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THE  TECHNOLOGY  OF 
BREAD-MAKING 


By  one  of  the  same  Authors, 

Inorganic  Chemistry,  Theoretical  and 

Practical.  With  49  Woodcuts  and  Questions  and 
Exercises.  Crown  8vo,  2s  6d,  London : Long- 
mans, Green  & Co 

An  Introduction  to  Practical  Inorganic 

Chemistry.  Fcap.  8vo,  Is.  6d.  London:  Long- 
mans, Green  & Co. 

Inorganic  Chemistry.  A Manual  for 

Students  in  Advanced  Classes.  With  Plate  of  Spectra 
and  78  Woodcuts.  Crown  8vo,  4s.  6d.  London  : 
Longmans,  Green  & Co, 

Introduction  to  the  Principles  of  Bread- 

Making.  ,^2s.  London  : Maclaren  & Sons,  37— 
38,  Shoe  Lane,  E.C. 

Cantor  Lectures  on  Modern  Develop- 
ments of  Bread-making.  Is.  London  : Society^ 
of  Arts,  John  Street,  Adelphi. 

Cantor  Lectures  on  Chemistry  of  Con- 
fectioners’ Materials  and  Processes.  Is.  Lon- 
don : Society  of  Arts,  John  Street,  Adelphi. 

Forensic  Chemistry  and  Chemical 

Evidence.  5s.  London  : Stevens  & Haynes, 
Bell  Yard,  Temple  Bar. 


THE  TECHNOLOGY  OF 
BREAD-MAKING 

INCLUDING 

The  Chemistry  and  Analytical  and  Practical  Testing 
of  Wheat,  Flour,  and  other  materials  employed 
in  Bread-making  and  Confectionery. 


By 

WILLIAM  JAGO,  F.I.C,  F.C.S., 

Of  Lincoln’s  Inn,  Barrister-at-Law  ; 

Senior  Examiner  in  Bread-making  and  Confectionery  to  the  City  and  Guilds 
of  London  Institute  for  the  Advancement  of  Technical  Education  ; 
Cantor  Lecturer  on  “ Modern  Developments  of  Bread-making,” 
and  “ Chemistry  of  Confectioners’  Materials  and  Pro- 
cesses ” to  the  Society  of  Arts,  London,  etc. 

And 

WILLIAM  C.  JAGO, 

Food  Manufacturing 
Chemist. 


AMERICAN  EDITION. 

BAKERS’  HELPER  COMPANY, 

CHICAGO,  'v 


Copyright] 


[All  Rights  Reserved. 


6 1 1 

REMOTE  SrOiwi 


L.  & A.  Harris, 
Printers, 

94,  Leadenhall  St.,  E.C. 


PREFACE. 


The  volume  now  offered  to  the  reader  must  be  regarded  as  a development 
of  the  vTiter’s  former  works  on  the  same  subject,  which  appeared  in  1886  and 
1895.  The  general  mode  of  treatment  is,  therefore,  to  some  extent  governed 
by  that  of  its  predecessors.  It  should  be  remembered  that  the  requirements 
of  the  student  of  the  technology  of  bread-making,  whether  miller  or  baker, 
have  been  the  first  consideration  ; and  accordingly  the  arrangement  is  that 
which  seems  most  likely  to  be  of  service  and  assistance  to  him.  In  addition 
the  authors  have  endeavoured  to  make  the  book  as  complete  a work  of  general 
reference  as  possible. 

In  the  preparation  of  the  present  treatise  the  wTiter  has  had  the  benefit  of 
the  assistance  of  his  son,  Mr.  William  C.  Jago,  whose  name,  together  with  his 
^ own,  appears  on  the  title-page.  Mx.  William  C.  Jago’s  wide  experience  of 
' the  practical  application  of  chemical  methods  in  the  mill  and  the  factory 
r have  been  of  much  advantage.  So  also  has  been  his  knowledge  of  the  dairy- 
ing industries  gained  in  Denmark,  and  of  modern  biology  and  bacteriology 
acquired  in  the  laboratories  of  Professor  Jorgensen  in  Copenhagen.  The 
writer  is  further  indebted  to  him  for  the  investigation  and  verification  of  many 
references  in  the  original  French,  German,  and  Danish. 

Since  1895  much  valuable  original  work  has  been  done  in  this  country, 
^ and  also  in  Europe  and  America,  on  bread-making  and  cognate  subjects. 
The  authors  have  tried  to  place  this  as  fully  as  possible  on  record.  In  so 
doing  they  have  adopted  the  method  of  giving  a resume  of  each  investiga- 
- tor’s  work  and  conclusions,  following  the  same  where  necessary  by  any 

j 

7 comments  of  their  own.  In  pursuance  of  this  plan,  new  chapters  have  been 
i wTitten  on  the  Strength  of  Flour,  the  Bleaching  of  Flour,  Wheat  Flour  and 
] Bread  Improvers,  the  Nutritive  Value  and  Digestibility  of  Bread,  and  the 
I Weighing  of  Bread.  Subjects  such  as  “ Standard  ” Bread,  and  the  use  of 

V 

199817 


PREFACE. 


additions  to  flour  and  bread  have  been  critically  and  exhaustively  examined. 
The  application  of  chemical  and  other  tests  to  routine  mill  practice  has  been 
dealt  with  in  a special  chapter.  Following  on  the  inclusion  of  Confectionery 
in  the  programme  of  the  City  and  Guilds  of  London  Institute  for  the  Advance- 
ment of  Technical  Education,  a chapter  has  been  added  on  the  Chemistry 
of  the  Confectioners’  Raw  Materials  and  Processes. 

Again,  the  authors  desire  to  express  their  thanks  to  the  number  of  millers, 
bakers,  and  scientists  who  by  personal  communications  and  in  many  other 
ways  have  rendered  them  so  much  assistance  in  the  preparation  of  this 
volume.  The  numerous  instances  of  help  of  this  kind  will  be  evident  on  a 
perusal  of  the  following  pages. 

In  a work  of  such  magnitude,  the  authors  cannot  hope  to  have  alto- 
gether avoided  mistakes,  and  in  such  cases  they  confldently  appeal  to  the 
generous  consideration  of  their  readers. 

WILLIAM  JAGO. 


London,  E.C., 

1,  Garden  Court,  Temple, 
July,  1911. 


CONTENTS 


CHAPTER 


PAGE 


I Introductory  .......... 

[I  Description  of  the  Principal  Chemical  Elements,  and  their  In- 
organic Compounds 

Ill  Description  op  Organic  Compounds  ...... 

[V  The  Microscope  and  Polarisation  op  Light  . . . . 

V Mineral  and  Fatty  Matters  ....... 

VI  The  Carbohydrates  ......... 

VII'  The  Proteins  .......... 

VIII  Enzymes  ane  Diastatio  Action  ....... 

IX  Fermentation  .......... 

X Bacterial  and  Putrefactive  Fermentations  . . . ■ 

XI  Technical  Researches  on  Fermentation  . . . . . 

XII  Manufacture  of  Yeasts 

XIII  Physical  Structure  and  Physiology  ^of  the  Wheat  Grain  . 

XTV  Chemical  Composition  of  Wheat  ...... 

XV  The  Strength  op  Flour  ........ 

XVI  Chemical  Composition  of  Flour  and  other  Milling  Products 
XVII  The  Bleaching  of  Flour  ........ 

XVni  Bread-making  .......... 

Special  Breads  and  Bread-making  Processes  .... 

vii 


1 

2S 

41 

57 

68 

74 

91 

120 

145 

182 

108 

232 

254 

270 

291 

344 

375 

400 

483 


XIX 


TIU 


CONTENTS. 


OHAPTKR  PAGE 

XX  Wheat,  Flour  and  Bread  Improvers  . . . . .497 

XXI  The  Nutritive  Value  and  Digestibility  of  Bread  . . . 625 

XXII  The  Weighing  of  Bread  . . . . . . , . 562 

XXIII  Bakehouse  Design  .........  681 

XXTV  The  Machine  Bakery  . . . . . . . .612 

XXV  Analytic  Apparatus  . . . . . . . . .680 

XXVI  Commercial  Testing  of  Wheats  and  Flours  ....  689 

XXVII  Determination  of  Mineral  and  Fatty  Matters  . . . 757 

XXVIII  Soluble  Extract,  Acidity  and  Proteins  . . . . .768 

XXIX  Estimation  of  Carbohydrates  . . . . . . . 800  - 

XXX  Bread  Analysis  . . . . . . . . .831 

XXXI  Adulterations  and  Additions  . . . . . . .837 

XXXII  Routine  Mill  Tests  . . . . . . . . .844 

XXXIII  Confectioners*  Raw  Materials  .......  852 

Index  ...........  894 


THE  TECHNOLOGY  OF 
BREAD-MAKING. 


CHAPTER  I. 

INTRODUCTORY. 

1.  General  Scope  of  Work. — ^The  object  of  the  present  Work  is  to  deal, 
in  the  first  place,  with  those  branches  of  knowledge  which  together  con- 
stitute the  scientific  foundations  of  Bread-making  as  a science  in  itself. 
Paramount  among  these  is — 

Chemistry. 

With  which  is  closely  associated — 

Heat  and  its  properties. 

Fermentation  and  the  Biology  of  Micro-organisms. 

Vegetable  Physiology  in  its  relation  to  the  Wheat  Plant. 

Microscopy. 

Next,  viewing  Bread-making  as  an  Art  or  Industry,  the  design  of  Bakeries 
and  adaptation  of  Machinery  for  various  purposes  is  discussed.  Following 
on  this  is  a description  of  the  various  processes  and  operations  involved 
in  the  Commercial  Manufacture  of  Bread,  together  with  an  investigation 
of  the  many  important  practical  problems  connected  therewith.  Chapters 
are  also  added  on  the  nutritive  value,  and  weighing,  of  bread,  and  other 
matters  of  interest. 

The  more  purely  analytical  section  of  the  work  includes  detailed 
diiections  foi  the  commercial  testing  and  valuation  of  flour,  yeast,  and 
other  bread-making  materials  ; in  addition  to  which  there  are  also  given 
approved  methods  for  the  commercial  and  complete  chemical  analysis 
of  such  substances.  A number  of  analyses  and  other  chemical  investi- 
gations have  been  recently  made  for  the  purposes  of  this  book,  and  are 
here  for  the  first  time  published.  The  work  concludes  with  a description 
of  the  chemistry  of  confectioners’  raw  materials. 

It  is  not  proposed  to  adhere  to  any  very  rigid  classification  but  so  to 
arrange  the  subject  matter  as  seems  most  likely  to  meet  the  requirements 
of  the  majority  of  readers. 

2.  Matter. — The  bodies  with  which  we  are  surrounded  present  an  almost 
endless  diversity  of  colour,  appearance,  and  other  characteristics.  One 
property  they  however  all  possess  in  common,  and  that  is  the  property  of 
weight.  All  bodies  are  attracted  by  the  earth,  and  any  substance  is  said 
to  be  heavy  because  of  the  resistance  which  it  offers  to  this  earth-attrac- 
tion or  gravitation.  Not  only  are  solid  bodies,  such  as  iron  and  wood, 
possessed  of  weight,  but  so  likewise  are  liquids,  such  as  water  and  oil,  and 
also  gases,  such  as,  for  example,  common  air,  or  coal-gas.  It  is  conveni- 
ent to  have  one  name  for  all  bodies  which  possess  weight,  and  for  this  pur- 
pose, in  English,  the  term  Matter  is  employed.  Matter,  then,  is  anything 

1 ' B 


2 


THE  TECHNOLOGY  OF  BREAH-MAKING. 


which  possesses  weight  (i.e.,  is  acted  on  by  gravitation),  and  exists  in  three 
distinct  forms,  namely,  as  solids,  liquids,  and  gases. 

3.  Force. — The  definition  of  matter  just  given  would  seem  at  first  sight 
sufficiently  comprehensive  to  embrace  everything  of  which  we  can  take 
cognisance,  but  yet  a moment’s  reflection  shows  the  existence  of  other 
things  beside  matter.  An  illustration  best  demonstrates  this  fact — A 
hammer-head  is  known  to  consist  of  matter  because  it  possesses  weight ; 
but  if  with  this  hammer-head  you  give  a series  of  blows  to  a small  piece 
of  nail -rod,  you  have  given  the  nail-rod  something  which  is  not  matter. 
The  hammer-head  is  not  lighter,  nor  is  the  nail-rod  heavier — still  the  blows 
are  something,  as  otherwise  they  could  produce  no  effect.  For  one  thing, 
the  nail-rod  will  have  been  flattened  and  altered  in  shape  ; further,  and 
which  is  of  far  more  present  importance,  it  will  have  become  hot  to  the 
touch.  Again,  to  make  use  of  another  illustration,  if  a dry  brick  be  care- 
fully weighed  and  then  made  red-hot  in  a furnace,  it  will  be  found  to  weigh 
when  hot  precisely  the  same  as  it  did  when  cold.  Further,  this  brick, 
if  allowed  to  become  cold,  imparts  heat  to  surrounding  objects,  and  never- 
theless remains  unaltered  in  weight.  Here,  then,  is  something  very  definite 
which  a body  can  receive  and  again  yield,  and  which  is  not  matter.  This 
something  has,  however,  a very  direct  relation  to  matter  ; in  the  first 
illustration  the  blows  were  struck  by  the  moving  hammer-head,  which 
consists  of  matter  in  motion.  The  more  rapid  the  motion,  the  more  violent 
would  be  the  blows  ; in  fact  the  force  of  the  blow  depends  both  on  the 
quantity  of  matter  and  the  rapidity  of  its  motion.  A number  of  con- 
siderations lead  to  the  belief  that  the  hot  iron  of  the  nail-rod  and  also  the 
hot  brick  differ  from  the  same  substances  in  the  cold  state,  in  that  their 
component  particles  are  in  a state  of  movement ; as  these  substances 
cool,  the  particles  once  more  enter  into  a condition  of  comparative  rest. 
This  something  beyond  matter  is  closely  associated  with  motion,  and  is 
termed  force.  Force  is  defined  as  that  which  is  capable  of  setting  matter 
in  motion,  or  of  altering  the  direction  or  velocity  of  matter  already  in  motion. 
The  motion  of  bodies  may  be  divided  into  two  classes  : there  is,  first,  that 
of  the  body  as  a whole,  as  in  the  case  of  the  moving  hammer-head ; second, 
the  internal  movements  of  the  particles  of  a body,  as  when  it  becomes  hot. 

Elements  of  Heat. 

4.  Heat,  its  Nature  and  Effects. — Among  generally  observed  facts  with 
regard  to  heat,  one  of  the  first  and  most  important  is  that  it  induces  the 
sensation  of  warmth.  According  to  the  character  and  degree  of  this  sensa- 
tion, a body  is  said  to  be  cold,  warm,  or  hot.  The  conditions  which  pro- 
duce this  sensation  of  warmth  also  cause  other  well-marked  changes  in 
the  physical  condition  of  substances.  The  general  effects  of  heat  are  to 
cause  bodies  as  they  get  hot  to  expand  in  volume  ; further,  solids  are  re- 
duced to  the  liquid  state  ; and,  with  still  further  increments  of  heat,  liquids 
are  converted  into  gases.  The  opposite  series  of  changes  occur  as  heat  is 
abstracted  from  bodies.  From  the  explanation  of  Force  given  in  the  pre- 
ceding paragraph,  it  will  be  understood  that  these  changes  are  not  accom- 
panied by  any  addition  or  diminution  of  weight.  On  the  contrary.  Heat 
is  viewed  as  a form  of  Force,  and  is  regarded  as  a mode  or  variety  of  internal 
motion  of  the  particles  of  bodies — the  hotter  they  are,  the  more  violent  and 
energetic  is  this  motion. 

5.  Measurement  of  Heat : Temperature. — The  earliest  and  most  accessible 
measure  to  be  applied  to  heat  is  that  of  the  sensation  of  warmth  before 
referred  to,  and  according  to  whether  a boiy  to  the  touch  is  hot  or  cold,  it 
is  said  to  be  of  high  or  low  temperature.  Temperature  is,  in  fact,  the  mea- 


INTRODUCTORY. 


3 


sure  of  what  is  popularly  termed  “how  hot  a body  is  ; ” it  will  be  seen  on 
consideration  that  this  depends  on  the  power  the  body  has  of  imparting 
heat  to  another  body.  Thus,  if  when  the  hand  is  thrust  into  water,  the 
water  is  able  to  yield  heat  to  the  hand, it  is  said  to  be  “hot,”  while  if  it 
robs  the  hand  of  heat  it  is  said  to  be  “ cold.”  The  measure  of  this  power 
is  termed  temperature,  and  is  more  exactly  embodied  in  the  following 
definition  : — The  temperature  of  a body  is  a measure  of  the  intensity  of  its 
heat,  and  is  further  defined  as  the  thermal  state  of  a body  considered  with  refer- 
ence to  its  power  of  communicating  heat  to  other  bodies. 

6.  The  Thermometer. — ^For  scientific,  and  also  for  most  technical,  purposes, 
the  sensations  are  not  sufficiently  accurate  methods  of  measuring  tem- 
perature ; accordingly  temperature  is  usually  measured  by  certain  of 
the  effects  which  heat  produces  : the  most  convenient  for  this  purpose 
is  the  expansion  of  liquids  with  an  elevation  of  temperature.  For  the 
general  purposes  of  temperature  measurement,  the  metal  mercury  is  the 
most  convenient  substance.  This  liquid,  enclosed  in  a suitable  vessel, 
constitutes  the  temperature-measuring  instrument  termed  a thermometer. 
In  constructing  a thermometer,  a bulb  is  blown  at  one  end  of  a glass  tube 
of  very  narrow  bore  ; the  bulb  and  tube  are  next  filled  with  carefully  purified 
mercury  ; this  is  boiled,  and  thus  all  air  and  moisture  are  driven  out  of 
the  tube  ; the  open  end  is  then  hermetically  sealed  by  fusing  the  glass 
itself.  At  this  stage  the  bulb  and  a portion  of  the  tube  are  filled  with 
mercury,  the  remainder  of  the  tube  being  a vacuum,  save  for  the  presence 
of  a minute  quantity  of  mercury  vapour.  On  heating  the  bulb  of  this 

- instrument,  the  mercury  expands  and  rises  considerably  in  the  stem. 
Throughout  any  body,  or  series  of  bodies  in  contact  with  each  other,  heat 
lias  a tendency  so  to  distribute  itself  that  the  whole  series  shall  be  at  the 
same  temperature  ; consequently  if  the  thermometer  be  placed  in  contact 
with  the  body  whose  temperature  it  is  desired  to  measure,  a redistribution 
of  heat  occurs,  until  the  two  are  at  the  same  temperature.  That  is  to 
say,  if  the  body  be  the  hotter,  it  yields  heat  to  the  thermometer  ; and  if  it  be 
colder,  it  receives  heat  from  the  thermometer,  until  the  temperature  of 
both  is  the  same.  The  two  being  in  efficient  contact,  this  stage  is  indi- 
cated by  the  mercury  becoming  stationary  in  the  thermometer.  Now 
the  volume  of  mercury  is  constant  for  any  one  temperature  ; therefore, 
to  register  temperature,  it  is  only  necessary  to  have  further  a scale,  or 
series  of  graduations,  attached  to  the  stem  of  the  instrument,  by  which 
the  temperature  may  always  be  read. 

7.  The  Pyrometer. — ^The  ordinary  mercury  thermometer  is  not  well 
adapted  to  the  measurement  of  comparatively  high  temperatures,  since 
the  mercury  boils  at  a temperature  considerably  below  that  of  a dull 
red  heat.  In  consequence  other  instruments  have  been  devised  for  that 
purpose,  to  which  the  name  of  pyrometers  has  been  given.  The  pyrometer 
may  therefore  be  regarded  as  a high  temperature  thermometer.  The 
pyrometers  used  for  measuring  the  temperature  of  some  types  of  bakers’ 
ovens,  consist  usually  of  a rod  and  casing  constructed  of  materials  which 
expand  at  different  rates  with  an  increase  of  temperature.  The  differential 
expansion  actuates  a needle  moving  in  front  of  a dial  plate. 

8.  Thermometric  Scales. — Subject  to  certain  precautions,  the  tempera- 
tures of  melting  ice  and  of  steam  in  contact  with  boiling  water  are  con- 
stant. The  height  at  which  the  mercury  stands  when  immersed  in  each 
of  these  is  marked  on  most  thermometers  ; for  the  registration  of  other 
temperatures  some  system  of  graduation  must  be  devised.  The  one  most 
commonly  employed  in  this  country  is  that  of  Fahrenheit,  while  for  scien- 


4 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


tific  purposes  that  of  Celsius,  or  the  Centigrade  Scale,  is  almost  universally 
adopted.  Fahrenheit  divided  the  distance  between  the  melting  and  boiling 
points  of  his  thermometer  into  180  degrees  ; degrees  of  the  same  value 
were  also  set  off  on  either  side  of  these  limits.  At  32  degiees  below  the 
melting  point  he  fixed  an  arbitrary  zero  of  temperature,  from  which  he 
reckoned.  On  his  thermometric  scale,  the  melting  point  is  32°,  while  the 
boiling  point  is  32  + 180  = 212°.  Degrees  below  the  zero  are  reckoned 
as  — (minus)  degrees,  thus  —8°  means  8 degrees  below  zero,  or  40  degrees 
below  the  melting  point  ; degrees  above  212  simply  reckon  upwards,  213, 
214°  F.,  etc. 

The  Centigrade  Scale  is  much  simpler,  the  melting  point  is  taken  as 
0°  or  zero,  and  the  boiling  point  as  100° ; temperatures  below  the  melting 
point  are  reckoned  as  — degrees. 

The  conversion  from  one  to  the  other  of  the  Centigrade  and  Fahren- 
heit Scales  may  be  easily  performed. 

180  Fahrenheit  degrees  = 100  Centigrade  degrees. 

0 — 5 

U 5 5 5 5 ^ 5 5 5 5 

1 ,,  degree  = ,,  degree. 

.">  5 5 5 5 ■ 1 5 5 5 5 

There  is  this  important  difference  between  the  two  scales — Centigrade 
degrees  count  from  the  melting  point,  while  Fahrenheit  degrees  are  reckoned 
from  32  below  the  melting  point. 

30°  C.  = 30  X 5 = 54  Fahrenheit  degrees. 

Therefore  30°  C.  are  equivalent  to  54  Fahrenheit  degrees  above  the  melting 
point,  but  as  the  melting  point  is  32,  that  number  must  be  added  on  to 
54  ; the  temperature  Fahrenheit  equal  to  30°  C.  is  86°.  By  the  reverse 
operation,  Fahrenheit  degrees  are  converted  into  degrees  Centigrade. 
The  following  formulae  represent  the  two  operations  : — 

C°.X  (P°.-32)x5^^o 

The  following  table  gives  the  equivalent  readings  on  the  two  thermometric 
scales  for  some  of  the  most  important  temperatures  — 


-40° 

C.  = 

-40° 

F. 

70°  C. 

— 

158° 

F. 

-17*7 

? 9 

0 

99 

75 

167 

, , 

0 

9 9 

32 

99 

80  ,, 

= 

176 

9 9 

15 

’ 9 

59 

9 9 

85  „ 

185 

9 9 

15-5 

9 9 

60 

90  „ 

194 

9 9 

20 

68 

9 9 1 

93-3  ,. 

zzn 

200 

2M 

-— 

70 

9 9 

95  ,, 

203 

9 9 

25 

77 

9 9 

100  „ 

— 

212 

9 9 

26-6 

9 9 

80 

9 9 

150  „ 

302 

9 9 

30 

86 

99 

1 200  „ 

392 

9 9 

35 

— 

95 

232*2 

= 

450 

9 9 

37-7 

9 9 

100 

9 9 

250  !! 

482 

9 9 

40 

9 5 

104 

260  „ 

= 

500 

9 9 

45 

9 9 

113 

9 9 

287*7  „ 

550 

9 9 

50 

9 9 

122 

300  „ 

— 

572 

9 9 

55 

131 

9 9 

316*6  ,, 

600 

9 ' 

60 

9 9 

140 

9 9 

! 350  „ 

662 

9 9 

65 

9 9 

149 

99 

1 400  „ 

752 

9 J 

9.  Quantity  of  Heat. — Temperature  is  not  a measure  of  quantity  of 
heat,  for  a thermometer  would  indicate  the  same  temperature  both  in  a 
vessel  containing  a pint,  and  one  containing  a gallon  of  boiling  w^ater,  al- 
though it  is  evident  that  one  must  contain  eight  times  as  much  heat  as 


INTRODUCTORY.  5 

the  other  ; further,  to  raise  the  gallon  of  water  to  the  boiling  point,  eight 
^mes  the  amount  of  heat  necessary  to  similarly  raise  the  pint  is  required. 
This  leads  to  the  mode  of  measuring  and  registering  quantity  of  heat.  Quan- 
tity of  heat  is  measured  by  the  amount  necessary  to  raise  a certain  weight 
of  some  body  from  one  to  another  fixed  temperature.  The  amount  of  heat 
necessary  to  raise  1 gram  of  water  from  0°  to  1°  C.  is  termed  a Unit  of  Heat. 
For  the  phrase  Unit  of  Heat,  a distinctive  term,  “ Calorie  ” is  now  fre- 
quently  employed  From  this  it  follows  that  to  raise  2 grams  of  water 
from  0 to  1 C.  will  require  2 Units  of  heat,  or  2 H.U.,  or  2 Calories.  Be- 
freezing  and  the  boiling  points,  ap'proximately  the  same  amount 

01  heat  IS  necessary  to  raise  1 gram  of  water  through  any  1 degree  of  tem- 
perature,  so  that  to  raise  1 gram  through  2 degrees  will  require  approximately 

2 H.U.  For  practically  all  purposes,  it  may  be  taken  that  the  weight  of 
water  in  grams  X degrees  of  temperature  through  which  it  must  be  raised 
— the  number  of  H.U.  required. 

10.  Specific  Heat.— The  quantity  of  heat  necessary  to  raise  the  same 
V eight  of  different  substances  through  1 degree  of  temperature  varies  very 

considerably.  The  quantity  of  heat  necessary  to  raise)  1 gram  of  any  sub- 
stance  through  1 degree  of  temperature  is  termed  its  SpeciBc  Heat.  Prom 
this  definition  it  follows  that  the  specific  heat  of  water  at  0°  C is  I'OO  or 
unity.  The  following  table  gives  the  specific  heat  of  various  substances’;— 

Substance. 

Water 
Alcohol 


Glass 
Iron  . . 
Copper 
Mercury 


Specific  Heat. 

1-00000 

0-61500 

0-19768 

0-11379 

0-09391 

0-03332 


If  equal  weights  of  water  at  different  temperatures  are  mixed  together 
the  result  is  a mixture  having  a temperature  the  mean  of  the  two  • thus 
a gallon  of  water  at  20°  C.  mixed  with  a gaUon  at  50°  C.  will  produce  a 
mixture  at  the  temperature  of  35°  C.  But  if  equal  weights  of  two  sub- 
stances of  different  specific  heats  be  thus  mixed,  the  temperature  of  the 
mixture  of  the  two  will  not  be  a mean  of  those  of  the  substances,  but  will 
be  nearer  that  of  the  substance  having  the  higher  specific  heat.  The  most 
important  mixture  with  which  the  baker  has  to  do  is  that  of  flour  with 
water,  as  the  temperature  of  the  resultant  dough  is  a matter  of  vital  con- 
cern to  him  The  results  are  complicated  by  the  presence  of  other  ingre- 
dients, as  salt  and  yeast,  and  also  in  practice  by  loss  of  heat  through  absorp- 
tion by  the  surroundings  of  the  dough,  and  heat  generated  by  chemical 
action  among  the  ingredients.  The  following  are  the  results  of  laboratory 
experiments  made  by  mixing  together  flour  and  water  only,  and  carefully 
taking  the  temperatures,  but  not  allowing  for  loss  of  heat  absorbed  bv 
containing  vessels.  ^ 


500  grams 

of  flour  at 

67°  F.  1 

Specific  Heat. 

500  „ 

water  at 

145°  F.  J 

[ = 1000  at  118°  P. 

0-53 

500 

flour  at 

67°  F.  ^ 

500  „ 

water  at 

104°  F.  ; 

t = 1000  at  93°  F. 

0-42 

500  „ 

flour  at 

67°  P.  1 

500  „ 

water  at 

86°  F.  J 

[ = 1000  at  80-5°  F. 

0-40 

I heats  are  calculated  from  the  above  experiments  in  the 

lollowmg  manner  : in  the  first  experiment  500  grams  of  water  have  fallen 
from  H5  to  118°,  that  is  27°,  during  which  they  must  have  afforded  500  x 
~ 13,500  H.U.  At  the  same  time  500  grams  of  flour  have  been  raised 


6 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


from  67°  to  118°,  that  is  through  51°,  which  is  equal  to  500  x 51  = 25,500 
grams  through  1°,  and  to  do  this  13,500  H.U.  have  been  utilised  ; then 
to  raise  1 gram  through  1°  there  has  been  taken 


13.500 

25.500 


= 0*53 


H.U. 


therefore  0*53  is  the  specific  heat  of  flour  as  derived  from  this  experiment. 

A number  of  observations  have  also  been  [made  on  the  temperatures 
of  mixtures  made  in  the  bakehouse  on  the  large  scale  for  manufacturing 
purposes.  The  doughs  were  machine-mixed,  and  no  allowance  is  made 
for  the  salt  and  compressed  yeast,  quantities  of  which  were  the  same  in 
all  cases.  The  quantities,  temperatures,  and  calculated  specific  heats 
are  given  in  the  following  table  : — 


Water. 

Flour. 

Dough. 

Flour. 

Specific 

Heat. 

0-39 

Quarts. 

53 

Lbs.  Temp. 

132-5  95° 

Lbs. 

205 

Temp. 

52-5° 

Temp. 

79-0° 

51 

127-5 

90° 

205 

50-0° 

77-0° 

0-30 

51 

127-5 

90° 

205 

50-0° 

77-0° 

0-30 

53 

132-5 

98° 

205 

53-0° 

79-0° 

0-45 

53 

132-5 

89° 

205 

53-0° 

76-0° 

0-36 

53 

132-5 

89° 

205 

53-0° 

76-0° 

0-36 

The  whole  of  these  figures,  it  must  be  remembered,  are  those  obtained 
in  experiments  made  under  conditions  such  as  hold  in  the  bakehouse, 
and  represent  rather  the  result  of  actual  working,  than  theoretic  specific 
heats  with  all  disturbing  causes  eliminated.  In  the  case  of  the  mixtures 
made  at  the  higher  temperatures,  there  is  naturally  a greater  loss  of  heat, 
and  this  causes  an  increase  in  the  corresponding  apparent  specific  heats. 
In  consequence  of  this,  the  No.  1 Laboratory  Experiment  gives  a remark- 
ably high  figure  ; but  the  whole  of  the  others  lie  fairly  closely  together. 
Comparing  those  above  given  with  a large  number  of  observations  on 
the  manufacturing  scale  since  made,  practically  all  the  specific  heat  results 
range  between  0‘36  and  0*45,  with  a mean  of  0‘40,  to  which  the  majority 
approach  most  closely.  Taking  0*40  as  the  working  s]3ecific  heat  of  flour, 
1 unit  by  weight  of  water  in  falling  through  1°  raises  2-5  units  by  weight 
of  flour  through  the  same  increment  of  temperature. 


11.  Sources  of  Heat. — ^Directly  or  indirectly  all  available  terrestrial 
heat  is  practically  derived  from  the  sun  : its  immediate  source,  however, 
for  manufacturing  operations  is  the  combustion  of  different  kinds  of  fuel ; 
these  give  out  different  amounts  of  heat  according  to  their  composition. 
Tlie  following  table  gives  the  number  of  heat  units  evolved  by  the  com- 
bustion of  one  gram  of  each  substance  in  oxygen  : — 


Heat  Developed  during  Combustion. 


Substance. 

Formula 

Heat  Units. 

Hydrogen 

H, 

34,462 

Carbon  . . 

C 

8,080 

Carbon  Monoxide 

CO 

2,634 

Marsh  Gas 

CH4 

13,063 

Olefiant  Gas 

C2H4 

11,942 

Alcohol  . . . . . . 

C2H5HO 

6,909 

Welsh  Chal 

about 

8,241 

Newcastle  Coal 

8,220  ' 

D(  rbysliire  Coal 

7,773 

Coke 

7,000 

Wood  (dried  in  air) 

. . 

3,547 

INTRODUCTORY. 


7 


12.  Expansion  by  Heat. — It  has  already  been  mentioned  that  in  most 
cases  bodies  expand  under  the  influence  of  heat.  Solids  expand  the  least, 
and  at  a definite  rate  for  each  particular  solid  ; liquids  have  a higher  rate 
of  expansion,  each  still  having  its  own  special  rate  ; while  gases  expand 
at  a far  higher  rate  than  either  liquids  or  solids.  The  following  table  gives 
what  are  termed  the 

Coefficients  of  Linear  Expansions  for  I°  between  0°  and  100°  0. 
Glass..  ..  0*000008613  Brass..  ..  0*000018782 

Platinum  ..  0*000008842  Lead..  ..  0*000028575 

Iron  ..  ..  0*000012204  Zinc  ..  ..  0*000029417 

Tliese  figures  mean  that  each  of  these  substances  expands  at  the  rate 
expressed  by  its  own  coefficient  : thus  1 foot  of  glass  at  0°  C.  becomes 
1*000008613  foot  long  at  1°  C.,  and  so  for  each  degree  rise  in  temperature. 
When  a body  is  heated,  its  whole  three  dimensions  of  course  increase, 
and  the  coefficients  of  cubical  expansion  of  solids  for  practical  purposes, 
may  be  taken  as  three  times  their  coefficients  of  linear  expansion. 

The  apparent  expansion  of  liquids  is  not  so  great  as  the  real,  because 
the  vessels  in  which  they  are  contained  also  expand.  The  following  table 
gives  the 

Total  Apparent  Expansions  of  Liquids  between  0°  and  100°  C. 
Mercury  . . . . 0*01543  Fixed  Oils  . . . . 0*08 

Distilled  Water  . . 0*0466  Alcohol  . . . . 0*116 

The  coefficient  of  apparent  expansion  for  1°  C.  is  obtained  by  dividing 
these  numbers  by  100,  thus  that  for  mercury  is  0*0001543.  Mercury  expands 
at  a practically  constant  rate  from  36°  to  100°  C.  ; water,  however,  contracts 
in  rising  from  0°  to  4°,  and  then  expands  from  4°  to  100°  C. 

13.  Expansion  and  Contraction  of  Gases. — There  are  certain  reasons 
V hich  lead  us  to  suppose  that  at  a temperature  of  — 273°  C.  bodies  would 
be  entirely  devoid  of  heat.  This  point  — 273°  C.  is  therefore  often  termed 
the  absolute  zero  of  temperature ; and  temperature  reckoned  therefrom 
is  termed  “ absolute  temperature.”  The  absolute  temperature  of  a body 
is  its  temperature  in  degrees  C.  + 273.  All  gases  expand  with  increase, 
and  contract  with  diminution,  of  temperature.  The  amount  of  expansion 
and  contraction  is  the  same  for  all  gases  between  the  same  limits  of  tem- 
perature, provided  the  temperature  is  considerably  higher  than  that  at 
which  they  condense  to  liquids.  The  volume  of  all  gases  is  directly  pro- 
portional to  their  absolute  temperature.  Because  of  this  variation  with 
temperature  it  is  necessary  to  fix  a temperature  which  shall  be  considered 
as  a standard  in  expressing  the  volume  of  gas  : 0°  C.  is  commonly  adopted  for 
this  purpose. 

Knowing  the  volume  of  a gas  at  any  one  temperature,  its  volume  at  any 
other  may  be  easily  calculated  ; thus,  a vessel  was  found  to  contain  750 
c.c.  of  air  at  15°  C.  ; it  is  required  to  find  its  volume  at  the  standard  tem- 
perature. 

15°  C.  -f  273  = 288°  Absolute  Temperature. 

0°  C.  + 273  = 273° 

As  288  : 273  : : 750  ; 711  c.c.  of  gas  at  standard  temperature. 

14.  Relation  of  Pressure  and  Volume  of  Gases. — It  is  convenient  here 
to  note  that  the  volume  of  a gas  is  also  affected  by  the  pressure  to  which 
it  is  subjected  : this  variation  is  governed  by  what  is  called  Boyle  and 
Marriotte’s  Law — ^The  volume  of  any  gas  is  inversely  proportional  to  the 


8 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


pressure  to  which  it  is  subjected.  The  most  important  variations  of  pressure 
to  which  gases  are  liable  are  those  resulting  from  the  changes  in  pressure 
of  the  atmosphere.  The  height  of  the  mercury  column  of  the  barometer 
is  a direct  measure  of  the  pressure  of  the  atmosphere,  therefore  that  pres- 
sure is  commonly  expressed  in  the  number  of  millimetres  (m.m.)  which  that 
column  is  high.  For  purposes  of  comparison  it  is  also  necessary  to  reduce  all 
pressures  to  one  standard  ; that  selected  is  an  atmospheric  pressure  which 
causes  the  barometer  to  stand  at  760  millimetres. 

The  temperature  and  pressure  quoted  as  standards  for  gas  measure- 
ment 0°  C.  and  760  m.m.  are  often  termed  normal  temperature  and  pres- 
sure ; for  this  expression  the  abbreviation,  “ N.  T.  P.”  is  frequently 
used. 

The  laws  governing  the  relation  between  the  volume  and  temperature 
and  pressure  of  gases  must  not  be  regarded  as  absolutely  exact,  since  they 
are  subject  to  certain  small  but  well-marked  departures.  These  variations, 
however,  have  no  direct  bearing  on  the  present  subject. 

15.  Transmission  of  Heat. — ^It  is  well  known  that  when  one  part  of  a 
body  or  place  is  heated,  the  other  parts  also  become  hot  more  or  less  quickly. 
Some  explanation  of  how  such  transmission  is  effected  must  now  be  given. 

There  are  three  methods  by  which  heat  can  be  transmitted  from  one  point  to 
another,  which  are  termed  respectively  Convection,  Conduction,  and  Radiation. 

16.  Convection. — ^As  the  word  convection  implies,  a part  or  mass  is 
heated  by  the  heated  matter  being  conveyed  from  one  part  to  another. 
This  kind  of  heating  can  only  occur  in  liquids  or  gases  where  the  particles 
of  matter  can  move  freely.  One  of  the  best  illustrations  of  convection  is 
the  heating  of  an  ordinary  vessel  of  water  by  the  placing  of  a fire  under- 
neath ; the  layer  of  water  at  the  bottom  first  gets  hot,  and  consequently 
expands  and  becomes  of  lower  specific  gravity.  As  a result  of  being  lighter, 
it  therefore  rises  to  the  surface,  and  its  place  is  taken  by  other  water  which 
is  colder  and  denser.  This  in  its  turn  is  heated  and  rises  ; continuous  cur- 
rents of  warm  water  ascend  through  the  liquid,  and  colder  water  descends 
to  take  its  place.  In  this  way  the  whole  mass  is  gradually  made  hot.  The 
heating  of  the  water  in  a supply  cistern  on  the  top  of  a building  by  currents 
through  flow  and  return  pipes  from  a small  boiler  in  the  basement  is  due 
to  convection.  So,  too,  the  ventilation  of  a building  is  naturally  caused 
in  the  same  way — heated  air  ascends  and  makes  its  way  through  exits  at 
the  highest  point,  while  cold  air  enters  through  the  joints  of  doors  and 
windows  or  apertures  specially  provided  for  the  purpose.  Among  other 
illustrations  may  be  mentioned  the  warming  of  a building  or  room  by  hot- 
water  pipes  running  close  to  the  floor.  The  air  is  thereby  heated  and 
ascends  ; the  cooler  air  falls  and  takes  its  place.  Conversely,  a mass  of 
water  or  air  is  best  cooled  by  the  application  of  cold  at  the  upper  surface. 
Thus,  given  a vessel  of  hot  water  and  a coil  of  pipes  at  the  surface,  through 
which  cold  water  is  passing,  the  cold  water  lowers  the  temperature  of  the 
upper  layer  in  the  vessel ; this  consequently  descends  and  its  place  is  taken 
by  hotter  water.  In  this  way  a series  of  currents  is  set  up  whereby  the  whole 
mass  of  water  is  uniformly  cooled.  It  will  be  seen  that  convection  is  a 
mode  of  distributing  heat  through  a mass  of  either  liquid  or  gas  by  means  of 
moving  currents,  such  currents  being  usually  produced  by  differences  in  density 
due  to  expansion  caused  by  the  source  of  heat  itself. 

17.  Conduction. — ^Instances  are  well  known  in  which  the  application 
of  heat  to  any  one  point  of  a solid  causes  the  whole  mass  to  become  hot. 
Thus,  if  the  end  of  a bar  of  iron  be  placed  in  the  fire,  the  other  end  gradu- 


INTRODUCTORY. 


1) 


ally  increases  in  temperature.  This  cannot  be  due  to  convection,  but  is 
due  to  the  heating  effect  which  the  hot  particles  of  the  body  have  on  the 
contiguous  particles.  In  these  cases  the  heat  is  said  to  be  transmitted  by 
conduction.  Conduction  is  that  method  of  transmitting  heat  in  which  the 
heat  passes  from  the  hotter  particles  of  a body  to  the  colder  ones  lying  in  contact 
with  them,  and  so  throughout  the  whole  body. 

There  are  wide  differences  in  the  power  of  conducting  heat  displayed  by 
various  substances  ; thus,  if  a bar  of  copper  be  heated  in  the  same  way  as 
suggested  for  the  iron,  the  further  end  becomes  hot  far  more  rapidly.  If, 
instead,  a rod  of  glass  or  porcelain  be  heated,  the  outer  end  gets  hot  only 
with  extreme  slowness.  It  must  therefore  be  remembered  that  some  sub- 
stances conduct  heat  much  more  rapidly  than  others.  The  metals  as  a class 
are  good  conductors,  although  there  are  great  differences  between  them. 
Porcelain,  tiles,  glass,  and  earthy  substances  are  generally  bad  conduc- 
tors, so  also  are  most  bodies  of  animal  or  vegetable  origin,  as,  for  example, 
felt,  wool,  and  wood.  Water  is  a bad  conductor,  and  so  are  the  gases.  Air 
is^^one  of  the  worst  heat  conductors  known,  consequently  porous  masses, 
as  slag-wool  and  fossil  earth,  conduct  very  badly,  not  only  from  their  own 
non-conducting  power,  but  because  of  the  air  retained  in  their  interstices. 
Owing  to  their  very  slight  conducting  properties,  wool,  glass,  bricks,  and 
similar  bodies  are  frequently  termed  non-conductors.  The  following  table 
gives  the  comparative  conducting  power  of  a few  substances,  silver  being 
taken  as  100. 


Comparative  Powers  of  Conductivity. 

Silver 

Copper 

Iron 

Lead 

Marble  . . . . . . . . . . . . about 

Porcelain  . . . . . . . . . . . . „ 

Brick  Earth  . . . . . . . . . . „ 


100 

75 

10 

8 

2 

1 

1 


18.  Radiation. — It  has  been  already  explained  that  when  a substance  is 
hot,  its  particles  are  in  a state  of  motion  : under  circumstances  in  which 
transmission  of  heat  by  convection  and  conduction  is  impossible,  one  body 
may  yet  be  heated  by  another.  The  explanation  now  generally  accepted 
is,  that  all  space  is  permeated  by  a highly  elastic  body  to  which  the  name 
of  ether  has  been  given,  which  is  capable  of  being  set  in  undulatory  motion 
by  appropriate  agitation.  The  violently  moving  particles  of  a hot  body 
in  the  act  of  vibration  strike  against  this  ether,  setting  up  in  it  a series 
of  waves.  These  waves  spread  in  all  directions,  and  on  impingeing  against 
a cold  body,  cause  its  particles  also  to  assume  a state  of  vibration — ^that 
is,  they  make  the  substance  hot.  In  this  way  heat  passes  from  one  body 
to  the  other,  not,  however,  as  hot  matter,  but  as  a peculiar  wave-like  motion 
in  the  substance  called  ether.  This  is  known  as  “ Radiation  ” of  Heat,  and  is 
independent  of  the  temperature  of  the  medium  through  which  radiation  occurs. 

Radiation  occurs  in  straight  lines  in  all  directions  from  the  body  which 
is  evolving  heat,  and  follows  the  same  general  laws  of  reflection  as  those 
which  govern  light.  At  the  same  temperature  different  bodies  radiate 
heat  at  different  rates.  The  rate  of  radiation  is  affected  both  by  the  nature 
of  the  radiating  material  and  also  the  eondition  of  its  surface,  whether 
rough  or  smooth.  Highly  polished  surfaces  radiate  less  rapidly  than 
those  which  are  roughened.  Being  maintained  at  the  same  temperature, 
the  following  table  gives  the  comparative  radiating  power  of  different 
bodies. 


10 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


Comparative  Power  of  Radiation. 


Lampblack  (Soot)  . . . . . . . , . . 100 

White  Lead  . . . . . . . . . . . . 100 

Tarnished  Lead  . . . . . . . . . . . . 45 

Polished  Iron  . . . . . . . . . . . . 15 

Burnished  Silver  . . . . . . . . . . . . 2*5 


When  hot,  surfaces  of  clay  and  brick  are  good  radiators  of  heat,  so  also 
are  those  of  flannel  and  other  like  substances. 

In  order  that  bodies  may  be  heated  by  radiant  heat,  it  is  necessary 
that  they  possess  the  power  of  absorbing  such  heat — like  radiation,  this 
power  of  absorption  also  varies  with  different  bodies.  Those  which  are 
good  radiators  of  heat  are  good  absorbents,  and  practically  the  table  showing 
power  of  radiation  equally  applies  to  power  of  absorption. 

A good  illustration  of  the  different  modes  of  transmission  of  heat  is 
furnished  by  the  action  of  one  of  the  pipes  of  a steam  oven.  This  pipe 
contains  a certain  quantity  of  water  sealed  up  in  the  pipe.  The  pipe  is 
built  into  the  oven  on  a slight  incline  so  that  the  lower  end  is  in  the  fur- 
nace, and  the  upper  one  in  the  baking  chamber  of  the  oven.  The  fire 
of  the  furnace  or  the  heated  gases  thereby  produced  are  in  contact  witli 
the  pipe.  By  conduction  the  heat  finds  its  way  through  the  iron  walls 
of  the  pipe  and  into  the  water.  This  is  heated  by  convection  currents, 
and  ultimately  the  steam  finds  its  way  into  the  upper  parts  of  the  pipe 
which  are  in  the  oven.  The  metal  is  consequently  heated  by  conduction 
and  by  conduction  the  heat  passes  through  to  the  outer  surface.  There 
it  partly  warms  the  air  by  a process  of  conduction  and  also  sets  up  radiation 
by  which  anything  placed  in  the  oven  to  bake  is  in  due  course  heated. 

19.  Mechanical  Equivalent  of  Heat. — It  has  already  been  stated  that 
heat  is  produced  when  mechanical  work  is  absorbed  by  friction  or  per- 
cussion, as  when  nail-rod  is  heated  by  repeated  blows  of  the  hammer.  Care- 
ful measurements  have  shown  that  the  work  done  by  1 lb.  falling  through 
772  feet  (or  772  ft.-lbs.),  is  capable  of  raising  the  temperature  of  1 lb.  of  water 
1°  F.  : this  amount  is  therefore  termed  the  Mechanical  Equivalent  of  Heat. 
From  this  the  value  in  degrees  Centigrade  is  easily  calculated,  being  of 
772=1390  ft.-lbs,  of  work  to  raise  I lb.  of  water  through  1°  Centigrade. 

Introductory  Chemical  Principles. 

20.  Definition  of  Chemistry. — Chemistry  has  well  been  defined  as  that 
science  which  treats  of  the  composition  of  matter,  of  changes  produced 
therein  by  certain  natural  forces,  and  of  the  action  and  reaction  of  different 
kinds  of  matter  on  each  other.  It  follows  that  the  Chemistry  of  Wheat, 
Flour,  and  Bread  may  be  defined  as  that  branch  of  the  science  which  treats  of 
the  composition  of  these  bodies,  of  the  changes  they  undergo  when  subjected 
to  the  action  of  certain  natural  forces,  and  of  the  action  and  reaction  of  these 
and  other  kinds  of  matter  on  each  other. 

21.  Introductory  Study  Necessary. — An  elementary  course  of  study 
of  the  general  principles  of  chemistry  must  precede  that  of  any  particular 
branch  of  the  applied  science.  Such  a course  should  include  the  preparation 
and  properties  of  the  commoner  elements  and  their  compounds,  the  prin- 
ciples of  qualitative  analysis,  and  the  simpler  laws  governing  chemical 
action  arid  combination.  For  this  purpose  Jago’s  “ Elementary  Chem- 
istry.” and  “Advanced  Chemistry,”  published  by  Messrs.  Longmans  & Co., 
may  be  employed.  For  convenience  of  reference  and  in  response  to  a 
widely  expressed  wish,  a short  description  follows  of  the  most  important 
chemical  laws,  and  also  of  such  elements  and  compounds  as  are  closely 


INTRODUCTORY. 


11 


connected  with  the  chemistry  of  wheat,  flour,  and  bread.  This  brief  account 
must  not,  however,  be  accepted  as  a substitute  for  a systematic  course 
of  study  of  elementary  chemistr}^ 

22.  Indestructibility  of  Matter. — Chemical  changes  are  often  accom- 
j)anied  by  very  great  alterations  in  the  appearance  and  properties  of  the 
bodies  involved  ; for  example,  when  a candle  is  burned  it  almost  entirely 
disappears,  but  although  it  no  longer  remains  in  the  solid  state,  all  its 
constituents  exist  as  gases,  and  these  weigh  exactly  the  same  as  did  the 
candle,  flus  the  oxygen  of  the  air  with  which  they  have  combined.  Matter 
is  indestructible,  and,  consequently,  the  same  weight  of  material  remains  after 
any  and  every  chemical  change  as  there  was  before  its  commencement. 

23.  Preliminary  Definitions. — It  is  important  that  at  the  outset  accurate 
and  concise  ideas  are  gained  of  the  meaning  of  various  chemical  terms. 
Although  matter  assumes  so  many  diversified  forms,  yet  all  bodies,  on 
being  subjected  to  chemical  analysis,  are  found  to  consist  of  one  or  more 
of  a class  of  about  eighty  substances,  which  are  termed  “ elements.” 

An  Element  is  a substance  which  has  never  been  separated  into  two  or  more 
dissimilar  substances. 

Recent  chemical  researches  go  to  show  that  some  of  the  bodies  now 
regarded  as  elements,  may  after  all  be  composed  of  more  than  one  substance. 
However  interesting  such  investigations  may  be,  they  are  not  likely  to 
have  any  bearing  whatever  on  our  present  subject. 

While  the  letters  of  the  alphabet  are  few,  the  number  of  words  which 
can  be  formed  from  them  is  practically  infinite  ; so,  in  a somewhat  similar 
fashion,  from  the  comparatively  small  number  of  elements  which  constitute 
the  “ alphabet  ” of  chemistry,  there  may  be  built  up  an  immense  number 
of  chemical  compounds. 

A compound  is  a body  produced  by  the  union  of  two  or  more  elements 
in  definite  proportions,  and,  consequently,  is  a substance  which  can  be  separated 
into  two  or  more  dissimilar  bodies.  Compounds  differ  in  appearance  and 
characteristics  from  their  constituent  elements. 

The  term  “ Mixture  ” is  applied  to  a substance  produced  by  the  mere 
blending  of  two  or  more  bodies,  elements  or  compounds,  in  any  proportion, 
without  union.  Each  component  of  a mixture  still  retains  its  own  properties, 
and  separation  may  be  effected  by  mechanical  means. 

24.  List  of  Elements. — The  following  is  a list  of  some  of  the  more  impor- 
tant elements,  together  with  their  symbols  and  other  particulars  : — 


Name. 

Symbol. 

Combining  or 
Atomic  Weight. 

Atomicity  or 
Quantivalence, 

Aluminium  . . 

. . A1 

Old. 

27 

New. 

26-9 

IV 

Barium 

Ba 

137 

1364 

II 

Boeon 

. . B 

II 

10-9 

III 

Beomine 

. . Br 

80 

79-36 

I 

Calcium 

. . Ca 

40 

39-8 

II 

Caebon 

. . C 

12 

11-91 

IV 

Chloeine  . . 

. . Cl 

35*5 

35-18 

I 

Chromium  . . 

. . Cr 

52 

51-7 

VI 

Copper  (Cuprum)  . . 

. . Cu 

63 

63-1 

II 

Fluoeine  . . 

..  F 

19 

18-9 

I 

Hydeogen  . . 

..  H 

I 

1-0 

I 

Iodine 

..  I 

126 

125-9 

I 

Iron  (Ferrum) 

. . Fe 

56 

55*6 

VI 

Lead  (Plumbum)  . . 

. . Pb 

205 

205-35 

IV 

Magnesium  . . 

..  Mg 

24 

24-18 

II 

12 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Name. 

Symbol. 

Combining  or 

Atomicity  or 

Atomic  Weight. 

Old.  New. 

Quantivalence. 

Manganese  . . 

. . Mn 

55 

54-6 

VI 

Mercury  (Hydrargyrum) 

..  Hg 

199 

198-5 

II 

Nitrogen  . . 

..  N 

14 

13-93 

V 

Oxygen 

..  0 

16 

15-88 

II 

Phosphorus 

. . P 

31 

30-77 

V 

Platinum 

..  Pt 

193 

193-3 

IV 

Potassium  . . 

..  K 

39 

38-86 

I 

Silicon 

..  Si 

28 

28-2 

IV 

Silver  (Argentum)  . . 

..  Ag 

107 

107-12 

I 

Sodium  (Natrium) . . 

..  Na 

23 

22-88 

I 

Sulphur 

..  S 

32 

31-83 

VI 

Tin  (Stannum) 

. . Sn 

118 

118-1 

IV 

Zinc  . . 

. . Zn 

65 

64-9 

II 

25.  Recently  Discovered  Elements. — Considerable  interest  attaches  to 
certain  elements  which  have  recently  been  discovered.  Among  these 
are  argon  and  other  allied  elements  which  exist  in  the  atmosphere,  and 
radium,  a constituent  of  pitch-blende.  As  none  of  these  bodies  has  appa- 
rently a bearing  on  the  chemistry  of  bread -making  they  are  not  dealt  with 
in  this  work. 

26.  Metals  and  Metalloids. — ^The  elements  are  divided  into  two  groups, 
termed  respectively  “ Metals,”  and  “ Metalloids  ” or  non-metals.  The 
non-metals  are  distinguished  in  the  foregoing  table  by  being  printed  in 
small  capitals.  The  line  of  division  between  the  two  classes  is  not  very 
marked,  the  one  group  gradually  merging  into  the  other.  The  metals, 
as  a class,  are  opaque  bodies,  having  a peculiar  lustre  known  as  metallic  ; 
they  are  usually  good  conductors  of  heat  and  electricity.  Two  of  the 
elements,  mercury  and  bromine,  are  liquid  at  ordinary  temperatures, 
while  hydrogen,  oxygen,  nitrogen,  and  chlorine  are  gaseous. 

27.  Symbols  and  Formulae. — ^The  symbols  are  abbreviations  of  the 
names  of  the  elements,  and,  where  practicable,  consist  of  the  first  letter 
of  the'Latin  names.  When  two  or  more  elements  have  names  commencing 
with  the  same  letter,  it  becomes  necessary  to  distinguish  them  from  each 
other  by  restricting  the  initial  letter  to  the  most  important  element,  and 
selecting  two  letters  as  the  symbol  of  each  of  the  others.  Thus,  carbon 
and  chlorine  each  commence  with  “ C,”  that  letter  is  chosen  as  the  symbol 
of  carbon,  while  that  of  chlorine  is  Cl. 

As  all  compound  bodies  consist  of  elements  united  together,  they  may 
be  conveniently  expressed  symbolically  by  placing  side  by  side  the  symbols 
of  the  constituent  elements  ; the  symbol  of  a compound  is  termed  its  for- 
mula. Thus,  common  salt  consists  of  chlorine  and  sodium  ; its  formula 
is  accordingly  written,  NaCl. 

28.  Further  Uses  of  Symbols  and  Formulae  : law  of  chemical  com- 
bination by  weight. — Simply  as  abbreviations  of  the  full  names,  symbols 
and  formulae  are  of  great  service  ; this,  however,  is  but  a small  part  of 
their  significance  and  value  to  the  chemist.  Their  further  use  may  best 
be  explained  by  reference  to  certain  information  gained  by  experiment, 
to  which  careful  attention  is  requested.  On  analysis,  it  is  found  that 
36’5  ounces  of  the  substance  known  as  hydrochloric  acid  consist  of  1 ounce 
of  hydrogen,  combined  with  35'5  ounces  of  chlorine  ; also,  that  in  58'5 
ounces  of  common  salt  there  are  35*5  ounces  of  chlorine  to  23  of  sodium. 
Taking  water  as  another  instance  of  a hydrogen  compound,  analysis  show^s 
that  its  composition  may  be  expressed  by  the  statement,  that  18  ounces 


INTRODUCTORY. 


la 

of  water  consist  of  2 ounces  of  hydrogen  combined  with  16  ounces  of  oxygen. 
In  the  table  given  on  page  II  there  is  a column  headed  “Combining  or 
Atomic  Weight ; ” on  referring  to  this  it  will  be  found  that  the  numbers 
opposite  hydrogen,  chlorine,  sodium,  and  oxygen,  are,  respectively,  1,35*5, 
23,  and  16,  being  (with  one  exception)  identical  with  those  that  have  just 
been  given  as  the  numbers  obtained  by  analysis  of  the  compounds  under 
consideration.  It  is  possible  to  assign  to  every  element  a number,  which 
number,  or  its  multiple,  shall  represent  the  proportionate  quantity  by  weight 
of  that  element  which  enters  into  any  chemical  compound.  These  numbers 
are  termed  the  “ Combining  or  Atomic  Weights  ” of  the  elements,  and  are 
deduced  from  results  obtained  on  actual  analysis.  In  addition  to  its  use 
as  an  abbreviated  title  of  any  element,  the  symbol  represents  the  quantity 
of  the  element  indicated  by  its  combining  weight ; where  multiples  of  that 
quantity  exist  in  a compound,  the  fact  is  expressed  by  placing  a small 
figure  after  the  symbol  and  slightly  below  the  line.  In  the  table  of  elements 
there  are  two  columns  of  combining  weights  given,  headed  respectively 
“ Old  ” and  “ New  ” ; the  second  column  gives  those  obtained  as  a result 
of  the  most  recent  research  and  which  represent  the  most  exact  determinations 
as  yet  made.  For  most  purposes,  the  weights  given  in  the  first  column  are 
sufficiently  accurate. 

As  previously  stated,  the  formula  of  sodium  chloride  is  NaCl,  and  it 
contains  23  of  sodium  to  35  5 of  chlorine.  The  formula  of  hydrochloric 
acid  is  HCl,  and  it  contains  1 of  hydrogen  to  35*5  parts  of  chlorine.  Water 
consists  of  2 parts  of  hydrogen  to  16  of  oxygen  ; the  fact  that  it  contains 
twice  the  combining  weight  of  hydrogen  is  expressed  by  writing  the  formula, 
H2O.  Again,  ammonia  contains  3 parts  by  weight  of  hydrogen  to  14 
parts  of  nitrogen,  consequently  it  has  the  formula,  NHg  : the  substance 
commonly  termed  carbonic  acid  gas  consists  of  32  parts,  or  twice  the  com- 
bining weight,  of  oxygen  to  12  by  weight  of  carbon,  the  formula  is  con- 
sequently COg.  The  quantity  of  an  element  represented  by  its  combining 
weight  is  termed  “ one  combining  proportion  ” of  that  element. 

29.  Constitutional  Formulae. — In  addition  to  simply  showing  the  number 
of  atoms  of  each  element  present,  formulae  are  frequently  so  written  as 
to  show  the  probable  constitution  of  the  resultant  compounds  ; such  formulae 
are  termed  “ Constitutional  Formulae.” 

30.  Chemical  Equations. — Chemical  changes  are  most  conveniently 
expressed  by  what  are  termed  “ chemical  equations  ” : these  consist  of 
the  S3mibols  and  formulae  of  the  bodies  participating,  placed  before  the 
sign  =,  while  those  of  the  resultant  bodies  follow.  As  an  instance  it  may 
be  mentioned  that,  when  a solution  of  potassium  iodide  is  added  to  one 
of  mercury  chloride,  potassium  chloride  and  mercury  iodide  are  produced. 
The  equation  representing  this  chemical  action  is  written  thus  : — 

2KI  -f  HgCla  = 2KC1  -f  Hgl2. 

Potassium  Iodide.  Mercury  Chloride.  Potassium  Chloride.  Mercury  Iodide. 

Having  access  to  a table  of  combining  weights,  the  chemist  learns  from 
this  equation  that  two  parts  of  potassium  iodide,  each  containing  one 
combining  proportion  of  potassium  weighing  39,  and  one  of  iodine  w^eighing 
126  together  with  one  part  of  mercury  chloride,  containing  one  combining 
proportion  of  mercury  weighing  199,  and  two  of  chlorine  each  weighing 
35*5,  together  yield  or  produce  two  parts  of  potassium  chloride,  each 
consisting  of  one  combining  proportion  of  potassium  w^eighing  39,  and 
one  of  chlorine  w^eighing  35*5,  and  one  part  of  mercury  iodide,  containing 
one  combining  proportion  of  mercury  w^eighing  199,  and  tw^o  combining 
proportions  of  iodine  each  weighing  126.  As  no  chemical  change  affects 


14 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  weight  of  matter,  the  weight  of  the  quantity  of  a compound,  represented 
by  its  formula,  must  be  the  sum  of  that  of  the  constituent  elements  : so, 
too,  the  weight  of  the  bodies  resulting  from  a chemical  change  must  be 
the  same  as  that  of  the  bodies  before  the  change,  whatever  it  may  be,  had 
occurred.  Although  from  a chemical  equation  and  table  of  combining 
weights,  it  is  possible  to  state  what  relative  weight  of  each  element  is  con- 
cerned in  any  chemical  action,  it  must  never  be  ^forgotten  that  the  com- 
bining weights  were  first  determined  by  experiment  and  then  the  table  com- 
piled therefrom.  The  statement  of  premise  and  deduction  is,  that  hydrogen 
and  chlorine  have  respectively  the  combining  weights  of  1 and  35*5  assigned 
to  them,  because  analysis  shows  that  they  combine  in  those  proportions  ; 
not  that  hydrogen  and  chlorine  have  as  combining  weights  1 and  35*5, 
and  therefore  they  must  combine  in  those  proportions.  The  combining 
weights  are  simply  a tabular  expression  of  results  obtained  by  practical 
analytic  investigation. 

31.  Atoms  and  Molecules. — The  fact  that  the  quantity  of  every  element 
which  enters  into  combination  is  either  a certain  definite  and  unchangeable 
weight,  or  a multiple  of  that  weight,  led  chemists  to  regard  this  weight 
of  a combining  proportion  of  an  element  as  being  in  some  way  associated 
with  its  physical  nature.  The  first  step  toward  the  explanation  of  this 
question  is  due  to  Dalton,  who  enunciated  what  is  termed  the  Atomic 
Theory.  He  assumed  that  all  matter  is  built  up  of  extremely  small  particles, 
which  are  indivisible,  and  that  when  elements  combine,  it  is  between 
" these  particles  that  the  act  of  union  occurs.  These  ultimate  particles  of 
matter  are  termed  “Atoms.”  The  name  “atom”  is  derived  from  the 
Greek,  and  signifies  that  which  is  indivisible.  Atoms  of  the  same  element 
are  supposed  to  be  of  the  same  size  and  weight.  With  the  absolute  weight 
of  atoms  the  student  of  bread-making  chemistry  has  but  little  to  do  : the  prin- 
cipal point  of  importance  for  him  is  their  relative  weights  compared  with  each 
other.  For  chemical  purposes,  an  atom  may  be  defined  as  the  smallest  particle 
of  an  element  which  enters  into,  or  is  expelled  from,  a chemical  compound. 
For  the  phrase,  “ combining  proportion,”  hitherto  used,  the  term  “ Atom  ” 
may  be  substituted  ; the  combining  weight  then  becomes  the  relative  weight 
of  the  atom  of  each  element  compared  with  that  of  hydrogen,  which,  being 
the  lightest,  is  taken  as  unity.  Though  the  atomic  theory  does  not  admit 
of  absolute  proof,  yet  it  so  amply  and  consistently  explains  all  the  phenomena 
of  chemistry  that  its  essential  principles  are  universally  recognised. 

The  little  group  of  atoms  represented  by  the  formula  of  a compound 
is  termed  a “ molecule.”  A molecule  is  the  smallest  possible  particle  of 
a substance  which  can  exist  alone.  In  the  case  of  chemical  compounds 
the  molecule  cannot  be  further  subdivided,  except  by  separation  into  the 
atoms  of  its  constituent  elements,  or  into  two  or  more  molecules  of  some 
simpler  chemical  compound  or  compounds.  When  elements  are  in  the 
free  or  uncombined  state,  their  atoms  usually  combine  together  to  form 
elementary  molecules  : thus  with  oxygen,  two  atoms  unite  to  form  a mole- 
cule of  oxygen  ; the  formula  of  the  oxygen  molecule  is  written,  O2. 

Tlie  molecules  of  the  following  elements  contain  two  atoms  : — hydro- 
gen, chlorine,  oxygen  and  nitrogen. 

As  all  elements  normally  exist  in  the  molecular  state,  it  is  frequently 
advisable  to  use  equations  in  which  the  lowest  quantity  of  any  element 
])resent  is  a molecule.  Thus,  H2  + CI2  — 2HC1,  should  be  written  as  the 
e({uation  representing  the  combination  of  hydrogen  and  chlorine,  rather 
tlian  H -h  Cl  = HC'l.  This  rule  applies  more  especially  to  the  gaseous 
elements,  as  their  molecular  constitution  lias  been  definitely  ascertained. 
But  ill  the  case  of  tlie  solid  elements  the  number  of  atoms  in  the  molecule 


INTRODUCTORY. 


15 


is  not  so  well-known  and  therefore  such  elements  are  usually  written  as 
so  many  single  atoms,  and  not  as  molecules. 

32.  Avogadro’s  Law. — The  fact  that  all  gases,  whether  elementary 
or  compound,  expand  and  contract  at  the  same  rate,  when  subjected 
to  variations  of  temperature  and  pressure,  has  an  important  bearing 
on  their  probable  molecular  constitution.  Their  similarity  in  this  respect 
has  led  to  the  assumption  express£d  in  the  “ Law  of  Avogadro  ” : — “ Under 
similar  conditions  of  temperature  and  pressure,  equal  volumes  of  all  gases 
contain  the  same  number  of  molecules.”  From  this  it  follows,  that  at 
the  same  temperature  and  under  the  same  pressure,  the  volume  of  any 
gaseous  molecule  is  the  same  whatever  may  be  the  nature  and  composition 
of  the  gas.  The  density  of  a gas  being  known,  its  molecular  weight  is 
easily  calculated.  The  clensity  of  a gas  is  the  weight  of  any  volume,  com- 
pared with  that  of  the  same  volume  of  hydrogen,  measured  at  the  same 
temperature  and  pressure,  and  taken  as  unity.  It  has  already  been  stated 
that  the  molecule  of  hydrogen  contains  two  atoms  ; its  molecular  weight, 
expressed  in  terms  of  its  atomic  weight,  is  consequently  2.  The  molecular 
weight  of  any  gas  is  the  weight  of  that  volume  which  occupies  the  same  space 
as  do  two  parts  by  weight  of  hydrogen  ; or  is  identical  with  the  number 
obtained  by  doubling  the  density.  Similar  conditions  of  temperature  and 
pressure  are  always  understood  in  speaking  of  the  comparative  weights  of 
gases.  Conversely,  as  the  molecular  weight  is  the  sum  of  the  weights  of 
the  constituent  atoms,  the  density  of  a gas  may  be  calculated  from  its 
formula.  Thus,  carbon  dioxide  gas  has  as  its  formula,  CO, ; its  molecular 

44 

weight  is  12  + (16  x 2=)  32  = 44;  the  density  is  ^ =22.  Here  again 

it  must  be  remembered  that  the  molecular  weight  is  primarily  determined 
from  the  density,  and  not  the  density  from  the  molecular  weight. 

33.  Absolute  Weight  of  Hydrogen. — ^As  hydrogen  is  taken  as  the  unit 
of  comparison  for  other  gases,  it  is  necessary  that  its  absolute  weight  be 
determined  with  the  greatest  exactitude.  Experiment  has  shown  that 
1 litre  of  hydrogen,  at  normal  temperature  and  pressure,  weighs  0*0896 
gram  ; or  11*2  litres  weigh  1 gram.  The  student  must  make  up  his  mind 
to  remember  this  figure  ; to  quote  Hofmann,  the  fact  that  at  0°  C.  and  760 
m.m.  pressure,  1 litre  of  hydrogen  weighs  0*0896  gram,  should  be  impressed 
“as  it  were  with  a graving  tool  on  the  memory.”  The  weight  in  grams 
of  a litre  of  any  gas  is  its  density  X 0*0896.  Thus,  the  density  of  carbon 
dioxide  gas  is  22;  the  weight  of  a litre  is  22  x 0*0896  = 1*9712  grams. 

34.  Laws  of  Chemical  Combination  by  Volume. — Not  only  does  chemical 
combination  follow  definite  laws,  so  far  as  weight  is  concerned,  but  also 
equally  definite  laws  govern  the  proportions  by  volume  in  the  case  of  gaseous 
bodies.  For  example,  experiment  shows  that  one  volume  of  hydrogen  unites 
with  one  volume  of  chlorine  to  form  two  volumes  of  hydrochloric  acid 
gas.  So,  too,  two  volumes  of  hydrogen  unite  with  one  volume  of  oxygen 
to  form  two  volumes  of  water-gas  (steam).  Again,  ammonia  consists 
of  three  volumes  of  hydrogen,  united  with  one  of  nitrogen,  to  form  two 
volumes  of  ammonia.  The  reactions  are  expressed  in  the  following  equa- 
tions :• — 


H^ 

+ 

CI2 

— 

2HC1. 

Hj^lrogen. 

Chlorine. 

Hydrochloric  Acid. 

2H2 

+ 

O2 

— 

2H2O. 

Hydrogen. 

Oxygen. 

Water. 

3H2 

+ 

N2 

2NH3. 

Hydrogen. 

Nitrogen. 

Ammonia. 

It  will  be  observed  that  in  the  first  equation  one  molecule  of  hydrogen 


16 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


unites  with  one  molecule  of  chlorine  to  form  two  molecules  of  hydrochloric 
acid  : the  application  of  Avogadro’s  Law,  therefore,  teaches  that  these 
elements  will  unite  in  equal  quantities  of  one  volume  to  form  two  volumes, 
of  hydrochloric  acid.  In  the  same  way,  the  proportions  by  volume  in  which 
chemical  changes  occur  between  gaseous  bodies  are  always  expressed  in 
the  equation,  it  being  remembered  that  all  gaseous  molecules  occupy  the 
same  space  when  measured  at  the  same  temperature  and  pressure.  The 
following  is  a useful  method  of  writing  such  equations,  when  the  object 
is  to  show  the  proportions  by  volume  in  a chemical  change  in  which  any 
gaseous  body  is  involved. 


H2 

+ 

CI2 

2HC1. 

1 volume. 

1 volume. 

2 volumes. 

2H2 

+ 

O2 

— 

2H2O. 

2 volumes. 

1 volume. 

2 volumes. 

3H2 

+ 

N2 

2NH3. 

3 volumes. 

1 volume. 

2 volumes. 

35.  Acids,  Bases,  and  Salts. — ^The  name  acid  is  a famihar  one,  because 
it  is  continually  applied  in  everyday  parlance  to  anything  which  is  sour. 
A number  of  bodies  possess  this  distinction  in  common  ; to  the  chemist,, 
the  sourness  of  an  acid  is  but  an  accidental  property,  as,  according  to  his 
definition  of  these  bodies,  substances  are  included  as  acids  that  are  not 
sour  to  the  taste.  An  acid  may  be  defined  as  a body  which  contains  hydrogen, 
which  hydrogen  may  be  replaced  by  a metal  (or  group  of  elements  equivalent 
to  a metal),  when  presented  to  the  acid  in  the  form  of  an  oxide  or  hydroxide 
(hydrate).  As  a class,  the  acids  are  sour  ; they  are  also  active  chemical 
agents  ; most  acids  are  characterised  by  the  property  of  changing  the  colour 
of  a solution  of  litmus,  a naturally  blue  body,  to  a red  tint.  Oxygen  is  a 
constituent  of  most  acids.  These  are  termed  “ oxy-acids.”  A few  in  which 
it  is  absent  are  termed  “ hydr-acids.”  Hydrochloric  acid,  HCl,  is  an  example 
of  these  bodies.  Most  of  the  oxy-acids  are  produced  by  the  union  of  water 
with  an  oxide — thus,  oxide  of  sulphur  and  water  form  sulphuric  acid  : — 

SO3  + H2O  ==  H2SO4. 

Sulphur  Trioxide.  Water.  Sulphuric  Acid. 

The  oxides,  which  by  union  with  water  form  acids,  are  termed  anhydrides, 
or  anhydrous  acids.  They  are  usually  non-metallic  oxides,  but  sometimes 
consist  of  metals  combined  with  a comparatively  large  number  of  atoms 
of  oxygen. 

A Base  is  a compound,  usually  an  oxide  or  hydroxide,  of  a metal  (or 
group  of  elements  equivalent  to  a metal),  which  metal  (or  group  of  elements) 
is  capable  of  replacing  the  hydrogen  of  an  acid,  when  the  two  are  placed, 
in  contact.  The  greater  number  of  metallic  oxides  are  bases.  Bases, 
as  well  as  acids,  differ  considerably  in  their  chemical  activity.  Certain 
l)ases  are  characterised  by  being  soluble  in  water,  to  which  they  impart 
a peculiar  soapy  feel.  These  bases  are  termed  “ alkalies,”  and  possess 
the  property  of  restoring  the  blue  colour  to  reddened  litmus.  The  most 
important  alkalies  are  sodium  hydroxide,  NaHO,  and  potassium  hydroxide, 
KHO.  The  bases,  lime,  CaO,  baryta,  BaO,  and  magnesia,  MgO,  are  more 
or  less  soluble  in  water,  and  also  turn  reddened  litmus  blue.  They,  with 
SrO,  constitute  the  group  known  as  the  “ Alkaline  Earths.”  Hydroxides 
are  compounds  of  oxides  with  water,  thus  : — 

Na20  + H2O  2NaHO. 

‘ Sodium  Oxido.  Water.  Solium  Hydroxide. 

When  an  acid  and  base  react  on  each  other,  the  body,  produced  by  the 
replacement  of  the  hydrogen  of  the  acid  by  the  metal  of  the  base,  is  termed 

a Salt.  Water  is  also  produced  during  the  reaction.  When  the  acid  and 


INTRODUCTORY. 


17 


base  which  have  thus  reacted  are  both  of  something  like  the  same  degree 
of  strength,  the  resultant  salt  is  commonly  without  action  on  litmus  ; that 
is  it  does  not  affect  the  colour  whether  it  be  red  or  blue.  The  salt  is  then 
said  to  be  neutral.  For  example,  when  sulphuric  acid,  a strong  acid,  acts 
on  potassium  hydroxide,  a strong  base,  the  resultant  salt,  potassium  sulphate, 
has  no  action  on  litmus.  But  when  the  acid  is  strong  and  the  base  feeble, 
or  vice  versa,  the  resultant  salt  will  be  governed  in  its  degree  of  neutrality 
by  the  predominant  component.  Thus  when  potassium  hydroxide  com- 
bines with  carbonic  acid  (a  weak  acid)  the  salt,  potassium  carbonate,  is 
strongly  alkaline  to  litmus.  That  is,  it  vigorously  restores  the  blue  colour 
to  litmus  which  has  been  reddened.  The  action  of  acid  and  base  on  each 
other  is  illustrated  in  the  following  equation  : — 

HCl  -f  NaHO  = NaCl  -f  H^O. 

Acid.  Base.  Salt.  Water. 

36.  Compound  Radicals. — ^At  times  a group  of  elements  enters  into  the 
composition  of  a body,  and  performs  functions  very  similar  to  those  of  an 
atom  of  an  element.  Such  groups  are  not  only  found  to  form  numbers 
of  very  definite  compounds,  but  may  be  even  transferred  from  one  com- 
pound to  another  without  undergoing  decomposition.  Groups  of  atoms 
of  different  elements  which  possess  a distinct  individuality  throughout  a 
series  of  compounds,  and  behave  therein  as  though  they  were  elementary  bodies, 
are  termed  “ Compound  Radicals.” 

37.  Quanti valence  or  Atomicity. — Referring  back  to  the  three  com- 
pounds of  hydrogen  mentioned  in  paragraph  34,  it  will  be  observed  that 
one  atom  each  of  chlorine,  oxygen,  and  nitrogen,  combines  respectively 
with  one,  two,  and  three  atoms  of  hydrogen.  If  chlorine  and  oxygen  com- 
pounds be  classified  and  compared,  it  is  found  that  oxygen  in  almost  every 
instance  combines  with  just  double  as  many  atoms  of  the  other  element 
as  does  chlorine.  The  atom-combining  power  of  elements  varies — Quan- 
tivalence  or  Atomicity  is  the  measure  of  that  combining  power.  Among 
the  elements,  hydrogen,  sodium,  and  chlorine  are  characterised  by  the 
fact  that  one  atom  of  each  rarely  combines  with  more  than  one  atom  of 
any  other  element.  Their  atomicity  is  unity,  and  as  every  other  element 
forms  a chemical  compound  with  one  or  more  of  these,  the  atomicity  of 
any  element  can  usually  be  determined  by  observing  with  how  many  atoms 
of  one  of  these  three  elements  an  atom  of  the  element  in  question  enters 
into  combination.  The  atomicity  of  the  different  elements  is  given  in 
the  table  included  in  paragraph  24.  Elements  with  an  atomicity  of  one 
are  termed  monads  ; of  two,  dyads  ; three,  triads  ; four,  tetrads  ; five, 
pentads  ; and  of  six,  hexads.  It  is  often  convenient  to  express  the  atomicity 
of  an  element  graphically.  This  is  done  by  attaching  a series  of  lines  to 
the  atom,  according  to  its  atomicity.  These  lines  may  be  viewed  as  indicat- 
ing the  number  of  links  or  bonds  with  which  the  particular  atom  can 
combine  with  other  atoms.  Of  the  actual  nature  of  the  force  which  holds 
atoms  together  in  chemical  compounds,  nothing  can  be  here  stated  : the  bonds 
must  only  be  viewed  as  indications  of  the  number  of  such  units  of  atom- 
combining power.  The  following  are  examples  of  these  graphic  symbols  : — - 

H—  Cl—  — 0—  — =zC  = 

Hydrogen.  Chlorine.  Oxygen.  Boron.  Carbon. 

The  same  two  elements  often  form  a series  of  two  or  more  compounds 
with  each  other ; under  these  circumstances  the  atomicity  must  vary. 
In  the  great  majority  of  such  compounds,  the  atomicity  increases  or 
diminishes  by  intervals  of  two — that  is,  the  atomicity  is  either  even  or 
odd  for  an  element  throughout  all  its  compounds.  This  is  sometimes 

c 


18 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


accounted  for  by  the  supposition  that  two  of  the  bonds  of  an  element  may, 
by  their  union,  mutually  satisfy  each  other.  This  is  not,  however,  invari- 
ably the  case,  as  certain  well-marked  exceptions  to  this  rule  are  known. 
The  highest  knov/n  atomicity  of  an  element  is  termed  its  “ absolute  ” 
atomicity  ; the  atomicity  in  any  particular  compound  is  the  “ active  ” 
atomicity  ; the  absolute,  less  the  active,  atomicity  is  the  “ latent  ” atom- 
icity. 


38.  Basicity  of  Acids. — In  order  to  form  salts,  different  acids  require 
different  quantities  of  a base  : the  measure  of  this  quantity  is  termed 
the  “ basicity  ” of  the  acid.  The  basicity  of  an  acid  depends  on  the  number 
of  atoms  of  hydrogen  it  contains  that  may  be  replaced  by  the  metal  of  a 

base.  In  forming  salts,  one  atom  of  hydrogen  is  replaced  by  one  atom 
of  a monad  metal,  two  atoms  of  hydrogen  by  an  atom  of  a dyad,  and  so 
on.  In  the  case  of  acids  which  contain  more  than  one  atom  of  replaceable 
hydrogen,  salts  are  sometimes  formed  in  which  a part  only  of  the  hydrogen 
is  replaced  ; such  salts  are  termed  “ acid  ” salts,  while  those  in  which  the 
whole  of  the  hydrogen  is  replaced  are  termed  “ normal  ” salts.  The  follow- 
ing are  typical  examples  of  acids  and  the  corresponding  salts  : — 


Monobasic  Acid. 

HNO3. 

Nitric  Acid. 

NaNOe. 

Sodium  Nitrate. 


Ca(N03)2. 

Calcium  Nitrate. 


Dibasic  Acid. 

H2SO4. 

Sulphuric  Acid. 

Na2S04. 
Sodium  Sulphate. 

HNaSO,. 

Acid  Sodium  Sulphate. 

CaS04. 

Calcium  Sulphate. 


Tribasic  Acid. 

H3PO4. 
Phosphoric  Acid. 

Na3P04. 

Sodium  Phosphate. 

Na2HP04. 

Disodic  Hydrogen  Phosphate. 


Ca3(P04)2* 
Calcium  Phosphate. 


It  is  often  convenient  to  view  the  acids  in  the  light  of  their  being  com- 
pounds of  the  anhydrides  with  water  : the  corresponding  salts  may  then 
be  written  as  compounds  of  the  bases  with  the  anhydrides.  This  method 
is  almost  invariably  employed  when  calculating  the  relative  quantities 
of  metals  and  acids  in  bodies  when  subjected  to  analysis.  Subjoined 
are  the  formulse,  written  in  this  manner,  of  the  acids  and  salts  previously 
given  as  examples  : — 


H3O,  N2O5. 

Two  Molecules  of 
Nitric  Acid. 

Na20,  N2O5. 
Two  Molecules  of 
Sodium  Nitrate. 


CaO,  N2O5. 

One  Molecule  of 
Calcium  Nitrate. 


H2O,  SO3. 

Sulphuric  Acid. 

Na20,  SO3. 
Sodium  Sulphate. 

Na20,  H2O,  (803)2. 

Two  Molecules  of 
Acid  Sodium  Sulphate. 

CaO,  SO3. 

Calcium  Sulphate. 


(H20)3,  P2O5. 
Two  Molecules  of 
Phosphoric  Acid. 

(Na20)3,  P2O5. 
Two  Molecules  of 
Sodium  Phosphate. 

(NaaOjH^O,  P2O5. 

Two  Molecules  of  Disodic 
Hydrogen  Phosphate. 

(CaO)3,  P2O6. 

One  Molecule  of 
Calcium  Phosphate. 


39.  Chemical  Calculations. — ^Most  of  the  chemical  calculations  necessary 
in  analytic  work  may  be  readily  made  by  the  help  of  chemical  formulse 
and  equations,  together  with  a table  of  combining  weights.  The  following 
are  illustrations  of  some  of  the  most  important  of  these  calculations. 


40.*  Percentage  Composition  from  Formula. — Chemists  usually  express 
the  results  of  analysis  of  a substance  in  parts  per  cent.,  so  that  in  the  case 
of  a chemical  compound  it  is  often  necessary  to  be  able  to  calculate  its 
chemical  formula  from  the  percentage  composition ; or  conversely,  the 
percentage  composition  from  the  formula.  The  latter  operation,  as  being 


INTRODUCTORY. 


19 


the  simpler,  shall  be  first  explained.  It  is  possible  from  the  formula  of 
any  body  to  arrive  at  the  molecular  weight  of  the  compound,  and  the  relative 
weight  present  of  each  element.  Thus,  to  find  the  percentage  composition 
of  acid  sodium  sulphate  : — 

The  formula  is 

Na  H S O4 

23  + 1 + 32  + (16  X 4 =--)  64  = 120. 

From  the  combining  weights,  given  beneath  each  element,  with  their  sum 
at  the  end,  it  is  seen  that  the  molecule  weighs  120,  and  contains  23  parts 
of  sodium.  Knowing  that  120  parts  contain  23,  it  is  exceedingly  easy  to 
calculate  the  number  of  parts  per  100,  as  the  problem  resolves  itself  into 
one  of  simple  proportion  : — 


As 

120  : 

: 100  : 

: 23  : 

: 19-17  per  cent,  of  sodium. 

As 

120  : 

: 100  : 

: 1 : 

0-83 

,,  hydrogen. 

As 

120  ; 

: 100  : 

: 32  ; 

: 26-66 

, , sulphur. 

As 

120  : 

: 100  : 

: 64  : 

53-33 

„ oxygen. 

99-99 

Precisely  the  same  method  of  calculation  has  been  applied  to  the  deter- 
mination of  the  percentages  of  hydrogen,  sulphur,  and  oxygen.  As  the 
results  seldom  work  out  to  a terminated  decimal,  the  added  percentages 
usually  amount  to  only  99-99  ; but  by  continuing  the  calculation,  any 
additional  number  of  9’s  could  be  obtained,  and  as  0-9  recurring  is  equal 
to  1-0,  so  99-9  recurring  is  equivalent  to  100-00.  As  another  example, 
let  it  be  required  to  determine  the  percentage  of  base  and  anhydrous  acid 
respectively  in  calcium  phosphate.  This  salt  is  represented  by — 

(Ca  0 )3  P2  O5 

(40+16=)56x3  62-h80 

168  ^ -f  14^^  = 310 

The  molecule,  which  weighs  310,  contains  168  of  lime  (CaO)  and  142  of 
phosphoric  anhydride  (P2O5);  consequently 

As  310  : 100  : : 168  : 54-19  per  cent,  of  lime. 

As  310  : 100  : : 142  : 45-81  ,,  ,,  phosphoric  anhydride. 


100-00 


41.  Formula  from  Percentage  Composition. — Let  the  following  represent 
the  results  of  analysis  of  a body 


Sodium 
Nitrogen  . . 
Hydrogen  . . 
Phosphorus 
Oxygen 

. . 16-79 

. . 10-22 
3-65 
. . 22-63 

. . 46-71 

100-00 

As  a first  step  toward  obtaining  the  formula,  divide  the  percentage  of 
each  element  by  its  atomic  weight,  the  result  will  be  a series  of  numbers 
in  the  ratio  of  the  number  of  atoms  of  each  element — 


20 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


16*79 

23 

1^*22 

14 

3*65 

1 

22^3 

46*71 

16 


0*73  of  Sodium. 

0*73  of  Nitrogen. 
3*65  of  Hydrogen. 
0*73  of  Phosphorus. 
2*92  of  Oxygen. 


It  is  next  necessary  to  find  the  lowest  series  of  whole  numbers  that  corre- 
spond to  these  ; such  a series  may  be  obtained  by  dividing  each  number  by 
the  lowest  one  of  the  series  : — 


0*73 

0-73 

Oy^73 

0*73 

3*65 

0*73 

0*73 

0*73 

2^92 

0*73 


= 1 atom  of  Sodium. 

= 1 atom  of  Nitrogen. 

= 5 atoms  of  Hydrogen. 
= 1 atom  of  Phosphorus. 
= 4 atoms  of  Oxygen. 


The  formula  of  the  compound  is,  therefore,  Na]NH5p04 ; itsname  is  “hy- 
drogen ammonium  sodium  phosphate."'  The  formula  obtained  in  this  way 
is  the  simplest  possible  for  the  body  in  question  : it  is  evident  that  the  per- 
centage composition  would  be  the  same  if  there  were  double  or  any  other 
multiple  of  the  number  of  atoms  of  each  element  in  the  molecule.  Other 
considerations  are  taken  into  account  in  determining  whether  the  correct 
molecular  formula  is  really  the  simplest  thus  obtained,  by  calculation,  from 
the  percentage  composition,  or  a multiple  of  the  same.  Such  simplest  possible 
formula  is  termed  an  Empirical  Formula. 


42.  Calculations  of  Quantities. — An  exceedingly  common  type  of  calcula- 
tion is  that  in  which  it  is  required  to  know  the  quantities  of  one  or  more 
substances  required  to  produce  a certain  quantity  of  another  body.  Thus, 
hydrogen  is  commonly  obtained  by  the  action  of  zinc  on  sulphuric  acid  ; 
suppose  that  10  grams  of  hydrogen  are  required  for  some  operation  : what 
weights  respectively  of  zinc  and  sulphuric  acid  are  necessary  for  the  pur- 
pose ? Here,  again,  the  equation  gives  the  relative  weights  of  each  ele- 
ment and  compound  participating  in  the  reaction.  In  every  such  calcula- 
tion it  is  absolutely  necessary  that  the  equation  and  combining  weights  be 
known  ; but  granted  these,  no  other  difficulties  arise  beyond  those  which 
can  be  readily  overcome  by  an  intelligent  application  of  the  principles  of 
proportion. 


In  the  case  in 

question  the  equation  is  : — 

Zn 

+ H2  S O4 

= Zn  S O4 

+ H2. 

65 

2 + 32  + 64 

65+32  + 64 

2. 

98  ^ 

161 

Zinc 

Sulphuiic  Acid. 

Zinc  Sulphate. 

Hydrogen. 

To  produce  two  parts  by  weight  of  hydrogen,  65  of  zinc  and  98  of  sul- 
phuric acid  are  required,  then — 


INTRODUCTORY. 


21 


As  2 : 10  : : 65  : 325  grams  of  zinc  required. 

As  2 : 10  : : 98  : 490  ,,  ,,  sulphuric  acid  required. 


Another  instance  may  be  given,  in  which  not  only  weights  but  also 
volumes  of  gases  have  to  be  calculated.  It  is  required  to  know  how  much 
carbon  dioxide  gas  in  cubic  centimetres  and  in  cubic  inches  is  evolved  by 
the  fermentation  of  28*35  grams  (=  1 ounce)  of  [pure  cane  sugar,  the  gas 
being  measured  at  a temperature  of  20°  C.  and  765  millimetres  pressure  ; 
it  being  assumed  that  the  whole  of  the  sugar  is  resolved  into  alcohol  and 
carbon  dioxide.  The  chemical  changes  involved  in  this  process  may  be 
represented  by  the  following  equations  : — 


144+22  + 176 

U2 

Cane  Sugar. 


+ H,  0 

2 + 16 

"Is" 

Water. 


2C,  H,,  0,. 
72  + 12+96 

2x180=360 

Glucose. 


In  the  first  place  one  molecule,  equalling  342  parts  by  weight  of  cane  sugar, 
is  converted  into  two  molecules  of  glucose,  each  weighing  180,  or  the  two 
weighing  360. 


2C,  H„  O, 

72+12+96 

2x180=360 

Glucose. 


4C2H5H  0 
21+5+1  + 16 

^46^184 

Alcohol. 


+ 4C  O2. 
12+32 

4>S=176 

Carbon  dioxide. 


The  two  molecules  of  glucose,  weighing  360,  are  next  decomposed  into  four 
molecules  of  alcohol,  having  a total  weight  of  184  ; and  four  molecules  of 
carbon  dioxide,  each  weighing  44,  and  the  whole  176.  From  342  parts  by 
weight  of  cane  sugar,  176  parts  by  weight  of  carbon  dioxide  are  produced  ; 
then — 

As  342  : 28*35  : : 176  : 14*59  grams  of  carbon  dioxide,  yielded  by 
28*35  grams  of  cane  sugar. 

The  next  step  is  to  determine  what  is  the  volume  of  14*59  grams  of  car- 
bon dioxide  at  N.T.P.  The  molecular  weight  of  carbon  dioxide  being  44, 
its  density  must  be  22  ; one  litre  of  hydrogen  weighs  0*0896  grams,  and 
therefore  1 litre  of  carbon  dioxide  must  weigh  0*0896  X 22  = 1 *9712  grams  ; 
then — 

i WlZ  ""  N.T.P. 

Applying  the  laws  previously  given  by  which  the  relations  between  the 
volume  and  temperature  and  pressure  of  a gas  are  governed  ; then — 


As  273  : 293  : : 7401  ) _ 293  X 760x7*401 
765  : 760  • J 273  x 765 

= 7*891  litres  at  20°  C.  and  765  m.m.  pressure  = 7891  cubic  centimetres 
As  16*39  c.c.  = 1 cubic  inch,  then 
= 481*7  cubic  inches. 

16*39 


28*35  grams  or  one  ounce  of  cane  sugar  would  yield,  according  to  the  ques- 
tion given,  7891  c.c.  or  481*7  cubic  inches  of  carbon  dioxide  gas  at  20°  C. 
and  765  m.m.  pressure. 

The  weight  of  sugar  necessary  to  yield  a certain  volume  of  gas  would 
be  calculated  on  the  same  principles  ; as  an  illustration,  the  reverse  of  the 
^calculation  just  made  is  appended.  Required  to  know  the  weight  of  cane 


22 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


sugar  necessary  to  produce  481*7  cubic  inches  or  7891  cubic  centimetres  of 
carbon  dioxide  gas  at  20°  C.  and  765  mm.  pressure. 


273x765x7891 

293x760 


=7401 


c.c.  at  N.T.P.  = 7*401  litres. 


7*401X1*9712=14*59  grams  of  CO2. 

As  176  : 14*59  : : 342  : 28*35  grams  of  cane  sugar  required. 


43.  Gaseous  Diffusion. — It  is  a well-known  fact  that  gases  mix  with 
each  other  with  remarkable  readiness.  For  instance,  if  in  a large  room  a 
jar  of  chlorine  is  opened  at  the  level  of  the  floor,  the  presence  of  the  gas 
may  be  detected  by  its  powerful  odour,  within  a few  seconds,  in  every  part 
of  the  room.  The  natural  process  by  which  the  chlorine  is  thus  disseminated 
through  the  air  is  termed  “ gaseous  diffusion  ; it  takes  place  between 
gases,  even  though  the  heavier  is  at  first  at  the  lower  level.  In  other  words,, 
a heavy  gas  will  diffuse  up  into  a superincumbent  light  gas,  while  the  light 
gas  will  make  its  w'ay  downwards  and  mix  with  the  heavier  one.  In  this 
way  different  gases,  when  placed  in  the  same  space,  rapidly  produce  of 
themselves  an  uniform  mixture.  Tliis  process  of  diffusion  will  also  go  on 
through  a porous  membrane,  as,  for  example,  a thin  diaphragm  of  plaster  of 
Paris  or  porous  earthenware.  Thus,  if  a vessel  be  divided  into  two  parts 
by  a thin  partition  of  porous  material,  and  the  one  half  be  filled  with  one 
gas  and  the  other  with  another,  they  will  be  found  after  some  time  to  have 
become  thoroughly  intermixed  with  each  other.  The  rate  of  diffusion  of  all 
gases  through  such  a diaphragm  is  not  the  same,  but  depends  on  their  den- 
sities. The  rate  of  diffusion  of  gases  is  inversely  as  the  square  root  of  their  density. 
Thus,  hydrogen  and  oxygen  have  respectively  densities  of  1 and  16  ; hydro- 
gen diffuses  four  times  as  rapidly  as  does  oxygen. 


44.  Solution. — ^When  certain  solid  substances,  of  which  salt  is  a con- 
venient example,  are  added  to  water,  the  solid  disappears,  and  is  said  to  be 
dissolved.  The  liquid  which  has  been  used  for  dissolving  the  substance  is 
said  to  be  a solvent,  the  substance  which  is  dissolved  is  called  a solute, 
and  the  liquid  which  as  a result  contains  the  dissolved  substance  is 
termed  a solution.  Solutions  may  be  prepared  of  gases,  liquids  and  solids, 
liquid  solution  may  be  defined  as  a homogeneous  or  uniform  liquid  mixture 
of  a gas,  a liquid,  or  a solid  with  a liquid.  The  act  of  solution  is  not  in  itself 
one  of  chemical  combination  between  the  dissolved  substance  and  the 
solvent  (although  solution  may  be  followed  in  addition  by  chemical  com- 
bination). Thus  when  a solution  of  salt  in  water  is  heated,  the  water  may 
be  driven  off  and  the  whole  of  the  salt  recovered  in  an  unchanged  condition. 

45.  Gaseous  Solution. — Gases  vary  very  greatly  in  their  degree  of  solu- 
bility in  water.  In  the  following  table  is  given  the  volumes  of  each  gas 
dissolved  in  100  volumes  of  water,  at  the  temperatures  of  0°  and  15°  C. 
respectively — 


Hydrogen 

O’C. 

2*15 

15°C. 

1*91 

Nitrogen 

2*03 

1*48 

Oxygen 

4*11 

2*99 

Chlorine 

solid 

23*68 

Carbon  dioxide 

179*67 

100*20 

Sulphur  dioxide 

6886*1 

4356*4 

Hydrochloric  acid  . . 

. . 50590*0 

45800*0 

Ammonia 

. . 104960*0 

72720*0 

•mparatively  small  quantities  of  hydrogen,  nitrogen. 

and  oxygen 

INTRODUCTORY. 


23 


thus  dissolved,  but  that  of  oxygen  is  sufficiently  large  to  have  most  important 
results  in  the  economy  of  nature.  Carbon  dioxide  is  much  more  soluble, 
water  absorbing  about  its  own  volume  at  ordinary  temperatures.  The 
last  mentioned  gases  are  examples  of  extremely  soluble  gases  ; their  various 
solutions  have  important  applications  in  chemistry  and  the  arts.  It  will 
be  observed  that  all  the  gases  mentioned  are  less  soluble  in  water  at  15*^ 
than  at  0°  C.,  and  as  the  temperature  is  raised  the  solubility  still  further 
diminishes.  Most  gases  may,  in  fact,  be  entirely  expelled  from  water  by 
the  act  of  boiling.  The  weight  of  a gas  dissolved  by  water  is  increased  by 
pressure,  and  is  governed  by  an  interesting  law,  viz.,  that  it  is  directly  pro- 
portional to  the  pressure  exerted.  As  the  volume  of  a gas  is  in  inverse  ratio 
to  the  pressure,  it  follows  that  the  volume  of  a gas  dissolved  by  water  is  the 
same  at  all  pressures.  The  so-called  mineral  or  aerated  waters  are  prepared 
by  forcing  carbon  dioxide  into  the  water  under  pressure.  On  the  release  of 
the  pressure  the  gas  escapes  and  causes  the  familiar  effervescence.  Most  of 
the  gases  mentioned  in  the  foregoing  table  are  much  more  soluble  in  alcohol 
than  in  water  ; thus  100  volumes  of  alcohol  at  15°  C.  dissolve  28  volumes, 
of  oxygen  and  320  volumes  of  carbon  dioxide  respectively. 

46.  Solution  of  Liquids. — ^Some  liquids  on  being  placed  together  mix 
or  are  said  to  be  “ miscible  in  all  proportions  ; an  example  of  these  is  found 
in  alcohol  and  water.  Others  practically  refuse  altogether  to  mix,  as,  for 
example,  water  and  oil.  Others  again  are  to  a limited  extent  soluble  in 
each  other.  One  of  the  best  illustrations  of  these  is  that  of  water  and 
ether  ; if  these  be  shaken  together  in  about  equal  proportions  and  then 
allowed  to  stand,  the  ether  being  the  lighter,  separates  out  as  a layer  on  the 
surface  of  the  water.  On  examination,  however,  the  ether  will  be  found  to 
have  water  dissolved  in  it  to  the  extent  of  about  3 per  cent.  ; and  the  water 
will  have  dissolved  about  10  per  cent,  of  ether.  (As  a matter  of  fact,  oils 
and  water  are  also  very  slightly  soluble  in  each  other,  but  the  amount  of 
oil  so  dissolved  is  so  minute  as  to  be  a negligible  quantity,  while  traces 
only  of  water  are  dissolved  by  oil.) 

47.  Solution  of  Solids. — ^Solids  vary  very  greatly  in  their  degree  of 
solubility  in  water.  Among  the  mineral  salts,  barium  sulphate  is  almost 
absolutely  insoluble ; calcium  sulphate  is  dissolved  to  the  extent  of  1 part 
in  700  parts  of  water  ; while  at  the  other  end  of  the  scale  2 parts  of  crystal- 
lized magnesium  sulphate  are  dissolved  by  3 parts  of  water  at  ordinary 
temperatures.  In  the  majority  of  instances  the  solubility  of  substances  in 
water  is  increased  by  an  elevation  of  temperature,  but  this  is  not  an  at  solute 
rule.  Lime,  for  example,  is  much  more  soluble  in  cold  than  in  hot  water. 
Salt  is  almost  equally  soluble  in  cold  and  hot  water  ; at  0°  C.  water  dissolves 
35*5  per  cent,  of  salt,  and  41 ’2  per  cent,  at  109*5°  C.,  the  boiling  point  of 
the  solution.  Sugar,  on  the  other  hand,  is  soluble  in  about  half  its  weight 
of  cold  water,  and  in  boiling  water  in  all  proportions.  In  order  to  deter- 
mine the  solubility  of  any  particular  substance,  it  must  be  allowed  to  remain 
in  contact  with  the  solvent  until  the  latter  has  dissolved  as  much  as  it 
possibly  can,  and  leaves  the  excess  in  contact  with  the  solution.  Under 
such  conditions,  the  solvent  takes  up  a definite  proportion  of  the  dissolved 
body  for  each  particular  temperature. 

A perfect  solution  is  quite  clear  and  free  from  any  eloudiness,  as  the 
solid  partieles  will  have  completely  disappeared  from  sight.  Any  turbidity 
is  caused  by  the  presence  of  minute  solid  or  liquid  particles  in  susrension. 
It  is  incorrect,  therefore,  to  speak  of  a mixture  of  a permanently  solid  sub- 
stance with  water  in  the  form  of  a creamy  mass  as  a solution.  Similarly 
one  does  not  dissolve  yeast  in  water  ; one  is  simply  broken  down  into  an 
intimate  admixture  with  the  other.  Water  dissolves  many  of  the  mineral 


24 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


salts,  but  does  not  dissolve  resins  or  fatty  matters.  The  resinous  bodies, 
of  which  shellac  may  be  taken  as  an  example,  are  soluble  in  alcohol ; while 
fats  may  be  readily  dissolved  by  ether,  chloroform,  and  light  petroleum 
spirit.  Water,  on  the  other  hand,  dissolves  certain  gelatinous  and  gummy 
bodies,  but  such  solutions  have  special  characteristics  to  which  further 
reference  is  made  in  the  following  paragraphs. 

48.  Osmose  and  Dialysis. — Liquids  which  are  miscible  with  each  other 
in  somewhat  the  same  way  as  gases,  also  undergo  diffusion  more  or  less 
rapidly.  The  laws  governing  diffusion  of  liquids  are  more  complex  than 
those  affecting  the  diffusion  of  gases  : not  only  gases,  but  also  liquids,  are 
capable  of  diffusion  through  a porous  diaphragm  ; such  diffusion  is  termed  “ Os- 
mose.” Some  of  the  most  remarkable  and  important  phenomena  of  liquid 
diffusion  are  those  exhibited  by  aqueous  solutions  of  different  substances. 
Thus,  let  a sort  of  drum-head  be  made  by  stretching  and  fastening  a piece 
of  bullock’s  bladder,  or  either  animal  parchment  or  vegetable  parchment 
paper,  over  a cylinder  of  some  impervious  material,  as  glass  or  gutta  percha. 
Float  this  in  a vessel  of  pure  water,  and  pour  inside  it  a strong  solution  of 
common  salt.  The  brine  and  the  pure  water  will  only  be  separated  from 
each  other  by  the  thin  membrane  of  bladder  or  other  similar  material. 
After  the  lapse  of  some  hours  it  will  be  found  that  the  solution  of  salt  will 
have  diffused  out  through  the  membrane  until  the  liquid  both  outside  and 
inside  the  floating  vessel  has  the  same  strength.  By  repeatedly  changing 
the  water  in  the  outer  vessel,  the  whole  of  the  salt  might  be  removed  from 
the  solution  wdthin  the  cylinder.  On  the  other  hand,  if  a solution  of  gum 
arabic  were  placed  within  the  parchment  drum,  and  subjected  to  precisely 
the  same  treatment,  the  gum  would  be  found  incapable  of  diffusion  through 
the  membrane.  If  a mixture  of  brine  and  gum  were  placed  in  the  cylinder 
wdth  parchment  bottom,  and  then  floated  on  the  surface  of  w'ater,  the  salt 
w^ould  diffuse  out  and  the  gum  remain  behind  : in  this  manner  a complete 
separation  of  the  two  might  be  effected.  The  separation  of  bodies  by  their 
respective  ability  or  inability,  when  dissolved,  to  diffuse  through  a porous  membrane, 
is  termed  “Dialysis.” 

49.  Crystalloids  and  Colloids. — ^All  bodies,  soluble  in  water,  are  capable 
of  being  divided  into  tw^o  great  classes,  known  respectively  as  “ crystalloids  ” 
and  “ colloids.”  Crystalloids  are  substances  which,  on  changing  from  the  liquid 
to  the  solid  state,  assume  a crystalline  form.  Bodies  are  said  to  be  crystalline  when 
they  consist  of  crystals,  and  for  chemical  purposes  a crystal  may  be  defined  as  matter 
which  has  spontaneously  assumed  during  the  act  of  solidification  a definite  geometric 
form.  In  crystals  there  is  also  a definite  internal  molecular  arrangement  related  to 
the  crystalline  form  by  certain  determinate  laws.  Solutions  of  crystalline  bodies 
are  usually,  but  not  invariably,  free  from  any  marked  viscosity.  Crystalline 
bodies  are  only  soluble  to  a definite  extent  in  water,  the  quantity  dissolved 
depending  more  or  less  on  the  temperature,  as  has  been  already  explained 
Jelly-like  substances,  as  gum  and  gelatin,  are  termed  “ Colloids,”  and  do  not  acquire, 
a crystalline  form  when  assuming  the  solid  state.  The  colloids  form,  wdien  treated 
w^ith  water,  sirupy,  viscous,  or  jelly-like  solutions.  They  maybe  said  to  be 
soluble  in  w^ater  in  all  proportions.  Thus,  if  a few  drops  of  water  be  added 
to  a piece  of  dry  gelatin,  the  water  will  be  absorbed  by  the  gelatin,  and 
after  a time  will  be  uniformly  diffused  throughout  the  wLole  mass.  Suc- 
cessive portions  of  w ater  may  thus  be  absorbed  by  the  gelatin,  which  will 
become  gradually  softer,  assuming  the  consistency  of  a jelly ; further  addi- 
tion of  water  produces  a solution  wdth  more  or  less  viscosity,  depending  on 
the  degree  of  concentration.  Crystalloids  are  especially  susceptible  of  dialysis  ; 
colloids  exhibit  under  similar  treatment  very  little  tendency  to  passthrough  a porous 


INTRODUCTORY. 


25 


membrane.  The  probable  reason  for  this  inability  on  the  part  of  colloids  is 
that  their  solution  particles  are  too  large  to  readily  pass  through  the  inter- 
stices in  the  porous  membrane.  The  membranes  used  for  dialysis  consist  of 
colloid  substances  : gelatin  in  the  jelly-like  form  at  times  is  a very  con- 
venient dialysing  agent.  The  apparatus  used  for  the  purpose  of  effecting 
dialysis  is  termed  a dialyser.  The  phenomena  of  liquid  diffusion  have  an 
exceedingly  important  bearing  on  many  chemical  changes  which  occur 
during  bread-making. 

50.  Measures  of  Weight  and  Volume. — It  will  be  here  convenient  to 
furnish  a statement  of  the  different  systems  of  weights  and  measures  usually 
employed  for  scientific  purposes.  The  chemist,  as  a rule,  prefers  the  metric 
system,  as  in  common  use  in  France,  to  the  very  complicated  system  of 
weights  and  measures  employed  in  this  country.  One  reason  is  that  the 
metric  system  is  extremely  simple  ; another,  that  the  measures  of  weight 
and  volume  are  directly  connected  with  each  other.  If  the  authors  simply 
followed  their  own  predilections,  metric  weights  and  measures  only  would 
be  used  throughout  this  work,  but  it  having  been  strongly  represented  to 
them  that  the  introduction  of  the  English  equivalents  of  the  different  weights 
employed  would  be  a help  to  some  of  their  readers,  they  also  have  been,  in 
most  cases,  given.  The  authors  are  conscious  that  the  result  of  this  inter- 
mixture is  often  incongruous,  but  to  those  familiar  with  the  metric  system 
this  will  present  no  difficulty,  while  to  those  who  are  unacquainted  with  it, 
it  mil  be  an  assistance.  It  is  nevertheless  urged  that  the  metric  system 
be  mastered  ; this  may  be  easily  done  in  a quarter  of  an  hour,  much  time 
will  then  be  saved  which  otherwise  would  have  to  be  spent  in  making 
calculations. 


51.  The  Metric  System. — The  unit  of  the  mstric  system  is  a “ metre,” 
which  is  the  length  of  a rod  of  platinum  that  is  deposited  in  the  archives  of 
France.  The  metre  measures  39*37  English  inches.  The  higher  and  lower 
measures  are  obtained  by  multiplying  and  dividing  by  10,  thus  : — 


Kilometre 

= 1000  metres 

= 39370  inches. 

Hectometre 

= 100 

= 3937 

Decametre 

10 

= 393*7 

Metre 

39*37 

Decimetre 

= 0*1  metre 

= 3*937 

Centimetre 

= 0*01  „ 

= 0*3937  inch 

Millimetre 

= 0*001  „ 

= 0*03937  „ 

In  the  above,  and  all  other  measures 

of  the  metric  system,  the 

kilo,  hecto,  and  deca  ” are  used  to  represent  1000,  100,  and  10  respec- 
tively ; and  “ deci,  centi,  and  milli,”  to  represent  a tenth,  hundredth,  and 
thousandth.  The  decimetre  is  very  nearly  4 inches  in  length,  and  the  milli- 
metre very  nearly  one  twenty-fifth  of  an  inch  : remembering  this,  measures 
of  the  one  denomination  can  be  roughly  translated  into  those  of  the  other. 
The  exact  length  of  a decimetre  is  shown  in  Fig.  1. 

The  unit  of  the  measure  of  capacity  is  the  “ litre,”  which  is  the  volume 
of  a cubic  decimetre  : — 


Kilolitre 

Hectolitre 

Decalitre 

Litre 

Decilitre 

Centilitre 

Millilitre 


= 1000 
= 100 

= 10 


Cubic  Inches. 

litres  = 61027 
„ = 6102*7 

„ = 610*27 


0*1  litre  = 
0-01  „ = 
0*001  „ = 


61*027 

6*1027 

0*61027 

0*06102 


Pints. 

1760*7 

176*07 

17*607 

1*7607 

0*17607 

0*017607 

0*00176 


Fluid  Ounces. 

35214 

3521*4 

352*14 

35*214 

3*5214 

0*3521 

0*0352 


26 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  decimetre  being  10  centimetres  in  length,  it  follows  that  a cubic 
decimetre  must  be  equal  to  1000  cubic  centimetres,  and  that  the  millilitre 
has  a volume  of  a cubic  centimetre.  The  name  “ cubic  centimetre,"'  or 
its  abbreviation  “ c.c.,"  is*  almost  always  used  in  preference  to  millilitre  ; 
thus,  a burette  or  pipette  is  said  to  deliver  50  c.c.,  while  a litre  measure  is 
often  termed  a “ 1000  c.c."  measure. 

A cubic  inch  is  equal  to  16*38  cubic  centimetres. 


1 

2 

3 

4 


6 

7 

8 


9 

10 


The  unit  of  the  measure  of  weight  is  the  “ gramme,"  or  “ gram  " ; this 
is  the  weight  of  a cubic  centimetre  of  distilled  water  at  its  maximum  density 


: 39*2°  F.) 

Kilogram  = 

1000  grams  = 

Grains. 

15432*3 

Avoirdupois  Ounces. 

35*2739 

Hectogram  = 

100  „ = 

1543*23 

3*52739 

Decagram  = 

10  „ 

154*323 

0*35273 

Gram  = 

15*4323 

0*03527 

Decigram  = 

0*1  gram  = 

1*54323 

0*00352 

Centigram  = 

0*01  „ - 

0*15432 

0*00035 

Milligram  = 

0*001  „ = 

0*01543 

0*0000351 

A kilogram  is  just  over  2 lb.  oz.,  and  a hectogram  is  very  nearly 
3J  oz.  An  ounce  avoirdupois  equals  28*35  grams. 

The  relation  between  the  weight  and  volume  of  water  is  a very  simple 
one,  the  volume  being  the  same  number  of  c.c.  as  the  weight  is  grams. 
With  other  liquids  the  volume  in  c.c.  X specific  gravity  = weight  in  grams. 


Each  side  of  this  square  measures 

1 Decimetre,  or 
10  Centimetres,  or 
100  Millimetres,  or 
3-937  English  inches. 

A litre  is  a cubic  measure  of  1 decimetre  in  the  side,  or  a 
cube  each  side  of  which  has  the  dimensions  of  this  figure. 

When  full  of  water  at  4°  C.  a litre  weighs  exactly  1 kilogram 
or  1000  grams,  and  is  equivalent  to  1000  cubic  centimetres  ; 
or  to  61-027  cubic  inches,  English. 

A gram  is  the  weight  of  a centimetre  cube  of  distilled 
water  ; at  4°  C.  it  weighs  15-432  grains. 


I Sq. 
Centim 

■< 4 inches. 

Fig.  1. 


INTRODUCTORY. 


27 


52.  English  Weights  and  Measures. — ^Familiarity  with  English  weights 
and  measures  is  assumed,  still  the  following  partieulars  will  most  likely 
be  of  service — one  gallon  of  pure  water  at  a temperature  of  62°  F.  (16*6°  C.) 
weighs  10  pounds  or  160  ounces  or  70,000  grains  ; the  pint,  therefore,  weighs 
20  ounces.  The  measure  termed  a “ fluid  ounce  ''  is  derived  from  the  weight 
of  a pint  of  water.  A fluid  ounce  is  a measure  of  volume,  not  of  weight, 
and  equals  one  twentieth  part  of  a pint.  The  fluid  ounce  bears  the  same 
relation  to  the  avoirdupois  ounce,  as  does  the  cubic  centimetre  to  the  gram. 
A gallon  is  equal  to  277*274  cubic  inches.  An  ounce  avoirdupois  weighs 
437*5  grains. 


CHAPTER  II. 


DESCRIPTION  OF  THE  PRINCIPAL  CHEMICAL  ELEMENTS  AND  THEIR 
INORGANIC  COMPOUNDS. 

53.  Description  of  Elements  and  Compounds. — It  is  intended  in  this 
chapter  to  give  a very  brief  description  of  those  elements  and  their  inorganic 
compounds,  which  are  more  or  less  directly  connected  with  the  chemistry 
of  wheat,  flour,  and  bread,  and  to  which  reference  may  be  made  in  the  latter 
part  of  this  work.  Such  descriptions  as  are  here  given  must  not  be  viewed 
as  being  in  any  way  a substitute  for  a careful  study  of  elementary  chemistry. 
It  is  thought,  however,  that  to  many  readers,  more  particularly  those  who 
may  not  have  the  time  for  such  a systematic  course,  an  account  such  as 
is  to  follow  will  be  found  of  service. 

54.  Hydrogen,  H2. — This  element  is  a gas,  and  is  the  lightest  substance 
known  ; it  is  consequently  selected  as  the  standard  by  which  the  density 
of  other  gases  is  measured.  One  litre  of  hydrogen  at  N.T.P.  weighs  0*0896 
gram.  Hydrogen  has  the  lowest  atomic  weight  of  all  the  elements,  and 
is  therefore  also  selected  as  the  unit  of  the  modern  system  of  atomic  or 
combining  weights.  (For  certain  reasons,  the  atomic  weights  are  some- 
times calculated  to  the  basis  of  16  00  as  the  atomic  weight  of  oxygen.) 
Hydrogen  is  colourless,  odourless,  tasteless,  and  non-poisonous.  It  is  not 
capable  of  supporting  respiration,  and  therefore  animals  placed  therein 
quickly  die  through  lack  of  proper  air  to  breathe.  Hydrogen  is  inflammable 
and  burns  with  a pale  blue  flame  ; it  does  not  support  combustion. 
Hydrogen  is  only  very  slightly  soluble  in  water. 

55.  Oxygen,  O2. — ^This  element  is  a colourless,  odourless,  and  non- 
inflammable  gas.  Its  most  remarkable  feature  is  that  it  supports  combustion 
and  also  respiration.  Bodies  which  burn  in  ordinary  air  do  so  because  that 
substance  is  a mixture  of  oxygen  and  nitrogen ; they  burn  with  much  increased 
brilliancy  in  oxygen.  The  respiration  or  breathing  of  animals  consists  of  a 
removal  of  oxygen  from  the  air,  and  a return  thereto  of  water  vapour  and 
carbon  dioxide  gas  : the  activity  of  oxygen  renders  it  injurious  to  breathe  in 
a pure  state  : in  air,  the  nitrogen  acts  as  a diluting  agent,  without  modifying 
the  essential  characteristics  of  the  gas.  Oxygen  is  soluble  in  water  to 
the  extent  of  three  volumes  of  the  gas  in  one  hundred  volumes  of  water  at 
15°  C.  This  quantity,  though  small,  is  of  vast  importance,  as  it  thus  sup- 
ports the  life  of  fishes,  and  has  also  a most  important  action  on  fermenta- 
tion. Although  oxygen  is  such  an  essential  to  most  forms  of  life,  there  are 
some  of  the  lower  microscopic  organisms  towards  which  it  acts  as  a most 
energetic  poison.  Compounds  produced  by  the  union  of  elements  with 
oxygen  are  termed  “ oxides.’" 

56.  Ozone,  O3. — ^This  body  is  a gaseous  substance  consisting  of  pure 
oxygen,' but  having  a density  of  24  instead  of  16.  This  is  due  to  there  being 
3 atoms  of  the  element  in  the  molecule,  instead  of  2 as  in  ordinary  oxygen. 
Ozone  has  a peculiar  odour  ; and  is  produced  during  the  working  of  a fric- 
tional electric  machine,  when  its  smell  is  recognized.  Traces  of  this  gas 
exist  in  the  air  in  mountainous  districts,  and  by  the  seaside.  By  exposure 


ELEMENTS  AND  INORGANIC  COMPOUNDS. 


29' 


to  a temperature  of  237°  C.  ozone  is  transformed  into  ordinary  oxygen. 
Ozone  is  a powerful  oxidizing  agent,  and  is  inimical  to  the  growth  and 
development  of  germ  life.  Of  recent  years,  ozone  has  been  proposed  as 
a bleaching  agent  for  flour  ; its  employment  for  that  purpose  will  be  dis- 
cussed in  full  at  a later  stage. 

57.  Water,  HsO.—This  most  important  compound  consists  of  two 
volumes  of  hydrogen  united  to  one  volume  of  oxygen,  to  form  two 
volumes  of  water-gas  or  steam.  By  weight,  water  contains  16  parts  of 
oxygen  to  2 of  hydrogen.  Water  in  the  pure  state  is  odourless  and  taste- 
less ; viewed  through  thick  layers  it  has  a blue  colour.  At  temperatures 
below  0°  C.  water  exists  in  the  solid  state  ; on  being  heated,  ice  expands 
until  a temperature  of  0°  C.  is  reached.  At  this  point  the  ice  begins  to 
melt  ; the  temperature  remains  stationary  until  the  whole  of  the  ice  is 
melted,  but  in  order  to  effect  the  change  from  the  solid  to  the  liquid  con- 
dition as  much  heat  is  required  as  would  be  sufficient  to  raise  79  times  the 
weight  of  water  from  0°  to  I°C.  Ice  in  melting  contracts  in  [bulk  ; 10*9 
volumes  of  ice  producing  10  volumes  of  water.  As  the  ice-cold  water  is 
further  heated,  contraction  continues  until  a temperature  of  4°  C.  is  reached  : 
at  this  point  water  is  at  its  maximum  density,  and  any  given  weight  of  it 
occupies  its  minimum  volume.  With  further  application  of  heat  the  water 
expands,  and  also  rises  steadily  in  temperature.  In  metal  vessels  open  to 
the  air,  water  boils  at  a temperature  of  100°  C.  Continued  heating  now 
converts  the  whole  of  the  water  into  steam,  but  does  not  raise  the  tempera- 
ture. The  quantity  of  heat  necessary  to  convert  the  whole  of  the  water 
at  100°  C.  into  steam  at  the  same  temperature  would  raise  537  *2  times  the 
weight  of  water  from  0°  to  1°C.  Steam  in  being  further  heated  expands, 
and  may  have  its  temperature  raised  indefinitely  ; steam  follows  the  same 
law  of  expansion  on  increase  of  temperature  as  do  other  gases.  Steam,  on 
being  cooled,  passes  through  a series  of  changes  which  are  the  exact  con- 
verse of  those  just  described.  At  all  temperatures  water  gives  off  vapour, 
but  with  much  greater  rapidity  as  the  temperature  approaches  the  boiling 
point.  This  vapour  exerts  a definite  pressure,  the  pressure  increasing 
steadily  with  the  temperature  ; at  the  boiling  point,  the  pressure  exerted 
by  the  vapour  of  Avater  is  exactly  equal  to  that  of  the  atmosphere  ; conse- 
quently, if  the  atmospheric  pressure  be  diminished,  the  boiling  point  of 
water,  and  also  that  of  all  other  liquids,  is  lowered.  Advantage  is  taken 
of  this  property  in  many  operations  in  the  arts  ; thus,  in  driving  off  the 
water  from  sugar  solutions,  as  in  the  preparation  of  malt  extract,  the  boiling 
is  effected  in  a vacuum,  and  so  the  temperature  prevented  from  rising  to 
any  great  height.  On  the  other  hand,  by  subjecting  water  to  pressure,  its 
boiling  point  may  be  raised  to  any  temperature  attainable,  the  only  limit 
being  the  capacity,  for  resisting  the  pressure,  of  the  material  of  the  vessel. 
The  tubes  of  steam  ovens  are  constructed  on  this  principle — a certain  quan- 
tity of  water  is  sealed  up  in  them,  which,  on  being  heated,  is  converted 
into  steam  having  a sufficiently  high  temperature  to  effect  the  baking  of 
bread.  The  boiling  point  of  water  also  depends  on  any  substances  it  may 
have  in  solution.  Salt  and  other  non-volatile  bodies  raise  the  temperature 
of  the  boiling  point,  but  do  not  affect  that  of  the  steam  produced,  which 
immediately  falls  to  100°  C.  Admixture  of  volatile  bodies  lowers  the  boiling 
point  ; thus,  a mixture  of  water  and  alcohol  boils  at  a temperature  below 
100°  C.  until  the  whole  of  the  alcohol  has  been  expelled. 

58.  Solvent  Power  of  Water. — ^Water  is,  of  ail  bodies,  pre-eminently 
the  solvent  in  nature.  As  a result  of  this  property,  water  is  never  found 
in  a state  of  purity  in  nature.  Even  rain  is  found  to  have  dissolved  out 


30 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


traces  of  solid  matter  that  were  suspended  in  the  air,  while  river  and  spring 
water  is  always  more  or  less  impure  from  saline  and  other  matter  dissolved 
from  the  soil  and  rocky  strata  from  whence  it  is  obtained.  In  addition  to 
the  solid  matter  there  is  also  invariably  more  or  less  gas  held  in  solution 
in  natural  waters.  A further  account  of  natural  waters,  having  particular 
reference  to  their  fitness  for  bread- making,  is  given  in  a future  chapter. 
For  chemical  purposes  all  such  water  is  purified  by  distillation,  that  is,  it 
is  converted  into  steam,  and  re -condensed  ; the  solid  impurities  then  remain 
behind.  This  treatment  does  not,  however,  free  the  water  from  gases  or 
from  volatile  impurities.  For  certain  purposes,  where  rigidly  pure  water 
is  a necessity,  special  modes  of  preparation  have  to  be  adopted  ; these 
will  be  described  in  detail  hereafter. 

59.  Hydrogen  Peroxide,  H2O2. — ^In  addition  to  water,  there  is  also 
known  a higher  oxide  of  hydrogen,  to  which  the  name  of  hydrogen  per- 
oxide is  given.  In  the  pure  state,  hydrogen  peroxide  is  a colourless,  odour- 
less, and  somewhat  sirupy  liquid  having  a peculiar  metallic  taste.  It  is 
extremely  unstable,  readily  giving  off  oxygen,  and  leaving  a residue  of  pure 
water.  When  diluted  with  water,  hydrogen  peroxide  is  much  more  stable, 
and  this  stability  is  increased  by  the  addition  of  a small  quantity  of 
acid.  But  on  heating,  this  solution  is  changed  into  water  and  free 
oxygen.  This  readiness  to  give  up  oxygen  causes  the  peroxide  to  be  a 
powerful  oxidizing  agent,  and  as  such  it  possesses  active  bleaching  properties. 
The  semi-molecule  of  hydrogen  peroxide,  HO,  enters  into  the  composition 
of  a large  number  of  compounds,  and  has  received  a specific  name,  hydroxyl. 

60.  Chlorine,  CL. — This  element  is,  at  ordinary  temperatures,  a gas 
of  a greenish  yellow  colour,  with  a most  pungent,  acrid,  and  suffocating 
odour  and  taste.  The  presence  of  comparatively  small  quantities  renders 
air  irrespirable.  Chlorine  is  non-inflammable  ; but,  to  a limited  extent, 
supports  combustion.  Hydrogen  burns  in  it  readily,  but  carbon  is  incap- 
able of  direct  combination  with  chlorine.  Chlorine  does  not  exist  in  the 
free  state  in  nature  ; it  has  so  great  an  attraction  for  hydrogen  that  it 
slowly  decomposes  water,  combining  with  the  hydrogen  and  liberating 
oxygen  in  the  free  state.  Water  dissolves  2*368  volumes  of  chlorine  at 
15°  C.  ; the  solution  has  a powerful  bleaching  action  on  vegetable  colours, 
and  also  is  a most  efficient  disinfectant.  Chlorine  forms  compounds,  termed 

chlorides,’'  with  all  other  elements. 

61.  Hydrochloric  Acid,  HCl. — ^This,  the  only  known  compound  of  hydro- 
gen and  chlorine,  is  a gaseous  body.  Hydrochloric  acid  gas  is  colourless, 
fumes  on  coming  in  contact  with  moist  air,  has  a most  pungent  smell,  and 
is  neither  inflammable  nor  a supporter  of  combustion.  One  volume  of 
hydrogen  unites  with  one  volume  of  chlorine  to  produce  two  volumes  of 
hydrochloric  acid  gas.  The  gas  dissolves  readily  in  water,  one  volume  of 
which  at  15°  C.  holds  in  solution  454  volumes  of  the  gas.  The  concentrated 
solution  fumes  on  exposure  to  air,  and  smells  strongly  of  the  gas  ; it  has 
an  extremely  sour  taste,  and  turns  litmus  solution  red.  The  commercial 
solution  has  a specific  gravity  of  about  1 *16,  and  contains  about  33  per  cent, 
(one  third)  by  weight  of  hydrochloric  acid.  Hydrochloric  acid  attacks 
many  of  the  metals,  forming  chlorides,  with  the  evolution  of  hydrogen. 
Hydrochloric  acid  and  the  bases  when  placed  in  contact  form  the  salts 
known  as  chlorides.  Hydrochloric  acid  and  the  chlorides  may  be  recognised 
when  in  solution  by  their  giving  a curdy  white  precipitate  on  the  addition 
of  dilute  nitric  acid,  and  nitrate  of  silver  solution. 

62.  Chlorides. — Common  salt,  or  sodium  chloride,  NaCl,  is  the  mo  ;t 


ELEMENTS  AND  INORGANIC  COMPOUNDS. 


31 


important  of  the  chlorides,  and  is  largely  used  as  an  antiseptic  or  preventa- 
tive of  putrefaction  ; its  effect  during  fermentation  of  dough  will  be 
discussed  hereafter.  Other  chlorides,  as  calcium  chloride,  CaCU,  will  be 
referred  to  as  occasion  arises. 

63.  Bleaching  Powder,  or  Chloride  of  Lime,  CaOCU. — This  body  is 
produced  by  the  union  of  lime  (calcium  oxide)  with  chlorine.  The  addition 
of  almost  any  acid,  even  carbon  dioxide,  is  sufficient  to  effect  its  decomposi- 
tion, liberating  free  chlorine.  Chloride  of  lime  is  consequently  largely  used 
for  disinfecting  and  bleaching  purposes. 

64.  Carbon,  C. — This  element  is  only  known  in  the  solid  state,  being 
incapable  of  liquefaction  or  vaporisation  at  the  highest  temperatures  at 
our  command  (except  possibly  at  the  highest  temperatures  of  the  electric 
arc).  It  exists  in  nature,  uncombined  with  other  elements,  in  two  forms 
or  varieties  most  strikingly  different  from  each  other.  One  of  these  consti- 
tutes the  gem  known  as  the  diamond,  the  other  is  graphite,  or  black  lead. 
Both  these  bodies  are  almost  pure  carbon.  Carbon  also  occurs  plentifully 
as  a constituent  of  animal  and  vegetable  substances,  as  flesh,  bones,  fat, 
wood,  leaves,  seeds,  and  the  almost  numberless  bodies  that  may  be  obtained 
from  them.  Limestone,  marble,  and  chalk  rocks  contain  a large  percentage 
of  carbon  ; so  also  does  coal,  which  is  essentially  fossilised  wood.  From 
flesh,  bones,  wood,  and  many  other  substances,  carbon  may  be  obtained 
by  heating  them  to  redness  in  a closed  vessel  : this  form  of  carbon  is  termed 
“ charcoal,”  that  from  bones  being  “ animal,”  and  that  from  wood  ‘‘  vege- 
table charcoal.”  Carbon  prepared  in  this  manner,  or  charcoal,  is  a black 
substance.  The  operation  of  thus  heating  a substance  in  a closed  vessel  to 
a temperature  sufficiently  high  to  effect  its  decomposition  into  volatile 
liquid  and  gaseous  products,  with  usually,  as  in  this  case,  a non-volatile 
residue,  is  termed  “ destructive  distillation.”  All  forms  of  carbon  are  in- 
flammable. When  burned  with  an  insufficient  supply  of  oxygen,  carbon 
monoxide,  CO,  is  produced  ; with  excess  of  oxygen,  carbon  dioxide,  or 
CO2,  is  formed.  Charcoal  possesses  a most  remarkable  property  of  absorb- 
ing and  condensing  gases  within  its  pores  ; thus,  freshly-burnt  wood  char- 
coal is  capable  of  absorbing  about  ninety  times  its  volume  of  ammonia  gas. 
Charcoal  also  absorbs  considerable  quantities  of  oxygen  ; and  among  other 
gases,  those  evolved  during  the  putrefaction  of  animal  and  vegetable  bodies. 
The  gases  resulting  from  putrefaction  are  largely  composed  of  carbon  and 
hydrogen,  and,  when  thus  brought  by  their  absorption  within  the  charcoal 
so  closely  in  contact  with  oxygen,  are  rapidly  burned  or  oxidised  to  carbon 
dioxide,  water,  and  more  or  less  of  other  inodorous  and  innocuous  substances. 
Charcoal  thus  acts  as  a remedy  for  bad  smells,  and  acts  not  by  masking 
them  by  a more  powerful  odour,  but  by  absorption  of  the  deleterious  vapours, 
and  their  conversion  into  harmless  products.  In  this  way  charcoal  is  also 
capable  of  removing  evil  smells  from  water  ; for  instance,  water  from  a 
stagnant  pond  on  being  shaken  up  with  charcoal  loses  its  disagreeable  odour. 
Not  only  does  charcoal  act  as  an  absorbent  of  gases,  but  it  also  removes 
many  colouring  matters  from  solution  ; thus,  a syrup  of  dark  brown  sugar 
on  being  shaken  up  with  animal  charcoal,  and  then  filtered,  may  be  made 
almost  colourless.  These  properties  of  charcoal  have  led  to  its  finding  much 
favour  as  a filtering  medium  for  the  purification  of  water  ; for  this  purpose 
it  is,  when  fresh,  of  great  efficacy,  but  after  a time  loses  its  activity  by  be- 
coming saturated  with  the  bodies  it  is  intended  to  remove.  All  filters 
require  from  time  to  time  to  be  taken  apart,  and  the  filtering  medium  re- 
moved and  replaced  by  some  fresh  and  pure  material.  Charcoal  may  be 
renovated  by  being  heated  to  redness  in  a closed  vessel.  With  these 
precautions,  charcoal  forms  one  of  the  best  of  filtering  agents  ; but  without 


32 


THE  TECHNOLOGY  OF  BREAD-MAKING 


attention  to  continuous  cleaning,  filters,  so  far  from  purifying  water,  become 
positive  sources  of  the  most  serious  , and  dangerous  impurities.  Charcoal 
is  frequently  used  in  the  laboratory  for  decolourising  purposes. 

65.  Carbon  Monoxide,  CO. — This  compound  is  a colourless,  odourless 
and  exceedingly  poisonous  gas.  It  is  formed  when  carbon  dioxide  gas 
passes  over  or  through  red-hot  charcoal,  as  it  frequently  does  in  a clear 
coke  or  charcoal  fire.  The  carbon  monoxide  thus  produced  burns  with  a 
blue  flame  on  the  surface  of  the  Are.  Carbon  monoxide  is  also  formed, 
together  with  free  hydrogen,  when  steam  is  passed  through  a red-hot  carbon 
mass,  such  as  a Are  of  burning  coke.  The  gas  is  inflammable,  and  in  burning 
yields  carbon  dioxide.  Carbon  monoxide  has  no  action  on  lime-water. 

66.  Carbon  Dioxide,  CO2. — This  gas  plays  a most  important  part  in 
the  chemistry  of  bread-making.  It  is  colourless,  has  a sweetish  taste,  and 
peculiarly  brisk  and  pungent  odour.  As  carbon  dioxide  is  an  essential 
constituent  of  aerated  waters,  its  taste  and  smell  are  familiar,  being  those 
perceived  on  opening  and  tasting  the  contents  of  a bottle  of  soda-water. 
Carbon  dioxide  is  neither  inflammable,  nor  under  ordinary  circumstances 
a supporter  of  combustion.  The  gas  is  poisonous  to  breathe,  but  may 
be  taken  into  the  stomach  without  injury.  Liquids  containing  carbon 
dioxide  gas  in  solution  are  marked  by  a pleasant  brisk  flavour.  Carbon 
dioxide  has  a density  of  22,  and  is  1*527  times  as  heavy  as  ordinary  air. 
In  the  absence  of  air  currents,  it  consequently  has  a tendency  to  remain  a 
considerable  time  in  a layer  on  the  surface  of  liquids  from  which  it  is  being 
evolved,  particularly  when  they  are  in  somewhat  confined  spaces.  Carbon 
dioxide  is  soluble  in  about  its  own  volume  of  water  ; as  has  already  been 
explained  (paragraph  45),  when  measured  by  volume  the  solubility  is 
independent  of  the  pressure  to  which  the  gas  is  subject.  Concentrated 
solutions  of  carbon  dioxide  gas  in  water  are  prepared  by  pumping  the  gas 
under  pressure  (some  10  or  12  atmospheres)  into  a strong  vessel,  in  which 
it  is  agitated  with  water.  The  solution  thus  obtained  is  permanent  under 
pressure,  but  on  its  relaxation  the  carbon  dioxide  is  again  liberated  in  the 
gaseous  state.  Carbon  dioxide  may  be  obtained  in  a variety  of  ways  ; the 
simplest  is  by  the  burning  of  carbon,  or  organic  bodies  containing  carbon 
in  air  or  oxygen — 

C + O2  = CO2. 

Carbon.  Oxygen’  Carbon  Dioxide. 

It  is  also  produced  when  chalk,  limestone,  or  marble  (calcium  carbonate) 
is  heated  to  full  redness — 

CaCOa  = CaO  + CO2. 

Caloiuni  Carbonate.  Calcium  Oxide  (Lime).  Carbon  Dioxide. 

Likewise,  by  gently  heating  sodium  bicarbonate  or  ammonium  carbonate — 


2NaHC03  = 

Na2C03 

+ 

H2O 

+ CO2. 

Sodium  Bicarbonate. 

Sodium  Carbonate. 

Water. 

Carbon  Dioxide. 

(NH4)2C03  - 

Ammonium  Carbonate. 

2NH3 

Ammonia. 

+ 

H2O 

Water. 

+ CO2. 

Carbon  Dioxide. 

Another  method  of  obtaining  carbon  dioxide  is  by  treating  any  carbonate 
with  an  acid  : the  following  equations  represent  a few  of  the  principal  of 
such  reactions — 


CaC03 

+ 

2HC1  = 

CaCL  + 

H2O 

-}-  CO2. 

Calcium  Carbonate. 

Hydrochloric  Acid. 

Calcium  Chloride. 

Water. 

Carbon  Dioxid  e. 

*CaC03 

+ 

H2SO4  = 

CaSO,  + 

H2O 

+ CO2. 

Calcium  Carbonate. 

Sulphuric  Acid. 

Calcium  Sulphate. 

Water. 

Carbon  Dioxide. 

Na2C03 

2HC1  = 

2N‘aCl  + 

H2O 

+ CO2. 

Sodium  Carbonate. 

Hydrochloric  Acid. 

Sodium  Chloride 
(Common  Salt). 

Water. 

Carbon  Dioxide. 

ELEMENTS  AND  INORGANIC  COMPOUNDS. 


33 


2NaHC03  + H2C4H4O6  = Na2C4H406+  2H2O  + CO2. 

Sodium  Bicarbonate.  Tartaric  Acid,  Sodium  Tartrate.  Water.  Carbon  Dioxide. 

Carbon  dioxide  is  also  evolved  during  alcoholic  fermentation,  and  the 
putrefaction  and  decay  of  organic  bodies.  In  addition,  carbon  dioxide  is 
produced  during  the  respiration  of  animals,  and  is  an  important  constituent 
of  the  exhaled  breath.  An  aqueous  solution  of  carbon  dioxide  gas  changes 
the  colour  of  litmus  solution  from  full  blue  to  a port  wine  tint  ; such  a solu- 
tion has  feebly  acid  properties  and  forms  with  bases  the  salts  termed  car- 
bonates. The  solution  in  water  may  be  viewed  as  carbonic  acid,  H2CO3  ; 
hence  the  gas  is  frequently  called  carbonic  anhydride.  Formerly  the  term 
acid  was  applied,  by  some  chemists,  indifferently  to  the  anhydrides  and 
their  compounds  with  water  ; carbon  dioxide  then  received  the  name  of 
“ carbonic  acid  gas,"'  by  which  it  is  still  popularly  known.  Modern  defini- 
tions of  an  acid  preclude  this  name  being  now  correctly  applied  to  what 
are  properly  termed  anhydrides. 

67.  Carbonates. — ^With  the  exception  of  those  of  the  alkalies,  all  car- 
bonates are  insoluble  in  water  ; many  are,  however,  dissolved  by  water 
containing  carbon  dioxide  in  solution.  The  most  interesting  example  of 
this  is  the  solution  of  considerable  quantities  of  carbonate  of  lime  in  natural 
waters  obtained  from  the  chalk  and  other  limestone  deposits.  Such  waters, 
although  perfectly  clear,  become  turbid  on  being  boiled  from  fifteen  to 
thirty  minutes  : the  boiling  drives  off  the  carbon  dioxide,  and  the  calcium 
carbonate  is  precipitated  in  the  insoluble  state.  The  formation  of  car- 
bonates is  exemplified  by  the  passage  of  carbon  dioxide  gas  into  lime  water, 
i.e.,  a solution  of  lime  in  water,  CaH202  ; the  insoluble  calcium  carbonate,  or 
carbonate  of  lime,  is  produced,  and  turns  the  clear  solution  milky.  This 
forms  a useful  and  convenient  test  for  the  presence  of  carbon  dioxide  in 
any  mixture  of  gases.  Most  carbonates  are  easily  decomposed  by  the 
addition  of  an  acid,  with  the  formation  of  the  corresponding  salt  of  the 
acid  used.  Several  instances  of  this  action  have  been  given  when  describing 
methods  for  the  production  of  carbon  dioxide.  The  acid-  or  bi-carbonates 
have  one-half  only  of  the  hydrogen  replaced  by  a metal ; they  may  be  pro- 
duced by  passing  carbon  dioxide  gas  to  excess  through  a solution  of  the 
normal  carbonates  of  the  alkalies.  The  bicarbonates  are  readily  decomposed 
by  heat  into  normal  carbonates,  free  carbon  dioxide,  and  water. 

68.  Compounds  of  Carbon  with  Hydrogen. — ^These  are  exceedingly 
numerous  ; an  account  of  some  of  those  of  most  importance  will  be  given 
when  describing  the  organic  bodies  more  particularly  associated  with  our 
subject.  As  a group,  they  are  termed  “ hydrides  of  carbon." 

69.  Nitrogen,  N2. — ^This  gas  constitutes  about  four-fifths,  by  volume, 
of  the  atmosphere  ; it  is  also  a constituent  of  ammonia,  of  nitric  acid 
and  its  salts,  and  of  many  animal  and  vegetable  substances.  Nitrogen  is 
colourless,  odourless,  tasteless,  non-infiammable,  and  a non-supporter  of 
combustion.  It  does  not  readily  enter  into  combination  with  other 
elements,  but  may  be  caused  to  combine  with  oxygen  by  passing  a sparking 
or  flaming  discharge  through  a mixture  of  the  two.  In  the  free  state 
nitrogen  is  marked  rather  by  its  neutral  qualities  than  by  any  positive 
characteristics.  In  the  uncombined  state  its  principal  function  is  that  of  a 
diluting  agent  in  the  atmosphere.  Although  1 ot  an  active  element,  nitro- 
gen forms  an  extensive  series  of  compounds. 

70.  The  Atmosphere. — ^It  has  already  been  stated  that  the  atmosphere 
consists  essentially  of  oxygen  and  nitrogen  ; these  gases  are  not  united 
in  any  way,  but  simply  form  a mechanical  mixture.  In  addition  to  the 

D 


34 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


nitrogen  and  oxygen,  air  contains  small  quantities  of  carbon  dioxide,  water 
vapour,  and  traces  of  other  substances.  Subjoined  is  a table  showing  its 
average  composition  : — 


Oxygen,  O2  • . 

. . 20-61 

Nitrogen,  N2.  . 

. . 77-95 

Carbon  Dioxide,  CO  2 

0-04 

Aqueous  Vapour,  H2O 

Nitric  Acid,  HNO3  • • 

1-40 

Ammonia,  NH3 

. . 1 Traces. 

Hydrides  of  Carbon 

. 

In  f Sulphuretted  Hydrogen,  SH2 

. . 1 

townsjSulphur  Dioxide,  SO2 

. . j ” 

Air,  freed  from  moisture  and  carbon  dioxide, 
percentage  of  nitrogen  and  oxygen : — 

contains  the  following 

By  Measure.  By  AVeight. 

Nitrogen  . . . . . . . . 79‘19 

76-99 

Oxygen  20-81 

23-01 

100-00 

100-00 

Argon,  and  the  other  members  of  the  allied  group  of  elements,  are  here 
included  with  the  nitrogen.  They  altogether  amount  to  about  0*94  per 
cent,  of  atmospheric  air. 

In  addition  to  the  bodies  already  mentioned,  air  in  most  localities  con- 
tains germs  of  microscopic  organisms. 

71.  Ammonia,  NH3. — ^Traces  of  this  gas,  either  in  the  free  state  or  as 
salts,  are  found  both  in  air  and  in  water.  Its  great  natural  source  is  the 
decomposition  of  animal  and  vegetable  substances  which  contain  nitrogen 
as  a constituent.  In  this  way,  ammonia  is  continually  being  formed  in 
nature  by  the  decay  of  refuse  nitrogenous  matter,  such  as  the  urine  and 
excreta  of  animals,  ^nd  other  bodies.  Many  nitrogenous  vegetable  and 
animal  substances  also  evolve  ammonia  on  being  strongly  heated  ; among 
these  is  coal,  which  thus  forms  the  principal  source  from  which  ammonia 
is  now  derived.  Ammonia  is  a colourless  gas,  with  a most  pungent  and 
characteristic  odour  : in  the  concentrated  state  the  gas  acts  as  an  irritant 
poison,  but  when  diluted  with  air  possesses  a smell  rather  pleasant  than 
otherwise.  Ammonia  does  not  support  combustion,  and  at  ordinary  tem- 
peratures does  not  burn  in  air.  The  gas  is  very  soluble  in  water  ; the 
solution  has  the  odour  of  the  gas,  and  constitutes  what  is  commonly  known 
as  liquor  ammonice  ; this  must  not  be  confused  with  the  gas  condensed  by 
pressure  in  the  absence  of  water,  and  which  is  termed  “ liquid  ammonia.'’. 
Ammonia  acts  as  a powerful  alkali,  neutralising  the  strongest  acids,  and 
restoring  the  blue  colour  to  reddened  litmus. 

72.  Ammonium  Salts. — On  the  addition  of  an  acid,  such  as  either  sul- 
phuric or  hydrochloric  acid,  to  ammonia,  the  odour  disappears,  and  the 
acid,  as  above  stated,  is  found  to  be  completely  neutralised.  The  reaction 
may  be  expressed  thus  : — 


NH3 

+ 

HCl  = 

NH4CI. 

Ammonia. 

Hydrochloric  Acid. 

Ammonium  Chloride. 

2NH3 

+ 

H2SO4  = 

(NH4)2S04. 

Ammonia. 

Sulphuric  Acid. 

Ammonium  Sulphate. 

On  comparing,  in  each  case,  the  formula  of  the  resulting  compound 
Avith  that  of  the  acid,  it  will  be  seen  that  the  group  NH4  replaces  the  hydrogen 


ELEMENTS  AND  INORGANIC  COMPOUNDS. 


35 


of  the  acid.  This  compound,  NH4,  cannot  exist  in  the  free  state,  but  occurs 
in  a number  of  chemical  compounds,  and  can  be  transferred  from  one  to 
another  without  undergoing  decomposition.  It  is  consequently  viewed  as 
a compound  radical,  and  has  received  the  name  “ Ammonium."’  The 
solution  of  ammonia  in  water  may  then  be  represented  as  ammonium 
hydroxide,  NH4HO  ; this  body,  which  is  alkaline  to  litmus,  is  then  seen 
to  be  analogous  to  sodium  hydroxide,  NaHO,  the  ammonium  occupying 
a corresponding  place  to  the  sodium.  This  is  seen  the  more  clearly  when  a 
comparison  is  instituted  between  the  action  of  the  same  acid  upon  each  : — 

NH4HO  + HCl  = NH4CI  + H2O. 

Ammonium  Hydroxide.  Hydrocliloric  Acid.  Ammonium  Chloride.  Water. 

NaHO  + HCl  = NaCl  + H2O. 

Sodium  Hydroxide.  Hydrochloric  Acid.  Sodium  Chloride.  Water. 

Ammonium  is  often  represented  by  the  symbol  “ Am.”  instead  of  NH4. 
The  stronger  bases,  as  lime,  CaO,  or  soda,  NaHO,  decompose  ammonium 
salts  with  the  liberation  of  ammonia  : — 


NH4CI  + NaHO  = NaCl  + NH3  + H2O. 

Ammonium  Chloride.  Sodium  Hydroxide.  Sodium  Chloride.  Ammonia.  Water. 

All  ammonium  salts  volatise  on  being  heated,  leaving  no  residue,  unless 
the  acid  be  non-volatile,  in  which  case  the  acid  remains  behind. 

73.  Oxides  and  Acids  of  Nitrogen. — No  less  than  five  distinct  compounds 
of  nitrogen  with  oxygen  are  known.  The  following  is  a list  of  their  names 
and  formulae  — 


Nitrous  Oxide  . . . . . . . . . . . . N2O 

Nitric  Oxide  . . . . . . . . . . NO  (or  N2O2) 

Nitrogen  Trioxide,  Nitrous  Anhydride  . . . . N2O3 

Nitrogen  Peroxide  . . . . . . . . NO2  or  N2O4 

Nitrogen  Pentoxide,  Nitric  Anhydride  . . . . N2O5 


Two  of  these  oxides,  the  trioxide  and  pentoxide,  form  acids  with  water — 
the  acids  being  nitric  acid,  HNO3,  and  nitrous  acid,  HNO2. 

The  first  and  last  of  this  series  of  oxides  have  little  or  no  connection 
with  our  present  subject,  but  the  intermediate  three  are  of  much  interest 
and  importance  as  being  the  agents  of  a successful  flour  bleaching  process. 
Eor  this  reason  a brief  description  of  their  properties  is  necessary. 

74.  Nitric  Oxide,  NO. — ^Formerly,  N2O2  was  considered  possibly  to 
represent  the  constitution  of  the  molecule  of  this  body,  but  from  its  density, 
the  molecule  must  be  regarded  as  consisting  of  NO.  The  N2O2  formula 
is  given  above  in  brackets,  in  order  to  show^  the  relationship  in  com- 
position between  this  and  the  other  oxides  of  nitrogen.  When  nitric  acid 
is  added  to  metallic  copper,  an  abundance  of  ruddy  fumes  is  evolved  ; but 
if  the  operation  be  conducted  in  a flask  fitted  in  the  ordinary  way  with  a 
thistle  funnel  and  leading  tube,  the  coloured  fumes  are  seen  to  be  sw^ept 
out  of  the  flask,  which  soon  becomes  filled  with  a colourless  gas,  wdiich  may 
be  collected  over  w^ater  in  the  pneumatic  trough.  This  colourless  gas 
is  nitric  oxide.  If  a gas  jar  be  partly  filled  with  nitric  oxide  and  then 
oxygen  admitted  bubble  by  bubble,  a red  colour  is  seen  to  develop  with  each 
introduction.  This  rapidly  disappears,  and  simultaneously  the  water 
rises  in  the  jar.  By  careful  addition  of  oxygen  the  wiiole  of  the  gas  (assum- 
ing its  purity)  may  be  thus  rendered  soluble.  Nitric  oxide  is  only  very 
slightly  soluble  in  water,  and  possesses  the  property  of  immediately  com- 
bining with  free  oxygen  to  produce  nitrogen  peroxide,  NO2.  Nitrogen 
peroxide  is  a ruddy  coloured  gas,  and  is  very  soluble  in  w ater.  A convenient 


36 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


method  of  preparing  nitric  oxide  consists  of  allowing  nitric  acid  to  drop 
into  a solution  of  ferrous  sulphate,  and  at  the  same  time  passing  a current 
of  air  through  the  solution.  The  air  comes  over,  carrying  with  it  the  gas ; 
the  proportion  of  the  latter  may  be  regulated  by  adjusting  the  rate  at 
which  the  nitric  acid  is  allowed  to  drop  into  the  solution.  The  following 
is  the  nature  of  the  chemical  change  : — 

8HNO3  + 6FeS04  = 2Fe2(S04)3  + Fe2(N03)6  + 2NO  + 4H2O. 

Nitric  Acid.  Ferrous  Sulphate.  Ferric  Sulphate.  Ferric  Nitrate.  Nitric  Oxide.  Water. 

In  the  presence  of  air,  the  nitric  oxide  is  immediately  converted  into  the 
peroxide. 

75.  Nitrogen  Peroxide,  NO2. — ^At  a temperature  of  26-7°  C.,  this  gas 
has  a density  which  indicates  that  about  80  per  cent,  of  its  molecules  con- 
sist of  N2O4,  the  remaining  ones  being  composed  of  NO2.  As  the  tempera- 
ture of  the  gas  is  raised,  the  density  diminishes,  and  at  140*0°  is  23*00, 
which  corresponds  to  the  whole  of  the  gas  being  dissociated  with  NO2  mole- 
cules. Nitrogen  peroxide  is  absorbed  and  decomposed  by  water  ; in  the 
presence  of  ve^y  small  quantities  of  the  latter  nitrous  and  nit^-ic  acids  are 
thus  formed  : — 

N2O4  + H2O  = HNO3  + HNO2 

Nitrogen  Peroxide.  Water.  Nitric  Acid.  Nitrous  Acid. 

At  ordinary  temperatures,  and  with  w^ater  in  excess,  nitric  acid  and 
nitric  oxide  are  produced  thus  : — 

3NO2  + H2O  = 2HNO3  + NO. 

Nitrogen  Peroxide.  Water.  Nitric  Acid.  Nitric  Oxide. 

From  the  ease  wdth  wLich  nitrogen  peroxide  loses  an  atom  of  oxygen 
and  becomes  nitric  oxide,  it  is  a powerful  oxidising  agent.  Its  efficiency 
as  such  is  greatly  increased  by  the  property  possessed  by  nitric  oxide 
of  at  once  combining  with  free  oxygen  and  again  producing  nitrogen  per- 
oxide. In  this  way  a very  small  quantity  of  nitrogen  peroxide,  by  its  succes- 
sive reductions  and  oxidations,  may  act  as  a carrier  of  oxygen  to  a relatively 
large  quantity  of  oxidisable  material. 

76.  Nitrogen  Trioxide,  N2O3. — Nitrogen  tri oxide  is  a very  unstable 
compound  which  can  only  exist  at  low  temperatures,  and  readily  decomposes 
into  a mixture  of  nitric  oxide  and  nitrogen  peroxide.  With  water  it  forms 
nitrous  acid,  HNO2,  and  this  in  turn  yields  salts  known  as  nitrites.  These 
bodies  are  fairly  stable,  and  potassium  nitrite,  KNO2,  is  an  example.  Nitrites 
are  found  in  many  drinking  waters  as  an  intermediate  product  in  the  oxida- 
tion to  nitrates  of  nitrogenous  matter  that  may  have  been  present. 

77.  Nitric  Acid,  HNO3. — This  is  by  far  the  most  important  oxy -compound 
of  nitrogen.  Its  usual  source  in  nature  is  the  oxidation  of  animal  matter  in 
the  soil.  The  nitric  acid  thus  produced  is  found  in  combination  with  some 
base,  usually  as  potassium  or  calcium  nitrate.  Pure  nitric  acid  is  a colourless 
fuming  liquid  ; commonly,  how^ever,  the  acid  is  of  a slightly  yellow  tint, 
from  the  presence  of  some  of  the  low^er  oxides  of  nitrogen.  The  pure  acid 
lias  a specific  gravity  of  1*52,  and  mixes  with  water  in  all  proportions. 
Nitric  acid  is  a most  pow^erful  oxidising  agent,  and  attacks  most  animal  and 
vegetable  tissues  w4th  great  vigour.  It  also  freely  dissolves  most  of  the 
metals,  forming  nitrates.  Gold  and  platinum  are  not  affected  by  this  acid 
wdien  pure,  but  are  dissolved  with  the  formation  of  chlorides  by  a mixture 
of  nitric  w'ith  hydrochloric  acid.  Reducing  agents  convert  nitric  acid  into 
nitrous  acid,  or  some  one  or  more  of  the  oxides  of  nitrogen  containing  less 
oxygen.  Under  favourable  circumstances,  nitric  acid  may  even  be  reduced 
to  ammonia  ; that  is,  the  w hole  of  its  oxygen  may  be  removed,  and  its  place 
occupied  by  hydrogen. 


ELEMENTS  AND  INORGANIC  COMPOUNDS.  37 

78.  Nitrates. — ^The  principal  of  these  is  potassium  nitrate,  KNO3.  Like 
nitric  acid,  the  nitrates  are  powerful  oxidising  agents. 

79.  Sulphur,  S2. — This  element,  in  its  common  form,  is  a brittle  yellow 
solid,  which  burns  in  air  or  oxygen  with  the  formation  of  sulphur  dioxide, 
SO2.  The  principal  interest  of  sulphur,  in  connection  with  our  present  sub- 
ject, lies  in  its  compounds.  In  addition  to  its  occurrence  in  many  inorganic 
bodies,  sulphur  is  one  of  the  constituents  of  albumin  and  other  animal  and 
vegetable  substances. 

80.  Sulphuretted  Hydrogen,  SH2. — ^This  body  is  a colourless  gas,  having 
a most  disgusting  odour,  resembling  that  of  rotten  eggs  ; the  gas  is  soluble 
in  water,  which  at  15°  C.  dissolves  3*23  volumes  of  sulphuretted  hydrogen. 
During  the  decomposition  of  substances,  either  of  animal  or  vegetable 
origin,  containing  sulphur,  sulphuretted  hydrogen  is  one  of  the  bodies 
evolved  ; it  is  from  the  presence  of  this  gas  that  rotten  eggs  acquire  their 
characteristic  odour.  Sulphuretted  hydrogen  is  inflammable,  and  produces 
water  and  sulphur  dioxide  by  its  combustion.  Moist  sulphuretted  hydro- 
gen undergoes,  in  the  presence  of  oxygen,  slow  oxidation,  with  the  formation 
of  water  and  deposition  of  free  sulphur  : — 

2H2S  + 02  = 82+  2H2O. 

Sulphuretted  Hydrogen.  Oxgyen.  Sulphur.  Water. 

81.  Sulphur  Dioxide,  SO2. — This  gas  is  produced  by  the  combustion 
of  sulphur  in  either  air  or  oxygen  : it  is  colourless,  has  a pungent  odour, 
recognised  as  that  of  burning  sulphur  ; is  neither  inflammable  nor  a sup- 
porter of  combustion.  Sulphur  dioxide  is  soluble  in  water,  which  at  a 
temperature  of  15°  C.  dissolves  47  volumes  of  the  gas  ; the  solution  thus 
formed  tastes  and  smells  of  the  gas,  it  reddens  and  Anally  bleaches  a solu- 
tion of  litmus.  Sulphur  dioxide  is  one  of  the  most  powerful  antiseptics 
known.  The  gas  is  easily  condensed  to  the  liquid  state  by  either  cold  or 
pressure.  Liquid  sulphur  dioxide  is  supplied  commercially  in  syphons, 
similar  to  those  used  for  soda  water. 

82.  Sulphurous  Acid,  H2SO3,  and  the  Sulphites. — Sulphur  dioxide  when 
dissolved  in  water  produces  a somewhat  unstable  acid,  H2SO3.  The  sul- 
phites, or  salts  of  this  acid,  are  mostly  insoluble  in  water,  the  principal 
exceptions  being  sodium  sulphite,  Na2S03,  and  potassium  sulphite.  In 
addition  to  the  normal  sulphites,  acid  or  bisulphites  occur  ; these  may  be 
produced  by  passing  excess  of  sulphur  dioxide  into  a solution  of  the  normal 
salts.  The  bisulphites  readily  evolve  sulphur  dioxide  on  being  heated. 
Calcium  sulphite  is  insoluble  in  water,  but  dissolves  in  a solution  of  sul- 
phurous acid,  forming  calcium  bisulphite,  or,  as  commonly  called,  “ bisulphite 
of  lime.""  Bisulphite  of  lime  is  largely  used  as  an  antiseptic.  Under  the 
influence  of  oxidising  agents,  sulphurous  acid  and  the  sulphites  are  oxidised 
to  sulphuric  acid  and  sulphates. 

83.  Sulphuric  Acid,  H2SO4,  and  the  Sulphates. — Sulphuric  acid  is  one 
of  the  most  useful  chemical  compounds  known,  forming  as  it  does  the  start- 
ing point  in  the  manufacture  of  a number  of  substances  of  vast  importance 
in  the  arts.  When  in  the  pure  state,  sulphuric  acid  is  a colourless,  odourless 
liquid  of  an  oily  consistency  : this  latter  property  has  led  to  its  receiving 
the  popular  name  of  “ oil  of  vitriol ""  ; the  acid,  however,  is  in  no  way  con- 
nected chemically  with  the  class  of  bodies  known  as  fats  or  oils.  Sulphuric 
acid  is  nearly  twice  as  heavy  as  water,  having  a specific  gravity  of  I *842  ; 
it  boils  at  a temperature  of  338°  C.  Sulphuric  acid  has  a great  attraction 
for  water,  with  which  it  combines  to  form  definite  hydroxides  (Le.  chemical 
^compounds  with  water) ; considerable  heat  is  evolved  during  the  act  of 


38 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


union.  In  consequence  of  this  affinity  for  water,  sulphuric  acid  is  largely 
used  as  a desiccating  or  drying  agent  ; on  exposure  to  the  air  the  acid 
rapidly  increases  in  weight  by  absorption  of  water  vapour,  and  the  air 
becomes  dry  ; hence,  if  a vessel  of  sulphuric  acid  be  placed  under  a bell  jar, 
it  speedily  produces  a dry  atmosphere  inside.  Less  concentrated  varieties 
of  the  acid  form  staple  articles  of  commerce.  Owing  to  this  attraction  for 
water,  sulphuric  acid  is  a most  corrosive  body  ; wood,  paper,  and  most 
vegetable  and  animal  substances  are  vigorously  attacked  by  it  ; the  acid 
combines  with  the  hydrogen  and  oxygen  of  the  substance  in  the  proportions 
in  which  they  form  water,  and  leaves  behind  a mass  of  carbon,  together  with 
any  excess  of  either  hydrogen  or  oxygen  that  may  have  been  present.  This, 
of  course,  does  not  in  all  cases  represent  the  whole  of  the  chemical  action 
that  may  have  occurred.  Dilute  sulphuric  acid  contains  water  in  excess, 
and  therefore  does  not  exhibit  this  dehydrating  tendency  when  placed  in 
contact  with  other  bodies  ; it  is  well  to  remember  this,  because  in  a number 
of  reactions,  where  dilute  sulphuric  acid  is  employed,  it  produces  not  merely 
less  energetic  action,  but  action  absolutely  opposite  in  character  to  that  of 
the  concentrated  acid.  The  dilute  acid,  if  allowed  to  evaporate  in  contact 
with  paper,  etc.,  acts  in  a similar  manner  to  the  strong  acid,  as  the  water 
dries  off.  Sulphuric  acid  forms  a normal  and  an  acid  series  of  salts,  of  which 
Na2S04,  sodium  sulphate,  andNaHS04,  acid  sodium  sulphate,  are,  respect- 
ively, examples.  Most  of  the  sulphates  are  more  or  less  soluble  in  water  ; 
calcium  sulphate  is  only  slightly  so  ; barium  sulphate  is  insoluble  in  water 
and  dilute  acids.  Sulphuric  acid  and  the  sulphates  may  be  detected  in 
solution  by  the  addition  of  hydrochloric  acid  and  barium  chloride,  when 
they  produce  a white  precipitate  of  BaS04. 

84.  -Bromine,  Bfs  ; Iodine,  I2 ; and  Fluorine,  F2. — These  three  elements 
are  very  closely  allied  in  properties  to  chlorine  ; they  have  no  very  intimate 
connection  with  the  chemistry  of  wheat  and  flour.  Bromine  is  a liquid  ; 
iodine,  at  ordinary  temperatures,  is  a solid  body.  Iodine  is  slightly  soluble 
in  water,  readily  soluble  in  alcohol  or  a solution  of  potassium  iodide,  KI. 
Iodine,  or  its  solution,  produces  a characteristic  blue  colour  with  starch  : 
this  reaction  is  of  great  delicacy,  and  is  an  exceedingly  valuable  test  both 
for  starch  and  iodine.  Fluorine  forms  an  acid  with  hydrogen,  hydrofluoric 
acid,  HF,  which  is  characterised  by  its  power  of  attacking  and  dissolving 
glass  and  the  silicates  generally. 

85.  Silicon,  Si ; Silica,  Si02 ; and  the  Silicates. — Silicon  is  an  element 
somewhat  resembling  carbon  in  some  of  its  properties  ; all  that  at  present 
need  be  stated  about  it  is  that  it  forms  with  oxygen  an  oxide,  Si02,  analogous 
in  composition  to  that  of  carbon,  CO2.  This  oxide,  Si02,  is  termed  silica, 
or  at  times,  silicic  anhydride.  Flint  and  quartz  are  almost  chemically  pure 
forms  of  silica  ; in  this  form  silica  is  insoluble  in  water  and  all  acids,  and 
mixtures  of  acids,  except  hydrofluoric  acid.  On  being  fused  with  an  alkali 
as  KHO,  or  an  alkaline  carbonate,  K2CO3,  silica  produces  a glassy  substance 
entirely  soluble  in  water  : this  body  is  potassium  silicate,  K4Si04,  and  from 
it,  silicic  acid,  H4Si04,  may  be  obtained.  Silicic  acid  is  soluble  in  water 
and  is  tasteless  and  odourless  ; on  being  gently  evaporated  it  first  forms  a. 
jelly,  and  then,  as  the  whole  of  the  water  is  driven  off,  the  silica  remains  as 
a white  powder,  once  more  insoluble  in  water  and  acids.  As  silica  produces 
a compound  Avith  water  which,  by  action  on  bases,  forms  salts,  silica  is 
rightly  viewed  as  an  anhydride.  The  silicates  are  the  principal  constituents 
of  the  great  rock  masses  of  the  earth  and  of  soil.  The  natural  silicates, 
usually  contain  two  or  more  of  the  following  bases — iron  oxides,  alumina, 
lime,  magnesia,  potash,  and  soda.  With  the  exception  of  those  of  potash 
and  soda,  the  silicates  are  mostly  insoluble. 


ELEMENTS  AND  INORGANIC  COMPOUNDS. 


39 


86.  Phosphorus,  P4 ; Phosphoric  Acid,  H3PO4 ; and  the  Phosphates. — 

Like  several  other  elements,  phosphorus  assumes  more  than  one  distinct 
form.  The  commoner  variety  is  a crystalline  body,  often  called  yellow 
phosphorus.  In  addition  there  is  an  amorphous  variety,  which  from  its 
colour  is  frequently  known  as  red  phosphorus.  In  properties,  the  ordinary 
or  yellow  phosphorus  is  one  of  the  most  striking  of  the  elements  ; its  attrac- 
tion for  oxygen  is  so  great  that  it  has  to  be  kept  under  water  in  order  to 
prevent  its  oxidation.  In  process  of  manufacture,  the  ordinary  phosphorus 
is  usually  cast  into  sticks  of  a light  yeUaw  colour  and  the  consistency  of  wax  ; 
a piece  of  phosphorus  appears  luminous  in  the  dark  when  exposed  to  air  ; 
this  is  caused  by  its  slow  combustion.  A slight  elevation  of  temperature, 
or  even  friction,  suffices  to  cause  phosphorus  to  burn  vigorously  ; it  then 
produces  a vivid  light,  and  forms,  by  union  with  oxygen,  phosphorus  pent- 
oxide,  P2O6,  or,  as  it  is  sometimes  termed,  phosphoric  anhydride.  Phos- 
phoric anhydride,  as  thus  formed,  is  a white  powder,  which  combines  with 
water  with  great  avidity  to  form  phosphoric  acid,  H3PO4.  Phosphoric  acid 
is  principally  of  interest  because  of  its  salts,  known  as  phosphates  : of  these 
the  most  important  to  us  are  calcium  phosphate,  Ca3(P04)2  ; and  potassium 
phosphate,  K3PO4.  Calcium  phosphate  is  the  principal  constituent  of  the 
mineral  matter  of  bones,  and  hence  in  some  form  or  other  is  an  absolutely 
essential  article  of  food.  Phosphates  occur  in  some  parts  of  all  plants,  and 
is  derived  by  them  from  the  soil.  In  wheat,  the  phosphoric  acid  is  mostly 
combined  with  potassium.  The  alkaline  phosphates  are  soluble  in  water  ; 
the  others  are  insoluble,  but  may  be  readily  dissolved  by  the  addition  of 
nitric  or  hydrochloric  acid. 

87.  The  Metals  and  their  Compounds. — ^Within  the  limits  of  this  work 
it  would  be  impossible  to  give  even  the  briefest  systematic  description  of 
these  bodies.  An  account  follows  of  calcium  and  potassium,  but  such  other 
metallic  compounds  as  have  any  bearing  on  our  subject  will  be  described 
when  reference  to  them  is  made. 

88.  Calcium,  Ca,  and  its  Compounds. — ^Until  recently,  calcium  was 
scarcely  more  than  known  in  the  free  state.  It  is  a silver- white  metal,  and 
has  such  an  attraction  for  oxygen  that  it  very  readily  becomes  oxidised  on 
exposure  to  moist  air,  with  the  formation  of  calcium  oxide.  There  are  two 
oxides  of  calcium,  but  only  the  monoxide  is  of  practical  importance  in  con- 
nection with  the  present  subject.  This  body,  CaO,  is  that  commonly  spoken 
of  as  “ quicklime."’  The  salts  of  calcium  are  sometimes  referred  to  as  salts 
of  lime  ; this  is  not  strictly  correct,  but  in  most  cases  makes  no  real  differ- 
ence. To  this  there  is  one  exception.  Chloride  of  calcium,  or  calcium 
chloride,  is  CaCb  ; chloride  of  lime  is  a very  different  body,  CaOCL.  Cal- 
cium oxide  is  a whitish-grey  substance,  usually  obtained  by  the  action  of 
heat  on  the  carbonate  ; it  is  infusible  at  the  highest  temperatures.  Calcium 
oxide  combines  readily  with  water,  with  the  evolution  of  considerable  heat, 
forming  slaked  lime,  or  calcium  hydroxide,  CaH202.  Calcium  hydroxide 
occurs  as  a dry,  white  powder,  which  is  soluble  in  water  to  the  extent  of  one 
part  in  600.  This  solution  is  that  known  as  “ lime-water,”  and  is  employed 
as  a test  for  carbon  dioxide.  The  solution  of  lime  has  a decidedly  alkaline 
reaction,  turning  reddened  litmus  blue.  Calcium  produces  an  extensive 
series  of  salts  ; of  these  calcium  carbonate  has  been  already  referred  to 
when  describing  carbon  dioxide.  The  next  most  important  salt  is  calcium 
sulphate  ; this  body  is  only  slightly  soluble,  one  part  being  dissolved  by 
about  400  parts  of  water.  The  phosphate  and  chloride  have  already  been 
referred  to  ; the  latter  has  a great  affinity  for  water,  and  consequently  is 


40 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


often  used  as  a drying  agent  ; it  can  be  frequently  used  where  sulphuric 
acid  would  be  unsuitable  from  its  other  properties. 

89.  Potassium,  K,  and  its  Compounds. — Potassium  is  a soft  bluish 
white  metal,  which  has  so  great  an  attraction  for  oxygen  that  it  has  to  be 
kept  from  contact  with  the  air,  and  even  liquids  as  water,  which  contain 
oxygen  as  one  of  their  compounds  ; for  this  purpose  the  potassium  is  gener- 
ally preserved  in  mineral  naphtha,  a compound  of  carbon  and  hydrogen. 
The  normal  oxide  of  potassium  is  K2O  ; this  body  has  such  affinity  for  water 
that  it  practically  never  occurs  in  the  anhydrous  state,  but  usually  as  the 
hydroxide,  KHO.  Potassium  hydroxide  is  a white  crystalline  solid  sub- 
stance ; it  melts  at  a red  heat,  and  is  supplied  commercially  either  in  sticks, 
or  in  lumps  produced  by  breaking  up  fused  slabs  of  the  compound.  Potas- 
sium hydroxide  is  a powerfully  caustic  body,  and  rapidly  destroys  animal 
tissues.  It  is  one  of  the  most  powerful  alkalies  known,  restoring  the  blue 
colour  to  reddened  litmus,  and  forming  salts  with  acids.  Potassium  hydro- 
xide decomposes  ammonium  salts  with  the  liberation  of  ammonia  ; sodium 
hydroxide  and  lime  behave  similarly  in  this  respect.  Potassium  hydroxide 
is  very  soluble  in  water  ; the  solution  has  a peculiar  soapy  feel  to  the 
fingers.  Potassium  hydroxide  has  a great  attraction  for  carbon  dioxide  ; its 
solution  absorbs  that  gas  with  great  rapidity,  forming  potassium  carbonate, 
K2CO3.  Potassium  carbonate  is  a white  deliquescent  body ; i.e.  one  that 
readily  becomes  moist  through  the  absorption  of  water  . Like  other  de- 
liquescent bodies,  potassium  carbonate  is  very  soluble  in  water  ; the  solution 
is  strongly  alkaline  to  litmus,  although  the  salt  is  of  normal  constitution. 
As  already  explained,  the  very  strong  bases  produce  with  certain  weak  acids 
normal  salts,  in  which  the  alkaline  compound  may  be  said  to  predominate. 
Potassium  carbonate  was  at  one  time  almost  exclusively  obtained  from 
wood  ashes.  An  acid  potassium  carbonate,  KHCO3,  is  also  kno^vn  ; this 
body  is  neutral  to  litmus,  and  is  less  soluble  in  water  ; it  is  at  a temperature 
of  80°  C.  decomposed  into  the  normal  carbonate  and  free  acid. 

90.  Sodium  Compounds. — Sodium  forms  a series  of  compounds  which 
closely  resemble  those  of  potassium  ; of  these  the  most  familiar  are  sodium 
hydroxide,  NaHO  ; sodium  carbonate,  Na2C03  ; acid  sodium  carbonate, 
NaHC03  ; and  sodium  chloride,  NaCl.  Sodium  hydroxide  is  a somewhat 
less  powerful  base  than  potassium  hydroxide. 


CHAPTER  III. 

DESCRIPTION  OF  ORGANIC  COMPOUNDS. 

91.  “ Organic  ” Chemical  Compounds. — Chemical  science  is  commonly 
divided  into  two  branches,  known  respectively  as  “ Inorganic  ""  and  Or- 
ganic chemistry.  Certain  substances,  whether  they  occur  in  nature,  or 
are  prepared  in  the  laboratory,  are  obtained  from  mineral  sources  : the 
bodies  described  in  the  preceding  chapter  are  instances  of  such  compounds. 
There  are,  on  the  other  hand,  bodies  which  are  obtained  either  from  the 
animal  or  vegetable  kingdom.  Animals  and  vegetables  are  organised  bodies, 
that  is,  they  have  definite  organs  which  adapt  them  for  that  series  of  pro- 
cesses which  constitutes  what  is  called  “ life  ""  ; hence  chemical  compounds 
having  a vegetable  or  animal  origin  are  termed  “ organic.''  Those  which 
are  not  thus  obtained  from  organic  sources  are  termed  “ inorganic  ” com- 
pounds : the  two  names  have  also  been  given  to  the  branches  of  chemistry 
which  treat  respectively  of  these  two  classes  of  bodies,  and  of  their  properties 
and  reactions.  It  was  formerly  supposed  that  the  so-called  organic  bodies 
could  only  be  obtained  from  organic  sources  ; but  chemical  investigation 
has  demonstrated  that  many  such  compounds  can  be  produced  by  artificial 
means  from  the  elements  of  which  they  are  composed,  without  the  inter- 
vention of  living  organisms,  and  even  under  such  conditions  as  render  the 
existence  of  living  organisms  an  impossibility.  Alcohol  and  its  derivatives 
are  examples.  The  definition  of  an  organic  body  as  one  produced  as 
a result  of  “ life  " is  evidently  no  longer  tenable,  and  chemists  have  en- 
deavoured, with  more  or  less  success,  to  frame  new  definitions  of  organic 
chemistry.  As  all  organic  compounds  contain  carbon,  it  has  been  proposed  to 
define  it  as  the  “ chemistry  of  the  carbon  compounds  " ; again,  as  many 
organic  bodies  are  w^eU  defined  compound  radicals,  the  phrase,  “ chemistry 
of  the  compound  radicals  " has  been  proposed.  These  definitions  have  not 
been  found  entirely  satisfactory,  as  they  are  either  too  wide  or  too  narrow. 
They  present  the  further  difficulty  that  they  are  not  modifications  or  ex- 
planations of  the  term  organic  chemistry,  but  are  totally  new  phrases.  As 
this  branch  of  chemistry  is  still  called  organic  chemistry,  and  the  compounds 
included  in  its  scope  are  still  called  organic  compounds,  the  student  of  the 
chemistry  of  bread- making  may  regard  Organic  Chemistry  as  that  branch  of 
the  science  which  treats  of  the  composition  and  properties  of  those  compounds  whose 
usual  or  original  source  is  or  was  either  animal  or  vegetable.  This  explanation  of 
the  meaning  of  organic  chemistry  has  the  defect  that  it  does  not  include  all 
those  substances  now  known  as  organic  compounds  ; but  all  such  com- 
pounds thus  excluded  are  without  any  direct  bearing  on  the  chemistry  of 
wheat,  flour,  or  bread. 

92.  Organised  Structures. — ^Although  organic  compounds  can  be  prepared 
by  artificial  means,  it  must  be  clearly  understood  that  no  chemical  processes 
have  as  yet  been  found  capable  of  producing  an  organised  structure  ; furl  her,  all 
evidence  hitherto  obtained,  so  far  as  it  goes,  tends  to  prove  the  impossibility 
of  such  structures  being  formed  other  than  through  living  agencies.  Eor 
instance,  starch  is  found,  when  viewed  under  the  microscope,  to  have  a 

41 


42 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


structural  organisation  peculiar  to  it  self.  Starch  may  be  dissolved,  and  after 
such  solution  again  obtained  in  the  solid  state  ; but  the  solid  thus  produced 
shows  no  traces  of  the  original  structure  of  the  grains  of  starch  ; neither  is 
there  knovTi  any  artificial  process  by  which  the  starch  may  again  be  built 
up  into  structures  of  the  same  kind  as  those  in  which  it  originally  occurred. 
Similarly,  it  is  impossible  to  artificially  produce  a blood  corpuscle.  The 
same  law  applies  to  minute  organisms,  as  yeast,  bacteria,  etc.  ; none  of  these 
can  be  generated  otherwise  than  through  the  agency  of  previously  existing 
living  beings  of  the  same  type.  So  far  as  any  problem  can  be  proved  scienti- 
fically, this  fact  of  the  impossibility  of  spontaneous  generaticn  is  abundantly  demon- 
strated ; experimental  evidence  of  a most  conclusive  character  has  shown  as 
certainly  as  scientific  research  can,  in  any  case,  possibly  show,  that  living 
organisms  can  only  be  formed  by  means  of  similar  pre-existing  organisms. 

93.  Composition  of  Organic  Bodies.— Organic  compounds,  generally, 
have  a much  more  complicated  chemical  composition  than  have  inorganic 
compounds  ; they  are  mostly,  however,  restricted  to  comparatively  few 
elements.  All  organic  bodies  contain  carbon  ; many  are  composed  of 
carbon  and  hydrogen  only,  a greater  number  consist  of  carbon,  hydrogen, 
and  oxygen  ; while  others  contain  the  four  elements,  carbon,  hydrogen, 
oxygen,  and  nitrogen.  The  majority  of  organic  compounds  belong  to  one 
or  other  of  these  series.  Carbon,  more  than  any  other  element,  is  remark- 
able for  the  property  of,  in  compounds,  combining  directly  with  itseK,  and 
so  forming  most  complicated  bodies  out  of  comparatively  few'  elements. 


94.  Classification  of  Organic  Compounds. — The  number  of  these  is  so 
bewildering  that,  without  some  classification,  it  would  be  impossible  to 
grasp  their  relationship  to  each  other  : recent  chemical  science  has  suc- 
ceeded in  very  clearly  demonstrating  the  constitution  of  a vast  number  of 
these  bodies.  There  are,  in  the  first  place,  large  numbers  of  well  defined 
compound  radicals,  consisting  of  carbon  and  hydrogen  : it  has  been  found 
possible  to  group  these  into  distinct  families,  the  members  of  each  of  which 
may  be  represented  by  a common  formula. 


95.  Organic  Radicals. — ^The  most  important  series  of  these  is  that  known 
as  the  “ Methyl,’'  or  “ Ethyl  ” series  ; these  have  the  common  formula 
(C„H2„4.i)2-  This  formula  signifies  that  in  the  first  place  the  molecule  con- 
sists of  two  semi-molecules  that  are  similar  in  composition  ; secondly,  that 
in  each  semi-molecule  the  number  of  atoms  of  hydrogen  is  one  more  than 
double  the  number  of  atoms  of  carbon.  The  following  is  a list  of  a few  of 
the  radicals  of  this  series  : — 

Methyl 

Ethyl 

Propyl 

Butyl 

Amyl 

. Caproyl  . . 


Mea 

Eta 

Pr2 

Bua 

Ay2 

0P2 


CH3 

CH3 

C2H5 

C2H5  ’ 

C3H7 

C3H,  ’ 

C4H, 

C4H9 

C5H,, 

C5H,, 

CeHjg 

C6H,3 


or 


or 


/CH3\  f CMeHa 


VCHa\’  ""i  CMeHa 

f CEtHa 
I CEtHa 


or 


Each  semi-molecule  of  these  radicals  behaves  in  compounds  as  though 
it  were  an  atom  of  a monad  element  ; the  atomicity  is  shown  by  the  follow- 
ing graphic  formulae — 


ORGANIC  COMPOUNDS. 


43 


H H H 

I I I 

H— C—  H— C— C— 

H H H 

Methyl.  Ethyl. 


Irom  these  formulae  it  is  seen  that  in  each  case  there  is  one  of  the  carbon 
bonds  free  ; in  the  free  state  two  semi-molecules  unite  by  these  bonds  to 
form  the  molecule.  The  graphic  formulae  also  show  how  each  of  the  higher 
radicals  of  the  series  may  be  viewed  as  compounds  of  the  next  lower  radical 
with  an  additional  CH2.  The  temperature  of  the  boiling  points  of  these 
bodies  increases  as  the  series  is  ascended. 

96.  Hydrides  of  Organic  Radicals  (Paraffin  Group). — ^These  bodies  are 
compounds  of  the  radicals  with  hydrogen  ; those  of  the  series  already  re- 
ferred to  have  the  general  formula  C„H2„+2.  Among  them  there  is,  as  the 
lowest,  methane  or  methyl  hydride  (marsh  gas),  CH3H  or  CH4  ; from  this 
the  series  ascends  regularly  to  C^gH3  4.  These  compounds  are  distinguished 
by  their  not  being  readily  attacked  by  the  most  powerful  oxidising  agents, 
they  consequently  have  received  the  name  of  “ paraffins  (from  the  Latin, 
'parum  affinis,  having  little  affinity).  The  lower  members  of  the  series  are 
gases,  the  middle  are  liquids,  and  the  higher  members  are  solid  at  ordinary 
temperatures.  The  paraffins  are  produced  by  the  destructive  distillation 
of  wood,  coal,  and  many  other  organic  substances,  and  also  occur  in  rock- 
oils.  Some  varieties  of  American  petroleum  consist  almost  entirely  of 
paraffins.  In  distilling  the  crude  petroleum,  it  is  found  that  the  tempera- 
ture of  the  vapour  produced  rises  as  the  operation  progresses.  The  more 
volatile  portions  distil  oh  first  ; the  distillate  may  be  collected  in  separate 
portions  or  fractions  ; the  operation  is  then  termed  “ fractional  distilla- 
tion.'" The  lighter  or  more  volatile  paraffins  constitute  what  is  known  as 
light  petroleum  spirit  ; this  substance,  when  carefully  freed  from  solid  im- 
purities, is  of  great  use  as  a solvent  for  fatty  substances,  both  in  the  arts 
and  chemical  analysis.  Good  light  petroleum  spirit  should  distil  entirely  at 
a temperature  of  70°  C.  Such  spirit  is  a mixture  of  several  of  the  lower 
paraffins.  The  petroleum  of  commerce  consists  of  a somewhat  higher 
fraction,  and  mineral  lubricating  greases  and  “ vaseline  ” of  a yet  less  vola- 
tile portion.  The  least  volatile  portion  of  all  constitutes,  when  pure,  the 
hard  white  solid  substance  knovTi  as  “ solid  paraffin,"  or  paraffin  “ wax." 

97.  The  Alcohols. — ^In  constitution,  these  bodies  bear  the  same  relation 
to  the  organic  radicals  as  do  the  metallic  hydroxides  to  the  metals.  This 
is  clearly  seen  on  writing  representative  formulae  of  the  two  side  by  side  : — 

C2H5HO  NaHO 

Ethyl,  or  ordinary,  Alcohol.  Sodium  Hydroxide. 

Certain  chemists  carry  this  analogy  so  far  as  to  regard " the  alcohols  as 
hydrates  (hydroxides)  of  the  radicals,  and  term  ordinary  alcohol,  “ ethylic 
hydrate."  To  this  the  objection  has  been  taken  that  the  alcohols  do  not 
contain  water,  and  that  the  hydroxides  are  really  hydrated  oxides,  or 
oxides  formed  by  the  union  of  water  with  the  normal  oxide,  as,  for 
example : — 

Na20  + H2O  = 2NaHO. 

The  argument  is,  however,  addressed  to  the  composition  of  these  bodies 
rather  than  to  the  mode  of  formation  ; and  it  is  clear  that  these  bodies 
may  be  regarded  as  compounds  of  the  organic  radicals  with  hydroxyl  (HO). 


44 


THE  TECHNOLOGY  OF  BREAD-MAKING, 


It  is  then  simply  a matter  of  definition  whether  or  not  the  term  hydrate  or 
hydroxide  shall  be  understood  to  mean  a compound  with  hydroxyl.  The 
alcohols  are  sometimes  conveniently  regarded  as  substitution  products  of 
the  paraffins  ; thus  ethyl  alcohol  may  be  viewed  as  ethane,  C2Hg,  in  which 
hydroxyl  is  substituted  for  one  of  the  atoms  of  hydrogen.  In  this  manner 
the  relationship  between  the  alcohols  and  the  paraffins  is  clearly  seen.  Like 
metallic  hydroxides,  the  alcohols  enter  into  combination  with  acids  to  form 
organic  salts.  Thus  ethyl  alcohol,  being  C2H3HO,  is  converted  by  the 
action  of  hydrochloric  acid  into  C2H5CI,  ethyl  chloride.  This  reaction  is 
analagous  to  that  by  which  sodium  hydroxide  is  converted  into  sodium 
chloride,  as  is  shown  by  the  respective  equations  ; — 

C2H5HO  -f  HCl  = C2H5CI  + H2O. 

Alcohol  or  Ethyl  Hydroxide.  Hydrochloric  Acid.  Ethyl  Chloride.  Water. 

NaHO  + HCl  = NaCl  + H2O. 

Sodium  Hydroxide.  Hydrochloric  Acid.  Sodium  Chloride.  Water. 

Of  the  various  alcohols,  those  of  the  methyl  series  are  the  most  important, 
and  are  represented  by  the  formula,  C„H2,j+iHO.  Subjoined  are  a few 
examples  of  these  compounds  : — 

Methyl  Alcohol,  CH3HO,  or  | cH^HO.  Butyl  Alcohol,  C4H9HO. 

Ethyl  „ CAHO,or{CH3jjo 

Propyl  ,,  C3H7HO.  Melissic  „ CaoHgiHO. 

The  lower  members  of  the  series  are  liquid,  and  the  higher  solid. 

98.  Methyl  Alcohol,  CH3HO. — ^This  body,  in  an  impure  form,  is  yielded 
on  the  destructive  distillation  of  wood,  and  hence  is  commonly  known  as 
“ wood  spirit,''  or  “ wood  naphtha."  This  crude  preparation  has  a nauseous 
flavour,  which  renders  it  unfit  for  drinking  : the  pure  methyl  alcohol  has, 
on  the  contrary,  a purely  spirituous  taste  and  odour.  Methyl  alcohol  mixes 
in  all  proportions  with  water,  ethyl  alcohol,  and  ether  ; it  has  at  15°  C.  a 
specific  gravity  of  0*8021. 

99.  Ethyl  Alcohol,  | or  C2H5HO. — ^This  body  constitutes 

the  active  ingredient  of  beer,  wine,  and  of  all  spirituous  liquors,  as  brandy, 
whisky,  etc.  The  term  “ alcohol,"  when  used  without  any  prefix,  is  always 
understood  to  refer  to  this  compound,  which  is  known  popularly  as  “ spirits 
of  wine."  Alcohol  may  be  produced  artificially  from  its  elements  by  purely 
chemical  means,  but  is  always  manufactured  by  the  process  of  fermentation, 
of  which  a detailed  account  is  hereafter  given.  Pure  ethyl  alcohol  is  a 
colourless,  mobile  liquid,  having  an  agreeable  spirituous  odour,  and  a burn- 
ing taste.  Alcohol  is  inflammable,  and  burns  with  a scarcely  luminous 
smokeless  flame,  evolving  considerable  heat  ; it  is  on  this  account  largely 
used  in  “ spirit  " lamps  as  a fuel.  Alcohol  rapidly  evaporates  at  ordinary 
temperatures,  and  when  pure,  boils  at  78*4°  C.  (=  173*1°)  F.  . At  a tem- 
perature of  15*5°  C.,  alcohol  has  a specific  gravity  of  0*79350  ; that  of  water, 
at  the  same  temperature,  being  taken  as  unity.  Alcohol  mixes  with  water, 
and  also  ether,  in  all  proportions  : for  the  former  compound  it  has  a great 
affinity,  and  evolves  considerable  heat  on  the  tw^o  being  mixed  ; the  volume 
of  the  mixture  is  less  than  that  of  the  two  liquids  taken  separately.  As 
previously  mentioned,  alcohol  is  manufactured  by  fermentation  ; this  pro- 
cess is  only  f apable  of  producing  a comparatively  dilute  solution  of  alcohol 
in  water.  In  order  to  obtain  a stronger  spirit,  the  fermented  liquid  is  dis- 


ORGANIC  COMPOUNDS. 


45 


tilled  ; as  alcohol  boils  at  a lower  temperature  than  water,  the  earlier  por- 
tions of  the  distillate  are  the  stronger  in  spirit,  until  finally  no  alcohol  re- 
mains in  the  liquid  being  distilled.  It  is  not  possible  to  obtain  in  this  manner 
alcohol  free  from  water,  as  even  the  very  first  portions  of  spirit  which  distil 
over  carry  water  with  them.  By  several  times  distilling  the  spirit  it  is 
possible  to  obtain  a mixture  containing  about  90  per  cent,  of  the  pure  spirit  ; 
special  distilling  arrangements  have  resulted  in  the  production  of  a distillate 
containing  as  much  as  95  per  cent,  of  alcohol.  In  order  to  remove  this 
small  quantity  of  water,  the  spirit  is  treated  with  quicklime  or  potassium 
carbonate,  and  then  allowed  to  stand,  and  after  a time  distilled  : in  this 
manner  alcohol  can  be  obtained  in  which  there  is  only  the  most  minute 
trace  of  water.  This  desiccated  alcohol  is  termed  “ absolute  ” alcohol. 
Alcohol  is  of  very  great  use  as  a solvent,  particularly  for  many  organic 
bodies  ; it  also  acts  as  an  antiseptic,  and  hence  is  employed  for  the  preser- 
vation of  biological  and  other  specimens.  The  solvent  power  of  alcohol  is 
modified  considerably  by  its  admixture  with  more  or  less  water  : for  many 
purposes  alcohol  of  a certain  definite  strength  is  necessary.  As  water  and 
alcohol  have  different  densities,  and  as  density  is  easily  measured,  it  is  a 
usual  method  of  testing  the  strength  of  alcohol  to  take  its  specific  gravity. 
Tables  have  been  prepared  giving  the  strength  in  percentages  of  alcohol 
present  for  different  densities.  Three  distinct  standards  of  strength  of 
alcoholic  spirit  are  commercially  recognised.  The  “ rectified  spirit  of 
wine  of  the  British  Pharmacopoeia  is  the  strongest  spirit  that  can  be 
produced  by  the  ordinary  methods  of  distillation  : such  spirit  should  contain 
84  per  cent,  by  weight  of  absolute  alcohol,  and  should  have  a density  of 
0*838.  “ Proof  spirit  ” is  a term  that  has  survived  its  original  application  : 

it  is  now  legally  defined  as  spirit  of  such  a strength  that  13  volumes  of  it 
shall  weigh  at  51°  F.  the  same  as  12  volumes  of  water  at  the  same  tempera- 
ture. Proof  spirit  has  at  15°5°C.  a density  of  0*91984,  and  contains  49*24 
l^er  cent,  by  weight  of  alcohol  and  50*76  of  water.  Weaker  spirits  are  de- 
fined as  being  so  many  degrees  “ under  proof  (U.P.),  while  stronger  spirits 
are  referred  to  as  being  so  many  degrees  “ over  proof  ""  (O.P.).  A spirit  of 
10  degrees  U.P.  is  such  that  it  contains  90  per  cent,  of  proof  spirit  and  10 
per  cent,  of  water  ; spirit  of  10  degrees  O.P.  is  of  such  a strength  that  it 
may  be  made  up  to  110  volumes  by  the  addition  of  water,  and  Avould  then 
have  the  same  percentage  of  alcohol  as  proof  spirit.  Absolute  alcohol  is 
that,  as  before  s ated,  which  contains  no  water.  For  chemical  purposes  it 
is  usual  to  specify  the  strength  of  alcohol,  either  as  so  much  per  cent,  spirit, 
or  by  its  density.  When  for  any  purpose  it  is  directed  that  alcohol  of  a 
certain  strength  must  be  employed,  particulars  will  be  given  as  to  its 
density  ; for  complete  tables  of  densities  and  corresponding  strengths, 
the  larger  treatises  on  chemistry  must  be  consulted. 

100.  Detection  of  Alcohol. — ^Alcohol  when  present  in  any  quantity  is 
easily  recognised  by  its  smell  ; in  liquids  which  contain  traces  only,  it  is 
best  to  distil  and  then  examine  the  first  portions  of  the  distillate.  When 
using  a Liebig’s  condenser,  it  will  be  seen,  at  the  point  where  the  vapour 
begins  to  condense,  that  when  alcohol  is  present,  the  distillate  trickles  down 
the  sides  of  the  tube  in  peculiar  oily  looking  drops  or  “ tears.”  This  appear- 
ance ceases  as  soon  as  the  whole  of  the  alcohol  has  distilled  off.  Very 
minute  quantities  of  alcohol  suffice  to  produce  this  effect.  Another  and 
more  delicate  method  for  its  detection  depends  on  the  production  of  iodo- 
form. This  body  has  the  symbol  CHI3,  and  is  similar  in  constitution  to 
chloroform,  CHCI3.  The  liquid  under  examination  should  first  be  distilled, 
and  the  tests  applied  to  the  first  portion  of  the  distillate.  Ten  c.c.  are  to 
be  taken  and  rendered  alkaline  by  the  addition  of  about  a quarter  of  a c.c. 


46 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


(five  or  six  drops)  of  a 10  per  cent,  solution  of  sodium  hydroxide  ; the 
liquid  must  next  be  warmed  to  about  50°  C.,  and  then  a solution  of  potas- 
sium iodide,  saturated  with  iodine,  added  drop  by  drop  until  a slight  excess 
of  free  iodine  is  present  ; this  is  indicated  by  the  liquid  acquiring  a per- 
manent sherry  yellow  tint.  The  liquid  must  next  be  just  decolourised  by  the 
addition  of  a minute  quantity  of  the  sodium  hydroxide  solution.  If  there 
be  any  alcohol  present,  a yellow  crystalline  precipitate  of  iodoform  gradually 
forms.  Certain  other  organic  compounds,  however,  are  capable  of  pro- 
ducing the  same  reaction. 


101.  Methylated  Spirits  of  Wine. — ^Alcoholic  liquors  are  subject  to  a 
high  duty  ; consequently,  for  purposes  other  than  the  production  of  drink- 
able spirits,  the  Excise  authorities  permit  the  sale,  duty  free,  of  a mixture 
of  rectified  spirit  with  some  substance  which  imparts  a flavour  sufficiently 
nauseous  to  render  the  whole  absolutely  undrinkable,  except  to  the  palates 
of  the  most  debased  dipsomaniacs.  Formerly  spirit  was  thus  “ denatured  ” 
by  the  addition  of  one  volume  of  commercial  wood  spirit  to  nine  volumes  of 
rectified  spirit.  Being  produced  by  the  addition  of  crude  methyl  alcohol, 
the  mixture  was  known  as  “ methylated  spirits  of  wine.'’  Other  bodies  are 
now  used  for  “ methylating,"  among  them  being  some  of  the  lighter  paraf- 
fins. For  most  laboratory  operations,  methylated  spirits  can  be  used  as  a 
substitute  for  rectified  spirits  of  wine  : for  delicate  purposes  it  is  well  to 
re-distil  the  spirits  prior  to  use.  On  diluting  the  distilled  spirit  to  about 
70  per  cent,  strength,  opalescence  is  produced.  This  is  due  to  paraffin 
Avhich  distils  over,  and  is  insoluble  in  the  mixture  of  spirit  and  water.  As 
the  cloudiness  is  due  to  the  presence  of  a volatile  substance,  it  does  not 
interfere  with  many,  or  even  most,  uses  to  which  the  spirit  is  applied. 
Methylated  spirits  may  be  rendered  almost  absolute  by  adding  about  one- 
third  of  its  weight  of  recently  burned  quicklime,  and  thoroughly  shaking  ; 
the  mixture  must  be  allowed  to  stand  some  three  or  four  days,  and  the 
shaking  repeated  two  or  three  times  daily.  The  spirit  must  then  be  dis- 
tilled, precautions  being  taken  to  prevent  the  temperature  unduly  rising. 
The  still  should  be  fixed  in  a water  bath,  consisting  of  an  iron  saucepan 
containing  brine.  The  clear  portions  of  the  spirits  should  first  be  poured 
into  the  still,  without  disturbing  the  sediment,  and  distilled  to  dryness  by 
application  of  heat  to  the  water  bath.  Care  must  be  taken  that  the  bath 
does  not  boil  dry.  The  pasty  mass  of  lime  may  next  be  placed  in  the  still, 
preferably  in  small  quantities  at  a time,  and  heated  by  the  bath  so  long  as 
any  alcohol  distils  over.  An  efficient  condensing  worm  must  be  used,  and 
the  tube  connecting  it  with  the  still  ought  to  be  a long  one.  At  the  close 
of  the  operation  the  lime  may  be  removed  from  the  vessel  used  as  a still  by 
soaking  with  water. 


102.  Propyl,  Butyl,  and  Amyl  Alcohols. — These  bodies  are  produced 
in  small  quantities  during  fermentation.  They  all  boil  at  a higher  tempera- 
ture than  ethyl  alcoliol,  and  are  found  in  the  residual  liquor  after  most  of 
tlie  spirit  has  been  distilled  over.  Propyl  alcohol  occurs  in  the  residues  of 
the  distillation  of  the  fermented  liquor  of  the  marc  of  grapes  in  the  produc- 
tion of  low-class  brandy.  Normal  butyl  alcohol  occurs  in  genuine  cognac, 
from. which  it  may  be  obtained  by  fractional  distillation  : it  has  a boiling 
point  of  116*8°  C.,  and  possesses  an  agreeable  odour.  But  spirits  from 
potatoes,  beet-root,  maize,  and  certain  other  substances  contain  isobutyl 
alcohol,  an  isomeride  of  the  normal  alcohol.  Isobutyl  alcohol  has  a dis- 
agreeable fusel-oil-like  odour.  The  following  formulae  indicate  their  differ- 
ence in  constitution  : — 


ORGANIC  COMPOUNDS. 


47 


/^TJ  /^TT  ^CHs 

L^xl2L'Xl2'^-tl3  0x1 

CH2H0  CH2H0 

Normal  Butyl  Alcohol.  Isobutyl  Alcohol. 

In  addition  to  isobutyl  alcohol,  amyl  alcohol  is  also  produced  as  a bye- 
product  during  the  manufacture  of  alcohol  from  potatoes  or  grain.  Amyl 
alcohol  is  an  oily  looking  liquid,  which  does  not  mix  with  water,  but  with 
alcohol  and  ether  in  all  proportions  ; it  boils  at  137°  C.  Amyl  alcohol  has 
a strong,  disagreeable  smell,  and  burning  taste.  Its  intoxicating  effects  are 
similar  to  those  of  ethyl  alcohol,  but  a small  quantity  of  amyl  alcohol  suf- 
fices to  produce  all  symptoms  of  intoxication  ; it  has  been  estimated  that 
amyl  alcohol  is  fifteen  times  as  intoxicating  as  is  ethyl  alcohol. 

103.  Fusel  or  Fousel  Oil. — ^This  name  is  applied  to  the  oily  mixture 
of  spirits  above  referred  to  as  being  formed  during  fermentation.  The 
fusel  oil  of  potato  and  grain  spirits  principally  consists  of  amyl  alcohol. 

104.  Glycerin,  C3H5(HO)3.— In  constitution  this  body  is  an  alcohol, 
and  may  be  regarded  as  the  paraffin  propane,  C3H8,  in  which  three  of  the 
hydrogen  atoms  have  been  replaced  by  three  groups  of  hydroxyl.  When 
pure,  glycerin  is  a colourless,  odourless,  and  thick  sirupy  liquid,  having  a 
sweet  taste,  and  boiling  at  a temperature  of  290°  C.  Glycerin  is  one  of  the 
substances  produced  during  the  normal  fermentation  of  sugar,  and  also  is 
the  basic  constituent  of  fats  and  oils. 


105.  Mannitol,  C6H8(HO)6  . — This  is  a substance  possessing  a sweet 
taste  and  found  in  the  sap  of  certain  plants,  which  sap  when  dried  consti- 
tutes what  is  known  as  manna.  In  constitution  mannitol  is  a hexahydric 
alcohol,  and  is  of  interest  from  its  relationship  to  the  sugars  and  other 
carbohydrates.  Mannitol  is  regarded  as  being  derived  from  the  paraffin 
hexane,  CgH^^,  by  the  replacement  of  six  atoms  of  hydrogen  by  six  hydroxyl 
groups. 


106.  The  Ethers. — These  bodies  are  the  oxides  of  the  organic  radicals  : 

(C  H 

term  “ether''  is  employed  without  any  qualification,  it  is  this  body  to 
which  reference  is  made.  From  its  mode  of  preparation,  ether  is  often 
termed  “ sulphuric  ether  " ; sulphuric  acid,  of  course,  does  not  enter  into 
its  composition.  Ether  is  a colourless,  very  mobile  liquid,  having  a peculiar, 
penetrating,  and  characteristic  smell.  This  smell  has  given  rise  to  the 
term  “ ethereal  odour."  Ether  has  a specific  gravity  of  0*736,  it  does  not 
mix  with  water  ; but,  on  being  added,  forms  a layer  on  the  surface.  The 
ether  dissolves  a certain  quantity  of  water,  while  the  water,  on  the  other 
hand,  holds  a portion  of  the  ether  in  solution.  Ether  boils  at  34*5°  C.,  and 
is  very  volatile  at  ordinary  temperature.  The  vapour  is  inflammable  ; and, 
as  may  be  gathered  from  the  formula,  is  very  heavy.  Great  care  must  be 
taken  when  working  with  ether  to  keep  all  lights  at  a safe  distance.  The 
high  density  of  the  vapour  causes  it  to  flow  as  a dense  layer  along  a level 
surface  for  a considerable  distance  ; in  this  way  there  is  danger  of  the 
vapour  communicating  with  a light  that  may  be  placed  even  at  the  further 
end  of  a long  table.  The  rule  should  invariably  be  adopted  of  having  no 
more  of  the  liquid  in  the  immediate  neighbourhood,  where  experiments  are 
being  made,  than  is  necessary  for  the  purpose  in  hand  ; the  store  bottle 
should  not  be  kept  in  the  laboratory.  Ether  is  of  great  use  as  a solvent  for 
fats,  resins,  and  other  organic  bodies. 


48 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


107.  Esters  or  Ethereal  Salts. — ^These  bodies  are  produced  by  the  displace- 
ment of  the  hydrogen  of  acids  by  organic  radicals  ; the  acid  may  be  organic 
or  inorganic.  The  compounds  of  such  radicals,  with  chlorine,  bromine, 
and  iodine,  are  at  times  viewed  as  a sub-class  of  these  bodies,  and  are  termed 
“ haloid  ''  esters.  The  esters  were  at  one  time  called  “ compound  ethers,'^ 
but  the  newer  name  “ester  is  now  employed  in  order  to  differentiate  them 
from  the  true  ethers  or  oxides  of  organic  radicals.  The  following  are  formulae 
of  examples  of  esters  : — 

C2H5CL  C2H5C2H3O2.  C5H^iC2H302. 

Ethyl  Chloride.  Ethyl  Acetate.  Amyl  Acetate. 


NaCl.  NaC2H302. 

Sodium  Chloride.  Sodium  Acetate. 


NaC2H302. 

Sodium  Acetate. 


The  corresponding  sodium  salts  are  written  underneath  in  order  to  show 
their  similarity  in  constitution.  Amyl  acetate  is  the  confectioner’s  well- 
known  jargonelle  pear  flavouring,  while  pineapple  essence  consists  of  an- 
other ester,  ethyl  butyrate,  C2H5C4H^02. 

On  appropriate  treatment  with  sodium  hydroxide,  the  esters  are  split 
up  with  the  formation  of  a sodium  salt,  thus*: — 


C2H5C2H3O2  + NaHO  = NaC2H302  + C2H5HO. 

Ethyl  Acetate.  Sodium  Hydroxide.  Sodium  Acetate.  Alcohol  (Ethyl  Hydroxide). 

The  reaction  is  similar  to  that  of  sodium  hydroxide  on  a weaker  inorganic 
base,  as  ammonium  : — 


NH4CI  -f  NaHO  = NaCl  + NH4HO. 

Ammonium  Chloride.  Sodium  Hydroxide.  Sodium  Chloride.  Ammonium  Hdyroxide. 


108.  Chloroform,  CHCI3. — In  a number  of  organic  compounds  it  is 
possible  to  replace  the  atoms  of  certain  elements  present  by  those  of  others  ; 
in  this  way  what  are  called  “ substitution  products  ” are  formed.  Starting 
with  methyl  hydride,  CH4,  the  hydrogen  of  this  body  may  be  replaced  atom 
by  atom  by  chlorine  until  CCI4  is  formed.  The  replacement  of  three  atoms 
of  hydrogen  by  chlorine  results  in  the  production  of  chloroform,  CHCI3. 
This  compound  is  at  ordinary  temperatures  a heavy  volatile  liquid,  having 
a specific  gravity  of  1*48.  The  vapour  of  chloroform  has  a peculiar  but 
pleasant  smell,  and  when  inhaled  produces  insensibility  to  pain,  while  in 
less  quantities  it  causes  stupefaction.  No  danger  need,  however,  be  appre- 
hended during  any  ordinary  working  with  this  substance.  Chloroform  boils 
at  a temperature  of  60 *8° C.  Chloroform,  like  ether,  acts  as  a solvent  of 
many  organic  bodies  ; it  is  only  slightly  soluble  in  water,  and  after  being 
shaken  up  with  that  liquid  more  or  less  quickly  subsides  and  forms  a layer 
at  the  bottom. 


109.  Iodoform,  CHI3. — This  is  a yellow  solid  body,  analogous  in  con- 
stitution to  chloroform. 


110.  Organic  Acids. — These  bodies  constitute  a numerous  class  of 
organic  compounds  ; like  the  radicals,  they  are  capable  of  subdivision  into 
distinct  families,  the  members  of  which  exhibit  considerable  resemblance 
to  each  other.  Several  of  these  groups  of  acids  are  derivatives  from  corre- 
sponding series  of  alcohols. 


111.  Fatty  Acids,  or  Acids  of  Acetic  Series. — These  acids  may  be  repre- 


series 


r C H 1 

sented  by  the  general  formula,!  ’ The  lowest  member  of  the 

is  formic 

acid,|^Qjl^Q  or  HC2H3O2.  Acetic  acid  is  the  derivative  from  ethyl  alco- 


COHO 

or  HCHO2.  The  next  and  best  known  is  acetic 


ORGANIC  COMPOUNDS.  49 


hoi.  It  will  be  of  service  to  place  side  by  side  for  comparison  the  formulae 
of  ethyl  and  some  of  its  principal  derivatives  : — 


C2H5HO,  or 


f C0H5 

tCA 

Ethyl. 

f CH3 
\ CH2HO 


C2ll5^ 

Ethyl  Oxide  or  Ether. 

CH3 
COH 


Ethyl  Hydroxide  or  Alcohol.  Acetic  Aldehyde. 


CH3 

COHO 

Acetic  Acid. 


By  oxidising  agents,  two  atoms  of  hydrogen  may  be  removed  from  alcohol 
with  the  formation  of  acetic  aldehyde.  This  body  is  formed  as  an  inter- 
mediate step  between  alcohol  and  acetic  acid.  Aldehyde  readily  combines 
with  another  atom  of  oxygen  to  form  acetic  acid.  Further  reference  is 
made  subsequently  to  the  aldehydes  as  a class. 


112.  Acetic  Acid, — This  body  is  a liquid  which  boils  at  a temperature 
of  117°  and  freezes  at  17°  C.  ; it  has  a sharp  but  pleasant  smell,  and  is  well 
known  in  a dilute  form  as.  vinegar.  Vinegar  is  manufactured  by  a species 
of  fermentation  from  alcohol  : its  interest  in  connection  with  our  present 
subject,  lies  in  the  fact  that  during  many  fermenting  processes  acetic  acid 
is  produced. 


113.  Butyric  Acid, 


C3H, 

COHO, 


or  HC4H„02. — This  body  bears  the  same 


relation  to  butyl  alcohol  that  acetic  acid  does  to  that  of  ethyl.  Butyric 
acid  occurs  in  rancid  butter,  sweat,  and  many  animal  secretions.  It  is 
also  one  of  the  products  of  putrefaction,  or  putrid  fermentation,  of  many 
organic  substances  ; for  instance,  it  may  be  formed  in  considerable  quantity 
by  the  action  of  putrid  cheese  on  sugar.  Butyric  acid  is  a liquid  having 
a sharp  odour  resembling  that  of  rancid  butter. 


114.  The  Higher  Fatty  Acids. — These  have  received  their  special  name 
because  of  their  occurrence  as  constituents  of  many  natural  fats  ; among 

those  thus  found  are  butyric  acid  (above  described)  ; palmitic  j^Q^Q) 

or  HC^j.H3^02  ; margaric  acid,  HC^7H3302 ; and  stearic 

f C H 

acid,  I qqjjq’  or  HCj8H3.02.  These  latter  bodies  are  at  ordinary  tem- 


peratures fatty  solids,  melting  into  oily  liquids  with  an  increase  of  tempera- 
ture. Physically,  they  bear  little  resemblance  to  acetic  acid  ; but  the 
formulae  at  once  show  their  similarity  in  constitution. 


115.  Fats  and  Soaps,  or  Salts  of  Higher  Fatty  Acids. — Most  natural 
fats  are  salts  of  the  higher  fatty  acids,  with  glycerin  as  the  base  ; for  ex- 
ample, mutton  fat  is  essentially  composed  of  the  stearate  of  glycerin.  This 
body  may  be  artificially  produced  by  heating  together  stearic  acid  and 
glycerin,  according  to  the  following  equation — 


3HC,8H3.502  + C3H5(H0)3  = C3H5(C,8H350  2)  3 + 3H2O. 

Stearic  Acid.  Glycerin.  Glycerin  Stearate.  Water. 

Some  natural  fats  contain  an  excess  of  the  fatty  acid  over  and  above  that 
sufficient  to  combine  with  the  whole  of  the  glycerin  present. 

In  addition  to  the  “ fatty  acids,  acids  of  another  group,  known  as 
the  oleic  series,  are  found  as  constituents  of  natural  oils  and  fats.  Oleic 
acid,  HC,8H3302,  is  the  product  of  oxidation  of  an  alcohol  of  the  family 
C„H2„_,H0  series  : it  will  be  noticed  that  the  formula  of  the  acid  differs 
from  that  of  stearic  acid  by  containing  two  atoms  less  of  hydrogen  : this 

B 


50 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


difference  follows  from  the  difference  in  the  typical  formulae  of  the  two 
series  of  alcohols.  Tlie  oleates  of  glycerin  constitute  the  oils  or  liquid  portions 
of  fats. 

By  the  action  of  alkalies,  as  soda  or  potash,  the  fats  are  decomposed, 
with  the  formation  of  sodium  or  potassium  salts  of  the  fatty  acids,  and  the 
liberation  of  glycerin  in  the  free  state.  These  salts  constitute  the  bodies 
known  technically  as  “ soaps,""  those  of  sodium  are  the  “ hard,""  and  those 
of  potassium  “ soft  ""  soaps.  The  separation  of  fats  into  glycerin  and  the 
fatty  acids  may  also  be  effected  by  forcing  a current  of  steam  through  the* 
melted  fat.  The  glycerin  distils  over  with  the  steam.  This  operation  of 
decomposing  fat  by  the  aid  of  alkalies  is  termed  “ saponification,""  and,  in 
addition  to  its  great  use  in  the  commercial  manufacture  of  soap,  constitutes 
a valuable  method  of  investigating  the  composition  and  properties  of  natural 
fats  and  oils. 

Some  few  other  organic  acids  of  interest  yet  remain  to  be  described  : 
among  these  there  is  : — 

116.  Lactic  Acid,  HC3H5O3. — This  body  occurs  in  sour  mhk,  and  is 
also  produced  in  greater  or  less  quantities  during  fermentation  with  ordinary 
commercial  yeast.  Lactic  acid  is  a sirupy  liquid  of  specific  gravity  1*215, 
colourless  and  odourless,  and  having  a very  sharp  sour  taste.  It  forms  a 
well-defined  series  of  salts. 

117.  Succinic  Acid,  H2C4H4O4. — Succinic  acid  is  a white  solid  boly, 
soluble  in  water.  It  is  one  of  the  bodies  produced  during  the  normal  alco- 
holic fermentation  of  sugar.  On  being  heated,  succinic  acid  evolves  dense 
suffocating  fumes. 

118. "  Tartaric  Acid,  H2C4H4O6. — This  body  occurs  naturally  as  a con- 
stituent of  the  juice  of  the  grape,  and  in  various  other  plants.  It  is  when 
pure  a white  ^olid  crystalline  body,  soluble  in  water,  and  possessing  a plea- 
sant sour  taste.  On  being  heated,  tartaric  acid  evolves  an  odour  of  burnt 
sugar.  Tartaric  acid  is  dibasic,  and  forms  both  an  acid  and  a normal  series 
of  salts,  termed  “ tartrates.""  The  well-known  substance  “ cream  of  tartar  "" 
is  acid  potassium  tartrate,  KHC^H^Og  ; this  body  has  an  acid  reaction, 
and,  like  tartaric  acid,  decomposes  sodium  carbonate  with  the  evolution 
of  carbon  dioxide  gas.  As,  however,  one-half  the  hydrogen  has  been  al- 
ready replaced  in  cream  of  tartar  by  potassium,  that  salt  has  only  half  the 
power,  molecule  for  molecule,  of  decomposing  sodium  carbonate  that  is 
possessed  by  free  tartaric  acid.  When  acid  potassium  tartrate  is  neutralised 
by  the  addition  of  sodium  carbonate  so  long  as  effervescence  occurs, 
there  is  produced  a double  tartrate  of  potassium  and  sodium,  KNaC^H^Og. 
This  body  is  soluble  in  water,  and  is  known  as  “ Rochelle  salt."" 

119.  Definition  of  Homologues,  ete. — At  this  stage  of  the  subject  it 
will  be  convenient  to  explain  the  meaning  which  is  attached  to  “ homo- 
logue  ""  and  other  similar  terms  used  in  describing  organic  bodies.  Series 
of  bodies  are  termed  homologous,  in  which  their  general  constitution  maybe  repre- 
sented by  a typical  formula  ; thus,  the  organic  radicals  of  the  methyl  series  are 
homologous,  so  too  are  the  corresponding  alcohols,  and  also  the  fatty  acids. 
The  melting  and  boiling  points  of  the  members  of  a homologous  series 
usually  rise  as  the  series  is  ascended.  When  capable  of  being  vapourised, 
their*density  in  the  gaseous  condition  increases  with  the  ascent  of  the  series. 
In  many  cases,  the  lower  members  of  a series  of  homologues  are  more  chemi- 
cally active  than  are  the  higher  members. 

Many  organic  bodies  are  known  which  not  only  contain  the  same  ele- 
ments, but  also  contain  them  in  the  same  proportion,  while  their  physical 


ORGANIC  COMPOUNDS. 


51 


and  chemical  character  show  them,  nevertheless,  to  be  distinct  compounds. 
Distinct  compounds,  having  the  same  percentage  ccmpcsiticn,  are  said  to  he 
“ isomers,"'  or  “ isomeric  with  each  other.”  Isomerism  may  be  of  different 
kinds.  Thus,  bodies  may  have  the  same  percentage  composition,  and  yet 
have  different  molecular  weights  : in  these  cases  the  molecular  weights  are 
multiples  of  the  simplest  possible  molecular  weight  that  can  be  deduced 
from  the  percentage  composition.  Bodies  having  the  same  percentage  com- 
, position,  hut  different  molecular  weights,  are  said  to  he  “ polymers,"  cr  “ poly- 
meric ” with  each  other.  The  following  are  instances  of  polymeric  bodies  : — 

Ethylene  — C2II4. 

Propylene — C3H6. 

Butylene  — C4II8. 

In  addition  to  isomerism  of  the  above  type  there  is  yet  another  more  striking 
variety.  When  distinct  chemical  compounds  have  not  only  the  same  percentage 
composition,  hut  also  the  same  molecular  weight,  they  are  said  to  he  “ metamers,” 
or  “ metameric  " with  each  other.  As  examples  of  metameric  compounds, 
the  following  three  bodies  may  be  cited — propylamine,  methylethylamine, 
and  trimethylamine.  These  three  bodies  all  have  the  formula  NC3H9. 
That  they  are  distinct  compounds  containing  the  same  proportions  of  carbon 
and  hydrogen,  but  united  together  to  form  different  organic  radicals,  is 
seen  when  the  formulae  are  written  as  below  : — 


f CsH, 

rcH3 

N H 

N C2H5 

IH 

1h 

Propylamine. 

Methylethylamine. 

f CH3 
N CH3 
ICH3 

Trimethylamine, 


The  nature  and  constitution  of  these  bodies  are  described  in  paragraph  126. 


120.  The  Aldehydes. — One  of  the  members  of  this  group,  acetic  alde- 
hyde, has  already  been  mentioned  in  a previous  paragraph  ; as  explained, 
its  preparation  is  effected  by  the  removal  of  hydrogen  from  the  correspond- 
ing alcohol.  Hence  the  name  aldehyde,  derived  from  “ afcohol  dehydvo- 
genatum."  The  lowest  aldehyde  of  the  ethyl  series  is  that  derived  from 
methyl  alcohol  according  to  the  following  equation  : — 

CH3HO  = HCOH  + H2. 

Methyl  Alcohol.  Methyl  or  Formic  Aldehyde  (Formaldehyde).  Hydrogen. 

The  oxygen  of  the  aldehydes  is  directly  united  to  the  carbon,  and  is  not 
present  as  hydroxyl  as  in  the  alcohols.  This  is  shown  in  the  comparative 
graphic  formulae  given  subsequently. 

Formic  aldehyde  is  a powerful  and  well-known  disinfectant  ; its  solu- 
tion in  water,  termed  formalin,  is  employed  both  as  a disinfectant  and 
preservative. 

121.  The  Aldoses. — Closely  allied  to  the  aldehydes  are  the  bodies  collec- 
tively known  as  aldoses.  Among  these  is  hexose,  which  is  an  aldose  con- 
taining six  atoms  of  carbon,  and  having  the  formula  HsCOHAHCOHUOH, 
or  CgHjaOg.  There  are  several  hexoses,  one  of  the  number  being  the  well- 
known  sugar,  glucose.  Hexose  and  the  homologous  aldoses  have  for  ulae 
which  are  multiples  of  that  of  formic  aldehyde.  They  all  contain  the  CO 
group. 

122.  The  Ketones. — A group  of  substitution  compounds  is  produced 
by  the  replacement  of  the  hydrogen  of  an  aldehyde  by  a radical  of  the  ethyl 
series  ; thus  acetone  results  from  the  substitution  of  methyl  for  hydrogen 
in  acetic  aldehyde  : — 


52 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


CH3COH.  CH3COCH3. 

Aldehyde.  Acetone. 

These  bodies  are  called  ketones,  the  name  being  derived  from 
acetone.  It  will  be  observed  that  the  independent  CO  group  is  still  present. 
An  important  ketone  is  butyl-methyl  ketone,  of  which  the  formula  is 
C4HyCO-CH3. 


123.  The  Ketoses. — The  ketoses  may  be  regarded  as  ketones  in  which 
the  hydrogen  of  the  radical  has  in  part  been  replaced  by  hydroxyl.  By 
this  replacement  butyl-methyl  ketone  becomes  the  ketose,  fructose  or  Isevu- 
lose,  of  which  the  formula  is  CHaOH-CHOH'CHOH-CHOH-CO-CHaOH. 
Lsevulose  is  a form  of  sugar.  The  relationship  of  these  various  bodies  to 
each  other  is  of  importance  as  throwing  light  on  the  chemical  constitution 
of  the  sugars  and  other  allied  compounds,  to  which  in  subsequent  chapters 
extended  reference  is  made.  The  following  graphic  formulae  show  how 
these  bodies  are  related  to  each  other. 


H 

I 

H— C— H 

I 

0 


H 

I 

H— C=0 


H 

Methyl  Alcohol. 


Methyl,  or  Formic,  Aldehyde. 


H 

H 

H 

1 

H— C— H 

1 

I 

H— C— H 

1 

H— C— H 

1 

H— C— H 

1 

1 

H— C=0 

I 

H— C— H 

1 

0 

1 

I 

H— C— H 

1 

H 

j- 

H— C=0 

Ethyl  Alcohol. 

Acetic  Aldehyde. 

[Butylrddebvdo. 

H 

H 

I 

H— C— H 

1 

H— C— 0— H 

1 

H— C— H 

1 

H— cLo— F 

1 

H— C— H 

1 

H— C— 0— H 

1 

H— C— H 

1 

1 

H— C— 0— H 

1 

H— C— H 

1 

1 

H— C— 0— H 

1 

H— C— H 

1 

1 

H— C=0 

1 

0 

Hexylio  Alcohol. 

Hexose,  Glucose. 

ORGANIC  COMPOUNDS. 
H H 


53 


H— C— H 

H— C— 0— H 

I 

H— C— H 

H— C— 0— H 

I 

H— C— H 

I 

H— C— 0— H 

1 

H— C— H 

1 

1 

H— C— 0— H 

1 

1 

c=o 

1 

C-:0 

1 



H— C— H 

1 

H— C— 0— H 

1 

H 

Butyl-Methyl  Ketone, 

1 

H 

Lasvulose  (Ketose). 

The  relationship  between  methyl  alcohol  and  its  corresponding  aldehyde 
is  very  simple,  one  atom  of  hydrogen  and  one  group  of  hydroxyl  are  replaced 
by  an  atom  of  dyad  oxygen.  The  same  holds  good  with  regard  to  ethyl 
alcohol  and  acetic  aldehyde.  An  inspection  of  the  formulae  shows  that 
while  in  the  alcohol  the  ethyl  radical  is  intact  and  is  combined  with  an 
extraneous  group  of  hydroxyl,  in  the  corresponding  aldehyde  the  oxygen 
atom  has  made  an  inroad  into  the  ethyl  group  and  has  replaced  one  of  its 
atoms  of  hydrogen.  The  aldehyde  is  not  that  of  the  intact  C,jH2„+i 
radical,  but  that  of  the  next  higher  member  of  the  series.  Similarly,  butyl 
is  C4H9,  but  butyl  aldehyde  is  C3H7COH  as  shown  in  the  graphic  formula. 

Coming  next  to  the  hexose  as  a member  of  the  aldoses,  the  formula  of 
hexylic  alcohol  is  given  beside  it  in  order  that  the  two  types  may  be  com- 
pared. In  the  case  of  five  of  the  carbon  atoms,  an  atom  of  hydrogen  has 
been  replaced  by  hydroxyl,  while  with  the  remaining  carbon  atom  the  same 
change  has  occurred  as  in  the  conversion  of  alcohols  into  aldehydes. 

The  formation  of  ketones  is  rendered  clear  by  the  before  given  formulae 
of  aldehyde  and  acetone.  Turning  to  the  more  complicated  ketones,  the 
formula  of  butyl- methyl  ketone  is  given,  but  the  principle  of  the  nomen- 
clature is  not  quite  the  same.  Butyl  aldehyde  is  C3H7COH,  in  accordance 
with  the  rule  of  naming  other  aldehydes,  but  that  part  of  the  formula  of 
butyl-methyl  ketone  above  the  dotted  line  which  is  on  the  pattern  of  the 
formula  of  an  aldehyde,  in  composition  reads  C4II9CO— , that  is  to  say,  the 
butyl  radical  is  intact  with  the  aldehydic  carbon  atom  added  on  to  it.  Fol- 
lowing the  same  rule  as  in  aldehydes  generally,  this  would  be  regarded  as 
the  aldehyde  of  the  next  higher  radical,  amyl,  CsHn.  One  must,  there- 
fore, regard  these  ketones  as  combinations  of  the  group  CO  (carbonyl) 
with  the  intact  radicals  from  which  the  name  is  derived. 

In  the  ketoses,  a portion  of  the  hydrogen  of  the  ketone  is  replaced  by 
groups  of  hydroxyl,  and  examination  of  the  formulae  shows  the  ketoses  to 
bear  much  the  same  relation  in  composition  to  the  ketones  as  do  the  aldoses 
to  the  corresponding  alcohols. 

J24.  Pentose  and  Pentosan. — Passing  mention  must  be  made  of  the 
pentose  group  of  aldoses.  These  contain  five  atoms  of  hydrogen,  the  formula 
of  pentose  being  CsH^oOs.  By  condensation  with  elimination  of  water,  the 
pentoses  furnish  the  corresponding  pentosans  thus  : — 

C5H40O5  = C5H8O4  + H2O. 

Pentose.  Pentosan.  Water. 

These  bodies  ar  e found  in  the  woody  fibre  of  the  outer  envelope  of  wheat, 
and  by  hydrolysis  yield  pentose  sugars. 


54 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


125.  Nitrogenous  Organic  Bodies.— Many  organic  compounds,  both 
from  animal  and  vegetable  sources,  contain  nitrogen  as  one  of  their  con- 
stituents. The  constitution  of  the  majority  of  these  bodies  has  not  as  yet 
been  completely  investigated  ; a large  number  of  them  are,  however,  basic 
in  their  character,  and  hence  are  known  as  nitrogenous  organic  bases,  or 
“ alkaloids.’' 


126  Amines,  Substitution,  or  Compound,  Ammonias.— Many  of  the 
nitroae’nous  organic  bodies  are  built  upon  the  same  type  as  ammonia,  and 
may  be  viewed  as  ammonia  in  which  one  or  more  of  the  atoms  of  hydrogen 
are  replaced  by  compound  radicals.  These  compounds  are  termed  “ amines,” 
or  “ substitution  ammonias.”  The  three  bodies,  propylamine,  methylethyl- 
amine  and  trimethylamine,  whose  formula  are  given  in  a preceding  para- 
graph’ are  examples  of  amines.  The  methylamines  are  gases  at  ordinary 
temperatures,  having  a strong  ammoniacal  and  fish-like  smell.  Trimethyl- 
amine is  produced  by  decomposing  proteins,  and  is  the  source  of  the  char- 
acteristic smell  of  fish. 


127  Alkaloids.— This  name  is  applied  to  a class  of  organic  bodies,  most 
of  which  contain  nitrogen,  carbon,  hydrogen,  and  oxygen.  All  these  bodies 
are  basic  while  many  are  able  to  neutralise  even  the  strongest  acids,  as 
sulphuric  acid.  They  are,  as  a class,  remarkably  energetic  in  their  action 
on  animals;  thus,  quinine  and  morphine  are  most  powerful  medicines, 
while  strychnine  and  brucine  are  among  the  most  violent  poisons;  but 
little  is  understood  of  the  constitution  of  the  alkaloids  ; it  is  probable  that 
they  are  of  the  same  type  as  the  compound  ammonias.  For  the  sake  of 
uniformity  in  chemical  nomenclature,  it  has  been  proposed  to  restrict  the 
termination  “ ine  ” to  the  alkaloids  ; for  this  reason,  glycerin,  dextrin, 
etc.,  should  never  be  written  glycerine,  dextrine,  etc. 

128  Amino-acids  — ^The  amino-acids  are  bodies  intermediate  in  character 
between  an  acid  and  a weak  base,  fulfilling  under  difierent  circumstances 
the  functions  of  either.  They  have  no  acid  taste,  do  not  redden  litmus,  and 
are  derivatives  from  organic  acids  in  which  hydrogen  of  the  acid  radical  is 

replaced  by  amidogen.  . „ -j 

Among  members  of  this  group  are  glycine,  or  amino-acetic  acid, 

C'aHeNOarthe  relation  of  which  to  acetic  acid  is  shown  in  the  following  graphic 
formulae  ; — 

H H 


H— C— H 
0=C-0-H 

Acetic  Acid. 


H— C— N 


-H 

H 


0=C— 0— H 

Amino- Acetic  Acid. 


Aspartic  acid,  amino-succinic  acid,  C4H7N04,  and  glutamic  acid,  amino- 
glutaric  acid,  C5H9NO4,  are  members  of  this  group.  So  also  are  leucine, 
amino-caproic  acid,  CeH.aNOa,  and  tyrosine,  amino-oxy-phenyl-propionic 
acid,  C9H44NO3.  All  these  bodies  are  important  constituents  and  decom- 
position  products  of  the  proteins.  Leucine  is  soluble  at  12  C.  in  48  parts 
of  water  and  800  of  alcohol  ; and  insoluble  in  ether  Tyrosine  dissolves 
in  150  parts  of  boiling  water,  and  is  insoluble  in  alcohol  and  ether. 

129  Amides  —Amides  maybe  regarded  as  derivatives  of  acids  in  which 
amidogen,  NH^  replaces  hydroxyl,  HO;  or  they  may  be  looked  on  as 
ammonia  in  which  one  or  more  of  the  hydrogen  atoms  are  replaced  by 
organic  radicals.  Urea,  CON3H4,  is  a typical  amide.  It  may  be  viewed 
L a derivative  of  carbonic  acid,  CO(HO)3,  in  which  case  the  two  groups  of 


ORGANIC  COMPOUNDS. 


55 


HO  are  replaced  by  two  groups  of  NH2  ; or  on  the  other  hypothesis  may  be 
regarded  as  two  molecules  of  ammonia,  NH3,  with  a pair  of  hydrogen 
atoms  replaced  by  CO,  thus 


/H 


\N— C— N^ 


li 

0 


= CON2H4 

Urea,  Carbamide. 


The  amides  are  distinguished  from  the  amines  by  the  latter  being  incap- 
able of  derivation  in  constitution  from  an  acid. 

Among  amides  found  in  plants  are  asparagine,  C4H8N2O3,  and  glutamine, 
C5H10N2O3.  Asparagine  is  the  amide  of  amino-succinic  acid.  The  relation 
between  succinic  acid,  amino-succinic  acid,  and  the  amide  asparagine  is 
shown  in  the  following  formulae  : — 


0=C— 0— H 

I 

H— C— H 
H— C— H 
0=C— 0— H 

Succinic  Acid. 


0:=C— 0— H 

I JJ 

H— c— N c:" 

I 

H— C— H 

I 

0=C— 0— H 

Amino-Succinic  Acid. 


0=C— 0— H 

I TJ 

H-C-NCS 


H— C— H 

I H 

0=C-N  Ch 

Asparagine  (Amide). 


The  amides  are  crystalline,  diffusible  bodies.  Asparagine  is  soluble  in 
hot  water,  but  not  in  alcohol  or  ether. 


130.  Phenylhydrazine. — ^Among  the  compounds  of  nitrogen  with  hydro- 
gen is  that  known  as  hydrazine,  N2H4.  Further,  there  is  a compound  of 
hydrogen  and  carbon  named  benzene,  CsHe.  This  body  is  regarded  as  a 
combination  of  a radical,  phenyl,  CeHs,  with  hydrogen.  The  generally 
accepted  view  of  the  composition  of  the  bodies  of  this  group  is  that  sug- 
gested by  Kekule,  who  regarded  the  carbon  atoms  as  forming  a closed  chain, 
as  shown  in  the  following  formula  : — 

H 

H C H 

\ 

c c 


c c 

/ X/'\ 

H C H 

I 

H 

Benzene  or  Phenylliydride. 


If  one  of  the  atoms  of  hydrogen  in  hydrazine  be  replaced  by  phenyl, 
CeHs,  phenylhydrazine  is  produced,  and  has  the  formula,  C6H5NHNH2. 
This  body  is  of  importance  because  of  the  great  value  it  has  been  in  the 
investigation  of  the  composition  of  the  sugars. 


131.  Phenylhydrazones  or  Hydrazones. — ^Phenylhydrazine  is  eapable 
of  entering  into  combination  with  aldehydes,  aldoses,  ketones  and  ketoses, 
in  the  proportions  of  one  molecule  of  each  with  the  elimination  of  a molecule 
of  water.  The  bodies  thus  produced  are  termed  phenylhydrazones,  or 
more  briefly,  hydrazones.  The  formation  of  two  of  these  bodies  is  shown  in 
the  following  equations  : — 


56 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


CH3COH  -f  N2H3C6H5  = CH3CN2H2C6H5  -f  H2O. 

Aldehyde.  Phenylhydrazine.  Aldehyde-hydrazone.  Water. 

H2C0H(HC0H)4C0H+N2H3C6H5=H2C0H(HC0H)4CN2H2C6H5+H20. 

Hexose,  Glucose.  Phenylliydrazine.  Glucose-hydrazone.  Water. 

The  hydrazones  occasionally  serve  as  means  of  identifying  sugars,  but 
are  far  exceeded  in  value  for  that  purpose  by  the  compounds  described  in 
the  next  paragraph. 

132.  Phenylosazones  or  Osazones. — ^When  an  aqueous  solution  of  either 
an  aldose  or  ketose  is  heated  together  with  phenylhydrazine  acetate  in  the 
proportion  of  one  molecule  of  the  former  to  three  molecules  of  the  acetate, 
a somewhat  complicated  reaction  ensues.  Among  its  products  is  a compound 
consisting  of  two  molecules  of  phenylhydrazine  with  one  of  the  aldose  or 
ketose,  which  body  is  a phenylosazone,  or  more  shortly  osazone.  Taking 
the  example  of  glucose,  the  following  is  the  formula  of  the  phenyl- 
glucosazone  : — 

H2C0H(HC0H)3CN2HC6H5CN2H2C6H5. 

( Phenylglucosazone. 

Two  groups  of  phenylhydrazine  have  become  incorporated  in  the  mole- 
cule of  glucose  with  the  elimination  of  two  molecules  of  water.  There  are 
other  secondary  chemical  changes  which  need  not  be  further  described. 
The  osazones  have  well  marked  chemical  characteristics  in  the  direction  of 
opticity  and  other  properties.  These  are  of  great  service  in  identifying 
particular  sugars,  the  modus  operandi  being  to  prepare  the  osazone,  and 
then  through  the  properties  of  this  body  to  identify  the  sugar. 


CHAPTER  IV. 


THE  MICROSCOPE,  AND  POLARISATION  OF  LIGHT. 

133.  Object  of  Microscope. — description  of  the  microscope,  and  method 
of  using  it,  is  given  at  this  early  stage,  because  the  student  will  continually 
find  it  requisite  to  have  recourse  to  this  instrument  from  time  to  time,  while 
going  on  with  his  study  of  the  chemical  properties  of  the  various  grain 
constituents.  In  order  to  thoroughly  understand  the  physical  construc- 
tion of  bodies  it  is  necessary  to  see  them.  The  microscope  is  an  instru- 
ment to  enable  us  to  see  points  of  physical  construction  which  are  so  minute 
as  to  escape  the  unaided  vision. 

134.  Description  of  Microscope. — ^The  demand  for  good  microscopes 
has  led  to  the  supply  by  a number  of  makers,  both  English  and  Continental, 
of  really  excellent  instruments  at  low  cost.  In  consequence,  the  microscope 
is  not  now,  even  to  the  general  public,  an  unfamiliar  piece  of  apparatus. 
These  pages  are  not  the  place  where  an  exhaustive  description  of  micro- 
scopes could  with  fitness  be  given,  but  as  the  instrument  should  be  in  the 
hands  of  every  miller  and  baker,  a few  hints  as  to  how  to  use  it  for  such 
purposes  as  those  occurring  during  milling  and  bread-making  will  naturally 
find  a place  in  this  work.  As  an  instrument  suitable  for  the  work  of  miller 
and  baker,  the  authors  have  figured  one  supplied  by  Charles  Baker,  of  244, 
High  Holborn,  London.  These  microscopes  are  cheap  (in  the  best  sense  of 
the  term),  of  excellent  make,  and  always  trustworthy. 

Every  reader  will  probably  be  familiar  with  the  general  appearance 
of  the  instrument  as  shown  in  the  illustration.  The  microscope  proper 
consists  of  the  stand,  to  which  is  attached  the  main  tube  of  the  instrument, 
by  means  of  a sliding  “ dove- tail ''  arrangement,  that  can  be  raised  or 
lowered  by  a rack  and  pinion  : the  pair  of  milled  heads,  d,  actuate  this 
pinion.  Below  is  another  pair  of  milled  heads,  E,  which  are  more  delicate  in 
their  action,  and  constitute  what  is  known  as  the  “fine  adjustment.”  The 
stage,  G,  is  that  part  of  the  instrument  arranged  for  the  reception  of 
the  objeet  being  examined.  It  consists  of  a flat  surface  at  right  angles 
to  the  axis  through  the  tube  of  the  microscope,  and  carries  on  it  a 
pair  of  spring  clips,  f,  by  means  of  which  the  glass  on  which  the  object  is 
mounted  is  held  on  the  stage,  g,  and  thus  may  be  shifted  in  any  direction 
by  the  fingers.  Underneath  the  stage  is  a contrivanee  known  technically 
as  the  sub-stage,  h : this  is  also  fitted  with  a rack  and  pinion,  and  may  be 
raised  or  lowered  by  the  milled  head,  i.  The  central  aperture  of  the  sub- 
stage is  arranged  to  take  either  a sub-stage  illuminator  (Abbe  condenser), 
a series  of  diaphragms,  the  polariser  of  a polarising  apparatus,  or  other 
desired  sub-stage  fittings.  Beneath  this  again  is  a concave  glass  mirror, 
J,  so  mounted  as  to  be  easily  placed  in  any  required  position.  The  tube 
of  the  miroscope,  together  with  the  stage  and  mirror,  can  be  turned  at  any 
angle  to  the  tripod  stand,  from  the  vertical  to  the  horizontal.  Within  the 
main  tube  is  fitted  a second,  b,  known  as  the  “draw  tube,”  which  can  be 
pulled  out  if  required,  thus  inereasing  the  distance  between  the  eye-piece 
and  object  glass.  A scale  is  engraved  on  the  side  of  the  draw  tube,  by  which 

57 


58 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  amount  of  withdrawal  can  be  observed  and  noted.  The  lower  end  of 
the  main  tube  is  provided  with  an  internal  screw  at  c,  for  the  purpose  of 
receiving  the  combinations  of  lenses  known  as  “ object  glasses/"  or  “ objec- 
tives."" The  objectives  of  all  the  best  makers  are  now  cut  with  the  same 
screw  thread,  and  so  are  interchangeable.  The  “ eye-piece/"  a,  also  a lens 
combination,  slides  into  the  top  of  the  draw  tube.  The  objectives  are  named 
according  to  their  focal  length,  and  are  consequently  termed  “ 1-in.  objec- 


Fig.  2. — The  Microscope. 


fives,""  etc.  One  of  these  is  shown  in  position  at  L.  The  greater  the  focal 
length,  the  less  is  the  magnifying  power  of  an  objective.  The  eye-pieces 
also  vary  in  magnifying  power,  and  are  usually  referred  to  as  “A,""  “ B "" 
eye-pieces,  and  so  on  ; the  magnification  increases  with  each  successive 


THE  MICROSCOPE. 


59 


letter  of  the  alphabet,  commencing  with  A.  The  student  will  require  a 
series  of  objectives,  consisting  of  the  2-inch,  1-inch,  and  J-inch  ; these  will  be 
found  to  answer  most  purposes,  although  for  bacteriological  work  a yV-inch 
oil  immersion  objective  in  addition  is  exceedingly  useful.  In  working 
with  a microscope  it  is  frequently  necessary  to  change  from  a high  to  a low 
magnifying  power.  In  order  to  do  this  rapidly,  microscopes  are  now  pro- 
vided with  a carrier,  k,  which  screws  into  the  tube  at  c,  and  to  which  a 
number  of  objectives,  L,  l1,  l2,  is  attached.  By  rotating  this  carrier  the 
various  objectives  may  be  quickly  exchanged  for  each  other.  In  the  follow- 
ing description  it  will  be  assumed  that  the  instrument  is  fitted  with  such  a 
carrier.  For  ordinary  work  the  A eye-piece  is  sufficient,  but  a C eye-piece 
is  also  at  times  useful.  The  following  accessories  are  requisite  : one  or 
two  dozen  glass  slides,  3 inches  by  1 ; some  thin  glass  covers — these  may  be 
round  or  square,  and  should  be  about  f inch  diameter,  or  square  ; a pair  of 
fine  forceps  ; one  or  two  needles  set  in  handles  ; a glass  rod  drawn  out  to 
a point  at  one  end,  and  a small  piece  of  glass  tubing.  All  these  may  be 
obtained  from  the  maker  of  the  microscope,  and  are  usually  supplied  in  the 
case  with  the  instrument.  Other  useful  pieces  of  additional  apparatus 
will  be  mentioned  as  necessity  arises  for  their  employment. 

A word  may  be  said  in  the  first  place  about  the  preserving  of  the  instru 
ment  from  injury.  When  not  in  use  it  should  either  be  kept  in  its  case,  or, 
what  is  more  convenient,  under  a glass  shade,  as  then  it  can  be  readily 
used  when  required.  A mounted  longitudinal  section  of  a grain  of  wheat 
should  be  purchased  at  the  same  time  as  the  instrument  ; this  is  a very 
useful  slide  to  possess,  and  will  give  the  student  an  opportunity  of  learning 
how  to  use  his  microscope  before  he  proceeds  to  mounting  objects  for 
himself. 

135.  How  to  Use  the  Microscope. — ^To  commence  using  the  instrument, 
remove  it  from  the  case,  take  the  2-inch  objective  out  of  its  box  and  screw 
it  into  the  bottom  of  the  tube  ; next  insert  the  eye-piece  in  its  place.  The 
lenses,  if  dusty,  may  be  very  gently  wiped  with  either  an  old  silk  handker- 
chief that  has  been  often  washed,  or  a piece  of  wash-leather.  One  or  other 
of  these  should  be  kept  solely  for  this  purpose.  The  less,  however,  that  the 
lenses  require  wiping  the  better,  as,  being  made  of  soft  glass,  they  easily 
scratch.  When  working  on  yeast,  temporarily  mounted  in  water  or  other 
liquid  substance,  it  is  necessary  to  set  the  stage  horizontal,  as  otherwise 
the  liquid  flows  downward.  But  with  fixed  and  permanent  objects,  the 
microscope  should  be  inclined  to  an  angle  of  about  45  degrees,  as  in  such  a 
position  the  eye  is  much  less  fatigued  during  observation.  The  next  requisite 
is  light.  In  the  daytime  choose  a room  that  is  well  lighted,  if  possible  not 
by  direct  sunlight,  but  by  a bright  cloud.  At  night  an  incandescent  gas  burner, 
especially  if  enclosed  in  a ground  glass  globe,  makes  a good  source  of  light. 
Raise  the  microscope  tube  by  turning  the  pinion,  by  means  of  the  milled 
head,  d,  until  the  end  of  the  objective  is  about  2 inches  from  the  stage. 
Place  the  mounted  wheat  grain  slide  on  the  stage,  and  arrange  the  clips  to 
hold  it  firmly.  Next  turn  the  mirror  so  as  to  throw  the  spot  of  light  on 
the  object.  Now  look  down  the  eye-piece  and  lower  the  microscope  tube 
until  the  object  is  focussed  ; that  is,  until  its  outlines  are  seen  clearly  with- 
out being  blurred.  A word  may  here  be  said  about  the  amount  of  light 
advisable  ; generally  speaking,  the  rule  may  be  laid  down  that  it  is  wise 
to  work  with  no  more  light  than  necessary.  The  light  should  not  be  bright 
enough  to  dazzle  the  eye  in  the  slightest  degree  ; on  the  other  hand,  it 
should  be  sufficient  for  the  object  to  be  seen  comfortably.  The  2-inch  objec- 
tive will  show  the  greater  portion  of  the  grain  of  wheat  occupying  the  whole 
of  the  field  of  vision.  Any  object  when  seen  through  the  microscope  is 


60 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


inverted  ; that  is,  the  top  is  seen  at  the  bottom,  and  the  left  side  at  the  right. 
By  pulling  out  the  draw  tube  the  object  is  still  further  magnified. 

In  the  next  place  rotate  the  carrier  so  as  to  substitute  the  1-inch  for  the 
2-inch  objective.  The  microscope  tube  will  now  have  to  be  lowered  until 
the  object  is  again  in  focus.  A smaller  portion  only  of  the  wheat-grain 
is  seen  in  the  field,  but  that  portion  is  magnified  to  a much  greater  degree. 

The  illumination  is  much  less  than  with  the  2-inch  object  glass.  Notice 
that  more  of  the  details  of  the  object  can  be  distinguished. 

The  J-inch  objective  may  now  be  tried.  Unless  the  section  is  a very  thin 
one,  it  will  not,  however,  show  up  well.  Having  exchanged  the  inch  for 
this  power,  lower  the  microscope  tube  until  the  end  of  the  object  glass 
is  within  an  eighth  of  an  inch  from  the  slide  ; then  move  the  milled  head 
D,  very  slowly  and  carefully,  watching  all  the  time  until  the  object  is  again 
in  focus  : for  this  purpose  it  is  well  to  move  the  slide  until  a portion  of  the 
skin  of  the  grain  is  in  view.  The  milled  head,  e,  may  now  be  used  for  mak- 
ing the  final  adjustment  of  the  focus.  This  latter  milled  head  is  termed  tlie 
“ fine  adjustment,"’  while  that  by  means  of  the  rack  and  pinion  is  spoken 
of  as  the  “ coarse  adjustment.”  For  the  lower  powers  the  coarse  adjust- 
ment is  sufficient. 

This  exercise  with  the  three  powers  will  have  shown  the  student  the 
mode  of  using  his  microscope.  He  must  accustom  himself  to  moving  the 
object  about  on  the  stage,  so  as  to  get  any  portion  he  wishes  in  view  ; this 
presents  some  little  difficulty  at  first,  because  the  movement  must  be  made  in 
the  opposite  direction  to  that  in  which  it  is  desired  that  the  magnified  image 
shall  travel. 

Any”;  experimenting  with  the  oil  or  water  immersion  objective  had 
better  be  postponed  until  the  student  arrives  at  the  stage  of  examining 
bacteriological  specimens. 

136.  Measurement  of  Microscopic  Objects. — The  microscope  is  not  merely 
used  for  the  purpose  of  seeing  small  objects,  but,  with  the  addition  of  certain 
accessories,  is  also  employed  for  measuring  their  size.  The  first  object 
requisite  for  this  purpose  is  a “ stage  micrometer  ” ; an  eye-piece  micrometer 

should  also  be  procured.  The  stage  micrometer 
may  consist  of  a fraction  of  an  inch  further  divided 
up  into  tenths  and  hundredths,  or  preferably  of  a 
millimetre  similarly  graduated.  The  scale  for  this 
purpose  is  accurately  photographed  on  a glass 
slip,  the  same  as  an  ordinary  slide.  It  will  be 
remembered  that  the  millimetre  is  very  nearly  the 
twenty-fifth  part  of  an  inch,  consequently  the 
tenth  or  hundredth  of  a millimetre  may  be  taken 
as  equal  to  the  two  hundred  and  fiftieth,  or  two 
thousand  five  hundredth  part  of  an  inch.  Work- 
ing with  low  powers,  it  is  sufficient  for  rough 
purposes  to  place  the  stage  micrometer  face  down- 
Avards  on  the  object  to  be  measured,  and  then  to 
read  the  number  of  divisions  of  the  micrometer 
over  which  the  object  to  be  measured  extends. 
This  can  only  be  done  with  powers  sufficiently  low 
to  permit  the  lines  on  the  micrometer,  and  the 
object  under  examination,  to  be  in  focus,  or  nearly 
so,  at  the  same  time.  The  eye-piece  micrometer 
is,  for  all  purposes,  far  preferable.  - This  instru- 
ment consists  of  a scale  engraved  on  a circular 
piece  of  glass,  as  shown  in  Fig.  3,  which  is 


Fig.  3.  Eye-Piece 
Micrometer. 


THE  MICROSCOPE. 


61 


fixed  in  a specially  adapted  eye-piece,  also  figured.  The  top  of  the  eye- 
piece draws  out,  and  the  micrometer  scale  is  dropped  in,  so  as  to  rest  on  the 
diaphragm  shown  in  section  midway  of  the  eye-piece.  The  figures,  of 
course,  must  be  uppermost,  so  as  to  read  rightly  on  looking  down  the  micro- 
scope. The  scale  being  in  position,  the  sliding  tube  of  the  eye-piece  itself 
is  drawn  up  or  down  until,  on  looking  through  it,  the  graduations  are  sharply 
focussed.  With  the  eye-piece  in  position,  on  looking  down  the  microscope, 
both  the  eye-piece  scale  and  the  object  are  seen  in  focus  together.  The 
scale  looks  as  though  it  were  simply  superposed  on  the  object.  The  value 
of  this  scale  varies  with  each  different  power  employed,  but  may  be  deter- 
mined in  the  following  manner — place  the  lowest  power  into  position  on 
the  microscope  ; put  the  stage  micrometer  on  the  stage,  and  read  off  care- 
fully in  tenths  and  hundredths  of  a millimetre  the  value  of  one  division  of 
the  eye-piece  micrometer.  Next  repeat  the  same  measurement  in  exactly 
the  same  way  with  each  of  the  other  objectives.  In  these  determinations 
the  draw  tube  must  invariably  be  in  the  same  position  ; it  is  best  to  have 
it  always  closed  when  the  microscope  is  being  used  for  measuring  purposes. 
Thus,  for  example,  with  one  of  the  microscopes  in  the  possession  of  the 
authors  one  division  of  the  eye-piece  has  the  following  values  wdth  different 
objectives  : — 


Objective.  M.m.  M.k.m.  Inch. 


AA,  Zeiss  . . 

0-0286 

. . 28-6 

. . 0-00126 

A ., 

0-01734 

. . 17-34 

. . 0-00068 

DD,  ,, 

0-004098 

4-098 

. . 0-00016 

One-twelfth  oil  immersion . . 

0-001265 

1-265 

. . 0-00005 

One-twentieth  ,,  ,, 

0-001087 

1-087 

. . 0-000043 

Supposing  that  an  object,  under  examination  with  the  highest  power, 
on  being  measured  is  3*2  eye-piece  divisions  in  length,  then  its  real  length  is 
0-001087  X 3-2  = 0-00348  m.m.,  or  0-000137  inch. 

137.  The  Micromillimetre. — ^When  the  dimensions  of  minute  objects  are 
expressed  either  in  inches  or  in  millimetres  they  require  such  a number 
of  figures  that  it  is  difficult  to  at  first  realise  the  value  of  the  dimension. 
It  has  therefore  been  proposed  to  employ  the  one-thousandth  part  of  a milli 
metre  as  a unit  of  length  for  microscopic  measurements.  This  unit  is  called 
a micromillimetre,  for  which  the  following  abbreviation,  “ mkm.,'"  may 
be  used.  The  mkm.  is  also  sometimes  called  a “ /x  ” pronounced  mu) ; 
its  value  in  inches  is  very  nearly  2 Tii  o o inch.  The  eye-piece  measurements 
given  in  the  preceding  paragraph  have  also  their  values  expressed  in  micro- 
milhmetres. 

138.  Magnification  in  Diameters. — ^There  remains  to  be  explained  a 
convenient  method  of  measuring  the  magnifying  power  of  objectives  and 
eye-pieces.  A common  method  of  expressing  the  value  of  particular  com- 
binations of  these  two  is  to  say  that  they  magnify  so  many  diameters.  A 
moment's  reflection  will  show  that  the  image  seen  with  a microscope  will 
vary  in  actual  dimensions,  according  to  whether  it  be  supposed  to  be  near 
to  or  far  from  the  eye.  The  only  real  measurement,  in  fact,  is  the  visual 
angle  it  subtends.  This  being  the  case,  the  measurement  in  diameters  is 
always  expressed  with  the  understanding  that  the  object  is  supposed  to  be 
ten  inches  from  the  eye. 

Here  for  a moment  a slight  digression  must  be  made.  Most  beginners 
when  looking  through  a microscope  close  the  eye  not  in  use.  This  is  a bad 
plan,  as  the  eyes  are  thereby  much  more  fatigued.  Both  eyes  should  be 
kept  open.  At  first  the  surrounding  objects  are  continually  being  seen 


62 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


with  the  unoccupied  eye,  and  it  is  apparently  a hopeless  case  to  see  the 
object  under  the  microscope  at  all.  Practice  overcomes  this,  but  the  authors 
have  found  the  best  plan  is  to  fix  to  the  microscope  tube  a piece  of  dead  black 
cardboard,  so  that  the  unoccupied  eye  sees  only  a black  surface.  The  object 
will  now  be  observed  with  the  greatest  readiness,  and  probably  not  one 
quarter  the  fatigue.  In  a very  short  time  the  cardboard  shield  may  be 
dispensed  with,  and  the  trained  eyes  so  behave  that  the  one  is  transmitting 
the  view  of  the  microscopic  object  to  the  brain,  while  the  other  is  remaining 
idle  and  resting.  The  student  should  accustom  himself  to  use  either  eye 
indifferently  ; he  will  soon  find  that  he  will  no  more  think  of  closing  one 
eye  when  looking  through  his  microscope  than  he  would  of  tying  his  left 
hand  behind  his  back  before  he  shakes  hands  with  his  right. 

Now,  the  object  of  our  momentary  departure  will  be  evident  ; the 
idle  eye  can,  at  will,  be  used  for  looking  at  something  else,  so  that  the  one 
eye  is  looking  at  the  microscopic  object,  the  other,  if  wished,  at  say  a piece 
of  paper.  Place  the  stage  micrometer  in  focus,  and  fix  a piece  of  stiff  paper 
or  cardboard  as  near  as  possible  to  the  microscope,  at  right  angles  to  its 
axis,  and  ten  inches  from  the  eye-piece.  Look  down  the  tube  with  the  one 
eye,  and  with  the  other  at  the  piece  of  paper.  The  magnified  micrometer 
scale  appears  as  though  drawn  on  the  paper.  Still  using  both  eyes,  trace 
with  a pencil  on  the  paper  the  exact  position  of  each  line  representing  the 
tenths  or  hundredths  of  the  millimetre.  Next  measure  on  the  paper  the 
distance  between  the  two  marks  traced  from,  say,  the  tenths  of  a millimetre  ; 
suppose  that  this  distance  is  five  millimetres,  then  that  particular  combina- 
tion of  eye-piece  and  objective  has  a magnifying  power  of  fifty  diameters. 
Measure  each  other  combination  possible  with  the  various  eye-pieces  and 
objectives  in  your  possession  in  the  same  way. 

139.  Microscopic  Sketching  and  Tracing. — ^The  above  method  of  measur- 
ing is  very  useful,  because  with  small  objects  occupying  a portion  only  of 
the  field,  it  is  possible  to  trace  them  on  the  paper  in  the  manner  described, 
and  such  tracings  are  then  known  to  be  magnified  to  the  extent  ascertained 
by  previous  measurement  as  directed.  Such  sketching  by  actual  tracing 
is  very  desirable  in  microscopic  work,  as  otherwise  the  student  is  extremely 
likely  to  draw  an  object  either  too  large  or  too  small  ; this  is  to  be  avoided, 
as  one  object  of  microscopic  examination  is  to  definitely  ascertain  the  size 
of  objects.  It  is  the  authors'  practice  when  working  without  sketching  to 
note  the  measurements  with  the  eye-piece  micrometer.  When  sketching 
they  make  tracings  of  sufficient  at  least  of  the  object  to  give  its  actual 
dimensions,  by  a process  similar  in  principle  to  that  already  described. 

140.  Camera  Lucida. — ^For  tracing  with  the  microscope  an  appliance 
has  been  invented,  which  is  known  as  a ‘‘  camera  lucida  " ; there  is  also  a 
modification  termed  a neutral  tint  camera.  An  ingenious  combination  of 
eye-piece  and  camera  lucida  in  one  piece  of  apparatus  is  shown  in  section  in 
Fig.  4.  The  principal  portion  of  the  figure  consists  of  the  ordinary  eye- 
piece, a,  h,  with  its  upper  and  lower  lenses,  c,  d ; the  central  dotted  line,  e,  /, 
is  the  direct  axis  of  vision  through  the  microscope.  At  the  top  right  hand 
of  the  figure  is  a glass  prism,  g,  of  peculiar  shape.  The  angles  of  this  are  so 
arranged  that  a ray  of  light,  passing  in  the  direction  h,  i,  is  totally  reflected 
at  i,  in  the  direction  ^,  k,  and  again  at  k is  totally  reflected  in  the  line  k,  1. 
The^result  is  that  the  eye  placed  over  the  aperture  of  the  eye-piece,  at  m,  re- 
ceives both  rays  of  light,  /,  e,  and  h,  i,  k,  I,  which  enter  the  eye  parallel  to 
each  other.  In  consequence,  the  eye  sees  simultaneously  with  the  object 
under  the  microscope  any  other  object  placed  in  the  direction  of  the 
line  1i  ; both  are  combined  and  appear  to  be  in  the  direct  line  of 


THE  MICROSCOPE. 


63 


vision  througli  the  instrument.  Consequently  if  a sheet  of  paper  be  placed 
under  i,  h,  it  and  the  microscope  image  appear  to  the  eye  to  coincide. 

When  wishing  to  use  the  camera,  place 
the  microscope  in  a vertical  position, 
directly  facing  the  source  of  light,  and  turn 
the  camera  so  that  the  prism,  g,  is  at  the 
right-hand  side  (as  figured).  Procure  a 
box  or  other  convenient  stand  of  such  a 
height  that  its  upper  surface,  when  placed 
beside  the  microscope,  is  of  the  same  height 
as  the  microscope  stage.  Place  this  box 
on  the  right-hand  side  of  the  instrument, 
under  the  prism,  g,  so  that  the  line,  ^,  h, 
points  to  it.  For  drawing  purposes  the  most 
convenient  arrangement  is  a small  draw- 
ing “ block  ""  of  hot  pressed  paper,  sheet 
after  sheet  of  which  can  be  removed  as  fin- 
ished. Place  this  on  the  stand,  under  ^,  h, 
and  look  through  the  instrument  ; both 
object  and  paper  should  be  seen  in  com- 
bination ; that  is,  the  image  should  appear 
to  be  superposed  on  the  paper.  To  pro- 
perly get  this  effect  the  paper  and  image 
should,  as  nearly  as  possible,  be  equally 
illuminated.  As  the  paper  is  usually 
brighter  than  the  image,  provision  is  made 
for  cutting  off  some  of  the  light  from  it  by 
introducing  plates  of  neutrah  tinted  glass  in 
the  path  of  ^,  just  below  the  prism  g. 

On  the  other  hand,  the  illumination  of  the  object  may  be  adjusted  by 
means  of  the  reflecting  mirror  of  the  microscope. 

As  a preliminary  to  tracing  with  the  camera,  place  the  stage  micro- 
meter in  focus,  and  the  microscope  and  paper  in ’their  respective  positions. 
Then,  by  means  of  a pencil,  mark  on  the  paper  the  length  of  the  millimetre 
or  fraction  of  the  millimetre,  and  calculate  out  once  for  all  the  magnification 
in  exact  "number  of  diameters.  This  is  very  easily  done,  as  the  lines  of  the 
object  appear  to  be  drawn  on  the  paper  ; the  pencil  point  being  also  seen,  the 
operation  of  tracing  simply  consists  of  going  over  lines  apparently  already 
on  the  paper.  With  the  same  powers  and  eye-pieces,  and  microscope  and 
paper  in  the  same  relative  positions,  the  magnification  is  always  the  same. 
In  actual  sketching  it  is  usually  sufficient  to  trace  in  the  principal  outlines  ; 
the  details  may  then  be  added  with  sufficient  accuracy  by  the  ordinary 
method  of  judging  dimensions  by  the  eye,  as  in  freehand  drawing. 


Fig.  4. — Combination  of  Eye 
Piece  and  Camera  Lucida. 


141.  Microscopic  Counting  : the  Haematimeter. — ^For  certain  purposes 
it  is  highly  important  to  be  able  to  count  the  number^of  small  solid  particles 
suspended  in  a fluid.  Among  them  is  the  counting  of  blood  corpuscles, 
and  of  yeast  cells  suspended  in  water  or  fermenting  liquid.  An  instrument 
was  first  devised  for  this  purpose,  in  order  to  count  blood  corpuscles,  and 
hence  is  called  a haematimeter  ; the  same  appliance  is  adapted  to  the 
•counting  of  yeast  cells,  and  is  illustrated  in  Fig.  5.  The  instrument  consists 
of  a stout  glass  slide,  on  which  is  cemented  a cover-glass  with  a circular 
opening,  thus  constituting  a cell.  On  the  glass  slide,  and  in  the  centre  of 
this  cell,  is  arranged  a raised  circle  of  glass,  on  which  is  engraved  a series 
of  lines  at  right  angles  to  each  other,  thus  marking  its  surface  off  into  a 
number  of  squares.  A representation  of  this  part  of  the  apparatus  is  given 


64 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


on  the  left  of  the  figure,  showing  its  appearance  when  viewed  through  the 
microscope.  Each  of  the  larger  squares  has  an  area  of  4^^  (0-0025)  square 
millimetre.  The  inner  circle  of  glass,  and  the  outer  glass,  are  so  arranged 
that  the  former  is  exactly  m.m.  the  thinner  ; so  that  when  the  cover- 


r-l 

/- 

r 

i- 

d 

7 

V — 

-1 

7 

- 

Fig.  5. — The  H^matimetee. 

glass  is  brought  down  into  absolute  contact  with  the  outer  glass,  the  space 
between  the  lower  surface  of  one  and  the  upper  of  the  other  is  exactly  0-1 
m.m.  in  thickness.  Therefore  the  cubic  contents  of  the  space  above  each 
square  on  the  inner  glass  is 

0-0025  X 0-1  = 0-00025  = cubic  m.m. 

To  perform  a counting  operation  on  yeast,  for  example,  an  average 
sample  must  be  taken,  diluted,  and  shaken  up  until  the  cells  are  uniformly 
distributed  through  the  liquid.  Hansen  considers  that  the  liquid  most 
suitable  for  this  purpose  is  dilute  sulphuric  acid,  1 part  to  10  of  water  r 
for  yeast  the  authors  prefer  to  employ  1 part  sulphuric  acid,  1 part 
glycerin,  and  8 of  water.  The  viscid  nature  of  the  glycerin  enables 
the  liquid  to  keep  the  cells  uniformly  suspended  through  it  for  a longer 
time.  The  method  of  employing  the  hsematimeter  is  best  explained  by 
giving  an  actual  example.  From  a sample  of  compressed  yeast,  0*25  grams 
were  weighed  off  and  made  up  to  50  c.c.  with  dilute  glycerin  and  sulphuric 
acid.  The  yeast  was  broken  down  and  thoroughly  mixed  with  the  liquid  by 
violent  shaking  for  some  time  in  a flask.  A droplet  was  then  removed  by 
means  of  a pointed  glass  rod,  and  placed  on  the  centre  of  the  glass  of  the 
haematimeter,  and  immediately  covered  with  the  cover  : this  is  held  in 
close  contact  either  by  a pair  of  small  spring  clips  or  by  a weight  put  on. 
(The  minute  drop  for  this  purpose  must  not  be  more  than  sufficient  to- 
nearly  fill  the  space  between  the  two  glass  surfaces  : it  must  not  be  enough 
to  run  over  into  the  outside  annular  space.  The  apparatus  is  placed 
aside  in  a horizontal  position  to  rest  sufficiently  long  for  the  suspended  cells 
to  fall  to  tlie  bottom  of  the  layer  of  liquid.  The  yeast  cells  having  settled 
down,  say  in  ten  minutes,  place  the  haematimeter  on  the  horizontal 
stage  of  the  microscope , and  prepare  to  commence  counting,  using 
about  /j-incli  objective  (Zeiss  D).  The  yeasb  cells  will  be  seen  lying 
on  the  engraved  squares,  some  within  the  squares,  and  others  directly  on 
the  dividing  lines.  Commence  counting  the  cells  within  the  top  left-hand 
square,  and  make  a note  of  the  number,  then  go  on  along  the  line,  come  back, 
and  count  those  on  the  squares  of  the  next  line,  and  so  on.  The  cells  lying 
on  the  lines  must  also,  of  course,  be  counted,  but  only  once  ; that  is,  all 


THE  MICROSCOPE. 


65 


lying  on  the  horizontal  lines  must  be  counted  in  the  squares  above  them 
and  all  on  vertical  lines  in  the  squares  to  the  right  of  them.  The  counting 
must  be  continued  until  a sufficient  number  of  squares  have  been  taken  to 
give  a true  average.  By  experiment  it  should  be  ascertained  how  many 
squares  must  be  counted  in  order  that  an  additional  number  has  no  influence 
on  the  average  obtained.  It  is  usually  sufficient  to  count  some  50  or  60 
of  the  squares.  It  is  convenient  to  have  the  liquid  of  such  a degree 
of  dilution  that  about  8-10  cells  occur  in  each  square.  Approximately  the 
accidental  errors  amount — 

by  counting  £000  cells,  to  5 per  cent,  of  the  total  result. 

„ 1250  „ 2 

,,  5000  ,5  1 5j  >)  jj 

In  the  experiment  being  described,  100  squares  were  counted  and 
contained  738  yeast  cells. 

Now  the  space  above  each  square  = 0-00025  cubic  mm. 

Therefore  100  spaces  = 0'025  cubic  m.m.,  and  contain  738  cells. 
Therefore  4000  spaces  = POOO  cubic  m.m.,  and  contain  7 '38  X 4000  = 29,520 
cells. 

Therefore  1 c.c.  = 1000  cubic  m.m.,  and  contains  29,520  X 1000  = 

29,520,000  cells. 

But  1 c.c.  contained  0*005  gram  of  yeast,  and  therefore  1 gram  contains 
29,520,000  X 200  = 5,904,000,000  cells. 

But  1 lb.  avoirdupois  = 453*59  grams,  and  therefore  1 lb.  of  the  yeast 
contained  : — • 

5,904,000,000  X 453*59  = 2,677,995,360,000  cells. 

The  smaller  grained  starches  may  also  be  counted  in  the  same  manner. 

142.  — The  methods  of  using  the  microscope  having  been  briefly  described, 
directions  for  its  use  for  special  purposes  will  be  given  as  occasion  arises. 
For  fuller  descriptions  of  the  instrument  itself,  its  accessories  and  the 
method  of  using  them,  the  student  is  referred  to  one  of  the  many  excellent 
works  already  published  on  the  subject. 

143.  Polarisation  of  Light. — ^There  are  many  substances  which  exert  a 
special  action  on  “ polarised  light”  ; among  these  are  a variety  of  crystalline 
compounds,  and  certain  organic  bodies.  It  will  be  necessary  at  this 
stage  to  give  a short  description  of  the  nature  of  a ray  of  light,  and  the  way 
in  which  its  character  may  be  altered  by  the  action  of  these  substances 
just  mentioned.  As  is  well  known,  light  travels  in  straight  lines  called  rays. 
The  actual  motion  of  such  a ray  of  light  is  somewhat  like  to  that  of  a sea- 
wave,  or  the  ripples  produced  on  the  smooth  surface  of  a pond  by  throwing 
a stone  therein.  In  waves,  the  water  itself  does  not  move  forward,  but  only 
the  undulating  motion  of  the  surface  ; this  is  readily  seen  by  floating  a 
cork  on  the  water  ; each  little  wave  in  its  passage  onward  simply  raises 
and  depresses  the  cork,  but  leaves  it  in  the  same  position  as  it  found  it. 
Light,  then,  also  travels  in  waves,  these  waves  being  undulations  in  a sub- 
stance filling  all  space,  and  known  by  the  name  of  “ ether."'  The  waves  of 
light  differ  remarkably  in  one  particular  frorh  those  on  the  surface  of  water  ; 
the  undulatory  motion  in  the  latter  is  simply  up  and  down,  or,  to  use  the 
scientific  term,  in  a vertical  plane.  If  the  actual  movements  of  the  ether 
in  a ray  of  light  could  only  be  rendered  visible,  a much  more  complicated 
motion  would  be  perceived.  Just  as  in  the  case  of  the  water  wave,  the 
particles  would  move  across,  or  transversely  to,  the  direction  of  the  path 
of  the  ray.  Some  of  the  particles  would  rise  and  fall  like  those  in  the  water 
wave,  but  others  would  swing  from  side  to  side,  or  horizontally  instead 
of  vertically  ; further  than  this,  others  again  would  vibrate  at  every  inter- 


66 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


mediate  angle.  This  condition  of  things  is  expressed  in  the  statement 
that  the  undulations  of  a wave  of  light  are  in  a plane  transverse  to  the  path 
of  the  ray,  and  that  the  ether  particles  vibrate  in  every  direction  in  that 
plane. 

For  our  present  purpose  it  will  be  sufficient  to  regard  the  wave  of  light 
as  composed  of  two  sets  of  vibrations,  the  one  vertical,  and  the  other  hori- 
zontal, and  therefore  at  right  angles  to  each  other  ; the  intermediate  vibra- 
tions may  be  ignored.  The  character  of  the  undulations  of  a wave  of  hght 
is  not  greatly  altered  by  passing  through  glass,  water,  and  many  other 
bodies  ; the  same  does  not,  however,  hold  good  with  all  transparent  sub- 
stances— of  these  one  of  the  most  striking  is  a mineral  named  tourmaline. 
Let  two  thin  plates  be  cut  from  a crystal  of  this  substance  in  a certain  direc- 
tion ; on  examination  each  is  seen  to  be  fairly  transparent.  Let  one  be 
placed  over  the  other,  and  then  slowly  twisted  round.  In  one  particular 
position  light  passes  through  them  both  as  readily  as  through  either  taken 
singly  ; but  as  one  of  the  pair  is  turned  round,  less  and  less  light  is  trans- 
mitted ; until,  when  it  has  been  rotated  through  an  angle  of  90  degrees, 
no  light  whatever  passes.  As  the  revolution  is  continued,  the  plates  allow 
iinore  and  more  light  to  pass  ; until,  when  an  angle  of  180  degrees  has  been 
reached,  the  combination  of  two  plates  is  again  transparent.  A further 
revolution  of  90  degrees  once  more  causes  opacity.  This  peculiar  effect  is 
due  to  the  fact  that  tourmaline  plates,  such  as  described,  permit  the 
passage  through  them  of  only  the  vibrations  of  light  in  one  plane,  so  that 
the  ray  of  light,  after  passing  through  the  tourmaline,  instead  of  having  its  vibra- 
tions in  all  directions  of  the  plane,  has  them  occurring  in  one  direction  only  ; the 
ray  may  then  be  compared  to  a water  wave.  Such  a ray  of  light  is  said  to  be  “ polar- 
ised,"' and  the  change  effected  is  termed  the  “ polarisation  of  light."’ 

The  tourmaline  plate  may  be  compared  to  a sieve  composed  of  a set 
of  wires  in  but  one  direction.  Using  this  similitude,  only  those  vibrations 
which  are  in  the  same  direction  as  the  wires  of  the  sieve  succeed  in  effecting 
a passage.  The  second  tourmaline  plate  being  set  so  that  its  wires  are 
parallel  to  those  of  the  first,  the  light  which  passed  through  the  one  succeeds 
£ilso  in  passing  through  the  other.  But  when  the  second  tourmaline  is 
turned  at  right  angles  to  the  first,  then  the  light  which  passed  through  the 
(One  is  cut  off  by  the  other,  and  so  the  two  together  refuse  to  transmit  any 
light  whatever. 

Persons  who  are  acquainted  with  the  beautiful  mineral  known  as  Iceland 
spar,  know  that  when  a single  dot  is  looked  at  through  a piece  of  the  spar, 
it  is  seen  double  ; this  is  due  to  the  fact  that  the  spar  splits  the  ray  of  light 
into  two  distinct  rays  ; further,  the  light  of  each  of  these  sub-rays  is  polar- 
ised in  such  a manner  that  the  plane  of  polarisation  (that  is,  the  direction 


Fig.  6. — Nicol’s  Prism. 

in  which  the  vibrations  occur)  of  the  one  ray  is  at  right  angles  to  that  of  the 
other.  When  pieces  of  Iceland  spar  are  cut  and  re-joined  in  a particular 
manner,  as  shown  by  the  oblique  line  in  Fig.  6,  they  transmit  the  one  only 
of  these  two  rays,  the  other  being  lost  by  internal  refiection  within  the 
crystal.  Such  pieces  of  spar  are  termed  “ NicoFs  prisms,"  and  may  be  used 
for  the  same  purpose  as  .the  tourmaline  plates  ; they  have  the  great  advan- 
tage of  being  composed  of  material  as  transparent  as  glass,  while  the  tourma- 
line is  usually  only  semi-transparent,  apart  from  its  polarising  properties. 


THE  MICROSCOPE. 


67 


The  first  NicoPs  prism  placed  in  the  path  of  a ray  of  light  is  termed  the 
polariser,  because  it  effects  the  polarisation  ; the  second  is  known  as  the 
analyser,  because  it  enables  us  to  determine  the  direction  of  the  plane  of  the 
polarised  ray.  The  attachments  for  a NicoPs  prism  are  shown  in  Fig.  7, 
which  is  an  illustration  of  the  polariser  and  analyser  of  a microscope.  Tlie 
polariser,  in  use,  is  fitted  to  the  sub-stage,  and  the  analyser  to  the  eye-piece, 


Fig.  7. — Polariser  and  Analyser  of  Microscope. 


Returning  again  to  the  similitude  of  the  sieves,  suppose  that,  with  the 
two  at  right  angles  to  each  other,  it  were  possible  to  take  the  light  after  it 
had  passed  through  the  one,  and  was  thus  polarised,  and  twist  or  rotate  its 
plane  of  polarisation  through  an  angle  of  90°  before  it  came  to  the  second,  it 
would  evidently  then  be  able  to  pass  through  that  also.  Certain  substances 
possess  this  remarkable  property  : among  those  of  immediate  interest  in 
connection  with  the  present  subject  are  starch,  sugar,  and  other  of  the  carbo- 
hydrates. It  is  further  found  that  while  some  compounds  twist  the  polar- 
ised ray  to  the  right,  or  in  the  direction  of  the  hands  of  a watch,  others 
rotate  polarised  light  to  the  left.  If  two  NicoPs  prisms  were  so  arranged 
as  to  give  absolute  darkness,  and  then  a plate  of  sugar  were  placed  between 
them,  light  would  be  transmitted.  If  the  analyser  were  next  turned  around 
in  a right-handed  direction,  the  point  of  absolute  darkness  would  again 
be  reached,  and  then  by  measuring  the  angle  of  rotation,  the  number  of 
degrees  through  which  the  plane  of  polarisation  of  light  had  been  rotated 
by  the  sugar  could  be  ascertained.  Instruments  are  constructed  for  the 
purpose  of  making  this  measurement  with  great  delicacy,  and  are  termed 
“ polarimeters.''  The  exact  point  at  which  maximum  light  and  darkness  is 
reached  during  the  rotation  of  the  analyser  cannot  be  observed  with  great 
accuracy  ; recourse  is  therefore  had  to  observing  some  of  the  other  char- 
acteristics of  polarised  light  more  easily  detected  by  the  eye.  In  the  analytic 
section  of  this  work,  an  explanation  is  given  of  the  principles  which  guide 
chemists  in  the  application  of  the  rotation  of  the  plane  of  the  polarisation  of 
light  by  sugar  and  other  bodies  to  their  estimation  ; a practical  description 
then  follows  of  one  of  the  best  forms  of  polarimeter  and  the  method  of  using 
it.  For  microscopic  purposes  a polariser  is  fitted  underneath  the  stage, 
and  an  analyser  either  within  the  body  of  the  tube  or  over  the  eye-piece. 
The  object  under  examination  is  thus  illuminated  by  polarised  light.  For 
further  information  on  the  polarisation  of  light,  the  student  is  referred  to 
GanoFs,  or  some  other  standard  work  on  physics. 


CHAPTER  V. 


CONSTITUENTS  OF  WHEAT  AND  FLOUR. 

MINERAL  AND  FATTY  MATTERS. 

144.  Construction  of  Wheat  Grain.— Having  giving  a brief  outline  of 
the  principles  and  theory  of  Chemistry,  in  so  far  as  they  are  more  or  less 
connected  with  the  present  subject,  our  next  object  must  be  to  describe  the 
chemical  properties  of  the  different  compounds  found  in  the  grain,  and  to 
trace  them  out  in  the  history  of  the  flour  and  offal.  The  cereals,  to 
which  wheat  belongs,  is  the  name  given  to  the  grasses  which  have  been  cul- 
tivated for  use  as  food.  The  grain,  as  is  of  course  well  known,  is  the  seed  of 
the  plant  ; although  not  strictly  chemical  information,  it  will  be  well  to 
give  here  a short  description  of  its  various  parts.  The  most  important 
portion  of  the  seed  is  the  embryo  or  germ  ; this,  which  is  a body  rich  in 
fatty  matters,  is  that  part  of  the  seed  which  grows  into  the  future  plant. 
The  interior  of  the  seed  contains  a q^uantity  of  starch  and  other  compounds, 
designed  for  the  nutrition  of  the  young  plant  during  its  earliest  stages  of 
growth.  The  whole  is  enclosed  in  an  envelope,  made  up  principally  of 
woody  fibre,  and  arranged  in  a series  of  coats,  one  outside  the  other,  some- 
what like  those  of  an  onion,  only  on  a much  finer  scale.  During  the  process 
of  milling,  the  grain  is  divided  into  flour  and  what  is  technically  knovn  as 
offal.  This  latter  substance,  or  group  of  substances,  includes  the  germ, 
bran,  pollard,  etc.  The  bran  and  pollard  are  the  different  skins  of  the  grain 
broken  up  into  fragments  of  various  sizes.  This  department  of  the  subject 
will  be  dealt  with  fully  in  a subsequent  part  of  the  work. 

145.  Constituents  of  Wheat.— A large  number  of  chemical  compounds 
may  be  obtained  from  grain  ; these  naturally  divide  themselves  into  Mineral 
or  Inorganic  Constituents,  and  Organic  Constituents.  The  inorganic  por- 
tions of  wheat  consist  of  water  and  the  mineral  bodies  found  in  the  ash. 
Tlie  organic  compounds  may  be  conveniently  grouped  into— fatty  matters, 
starch,  and  allied  bodies  having  a similar  chemical  composition,  and  nitro- 
genous bodies  or  proteins.  Of  these  substances  the  fats  have  the  simplest 
composition,  next  come  the  starchy  bodies,  and  lastly,  the  proteins,  whose 
constitution  is  extremely  complex. 

146.  Mineral  Constituents.— The  properties  of  water  are  already  suffi- 
ciently described  ; the  actual  amount  present  in  grain  varies  from  about  10 
to  15  per  cent.  In  sound  wlieats  and  flours  there  is  no  perceptible  damp- 
ness, the  water  being  chemically  combined  with  the  starch,  which  body 
probably  exists  in  grain  as  a hydroxide.  The  other  mineral  constituents  are 
usually  obtained  by  heating  the  powdered  grain  to  faint  redness  in  a current 
(>f  air  ; the  organic  bodies  burn  away  and  leave  an  ash  consisting  of  the 


MINERAL  AND  FATTY  MATTERS. 


69 


inorganic  substances  present.  The  ash  of  wheat  has  been  made  the  subject 
of  prolonged  investigations  and  researcli,  conducted  principally,  however, 
from  an  agricultural  point  of  view.  Land  being  impoverished  by  the  growth 
of  crops,  the  constitution  of  the  ash  of  wheaten  grain  and  straw  is  an  indica- 
tion of  what  mineral  matters  are  removed  from  the  soil  by  wheat  crops,  and 
therefore  also  affords  information  as  to  what  additions  have  to  be  made  to 
an  exhausted  soil  in  order  to  replenish  its  necessary  mineral  components. 
Lawes  and  Gilbert  have  from  time  to  time  published  elaborate  tables  of 
results  obtained  on  their  experimental  farm  at  Rothampsted  ; the  following 
table  is  abstracted  from  a communication  of  theirs  to  the  Chemical  Society 
{Chem.  Soc.  Jour.,  vol.  xlv.,  page  305  et  seq.).  It  gives  the  composition  of 
the  grain-ash  of  wheat,  grown  on  the  same  land,  in  four  characteristic  sea- 
sons— 1852,  1856,  1858,  and  1863  ; the  land  being  treated  with  farmyard 
manure  : — 


Harvests — 

1852. 

1856. 

1858. 

1863. 

Weight  per  bushel  of  grain,  lb. . . . 

58-2 

58-6 

62-6 

63-1 

Percentage  Composition  of  Ash. 

I 

Iron  Oxide,  Fe203 

0-95 

0-86 

0-90 

0-43 

Lime,  CaO  . . 

2-79 

I 2-53 

2-61 

2-34 

Magnesia,  MgO 

12-77 

11-71 

11-17 

11-41 

Potash,  K2O 

27-22 

j 29-27 

31-87 

31-54 

Soda,  Na25 

0-45 

0-42 

0-28 

0-66 

Phosphoric  Anhydride,  P2O5 

54-69 

54-18 

51-88 

52-04 

Sulphuric  Anhydride,  SO3 

0-14 

0-23 

0-75 

0-93 

Chlorine,  CI2 

trace 

0-07 

0-06 

trace 

Silica,  Si02 . . 

0-99 

0-75 

0-49 

0-65 

Total 

100-00 

100-02 

100-01 

100-00 

The  ash  constitutes  about  1 *5  per  cent,  of  wheat,  and  about  0 4 per  cent,  of 
the  finished  flour,  while  bran  yields  from  5 to  7 per  cent,  of  ash.  It  will  be 
noticed  that  more  than  half  the  wheat  ash  consists  of  anhydrous  phosphoric 
acid  ; this  is  principally  in  combination  with  potash,  forming  potassium 
phosphate.  The  magnesia  is  also  present  as  a salt  of  phosphoric  acid.  The 
greater  part  of  wheat  ash,  therefore,  consists  of  potassium  phosphate,  and 
is  soluble  in  water. 

147.  Composition  of  the  Ash  of  a Wheat  and  its  Mill  Products,  Teller.— 

The  following  series  of  ash  analyses  was  made  for  the  purpose  of  obtaining 
some  further  information  concerning  the  distribution  of  various  ash  ingre- 
dients in  the  wheat  grain  and  in  the  different  products  of  modern  flouring 
mills.  The  figures  given  in  the  table  indicate  in  per  cent,  of  total  ash,  the 
amount  of  each  constituent  named. 


70 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Constituents. 

Patent 

Plour. 

straight 

Flour. 

Low 

Grade. 

Dust 

Room. 

Ship 

Stuff. 

Bran. 

Wlieat. 

Silica  . . 

2-33 

1-28 

0-50 

1-34 

0-49 

0-97 

' 1-04 

xHumina 

0-41 

0-15 

0-12 

0-04 

0-18 

0-07 

0-11 

Ferric  Oxide.  . 

0-47 

0-26 

0-25 

i 0-30 

0-37 

0-27 

0-27 

Potash 

38-50 

36-31 

32-27 

30-85 

, 28-03 

28-19 

29-70 

Soda  . . 

0-00 

0-00 

0-00 

0-00 

0-00 

0-00 

0-00 

Lime  . . 

5-59  ! 

5-65 

4-51 

3-53 

2-80 

2-50 

3-10 

Magnesia 

4-39 

6-44 

9-33 

12-90 

13-27 

14-76 

13-23 

Phosphoric  Acid 

48-05 

49-32 

53-10 

49-94 

54-62 

52-81 

52.14 

Sulphur  Trioxide 

0-16 

0-52 

0-00 

0-58 

0-00 

0-10 

0-22 

Chlorine 

i 

— 

— 

- — • 

— 

0-01 

0-01 

Zinc  Oxide  . . 

1 

0-04 

— 

0-46 

0-36 

0-27 

0-24 

Total 

99-90 

99-97 

1— 1 

o 

o 

6 

00 

99-94 

100-12 

99-95 

100-06 

Per  cent  total  ash  in  ; 
each . . . . . . , 

1 

CO 

o 

040 

1 

0-70 

2-50 

3-08 

5-25 

1-62 

x\mong  the  variations  in  composition  in  the  ash  from  different  parts  of 
the  wheat  grain,  the  most  noticeable  are  the  very  marked  increase  in  the 
proportion  of  potash  and  lime  toward  the  interior  of  the  grain,  and  the  still 
greater  decrease  in  the  proportion  of  magnesia  in  the  same  direction,  that 
is,  from  the  bran  to  the  whitest  flour.  {Bulletin,  Arkansas  Aqric.  Expt.  Station  . 
1896.) 

148.  Organic  Constituents  : Fatty  Matters. — Of  the  numerous  organic 
bodies  found  in  wheat,  fat  has  not  been  chosen  as  the  first  to  be  described 
because  of  its  importance  as  a grain  constituent,  but  because  it  has  the 
simplest  composition  of  the  organic  bodies  present,  and  therefore  may  fitly 
serve  as  an  introduction  to  the  chemistry  of  the  more  complicated  com- 
pounds to  follow.  All  grains  contain  more  or  less  fat  ; rice  has  the  least 
quantity,  viz.  0*1  per  cent.  ; maize  and  oats  have  respectively  4*7  and  4*6 
per  cent.  ; wheat  occupies  a medium  position  with  a percentage  of  1 -2  to 
1*5.  The  fat  of  wheat  is  not  equally  disseminated  through  the  grain,  but 
is  almost  entirely  contained  in  the  germ  and  husk  or  bran.  An  analysis  by 
Church  gives  the  quantity  of  fat  in  “ fine  wheat  flour  ""  as  0*8  ; it  is,  how- 
ever, doubtful  if  this  analysis  were  made  since  the  time  when  the  problem 
of  degerming  flour  has  received  so  much  attention  from  the  miller. 

It  has  been  already  explained  that  the  fats  are  salts  of  certain  acids, 
with  glycerin  as  a base.  They  are  characterised  by  their  unctuous  nature, 
and  by  leaving  a greasy  stain  on  paper  or  linen.  Fats  are  insoluble  in  water, 
and  from  their  low  specific  gravity  float  on  the  surface  of  that  liquid.  On 
the  other  hand,  all  fatty  bodies  dissolve  readily  in  either  ether  or  light 
petroleum  spirit.  As  food  stuffs,  the  fats  occupy  a high  position  ; in  tables 
giving  the  relative  nutritive  value  of  different  articles  of  food,  fat  heads  the 
list.  -If  this  were  the  only  point  to  be  considered,  the  presence  of  fats  in 
v'heat  and  flour  would  be  highly  advantageous.  They  have,  unfortunately, 
one  great  drawback,  and  that  is  that  they  become  rancid  on  standing.  This 
effect  is  particularly  noticeable  in  flour  imperfectly  freed  from  germ.  The 
rancidity  is  due  to  slow  oxidation  of  certain  constituents  of  the  fat  ; this 
change  may  proceed  sufficiently  far  to  seriously  affect  the  flavour  of  the 


MINERAL  AND  FATTY  MATTERS. 


71 


flour,  without  the  fat  as  a whole  being  very  greatly  changed.  The  fat  of 
wheat  is  of  a light  yellow  colour,  melts  at  a low  temperature,  and  gradually 
darkens  in  colour  on  being  kept.  This  change  proceeds  rapidly  in  the  fat 
when  maintained  at  a temperature  of  70  or  80°  C. 

Kdnig  states  that  the  fat  of  rye,  a grain  very  similar  to  wheat,  has  the 
follovdng  composition  : — 

Glycerin  . . . . . . . . . . 1 *30  per  cent. 

Oleic  acid  . . . . . . . . ..  90*60  ,, 

Palmitic  and  stearic  acids  . . . . . . 8*10  ,, 

According  to  Konig,  therefore,  the  fat  of  rye  consists  largely  of  free 
fatty  acids,  the  glycerin  present  being  insufficient  to  neutralise  but  a small 
])roportion  of  the  acids  present. 

Stellwaag  states  that  the  fat  of  barley  as  extracted  by  ether  has  the 
following  composition  : — 


Free  fatty  acids 
Neutral  fats 
Lecithin  . . 
Cholesterin 


3*62  per  cent. 
7*78  „ 

4-24 


An  examination  of  wheat  fat  in  the  authors'  laboratory  gave  the  follow- 
ing results  : A sample  of  perfectly  fresh  wheat  germs  was  obtained  from 
the  miller  and  extracted  repeatedly  with  light  petroleum  spirit  in  the  cold. 
The  extract  was  filtered,  the  spirit  distilled  off,  and  the  residue  heated  very 
gently  until  completely  free  from  the  odour  of  petroleum.  A light  yellow 
oil,  which  in  twenty-four  hours  deposited  a trace  of  crystalline  fat,  was  the 
result.  The  following  analytic  data  were  obtained  on  the  thoroughly  mixed 
oil  and  fat  : — 

Free  fatty  acids  . ..  ..  ..  5*92  per  cent. 

Neutral  fats  . . . . . . . . . . 94*08  ,, 


10000 

More  detailed  analysis  gave  the  following  results  : — 

Lower  fatty  acids  (reckoned  as  butyric)  . . 0*11  per  cent. 

Higher  fatty  acids  (palmitic,  stearic,  etc.)  20*72  ,, 

Oleic  acid  . . . . . . . . . . 52*24  ,, 

The  fat  completely  saponified  very  readily. 

Spaeth  (p.  233,  Analyst,  1896)  gives  the  following  analytic  data  as  to 
the  properties  of  wheat  fat  : — 

Specific  Gravity  at  100°  C.  (water  at  15=°  1)  ..  0*9068 


Melting  Point  of  Fatty  Acids  . . . . . . 34° 

Saponification  Value  . . . . . . . . ..  166*5 

Iodine  Value  ..  ..  ..  ..  ..  ..  101*5 

Reichert  Meissl  Value  . . . . . . . . . . 2*8 

Refractive  Index  at  25°  C.  ..  ..  ..  1*4851 


,,  j,  on  Zeiss's  Refractometer  Scale  92*0 

149.  Wheat  Oil : de  Negri,  and  Frankforter  and  Harding. — ^A  somewhat 
exhaustive  examination  of  the  oil  of  wheat  has  been  made  by  de  Negri, 
who  found  the  separated  germs  of  wheat  to  contain  12*5  per  cent,  of  fatty 
matter,  of  which  8 per  cent,  could  be  extracted  by  petroleum  spirit.  On 
removal  of  the  solvent  by  distillation  in  a vacuum,  there  remained  a clear 
yellow-brown  mobile  oil  having  a peculiar  smell  resembling  that  of  wheat. 


72  THE  TECHNOLOGY  OF  BREAD-MAKING. 

This  oil  solidifies  at  15°  C.  It  is  soluble  in  ether,  petroleum  ether,  chloroform, 
and  carbon  disulphide  ; but  is  insoluble  in  cold  absolute  alcohol,  though 
soluble,  however,  in  thirty  parts  of  hot  alcohol.  Glacial  acetic  acid  dis- 
solves at  65°  C.  an  equal  volume  of  oil.  It  is  only  slowly  saponified  by 
alcoholic  potash. 

Colour  reactions  : Haydenreich’s  reaction,  orange-yellow  with  violet 
spots.  Brulle’s  reaction,  red  tinge  becoming  blood  red.  Schneider’s  and 
also  Baudoin’s  reaction  gave  no  colour.  Becchi’s  as  well  as  Milliau’s  reac- 
tion gave  a pale  brown  colour.  The  oil  easily  turns  rancid.  After  standing 
a year  a sample  contained  43*86  per  cent,  of  free  acid  calculated  as  oleic 
acid.  Germs  of  different  origin  were  found  to  give  oils  with  varying  con- 

St  3;Tlt  S 

Frankforter  and  Harding  state  that  the  oil  extracted  from  the  germ 
by  ether  has  a golden  yellow  colour,  and  a characteristic  odour  of  freshly 
ground  wheat.  Warmed  to  100°  C.,  the  oil  becomes  reddish-brown.  It  is 
a non-drying  and  not  readily  oxidisable  oil.  The  following  are  the  more 
important  constants  and  particulars  of  composition  as  determined  by  de 
Negri,  and  Frankforter  and  Harding  respectively 


Data. 


Specific  Gravity  at  0°  C.  . . 

„ . 15°C 

Solidification  Point 
Melting  Point  of  Fatty  Acids 
Solidification  Point  of  Fatty  Acids 
Saponification  Value 
Iodine  Value  of  Oil 

Fatty  Acids 

Refractometer  Value  (Zeiss-Wollny) 

Free  Acid  calculated  as  Oleic  Acid 

Glycerol  (glycerin) . . 

Lecithin 

Paracholesterol 


De  Negri. 

Frankforter 
and  Harding. 

_ 

0*9374 

0*9245 

0*9292 

15°  C. 

— 

39*5°  C. 

— 

29*7°  C. 

— 

182*81 

188*83 

115*17 

115*64 

123*27 

— 

74*5  I 

( 4*07* 

5*65  1 

1 

1 20*46 

1 

7*37 



1*99 

— 

2*47 

The  figure  marked  by  an  asterisk  is  the  amount  per  cent,  of  potassium 
hydroxide,  KHO,  required  to  neutralise  the  free  acid.  This  figure  X 5*027 
= the  acidity  calculated  as  oleic  acid.  It  will  be  seen  that  this  sample  is 
about  four  times  as  acid  as  that  of  de  Negri.  But  like  other  oils,  the  acidity 
varies  considerably  with  age  and  other  conditions,  {de  Negri,  Chem.  Zeit 
1898,  22,  976,  and  Frankforter  and  Harding,  Jour.Amer.  Chem.Soc.,  1899, 
'758.) 

it  is  unusual  to  find  germ  oil  with  any  brown  tint  as  described  by  de 
Negri,  pure  germ  is  very  pale  yellow  in  colour  and  so  also  is  the  oil  extracted 
therefrom.  Possibly  the  germ  on  which  de  Negri  worked  contained  a slight 
.amount  of  bran  from  which  the  oil  derived  its  colour. 

Further  explanation  of  the  various  analytic  data  will  be  given  when 
•dealing  more  fully  with  fats  in  the  confectionery  section  of  this  work,  Chapter 
XXXIII. 

Experimental  Work. 

150.  The  student  who  proposes  to  master  for  himself  the  contents  of 
ithis  work,  should  endeavour  to  verify  as  many  as  possible  of  the  various 


MINERAL  AND  FATTY  MATTERS. 


73 


statements  and  descriptions  by  direct  experiment.  The  following  outline 
of  experimental  work  is  intended  as  a laboratory  course  of  study  on  the 
subject. 

151.  Mineral  Constituents. — ^Take  a small  quantity  of  whole  wheaten 
meal,  heat  it  to  redness  over  a bunsen  in  a shallow  platinum  capsule  or 
basin.  At  first  the  volatile  constituents  of  the  grain  burn  with  flame,  leav- 
ing a black  mass  of  carbon  and  ash.  Continue  the  application  of  heat  until 
the  carbon  entirely  burns  away,  leaving  behind  a greyish  white  ash.  To 
this,  when  cool,  add  water  ; notice  that  most  of  it  dissolves  ; add  a few 
drops  of  hydrochloric  acid,  filter  the  solution,  and  make  a qualitative  analy- 
sis of  it  ; test  specially  for  calcium,  magnesium,  potassium,  and  phosphoric 
acid.  It  is  well  to  test  direct  for  these  two  latter  constituents  in  separate 
small  portions  of  ash.  To  test  for  potassium,  dissolve  up  a portion  in  hydro- 
chloric acid,  filter  and  add  a few  drops  of  platinum  chloride  to  some  of  the 
solution  in  a watch-glass,  the  presence  of  potassium  is  demonstrated  by  the 
formation  of  the  yellow  precipitate  of  the  double  chloride  of  platinum  and 
potassium.  Dissolve  another  portion  of  the  ash  in  nitric  acid,  filter  and 
add  nitric  acid  and  ammonium  molybdate  solution  ; after  standing  for 
some  time  in  a warm  place,  phosphoric  acid  throws  down  a canary-yellow 
precipitate. 

152.  Fat. — ^In  a tightly  corked  or  stoppered  bottle,  shake  up  together 
some  wheat  meal  and  ether  (or  light  petroleum  spirit),  allow  the  mixture  to 
stand  for  an  hour,  giving  it  an  occasional  shake  meanwhile.  At  the  end  of 
that  time  filter  the  solution  through  a paper  into  a clean  evaporating  basin 
and  allow  it  to  spontaneously  evaporate.  Notice  that  it  leaves  a small 
quantity  of  fat  in  the  basin.  Remember  that  the  greatest  care  must  be 
taken  in  all  experiments  with  ether  to  avoid  its  taking  fire.  It  is  best  to 
make  this  experiment  in  a room  where  there  are  no  lights. 


CHAPTER  VI. 

THE  CARBOHYDRATES. 


153.  Definition  of  “ Carbohydrates.” — ^This  name  has  been  applied  to  a 
class  of  bodies  composed  of  carbon,  hydrogen,  and  oxygen,  in  which  the 
latter  two  elements  are  present  in  the  same  proportion  as  in  water,  namely, 
two  atoms  of  hydrogen  for  every  one  of  oxygen.  Thus,  for  example,  starch 
contains  to  the  six  atoms  of  carbon,  ten  atoms  of  hydrogen  to  five  atoms  of 
oxygen.  The  carbohydrates  comprise,  among  their  number,  bodies  differing 
considerably  in  physical  appearance  and  character,  but  yet  exhibiting  signs 
of  close  chemical  relationship.  Subjoined  is  a table  of  the  more  important 
carbohydrates,  arranged  into  three  groups,  according  to  their  empirical 
or  simplest  possible  formulae  : — 


Classification  of  Carbohydrates. 


1.  Glucoses,  Hexoses 
(C6H12O6). 

2.  Sucroses  or  Saccharoses, Di-hexoses 
(C12H22O11). 

3.  Amyloses,  Poly-hexoses 
n (C6H10O5). 

+ Dextrose 
— La3vulose 
Galactose 

+Cane  Sugar 

4- Lactose 
+ Maltose 

+ Starch 
-J- Dextrin 
Cellulose 

Gums 

154.  Constitution  of  Carbohydrates. — Some  reference  has  already  been 
made  to  the  glucoses  in  the  chapter  on  organic  compounds.  It  is  there 
shown  that  closely  allied  to  the  aldehydes  is  a family  of  compounds  known 
as  aldoses.  Of  these,  the  formula  of  hexose,  one  form  of  which  is  glucose, 
has  been  given  and  explained.  In  both  aldehydes  and  aldoses,  there  occurs 
the  carbonyl  (CO)  group  in  which  the  oxygen  is  directly  united  to  the  carbon 
by  its  two  links  or  bonds.  It  will  be  noticed  that  this  group  is  attached  to 
the  free  end  of  the  open  chain  of  carbon  atoms.  Glucose  has  been  regarded 
as  an  aldehyde  of  mannitol,  and  may  be  formed  by  processes  of  moderate 
oxidation  from  that  alcohol  : — 


CHoHO 

CHHO 

CHHO 

CHHO 

CHHO 


or  C«H8(HO)o  + 0 


ICHsHO 

Mannitol.  Oxgyen. 


(CH2HO 

CHHO 

CHHO 

CHHO 

CHHO 

'COH 


or  CfiHiaOe  + H.O. 


Glucose. 


Water. 


Conversely  upon  reduction,  glucose  takes  up  two  atoms  of  hydrogen  and  is 
converted  into  mannitol.  The  formula  given  shows  the  composition  and 
relationship  of  glucose,  which  name  is  now  more  specifically  applied  to  dex- 
trose. Lsevulose,  called  also  fructose,  has  the  same  simplest  formula  as 
dextrpse,  CeHisOg,  and  like  it  contains  the  radical  carbonyl.  There  is, 
liowever,  this  difference,  the  carbonyl  is  attached  not  to  one  of  the  free 
atoms  of  the  carbon  chain,  but  to  the  last  but  one,  thus  showing  lsevulose 
to  be  a ketose  and  closely  allied  to  butyl-methyl  ketone. 

The  sucroses  may  be  regarded  as  bodies  formed  by  the  union  of  two 
molecules  of  the  glucose  type,  with  the  elimination  of  a molecule  of  water. 


THE  CARBOHYDRATES. 


75 


a reaction,  however,  whicli  does  not  occur  anything  like  so  readily  as  the 
decomposition  of  a sucrose  into  its  component  molecules  of  glucose.  Thus 
under  the  influence  of  weak  acids  cane  sugar  splits  up  into  glucose  and 
fructose  : — 

CioH220ii+H20=CH2HO-(CHHO)4COH+CH2HO.(CHHO)3-COCH2HO. 

Cane  sugar.  Glucose,  Dextrose.  Fructose,  Lsevulose. 

The  structural  composition  of  cane  sugar  is  not  indicated  in  the  above 
ecpiation,  but  the  formulae  of  the  resultant  products  show  them  to  be  re- 
spectively an  aldose  and  a ketose.  Owing  to  their  composition,  the  sucroses 
are  regarded  as  di-hexoses. 

The  amyloses  are  much  more  complex  bodies  than  are  the  preceding 
groups.  They  depart  still  further  from  the  simplest  hexose  type,  inasmuch 
as  another  molecule  of  water  has  been  eliminated.  This  is  clearly  shown 
in  the  following  specially  written  formulae  : — 

Ci2H240i2*  O12H22O11.  C42H20O10. 

[Two  Molecules  of  Glucose.  One  Molecule  of  Sucrose.  Two  “ Units  ” of  Amylose. 

The  molecules  of  the  amyloses  are  high  multiples  of  the  unit  group, 
C0H10O5.  From  their  complexity  they  are  termed  poly-hexoses. 

Brown  and  Morris  in  1888  and  1889  contributed  to  the  Chemical  Society's 
Journal  important  papers  on  the  Molecular  Weights  of  the  Carbohydrates. 
Their  researches  were  based  on  RaoulCs  investigations  on  the  lowering  of 
the  freezing  point  of  a solvent  by  the  solution  in  it  of  any  substance.  (Thus, 
salt  water  freezes  at  a lower  temperature  than  pure  water.)  Raoult  found 
that  equivalent  molecular  proportions  of  different  compounds  cause  under 
the  same  conditions  a similar  depression  of  the  freezing  point  of  the  solvent. 
This  offers  a valuable  means  of  determining  molecular  ’weight,  as,  knowing 
that  of  one  body  dissolved,  that  of  others  may  be  determined.  Brown  and 
]\Iorris  applied  this  method  to  the  investigation  of  the  carbohydrates.' 


Molecular  Constitution  of  Carbohydrates. 


Substance. 


Formula  of  Molecule. 


Dextrose 
Cane  Sugar  . . 

Cane  Sugar,  same  solution  after  inversion"^' 
Maltose 

Lactose,  Milk  Sugar 
Arabinose  . . 

Raffinose 

Mannite  or  Mannitol 
Galactose  f . . 

Maltodextrin 
Amylodextrin 

Lowest  or  Stable  DextrinJ 
Soluble  Starch 


C6H42O6 

C12H22O11 

CcHipOe 

C42H22O11 

Ci2H2204i 

C5H10O5 

C18H32O16.  5H2O 

C«Hs(HO)b 

C6H4206 

C12H220H  I 
(Ci2H2o04o)2  j 
C12H22O11 

(Ci2H2oOio)6 
2OC12H20O10 
5(Ci2H2oOio)20 


Molecular 

Weight. 


180 

342 

180 

342 

342 

150 

594 

182 

180 

990 

2,286 

6,480 

32,400 


* Cane  Sugar  after  inversion  is  split  up  into  dextrose  and  laivulose,  and  dextrose 
having  a molecular  weight  of  180,  so  must  lsevulose,  and  be  represented  by  the  formula 
CfiHioOfi.  t Galactose  is  the  “ dextrose  ” of  lactose. 

t The  molecular  weight,  not  only  of  the  lowest  or  stable  dextrin,  is  represented 
by  the  formula  (C12H20  O|o)2c»  but  so  also  are  those  of  the  so-called  higher  dextrins, 
of  which  Brown  and  Morris  examined  a series.  They  find  that  “ the  numbers  obtained 
with  dextrins  occupying  very  different  positions  in  the  series  are  strikingly  identical.” 


76 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  above  table  contains  the  results  of  their  determinations,  which 
molecular  weights,  with  the  exception  of  that  of  starch,  were  obtained  by 
direct  estimations.  In  this  latter  case  the  direct  method  was  inapplicable, 
and,  accordingly,  recourse  was  had  to  an  indirect  method,  based  on  the 
generally  accepted  hypothesis  that  the  starch  molecule  must  be  at  least 
five  times  the  size  of  the  dextrin  molecule  produced  under  certain  conditions. 
Mannitol,  having  such  an  intimate  relationship  in  constitution  to  the  carbo- 
hydrates, is  also  included  in  the  table. 

It  will  be  seen  that,  commencing  with  those  most  simple  in  constitution, 
the  glucoses  come  first,  and  the  amyloses  last  in  order.  In  nature  also  no 
doubt  the  simpler  bodies  are  first  produced,  and  from  these  those  which 
are  more  complex.  In  flour  as  a product  of  the  finished  and  ripened  grain, 
by  far  the  greater  part  of  the  carbohydrates  present  is  in  the  form  of  starch, 
and  the  chemistry  of  these  bodies,  in  so  far  as  bread-making  is  concerned, 
deals  with  the  degradation  or  breaking  down  of  the  starch  molecule  into 
simpler  substances,  rather  than  with  its  building  up.  For  this  reason  it 
will  be  preferable  to  begin  our  study  of  the  carbohydrates  with  the  amyloses, 
and  then  proceed  to  the  other  members  of  the  family. 

Cellulose,  TiCeHioOs. 

156.  Occurrence  and  Physical  Properties. — ^This  body,  of  which  there 
are  numerous  physical  modifications,  constitutes  the  framework  or  skeleton 
of  vegetable  organisms,  in  which  it  acts  as  a sort  of  connective  tissue,  bind 
ing  and  holding  together  the  various  parts  and  organs  of  plants.  Woody 
fibre  consists  largely  of  cellulose  and  one  or  two  closely  allied  substances, 
among  which  is  lignin,  a harder  and  more  resistant  body  than  cellulose,  but 
of  somewhat  similar  composition. 

The  pith  of  certain  plants  is  nearly  pure  cellulose.  Manufactured 
vegetable  fabrics,  as  cotton  and  linen  goods,  and  likewise  unsized  paper,  are 
also  cellulose  in  an  almost  pure  form.  Chemically  pure  Swedish  filters  con- 
sist of  cellulose  with  only  the  most  minute  traces  of  other  bodies.  The 
horny  part  of  certain  seeds,  such  as  “ vegetable  ivory,'’  consist  of  a form  of 
cellulose,  which  is  of  interest  as  being  a “ reserve  ” store  of  nutriment,  as 
starch  is  in  wheat  and  other  seeds. 

Pure  cellulose  is  white,  translucent,  of  specific  gravity  of  about  1*5,  and 
is  insoluble  in  water,  alcohol,  ether,  and  both  fixed  and  volatile  oils.  An 
ammoniacal  solution  of  copper  hydroxide  dissolves  cellulose  completely  ; 
this  reagent  may  be  prepared  by  precipitating  copper  hydroxide  from  the 
sulphate,  by  sodium  hydroxide,  and  then  dissolving  the  thoroughly  washed 
precipitate  in  strong  ammonia.  This  solution  dissolves  cotton  wool,  or 
thin  filtering  paper,  forming  a sirupy  solution  ; on  the  addition  of  slight 
excess  of  hydrochloric  acid,  the  cellulose  is  precipitated  in  flaky  masses  ; 
these,  on  being  washed  and  dried,  produce  a brittle  horny  mass.  This  re- 
precipitated cellulose  is  not  coloured  blue  by  iodine,  and  still  presents  the 
same  chemical  properties  as  ordinary  cellulose. 

156.  Behaviour  with  Chemical  Reagents. — Cellulose,  on  being  boiled 
with  water  under  pressure,  is  converted  into  a body  bearing  some  resemblance 
to  dissolved  starch,  inasmuch  as  it  is  coloured  blue ‘by  iodine.  The  same 
effect  is  produced  more  rapidly  by  treatment  with  acids.  Boiling  with 
dilute  sulphuric  or  nitric  acid,  or  strong  hydrochloric  acid,  breaks  up  cellu- 
lose into  a flocculent  mass,  but  without  any  change  in  composition.  Treat- 
ment with  stronger  nitric  acid  changes  cellulose  into  nitro-substitution  pro- 
ducts called  gun  cottons  or  pyroxylin  ; while  that  acid,  in  a yet  more  con- 
centrated form,  oxidises  cellulose  to  oxalic  acid.  By  the  action  of  strong 
sulphuric  acid,  cellulose  is  converted  into  a form  of  sugar  known  as  cello- 


THE  CARBOHYDRATES. 


77 


biose,  C12H22O11.  Concentrated  solutions  of  potash  or  soda  also  dissolve 
cellulose,  with  the  formation  apparently  of  the  same  compound.  Sulphuric 
acid,  diluted  with  about  half  or  quarter  its  bulk  of  water,  has  a most  remark- 
able action  on  unsized  paper.  The  paper  on  being  dipped  in  the  acid  for  a 
few  seconds,  and  then  washed  with  weak  ammonia,  is  found  to  be  changed 
into  a tough  parchment-like  material,  which  may  be  used  for  many  of  the 
purposes  to  which  animal  parchment  is  applied.  This  body  is  familiar  to 
confectioners,  as  being  sold  under  the  name  of  parchment  paper  for  tying 
down  pots  containing  jam  and  other  substances.  Filter  papers,  on  being 
momentarily  immersed  in  nitric  acid  of  density  1 *42,  are  remarkably  tough- 
ened, the  product  being  still  pervious  to  liquids  and  therefore  suitable  for 
filtering  purposes.  Such  papers  are  recommended  for  filtering  bodies  that 
have  to  be  removed  from  the  paper  while  wet,  and  are  now  sold  commercially 
for  that  purpose. 

157.  Existence  in  Wheat. — ^There  are  three  forms  of  cellulose  present 
in  wheat,  of  which  the  following  is  a brief  description  ; — 

1.  The  lignified  or  woody  cellulose  of  the  bran,  which  is  entirely  removed 
in  the  process  of  making  white  flour.  In  whole-meal,  which  contains  the 
bran,  the  lignified  cellulose  undergoes  no  change  in  the  operations  of  bread- 
making, nor  afterwards  during  the  processes  of  human  digestion. 

2.  The  parenchymatous  cellulose,  which  forms  the  cell-walls  of  the 
endosperm.  This  disappears  during  germination  of  the  grain,  and  is  far 
more  easily  dissolved  by  all  reagents  than  is  lignin  or  woody  cellulose. 

3.  So-called  starch  cellulose  constitutes  the  envelopes  or  cellulose- 
skeleton  of  the  starch  cells.  It  is  this  form  which  is  most  readily  converted 
into  the  starch-like  body,  giving  a blue  colouration  with  iodine. 


158.  Composition. — ^The  formula,  CeHioOs,  is  the  simplest  that  can  be 
derived  from  the  percentage  composition  of  cellulose,  but  there  is  little 
doubt  that  the  molecule  really  consists  of  a number  of  groups  of  CeHioOs 
united  together,  and  is  at  least  as  complex  as  that  of  starch. 


Starch  ^ 

v 


(Ci2H2oOio)20 
(Ci2H2oOio)20 
(Ci2ll2oOio)20 
(Ci2H2oOio)20 
(C12H20O10)  20 


159.  Occurrence. — ^The  starchy  matters  of  wheat  are  of  vast  importance 
as  constituting  the  greatest  portion  of  the  whole  seed.  Starch  is  not  only 
found  in  wheat,  but  also  in  other  seeds  ; and  in  fact  in  most  vegetable 
substances  used  as  food.  From  whatever  source  obtained,  starch  has  the 
same  chemical  composition,  but  varies  somewhat  in  physical  character. 


160.  Physical  Character. — Starch,  when  pure,  is  a glistening,  white, 
inodorous  granular  powder.  If  a pinch  be  taken  and  squeezed  between 
t!ie  thumb  and  finger,  a peculiar  “ crunching  (crepitating)  sound  is  heard. 
Starch  has  a specific  gravity  of  from  1*55  to  1*60.  Starch  is  extremely 
hygroscopic,  absorbing  moisture  with  avidity  ; in  the  form  in  which  it  is 
usually  sold  it  contains  about  18  per  cent,  of  water.  Wheat  starch  after 
drying  in  a vacuum  still  retains  about  11  per  cent,  of  water.  Heating  in  a 
current  of  dry  air  to  a temperature  of  110°  C.  renders  it  practically  anhydrous. 

161.  Microscopic  Appearance. — ^The  microscope  shows  starch  to  be 
composed  of  minute  grains,  each  having  a well  defined  strueture.  These 
grains  are  respectively  termed  starch  cells,  granules,  or  corpuscles.  Care- 
ful examination  reveals  that  each  cell  consists  of  an  outer  coating  or  pellicle 
formed  of  a very  delicate  type  of  cellulose,  to  which  the  name  “ starch 


78 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


Plate  I. 


IfheaJt/. 


JPcftccto. 


Microscopic  Sketches  of  Various  Starches. 

JUia^nificdL  a^outy  HJO  ciiajTvefX/'S.  £E.TulUr 


THE  CARBOHYDRATES. 


79 


cellulose  is  applied.  This  envelope  is  built  up  of  several  layers,  arranged 
concentrically  one  over  the  other,  and  contains  within  its  interior  a sub- 
stance which  may  be  called  starch  proper,  in  distinction  from  the  enclosing 
matter.  This  starch  proper  is  also  termed  “ starch  granulose  or  “ amy- 
lose.""  On  careful  examination  these  separate  coats  appear  as  a series  of 
more  or  less  concentric  rings,  having  for  a nucleus  a dark  spot  or  cross, 
termed  the  “ hilum."'  The  actual  size  and  shape  of  starch  cells  vary  with 
the  source  from  which  the  starch  is  derived  ; thus  the  grains  of  starch  from 
potatoes  are  comparatively  large,  while  those  of  rice  are  extremely  minute. 
When  examined  by  polarised  light  certain  starches  exhibit  characteristic 
appearances — these  are  referred  to  in  detail  in  the  table  following.  A 
description  of  the  phenomena  of  polarisation  is  given  in  Chapter  IV.  It  is 
possible  in  many  instances  to  determine  the  origin  of  a sample  of  starch  by 
its  microscopic  characteristics  ; it  follows  that  impurities  may  similarly  be 
detected  ; also,  as  all  vegetable  adulterants  of  flour  contain  starch,  admix- 
ture of  other  grains,  as  maize,  rice,  etc.,  is  in  this  manner  revealed. 

In  Plate  I is  given  the  appearance  of  the  more  important  starches  as 
seen  under  the  microscope. 

Microscopic  Characters  of  Various  Starches. 

162.  Wheat. — ^Wheat  starch  is  extremely  variable  in  size,  the  diameter 
of  the  corpuscles  being  from  0*0022  to  0*052  m.m.  (0*00009  to  0*0029  inch). 
Many  observers  point  out  that  medium  sized  granules  are  comparatively 
absent.  The  grains  are  circular,  or  nearly  so,  being  at  times  somewhat 
flattened.  The  concentric  rings  are  only  seen  with  difflculty  ; the  hilum  is 
not  so  visible  as  in  certain  other  starches.  Polarised  light  shows  a faint 
cross.  In  old  samples  of  wheat  or  flour  the  granules  show  cracks  and 
fissures  : this  applies  more  or  less  to  all  starches. 

163.  Barley. — Granules  more  uniform  in  size  than  those  of  wheat,  also 
somewhat  smaller  ;]  average  diameter  0*0185  m.m.  (0*00073  inch)  ; a few 
exceptionally  large  granules  may  be  found  measuring  as  much  as  0*07  m.m. 
Shape,  slightly  angular  circles.  Concentric  rings  and  hilum  either  invisible 
or  only  seen  with  difficulty. 

164.  Rye. — ^Diameter  of  granules  from  0*0022  to  0*0375  m.m.  (0*00009 
to  0*00148  inch).  Taking  a whole  field,  the  average  size  of  granules  is 
usually  somewhat  higher  than  those  of  wheat.  Shape,  granules  are  almost 
perfectly  round,  here  and  there  show  cracks.  Concentric  rings  and  hilum 
only  seen  with  difficulty. 

165.  Oats. — ^Diameter  of  granules,  0*0044  to  0*03  m.m.  (0*00017  to 
0*00118  inch).  Granules  are  angular  in  outline,  varying  from  three  to  six- 
sided. 

166.  Maize. — ^Diameter  of  granules,  average  size,  0*0188  m.m.  (0*00074 
inch).  Shape,  from  round  to  polyhedral,  mostly  elongated  hexagons,  with 
angles  more  or  less  rounded.  Concentric  rings  scarcely  visible,  hilum  star- 
shaped. 

167.  Rice. — ^Diameter  of  granules  from  0*0050  to  0*0076  m.m.  (0*0002  to 
0*0003  inch).  Granules  are  polygonal  in  shape,  mostly  either  five  or  six- 
sided,  but  occasionally  three-sided.  Are  usually  seen  in  clusters  of  several 
joined  together.  A very  high  magnifying  power  shows  a starred  hilum. 

168.  Potatoes. — ^Diameter  of  granules  from  0*06  to  0*10  m.m.  (0*0024  to 
0*0039  inch).  The  granules  vary  greatly  in  shape  and  size  ; the  smaller 
ones  are  frequently  circular  ; the  larger  grains  are  mussel  or  oyster  shaped. 


80 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  hilum  is  annular,  and  the  concentric  rings  incomplete,  but,  especially 
in  the  larger  granules,  clear  and  distinct.  The  rings  are  distributed  round 
the  hilum  in  very  much  the  same  way  as  the  markings  show  on  the  outside 
of  a mussel  shell.  With  polarised  light  a very  distinct  dark  cross  is  seen,, 
the  centre  of  which  passes  through  the  hilum. 

169.  Canna  Arrowroot,  or  Tous  les  mois. — ^Diameter  of  granules  varies 
from  0-0469  to  0*132  m.m.  (0-0018  to  0*0052  inch).  The  shapes  differ  con- 
siderably, from  round  to  more  or  less  elongated  ovals.  The  hilum  is  eccen- 
tric ; the  rings  are  incomplete,  extremely  fine,  narrow  and  regular.  Under 
polarised  light  a more  distinct  cross  is  seen  than  with  the  potatoes. 

170.  Preparation  and  Manufacture  of  Starch. — ^For  experimental  pur- 
poses, starch  can  readily  be  obtained  from  wheaten  flour  by  first  preparing 
a small  quantity  of  dough  ; this  is  then  vTapped  up  in  a piece  of  fine  muslin, 
or  bolting  silk,  and  kneaded  between  the  fingers  in  a basin  of  water.  The 
milky  fluid  thus  produced  deposits  a white  layer  of  starch  on  the  bottom  of 
the  vessel,  which  may  be  carefully  air-dried.  The  starch  of  barley  and  the 
other  cereals  may  be  obtained  in  a sufficiently  pure  form  for  microscopic 
study  in  the  same  manner.  Potatoes  require  to  be  first  scraped,  or  rubbed 
through  a grater,  into  a pulp  ; this  pulp  must  then  be  enclosed  in  the  muslin 
and  the  starch  washed  out. 

On  the  manufacturing  scale,  starch  is  obtained  from  wheat  and  other- 
grains  by  first  coarsely  grinding  and  then  moistening  the  meal  with  water. 
This  is  allowed  to  stand,  and  after  three  or  four  days  fermentation  sets  in, 
more  water  is  then  added,  and  the  putrefactive  fermentation  allowed  to- 
proceed  for  some  three  or  four  weeks.  By  the  end  of  this  time  the  gluten 
and  other  nitrogenous  matters  are  dissolved.  They  are  then  readily  sepa- 
rated from  the  starch  by  washing,  after  which  the  starch  is  dried.  Starch 
is  now  largely  manufactured  from  rice  by  a process  in  which  the  grain  is  sub- 
jected to  the  action  of  very  dilute  caustic  soda,  containing  about  0*3  per 
cent,  of  the  alkali  ; this  reagent  dissolves  the  nitrogenous  bodies  and  leaves- 
the  starch  unaltered.  The  so-called  “ corn  flour  ” is  the  starch  of  maize 
prepared  after  the  same  fashion.  Potato  starch  is  obtained  by  first  rasping 
tlie  Avashed  potatoes  into  a pulp  by  machinery  ; the  pulp  is  next  washed  in 
a sieve,  the  starch  is  carried  through  by  the  Avater,  and  after  being  allowed 
to  subside  is  dried  on  a tile  floor  at  a gentle  heat. 

171.  Gelatinisation  of  Starch. — Starch  is  insoluble  in  cold  Avater,  and 
cannot  be  dissolved  by  any  knoA\m  liquid  AAnthout  change  ; this  folloAVS  from 
its  having  a definite  organic  structure  ; AAffien  this  is  destroyed,  as  must  of 
necessity  be  the  case  AA^henever  a solid  is  rendered  liquid,  it  cannot  by  any 
artificial  means  be  again  built  up  in  the  same  form. 

As  previously  stated,  the  starch  granules  consist  of  an  outer  envelope  of 
cellulose,  enclosing  AAffiat  is  termed  “ amylose,”  or  starch  proper.  This 
latter  body  is  soluble,  and  although  pure  starch  in  the  granular  form  yields 
no  soluble  substance  to  Avater,  yet  if  the  cellulose  envelopes  be  ruptured  by 
mechanical  means,  it  is  then  found  that  on  treatment  AAotli  Avater  at  ordinary 
temperatures  a soluble  extract  is  obtained.  When,  hoAvever,  starch  is  sub- 
jected to  the  action  of  boiling  AA'ater  a marked  change  ensues  : under  the 
influence  of  heat  the  little  particles  in  the  interior,  by  SAvelling,  burst  the 
containing  envelope,  and  dissolving  in  the  water  form  a thick  and  viscous 
liquid,  A\4iich  on  cooling,  if  sufficiently  concentrated,  solidifies  into  a gelatin- 
ous mass.  This  solution  of  starch  is  someAAffiat  cloudy,  owing  to  the  undis- 
solved particles  of  starch  cellulose  remaining  in  suspension.  These  may  be,, 
in  great  part,  removed  by  filtration. 

This  bursting  of  the  starch  granules  is  frequently  spoken  of  as  the  “ gela- 


THE  CARBOHYDRATES. 


81 


tinisation  of  starch,  and  the  resulting  substance  as  “ starch-paste.'’  The 
temperature  at  which  this  change  occurs  varies  with  the  nature  and  origin 
of  the  starcli. 

The  following  table  gives  particulars  as  to  the  gelatinising  temperatures 
of  starch  from  different  sources.  The  figures  to  the  left  are  those  of  Lipp- 
man,  while  to  the  right  are  given  the  results  of  a series  of  later  determinations 
made  by  Lintner,  and  published  in  1889.  It  may  be  taken  that  Lintner's 
temperatures  are  for  complete  gelatinisation. 


Temperature  of  Gelatinisation  of  Starch. 


Granules 

Gelatinisation. 

Complete 

Gelatinisation, 

Source  of  Starch. 

Swollen. 

Commenced. 

Completed. 

Lintner. 

°C. 

°F. 

°C. 

1 

°F. 

1 =C. 

°F. 

°C. 

°F. 

Barley  . . 

.37-5 

99-5 

57-2 

135 

62-2 

144 

80 

176 

Maize  . . 

50-0 

122-0 

55-0 

131 

62-2 

144 

75 

167 

%e 

45-0 

113-0 

50-0 

122 

55-0 

131 

80 

176 

Potato  . . 

46-1 

115-0 

58-3 

137 

62-2 

144 

65 

149 

Rice 

53-8 

129-0 

58-3 

137 

62-2 

144 

80 

176 

Wheat  . . 

50-0 

122-0 

65-0 

149 

67-2 

153 

80 

176 

Green  Milt 

— 

— 

— 

— 

— 

— 

85 

185 

Kilned  Milt  . . 

— 

— 

— 

— 

— 

— 

80 

176 

Oats 

— 

1 — 

— 

— 

1 i 

85 

185 

These  temperatures  of  gelatinisation  assume  that  the  walls  of  the  starch- 
containing  cells  have  been  broken  down,  and  that  excess  of  water  is  present  ; 
otherwise  the  temperature  of  gelatinisation  is  considerably  higher  : thus, 
in  stiff  biscuit  doughs,  and  even  in  bread,  much  of  the  starch  remains  un- 
gelatinised even  after  being  baked. 

There  is  doubt  as  to  whether  or  not  gelatinised  starch  is  in  a state  of  true 
solution.  When  filtered,  the  clear  filtrate  gives  a blue  colouration  with 
iodine  (a  characteristic  reaction  of  starch),  but  on  dialysis  through  an  ani- 
mal or  vegetable  membrane,  or  even  filtration  through  porous  earthenware, 
the  starch  is  removed.  This  has  led  to  the  view  that  the  starch  in  starch 
paste  is  simply  in  a state  of  extremely  fine  division,  but  more  probably  the 
state  is  one  of  true  solution,  and  the  removal  by  filtration  is  due  to  the 
highly  colloid  nature  of  starch. 

172.  Soluble  Starch. — On  treating  starch  with  dilute  acids  in  the  cold, 
the  starch  loses  its  power  of  gelatinisation,  and  becomes  what  is  known  as 
soluble  starch.”  In  this  form  no  change  of  appearance  is  observed  in  the 
granules,  but  the  starch  readily  dissolves  in  hot  water  to  a clear  limpid 
liquid.  Lintner  directs  soluble  starch  to  be  prepared  in  the  following  man- 
ner ; Pure  potato  starch  of  commerce  is  taken  and  mixed  with  a sufficient 
quantity  of  7*5  per  cent,  hydrochloric  acid  to  cover  it,  and  allowed  to  stand 
either  at  ordinary  temperatures  for  seven  days,  or  for  three  days  at  40°  C. 
By  that  time  the  starch  will  have  lost  the  power  of  gelatinisation,  and  is 
repeatedly  washed  with  cold  water  until  every  trace  of  acid  is  removed.  It 
is  then  air-dried,  and  is  readily  and  completely  soluble  in  hot  water  to  a 
bright  and  limpid  solution. 

Soluble  starch  is  probably  a polymeride  of  ordinary  starch,  and  when 
dissolved,  then  known  as  “ starch  solution,”  closely  resembles  “ starch- 
paste  ” in  its  chemical  behaviour. 

G 


82 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


173.  Action  of  Caustic  Alkalies  on  Starch. — ^Treatment  with  cold  dilute 
solutions  of  potash  or  soda  causes  starch  granules  to  swell  enormouslj^  ; 
the  volume  of  starch  grains  may  thus  be  made  to  increase  125-fold.  This 
reaction  also  serves  for  the  differentiation  of  the  various  starches.  H. 
Symons  recommends  the  use  of  soda  solutions  of  different  strengths  : a 
small  quantity  of  the  starch  is  shaken  up  in  a test-tube  for  ten  minutes  with 
one  of  the  soda  solutions,  and  then  a drop  of  the  liquid  is  examined  under 
the  microscope.  The  following  is  a table  of  results  thus  obtained  : — - 


A few  Starch  granules 

The  greater  number 

All 

dissolved  in  a solution  of 

dissolved  in  a solution  of 

dissolved  in  a solution  of 

Potato 

0*6  per  cent. 

0*7  per  cent. 

0*8  per  cent. 

Oats 

. . 0*6 

0-8 

1-0 

Wheat 

..  0-7 

0-9 

DO 

Maize 

. . 0-8 

DO  „ 

M 

Rice 

..  DO  „ 

1*1 

1-3 

174.  Action  of  Zinc  Chloride. — ^Treatment  with  zinc  chloride  also  causes 
a remarkable  swelling  of  the  granules  of  starch  ; this  reaction,  when  viewed 
under  the  microscope,  serves  admirably  to  show  the  structure  of  the  cor- 
puscles. Some  concentrated  solution  of  zinc  chloride  is  tinged  with  a trace 
of  free  iodine.  A few  grains  of  the  starch  are  placed  on  a glass  slide,  to- 
gether with  a small  drop  of  this  solution.  No  change  is  observed  until  a 
little  water  is  also  added.  They  then  assume  a deep  blue  tint,  caused  by 
the  iodine,  as  explained  in  a subsequent  paragraph,  and  gradually  expand. 
A frill-like  margin  developes  round  the  granule,  the  foldings  of  this  frill 
open  out  in  their  turn,  until  the  granules  at  last  sw^ell  up  to  some  twenty  or 
thirty  times  the  original  volume,  and  then  appear  as  limp-looking  sacs. 
These  changes,  so  far  as  can  be  seen,  are  not  accompanied  by  any  expulsion 
of  the  inner  contents  of  the  cell. 

175.  Properties  of  Starch  in  Solution.— A solution  of  starch  is  colourless, 
odourless,  tasteless,  and  perfectly  neutral  to  litmus.  Starch  is  a highly 
colloid  body,  and  can  be  readily  separated  by  dialysis  from  crystalUne  sub- 
stances. On  evaporating  a solution  of  starch,  it  does  not  recover  its  original 
insolubility.  Starch  solution  causes  right-handed  rotation  of  polarised  hght. 
Starch  amylose  is  insoluble  in  alcohol,  and  may  be  entirely  precipitated 
from  its  aqueous  solution  by  the  addition  of  alcohol  in  sufficient  quantity. 
Tannin  precipitates  both  starch-paste  and  soluble  starch,  the  precipitate 
being  re-dissolved  on  heating.  Barium  hydroxide  gives  an  insoluble  com- 
pound with  solution  of  starch,  and  is  used  in  this  way  in  some  processes  of 
starch  estimation. 

Soluble  starch,  owing  to  the  formation  of  a hydriodide  of  starch 
(C24H4o02oI)4HI,  is  coloured  an  intense  blue  by  the  addition  of  iodine  in 
extremely  small  quantities.  This  blue  colouration  disappears  on  heating  the 
solution,  but  reappears  on  its  being  cooled.  This  reaction  is  exceedingly  deli- 
cate, and  is  practically  characteristic  of  starch.  For  the  purpose  of  this  test,  the 
iodine  may  be  dissolved  in  either  alcohol  or  an  aqueous  solution  of  potassium 
iodide  ; for  most  purposes  preferably  the  latter.  For  the  occurrence  of 
tliis  reaction,  the  presence  of  water  is  apparently  essential  ; for  if  wh eaten 
flour  be  moistened  with  an  alcoholic  solution  of  iodine  no  colouration  is 
produced  other  than  tlie  natural  brownish  yellow  tint  of  tincture  of  iodine. 
But  with  a potassium  iodide  solution  the  flour  assumes  a blue  colour  so 
intense  as  to  be  almost  black.  The  iodine  colouration  of  starch  is  only 
caused  by  free  iodine,  not  by  iodine  compounds  ; and  is  not  produced  except 
in  the  presence  of  hydriodic  acid  or  an  iodide.  Potash  or  soda  in  solution, 
when  added  to  dissolved  iodine,  immediately  combine  therewith  to  form 


THE  CARBOHYDRATES. 


8.3 


iodides  and  iodates  ; consequently,  the  iodine  test  for  starch  is  inapplicable 
in  an  alkaline  medium.  In  case  a solution  to  be  tested  for  starch  is  alkaline 
to  litmus,  cautiously  add  dilute  sulphuric  acid,  until  neutral  or  very  slightly 
acid  ; the  test  for  starch  may  then  be  made.  The  only  compounds  usually 
likely  to  interfere  with  the  iodine  reaction  for  starch  are  some  of  the  dextrins  ; 
these  bodies  combine  with  iodine,  forming  either  colourless  or  brown  com- 
pounds ; but  unless  present  in  large  quantities  do  not  prevent  the  detection 
of  starcli.  Iodine  combines  with  starch  more  readily  than  with  dextrin, 
consequently  the  iodine  should  in  such  cases  be  added  in  very  small  quan- 
tities at  a time,  when  the  blue  colouration  due  to  the  starch  will  appear 
before  the  brown  tint  produced  by  dextrin.  In  testing  for  starch  the  addi- 
tion of  iodine  solution  should  be  continued  until  an  excess  of  iodine  is  present 
in  the  solution. 

In  bodies  such  as  starchless  biscuits,  of  which  washed  gluten  may  form 
a constituent,  it  is  sometimes  found,  on  dropping  a solution  of  iodine  on  the 
broken  surface  of  the  biscuit,  that  a blue  colouration  is  produced,  but  that 
prolonged  boiling  fails  to  yield  a solution  which  gives  an  iodine  colouration. 
The  probable  explanation  seems  to  be  that  under  the  influence  of  heat  traces 
of  starch  cellulose  in  the  biscuit  products  are  converted  into  the  soluble 
variety,  and  hence  give  a colouration  in  situ,  but  are  in  such  small  quantity 
and  so  firmly  imprisoned  within  the  cellulose  as  not  to  be  liberated  by  boil- 
ing. It  is  not  sufficient  in  making  starch  tests  on  solid  substances  to  trust 
to  adding  iodine  to  the  substance  itself  : the  substance  should  also  be  ex- 
tracted with  boiling  water,  and  the  test  made  on  the  filtered  solution. 

Starch  does  not  cause  a precipitate  with  Fehling's  solution,  that  is,  it 
does  not  reduce  an  alkaline  solution  of  copper  sulphate  in  potassium  sodium 
tartrate.  See  paragraph  182,  on  Reducing  Power. 

Starch  under  the  influence  of  heat,  and  readily  when  treated  with  certain 
other  bodies,  is  transformed  into  others  of  the  carbohydrates. 

Dextrin,  SOCi^H^oOio,  or  WCeHioOj  + H^O  = 

176.  Occurrence. — ^Dextrin  is  principally  known  as  a manufactured 
article,  but  also  occurs  in  small  quantities  as  a natural  constituent  of  wheat 
and  most  bodies  containing  starch. 

177.  Physical  Character. — ^In  appearance,  dextrin  is  a brittle  transparent 
solid,  very  much  resembling  the  natural  gums,  as  gum  arable.  It  is  colour- 
less, tasteless,  and  odourless.  Dextrin  is  a colloid  body,  and  is  very  soluble 
in  water,  and  it  is  also  soluble  in  dilute  alcohol ; but  it  is  insoluble  in  absolute 
or  even  concentrated  alcohol,  by  means  of  which  it  may  be  precipitated 
from  its  solutions.  Dextrin  is  also  insoluble  in  ether.  Surfaces  moistened 
with  a solution  of  dextrin,  and  then  allowed  to  dry  in  contact  with  each  other, 
adhere  firmly.  Commercial  dextrin  has  usually  a more  or  less  brown  tint 
from  the  presence  of  caramel  in  small  quantity. 

178.  Preparation. — Dextrin  is  usually  prepared  by  the  action  of  heat, 
with  or  without  certain  reagents,  on  starch.  The  starch  may  be  maintainecl 
at  a temperature  of  about  150°  C.  until  it  assumes  a brown  colour  : treat- 
ment with  water  then  dissolves  out  dextrin  in  an  impure  form.  If  the 
starch  be  first  moistened  with  water  containing  a minute  quantity  of  nitric 
acid,  the  change  proceeds  much  more  rapidly  ; the  starch  should  in  this 
case  be  heated  to  about  200°  C.  The  substance  thus  yielded  is  that  known 
as  British  gum,  and  is  largely  used  for  sizing  calicoes  and  other  purposes  in 
commerce.  If  starch  solution  be  boiled  with  dilute  sulphuric  acid  until  it 
no  longer  gives  a blue  colouration  with  iodine,  dextrin  will  be  found  in  the 
solution,  but  mixed  with  maltose.  Certain  nitrogenous  bodies  also  possess 
the  power  of  converting  starch  into  dextrin  and  maltose. 


84 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


179.  Chemical  Character. — ^Dextrin  was  formerly  supposed  to  consist 
of  a mixture  of  polymeric  bodies  of  closely  similar  chemical  character. 
These  several  dextrins  were  separated  into  two  groups  by  their  difference  in 
behaviour  when  treated  with  iodine  solution.  The  members  of  one  of  these 
groups,  known  as  “ erythro- dextrins,”  were  found  to  strike  a reddish-brown 
colouration  on  treatment  with  iodine  ; while  the  others,  which  were  classified 
as  “ achroo-dextrins,”  yielded  no  colouration  when  iodine  was  added.  It 
has  already  been  stated  that  Brown  and  Morris  in  1889  investigated  the 
molecular  weights  of  the  carbohydrates,  and  that  they  found  the  results 
given  by  the  various  dextrins  were  practically  identical.  The  formerly  held 
theory  assumed  that  the  erythro-dextrins  contained  in  the  molecule  8 and 
9 respectively  of  the  group  C12H20O10  ; while  the  molecular  formula  of  the 
achroo-dextrins  included  from  2 to  7 of  the  C12H20O10  group.  In  face  of 
Raoult’s  method,  giving  identical  molecular  weights  for  the  whole  of  the 
dextrins,  the  view  of  their  being  polymeric  bodies  is  no  longer  tenable.  The 
iodine  colouration,  produced  by  the  so-called  erythro-dextrins,  is  due  to  the 
presence  of  certain  other  bodies,  termed  “ amy loins,”  which  Avill  subse- 
quently be  described. 

Dextrin  has  a powerful  action  on  polarised  light,  twisting  the  ray  to  the 
right  : its  name  is  derived  from  this  property.  A solution  of  dextrin  in 
some  respects  resembles  one  of  starch  ; they  are,  however,  distinguished 
by  the  dextrin  giving  no  blue  colour  when  treated  with  iodine.  Dextrin 
was  formerly  supposed  to  exercise  no  reducing  action  on  Fehling’s  solution, 
and  that  in  that  respect  its  behaviour  was  similar  to  that  of  starch.  But 
more  recent  observers,  among  whom  are  Brown  and  Millar  {Journ.  Chem. 
Soc.,  1899),  point  out  that  dextrin  has  a reducing  power  of  about  R 5*8. 

The  Sugars — Maltose,  Cane  Sugar,  Milk  Sugar,  and  Glucose. 

180.  General  Properties. — ^As  already  explained,  the  sugars  are  a sub- 
division of  the  class  of  bodies  known  as  carbohydrates  ; they  are  character- 
ised by  having  a more  or  less  sweet  taste,  and  are  soluble  in  water.  Many 
are  natural  products  occurring  both  in  the  animal  and  vegetable  kingdom. 

181.  Maltose,  C,2H220ii. — This  body  occurs  in  company  with  dextrin 

in  starch  solutions  which  have  been  treated  with  dilute  sulphuric  acid  until 
the  solution  no  longer  yields  a blue  colouration  with  iodine.  It  forms  a 
most  important  constituent  of  malt  extract,  amounting  to  from  60  to  65 
2^er  cent,  of  the  total  solid  matter.  In  the  pure  state,  maltose  consists  of 
small  hard  crystalline  masses  or  minute  needles,  which  are  soluble  in  v^ater 
and  dilute  alcohol.  Maltose,  being  a crystalline  body,  may  be  separated 
from  dextrin  by  dialysis,  and  also  by  precipitating  the  dextrin  by  means  of 
strong  alcohol.  A solution  of  maltose  causes  a right-handed  rotation  of  a 
ray  of  polarised  light.  Maltose  gives  no  colouration  with  iodine,  but,  in 
common  with  certain  other  of  the  sugars,  exercises  a reducing  or  deoxidising 
action  on  some  metallic  salts.  1 

I: 

182.  Reducing  Power. — ^This  reducing  action  is  most  commonly  tested 
by  means  of  the  reagent  known  as  “ Fehling’s  solution,”  which  consists  of 
sulphate  of  coi)y)er,  tartrate  of  potassium  and  sodium,  and  sodium  hydroxide, 
dissolved  in  water.  If  sodium  hydroxide  be  added  to  a solution  of  copper  1 
sulphate,  a })recipitate  of  copper  oxide,  CuO,  combined  with  water,  is  thrown  1 
down  ; the  sodium  and  potassium  tartrate  redissolves  this  and  forms  a 
deep  blue  solution,  which  may  be  boiled  for  some  minutes  without  alteration.  || 
Now  certain  varieties  of  sugar  reduce  the  CuO  to  CU2O  ; that  is,  they  take  i 
away  oxygen,  the  change  being  represented  by  2CuO  = CU2O  + G.  The; 
oxygen  is  taken  by  the  sugar,  and  for  our  present  purpose  need  not  be  traced 


THE  CARBOHYDRATES. 


85 


further.  The  CU2O,  or  copper  sub-oxide,  thus  formed  is  insoluble  in  the 
Fehling's  solution,  and  hence  is  precipitated,  first  as  a yellow  and  then  as  a 
brick-red  powder.  The  cupric  oxide  reducing  power,  or,  more  shortly,  the 
cupric  reducing  power  of  a substance,  has  been  defined  by  O’Sullivan  as 
“ the  amount  of  cupric  oxide  calculated  as  dextrose,  which  100  parts  reduce  ” 
from  Eehhng’s  solution  under  usual  conditions  of  analysis.  By  careful 
experiment  is  has  been  found  that — 

100  grams  of  dextrose  reduce  220*5  grams  of  CuO. 

100  ,,  maltose  ,,  137*8  ,,  ,, 

If  in  the  case  of  maltose  the  reduced  CuO  be  assumed  to  be  caused  by  dex- 
trose, and  calculated  as  such,  then — 

22^  5^^^  ~ ~ cupric  reducing  power  of  maltose. 

Another  way  of  expressing  the  same  thing  is — The  cupric  oxide  reduced 
by  a given  weight  of  dextrose  being  100,  the  amount  reduced  by  the  same 
weight  of  any  other  body  is  taken  as  the  cupric  oxide  reducing  power  of 
that  body. 

For  cupric  reducing  power  the  symbol  K or  k is  employed,  that  is  to  say, 
the  amount  of  reducing  sugars  calculated  as  dextrose  from  the  CuO  or  CU2O 
precipitate  =K. 

In  the  case  of  sugars  resulting  from  changes  produced  in  starch,  the 
present  more  widely  adopted  rule  is  to  take  the  reducing  power  of  maltose 
as  100,  and  that  of  other  bodies  in  terms  of  that  of  maltose.  For  the  cupric 
reducing  power  thus  expressed,  the  symbol  R is  employed.  For  example, 
if  starch  is  converted  into  a mixture  of  bodies,  one-fifth  of  which  is  maltose, 
and  the  remainder  without  reducing  action,  then  the  cupric  reducing  power 
of  the  mixture  would  be  R 20. 

183.  Cane  Sugar,  C12H22O11. — Cane  sugar  is  widely  spread  in  nature  : 
it  is  found  in  certain  roots,  as  beet-root,  in  the  sap  of  trees,  as  the  maple, 
and  in  the  juice  of  the  sugar  cane.  These  natural  solutions  are  first  purified, 
and  then  the  sugar  obtained  by  crystallisation.  The  sugar  found  in  per- 
fectly sound  wheat  is  either  identical  with,  or  closely  allied  to,  cane  sugar. 
Pure  cane  sugar  is  colourless,  odourless,  and  soluble  in  water,  to  which  it 
imparts  a sweet  taste.  Boiling  water  dissolves  sugar  in  all  proportions, 
while  cold  water  dissolves  about  three  times  its  weight.  Sugar  is  insoluble 
in  ether,  chloroform,  and  petroleum  spirit  ; but  is  very  slightly  soluble  in 
absolute  alcohol,  and  sparingly  soluble  in  rectified  spirits  of  wine.  The 
purest  commercial  form  of  sugar  is  that  sold  by  the  grocers  as  “ coffee 
sugar,”  and  consists  of  well  defined  crystals  about  three-sixteenths  of  an 
inch  across.  This,  w^hen  dried  at  100°  C.  to  expel  any  water  that  may  be 
present,  is  sufficiently  pure  for  most  experimental  w'ork  with  sugar.  A 
solution  of  cane  sugar  exercises  a right-handed  rotation  on  a polarised  ray 
of  light.  Cane  sugar  produces  no  colouration  with  iodine,  neither  does  it 
cause  any  precipitate  in  Fehling’s  solution.  By  the  action  of  heat,  cane 
sugar  melts,  and  if  then  allowed  to  cool,  forms  the  solid  termed  “ barley- 
sugar  ” ; a prolongation  of  the  heat  results  in  giving  the  sugar  a deeper 
colour.  Many  sweetmeats  consist  of  sugar  thus  treated.  The  darkening 
in  colour  is  due  to  the  fact  that  at  moderately  high  temperatures  (210°  C. 
= 410°  F.)  sugar  begins  to  undergo  decomposition.  Watery  vapour  and 
traces  of  oily  matter  are  evolved,  leaving  behind  a substance  soluble  in 
w'ater,  to  which  it  imparts  a rich  brown  tint.  The  characteristic  sweet  taste 
of  sugar  has  then  disappeared,  and  the  liquid  is  no  longer  capable  of  fer- 
mentation by  yeast.  The  change  has  resulted  in  the  formation  of  a brown 
substance,  termed  caramel,  to  which  the  formula  Ci2Hi809  has  been  given. 


86 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Caramel  is,  however,  rather  a mixture  of  bodies  than  a definite  chemical 
compound.  The  browning  of  dextrin  and  starch  when  heated  is  also  due 
to  the  formation  of  caramel. 

184.  Milk  Sugar  or  Lactose,  Ci2H220ti. — ^This  sugar  is  principally  of 
interest  as  being  that  present  in  milk,  which  contains  quantities  of  it  varying 
from  4 to  5 per  cent. 

It  will  be  noticed  that  the  three  sugars — maltose,  cane  sugar,  and  milk 
sugar — have  all  the  same  formula. 

185.  The  Glucoses  or  Hexoses,  C6H12O6. — ^Several  modifications  of 
glucose  exist  ; or  these,  two  only  are  of  importance  in  connection  with 
the  present  subject,  viz.,  glucose,  otherwise  known  as  dextrose  or  dextro- 
glucose,  and  fructose,  called  also  laevulose  or  laevo-glucose. 

186.  Glucose  or  Dextrose. — ^This  form  of  sugar  exists  as  a natural  pro- 
duct in  the  juices  of  many  fruits,  notably  the  grape  and  sweet  cherry.  The 
former  yields  about  15  per  cent,  of  grape  sugar.  Glucose  also  occurs  in  the 
flowers  of  certain  plants,  and  is  derived  from  these  by  bees  in  the  shape  of 
honey,  of  which  the  glucoses  are  the  principal  constituents.  Glucose  is 
also  found  in  large  quantity  in  the  urine  of  diabetic  patients ; some  doubt 
exists  as  to  Avhether  this  sugar  is  absolutely  identical  with  the  glucose  of 
fruits.  Glucose,  when  pure,  occurs  in  crystalline  masses  : it  has  a sweet  taste  ; 
but,  weight  for  weight,  is  said  to  possess  much  less  sweetening  action  than 
does  cane  sugar.  (But  see  Chap.  XXXIII.)  A solution  of  glucose  exercises  a 
right-handed  rotation  on  a ray  of  polarised  light,  and  from  this  property 
has  received  the  name  of  dextrose.  Among  the  sugars,  glucose  is  specially 
noticeable  for  the  great  ease  with  which  it  undergoes  alcoholic  fermentation. 
Like  maltose,  glucose  exercises  a reducing  action  on  Fehling’s  solution, 
producing  a red  precipitate  of  cuprous  oxide. 

187.  Fructose  or  Laevulose. — This  sugar  occurs  in  company  with  glu- 
cose in  certain  fruits,  and  also  in  honey.  Fructose  crystallizes  from  an 
alcoholic  solution  in  long  crystals  ; it  possesses  greater  sweetening  power 
than  glucose,  and  offers  more  resistance  to  alcoholic  fermentation.  A 
solution  of  leevo-glucose  exercises  a left-handed  rotation  on  a ray  of  po- 
larised light,  thus  distinguishing  it  from  dextro-glucose  ; the  two  names  are 
})ased  on  the  respective  right-  and  left-handed  rotary  power  of  these  glucoses. 
Laevo-  and  dextro-glucose  both  reduce  Fehhng’s  solution,  but  the  reducing 
])ower  of  fructose  is  rather  the  less  of  the  two. 

188.  Commercial  Glucose. — Glucose,  in  a more  or  less  pure  form,  is 
largely  manufactured  for  commercial  purposes.  Under  the  names  of  “ sac- 
charum,'’  “ invert  sugar,’'  etc.,  it  is  used  as  a substitute  for  malt  by  brewers 
and  distillers.  Various  forms  of  confectionery  and  fruit  jams  contain  glu- 
cose as  an  important  constituent.  Glucose  occurs  in  two  forms  in  com- 
merce ; ' the  one  is  a thick  and  almost  colourless  syrup,  the  other  is  a hard 
crystalline  body,  varying  in  colour  from  almost  white  to  pale  brown.  Glu- 
cose is  usually  made  from  starch  by  the  action  of  heating  with,  dilute  sulphuric 
or  oxalic  acid.  For  the  purpose,  either  maize  or  rice  is  usually  selected. 
Invert  sugar  is  produced  from  cane  sugar  by  heating  with  dilute  acid.  The 
following  are  analyses  of  different  types  of  commercial  glucoses 

I.  Brewer’s  solid  starch  glucose  (Morris). 

II.  Confectioner’s  sirupy  glucose  (The  authors). 

III.  Brewer’s  invert  sugar  (Morris). 


THE  CARBOHYDRATES. 


87 


Glucose. . 

I. 

57*16 

II. 

..  7*50 

III. 

. . 66*92 

Maltose . . 

8*09 

..  60*92 

— 

Sucrose . . 

— 

— 

. . 0*80 

Dextrin . . 

16*63 

. . 16*20 

— 

Proteins 

0*97 

— 

. . 0*59 

Mineral  matter 

1*45 

..  0*18 

1*59 

AVater  . . 

15*70 

. . 15*20 

. . 22*21 

Unfermentable  matter,  etc... 

100  00 

100  CO 

. . 7*89 

100*00 

The  glucose  in  these  commercial  products  is  a mixture  of  dextrose  and 
laevmlose.  The  sirupy  glucoses  consist  principally  of  maltose  and  dextrin. 
” Invert  sugar ''  is  so  called  because  such  sugar  rotates  the  ray  of  polarised 
light  to  the  left  instead  of  to  the  right,  as  does  normal  cane  sugar. 

The  Amyloins — Amylo-dextrin,  M alto -dextrin. 

189.  Constitution. — ^The  term  “ amyloins  ” was  proposed  by  Armstrong 
as  a convenient  name  for  a group  of  bodies  which  are  compounds  of  varying 
2:)roportions  of  the  amylin  or  dextrin  group,  Ci2H2oOio,  with  the  amylon  or 
maltose  molecule,  C12H22O11.  That  these  bodies  are  compounds  and  not 
mixtures  is  proved  by  their  being  incapable  of  separation  by  the  action  of 
alcohol,  whereas  mixtures  of  dextrin  and  maltose  in  the  same  proportions 
are  readily  so  separated.  Further,  the  amyloins  are  unacted  on  by  ordinary 
yeast,  SaccTiaromyces  cerevisice,  while  the  maltose  of  a mixture  is  readily  so 
fermented.  They  are  completely  converted  by  diastase  into  maltose. 

(C  H O 

— ^This  body  is  produced  by  the  action 

Ui2Xl2oUioj6 

of  dilute  acids  on  starch  granules  in  the  cold.  After  some  weeks’  treatment 
the  corpuscles  become  completely  disintegrated,  and  then  consist  largely  of 
amylo-dextrin  ; this  is  dissolved  in  hot  water  and  purified  by  precipitation 
with  alcohol.  This  substance  is  a definite  chemical  compound,  having  the 
formula  above  assigned  to  it  as  the  result  of  a determination  by  Raoult’s. 
method  ; and  is  produced  by  the  hydrolysis  of  starch.  Amylo-dextrin 
gives  an  intense  reddish-brown  colouration  with  iodine,  and  its  presence  is 
the  cause  of  the  chemical  properties  hitherto  ascribed  to  erythro- dextrin. 

191.  Malto-dextrin,  x — When  starch  is  converted  by 

U'-'i  2*120^10)  2 

diastase,  malto-dextrin  is  found  to  a greater  or  lesser  extent  in  the  pro- 
ducts, especially  when  the  converting  action  is  not  very  prolonged.  Malto- 
dextrin  is  unfermentable  by  ordinary  yeast,  Saccharomyces  cerevisice,  by 
the  action  of  which  it  may  be  distinguished,  and  separated,  from  maltose. 
Malto-dextrin  is,  however,  slowly  fermented  by  certain  secondary  yeasts. 
Malto-dextrin  cannot  be  separated  into  its  constituents  by  the  action  of 
alcohol,  but  diastase  completely  and  readily  converts  it  into  maltose. 

192.  Other  Carbohydrates  of  Cereals. — ^There  are  certain  other  carbo- 
hydrate bodies,  of  which  small  quantities  are  found  in  wheat  and  other 
grains  ; among  these  are  : — 

Eaffinose,  Ci8H320i8,5H20,  is  a sugar  somewhat  resembling  cane  sugar 
in  character,  but  less  easily  inverted.  Found  by  O’Sullivan  in  barley, 
a and  /?  Amylan,  TiCeHioOs,  are  two  bodies  having  the  same  empiric 


88 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


formula,  which  are  found  in  the  mucilaginous  portions  of  grains.  They 
are  almost  insoluble  in  cold  water,  dissolve  in  hot  water,  and  gelatinise  on 
cooling.  These  substances,  when  treated  with  dilute  acids,  are  converted 
into  glucose  without  the  production  of  intermediate  bodies.  Wheat  con- 
tains from  0*1  to  0-05  per  cent,  of  a amylan,  and  from  2*0  to  2*5  per  cent, 
of  ft  amylan. 

Extractive  Matters. — Under  this  heading  are  included  certain  substances 
which  cannot  be  readily  identified  in  the  same  manner  as  starch,  maltose, 
and  other  bodies.  This  is  in  consequence  of  their  possessing  no  very  definite 
chemical  reactions.  Lintner  has  obtained  from  barley  a white  amorphous 
substance  of  a gummy  nature,  to  which  the  name  xylan  has  been  given, 
and  which  in  composition  is  represented  by  the  formula,  CuH2oOio. 

Experimental  Work. 

193.  Cellulose. — ^Mix  in  a moderate  sized  beaker  about  5 grams  of  wheat 
meal,  with  150  c.c.  of  water,  and  50  c.c.  of  a 5 per  cent,  solution  of  sulphuric 
acid  ; and  set  the  beaker  in  a hot  water  bath  for  half  an  hour,  giving  its 
contents  an  occasional  stir.  At  the  end  of  that  time  add  50  c.c.  of  a 12  per 
cent,  potash  solution,  and  set  the  beaker  in  the  bath  for  another  half-hour. 
Observe  that  a residue  remains  ; allow  this  to  subside,  and  wash  it  by  de- 
cantation. Finally,  transfer  it  to  a filter,  and  let  it  drain.  The  substance 
thus  obtained  consists  of  the  cellulose  or  woody  fibre  of  the  wheat.  Add 
iodine  solution  to  a portion,  and  notice  that  it  produces  no  blue  colouration. 

It  is  assumed  that  most  of  the  students  who  go  systematically  through 
this  course  of  experimental  work  will  do  so  in  a regularly  appointed  labora- 
tory ; they  will  there  find  the  solutions  of  sulphuric  acid  and  potash  above 
referred  to  ready  made  up  for  use.  Full  directions  for  their  preparation, 
and  also  of  other  special  reagents  required,  are  given  in  the  chapters  on 
analytic  work  toward  the  end  of  the  book.  Unless  he  has  not  access  to  such 
solutions,  the  student  need  not  at  this  stage  of  his  work  trouble  to  specially 
prepare  them. 

194.  Microscopic  Examination  of  Starches. — Take  a small  quantity  of 
either  wheat  meal  or  fiour  and  make  it  into  a dough.  Tie  this  up  into  a 
piece  of  muslin  or  bolting  silk,  and  knead  in  a small  cup  or  glass  with  water  ; 
the  starch  escapes,  giving  the  water  a milky  appearance,  while  the  gluten 
and  bran  remain  behind  in  the  muslin.  Clean  an  ordinary  microscopic 
glass  slide  and  cover,  shake  the  starchy  water  and  place  a minute  drop  on 
the  slide,  lay  on  the  cover,  press  it  down  gently,  and  soak  up  any  moisture 
round  its  edge  with  a fragment  of  blotting  paper.  Place  the  slide  on  the 
microscopic  stage,  and  focus  the  instrument,  using  first  the  inch  and  then 
the  quarter  or  eighth  objective.  The  separate  starch  cells  are  then  plainly 
seen.  Trace  in  a few  of  the  cells  on  paper,  with  a camera  lucida,  and  sketch 
in  any  points  of  detail.  Measure  one  or  two  of  the  cells  with  the  eye-piece 
micrometer,  and  mark  their  dimensions  on  the  drawing. 

Take  a small  quantity  of  the  flours  respectively  of  barley,  rye,  rice,  and 
maize,  wash  out  the  starch  from  each,  and  examine  microscopicallyin  pre 
cisely  the  same  manner  as  with  the  wheat,  making  drawings  in  each  case. 
A little  corn  flour,  being  practically  pure  maize  starch,  may  be  used  instead 
of  maize  flour.  Cut  a potato  in  halves,  and  with  a sharp  knife  scrape  off  a 
little  pulpy  matter  from  the  cut  surface,  transfer  to  a slide,  and  examine 
with  the  microscope. 

Notice  in  each  case  the  relative  sizes  of  the  granules,  and  compare  their 
shapes.  Examine  for  the  hilum  and  also  observe  the  rings.  If  the  micro- 
scope be  fitted  with  polarising  apparatus,  study  the  various  starches  under 
polarised  light. 


THE  CARBOHYDRATES. 


89 


195.  Examination  of  Mixed  Starches. — With  separate  portions  of  wheat 
flour,  mix  respectively  small  quantities  of  rice  meal  and  corn  flour.  As 
before,  knead  the  starch  out  of  each,  and  examine  the  milky  fluid  for  the 
foreign  starches.  Notice  in  the  one  case  the  very  small  rice  starch  granules, 
and  in  the  other  the  somewhat  larger  maize  starch  granules  interspersed 
among  those  of  the  wheat. 


196.  Gelatinisation  of  Starch. — Heat  separate  quantities  of  one  gram  of 
the  starches  of  wheat,  rye,  maize,  rice,  and  potato  in  50  c.c.  of  water  ; and 
notice  the  temperature  at  which  the  liquids  commence  to  thicken  through 
gelatinisation  of  the  starch.  The  experiment  is  conducted  in  the  following 
manner. 

Place  a moderately  large  beaker  on  a piece  of  wire  gauze  over  a tripod, 
as  in  Fig.  8.  Take  several  small  beakers  or  test 
tubes,  and  attach  to  each  a wire  hook,  so  that 
they  may  be  hung  over  the  edge  of  the  large 
beaker.  Fill  this  large  beaker  with  w^ater,  and 
use  it  as  a water  bath.  Put  the  starch  to  be 
tested,  together  with  the  requisite  quantity  of 
water,  in  one  of  the  small  beakers,  and  suspend 
it  in  the  water  bath  ; under  which  place  a 
lighted  bunsen.  While  the  small  beaker  is  thus 
being  heated,  stir  its  contents  with  a thermo- 
meter, and  note  the  temperature  at  which  the 
first  appearance  of  gelatinisation  is  detected  ; 
instantly  remove  the  beaker  and  plunge  it  into 
a vessel  of  cold  water.  When  cold,  examine  a 
little  of  the  paste  with  the  microscope,  and 
notice  whether  or  not  many  of  the  granules 
remain  unaltered.  Make  a second  experiment 
with  the  same  starch,  arresting  the  temperature 
at  2°  hotter  or  colder,  according  to  the  degree  of 
gelatinisation  revealed  by  the  microscope  on  the  Fig.  8. — Apparatus  for 
first  trial.  All  the  starches  specified  are  to  be  determining  Temperature 
tested  m the  same  manner.  Starch 


197.  Reactions  of  Starch  Solution. — Gelatin- 
ise a little  starch  by  heating  it  with  water  in  a test  tube  or  small  beaker 
placed  in  the  hot- water  bath  ; then  let  the  solution  cool. 

Dissolve  some  iodine  in  alcohol,  and  aqueous  solution  of  potassium 
iodide,  respectively.  In  each  case  use  sufficient  iodine  to  just  give  a sherry 
tint  to  the  solution.  Add  some  of  either  of  these  solutions  (that  in  alcohol 
is  commonly  a “ tincture  ”)  to  a small  quantity  of  the  solution  of  starch  ; 
notice  the  blue  colour  produced.  Heat  the  solution,  and  then  allow  it  to 
cool  ; observe  the  disappearance  and  gradual  reappearance  of  the  colour. 

Render  a portion  of  the  starch  solution  alkaline  by  the  addition  of  caus- 
tic soda  or  potash  ; to  one  portion  of  this  solution  add  iodine  ; notice  that 
no  colouration  is  produced.  To  the  other,  add  dilute  sulphuric  acid  until 
the  solution  is  slightly  acid  to  litmus  paper.  Then  add  some  iodine  solution, 
and  observe  that  the  normal  blue  eolour  is  produced.  Add  respectively 
solution  of  iodine  in  potassium  iodide,  and  the  tincture  of  iodine,  to  separate 
small  portions  of  flour  ; notice  the  dark  blue  colour  produced  in  the  first 
instance,  and  the  sherry  tint  in  the  second.  To  the  second  portion  add  a 
little  water  ; the  dark  blue  colour  at  once  appears.  Mount  a minute  por- 
tion of  flour  on  a slide  with  iodine  solu+ion  ; examine  under  the  microscope, 
and  notice  the  blue  colouration  of  the  starch  granules,  while  other  consti- 
tuents of  the  flour  remain  comparatively  uncoloured. 


90 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


198.  Dextrin. — ^Render  some  water  faintly  acid  by  the  addition  of  a 
small  quantity  of  nitric  acid  ; with  this,  moisten  some  starch  in  a porcelain 
dish,  and  maintain  it  at  a temperature  of  200°  C.  in  a hot-air  oven  for  about 
two  hours.  The  hot-air  oven  is  usually  made  of  copper,  and  is  heated  by 
means  of  a bunsen  placed  underneath  ; through  a hole  in  the  top  a ther- 
mometer is  fixed  so  as  to  show  the  temperature.  Before  using  the  oven, 
regulate  the  temperature  by  turning  the  bunsen  partly  on  or  off  until  the 
thermometer  remains  steadily  within  say  10  degrees  of  200.  The  moistened 
starch  must  not  rest  direct  on  the  bottom  of  the  oven  : it  may  be  placed  on 
a small  tripod  made  by  turning  down  the  wires  of  an  ordinary  pipe- clay 
triangle. 

Treat  this  heated  starch  with  hot  Avater,  and  filter  ; a yellowish-brown 
gummy  solution  is  obtained.  To  a portion,  add  iodine  solution  ; notice 
that  no  blue  colouration  is  produced,  but  instead  a reddish-broAvn  tint  - 
starch,  therefore,  is  absent.  The  reddish-broAAm  colour  is  due  to  the  presence 
of  amylo-dextrin.  From  another  portion  of  the  solution,  precipitate  the 
dextrin  by  adding  strong  alcohol  ; filter  and  AA^ash  the  precipitate  Avith  alco- 
hol, dissolve  in  a little  Avater  and  reserve  for  a future  experiment.  Use  a 
little  of  the  solution  for  fastening  together  pieces  of  paper  ; notice  that  it 
exhibits  the  ordinary  properties  of  gum. 

199.  Maltose  and  other  Sugars. — ^Take  from  5 to  10  grams  of  ground 
malt,  and  mix  AAdth  ten  times  the  quantity  of  Avater,  place  the  mixture  in  a 
beaker  arranged  in  a hot-water  bath,  and  keep  it  at  a temperature  of  60°  C. 
for  half  an  hour  : this  may  be  done  by  turning  doAAm  the  flame,  or  alto- 
gether removing  it  from  time  to  time.  The  temperature  may  range  from 
55  to  65°  C.,  but  must  not  be  alloAA^ed  to  go  above  the  latter.  At  the  end  of 
the  half-hour,  raise  the  temperature  to  the  boiling  point  for  five  minutes, 
and  then  filter  ; the  resultant  liquid  is  a solution  of  maltose  and  dextrin, 
and  may  be  used  for  experiments  on  maltose. 

Prepare  solutions  of  the  folloAA^ng  substances,  and  test  them  Avith  Feh- 
ling’s  solution  : (1)  starch  ; (2),  the  re-dissolved  alcoholic  precipitate  of 
dextrin  ; (3),  aqueous  extract  of  malt  ; (4),  cane  sugar  ; and  (5),  commer- 
cial glucose. 

Set  some  distilled  Avater  boiling  in  a flask  or  large  beaker  for  half  an  hour. 
Take  20  c.c.  of  the  mixed  Fehling’s  solution  (see  Chapter  XXIX.),  add  an  equal 
quantity  of  the  boiled  distilled  Avater,  and  set  in  the  boiling  hot-Avater  bath 
for  ten  minutes  ; notice  that  no  precipitate  is  produced.  Heat  five  separ- 
ate portions  of  20  c.c.  of  Fehling’s  solution,  and  20  c.c.  of  Avater  to  the  boiling 
point,  and  add  respectively  20  c.c.  of  the  starch  and  other  solutions  pre- 
viously prepared.  Let  them  all  stand  in  the  hot-Avater  bath  for  ten  minutes  : 
at  the  end  of  that  time  some  of  the  solutions  aa411  probably  be  decolourised 
Avith  the  deposition  of  a copious  red  precipitate,  Avhile  others  Avill  remain 
unchanged.  The  results  should  be  as  folloAvs  : — 

Starch — No  precipitate. 

Dextrin — Very  shght  precipitate,  due  partly  to  the  slight  reducing  action 
of  dextrin  itself,  and  partly  also  to  the  difficulty  of  thoroughly 
Avashing  the  dextrin  free  from  maltose. 

Maltose — Red  precipitate. 

Cane  sugar — No  precipitate. 

Glucose — Red  precipitate. 


CHAPTER  VIL 

THE  PROTEINS. 


200.  Character  of  Proteins. — ^Tlie  proteins,  while  not  the  most  abundant 

constituents  of  wheat  and  flour,  are  yet  among  the  most  important. 
In  whatever  life  exists,  and  in  that  physical  basis  of  life,  protoplasm,  pro- 
teins are  constantly  and  invariably  present.  In  matters  of  animal  origin, 
such  as  muscle,  blood,  milk,  the  proteins  constitute  a larger  proportion  of 
the  water-free  material  than  in  most  vegetable  bodies,  and  much  of  the 
work  of  examining  and  classifying  proteins  has  been  first  done  on  those 
derived  from  animal  sources.  All  animal  proteins  are,  however,  derived 
either  directly,  or  indirectly  through  the  body  of  some  other  animal,  from 
the  proteins  of  the  vegetable  kingdom.  The  name  protein  is  derived  from 
the  Greek  (rpwretov,  pre-eminence),  and  has  been  given  to  these  bodies 
because  of  their  great  importance  in  the  animal  economy.  Typical  among 
the  protein  bodies  is  albumin,  the  essential  constituent  of  the  white  of  egg  ; 
so  much  so  that  the  term  “ albuminous substance  was  often  used  as  a 
synonym  of  protein.  With  a more  minute  classification  of  the  proteins,  the 
term  albumin  was  restricted  to  one  particular  protein  group  ; and  the  term 
“ albuminoid,’'  commonly  employed  as  bearing  the  same  meaning  as  “ pro- 
tein,” was  restricted  to  gelatin  and  certain  othe  bodies  which  are  not 
proteins,  hut  bodies  bearing  a resemblance  or  relationship  to  the  group  of 
which  albumin  is  the  typical  member.  ^ ^ 

201.  Nomenclature  of  the  Proteins. — ^The  proteins  were  formerly  know- 
as  proteids,  but  in  view  of  the  confusion  arising  from  the  lack  of  understands 
ing  as  to  the  exact  sense  in  which  the  various  names  applied  to  protein- 
should  be  used,  the  Physiological  Society  and  the  Chemical  Society  con- 
jointly considered  the  subject  through  a Committee  nominated  by  the  two 
Societies.  Their  final  report  contained  the  following  recommendations  : — 

I-  The  word  Proteid  should  be  abolished. 

II.  The  word  Protein  is  recommended  as  the  general  name  of  the  group 
of  substances  under  consideration.  If  used  at  all,  the  term  Albuminoid 
should  be  regarded  as  a synonym  of  protein.  The  substances  gelatin  and 
keratin,  which  have  hitherto  been  termed  albuminoids  in  the  limited  sense 
in  which  physiologists  have  been  accustomed  to  use  it,  should  be  called  sclero- 
proteins  (Proc.  Chem.  Soc.,  1907,  xxiii,  55). 

This  restricted  use  of  the  term  “ albuminoid  ” has  not,  however,  been 
universally  adopted,  as  the  word  is  still  used  as  meaning  the  same  as  protein, 
while  in  more  recent  nomenclature  the  name  has  been  appropriated  to  a small 
sub-group  of  “ simple  proteins.” 

202.  Composition  of  Proteins. — ^The  proteins  are  distinguished  in  com- 
position from  the  carbohydrates  by  their  containing  nitrogen  and  sulphur 
as  essential  constituents,  in  addition  to  carbon,  hydrogen,  and  oxygen. 
They  are  substances  of  extremely  complex  constitution,  and  have  very  high 
molecular  weights.  They  are  colloid  bodies,  and  for  the  most  part  uncrys- 
tallisable.  The  various  proteins  differ  somewhat  in  composition  : the 
following  table  gives  the  ranges  of  variation  in  percentages  : — 

91 


^2 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


C H N S O 

From  50-0  6*9  15-0  0-1  20-9 

To  55-0  7*3  19-0  2-0  23*5 

From  these  figures  various  observers  have  attempted  to  assign  empiric 
formulae  to  the  proteins  ; but  in  this  there  is  some  difficulty,  as  methods, 
such  as  that  of  Raoult  which  was  so  useful  with  the  carbohydrates,  cannot 
be  applied  to  the  proteins.  Compounds  are,  however,  known  of  egg 
albumin  with  copper,  and  of  seed  globulins  with  magnesium  and  other 
metals,  and  from  these  some  idea  of  the  complexity  of  the  protein  molecule 
can  be  gained.  Thus  the  compound  of  one  atom  of  copper  with  egg  albumin 
has  the  following  formula  : CUC204H322N52S2O66,  while  tfrom  the  globulin 
metallic  compounds  the  formula,  C292H481N90S2O83,  has  been  suggested  for 
globulin.  Plimmer  gives  C726HH74N194S3O214  as  the  formula  of  globin,  the 
basis  of  haemoglobin. 

Within  the  last  ten  years  Fischer  and  his  co-workers  have  done  much 
to  make  clear  the  actual  constitution  of  the  proteins.  Plimmer  in  his 
monograph  on  the  Chemical  Constitution  of  the  Proteins  remarks  that  : 
“ The  main  results  of  these  [Fischer’s]  investigations  is  that  the  protein 
molecule  is  built  up  of  a series  of  amino -acids,  which  form  the  basis  of  their 
composition,  and  of  which  [some  eighteen]  have  been  definitely  determined.” 
By  the  condensation  together,  or  combination  with  the  elimination  of  mole- 
cules of  water,  the  amino-acids  are  converted  into  a class  of  products  which 
Fischer  terms  the  “ polypeptides.”  These  form  an  essential  part  of  the 
protein  molecule,  which  may  also,  however,  contain  other  groups  such  as 
phosphoric  acid  or  possibly  carbohydrates. 

Among  the  amino-acids  which  occur  in  proteins  is  a thio-  or  sulpho- 
acid,  known  as  cystine,  which  is  di-(^-thio-a-amino-propionic  acid),  and 
may  be  represented  by  the  formula — 

SCH2CH(NH2)C00H. 

I 

SCH^CHlNH^jCOOH. 

Recent  research  has  shown  that  cystine  is  the  only  sulphur-containing 
compound  in  the  protein  molecule,  and  consequently  that  the  number  of 
sulphur  atoms  in  such  molecule  must  be  two  or  a multiple  of  two.  As  sul- 
phur is  found  in  all  proteins  (except  the  protamines  and  histones),  it  follows 
that  they  must  all  contain  cystine  as  an  essential  constituent. 

203.  Reactions  of  Proteins. — Protein  substances  are  distinguished  by 
their  evolving  ammonia  on  being  strongly  heated.  This  is  at  once  noticed 
on  burning  pieces  of  quill  or  dried  gluten,  both  of  which  consist  largely  of 
protein  bodies.  If  the  suspected  substance  be  heated  to  near  the  boiling 
point  of  concentrated  sulphuric  acid,  to  which  a little  potassium  sulphate 
lias  been  added,  the  whole  of  its  nitrogen  is  converted  into  ammonium  sul- 
phate, from  which  free  ammonia  is  obtained  by  adding  caustic  soda  in 
excess,  and  subjecting  the  liquid  to  distillation.  This  reaction  forms  the 
basis  of  wliat  is  known  as  Kjeldahl’s  method  for  the  determination  of  nitro- 
gen in  org{\nic  compounds.  In  examining  substances  for  proteins,  and 
especially  in  discriminating  the  various  proteins  from  each  other,  their 
following  characters  are  of  importance — solubility,  heat  coagulation,  indif- 
fusibility,  action  on  polarised  light,  and  colour  reactions. 

Solubility. — All  proteins  are  insoluble  in  absolute  alcohol  and  in  ether. 
vSome  are  soluble  in  water,  others  insoluble  ; among  the  latter,  many  are 
soluble  in  weak  saline  solutions.  Some  proteins  are  soluble  and  others 
insoluble  in  strong  or  saturated  saline  solutions. 


THE  PROTEINS. 


93 


Mineral  and  acetic  acids,  and  also  caustic  alkalies,  dissolve  all  proteins 
by  the  aid  of  heat,  such  solution  being,  however,  accompanied  by  decom- 
position. The  gastric  and  pancreatic  juices  also  dissolve  proteins,  but,  in 
so  doing,  change  them  into  a sub-class  of  proteins,  known  as  peptones. 

Heat  Coagulation. — This  is  a very  familiar  characteristic  of  some  pro- 
teins, chief  among  them  being  albumin  from  the  white  of  egg,  which  on 
being  plunged  into  boiling  water  assumes  an  insoluble  form.  Many  pro- 
teins when  dissolved  either  in  water  or  dilute  saline  solutions  are  coagulated 
by  the  action  of  heat.  The  temperature  at  which  coagulation  occurs  affords 
one  method  of  determining  the  nature  of  the  particular  protein  in  the  solu- 
tion. Distinct  from  heat  coagulation  is  what  is  known  as  ferment  coagula- 
tion, an  instance  of  which  is  the  coagulation  of  milk  by  rennet. 

Indiffusihility. — All  the  proteins  (with  the  exception  of  the  peptones) 
are  highly  colloid  bodies,  and  when  in  solution  may  consequently  be  separ- 
ated from  crystalline  bodies  by  dialysis. 

Action  on  Polarised  Light. — All  proteins  turn  a ray  of  polarised  light  to 
the  left,  or  are  Isevo-rotatory. 

Colour  Reactions — Xanthoproteic  Reaction. — These  are  very  useful 
methods  of  detecting  and  recognising  proteins.  The  Xanthoproteic  reac- 
tion is  obtained  in  the  following  manner  : Add  to  the  solution  under 
examination  a few  drops  of  strong  nitric  acid  ; a white  precipitate  may  or 
may  not  be  produced,  according  to  the  nature  and  degree  of  concentration 
of  the  protein.  (Peptones  and  some  varieties  of  albumose  give  no  precipi- 
tate.) Boil  ; the  precipitate  or  liquid  turns  yellow,  with  usually  some 
solution  of  any  precipitate.  Cool  and  add  ammonia  ; the  yellow  liquid  or 
precipitate  turns  orange.  This  colouration  is  the  essential  part  of  the 
reaction,  and  is  the  most  delicate  test  for  proteins  we  possess. 

Milton’s  Reaction. — Dissolve,  by  the  acid  of  gentle  heat,  one  part  by 
weight  of  mercury  in  two  of  strong  nitric  acid  ; dilute  with  twice  its  volume 
of  water,  and  allow  the  precipitate  to  settle  ; the  clear  supernatant  liquid 
is  Millon's  reagent.  On  the  addition  of  a few  drops  of  this  to  a solution  of 
protein,  a white  precipitate  forms,  which,  on  being  heated,  assumes  a brick- 
red  colour.  The  reaction  is  prevented  by  the  presence  of  sodium  chloride. 
Other  substances  are  precipitated  by  Mil] on’s  reagent,  but  the  precipitate 
does  not  turn  red  on  boiling. 

PiotrowsH’ s or  “ Biuret  ” Reaction. — Add  to  the  solution  of  albumin  or 
similar  protein  a few  drops  of  dilute  solution  of  copper  sulphate  ; a precipi- 
tate of  copper  albuminate  is  formed,  except  with  deutero-albumose  and 
peptone.  Add‘  excess  of  caustic  potash  or  soda,  a violent  solution  is  pro- 
duced. Ammonia  gives  a blue  solution. 

In  the  case  of  albumoses  and  peptones,  the  result  is,  instead,  a rose-red 
solution  with  potash,  and  a reddish-violet  with  ammonia.  Care  must  be 
taken  not  to  add  excess  of  sulphate,  as  so  doing  gives  a reddish-violet  colour, 
very  difficult  to  distinguish  from  this  peptone  reaction.  When  this  test  is 
applied  in  the  presence  of  salt  solutions  it  may  be  somewhat  modified  : thus, 
magnesium  sulphate  is  precipitated  as  magnesia  by  potash  ; before  the 
colour  can  be  observed  the  precipitate  must  be  allowed  to  subside.  If 
ammonium  sulphate  is  present,  a large  quantity  of  potash  is  necessary 
before  the  colour  appears  ; sodium  chloride  does  not  affect  the  reaction. 

204.  Precipitation  of  Proteins. — The  preceding  note  on  the  solubility  of 
proteins  affords  some  clue  to  their  various  modes  of  precipitation,  the  pep- 
tones and  albumoses  being  much  more  soluble  than  other  proteins. 

Solutions  of  the  proteins  may  be  precipitated  by  the  following  bodies  : — 
Strong  mineral  acids,  especially  nitric  acid  ; acetic  acid  ; and  also  with 
excess  of  sodium  sulphate,  sodium  chloride,  or  magnesium  sulphate.  Salts 


94 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  the  heavy  metals,  as  mercuric  chloride  or  basic  lead  acetate,  also  precijh- 
tate  proteins  ; on  suspending  the  precipitate  in  water,  and  passing  a stream 
of  sulphuretted  hydrogen,  the  metal  is  precipitated  and  the  protein  recovered 
in  an  unchanged  form.  In  addition,  proteins  are  precipitated  by  tannin, 
or  tannin  and  sodium  chloride  together  ; by  saturation  with  ammonium 
sulphate  ; by  picric  acid  ; and  by  alcohol  in  faintly  acid  solutions. 

Among  these  the  following  are  convenient  methods  of  removing  proteins 
from  a solution,  either  as  a part  of  the  process  for  their  own  isolation,  or  as 
a prior  step  toward  examining  the  liquid  for  other  substances  : — 

1.  The  solution  is  mixed  Avith  half  its  volume  of  a saturated  solution  of 
common  salt,  tannin  is  added  in  slight  excess,  and  the  proteins  are  entirely 
separated. 

2.  The  solution  is  saturated  AA'ith  ammonium  sulphate,  which  precipi- 
tates all  proteins  but  peptones. 

3.  The  solution  is  rendered  faintly  acid  Avith  acetic  acid,  several  times 
its  volume  of  absolute  alcohol  added,  and  allowed  to  stand  tAA^enty-four 
hours.  The  Avhole  of  the  proteins  are  thus  precipitated. 

4.  When  proteins  of  the  albumin  or  globulin  group  only  are  present, 
simple  acidulating  and  boiling  the  solution  precipitates  the  proteins. 

205.  Glassification  of  Proteins. — ^Proteins  are  commonly  divided  into 
animal  and  vegetable  proteins,  according  to  their  origin.  Strictly  speaking, 
the  animal  proteins  have  but  little  to  do  AAuth  the  present  work,  but  as  their 
classification  is  largely  that  on  aaLIcIi  the  classification  of  those  from  vegetable 
bodies  is  also  based,  a short  account  of  the  animal  proteins  is  here  inserted. 

206.  Animal  Proteins. — ^These  are  conveniently  arranged  in  the  foUoAv- 
ing  groups  : — 

Class  I.  Albumins,  soluble  in  Avater,  in  dilute  saline  solutions,  and 
saturated  solutions  of  sodium  chloride  and  magnesium  sulphate.  Precipi- 
tated from  their  solutions  by  saturation  Avith  ammonium  sulphate.  Coagu- 
lated by  heat,  usually  about  70°-73°C. 

Members  of  class — Serum  albumin,  egg  albumin,  cell  albumin,  muscle 
albumin,  lact-albumin. 

Class  2.  Globulins,  soluble  in  dilute  saline  solutions  ; insoluble  in  water, 
concentrated  solutions  of  sodium  chloride,  magnesium  sulphate,  and  am- 
monium sulphate.  Coagulated  by  heat,  temperature  varying  considerably^ 

Members  of  class — Fibrinogen,  serum  globulin,  crystallin  ; vitelHn,  in 
the  yolk  of  egg,  not  precipitable  by  sodium  chloride. 

Class  3.  Albuminates,  or  Derived  Albumins,  derived  from  either  albu- 
mins or  globulins  by  the  action  of  AA-eak  acids  or  alkalies.  On  heating  a 
solution  of  egg  albumin  to  about  40°  C.  AA'ith  a feAV  drops  of  0*1  per  cent, 
sulphuric  acid  or  0*1  per  cent,  potash  solution,  the  solution  loses  its  pro- 
perties and  becomes  converted  into  acid-albumin  or  syntonin,  or  alkali- 
albumin  respectively. 

Albuminates  are  soluble  in  acid  or  alkaline  solutions  or  in  Aveak  saline 
solutions  ; insoluble  in  pure  Av^ater,  precipitated  like  globulins  by  saturation 
Avith  sodium  chloride,  magnesium  sulphate,  or  ammonium  sulphate.  Solu- 
tions not  coagulated  by  heat. 

Caseinogen,  the  chief  protein  constituent  of  milk,  is  an  albuminate. 

Class  4.  Proteoses,  intermediate  products  in  the  hydration  of  proteins, 
formed  in  the  body  by  the  action  of  the  gastric  and  pancreatic  juices,  arti- 
ficially by  heating  Avitli  water,  and  more  readily  by  dilute  mineral  acids. 
Are  not  coagulated  by  heat,  precipitated  by  alcohol,  all  give  the  biuret 
reaction.  Precipitated  by  nitric  acid,  precipitate  soluble  on  heating,  and 
reappearing  as  the  liquid  cools. 


THE  PROTEINS. 


95 


The  proteoses  are  subdivided  into  albumoses,  globuloses,  etc.,  according 
to  the  original  protein  from  which  derived,  albumin,  globulin,  etc.  Each 
group  of  proteoses  may  be  further  subdivided  in  a similar  manner  ; taking 
albumose,  there  are  two  varieties,  liemi-albumose  and  anti-alhumose,  which 
on  further  digestion  are  converted  into  hemi-peptone  and  anti-peptone 
respectively.  Classified  according  to  their  solubilities,  they  are  divided 
into — 

Proto-albumose,  soluble  in  cold  and  hot  water  and  in  saline  solutions  ; 
precipitated  like  globulins  by  saturation  with  sodium  chloride  or  magnesium 
sulphate. 

Hetero-albumose,  insoluble  in  water  ; soluble  in  0*5-15  per  cent,  sodium 
chloride  solution  in  the  cold,  but  precipitated  by  heating  to  65°.  Precipi- 
tated from  its  solutions  by  dialysing  out  the  salt,  like  globulins.  Precipi- 
tated by  saturation  with  salts.  Proto-  and  hetero-albumose  are  often  called 
primary  albumoses,  because  they  are  the  first  products  of  hydration  of 
proteins. 

Deutero-albumose,  soluble  in  hot  and  cold  water,  not  precipitated  from 
its  solutions  by  saturating  with  sodium  chloride  or  magnesium  sulphate, 
but  precipitated  by  ammonium  sulphate,  is  an  intermediate  stage  in  the 
conversion  of  the  primary  albumoses  into  peptone. 

Class  5.  Peptones  are  the  final  product  of  the  hydration  of  proteins  ; 
further  hydration  splits  up  the  peptone  into  simpler  bodies,  which  are  no 
longer  proteins.  The  peptones  are  soluble  in  water,  not  coagulated  by  heat, 
and  are  not  precipitated  by  nitric  acid,  copper  sulphate,  ammonium  sul- 
phate, and  a number  of  other  precipitants  of  proteins.  Precipitated,  but 
not  coagulated,  by  alcohol.  Precipitated  by  tannin,  picric  acid,  and  other 
substances.  They  give  the  biuret  reaction. 

Pure  peptone  may  be  separated  from  all  other  proteins  by  ammonium 
sulphate  : the  solution  is  then  subjected  to  dialysis  in  order  to  remove  the 
sulphate,  and  the  peptone  precipitated  by  alcohol.  It  may  then  be  dried 
by  washing  with  absolute  alcohol,  ether,  and  finally  standing  in  desiccator 
over  sulphuric  acid,  a vacuum  being  maintained  in  the  desiccator  by  a 
sprengel  or  other  air-pump.  Peptone  thus  prepared  hisses  and  froths  on 
being  dissolved  in  water,  with  evolution  of  heat.  < 

Peptone  is  somewhat  cheesy  in  taste,  but  not  unpleasant.  Artificially 
prepared  peptones,  as  peptonised  milk  or  beef  extract,  have  a bitter  taste. 
This  is  due,  however,  to  some  bitter  substance  not  yet  separated,  native 
peptones  and  albumoses  being  almost  tasteless. 

Hemi-peptones  are  split  up  by  the  pancreatic  juice  into  simpler  products, 
as  leucine  and  tyrosine.  Anti-peptone  is  not  decomposed  in  this  manner. 

Both  varieties  of  peptone  are  readily  dialysable  ; albumoses  are  only 
slightly  diffusible  under  similar  conditions,  while  the  albumins  and  globulins 
are  highly  colloid. 

Class  6.  Coagulated  Proteins. — (a)  Coagulated  by  heat,  are  insoluble  in 
water,  weak  acids,  and  alkalies.  Soluble  after  prolonged  boiling  in  con- 
centrated mineral  acids,  also  in  gastric  and  pancreatic  juice  with  formation 
of  peptones.  (6)  Coagulated  by  ferments,  fibrin  from  blood,  myosin  from 
muscle,  casein  from  milk. 

207.  Vegetable  Proteins. — ^As  previously  stated,  plants  contain  a less 
proportion  of  protein  matter  than  animals.  They  may  be  found  in  solution 
in  the  sap  or  juice  of  plants,  or  in  the  solid  state  in  the  protoplasm  of  the 
plant  cells,  and  in  a comparatively  dry  condition  in  the  ripe  seeds.  Protein 
is  often  found  in  granules  (aleurone  grains).  Some  of  the  vegetable  proteins 
are  obtainable  in  a crystalline  form.  The  classification  adopted  for  the 
animal  proteins  is  in  the  main  applied  to  those  of  vegetable  derivation. 


96 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


208.  More  Recent  Official  Classification. — In  the  years  1907  and  1908 

committees  were  appointed  by  scientific  societies  in  America  and  England 
respectively  in  order  to  settle  a scheme  of  classification  and  nomenclature 
of  the  proteins.  The  American  scheme  was  of  the  two  the  more  complete, 
inasmuch  as  it  definitely  provided  for  the  inclusion  of  the  vegetable  proteins. 
Their  classification  contained  the  following  groups  ; — 

I.  The  Simple  Proteins. 

{a)  Albumins. 

{h)  Globulins. 

(c)  Glutelins. 

{d)  Alcohol-soluble  Proteins  (Prolamins). 

(e)  Albuminoids. 

(/)  Histones. 

{g)  Protamines. 

II.  Conjugated  Proteins. 

{a)  Nucleoproteins. 

(6)  Glycoproteins. 

(c)  Phosphoproteins. 

{d)  Hsemoglobins. 

(e)  Lecithoproteins. 

III.  Derived  Proteins. 

1.  Primary  Protein  Derivatives— 

(g)  Proteans. 

{h)  Metaproteins. 

(c)  Coagulated  Proteins. 

2.  Secondary  Protein  Derivatives — 

(а)  Proteoses. 

(б)  Peptones. 

(c)  Peptides. 

Although  the  classification  of  the  vegetable  proteins  largely  follows  that 
of  animal  proteins,  the  special  character  of  those  of  vegetable  origin  necessi- 
tates some  little  modification  of  the  definitions  as  deduced  from  the  investi- 
gation of  the  animal  compounds. 

The  following  explanations  of  the  various  classes  are  made  vatli  special 
reference  to  the  vegetable  section,  and  do  not  agree  in  every  detail  with  the 
properties  already  given  of  the  animal  groups. 

209.  Simple  Proteins. — Albumins.  These  have  been  already  defined 
as  “ soluble  in  water  and  coagulated  by  heat,’'  but  a more  recent  classifica- 
tion has  been  based  upon  the  behaviour  of  albumins  and  globulins  respec- 
tively to  a half-saturated  solution  of  ammonium  sulphate.  The  portion  of 
])rotein  which  under  these  conditions  remains  in  solution  is  regarded  as 
albumin.  This  does  not  hold  good  with  the  vegetable  albumins,  since  some 
at  least  are  precipitated  by  this  treatment.  Again,  in  the  case  of  the  vege- 
table albumins  it  is  often  difficult  to  say  whether  such  a body  is  soluble  in 
])ure  water,  or  whether  its  solubility  is  due  to  the  presence  of  small  quanti- 
ties of  mineral  salts.  One  of  the  best  studied  vegetable  albumins  is  the  leu- 
cosin  of  wheat,  and  this  is  soluble  in  water  containing  merely  the  slightest 
traces  of  mineral  matter.  The  following  are  examples  of  vegetable  albu- 
mins — 

Leucosin  from  the  seeds  of  viieat,  rye  and  barley. 

Legumelin  from  the  seeds  of  pea  and  lentil. 

Globulins. — The  previous  definition  of  these  states  them  to  be  “ insolu- 
ble in  water,  soluble  in  dilute  saline  solutions  ” ; but  among  the  vegetable 


THE  PROTEINS. 


97 


globulins  are  classed  certain  bodies  Avhicli  only  have  the  properties  of  the 
globulins  when  existing  as  protein  salts  through  combination  with  small 
quantities  of  acid.  On  being  freed  from  this  acid,  they  become  soluble  in 
water,  and  thus  no  longer  conform  to  the  definition  of  the  class.  From 
their  mode  of  preparation  it  is  nevertheless  convenient  to  include  them  in 
this  group. 

Globulins  were  formerly  subdivided  into  two  groups  according  to  whether 
or  not  they  can  be  precipitated  from  a solution  by  saturation  with  sodium 
chloride.  This  operation,  known  technically  as  “ salting-out,""  separates 
the  bodies  known  as  myosins  from  solution.  Those  remaining  unchanged 
were  termed  vitellins.  In  the  case  of  the  vegetable  globulins,  this  distinction 
does  not  hold  good,  as  certain  so-called  myosins  are  in  fact  albumins,  while 
some  vegetable  vitellins  are  only  partly  soluble  in  saturated  sodium  chloride 
solution.  The  body  referred  to  as  wheat  myosin  is  really  the  albumin  leu- 
cosin.  All  vegetable  globulins,  so  far  as  has  been  at  present  ascertained, 
are  completely  precipitated  by  saturation  with  sodium  sulphate  at  a tem- 
perature of  33°  C.  The  animal  globulins  may  all  be  coagulated  by  heat, 
but  most  of  those  of  seeds  are  only  imperfectly  coagulated  by  heating  their 
solutions  even  to  boiling.  A characteristic  of  a number  of  the  vegetable 
globulins  is  that  they  may  be  obtained  in  a crystalline  form,  while  others 
can  be  separated  as  minute  spheroids.  The  following  are  examples  of 
vegetable  globulins  : — 

Legumin  from  the  seeds  of  pea  and  lentil. 

Tuberin  from  the  tubers  of  potato. 

Unnamed  globulin  from  the  seeds  of  wheat. 

The  globulin  of  wheat  is  mostly  if  not  all  contained  in  the  embryo  or 
germ. 

Glutelins. — These  consist  of  proteins  which  are  insoluble  in  neutral 
aqueous  solutions,  saline  solutions,  or  moderately  concentrated  alcohol 
(about  70  per  cent,  spirit).  The  most  characteristic  and  only  well  explored 
member  of  this  group  is  the  glutenin  of  wheat.  Similar  proteins  probably 
exist  in  other  seeds,  such  as  those  of  rye  and  barley,  and  also,  according  to 
Rosenheim  and  Kajiura,  in  rice.  The  rice  glutelin  has  received  the  name 
oryzenin,  and  is  said  to  represent  the  greater  portion  of  the  protein  of  the 
seed. 

Prolamins. — Certain  seed  proteins  are  soluble  in  alcohol  of  from  70  to  90 
per  cent,  strength.  Representatives  of  this  group  have  been  obtained  from 
all  seeds  of  cereals  except  rice  ; further,  they  have  never  been  found  in  the 
seeds  of  any  other  family  of  plants.  The  suggestion  has  been  made  that 
these  proteins  should  be  called  “ gliadins,""  but  as  that  name  has  already 
been  appropriated  to  alcohol-soluble  protein  of  wheat,  Osborne  has  proposed 
the  group  name  of  “ prolamins,""  because  on  hydration  they  yield  consider- 
able quantities  of  proline  and  amide  nitrogen.  The  following  are  examples 
of  prolamins  : — 

Gliadin  from  the  seeds  of  wheat  and  rye. 

Hordein  from  the  seeds  of  barley. 

Zein  from  the  seeds  of  maize. 

< Albuminoids,  etc. — The  remaining  simple  proteins,  albuminoids,  his- 
tones, and  protamines,  are  not  found  to  occur  in  plants. 

210.  Conjugated  Proteins. — Nucleoproteins.  These  bodies,  called  also 
nucleins,  occur  in  the  cells  of  animals  and  plants.  Thus  yeast  yields  a body 
represented,  according  to  Miescher,  by  the  formula  C29H49N9P3022*  This 
substance  contains  phosphorus  in  considerable  quantity  (9*59  per  cent.), 
and  is  extremely  resistant  to  the  action  of  pepsin.  Nucleoproteins  may  be 
regarded  as  compounds  of  nucleic  acid  with  the  proteins,  which  latter  have 

H 


98 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


been  shown  to  have  basic  properties.  Nucleic  acid,  in  turn,  is  viewed  as  a 
compound  of  albumin  with  phosphoric  acid.  Nucleoproteins  are  found  in 
the  protein  constituents  of  wheat  germ. 

Glycoproteins. — These  bodies  are  proteins,  containing  either  a carbo- 
hydrate or  carbohydrate  generating  group  within  their  molecule.  There  is, 
however,  no  definite  evidence  of  the  occurrence  of  glycoproteins  in  plants. 

Phosphoproteins. — Egg  yolk  contains  a protein  of  the  globulin  type,  of 
viiich  phosphorus  is  an  essential  ingredient,  and  to  which  the  name  of 
vitellin  has  been  given.  It  has  been  assumed  that  certain  vegetable  proteins 
are  also  of  this  class  ; but  vitellin  may  be  repeatedly  redissolved  and  re- 
precipitated  without  losing  its  phosphorus,  whereas  vegetable  proteins  con- 
taining phosphorus  are  thereby  completely  freed  from  that  element.  The 
conclusion  is  that  the  existence  of  true  vegetable  phosphoproteins  has  not 
as  yet  been  proved. 

Hcemoglobins,  etc. — It  is  doubtful  whether  any  haemoglobins  have  been 
obtained  from  plants,  while  lecithoproteins  are  also  probably  absent  from 
their  constituents. 

211.  Derived  Proteins. — Primary  Protein  Derivatives.  Substantially,  by 
the  action  of  dilute  acids  and  alkalies,  the  vegetable  proteins  undergo 
similar  changes  to  those  of  animal  origin  when  treated  in  a like  manner. 
The  derived  proteins  are  the  bodies  already  described  as  Class  3 of  animal 
proteins. 

The  proteans  and  metaproteins  do  not  need  description  as  a part  of  the 
present  work. 

Coagulated  proteins. — Many  of  the  proteins  possess  the  property  of  coagu- 
lation by  heat,  especially  in  the  presence  of  a small  quantity  of  free  acid. 
This  holds  good  much  more  with  those  of  animal  origin,  for  the  correspond- 
ing seed  proteins  are  in  most  cases  only  imperfectly  coagulated  by  heating 
their  solutions  even  to  boiling.  Thus  leucosin  from  wheat,  when  obtained 
in  solution  by  the  extraction  of  wheat  flour  with  water,  is  partly  coagulated 
at  a temperature  of  52°  C.,  but  is  not  entirely  so  changed  even  at  the  boihng 
point. 

Secondary  Protein  Derivatives. — Small  quantities  of  proteoses  are  found 
in  seeds,  but  it  is  difficult  to  say  whether  these  existed  as  such  in  the  seeds, 
or  have  been  produced  by  changes  which  have  occurred  during  the  processes 
involved  in  their  separation.  Present  evidence  is  not  sufficient  to  exclude 
the  possibility  of  such  changes,  and  therefore  to  demonstrate  their  existence 
as  original  components  of  the  seeds. 

The  same  difficulties  exist  in  the  way  of  deciding  whether  or  not  pep- 
tones occur  in  plants.  They  may  be  formed  from  vegetable  proteins  by 
boiling  with  dilute  mineral  acids,  or  treatment  with  gastric  or  pancreatic 
juices.  Animal  proteins  are,  as  a rule,  more  easily  peptonised  than  those 
of  vegetable  origin  ; thus  papain,  a vegetable  enzyme,  converts  animal 
proteins  into  peptones,  but  carries  the  change  of  vegetable  proteins  no 
further  than  proteoses. 

212.  Albuminoids. — ^With  the  proposal,  not  universally  adopted,  to 
restrict  this  term  to  a series  of  bodies  outside  the  protein  group,  it  will  be 
well  to  briefly  state  the  character  of  albuminoids  in  this  more  restricted 
sense.  The  tendons  of  animals  contain  a body  known  as  “ collagen,'"  which 
is  insoluble  in  water.  By  the  action  of  dilute  acids  or  boiling  water,  colla- 
gen is  transformed  into  gelatin  : the  process  is  one  of  hydration,  represented, 
according  to  Hofmeister,  by  the  following  equation  : — 


Ci02Hi49N3iO28 

Collagen. 


+ H2O 


Water. 


C102H151N31O: 

Gelatin. 


31^29* 


THE  PROTEINS. 


99 


The  albuminoids,  as  thus  classified,  differ  from  the  proteins  in  that  they 
contain  no  sulphur.  Gelatin  is  insoluble  in  cold  water,  but  dissolves  in  hot 
water,  gelatinising,  or  forming  a jelly,  on  cooling. 

213.  Proteins  of  Wheat. — It  is  a fact  too  familiar  to  need  experimental 
demonstration,  that  the  white  of  egg  coagulates  on  being  heated  ; but  it 
will  be  found  on  further  experiment,  as  may  in  fact  be  gathered  from  the 
preceding  description,  that  if  the  white  of  egg  be  shaken  up  with  consider- 
able quantities  of  water  and  then  heated,  the  albumin  separates  out  in 
coagulated  flocks.  Similarly  on  making  a cold  aqueous  infusion  of  flour,  or, 
still  better,  of  the  germ  of  wheat,  and  then  filtering  the  solution  until  per- 
fectly clear,  a liquid  is  obtained  which,  on  being  raised  to  the  boiling  point, 
throws  down  abundant  flocks  of  albumin  and  globulin.  The  coagulated 
protein  thus  obtained  is  as  white  and  pure  in  appearance  as  that  from  tlie 
white  of  egg,  and  is  closely  allied  to  that  of  mixtures  of  albumin  and  globulin 
of  animal  origin.  While  the  egg  albumin  always  occurs  in  an  alkaline 
liquid,  that  of  vegetables  is  always  found  either  in  acid  or  neutral  liquids. 

Further,  every  miller  and  baker  knows  that  flour,  on  being  moistened, 
forms  a stiff,  tenacious  paste  or  dough  ; he  also  knows  that  the  flour  of 
wheat  is  distinguished  in  a remarkable  manner  from  other  flours  by  this 
character  ; for  oatmeal,  when  similarly  treated,  simply  produces  a damp 
mass,  having  little  or  no  tenacity.  On  kneading  a mass  of  wheaten  dough, 
enclosed  within  a piece  of  muslin,  vith  water,  until  the  starch  is  separated, 
there  remains  behind  a greyish -white  sticky  elastic  mass,  to  which  the  name 
of  “ crude  gluten  is  applied.  This  substance  consists  of  the  insoluble 
proteins  of  the  wheat,  together  with  portions  of  the  ash,  carbohydrates,  and 
oily  matter.  Although  this  gluten,  when  in  the  flour,  existed  as  a powder, 
yet,  on  the  addition  of  water,  it  thus  swells  up  into  a tough  mass.  Gluten 
is  practically  insoluble  in  water,  and  without  taste  ; on  being  dried  by  ex- 
posure to  the  heat  of  the  hot-water  oven,  it  changes  into  a hard  horny  mass. 
Gluten  which  has  been  thus  moistened  with  water,  provided  it  is  dried  at  a low 
temperature,  swells  up  again  on  being  wetted,  although  not  usually  to  such 
a tough  mass  as  when  first  extracted.  Osborne,  with  whom  has  been  associ- 
ated a number  of  other  chemists,  has  for  some  years  been  engaged  in  a sys- 
tematic investigation  of  the  vegetable  proteins  ; in  1893  he,  in  association  with 
Voorhees,  communicated  to  the  American  Chemical  Journal  an  article  of  great 
importance  on  “ The  Proteids  [Proteins]  of  the  Wheat  Kernel.”  This  article 
contains  a historical  resume  of  the  work  previously  done  on  these  compounds, 
and  also  includes  the  results  of  their  own  elaborate  investigations  on  wheat 
proteins,  conducted  on  the  lines  of  the  most  recent  knowledge  of  the  con- 
stitution of  proteins  generally.  The  following  description  is  very  largely 
based  on  Osborne  and  Voorhees’  article,  which  is  still  the  most  authoritative 
exposition  of  the  properties  of  the  wheat  proteins.  It  is,  in  fact,  not  too 
much  to  say  that  science  generally  is  indebted  to  Osborne  for  most  of  the 
work  done  on  the  vegetable  proteins  during  the  last  twenty  years. 

214.  Earlier  Researches. — ^After  recounting  the  results  of  the  researches 
of  Taddei,  Berzelius,  Mulder,  Gunnsberg,  and  others,  Ritthausen’s  conclu- 
sions are  mentioned,  in  which  that  chemist  recognised  in  1872  that  wheat 
contains  five  protein  bodies,  to  which  he  gave  the  names  of  gluten  casein, 
gluten  fibrin,  plant  gelatin  or  gliadin,  mucedin,  and  albumin.  He  expressed 
a doubt  as  to  the  presence  of  albumin,  as  what  was  viewed  as  this  body 
might  possibly  be  a mixture  of  mucedin  and  gliadin. 

In  1880,  Weyl  and  Bischoff  published  the  view  that  the  protein  matter 
of  wheat  is  principally  a myosin-like  globulin,  which  they  call  vegetable 
myosin,  and,  if  this  view  be  correct,  they  further  assume  that  it  is  from  this 


100  THE  TECHNOLOGY  OF  BREAD-MAKING. 

substance  that  gluten  is  derived,  other  proteins  only  being  present  in  small 
quantity.  They  extracted  flour  with  a 15  per  cent,  salt  solution,  and  found 
that  the  residue  yielded  no  gluten  ; they  consequently  assumed  that  gluten 
is  formed  from  myosin  as  a result  of  a ferment  action  similarly  to  the  forma- 
tion of  blood-fibrin  from  fibrinogen.  No  ferment  possessing  such  properties 
could,  however,  be  detected.  Large  quantities  of  sodium  chloride  and 
other  salts  prevent  the  formation  of  gluten  in  the  same  way  as  these  salts 
also  prevent  the  formation  of  fibrin.  On  first  heating  flour  with  alcohol, 
they  found  that  subsequently  no  gluten  could  be  obtained  on  washing,  and 
so  assumed  that  the  myosin  had  been  coagulated.  Also,  on  warming  flour 
for  from  48  to  96  hours,  keeping  the  temperature  below  60°  C.,  the  coagula- 
tion point  of  myosin,  and  then  adding  a little  unwarmed  flour  and  extracting 
gluten  from  the  mixture,  no  gluten  is  obtained  beyond  that  present  in  the 
added  flour,  showing  in  Weyl  and  Bischoff ’s  opinion  that  the  gluten-forming 
substance  had  suffered  coagulation. 

Martin  in  1886  examined  gluten  by  extraction  with  alcohol— he  found 
but  one  protein  substance  so  extracted.  This  body  is  soluble  in  hot  water, 
but  is  insoluble  in  cold,  and  so  is  insoluble  phyt-albumose.  The  residue 
insoluble  in  alcohol  is  uncoagulated  protein,  soluble  in  dilute  acids  and 
alkalies  ; this  he  terms  gluten-fibrin.  The  insoluble  phyt-albumose  is  not 
present  as  such  in  flour,  as  direct  extraction  of  the  meal  with  75  per  cent, 
alcohol  removes  no  protein.  Martin  concluded  that  the  insoluble  phyt- 
albumose  is  formed  from  the  soluble  by  the  action  of  water,  the  gluten- fibrin 
being  formed  by  a similar  action  of  water  on  the  globulin,  that  is,  conversion 
into  an  albuminate.  The  albuminate  and  insoluble  phyt-albumose  together 
constitute  gluten. 

Johannsen,  1889,  combats  the  ferment  theory  of  the  production  of  gluten. 
He  found  that  a normal  dough  was  obtained  by  grinding  dried  gluten  and 
mixing  with  starch,  and  also  by  mixing  moist  gluten  with  starch. 

215.  Osborne  and  Voorhees’  Experiments,  Wheats  used. — One  of  these 
was  a Minnesota  spring  wheat,  Scotch  Fife,  milled  under  chemical  super- 
vision into  “ patent ''  flour  from  finest  and  purest  middlings,  and  “ straights 
from  the  coarser  middlings.  The  “ shorts  ” (red-dog  ? ),  chiefly  composed 
of  inner  portions  of  the  bran,  with  adhering  portions  of  the  endosperm,  was 
also  examined.  Samples  of  whole  wheat  flour  were  prepared  direct  from 
the  wheat  by  grinding  in  the  laboratory  when  required.  A variety  of  winter 
wheat,  known  as  “ Fultz,”  was  also  examined,  but  only  as  whole  wheat 
hour.  Preliminary  investigations  showed  that  all  these  different  hours- 
yielded  protein  matter  to — • 

Diluted  alcohol. 

Water, 

10  per  cent,  sodium  chloride  solution. 

And  after  complete  and  successive  extractions  with  these  reagents, 
to  dilute  potash  water. 

The  bodies  extracted  by  these  various  reagents  will  be  examined  separ- 
ately. 

216.  Proteins  Soluble  in  Water.— In  the  course  of  some  preliminary 
experiments,  £00  grams  of  spring  wheat  straight  hour  were  mixed  with  800 
c.c.  of  distilled  water.  No  coherent  gluten  formed,  the  undissolved  hour 
settling  down  as  a non-coherent  mass.  After  a few  hours’  digestion  the 
solution  was  hltered  ; the  filtrate  was  straw-yellow  in  colour,  becoming 
red-brown  on  standing,  and  had  a venj  slight  acid  reaction. 

Saturation  with  ammonium  sulphate  gave  a bulky  precipitate,  which 
contracted  on  standing,  showing  the  solution  to  contain  but  little  protein 
matter.  After  24  hours  this  precipitate  was  completely  soluble  in  water. 


THE  PROTEINS. 


101 


giving  no  evidence  of  the  formation  of  so-called  albuminates.  Saturation 
with  sodium  chloride  gave  a small  precipitate.  Acetic  acid  in  the  cold  gave 
no  precipitate  until  sodium  chloride  was  added. 

On  slowly  heating,  the  solution  gave  a turbidity  at  48°  C.,  and  a floccu- 
lent  coagulation  at  52°.  After  heating  to  65°  for  some  time  and  filtering, 
the  solution  became  turbid  again  at  73°,  flocks  forming  in  very  small  amount 
at  82°.  Heating  to  boiling  caused  no  further  separation  ; but  the  addition 
of  a little  acetic  acid  and  sodium  chloride  gave  a small  precipitate.  The 
body  coagulating  at  52°  formed  the  greater  part  of  the  protein  in  solution. 
The  complete  coagulation  of  this  required  a temperature  of  65°,  but  was 
greatly  facilitated  by  the  addition  of  sodium  chloride. 

Further  experiments  showed  that  extraction  of  the  flour  with  10  per 
cent,  salt  (sodium  chloride)  solution  yielded  the  same  proteins,  so  that  the 
subsequent  examination  of  the  water-soluble  substances  was  confined  to 
extracts  originally  made  with  10  per  cent,  salt  solution  after  separation  of 
the  globulins  by  dialysis. 

Again,  4000  grams  of  straight  flour  were  treated  with  8 litres  of  10  per 
cent,  brine,  allowed  to  subside  over  night,  and  the  supernatant  liquid  filtered 
off.  Another  2 litres  of  the  brine  were  added  to  the  residue,  which  was 
stirred  up,  allowed  to  settle,  and  again  filtered.  The  filtrate  was  saturated 
with  ammonium  sulphate  as  rapidly  as  collected.  The  precipitate  thus 
procured  was  filtered  and  redissolved  in  10  per  cent,  brine,  filtered  clear, 
and  dialysed  until  the  chloride  had  disappeared.  This  resulted  in  the  pre- 
cipitation of  a globulin,  which  was  filtered  off,  and  the  solution  again  dialysed 
for  14  days,  but  with  no  further  production  of  globulin. 

The  globulin-free  solution  was  next  examined  by  slowly  heating  a por . 
tion — turbidity  occurred  at  48°,  flocks  separating  at  55°.  After  heating  at 
65°,  the  coagulum  was  filtered  off.  Further  heating  resulted  in  a minute 
amount  of  coagulum  being  formed  at  80°  : after  filtering,  there  was  no 
further  precipitate  on  boiling,  and  nothing  was  obtained  by  adding  a little 
salt  and  acetic  acid.  On  adding  20  per  cent,  salt  solution  and  a little  acetic 
acid  to  the  original  solution,  a precipitate  was  caused  ; another  portion  was 
first  heated  to  65°,  and  a third  to  95°,  and  filtered  before  adding  the  salt 
solution  and  acetic  acid.  The  second  gave  less,  and  the  third  least  precipi- 
tate. The  filtrate  from  the  first  of  these  portions,  when  neutralised  and 
boiled,  gave  no  precipitate,  showing  that,  as  was  to  be  expected,  the  separa- 
tion of  albumin  by  precipitation  with  salt  and  acid  was  complete. 

This  globulin-free  solution  gave  a precipitate  on  saturation  with  sodium 
chloride,  the  filtrate  became  flocculent  at  56°,  with  no  further  precipitate 
on  further  heating,  showing  that  the  higher  coagulating  protein  had  been 
thus  removed.  Treatment  of  the  globulin-free  solution  with  nitric  acid 
yielded  a precipitate,  a portion  of  which  dissolved  on  heating,  the  rest  re- 
maining insoluble  : after  filtration,  the  filtrate  deposited  a precipitate  on 
cooling,  which  again  dissolved  on  re-application  of  heat.  The  filtrate  from 
the  salt  and  acid  precipitate  did  not  give  this  reaction,  which  is  characteristic 
of  certain  proteoses,  and  shows  that  the  salt  and  acid  precipitate  contains 
a proteose,  together  with  the  albumins.  Three  distinct  protein  substances 
are  thus  recognised  wFich  are  soluble  in  pure  water  ; two  coagulable,  one 
at  a higher  temperature  than  the  other,  and  presumably  both  albumins  and 
a proteose. 

To  make  sure  that  the  body,  which  was  apparently  an  albumin,  was  not 
a myosin-like  globulin  held  in  solution  by  the  salts  naturally  present  in  river 
water  used  for  dialysis,  a strong  aqueous  solution  of  winter  wheat  meal  was 
dialysed  into  distilled  water  in  the  outer  vessel.  The  solution  still  coagu- 
lated at  54°,  and  contained  in  250  c.c.  only  0*0008  gram  of  mineral  matter, 
proving  the  substance  was  an  albumin. 


102  THE  TECHNOLOGY  OF  BREAD-MAKING. 

217.  Albumins.— The  remainder  of  the  globulin-free  solution,  after 
making  the  foregoing  tests,  was  heated  to  61°,  the  precipitate  filtered,  washed 
with  water,  alcohol,  absolute  alcohol,  and  ether,  dried  over  sulphuric  acid, 
and  heated  to  110°  ; this  was  called  Preparation  1. 

A duplicate  lot  was  prepared  in  the  same  way,  and  yielded  64  grams 
from  10,000  grams  of  flour  ; this  was  called  Preparation  2. 

The  filtrate  from  Preparation  2 was  further  heated  to  75°,  and  the  small 
amount  of  precipitate  washed  A^itli  alcohol  and  dried  as  before  ; this  was 
called  Preparation  3. 

Another  preparation  was  made  on  the  same  flour  by  extracting  with  10 
per  cent,  brine,  and  dialysing  at  once  without  precipitation  by  ammonium 
sulphate.  After  the  separation  of  the  globulins,  the  albumins  were  precipi- 
tated by  at  once  raising  the  temperature  to  90°  ; this,  after  drying,  con- 
stituted the  Preparation  No.  4. 

Another  preparation  was  made  on  the  spring  wheat  “ shorts,  by  ex- 
traction with  10  per  cent,  salt  solution,  treatment  with  ammonium  sulphate, 
dialysis,  coagulating  albumin  at  65°,  and  drying  ; this  was  Preparation  5. 

These  substances  gave  on  analysis  the  following  results  : 


Analyses  of  Coaoulated  Wheat  Albumin. 


1 

1 

1 

_l 

3 

4 

1 

5 

i 

Average. 

Carbon 

53*27 

53*06 

53*02 

52*71 

53*02 

Hydrogen 

6*83 

'■  6*82 

• — 

6*87 

, 6*85 

6*84 

Nitrogen 

16*95 

17*01 

16*94 

16*26 

16*83 

16*80 

Sulphur 

' 1*27 

1*30  i 

— 

1*20 

1*34 

1*28 

Oxygen 

21*68 

' 21*81 

! 

— 

22*65 

1 

22*27 

, 22*06 

1 

100*00  . 

100*00 

— 

! 

• 100-00 

100*00 

‘ 100*00 

! 

These  figures  agree  very  closely,  except  that  the  nitrogen  in  No.  4 is 
low  : as  four  determinations  give  concordant  results,  Osborne  and  Voor- 
hees  consider  it  possible  that  some  of  the  nitrogen  may  be  lost  at  the  higher 
temperature. 

218.  Proteoses. — As  already  stated,  there  are  found  in  the  solution  after 
separating  the  globulins  by  dialysis,  and  the  albumins  by  heating,  small 
quantities  of  one  or  more  proteoses  which  are  almost  wholly  precipitated 
by  saturation  with  sodium  chloride.  On  concentrating  the  filtered  solution, 
after  the  removal  of  albumins  by  heat,  a coagulum  gradually  develops, 
which  must  be  derived  from  the  proteose-like  protein  still  remaining  in 


solution  before  concentration. 

This  body  gave  on  analysis  the  following  figures  : 

. . 51  *86 

Carbon 

Hydrogen  . . 

6*82 
1 ^ o o 

Nitrogen 

. . 1 / *o2i 

Sulphur) 

. . 24  00 

Oxygen ) 

100-00 

The  small  quantity  of  proteose  still  remaining  after  removal  of  the 
coagulum  was  not  separated  for  analysis.  In  analyses  quoted  later,  para- 
graph 233,  the  amount  of  this  proteose  is  seen  to  be  as  much  or  more  than 
tliat  of  the  coagulum. 


THE  PROTEINS. 


103 


219.  Globulin. — The  extraction  of  this  body  has  already  been  referred 
to  : in  a direct  experiment  for  the  preparation  of  globulin,  10,000  grams 
of  “ straight  ” flour  were  extracted  with  34  litres  of  10  per  cent,  salt  solution, 
stirred  and  allowed  to  stand  over  night.  This  was  filtered,  precipitated  by 
saturation  with  ammonium  sulphate,  filtered  and  again  dissolved  in  10  per 
cent,  brine.  The  solution  produced  was  exceedingly  viscid,  and  filtered 
vdth  extreme  difficulty  ; this  was  placed  in  a dialyser  and  left  in  a stream 
of  running  water  until  the  chlorides  were  removed.  The  globulin  gradually 
separated  out  in  minute  particles  of  spheroidal  form.  The  precipitate  was 
filtered,  washed  with  water,  alcohol,  and  ether,  dried  over  sulphuric  acid 
and  then  weighed  5*8  grams.  Globulin,  thus  prepared,  dissolves  in  10  per 
cent,  salt  solution,  from  which  it  is  precipitated  by  the  addition  of  water 
Saturation  with  sodium  chloride  gives  no  precipitate,  but  saturation  with 
magnesium  sulphate,  or  ammonium  sulphate,  completely  precipitates  the 
globulin.  The  solution  in  10  per  cent,  brine  gives,  on  slow  heating,  a very 
slight  turbidity  at  87°,  which  increases  slightly  up  to  99°.  Dried  at  110°, 
this  globulin  constituted  Preparation  8. 

A preparation  was  also  made  in  the  same  way,  except  that  the  precipita- 
tion with  ammonium  sulphate  was  omitted.  Again  the  solution  was  remark- 
ably viscid,  a property  possibly  due  to  the  presence  of  gum,  for  the  pure 
solution  of  globulin  in  10  per  cent,  brine  showed  no  trace  of  it,  neither  did 
an  aqueous  solution  of  the  flour.  On  dissolving  up  the  globulin  obtained 
by  dialysis  in  10  per  cent,  salt  solution,  a residue  remains,  consisting  of  aii 
“ albuminate  ’’  derived  from  the  globulin.  This  globulin  constituted 
Preparation  9. 

The  globulin  was  also  extracted  from  the  “ shorts,'’  and  its  total  quan- 
tity amounted  to  nearly  twice  as  much  as  was  similarly  obtained  from  a 
like  quantity  of  flour.  This  globulin  was  Preparation  10. 

The  globulins  gave  on  analysis  the  following  results  : — 


Analyses  of  Wheat  Globulins. 


; ■ ' s 

___  . _ Jv  . 

9 

10 

Average.  j 

Carbon  . . 

51-07 

51-01 

51-00 

51-03 

Hydrogen 

6-75 

6-97 

6-83 

6-85 

Nitrogen  . . 

..  ; 18-27 

18-48 

18-26 

18-39 

; Sulphur  . . 

23-91  ! 

/ 0-71 

0-66 

0-69  i 

, Oxygen  . . 

1 

t 22-83 

23-25 

23-04  1 

i 

i 

i 

100-00  1 

i 

1 

100-00 

100-00 

100-00  , 

In  contradistinction  to  the  views  held  by  Weyl  and  Bischoff,  and  Martin, 
Osborne  and  Voorhees  have  only  found  in  extracts  of  wheat  meal,  either 
spring  or  winter  wheat,  the  one  globulin  just  described  ; which  in  proper- 
ties and  composition  closely  resembles  those  globulins  found  in  other  seeds. 

220.  Protein  Soluble  in  Dilute  Alcohol ; Gliadin. — ^Whether  wheat  flour 
be  extracted  direct  with  dilute  alcohol,  or  after  treatment  with  10  per  cent, 
salt  solution,  a considerable  amount  of  protein  is  obtained.  The  same  is 
the  case  if  the  previously  extracted  gluten  be  subjected  to  alcohol  extraction. 
Extracts  were  made  by  aleohol  under  all  these  conditions,  and  subjected  to 
repeated  fractional  precipitations,  in  order  to  learn  whether  a single  protein 
body  or  a mixture  had  been  obtained. 


104 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


221.  Direct  Alcoholic  Extraction. — In  direct  treatment  with  alcohol 
5000  grams  of  “ straight  ’’  flour  were  extracted  with  10  litres  of  alcohol,  0*90 
specific  gravity,  and  allowed  to  soak  over  night.  The  mixture  was  then 
stirred,  allowed  to  settle,  and  the  supernatant  liquid  poured  off.  Three 
litres  more  of  alcohol  of  the  same  strength  were  added,  and  presumably 
stirred  in  ; after  standing,  the  clear  liquid  was  poured  off,  and  the  residue 
put  in  a screw  press  and  squeezed  nearly  dry.  The  whole  of  the  liquid  thus 
obtained  was  mixed,  and  constituted  “ Extract  1.""  The  residue  was  again 
treated  with  4 litres  of  0*90  alcohol,  and  once  more  pressed  nearly  dry  ; this 
liquid  was  “ Extract  2.”  The  same  process  was  twice  more  repeated,  and 
the  two  extracts  mixed,  which  gave  “ Extract  3.’"  Each  of  the  three  ex- 
tracts was  filtered  clear,  and  concentrated  separately  to  one-third  its  volume, 
and  after  cooling  decanted  from  the  very  glutinous  viscid  mass  which  had 
separated.  This  precipitated  mass  was  in  each  case  dissolved  in  a small 
amount  of  hot  alcohol,  sp.  gr.  0*90,  and  the  solution  allowed  to  cool  over 
night  : most  of  the  substance  separated  on  cooling,  and  the  liquid  w'as 
decanted  from  it.  The  solutions  were  treated  with  a quantity  of  distilled 
water  and  a little  sodium  chloride  added,  the  protein  was  thus  precipitated, 
washed  with  water,  absolute  alcohol,  and  ether,  and  dried.  The  residue 
was  subjected  to  a series  of  fractional  precipitations  based  on  the  principle 
of  partially  dissolving  with  alcohol  of  0*820  sp.  gr.,  and  precipitating  from 
the  solution  by  the  addition  of  small  quantities  of  sodium  chloride  solution, 
which  precipitate  was  washed,  dehydrated  with  absolute  alcohol,  digested 
with  ether,  and  dried  over  sulphuric  acid.  A portion  of  the  principal  frac- 
tion was  again  divided  by  solution  in  250  c.c.  of  0*90  alcohol,  and  partial 
precipitation  by  pouring  the  solution  into  800  c.c.  of  absolute  alcohol  ; 
precipitate  and  solution  were  again  treated  separately.  As  the  result  of  a 
series  of  fractional  precipitations,  altogether  thirteen  fractions  were  prepared 
and  then  analysed.  These  constituted  Preparations  II  to  23.  The  results  of 
the  whole  series  are  given  by  Osborne  and  Voorhees,  but  five  of  the  fractions 
are  discarded  from  the  final  comparison,  because  of  their  being  impure,  for 
obvious  reasons.  Some,  for  example,  contain  fat,  while  others  have  con- 
centrated in  them  the  solid  matter  which  in  a series  of  filtrations  has  passed 
through  the  filter  papers.  Subjoined  is  given  the  results  of  these  various 
analyses,  and  the  weight  of  each  fraction  which  was  obtained  : — 


Analyses  of  “ Fractions  ” of  the  Wheat  Protein  obtained  by 
Direct  Extraction  with  Dilute  Alcohol. 


1 

15 

16 

17 

1 

19 

21 

24 

25 

26 

Carbon 

52*52 

1 52*77 

52*67 

52*55 

52*74 

52*82 

52*33 

52*38 

Hydrogen.  . 

6*78 

6*78 

6>70 

6-85 

: 6*77 

6*81 

— 

6*91 

7*13 

Nitrogen  . . 

17*64 

17*77 

17*66 

17*94 

' 17*62 

17*67 

17*69 

17*70 

17*82 

Sulphur  . . 

1*08 

1*26 

1*22 

1*21 

1 1*23 

j 1*11 

) 

23*06 

22*67 

Oxygen  . . 

21*98 

21*42 

j 

' 21*75 

L 

21*45 

21*64 

! 21*57 

1 

100*00 

100*00 

100*00 

100*00 

100*00 

1 

100*00 

100*00 

100*00 

Weight  of| 
fraction  in  ■ ' 
gram  j 

12*40 

8*60 

32*26 

5*34 

17*43 

i ' 

63*0  ; 

— 

— 

— 

Nos.  24,  25,  26  are  fractional  re-precipitations  of  fraction  No.  21. 


THE  PROTEINS. 


105 


A study  of  this  series  of  analyses  shows  that  the  whole  of  the  fractions 
-are  in  remarkable  agreement,  and  that  no  fractional  separation  of  the  ex- 
tracted protein  has  been  effected.  For  example,  Nos.  15  and  16,  which  are 
aqueous  solutions,  have  the  same  composition  as  those  from  solution  in 
'0*8£0  alcohol,  and  also  as  the  residue  remaining  after  treatment  with  these 
reagents.  Osborne  and  Voorhees  draw  the  conclusion  that  it  may  be  safely 
eoncluded  that  wheat  contains  but  one  protein  soluble  in  dilute  alcohol. 
The  total  amount  of  protein  contained  in  the  whole  of  these  preparations  is 
207*83  grams,  being  equal  to  4*16  per  cent,  of  the  flour. 

222.  Alcoholic  Extraction  after  Salt  Solution  Extraction. — ^For  this  pur- 
pose 4000  grams  of  “ straight ''  flour  were  taken,  extracted  with  10  per  cent, 
salt  solution  so  long  as  anything  was  removed,  and  then  the  residue  squeezed 
-as  dry  as  possible  in  a screw-press.  This  residue  was  then  treated  with 
alcohol  of  such  a strength  as  to  yield  with  the  water  retained  in  the  flour  as 
nearly  as  possible  a solution  containing  75  per  cent,  of  alcohol.  Digestion 
with  this  solvent  was  continued  for  two  days  ; the  extract  was  squeezed  in 
-a  press,  and  the  process  repeated  three  times,  giving  altogether  four  extracts. 
These  were  concentrated  to  small  bulk,  and  the  solution  decanted  from  the 
separated  mass,  which  was  washed  with  distilled  water,  re-precipitated  by 
sodium  chloride,  washed  with  absolute  alcohol,  digested  with  ether,  and 
■dried  over  sulphuric  acid.  The  precipitates  obtained  from  the  water  wash- 
ings by  adding  salt  were  treated  in  the  same  way.  The  total  weight  of 
these  preparations  was  157*45  grams,  equal  to  3*94  per  cent,  of  flour,  as 
against  4*16  per  cent,  obtained  by  direct  extraction,  showing  that  the  dilute 
alcohol  extract  is  different  and  distinct  from  the  proteins  soluble  in  water. 
These  constituted  Preparations  27-31.  The  following  table  gives  the  result 
of  their  analyses  : — 


Analyses  op  Fractions  ” of  Wheat  Protein  obtained  by  Extraction 
WITH  Dilute  Alcohol  after  Sodium  Chloride  Extraction. 


27 

28 

29 

30 

31 

Carbon  . . 

52-69 

52-72 

52-71 

52-65 

Hydrogen  . . . , i 

6*84 

6-86 

6-81 

6-83 

Nitrogen.  . . . . . | 

17*73 

17-89 

17-75 

17-08 

17*79 

Sulphur  . . 

1-02 

0-95 

1-10 

— 

1*08 

Oxygen i 

i 

21-72  1 

21-58 

21-63 

— 

21-65 

Weight  of  fraction  in| 

100-00 

82-0 

100-00 

57-0 

100-00 

11-3 

1-35 

100-00 

5-8 

grams . . . . . . ) 

Nos.  27-30  are  the  precipitates  obtained  from  the  four  extracts  ; No.  31 
is  obtained  from  the  water  washings  of  27  and  28. 

\ The  results  of  these  analyses  agree  very  closely  among  themselves,  and 
also  with  the  series  obtained  by  direct  alcoholic  extraction. 

223.  Extraction  of  Gluten  with  Dilute  Alcohol. — ^For  the  preparation  of 
gluten,  2000  grams  of  “ straight flour  were  made  into  dough  with  distilled 


106  THE  TECHNOLOGY  OF  BREAD-MAKING. 

water  at  20°,  and  then  washed  in  a stream  of  river  water  at  5°  C.  When 
nearly  the  whole  of  the  starch  had  thus  been  removed,  the  gluten  was  chopped 
fine  and  digested  with  alcohol  of  0*90  sp.  gr.  at  a temperature  of  about  20°. 
This  extraction  was  repeated  with  fresh  portions  of  alcohol  of  the  same 
strength  so  long  as  anything  was  removed.  The  extracts  were  united, 
filtered  clear,  and  evaporated  down  to  one-fourth  their  original  volume. 
This  was  allowed  to  stand  over  night,  and  the  supernatant  liquid  decanted 
from  the  separated  protein.  This  latter  was  then  dehydrated  with  absolute 
alcohol.  The  original  mother-liquor  from  which  the  protein  had  separated, 
and  also  the  absolute  alcohol  used  for  dehydrating,  Avere  each  precipitated 
by  a small  quantity  of  sodium-chloride  solution.  The  three  products  were 
united,  digested  with  absolute  alcohol,  and  then  with  absolute  ether.  After 
drying  over  sulphuric  acid,  the  Preparation'^No.  32  weighed  82*0  grams, 
and  formed  4*10  per  cent,  of  the  flour  taken.  In  order  to  determine  whether 
this  substance  AA^as  a single  protein  or  a mixture  of  more  than  one,  the  pro- 
cess of  fractional  precipitation  Avas  again  employed.  Thirty  grams  of  Pre- 
paration 32  Avere  dissolved  in  0*90  alcohol,  concentrated  to  small  volume, 
and  then  strong  alcohol  added  till  about  half  the  substance  taken  had  been 
precipitated.  The  precipitate  was  treated  Avith  absolute  alcohol,  dried 
over  sulphuric  acid,  and  found  to  AA^eigh  12  grams  ; this  constituted  Pre- 
paration 33.  The  solution  Avas  precipitated  AAith  Avater,  dehydrated  and 
dried  over  sulphuric  acid  ; it  Aveighed  16  grams,  and  Avas  marked  Preparation 
34.  These  substances  had  the  folloAAung  composition  : — 


Analyses  of  ‘‘  Fractions  ” of  the  Wheat  Protein  obtained  by 
Extraction  of  Gluten  aahth  Dilute  Alcohol. 


t 

32 

1 33  1 3-4 

: Carbon 

I 52-58 

52-68  52-84 

Hydrogen 

6-67 

6-78  1 7-18 

Nitrogen 

17-65 

17-65  17-57 

Sulphur 

1-08 

t 92*41 

Oxygen 

22-02 

21-80  I) 

100-00 

100-00  100-00 

i 

In  this  case  also  the  analyses  sIioav  clearly  that  no  separation  into  pro- 
teins of  differing  composition  had  thus  been  effected. 

224.  Extraction  of  “ Shorts  ” with  Dilute  Alcohol. — In  order  to  deter- 
mine Avhether  the  “ shorts  ” or  bran  flour  yielded  the  same  body  to  dilute 
alcohol,  2000  grams  AA'ere  taken  and  subjected  to  much  the  same  process  of 
extraction  as  AAas  flour,  except  that  greater  precautions  Avere  necessary  in 
order  to  remove  impurities.  Taao  Preparations,  Nos.  36  and  37,  were 
obtained,  Avhich  had  the  folloAving  composition  : — 


THE  PROTEINS. 


107 


Analyses  of  Fractions  of  Wheat  Protein  obtained  by 
Extraction  of  “ Shorts  ” with  Dilute  Alcohol. 


36 

1 i 

37 

Carbon 

52-85 

52-74 

Hydrogen 

6-81 

6-87 

Nitrogen  . . 

17-48 

17-67 

Sulphur  . . . . . . . . . . ) 

Oxygen  . . . . . . . . . . j 

22-86 

22-72 

100-00 

100-00 

A comparison  of  tliese  figures  with  those  which  have  preceded  shows 
that  the  protein  extracted  from  the  bran  has  a similar  composition  to  that 
obtained  from  the  flour. 

225.  Extraction  of  Whole  Wheat  Meal  with  Dilute  Alcohol. — ^In  view  of 
the  fact  that  Ritthausen,  and  probably  others,  employed  whole  wheat  meal 
in  their  investigations  of  the  composition  of  wheat  proteins,  Osborne  and 
Voorhees  decided  to  make  some  experiments  on  wheat  meals,  in  addition  to 
those  previously  described.  Accordingly,  1000  grams  of  freshly  ground 
whole  spring  wheat  meal  were  taken,  made  into  a dough,  and  the  gluten 
extracted.  This  was  chopped  fine,  thoroughly  extracted  vith  0*90  alcohol, 
the  extract  concentrated,  and  the  protein  separated  by  cooling.  This  de- 
posit was  dissolved  as  far  as  possible  in  dilute  alcohol,  and  the  insoluble 
substance  washed  with  absolute  alcohol,  and  ether,  and  dried  over  sulphuric 
acid.  This  was  Preparation  38.  The  solution  was  precipitated  with  abso- 
lute alcohol,  dried  as  usual,  and  constituted  Preparation  39  ; the  filtrate 
from  this  was  concentrated  to  small  volume,  poured  into  absolute  alcohol, 
and  the  precipitate  washed  and  dried  as  before,  giving  Preparation  40. 

In  a similar  manner.  Preparations  were  made  from  winter  wheat  meal  ; 
the  coagulated  protein  w as  labelled  41,  and  that  obtained  by  further  diges- 
tion, 42.  These  had  the  following  composition  ; — 

Analyses  of  Wheat  Proteins  obtained  by  Extraction  of  Whole 
Wheat  Meal  whth  Dilute  Alcohol. 


Spring  Wheat. 

1 

Winter  Wheat.  I 

i 

38 

39 

40 

41 

42  : 

Carbon  . . . . . . 

52-90  ^ 

52-89 

53-16 

52-82 

1 

52-68 

Hydrogen  . . . , 

6-99  : 

6-87 

6-83 

6-88 

6-81 

Nitrogen.  . 

17-52 

18-06 

17-75 

17-55 

17-63 

Sulphur  . . 

Oxygen  . . 

1-43 

21-16 

0-92 

21-26 

0-96 

21-30 

1 22-75 

22-88 

100-00 

100-00 

100-00 

100-00 

100-00  j 

108 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Throughout  the  whole  series  there  is  no  essential  difference  in  composition, 
nor  in  physical  properties  ; nor  was  the  protein  altered  in  composition  by 
solution  in  dilute  caustic  potash,  and  re-precipitation  by  an  equivalent 
quantity  of  hydrochloric  acid  ; neither,  so  far  as  it  could  be  observed,  was 
its  solubility  altered. 

The  composition  of  this  protein,  as  obtained  by  averaging  the  preceding 
figures,  is  the  following 


Carbon  . . . . . . . . . . . . ..  52*72 

Hydrogen 6*86 

Nitrogen 17*66 

Sulphur  . . . . . . . . . . . . . . 1*14 

Oxygen 21  *62 


100*00 


226.  Properties  of  Protein  extracted  by  Dilute  Alcohol. — If  this  protein 
be  dehydrated  by  absolute  alcohol,  and  thoroughly  dried  over  sulphuric 
acid,  it  forms  a snow-white  friable  mass  easily  reduced  to  powder.  When 
dried  from  weak  alcohol  or  water,  it  forms  an  amorphous  transparent  sub- 
stance, closely  resembling  pure  gelatin  in  appearance,  being,  however,  rather 
more  brittle  than  that  body.  In  the  cold,  distilled  water  turns  the  substance 
sticky,  and  a part  dissolves.  As  the  water  is  warmed,  the  degree  of  solu- 
bility increases,  and  with  boiling,  a considerable  quantity  goes  into  solution. 
A portion  of  this  is  re-deposited  on  cooling.  The  solution  in  pure  water  is 
instantly  precipitated  by  adding  a very  minute  amount  of  sodium  chloride.  In  abso- 
lute alcohol  this  protein  is  perfectly  insoluble,  but  dissolves  on  the  addition 
of  water,  being  very  soluble  in  70  to  75  per  cent,  alcohol.  From  alcoholic 
solutions,  minute  quantities  of  salt  readily  precipitate  the  protein.  Exceed- 
ingly dilute  acids  and  alkalies  readily  dissolve  this  protein,  which  is  again 
precipitated  apparently  unchanged  in  appearance  and  composition  by 
neutralisation. 

This  protein  has  been  obtained  in  a more  or  less  pure  form  by  earlier 
observers  ; Taddei  first  gave  it  the  name  of  “ gliadin.’"  Ritthausen  and 
others  assumed  that  it  consisted  of  a mixture  of  two  or  more  substances,  to 
which  the  names  of  mucin  or  mucedin,  and  gliadin  or  vegetable  gelatin,  have 
been  given.  Among  recent  observers,  Martin  found  in  gluten  only  one 
protein  soluble  in  dilute  alcohol,  to  which  he  gaye  the  name  of  “ insoluble 
phyt-albumose,”  but,  curiously  enough,  stated  that  flour  extracted  direct 
vith  76  to  80  per  cent,  alcohol  yielded  no  soluble  protein.  This  is  in  direct 
opposition  to  the  results  of  Osborne  and  Voorhees,  and  also,  it  may  be 
added,  to  those  of  the  authors  of  the  present  work,  one  of  whom,  prior  to 
seeing  Osborne  and  Voorhees’  paper,  made  a series  of  analyses  of  various 
flours,  in  which  a direct  gliadin  estimation  by  alcohol  was  included.  These 
results  are  given  in  Chapter  XV,  paragraph  438.  Osborne  and  Voorhees  adopt 
gliadin  as  the  original  and  appropriate  name  for  the  vheat  protein  sclulle  in  dilute 
alcohol.  They  point  out  that  gliadin  is  absolutely  distinct  in  properties  and 
composition  from  the  other  alcohol-soluble  proteins,  prolamins,  obtained  from 
the  kernel  of  oats  and  maize. 

227.  Protein  insoluble  in  Water,  Saline  Solutions,  and  Alcohol ; Clute- 
nin.— After  treatment  with  the  scriis  of  previously  described  solvents,  a 
protein  body  remains  in  wheat  flour  and  gluten,  which  is  soluble  only  in 
dilute  acids  and  alkalies.  This  protein  being  especially  characteristic  of  gluten, 
Osborne  and  Voorhees  have  given  it  the  name  Glutenin. 

In  the  following  accounts  of  extraction  of  glutenin,  it  is  throughout 


THE  PROTEINS. 


109 


understood  that  the  separations  are  made  on  flour  or  meal  which  has  pre- 
viously been  exhausted  with  one  or  more  of  the  following  solvents  : Water, 
10  per  cent,  salt  solution,  and  dilute  alcohol. 

228.  Extraction  of  Glutenin  from  “ Straight  Flour  after  Treatment 
with  Brine  and  Dilute  Alcohol. — -After  completely  exhausting  4000  grams  of 
straight  flour  successively  with  10  per  cent,  brine  and  0*90  sp.  gr.  alcohol, 
the  residue  was  extracted  twice  with  0*1  per  cent,  potash  solution.  The 
residual  protein  was  soluble  in  this,  and  after  standing  three  days  at  a tem- 
perature of  5°,  with  frequent  stirring,  the  extract  was  Altered  off  and  al- 
lowed to  stand  in  a cold  room  until  most  of  the  finer  solid  impurities  had 
subsided.  The  still  turbid  solution  was  then  decanted  and  neutralised 
with  0*2  per  cent,  hydrochloric  acid,  thereby  producing  a precipitate  which 
subsided  rapidly,  leaving  a milky  filtrate.  This  precipitate  was  redissolved 
in  the  dilute  potash,  allow^ed  to  stand  in  order  to  deposit  impurities,  and 
again  precipitated  with  0*2  per  cent,  hydrochloric  acid.  The  protein  was 
w^ashed  with  w^ater,  dilute  alcohol,  absolute  alcohol,  and  ether.  This  pre- 
paration ’svas  found  to  be  far  from  pure,  and  accordingly  a portion  of  it  was 
again  dissolved  in  0 *2  per  cent,  potash,  and  repeatedly  filtered  through  very 
dense  filter  paper  till  perfectly  clear.  As  this  filtration  proceeded  very 
slowly  the  operation  was  conducted  in  a refrigerator  at  a temperature  near 
0°C.  Tw'o  successive  portions  of  the  filtrate  obtained  were  reprecipitated 
with  0 *2  per  cent,  hydrochloric  acid,  w^ashed  with  water,  alcohol,  ether,  and 
dried  over  sulphuric  acid,  and  then  at  110°.  These  gave  Preparations  45 
and  46.  It  was  found  absolutely  necessary  to  Alter  the  potash  solution 
perfectly  clear,  as  otherwise  considerable  amounts  of  non-nitrogenous  matter 
are  subsequently  carried  dowm  with  the  precipitate. 

229.  Extraction  of  Glutenin  after  Treatment  of  Dough  with  Water  and 
Exhaustion  with  Dilute  Alcohol. — ^A  dough  was  made  with  2000  grams  of 
spring  wheat  “ straight  ” flour  and  distilled  water  ; this  was  washed  with 
river  water  till  freed  so  far  as  possible  from  starch.  The  gluten  was  ex- 
hausted with  75  per  cent,  alcohol,  and  the  insoluble  residue  dissolved  in 
0*15  per  cent,  potash  solution,  and  allowed  to  stand  in  a cold  room  for  48 
hours.  The  solution  w^as  decanted,  precipitated  with  dilute  hydrochloric 
acid,  washed  thoroughly  with  water,  absolute  alcohol,  and  ether.  It  w^as 
then  again  dissolved  in  0*1  per  cent,  potash,  allow  ed  to  stand  over  night. 
Altered  till  perfectly  clear,  and  a part  of  the  filtrate  precipitated  by  neu- 
tralising with  0*2  per  cent,  hydrochloric  acid.  This  precipitate  w^as  dried 
as  usual,  and  constituted  Preparation  48. 

Another  lot  of  gluten  w as  prepared  in  the  same  w ay  from  1000  grams  of 
“ straight  ” flour,  extracted  with  alcohol  and  then  dissolved  in  potash  water. 
After  standing,  this  was  precipitated  by  adding  acetic  acid  to  slightly  acid 
reaction.  The  precipitate  Avas  Avashed  AAltli  AA^ater,  alcohol,  and  ether,  and 
again  dissolved  in  potash  AA'ater,  reprecipitated  aaIUi  hydrochloric  acid,  and 
again  AA^ashed  and  dried  as  usual  over  sulphuric  acid.  A pure  AAliite  light 
mass  w^as  obtained,  wliich  was  marked  Preparation  51. 

In  order  to  determine  Avhether  the  protein  lost  any  nitrogen  by  pro- 
longed solution  in  potash  w^ater,  another  lot  of  gluten  AA^as  similarly  treated, 
and  the  potash  solution  kept  in  an  ice-chest  for  £0  hours,  and  then  precipi- 
tated and  treated  in  the  usual  manner.  This  constituted  Preparation  52, 
and  had  evidently  lost  but  exceedingly  little  nitrogen. 

230.  Extraction  of  Glutenin  after  Direct  Exhaustion  of  Flour  with  Alcohol, 
Water  Treatment  omitted. — ^Another  preparation  was  made  by  extracting 
200  grams  of  spring  patent  flour  with  large  quantities  of  alcohol  of  0*90 


110 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


sp.  gr.,  then  washing  the  flour  with  absolute  alcohol  and  drying  and  air-drying 
Tlie  dr}^  flour  was  then  made  into  a dough,  which  possessed  considerable 
coherence,  showing  that  the  protein  insoluble  in  alcohol  has  an  important 
function  in  dough  production.  The  dough  was  washed  on  a hair-sieve  under 
a stream  of  water,  but  yielded  no  coherent  gluten.  The  washings  were 
allowed  to  settle,  and  the  sediment  treated  with  0*2  per  cent,  potash.  After 
standing,  the  supernatant  liquid  was  decanted,  precipitated  with  dilute 
hydrochloric  acid,  and  the  precipitate  allowed  to  settle.  It  was  then  again 
dissolved  in  dilute  potash,  filtered  perfectly  clear  while  in  the  ice-chest, 
reprecipitated,  and  washed  and  dried  in  the  usual  manner.  This  constituted 
Preparation  56. 

Another  experiment  was  made  by  direct  alcohol  treatment,  in  which 
1000  grams  of  “ straight ''  flour  were  exhausted  with  0-90  alcohol,  and  the 
residue  squeezed  in  a screw-press.  This  was  then  extracted  with  0*2  per 
cent,  potash,  but  filtration  was  impossible  owing  to  the  gummy  nature  of 
the  liquid.  An  equal  volume  of  alcohol,  sp.  gr.  0*820,  was  then  added,  and 
after  long  standing  a comparatively  clear  yellow  solution  was  syphoned  off 
and  filtered  clear.  This  was  precipitated  with  hydrochloric  acid,  and  the 
precipitate  filtered  off  and  again  dissolved  in  potash,  filtered  perfectly  clear, 
reprecipitated,  washed  with  water,  dilute  and  then  absolute  alcohol,  and 
ether.  This  yielded  Preparation  57,  the  analysis  of  which  shows  that  the 
same  protein  is  extracted  by  potash  water  from  the  flour  which  has  not  been 
in  contact  with  water  as  was  obtained  in  other  experiments. 

231.  Extraction  of  Glutenin  from  Gluten  of  Whole  Wheat  Flour. — ^A 

dough  was  made  from  1000  grams  of  whole  spring  wheat  meal,  washed  till 
free  from  starch,  and  the  gluten  exhausted  with  dilute  alcohol.  The  residue 
was  dissolved  in  dilute  potash,  allowed  to  stand,  decanted,  reprecipitated, 
and  the  precipitate  washed  with  water,  dilute  alcohol,  absolute  alcohol,  and 
ether,  and  then  re-dissolved  in  0 *2  per  cent,  potash  water.  This  was  filtered 
perfectly  clear,  and  precipitated  and  treated  in  the  usual  way.  The  dry 
protein  was  Preparation  58. 

A preparation  was  made  in  the  same  manner  from  whole  winter  wheat 
meal,  which  constituted  Preparation  60.  In  the  following  table,  analyses 
are  given  of  the  whole  of  the  glutenin  preparations  which  have  been  des- 
cribed. 

Analyses  of  Protein  of  Wheat  soluble  only  in  Dilute  Acids 
AND  Alkalies — Glutenin. 


45 

46 

i 

51 

52 

56 

57 

58 

60 

Carbon 

52-29 

r 

52-32 

52-54 

52-38 

52-19 

5219 

52*03 

Hydrogen.  . 

6-61 

— 

6-82 

6-85 

6-81 

— 

6-92 

6-93 

6*83 

Nitrogen  . . 

17-41 

17-33 

17-61 

17*46 

17*59 

17-20 

17-56 

17*45 

17*48 

Sulphur  . . 
Oxygen  . . 

0-94 

22-75 

— ): 

23-25 

( 107 
(22-08 

1-24 

21-98 

— ) 
— i' 

23-33 

23*43 

23*66 

• 

100-00 

— 

100-00 

lOO-OOi 

100-00 

— 

100-00  100-00^ 

100*00 

i 

232.  Properties  of  Glutenin. — ^The  characteristic  reactions  of  glutenin 
owing  to  its  comparative  insolubility,  are  not  numerous.  A minute  quantity 


THE  PROTEINS. 


Ill 


is  dissolved  by  cold  water,  and  more  on  slightly  warming.  Diluted  alcohol 
also  dissolves  a small  quantity  of  protein  in  the  cold,  and  a larger  quantity 
on  boiling,  which  again  precipitates  as  the  liquid  cools.  It  is  just  possible 
that  this  is  due  to  the  presence  of  traces  of  gliadin,  but  in  face  of  the  very 
oareful  exhaustion  by  alcohol  previous  to  preparation  of  glutenin,  it  is  more 
probable  that  glutenin  itself  is  slightly  soluble  both  in  warm  alcohol  and 
warm  water. 

When  freshly  precipitated  and  hydrated,  glutenin  is  soluble  in  Od  per 
cent,  potash  solution,  and  0*2  per  cent,  hydrochloric  acid.  In  this  condition 
it  is  also  soluble  in  the  slightest  excess  of  sodium  carbonate  solution  or  am- 
monia. After  drying  over  sulphuric  acid,  it  becomes  rather  less  soluble  in 
all  these  reagents.  On  comparing  the  analyses  of  gliadin  and  glutenin,  a 
very  close  agreement  is  observed.  It  is  well  known  that  many  proteins  pass 
readily  into  conditions  in  which  their  solubility  is  changed  without  any 
alteration  in  their  composition,  capable  of  detection  by  analysis.  Osborne 
and  Voorhees  therefore  concluded  that  gluten  was  made  uj3  of  two  forms  of 
the  same  protein,  one  being  soluble  in  cold  dilute  alcohol,  and  the  other  not 
soluble.  But  Osborne,  who  has  since  studied  the  products  of  their  com- 
plete hydrolysis,  finds  that  gliadin  differs  sharply  from  glutenin  in  yielding 
no  glycine  and  no  lysine  ; it  also  gives  nearly  twice  as  much  proline  as  glu- 
tenin (Armstrong,  Su'p'plement,  Jour.  Board  of  Agric.,  June,  1910,  p.  48.) 
It  can  scarcely,  therefore,  be  maintained  that  these  proteins  have  a common 
origin. 

233.  Amount  of  the  various  Proteins  contained  in  Wheat. — ^The  per- 
centage of  each  protein  present  in  whole- wheat  meal  was  determined  by  an 
analysis  on  1000  grams  of  meal  from  spring  and  winter  wheats  respectively. 
The  following  is  an  outline  of  the  analytic  method  adopted,  which  was  the 
same  in  each  case.  To  1000  grams  of  the  fine  meal  were  added  4000  c.c.  of 
10  per  cent,  salt  solution,  and  the  extract  filtered  ; 2500  c.c.  of  clear  extract 
were  obtained  from  the  spring  meal,  and  2600  from  the  winter  wheat  meal. 
As  100  c.c.  of  solution  were  used  to  each  25  grams  of  flour, 

2500  c.c.  = extract  from  625  grams  spring  meal,  and 
2600  c.c.  = ,,  ,,  650  ,,  winter  meal. 

The  extracts  were  dialysed  for  five  days,  at  the  end  of  which  time  they 
were  free  from  chloride.  The  precipitated  globulin  was  filtered,  washed 
with  distilled  water,  alcohol,  absolute  alcohol,  and  ether,  and  dried  at  110°. 
The  following  weights  were  obtained  : — 

3*8398  grams  = 0*624  per  cent,  globulin  in  spring  wheat. 

3*9265  ,,  =0*625  ,,  ,,  ,,  winter  ,, 

The  filtrates  from  the  globulin  were  heated  to  65°,  and  the  coagula 
formed  at  that  temperature  removed  by  filtration,  washed  as  usual,  dried 
at  110°,  and  weighed  with  the  following  results  : — 

1*9714  grams  = 0*315  per  cent.  No.  1 albumin  in  spring  wheat. 
1*9614  ,,  =0*302  ,,  ,,  ,,  winter  ,, 

The  filtrates  from  these  were  heated  to  boiling,  and  the  second  coagula 
similarly  treated.  The  weights  obtained  were  : — 

0*4743  grams  =0*076  per  cent.  No.  2 albumin  in  spring  wheat. 

0*3680  ,,  =0*057  ,,  ,,  ,,  winter  ,, 

The  filtrates  were  evaporated  nearly  to  dryness,  and  two  crops  of  coagu- 
lated protein  removed,  washed,  dried,  and  weighed — together  they  amounted 
to  : — 

1*6886  grams  = 0*269  per  cent,  coagulum  in  spring  wheat. 

1*4516  ,,  =0*223  ,,  ,,  ,,  winter  ,, 

The  filtrates  from  the  coagula  were  next  again  evaporated  to  a syrup 
and,  as  no  insoluble  matter  separated,  were  precipitated  by  pouring  into 


112 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


strong  alcohol,  the  precipitates  were  washed,  dissolved  in  water  and  repre- 
cipitated, washed  with  absolute  alcohol  and  ether,  and  dried  at  110°.  They 
were  evidently  very  impure,  and  the  amount  of  protein  present  in  each  was 
estimated  by  determining  the  nitrogen  and  multiplying  by  6 ‘25.  They 
gave  in  this  way  the  following  results  : — 

1*3297  grams  = 0*213  per  cent,  proteose  and  peptone  in  spring  wheat. 
2*8083  ,,  =0*432  ,,  ,,  ,,  ,,  winter  „ 

Collecting  these  figures,  the  sodium-chloride  solution  contained  the 
following  amounts  of  protein  matter  : — 


Globulin 

Two  Albumins  together 
Coagulum  . . 

Proteosf^ 


SpriQg  Wh3at. 


0*624  per  cent. 

0*391 

0*269 


0*213 


Winter  Wheat. 


0*625  per  cent. 


0*359 


?> 


0*223 

0*432 


Total 


1*497  „ 1*639 


The  remainder  of  the  protein  matter  constitutes  the  gluten,  and  was 
determined  in  the  following  manner — 200  grams  of  each  meal  were  made 
into  a dough  and  washed  free  from  starch.  The  wet  gluten,  freed  from 
adhering  moisture,  was  then  weighed,  and  exactly  one-half  dried  at  110° 
to  constant  weight. 

Spring  wheat  yielded  12*685  per  cent,  dry  gluten. 

Winter  ,,  ,,  11*858  ,,  ,,  „ 

The  other  half  of  the  gluten  was  cut  up  fine,  and  extracted  with  alcohol 
of  0*90  sp.  gr.  The  extract  was  concentrated,  and  the  precipitated  protein 
extracted  with  ether  and  dried  at  110°.  Reckoned  on  the  whole  meal, 
Spring  wheat  gluten  yielded  4*3379  per  cent,  gliadin. 

Winter  ,,  ,,  4*2454  ,,  ,, 

The  residues,  after  exhaustion  with  alcohol,  were  then  dried  at  110° 
and  weighed.  Reckoned  on  the  whole  meal. 

Spring  wheat  gluten  yielded  7*800  per  cent,  matter  insoluble  in  alcohol. 
Winter  ,,  „ „ 7*504 

Nitrogen  determinations  were  then  made  on  the  following  bodies — the- 
whole  meal  insoluble  alcohol  residues,  .dried  gluten,  and  the  sediments  of 
the  water  used  for  washing  out  gluten,  after  being  washed  with  strong  alcohol, 
dried  and  weighed.  The  following  is  the  tabulated  result  of  the  various- 
determinations  : — 


Proximate  Analysis  of  Proteins  of  Wheat. 


Total  nitrogen  in  the  meal  . . 

Spring. 

1*950  per  cent. 

Winter. 

1*940  per  cent. 

Total  gluten  in  the  meal 

12*685 

11*858 

Part  of  gluten  insoluble  in  alcohol  . . 

7*800 

7*504 

Per  cent,  of  nitrogen  in  gluten 

12*010 

12*000 

Total  nitrogen  in  gluten  in  per  cent,  of 
hour 

1*5222  „ 

1*4230  „ 

Total  nitrogen  in  residue  of  gluten  in- 
soluble in  alcohol . . 

0*8245  „ 

0*7346  „ 

Total  nitrogen  extracted  by  alcohol . . 

0*6977  „ 

0*6884  „ 

Gliadin  (Nx5*68,  assuming  17*60  per 
cent,  of  N in  gliadin) 

3*9630  „ 

3*9100  ., 

Gliadin  by  direct  weighing  . . 

4*3379  „ 

4*2454  „ 

Nitrogen  in  sediment  from  washing 
gluten 

0*2239  „ 

0*1552  ,, 

THE  PROTEINS. 


113 


i 

1 

Spring  Wheat. 

Xitiogen.  Protein. 

Wi.NTER  Wheat. 

Xitrogen.  Protein. 

! Glutenin  . . 

0-8245  x5-68= 

4*683 

0*7346x5*68= 

4*173 

1 Gliadin 

0*6977x5*68=: 

3*963 

0*6884x5*68= 

3*910 

j Globulin  . . . . 

0*1148  = 

0*624 

0*1148  = 

0*625 

! Albumin  . . 

0*6057  = 

0*391 

0*0603  = 

0*359 

Coagulum . . 

0*0453  = 

0*269 

0*0379  = 

0*223 

1 Proteose  . . 

0*0341  = 

0*213 

0*0791  = 

0*432 

From  Water  Wash- 

ings of  Gluten.  . 

0*2239x5*68= 

1*272 

0*1552x5*68= 

0*881 

Total 

2*0050 

11*415  , 

1*8703 

10*603 

Meal  . . 

2T0  x5-68  = 

1193  ; 

1-94  x5-68  = 

:10  96 

Inspection  of  the  above  figures  shows  that  the  gliadin  by  direct  weighing 
agrees  fairly  well  vdth  that  estimated  from  a nitrogen  determination.  The 
residue  insoluble  in  alcohol  is,  however,  very  much  more  than  the  true 
glutenin  : thus,  in  the  spring  wheat  the  insoluble  residue  weighed  7*80  per 
cent,  of  the  meal,  whereas  the  glutenin  calculated  from  nitrogen  amounted 
to  only  4*683,  leaving  3*117  of  foreign  matter  in  the  residue  insoluble  in 
alcohol.  The  total  protein  agrees  in  each  case  very  closely  with  the  whole 
found  by  direct  estimation  on  the  meal.  The  same  figures  as  those  above 
given  are  quoted  in  a work  recently  written  by  Osborne  (1609)  as  repre- 
senting the  amounts  of  proteins  contained  in  the  grain  of  wheat. 

234.  The  Formation  of  Gluten. — So  far  as  is  known,  wheat  is  the  only 
plant  whose  seeds  contain  proteins  in  such  a form  as  to  enable  them  to  be 
separated  in  a coherent  mass  from  the  other  constituents  by  washing  with 
water.  Osborne  and  Voorhees  have  examined  very  carefully  the  views 
promulgated  on  this  point  by  previous  observers  ; prominent  among  these 
is  the  “ ferment  ” hypothesis  of  Weyl  and  Bischoff,  who,  as  previously 
stated,  considered  the  proteins  of  wheat  meal  to  consist  principally  of  a 
globulin  very  similar  in  character  to  myosin,  and  which  they  therefore 
termed  “ vegetable  myosin.''  This  they  regarded  as  the  mother-substance 
of  gluten,  which  on  the  addition  of  water  is  changed  by  a ferment,  hitherto 
unisolated,  into  gluten,  “ as  other  proteins,  if  present  at  all,  exist  only  in 
small  amount  " (Weyl  and  Bischoff).  The  exhaustive  analyses  previously 
quoted  show  that  globulin  and  also  gliadin  form  only  about  half  the  total 
])rotein  of  the  grain.  Osborne  and  Voorhees  point  out  that  gliadin  is  ex- 
tracted in  similar  quantity  from  dry  flour  direct  by  alcohol,  as  is  yielded 
after  treatment  with  10  per  cent,  sodium  chloride  solution,  or  by  direct  ex- 
traction of  the  previously  washed  out  gluten.  Weyl  and  Bischoff  state 
that  with  the  aid  of  a 15  per  cent,  salt  solution  the  flour  was  extracted  till 
no  protein  could  be  detected  in  the  extract  ; the  residue  of  the  meal  kneaded 
with  water  then  gave  no  gluten.  “ If  the  globulin  substance  is  extracted,  no 
formation  of  gluten  takes  place.’*  Osborne  and  Voorhees  confirm  this  if  the 
flour  is  stirred  up  with  a large  quantity  of  salt  solution,  and  then  extracted 
repeatedly  with  fresh  quantities  of  the  solution.  But  they  say  : “ If,  however, 
wheat  flour  is  mixed  at  first  with  just  sufficient  salt  solution  to  make  a firm 
dough,  this  dough  may  then  be  washed  indefinitely  with  salt  solution,  and 
will  yield  gluten  as  well  and  as  much  as  if  washed  with  water  alone." 

This  statement  alone  is  scarcely  a sufficient  disproof  of  Weyl  and  Bis- 
choff's  position.  In  a firm  dough  made  with  15  per  cent,  salt  solution,  the 
quantity  of  salt  will  only  amount  to  5 per  cent,  of  the  dough.  As  nothing 


114 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


has  been  removed  in  the  act  of  making  dough,  it  may  be  reasonably  claimed 
that  this  quantity  of  salt  is  insufficient  to  prevent  the  ferment  performing 
its  function,  and  thus  producing  gluten  ; while  further,  the  gluten  once 
formed  is  able  to  withstand  the  action  of  the  salt  solution  which  is  unable 
to  decompose  it.  Osborne  and  Voorhees  go  on  to  state  that  “ when  large 
quantities  of  salt  solution  are  applied  at  once,  the  flour  fails  to  unite  to  a 
coherent  mass,  and  cannot  afterwards  be  brought  together.’'  This  action 
of  salt  solution  in  large  quantities  is  explained  by  subsequent  experiments, 
in  which  it  is  shown  that  such  solution  materially  modifies  the  adhesive 
nature  of  gliadin. 

Weyl  and  Bischoff’s  experiment,  in  which  they  extracted  the  flour  mth 
90  per  cent,  alcohol,  is  scarcely  conclusive,  because  according  to  both  h3rpo- 
theses  this  would  result  in  the  non-formation  of  gluten.  In  the  one  case 
globulin  would  be  coagulated,  and  in  the  other  gliadin  would  be  removed, 
and  so  according  to  both  reasoners  no  gluten  could  be  produced. 

More  recently,  Martin  has  advanced  a somewhat  similar  theory  of  gluten 
formation  ; he  finds  one  protein  in  gluten  soluble  in  alcohol,  and  in  hot 
water,  but  not  in  cold,  which  protein  he  calls  an  insoluble  phyt-albumose. 
The  gluten  is  termed  by  him  “ gluten-fibrin.”  Martin  next  inquires  : Does 
flour  contain  gluten-fibrin  ? Does  it  contain  insoluble  phyt-albumose  ? 
He  states  that  the  first  question  cannot  be  answered  directly,  and  that,  if 
phyt-albumose  originally  existed  in  the  flour,  it  should  be  extracted  by  76-80 
per  cent,  alcohol,  which,  however,  extracts  only  fat.  There  is  here  direct 
conflict  of  experimental  evidence,  as  the  analyses  previously  quoted  show 
that  considerable  quantities  of  a protein  are  thus  extracted.  Martin  next 
points  out  that  10  per  cent,  sodium  chloride  solution  extracts  a large  quantity 
of  globulin  of  the  myosin  type  and  of  albumose.  Osborne  and  Voorhees 
consider  that  Martin  has  made  the  mistake  of  taking  albumin  for  a myosin- 
like globulin,  and,  owing  to  the  voluminous  nature  of  the  body  when  coagu- 
lated, has  been  misled  as  to  its  amount.  Martin  further  looks  upon  the 
insoluble  albumose  as  formed  from  the  soluble,  and  that  the  globuhn  is 
transformed  into  gluten-fibrin.  That  a body  should  be  obtained  from  a 
solution  of  globulin,  which  gave  the  same  reactions  as  gluten- fibrin,  is  not 
surprising,  as  so-called  albuminates,  having  no  characteristic  reactions,  are 
derived  from  nearly  all  globulins.  Martin  tabulates  his  theory  as  follows  : — 

p _ I Gluten-fibrin  — precursor,  globulin. 

LUTEN  I Insoluble  albumose — ,,  soluble  albumose. 

Osborne  and  Voorhees  cannot  admit  this  theory,  because  it  is  founded 
on  two  erroneous  observations  : 1st,  that  80  per  cent,  alcohol  does  not 
extract  protein  from  flour  ; 2nd,  that  at  least  one-half  the  protein  of  the 
seed  is  a myosin-like  globulin. 

Osborne  and  Voorhees  conclude  that  no  ferment  action  is  involved  in 
the  formation  of  gluten,  and  that  it  contains  but  two  protein  substances, 
glutenin  and  gliadin,  and  that  these  exist  in  the  wheat  kernel  in  the  same 
form  as  in  the  gluten,  except  that  in  the  latter  they  are  combined  with 
about  thrice  their  weight  of  water.  This  opinion  is  based  on  the  following 
reasons  : — 

1.  Alcohol  extracts  the  same  gliadin  in  the  same  amount,  whether 
applied  directly  to  the  flour,  to  the  gluten,  or  to  the  flour  previously  ex- 
tracted with  10  per  cent,  sodium  chloride  solution. 

2.  Dilute  potash  solution  extracts  glutenin  of  uniform  composition 
and  properties  from  flour  which  has  been  extracted  with  alcohol,  or  with 
10  per  cent,  sodium  chloride  solution  and  then  with  alcohol,  as  it  extracts 
from  gluten  which  has  been  exhausted  with  alcohol. 

Viewed  as  a refutation  of  the  ferment  theory,  the  weak  point  of  this 


THE  PROTEINS. 


115 


statement  is  that  in  order  to  prepare  gliadin  the  flour  is  in  all  cases  treated 
with  water,  as  even  the  alcohol  used  contains  water  to  the  extent  of  30  per 
cent,  (although  extraction  with  70  per  cent,  alcohol  is  a condition  the  reverse 
of  favourable  to  ferment  action).  The  advocates  of  the  ferment  theory 
might  adduce  the  fact  that  small  quantities  of  ferment  substance  are  capable 
of  changing  very  large  quantities  of  the  body  on  which  the^^  act,  and  further 
might  suggest  that  the  small  quantity  of  globulin  which  is  removed  by 
treatment  with  sodium  chloride  solution  is  the  ferment  in  question.  It  is 
well  known  that  flour  contains  a diastase  precipitated  by  alcohol,  which 
presumably  belongs  to  the  albumins  or  globulins  ; it  is  therefore  conceivable 
that  among  the  globulin,  albumin,  and  indefinite  proteoses  of  wheat,  a fer- 
ment may  exist  capable  in  the  presence  of  water  of  producing  gliadin  from 
some  other  pre-existing  substance.  It  is  difficult,  however,  to  prove  »a 
negative,  and  the  onus  of  proving  the  existence  of  ferment  action  lies  rather 
with  those  who  are  advocates  of  that  hypothesis  than  with  those  who  view 
it  as  unnecessary.  Osborne  and  Voorhees,  without  actually  absolutely 
disproving  the  existence  of  a gluten-ferment,  account  rationally  and  scienti- 
fically for  the  production  of  gluten  on  the  assumption  of  the  pre-existence  of 
its  constituents  as  such  in  the  grain  ; the  balance  of  evidence  is  strongly 
in  favour  of  the  latter  hypothesis. 

The  following  experiments  are  adduced  to  show  that  both  glutenin  and 
gliadin  are  necessary  for  the  production  of  gluten.  A portion  of  flour  was 
washed  free  from  gliadin  by  alcohol  of  0*90  sp.  gr.,  and  next  with  stronger 
alcohol,  and  finally  with  absolute  alcohol,  and  air  dried.  The  residue  made 
a tolerably  coherent  dough,  but  much  less  tough  and  elastic  than  that  ob- 
tained from  the  untreated  flour.  On  w’ashing  this  dough  most  carefully, 
not  a trace  of  gluten  could  be  obtained. 

In  another  experiment  7 *5  grams  of  finely  ground  air- dried  gliadin  w^ere 
mixed  with  70  grams  of  starch,  and  distilled  water  added.  A plastic  dough 
was  formed,  but  it  had  no  toughness.  On  adding  a little  10  per  cent,  sodium 
chloride  solution  the  dough  became  tough  and  elastic.  This  was  washed 
with  great  care  with  cold  water,  a little  salt  solution  being  added  from  time 
to  time  ; no  gluten  was,  however,  obtained. 

The  following  experiment  shows  that  additional  gluten  is  formed  when 
glutenin  is  present,  by  the  adding  of  gliadin.  Two  portions  of  100  grams 
each  of  flour  were  taken,  and  to  one  of  them  5 grams  of  gliadin  added.  Both 
were  made  into  dough  with  the  same  quantity  of  water.  The  two  doughs 
exhibited  considerable  differences,  that  containing  the  extra  gliadin  being 
the  yellower  and  tougher  of  the  tw^o.  Gluten  was  extracted  from  each  by 
washing,  after  which  each  was  weighed  in  the  wet  condition,  that  containing 
the  added  gliadin  weighed  44*55  grams,  and  the  other  27*65  grams.  On 
drying  at  110°  the  yield  of  dry  gluten  Avas  respectively  15*41  grams  and 
9*56  grams  ; the  difference  being  5*85  grams,  Avhich  amount  more  than 
covers  the  added  gliadin. 

On  heating  finely  ground  air-dried  gliadin  with  a small  quantity  of  dis- 
tilled water,  a sticky  mass  is  formed  which,  on  the  addition  of  more  distilled 
water,  forms  a turbid  solution.  But,  if  to  the  gliadin  moistened  with  dis- 
tilled water  a very  dilute  solution  of  salt  in  distilled  Avater  is  added,  the 
gliadin  is  changed  into  a very  coherent  viscid  mass  Avhich  adheres  to  every- 
thing it  touches,  and  can  be  draAAm  out  into  long  threads.  Treatment  of 
gliadin  Avith  10  per  cent,  salt  solution,  first  to  moisten  it,  and  afterAA^ard  in 
larger  quantity,  serves  to  cause  the  substance  to  unite  in  a plastic  mass  Avhich 
can  be  drawn  out  into  sheets  and  strings,  but  is  not  adhesive.  This  explains 
the  non-success  of  Weyl  and  Bischoff’s  experiment  before  referred  to.  The 
gliadin  is  the  binding  material  which  causes  the  particles  of  flour  to  adhere 
together,  thus  forming  a dough.  But  the  gliadin  alone  is  not  sufficient  to 


116 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


form  gluten,  for  it  yields  a soft  and  fluid  mass  which  breaks  up  entirely  on 
washing  with  water.  The  insoluble  glutenin  is  probably  essential  as  afford- 
ing a nucleus  to  which  the  gliadin  adheres,  and  from  which  it  is  not  mechani- 
cally carried  away  by  the  wash  water. 

235.  Summary. — ^The  following  are  the  properties  and  composition  of 
the  proteins  of  the  wheat  grain  : — 

1.  A globulin,  soluble  in  saline  solutions,  precipitated  therefrom  by 
dilution,  and  also  by  saturation  with  magnesium  sulphate  or  ammonium 
sulphate,  but  not  by  saturation  with  sodium  chloride.  Partly  precipitated 
by  boiling,  but  not  coagulated  at  temperatures  below  100°.  The  grain 
contains  between  0*6  and  0*7  per  cent,  of  globulin. 

2.  An  albumin,  coagulating  at  52°,  which  differs  from  animal  albumin 
in  being  precipitated  on  saturating  its  solutions  with  sodium  chloride,  or 
with  magnesium  sulphate,  but  not  precipitated  by  completely  removing 
salts  by  dialysis  in  distilled  water.  The  grain  contains  between  0*3  and 
0*4  per  cent,  of  albumin. 

3.  A proteose,  precipitated  (after  removing  globulin  by  dialysis,  and  the 
albumin  by  coagulation)  by  saturating  the  solution  with  sodium  chloride, 
or  by  adding  20  per  cent,  of  sodium  chloride  and  acidulating  Avith  acetic 
acid.  Separates  as  a coagulum  on  concentrating  the  solution,  and  thus 
yields  about  0*3  per  cent,  of  the  grain. 

The  solution  from  this  coagulum  still  contained  a proteose-like  body 
which  was  not  obtainable  in  a pure  state.  By  indirect  methods  it  is  assumed 
to  amount  to  from  0 *2  to  0 *4  per  cent,  of  the  grain.  Both  these  substances,, 
the  coagulum  and  the  proteose-like  body,  are  derivatives  of  some  other 
protein  in  the  seed,  presumably  the  proteose  first  mentioned.  As  previously 
explained,  it  should  be  borne  in  mind  that  the  proteoses  may  be  formed 
during  the  processes  of  extraction  by  alterations  of  the  protein  matter 
originally  present  in  the  grain. 

4.  Gliadin,  soluble  in  dilute  alcohol,  and  soluble  in  distilled  water  to- 
opalescent  solutions,  which  are  precipitated  by  adding  a little  sodium 
chloride.  Completely  insoluble  in  absolute  alcohol,  but  slightly  soluble  in 
60  per  cent,  alcohol,  and  very  soluble  in  70-80  per  cent,  alcohol,  and  is  pre- 
cipitated from  these  solutions  on' adding  either  much  water  or  strong  alcohol,, 
especially  in  the  presence  of  much  salts  ; soluble  in  very  dilute  acids  and 
alkalies,  precipitated  from  these  solutions  by  neutralisation,  unchanged  in 
])roperties  and  composition.  The  formation  of  gluten  is  largely  dependent 
on  this  protein.  The  grain  contains  about  4*25  per  cent,  of  gliadin. 

5.  Glutenin,  a protein  insoluble  in  Avater,  saline  solutions,  and  dilute 
alcohol,  AA^hich  forms  the  remainder  of  the  proteins  of  the  grain.  Soluble 
in  dilute  acids  and  alkalies,  and  re-precipitated  from  such  solutions  by 
neutralisation. 

The  folloAA'ing  is  the  composition  of  these  bodies  : — 


Analyses  of  Proteins  of  Wheat. 


j 

Globulin. 

Albumin. 

1 

Coagulum. 

Gliadin.  j Glutenin. 

Carbon  . . 

51-03 

53-02 

51-86 

52-72  ! 52-34 

Hydrogen 

6-85 

6-84 

6-82 

6-86  i 6-83 

, Nitrogen.  . 

18-39 

16-80 

17-32 

17-66  17-49 

Sulphur  . . 

0-69 

1-28 

y 94.00  ■ 1 

1-14  1-08 

OxA^gen  . . 

23-04 

22-06 

^ \j\j  ^ \ 

21-62  22-26 

1 

100-00 

100-00 

100-00 

100-00  100-00 

THE  PROTEINS. 


117 


Wheat  gluten  is  composed  of  gliadin  and  glutenin,  both  being  necessary 
for  its  formation.  Gliadin  forms  with  water  a sticky  medium  which, 
by  the  presence  of  salts,  is  prevented  from  becoming  wholly  soluble.  This 
medium  binds  together  the  particles  of  flour,  rendering  the  dough  and  gluten 
tough  and  coherent.  Glutenin  imparts  solidity  to  the  gluten,  and  forms 
the  nucleus  to  which  gliadin  so  adheres  that  it  cannot  be  washed  away  with 
water.  Gliadin  and  starch  form  a dough  which  yields  no  gluten,  as  the 
gliadin  is  washed  away  with  the  starch.  Flour  freed  from  gliadin  gives  no 
gluten,  as  there  is  no  binding  material  to  hold  the  particles  together  so  that 
they  be  brought  into  a coherent  mass. 

Soluble  salts  are  also  necessary  in  forming  gluten,  as  in  distilled  water 
gliadin  is  readily  soluble.  The  mineral  constituents  of  the  flour  are  sufficient 
for  this  purpose,  as  gluten  can  be  obtained  by  washing  a dough  in  distilled 
water. 

No  ferment  action  occurs  in  the  formation  of  gluten,  for  its  constituents 
are  found  in  the  flour  having  the  same  composition  and  proportions  as  in  the 
gluten,  even  under  those  conditions  which  would  be  supposed  to  completely 
remove  antecedent  proteins,  or  to  prevent  ferment-action.  All  the  pheno- 
mena which  have  been  attributed  to  ferment-action  are  explained  by  the 
properties  of  the  proteins  themselves,  as  they  exist  in  the  seed  and  in  the 
gluten. 

The  conclusions  of  Osborne  and  Voorhees  agree  well  with  the  following 
opinions  on  a gluten-ferment  expressed  by  one  of  the  present  authors  in  a 
previous  work  on  this  subject  ; — “ The  existence  of  this  body  cannot  as  yet, 
however,  be  recognised  as  proved.  While  the  formation  of  gluten  may  be 
due  to  the  intervention  of  such  a body,  yet  there  is  nothing  remarkable  in 
considering  it  to  be  a simple  and  direct  hydration,  by  water,  of  the  gluten 
compounds  existent  in  the  grain.  The  effect  of  heating  the  flour,  and  of 
treatment  with  salt  solution,  are  fairly  accounted  for  by  their  well-knowii 
coagulating  action  on  the  albuminous  matters.  So,  too,  those  wheats  whose 
flours  hydrate  slowly  are  grown  under  conditions  which  favour  the  proteins 
being  in  a difficultly  soluble  condition.'' 

236.  Proteins  of  the  Oat- Kernel. — ^For  purposes  of  comparison  the 
following  statement  by  Osborne  of  the  composition  of  the  proteins  of  oats 
is  given.  When  oat-meal  is  extracted  with  10  per  cent,  sodium  chloride 
solution,  two  portions  of  uncoagulated  protein  were  obtained  ; after  which 
alcohol  extracted  another  uncoagulated  protein.  Two  distinct  proteins 
are  thus  obtained  from  oats — that  extracted  from  untreated  oats  readily 
coagulates  and  becomes  insoluble  in  alcohol,  and  when  wet  with  absolute 
alcohol  does  not  absorb  moisture  from  the  air  ; whilst  that  obtained  from 
oats  after  treatment  with  salt  solution  has  no  tendency  to  coagulate,  is 
freely  soluble  in  cold  alcohol  of  0*90  sp.  gr.,  and  when  wet  with  absolute 
alcohol  absorbs  moisture  from  the  air  and  becomes  gummy.  Both  sub- 
stances, when  washed  with  absolute  alcohol  and  dried,  are  light  yellowish 
powders,  soluble  in  dilute  acids  and  alkalies,  and  reprecipitated  on  neutralis- 
ing their  solutions  {American  Chemical  Journal). 

2Z1,  Distribution  of  Proteins  in  Wheat. — ^The  proteins  of  wheat  are  not 
distributed  equally  throughout  the  whole  seed,  there  being  certain  portions 
of  the  wheat  grain  which  are  specially  rich  in  soluble  proteins  ; the  bran  and 
germ  are  particularly  so.  Starting  from  the  outside  of  the  seed,  the  interior 
portions  become  less  and  less  nitrogenous,  until  the  kernel  of  the  grain  is 
found  to  consist  much  more  largely  of  starch. 

238.  Decomposition  of  Proteins. — Soluble  albumin,  or  the  white  of  egg, 
on  being  allowed  to  stand,  putrefies,  with  the  evolution  of  sulphuretted 


118 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


hydrogen  and  other  gases.  The  odour  of  sulphuretted  hydrogen  is  almost 
invariably  described  by  comparison  to  that  of  rotten  eggs.  Coagulated 
albumin,  when  dry,  is  a fairly  stable  body  ; but,  when  left  in  contact  with 
water,  putrefies,  yielding  valeric  and  butyric  acids,  together  with  other 
bodies.  The  oxygen  of  the  air  has  no  action  on  albumin. 

Dry  gluten  may  be  kept  indefinitely  without  change,  but  if  when  wet 
it  is  exposed,  in  masses  too  large  to  dry  quickly,  to  air  at  ordinary  tempera- 
tures, it  gives  off  a quantity  of  gas,  and  at  last  evolves  a strong  putrescent 
odour.  At  the  same  time,  the  insoluble  gluten  breaks  down  into  a thick 
creamy  mass. 

239.  Nature  of  Putrefaction. — It  is  necessary  to  get  accurate  ideas  of 
what  putrefaction  really  is.  Every  one  knows  the  results  of  putrefaction  in 
their  last  or  extreme  stages  ; animal  and  vegetable  substances  both  give  off 
gases  having  most  disgusting  odours,  and  yield  a variety  of  offensive  pro- 
ducts. These  gases  consist  of  compounds  of  hydrogen  with  carbon,  and 
also  with  sulphur  ; this  latter  gas,  termed  by  the  chemist  sulphuretted 
hydrogen,  is,  as  just  stated,  responsible  for  the  odour  so  characteristic  of 
rotten  eggs.  In  the  earlier  stages,  however,  of  putrefaction,  the  changes 
do  not  result  in  the  j)roduction  of  such  disagreeable  bodies  ; gases  are 
evolved,  but  these  are  either  inodorous  or  at  most  possess  only  slight  smells. 
Speaking  broadly,  putrefaction  consists  of  the  breaking  down  or  degrading 
of  the  complex  molecules  of  animal  and  vegetable  structures  into  compounds 
of  a more  simple  character,  and  ultimately  into  inorganic  compounds,  such 
as  carbon  dioxide,  water,  and  sulphuretted  hydrogen  ; which  latter,  in  its 
turn,  deposits  its  sulj)hur,  and  forms  water  by  the  action  of  atmospheric 
oxygen.  Bodies  in  the  first  stage  of  putrefying  absorb  more  or  less  oxygen  ; 
when  this  element  has  been  removed  from  the  supernatant  air,  a species  of 
fermentation,  known  as  putrefactive  fermentation,  proceeds.  When  dealing 
w ith  the  whole  question  of  fermentation  this  change  must  be  viewed  more 
closely.  At  present  there  is  one  particular  point  that  should,  however,  be 
mentioned,  and  that  is,  that  by  heating  any  organic  liquid,  as  a solution  of 
hay,  white  of  egg,  or  proteins  of  fiour,  under  pressure  at  a temperature  of 
about  266°  F.  for  some  time,  and  then  boiling  the  liquid  in  a flask  whose  neck 
is  loosely  plugged  with  cotton  wool  until  the  whole  of  the  air  is  expelled,  the 
liquid  acquires  the  property  of  resisting  putrefactive  action.  Solutions 
preserved  in  this  manner  may  be  kept  for  an  indefinite  length  of  time  ; on 
iieing  once  more  exposed  to  the  air  they  again  are  subject  to  putrefaction. 
It  would  thus  appear  that  putrefaction  is  not  a process  appertaining  ex- 
clusively to  the  grain  itself,  but  is  in  some  way  dependent  on  the  action  and 
j)resence  of  air. 

Experimental  Work. 

240.  Reactions  of  Proteins. — Separate  a little  gluten  from  flour  by 
kneading  dough,  enclosed  in  muslin,  in  water.  Dry  a little  of  this,  and  heat 
•strongly  in  a test-tube  ; notice  that  an  odour  is  evolved  similar  to  that  of 
burning  hair  or  feathers.  Water  also  condenses  in  the  cooler  parts  of  the 
tube  ; test  this  water  vlth  a strip  of  red  litmus  paper,  and  notice  that  it  has 
an  alkaline  reaction  ; this  alkalinity  is  caused  by  the  presence  of  ammonia. 
Make  a precisely  similar  experiment  with  some  white  of  egg,  and  observe 
that  the  same  reactions  occur. 

Solubility. — Mix  some  white  of  egg  with  about  four  times  its  volume  of 
water.  Place  a portion  of  this  solution  in  a test-tube,  float  it  in  a beaker 
of  cold  water,  and  heat  gently.  Test  the  temperature  at  which  coagulation 
t^n.sues.  To  successive  portions  of  the  albumin  solution,  add  alcohol,  ether, 
iuercuric  chloride,  and  picric  acid  solutions,  and  dilute  nitric  acid  : notice 


THE  PROTEINS.  119 

the  formation  of  a precipitate.  To  the  portions  precipitated  by  acid,  add 
caustic  soda  or  potash  solution  ; the  precipitates  are  re-dissolved. 

Colour  Reactions. — Test  the  Xanthoproteic  and  Millon’s  colour  reactions, 
as  described  in  paragraph  203. 

Precipitation. — Precipitate  proteins  from  solutions  by  the  various  methods 
given  in  paragraph  204. 

Production  of  Peptones. — Take  some  of  the  white  of  a hard-boiled  egg, 
and  rub  it  through  a fine  sieve.  Add  to  it  some  dilute  hydrochloric  acid 
(0*2  per  cent.)  and  a little  prepared  pepsin.  Gently  warm  the  whole  to  a 
temperature  of  about  40°  C.,  and  notice  that  the  white  of  egg  dissolves. 
The  albumin  has  then  been  converted  into  peptone. 

Soluble  Flour  Proteins. — Weigh  out  50  grams  of  flour,  and  mix  with  250 
c.c.  of  water  in  a large  flask,  shake  up  thoroughly  several  times  during  half 
an  hour,  and  then  set  aside  for  a few  hours,  or  even  over-night.  Filter  thel 
supernatant  liquid  through  a French  filter  paper  until  bright.  Heat  a 
portion  of  this  solution  in  a small  beaker  placed  in  a water-bath  : notice 
the  coagulation  of  vegetable  albumin. 

241.  Gluten  and  its  Constituents. — ^The  separation  of  gluten  will  have 
been  illustrated  in  the  preceding  experiments.  Moisten  flour  with  alcohol 
and  fold  up  in  muslin  ; knead  in  a small  vessel  also  containing  alcohol  : 
notice  that  no  gluten  is  yielded.  Make  a similar  experiment  with  a 15  per 
cent,  salt  solution  ; place  a sample  of  flour  for  the  night  in  the  hot  water 
oven,  and  treat  with  ordinary  water  in  the  morning  : observe  in  each  case 
that  no  gluten  is  produced. 

Place  aside  some  moist  gluten  and  water  in  an  outhouse  : notice  day 
after  day  the  changes  which  occur  in  the  appearance  and  physical  properties 
of  the  gluten  as  putrefaction  sets  in. 

Take  some  carefully  washed  gluten  and  grind  it  up  in  a mortar  with  a 
little  80  per  cent,  alcohol.  Transfer  to  a flask  and  keep  at  a temperature 
of  40°  C.  for  some  hours  ; filter,  and  again  grind  the  undissolved  residuum 
with  more  alcohol  in  the  mortar.  Again  digest  in  the  flask,  and  once  more 
repeat  this  treatment.  Evaporate  down  the  mixed  filtrates  over  a water- 
bath,  and  notice  the  transparent  yellow  gliadin  thus  obtained.  Carefully 
dry  the  insoluble  portion,  which  consists  of  more  or  less  pure  glutenin. 

The  extent  to  which  this  series  of  experiments  is  carried  must  depend  on 
the  time  and  opportunities  of  the  student,  and  also  the  laboratory  facilities 
at  his  disposal. 


CHAPTER  VIII. 


ENZYMES  AND  DIASTATIC  ACTION. 

242.  Hydrolysis. — ^It  has  already  been  incidentally  mentioned  that 
starch  may  readily  be  converted  into  dextrin  and  maltose  ; Avith  regard 
to  the  carbohydrates  generally,  one  of  their  special  characteristics  is,  that 
the  less  hydrated  members  of  the  series  are  easily  changed  to  those  con- 
taining a higher  proportion  of  hydrogen  and  oxygen.  In  consequence 
of  the  great  importance  of  these  transformations,  they  will  require  to  be 
dealt  with  fully.  The  present  chapter  will,  therefore,  give  particulars  of 
the  nature  of  these  changes,  the  agents  by  which  they  are  effected,  and 
the  conditions  which  are  favourable  or  unfavourable  to  their  occurrence. 
As  the  mutations  of  the  carbohydrates  consist  of  the  addition  of  the  ele- 
ments of  water  to  the  atoms  previously  present  in  the  molecule,  it  has  been 
proposed  to  include  these  changes  under  the  general  term  “ hydrolysis."" 
Hydrolysis  is,  therefore,  defined  as  a chemical  change,  consisting  of  the  assimilation, 
by  the  molecule  of  the  substance  acted  on,  of  hydrogen  and  oxygen  in  the  same 
proportions  as  they  exist  in  water  ; and  resulting  in  the  producticn  of  a new  chemical 
compound  or  compounds.  Those  bodies  capable  of  producing  hydrolysis 
are  termed  “ hydrolysing  agents ""  or  “ hydrolytics.""  In  order  that 
hydrolysis  may  occur  it  is  obviously  necessary  that  water  shall  be  present. 

243.  Hydrolytic  Agents. — ^These  bodies  include  oxalic  and  dilute  hydro- 
chloric and  sulphuric  acids.  Commencing  with  soluble  starch,  the  acids 
mentioned  possess  the  power  of  converting  that  body  first  into  dextrin 
and  maltose,  then  into  glucose.  The  acid  hydrolytics  also  transform  cane 
sugar  into  glucose.  It  will  be  noticed  that  the  ultimate  products  of  hydro- 
lysis of  starch  are  sugars  of  various  descriptions,  hence  this  operation  is 
frequently  termed  the  “ saccharification  ""  of  starch. 

244.  Saccharification  of  Starch  by  Acids. — This  operation  is  carried  on 
as  a commercial  process  for  the  manufacture  of  glucose  for  use  in  breAving. 
The  starch  is  boiled,  either  in  open  vessels  or  under  pressure,  Avith  dilute 
sulphuric  acid.  If  the  operation  be  stopped  as  soon  as  a portion  of  the 
solution  gives  no  blue  colouration  when  tested  AA’ith  iodine,  it  will  be  found 
that  dextrin  and  maltose  are  the  chief  products.  Continued  boiling  results 
in  the  transformation  of  most  of  the  dextrin  and  maltose  into  glucose. 
The  sulphuric  or  oxalic  acid,  Avhichever  is  used,  is  next  removed  by  the 
addition  of  calcium  carbonate  in  slight  excess.  This  reagent  forms  an 
insoluble  oxalate  Avith  the  latter  acid,  and  Avith  the  former,  calcium  sul- 
phate, Avhich  is  only  very  slightly  soluble.  The  precipitate  is  allowed 
to  subside  and  the  supernatant  liquid  evaporated  under  diminished  pressure. 

245.  Catalysis. — ^When  soluble  starch  is  saccharified  by  the  action  of 
an  acid  such  as  oxalic  acid,  it  is  found  that  the  acid  itself  does  not  disappear 
during'  the  reaction.  If  the  necessary  precautions  be  taken,  the  same 
quantity  of  unaltered  acid  is  found  at  the  termination  of  the  chemical 
cliange  as  Av^as  introduced  prior  to  its  commencement.  This  leads  us  to 
institute  a comparison  betAA^een  actions  of  the  type  now  under  consideration  • 
and  others  frequently  met  Avith  in  more  general  chemistry.  Taking  chem- 

120 


ENZYMES  AND  DIASTATIC  ACTION. 


121 


ical  changes  as  a whole,  they  may  be  resolved  into  those  of  two  classes, 
-(1)  those  in  which  the  reaction  is  practically  immediate  on  the  mixture 
of  the  interacting  bodies,  as  when  hydrochloric  acid  and  sodium  hydroxide 
are  added  to  each  other  in  solution  and  at  once  form  the  neutral  sodium 
chloride,  and  (2)  those  in  which  the  chemical  change  occupies  an  appreciable 
time.  As  an  illustration  of  the  latter  the  combination  of  sulphur  dioxide 
with  oxygen  to  form  sulphur  trioxide  in  the  presence  of  water  may  be  men- 
tioned. Now  in  the  case  of  many  reactions  of  the  second  type,  there  are 
.substances  which  remarkably  accelerate  the  speed  of  the  reaction,  without 
themselves  undergoing  a permanent  chemical  change.  Thus,  if  a small 
quantity  of  nitrogen  oxide,  NO,  be  added  to  the  aforesaid  mixture  of  sulphur 
dioxide  and  oxygen,  it  marvellously  increcoses  the  rapidity  of  combination 
of  these  bodies,  and  that  without  in  itself  undergoing  permanent  alteration. 
This  is,  in  fact,  the  method  employed  in  the  manufacture  of  sulphuric 
acid,  and  were  there  no  purely  secondary  reactions,  the  nitrogen  oxide 
might  be  entirely  recovered  as  such  at  the  close  of  the  chemical  process. 
This  process  of  changing  the  rate  of  a slow  chemical  action  is  termed  “ catalysis,” 
and  the  active  agent  therein  is  termed  a “ catalyst.”  Among  the  essentials  of 
catalytic  action  is  that  the  catalyst  does  not  induce  the  chemical  change 
but  only  alters  the  rate  of  one  already  proceeding  ; and  further,  the  catalyst 
does  not  combine  with  any  of  the  products  of  the  reaction. 

In  the  case  of  many  chemical  reactions,  an  important  point  is  that 
they  only  proceed  until  a certain  condition  of  equilibrium  is  reached. 
Thus  if  a compound  is  subjected  to  such  conditions  as  lead  to  its  dissociation 
into  the  constituent  elements,  there  is  a position  in  which  there  will  be 
neither  complete  combination  nor  complete  dissociation.  There  will  be 
simultaneously  present  free  atoms  or  molecules  of  the  elements  and  molecules 
of  the  compound.  If  an  additional  quantity  of  the  compound  is  added, 
dissociation  will  proceed  until  the  point  of  equilibrium  is  again  reached  ; 
or  if  combining  proportions  of  the  elements  are  added,  combination  will 
•ensue  till  again  the  position  of  equilibrium  is  attained.  In  a chemical 
reaction  that  is  accelerated  by  the  introduction  of  a catalyst,  and  in  which 
there  is  an  intermediate  point  of  equilibrium,  the  same  catalyst  that  speeds 
the  reaction  to  this  point  will  have  a reverse  action  if  added  to  the  sub- 
stances beyond  the  equilibrium  point.  Thus  taking  the  hydrolysis  of 
cane  sugar  to  glucose,  there  is  in  fact  a point  at  wdiich  the  action  ceases, 
and  on  that  point  being  reached,  there  is  present  some  cane  sugar  and 
also  glucose  and  fructose.  If  glucose  and  fructose  only  be  subjected  to 
the  action  of  the  same  catalyst,  a reverse  action  proceeds  until  cane  sugar 
and  glucose  and  fructose  are  present  in  equilibrium  quantities.  Thus 
the  same  catalyst  which  hydrolyses  cane  sugar  .into  the  simpler  bodies, 
may  also  synthesise  cane  sugar  from  these  substances. 

246.  Enzymes  or  Soluble  Ferments. — Another  most  important  group 
of  catalytic  agents,  which  are  capable  of  inducing  hydrolysis,  consist  of 
certain  soluble  bodies  of  organic  origin.  Among  such  substances  are  human 
saliva,  filtered  aqueous  infusions  of  yeast,  flour,  bran,  and  malt.  Chemical 
research  show  s that  in  each  case  hydrolysis  is  due  to  the  nitrogenous  con- 
stituents of  these  various  agents.  In  several  instances  the  active  principle 
has  either  been  isolated  or  obtained  in  a very  concentrated  form  ; it  is 
not  known,  however,  wdth  certainty  w^hether  these  bodies  are  definite 
chemical  compounds,  or  w^iether  they  are  only  mixtures  of  certain  nitro- 
genous bodies  in  a particularly  active  state. 

These  substances  form  part  of  a yet  larger  group  of  bodies  which  for- 
merly were  indiscriminately  classed  together  as  “ ferments,""  that  is,  bodies 
which  were  capable  of  inducing  fermentation.  At  present  this  latter  term, 


122 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


as  is  explained  in  a subsequent  chapter,  is  confined  to  those  chemical  actions 
which  are  the  work  of  certain  micro-organisms  ; and  the  changes,  such  as 
hydrolysis,  that  are  due  to  active  principles  which  are  not  organised  or 
living,  form  a separate  class.  These  active  principles  have  been  termed 
soluble-ferments  ; but,  as  in  order  to  avoid  confusion  with  micro-organisms 
and  fermentation,  it  is  well  to  dissever  them  entirely  from  the  idea  of  fer- 
mentation, the  term  “ enzyme  has  been  proposed,  and  is  now  generally 
adopted.  It  has  also  been  proposed  to  group  together  all  the  chemical 
changes  due  to  enzymes  under  the  generic  term  of  “ enzymosis.’’ 

A number  of  chemical  reactions  are  brought  about  by  enzymes,  most 
of  which,  however,  are  instances  of  hydration  of  the  bodies  acted  on.  Enzy- 
mosis  occurs  usually  most  readily  at  temperatures  about  40°  C.,  and  is 
characterised  by  the  fact  that  a minute  quantity  of  the  enzyme  is  capable 
of  causing  the  characteristic  chemical  change  in  a comparatively  enormous 
quantity  of  the  substance  acted  on,  without  itself  apparently  undergoing 
change.  In  other  words,  these  substances  behave  as  catalysts.  An  enzyme 
may  therefore  be  defined  as  a substance  produced  by  living  organisms,  and  capable 
of  acting  catalytically  on  contiguous  compounds. 

247.  Chemical  Properties  of  Enzymes. — These  substances  can  be  extracted 
from  the  bodies  containing  them  by  the  action  of  water,  dilute  alcohol, 
salt  solutions,  or  glycerin.  From  these  solutions  they  may  be  precipitated 
by  strong  alcohol,  lead  acetate,  or  saturation  with  ammonium  sulphate. 
This  precipitate,  on  being  washed  with  absolute  alcohol  and  dried  in  vacuo, 
yields  a friable  mass  easily  reduced  to  a white  powder,  and  in  composition 
either  protein  or  closely  allied  to  protein  matter.  The  enzymes  act  most 
vigorously  at  a temperature  of  from  40  to  45°  C.,  and  are,  in  the  moist 
state,  destroyed  by  a temperature  of  from  50  to  75°  C.,  according  to  the 
nature  of  the  enzyme.  (Certain  enzymes  when  absolutely  dry  withstand 
a temperature  of  as  much  as  170°  C.)  The  presence  of  free  acid  or  alkali, 
and  also  small  quantities  of  certain  neutral  salts,  as  ammonium  sulphate, 
are  inimical  to  enzymosis. 

248.  Classification  of  Enzymes. — ^Among  the  number  of  enzymic  actions, 
comparatively  few  are  of  importance  in  the  study  of  the  present  subject  ; 
these  are  placed  first  in  the  accompanying  table,  while  others  of  less  imme- 
diate value,  but  still  of  interest  as  illustrative  of  the  whole  scheme  of 
enzymosis,  follow. 

Osborne  and  Voorhees’  researches  rather  negative  the  existence  of  Weyl 
and  Bischoff’s  hypothetical  vegetable  myosin  ; but,  if  the  contrary  were 
the  case,  the  natural  place  of  this  enzyme  would  be  as  shown  in  class  6. 
The  fact  that  there  are  members  of  this  class  which  can  perform  analogous 
functions  in  blood  and  muscle  did  much  toward  paving  the  vay  for  the 
inception  of  the  theory  of  there  being  a gluten-forming  enzyme. 

249.  Cytase. — ^As  early  as  1879,  Brown  and  Heron  mentioned  that 
during  the  germination  of  grain  the  cellulose  cell- walls,  and  also  the  cellulose 
of  the  starch  granules,  are  broken  down.  Brovn  and  Morris  again  call 
attention  to  the  same  fact  in  their  paper  on  the  “ Germination  of  some 
of  the  Graminese,”  Jour.  Chem.  Soc.,  1890,  p.  458.  As  germination  pro- 
ceeds, tlie  parenchymatous  cell-walls  of  the  endosperm  are  gradually  dis- 
solved, and  ultimately  leave  no  sign  of  separation  between  the  contents 
of  the  contiguous  cells.  During  the  progress  of  these  changes  the  endosperm 
is  much  softened,  and  attains  the  condition  of  “ mealiness  ” aimed  at  by 
the  maltster  in  course  of  the  germination  of  barley  in  malt  manufacture. 
Brown  and  Morris  find  that  this  production  of  mealiness  is  undoubtedly 
co-terminous  with  the  dissolution  of  tlie  cell-wall,  and,  contrary  to  what 
is  usually  believed,  is  entirely  independent  of  tlie  disintegration  of  the 


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Myrosin.  Mustard. 

••  Stsatolytic  . . Separation  of  fats  into  fatty  acids  and  glycerin.  Steapsin.  Pancreatic  juice 


124 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


starch-granule.  The  enzyme,  which  thus  dissolves  the  parenchymatous  cell- 
walls  of  the  endosperm,  has  received  the  name  Cytase.  Cytase  is  secreted  by 
the  embryo  during  germination,  and  is  found  in  considerable  quantity  in 
green-  or  air-dried  malt,  but  is  readily  destroyed  by  the  action  of  heat, 
and  so  is  found  in  only  very  limited  quantity  in  kiln-dried  malt,  especially 
that  which  has  been  subjected  to  a somewhat  high  temperature.  That 
cytase  is  not  identical  with  diastase  is  demonstrated  by  the  fact  that,  where- 
as a filtered  aqueous  extract  of  air-dried  malt  dissolves  the  cell- walls  of 
the  endosperm,  this  power  is  lost  on  subjecting  the  liquid  to  a tempera- 
ture of  60°  C.,  which  temperature  does  not  destroy  the  vitality  of  diastase. 

250.  Diastase. — ^Since  the  “ mashing  ” or  maceration  of  malt  with 
water  at  about  a temperature  of  60°  C.  has  been  employed  as  one  of  the 
operations  in  the  brewing  of  beer,  it  has  been  well  known  that  during  this 
process  the  starch  of  the  malt  is  converted  into  some  form  of  sugar.  Payen 
and  Persoz,  in  1833,  stated  that  the  action  of  an  infusion  of  malt  on  starch 
was  due  to  the  presence  of  a particular  transforming  agent  to  which  thej’ 
gave  the  name  of  diastase. 

, Investigation  show^s  that  diastase  is  secreted  by  the  embryo  of  such 
plants  as  wheat  and  barley  during  germination — in  a subsequent  chapter 
the  physiology  of  its  production  and  action  is  dealt  with  somewhat  fully. 
Diastase  is  present  in  large  quantity  in  air-dried  malt,  and  to  a lesser  but 
still  eonsiderable  extent  in  the  malt  after  kiln-drying. 

For  its  extraction  in  a concentrated  form,  Lintner  recommends  the 
following  method  : — 1 part  of  green  malt  or  sifted  air-dried  malt  is  ex- 
tracted with  2 to  4 parts  of  20  per  eent.  alcohol  for  24  hours.  At  the  end 
of  this  time  as  much  as  possible  of  the  liquid  is  filtered  off  by  means  of  a 
press,  then  filtered  through  paper  until  bright.  To  this  filtered  extract 
2J  times  its  volume  of  absolute  alcohol  is  added,  resulting  in  the  production 
of  a precipitate,  which  is  allowed  to  settle,  and  washed  on  a filter  with  abso- 
lute alcohol.  The  precipitate  is  then  transferred  to  a mortar  and  rubbed 
down  with  absolute  alcohol,  once  more  transferred  to  a filter  and  washed 
with  absolute  alcohol,  and  ether.  Finally  it  is  dried  in  vacuo  over  sul- 
phuric acid.  Prepared  in  this,  manner,  diastase  consists  of  a yellowish- 
white  powder  of  great  diastatic  activity.  Its  purification  is  effected  by 
repeatedly  dissolving  in  water  and  re-precipitating  by  alcohol.  Subjecting 
the  aqueous  solution  to  dialysis  reduces  the  quantity  of  ash  (which  con- 
sists of  normal  calcium  phosphate)  and  also  increases  the  percentage  of 
nitrogen.  A purified  diastase  gave  the  following  numbers  on  analysis 
calculated  on  the  ash-free  substance.  Results  of  analyses  of  other  enzymes 
are  also  given. 

Composition  of  Various  Enzymes. 


Diastase. 

Pancreatic 

Enzyme. 

Invertase. 

j 

Emulsin.  j 

1 

Carbon  . . 

46-66 

46-57 

43-90 

' i 

i 43-50 

Hydrogen 

7-35 

7-17 

8-40 

7-00 

Nitrogen  . . 

10-42 

14-95 

9-50 

11-60  1 

Sulphur  . . 

1-12 

0-95 

0-60 

1-30 

Oxygen  . . . . . . 

34-45 

30-36 

37-60 

36-60 

100-00 

100-00 

100-00 

i 

100-00 

Authority 

Lintner. 

1 

Hiifner. 

Barth.  j 

Bull. 

ENZYMES  AND  DIASTATIC  ACTION. 


125 


More  recently  Osborne  lias  prepared  diastase  from  malt  in  another 
manner.  The  ground  malt  was  first  extracted  with  water  and  filtered. 
To  the  filtrate  ammonium  sulphate  was  added  to  saturation,  and  the  pro- 
teins thus  precipitated.  The  precipitate  was  suspended  in  water  and 
subjected  to  dialysis,  thus  removing  much  of  the  ammonium  sulphate  ; 
there  remained  a residue  of  a globulin  character,  and  this  was  filtered  off. 
The  filtrate  was  again  saturated  with  ammonium  sulphate,  the  precipitate 
suspended  in  water,  once  more  dialysed,  and  filtered,  thus  getting  rid  of 
most  of  the  globulins.  The  resulting  solution  of  proteins  was  next  dialysed 
into  alcohol,  with  the  formation  of  some  precipitate.  This  was  filtered 
off,  and  the  solution  again  dialysed  into  more  alcohol,  with  the  formation 
of  a further  precipitate.  The  operations  of  dialysis  and  filtration  were 
repeated  until  altogether  five  fractions  of  precipitate  had  been  obtained. 
The  precipitates  were  purified  by  solution  in  water,  filtration,  dialysis  first 
into  water,  and  afterwards  into  alcohol,  and  finally  re-precipitated  by  the 
addition  of  absolute  alcohol  and  dried.  The  fourth  fraction  was  far  higher 
in  diastatic  power  than  any  of  the  others.  This  preparation  was  soluble 
in  water,  became  turbid  at  50°  C.,  and  gave  a large  coagulum  at  56°  C. 
The  filtrate  from  this  gave  the  biuret  reaction,  thus  showing  the  presence 
of  proteoses.  This  preparation  had  a diastatic  power  of  600°  Lintner  and 
was  the  most  active  diastatic  substance  on  record.  Analysis  showed  it 
to  contain  0*66  per  cent,  of  ash,  and  allowing  for  this  it  had  the  following 
composition  : — 


Carbon  .........  52*50 

Hydrogen  .........  6*72 

Nitrogen  .........  16*10 

Sulphur  .........  1 *90 

Oxygen  .........  22*78 


100*00 

The  composition  is  that  of  a normal  protein,  save  that  the  sulphur  is 
somewhat  high,  but  this  may  be  accounted  for  by  the  possible  presence  of  a 
little  ammonium  sulphate. 

On  further  investigation,  this  substance  was  found  to  have  the  same 
coagulating  temperature  as  leucosin  (albumin  of  wheat  or  barley),  and 
Osborne  regards  albumin  as  being  the  diastatic  body.  But  the  amount 
of  diastatic  action  is  not  proportional  to  that  of  albumin,  amd  therefore 
Osborne  suggests  the  hypothesis  that  diastase  is  a compound  of  albumin 
M'ith  possibly  proteose,  but  of  this  theory  there  is  at  present  no  direct  proof. 

During  the  passage  of  this  work  throught  the  Press,  the  Malt-Diastase 
Company  of  New  York  have  forwarded  the  authors  a sample  of  exceedingly 
concentrated  malt  diastase,  prepared  in  their  laboratory,  which  has  the 
following  remarkable  converting  power  : — 

(1)  One  part  by  weight  will  convert  150  parts  by  weight  of  starch  into 

dextrin  and  maltose,  within  ten  minutes  at  99°  F. 

(2)  One  part  will  produce  from  a surplus  of  starch,  329  parts  of  maltose 

within  thirty  minutes  at  99°  F.  ■ 

(3)  Tested  according  to  Lintner’s  method,  this  diastase  has  a strength  of 

4,705°. 

Diastase  gives  with  tincture  of  guaiacum  and  hydrogen  peroxide  a 
blue  colouration,  which  is  soluble  in  ether,  benzene,  chloroform,  and  carbon 
disulphide,  but  not  in  alcohol.  This  reaction  of  diastase  is  shared  by  other 
enzymes,  and  is  caused  by  the  presence  of  peroxydase.  This  latter  sub- 
stance may  be  regarded  as  an  enzyme  having  an  oxidising  action  as  distinct 
from  the  hydrolysing  actions  before  described. 


126 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Diastase  in  the  pure  form  does  not  reduce  Fehling’s  solution,  and,  as 
may  be  judged  from  its  very  nature,  is  marked  by  a great  capacity  for 
liquefying  starch  paste  and  saccharifying  it  into  dextrin  and  maltose. 
Unlike  the  acids,  diastase,  however,  is  incapable  of  converting  starch  fur- 
ther than  into  dextrin  and  maltose.  Diastase  readily  changes  amylo- 
dextrin  and  maltodextrin  completely  into  maltose,  but  does  not  under 
any  circumstances  further  hydrolyse  maltose. 

Under  favourable  circumstances,  one  part  of  well-prepared  diastase, 
such  as  that  of  Osborne,  is  stated  to  suffice  for  the  conversion  of  2000  parts 
of  starch.  A dilute  solution  of  diastase  is  exceedingly  unstable,  rapidly 
becoming  acid,  and  losing  its  power  of  starch  conversion.  This  does  not 
apply  to  concentrated  solutions  of  diastase  in  the  presence  of  sugars  such 
as  are  obtained  by  concentrating  in  vacuo  cold-water  extracts  of  malt  to  the 
consistency  of  a sirup. 

251.  Diastatic  Action  or  Diastasis. — The  action  of  diastase,  being  of 
of  such  great  importance  in  brewing  operations,  has  been  studied  closely. 
The  term  “ diastase  is  occasionally  used  in  a generic  sense,  and  is  then 
applied  to  the  hydrolysing  agents  of  the  cereals  generally  ; thus  cerealin 
is  at  times  referred  to  as  the  “ diastase of  bran.  Hydrolysis,  when  effected 
by  diastase  or  its  congeners,  is  often  termed  diastatic  action,  for  which  the  shorter 
term  “ diastasis  ” is  sometimes  used. 

252.  Measurement  of  Diastatic  Capacity. — ^The  activity  of  malt  extract, 
or  of  the  purer  forms  of  diastase,  depends  on  the  degree  of  concentration, 
temperature,  and  other  conditions.  Kjeldahl  has  enunciated  what  is 
known  as  the  law  of  proportionality.  The  amount  of  diastase  in  two 
malt  extracts  is  proportional  to  the  reducing  power  which  they  effect, 
providing  that  both  act  on  the  same  quantity  of  starch  during  the  same 
period  of  time,  and  that  the  cupric  oxide  reducing  power  (K)  does  not 
surpass  25-30.  If  the  whole  of  the  starch  present  were  converted  into 
maltose,  K would  be  62*5  ; according  to  this  stipulation,  therefore,  some- 
what less  than  half  the  starch  must  undergo  conversion  into  maltose,  or, 
in  other  words,  starch  must  be  to  that  extent  in  excess  of  the  amount  hydro- 
lysed by  the  diastase.  Unless  the  starch  is  thus  largely  in  excess,  the 
diastatic  action  will  not  be  proportional  to  the  amount  of  diastase. 

Lintner  measures  the  diastatic  capacity  on  soluble  starch,  prepared  as 
directed  in  Chapter  VI.,  paragraph  172,  and  terms  the  diastatic  activity 
of  the  precipitated  diastases  as  100,  when  3 c.c.  of  a solution  of  0*1  gram 
of  diastase  in  250  c.c.  of  water,  added  to  10  c.c.  of  a 2 per  cent,  starch  solution, 
produces  in  one  hour,  at  the  ordinary  temperature,  sufficient  sugar  to 
reduce  5 c.c.  of  Fehling’s  solution.  These  quantities  amount  to  0*0012 
gram  of  diastase,  acting  on  0*2  gram  of  soluble  starch,  while  the  maltose 
necessary  to  reduce  5 c.c.  of  Fehling’s  solution  is  0*0400  grams.  This 
quantity  of  maltose  produced  is  approximately  equal  to  0*05  grams  of 
starch  reduced,  and  the  diastase  will  have  hydrolysed  about  41  times  its 
weight  of  starch  in  the  time  and  under  the  conditions  specified.  Direc- 
tions for  the  determination  of  diastase  by  methods  based  on  this  principle 
are  given  in  the  analytic  section  of  this  work.  The  above  is  simply  a mode 
of  determining  diastatic  activity,  everything  else  being  equal.  The  con- 
sideration of  how  diastatic  capacity  is  affected  by  changes  of  temperature 
and  Qtlier  conditions  is  described  in  detail  in  subsequent  paragraphs. 

253.  Nature  of  Diastase. — The  effects  of  diastase  on  starch  have  already 
been  spoken  of  as  including  two  distinct  actions  ; first,  the  liquefying  of 
starch  paste,  converting  it,  in  fact,  into  soluble  starch  ; and  second,  the 
saccharifying  of  tliis  previously  liquefied  starch.  Certain  forms  of  diastase 


ENZYMES  AND  DIASTATIC  ACTION. 


127 


possess  this  latter  power  only  ; but  it  is  usually  assumed  that  malt  diastase 
possesses  the  two  properties.  More  recently,  the  opinion  has  been  growing 
that  malt  diastase  consists  of  two  distinct  enzymes — the  one  a liquefying, 
and  the  other  a saccharifying  agent.  More  will  be  said  on  this  matter 
when  dealing  with  the  diastase  of  unmalted  grain. 

There  naturally  arises,  in  conjunction  with  the  study  of  diastase,  the 
speculation  whether  diastase  is  a distinct  chemical  compound  of  nature 
allied  to  the  proteins,  or  a property  or  function  certain  protein  bodies 
are  capable  of  exercising  under  special  conditions.  Certainly,  in  the  purest 
form  hitherto  isolated^,  diastase  is  obtained  by  processes  which  secure 
soluble  proteins  in  the  purest  state  ; and,  practically,  any  substance  called 
diastase  is  unobtainable  as  distinct  and  separate  from  soluble  proteins. 

Brown  and  Heron  finding  that,  on  heating  malt  extract  to  a temperature 
of  about  46°  C.,  the  soluble  proteins  commence  to  coagulate  ; a continu- 
ance of  this  temperature  for  some  15  to  20  minutes  effects  the  maximum 
amount  of  coagulation  possible  at  46°  C.  On  raising  the  temperature  a 
few  degrees,  an  additional  quantity  of  proteins  coagulate  ; this  further 
increase  of  coagulation  continues,  as  the  temperature  rises,  up  to  about 
95°  C.  The  proteins  of  malt  extract  may  be  viewed  as  being  composed 
of  distinct  fractions,  each  of  which  has  a definite  coagulating  point,  varying 
from  46°  to  95°  C.  With  the  coagulation  of  the  proteins,  the  diastatic 
power  of  the  malt  extract  diminishes  ; also,  no  diminution  of  starch  con- 
verting power  has  been  observed  without  a coagulation  of  proteins.  Fur- 
ther, at  the  point  at  which  the  diastatic  power  of  malt  extract  is  destroyed 
(80-81°  C.),  nearly  the  whole  of  the  coagulable  proteins  have  been  pre- 
cipitated. Brown  and  Heron  “ are  consequently  led  to  conclude  that 
the  diastatic  power  is  a function  of  the  coagulable  proteins  themselves,  and  is  not 
due,  as  has  been  generally  supposed,  to  the  presence  of  a distinctive  transforming 
agent/"  They  further  find  that  filtration  through  a porcelain  diaphragm 
results  in  the  production  of  a liquid  which,  on  being  heated  to  the  boiling 
point,  throws  down  no  proteins.  This  filtered  malt  extract  they  find  to 
be  incompetent  to  produce  diastasis,  possessing  “ absolutely  no  transforming 
power.""  It  is  therefore  possible  to  remove  the  diastatic  agent  from  the 
malt  extract  without  the  application  of  heat. 

254.  Action  of  Diastase  on  Starch. — This  reaction  may  first  be  summed 
up  briefiy  by  stating  that  if  a cold  infusion  of  malt  be  made,  and  then  fil- 
tered ; it,  the  infusion,  on  being  added  to  a solution  of  starch  in  water, 
at  temperatures  from  15°  to  about  70°  C.,  more  or  less  rapidly  hydrolyses 
the  starch  into  a mixture  of  dextrin  and  maltose.  The  longer  the  operation 
is  continued,  the  higher  is  the  proportion  of  maltose  produced  ; but  even 
prolonged  action  does  not  result  in  any  further  hydrolysis  of  the  maltose 
into  glucose.  The  investigation  of  starch  and  its  transformation  products 
has  for  many  years  occupied  the  close  attention  of  what  may  be  called 
the  Burton  School  of  Chemists.  Prominent  among  these  are  the  names 
of  0"Sullivan,  Brown,  Heron,  and  Morris.  By  these  and  other  writers,  a 
number  of  papers  of  singular  interest  and  value  have  been  contributed  to 
the  Journal  of  the  Chemical  Society.  The  following  paragraphs  (255-261) 
consist  largely  of  a summary  of  the  conclusions  arrived  at  and  adduced 
in  these  papers,  after  careful  collation  with  each  other,  and  the  work  of 
other  investigators. 

Brown,  Heron,  and  Morris’  Researches. 

255.  Malt  Extract  employed. — It  was  found  that  a cold  aqueous  infusion 
of  malt  was  he  most  convenient  diastatic  agent  to  employ,  as  diastase 
when  employed  in  a pure  state  was  liable  to  considerable  variations  in 


128 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


activity.  With  proper  precautions,  the  aqueous  infusion  of  malt  admitted' 
of  any  degree  of  accuracy.  The  infusion  or  malt  extract  was  prepared  by 
mixing  100  grams  of  finely  ground  pale  malt  with  250  c.c.  of  distilled  water. 
This  mixture  was  well  stirred  and  then  allowed  to  stand  for  from  six  to 
twelve  hours,  and  then  filtered  bright.  This  extract  had  a specific  gravity 
of  1036-1040. 

256.  Action  of  Malt  Extract  on  Cane  Sugar. — ^Malt  extract  is  capable 
of  “ inverting  ""  cane  sugar,  i.e.,  changing  it  into  glucose.  The  term  “ in- 
verting ” is  derived  from  the  fact  that  the  resulting  mixture  of  glucoses 
exerts  a left  handed  rotary  action  on  polarised  light,  while  the  original 
sugar  is  dextro-rotary.  The  maximum  effect  is  produced  at  about  55°  C.  ; 
it  is  much  weaker  at  60°,  almost  destroyed  at  66°,  and  entirely  destroyed 
by  boiling. 

257.  Action  of  Malt  Extract  on  Ungelatinised  Starch. — ^According  to 
Brown  and  Heron’s  earlier  researches,  malt  extract  is  incapable  of  acting 
on  unaltered  starch  ; and  even  when  contact  between  the  two  is  main- 
tained for  a considerable  time,  not  the  slightest  action  is  perceptible  at 
ordinary  temperatures. 

Notwithstanding  this,  it  is  well  known  that  the  starch  of  seeds  is  attacked 
and  dissolved  during  the  natural  act  of  germination  ; but  this  action  they 
viewed  as  being  inseparable  from  the  living  functions  of  the  vegetable  cell. 

This  statement  is  at  variance  with  that  of  Baranetzky,  who  avers  that 
“ the  starch  granules  of  different  kinds  are  acted  on  with  unequal  rapidity 
by  the  diastatic  ferments  of  plant  juices,  the  strongest  ferment  of  all,  malt 
diastase,  being  w^ell  known  to  have  no  perceptible  influence,  even  after 
long  exposure,  on  solid  potato-starch  granules,  while  wheat  and  buck- 
wheat are  dissolved  with  facility.” 

In  a more  recent  paper  on  “ Germination  of  some  of  the  Graminese,” 
1890,  Brown  and  Morris  refer  to  Brown  and  Heron’s  paper  of  1879,  and 
the  conclusion  therein  expressed  is  that  ungelatinised  starch  is  not  acted 
on  by  malt  extract,  no  “ pitting  ” of  the  granule  or  disintegration  being 
produced  by  artificial  means.  .They  also  refer  to  Baranetzky ’s  memoir, 
and  confirm  his  statement  that  solid  potato-starch  granules  (which  had 
been  exclusively  used  by  O’Sullivan  and  themselves  in  their  previous 
researches)  are  highly  resistant  to  diastase.  They  further  find  that 
well-washed  and  highly  purified  barley-starch  is  in  a few  days  “ pitted,” 
disintegrated,  and  dissolved  by  a cold-water  extract  of  air-dried  malt,  the 
action  being  facilitated,  as  shown  by  Baranetzky,  by  the  presence  of  a 
minute  quantity  of  acid.  They  treated  some  well-purified  ungelatinised 
5rtr^ey-starch  with  a solution  of  precipitated  malt  diastase,  to  which  0 0065 
per  cent,  of  formic  acid  had  been  added.  (Acid  of  this  degree  of  concen- 
tration has  no  action  on  barley-starch.)  A trace  of  chloroform  had  also  been 
employed  in  order  to  prevent  putrefactive  changes.  The  starch  was  vigor- 
ously attacked,  with  the  production  of  maltose  as  the  only  optically  active 
substance  produced. 

At  higher  temperatures,  diastase  or  malt  extract  acts  on  ungelatinised 
starcli  ; thus  Lovibond  (“  Brewing  with  Raw  Grain  ”)  states  that  the 
diffusive  action  of  the  diastase  through  the  starch  cell-wall  is  sufficient 
at  liigli  temperatures,  to  effect  the  hydrolysis  of  the  starch  granulose. 
The  temperatures  at  which  he  worked  were,  however,  not  much  below 
those  given  for  incipient  gelatinisation.  The  authors  also  find  that  on 
mashing  wheat  flour  witli  malt  extract  for  some  time  at  temperatures- 
below  the  gelatinising  point,  considerable  quantities  of  starch  suffer  hydro- 
lysis. 

Lintner  gives  the  following  table  of  the  quantities  of  ungelatinised 


ENZYMES  AND  DIASTATIC  ACTION. 


129 


starch  dissolved  by  treatment  with  malt  extract  at  various  temperatures. 
The  digestion  was  allowed  to  proceed  for  four  liours,  but  in  the  case  of 
the  higher  temperatures  was  practically  complete  in  about  twenty  minutes. 
Tlie  results  are  given  in  percentages  of  the  total  starch  taken  for  the  experi- 
ments : — 

Action  of  Malt  Extract  on  Ungelatinised  Starch. 


50°  C. 

55°C. 

60°  C. 



65°  C. 

Potato  Starch  . . 

Per  Cent. 

013 

Per  Cent. 

5-03 

I Per  Cent. 

52-68 

Per  Cent. 

90-34 

Rice  ,, 

6-58 

9-68 

19-68 

31-14 

Wheat  ,, 

— 

62-23 

91-08 

94-58 

Maize  ,, 

2-70 

— 

18-50 

54-60 

Rye 

25-20 

• — ■ 

39-70 

94-50 

Oat  ,, 

9-40 

48-50 

92-50 

93-40 

Barley 

12-13 

53-30 

92-81 

96-24 

Green  Malt  Starch 

29-70 

58-56 

92-13 

96-26 

Kilned  ,, 

13-07 

56-02 

91-70 

93-62 

258.  Action  of  Malt  Extract  on  Bruised  Starch. — As  the  next  step  in 
the  investigation,  some  starch  was  triturated  in  a mortar  with  powdered 
glass.  This  treatment  results  in  cutting  the  cellulose  envelopes  of  the 
granules.  The  starch  granulose  is  then  exposed,  and  on  being  treated 
with  malt  extract  rapidly  undergoes  conversion.  The  product  consists 
principally  of  maltose,  the  actual  results  obtained  in  one  experiment  being 
that,  after  remaining  six  hours,  the  clear  solution  contained — 

Maitose  . . . . . . . . . 86*3  , 

Dextrin  . . . . . . . . .10*5 

Cellulose  . . . . . . . . . 3 *2 


100-0 

After  twenty-four  hours  in  the  cold  the  maltose  had  suffered  a slight 
increase  : — 

Maltose  . . . . . . . .91*4 

Dextrin  . . . . . . . . . 70 

Cellulose  . . . . . . . . . 1 *6 


100-0 

It  will  be  noticed  that  under  these  circumstances  a ^mall  quantity  of 
cellulose  becomes  dissolved. 

259.  Action  of  Malt  Extract  upon  Starch  Paste  in  the  Cold. — At  ordinary 
temperatures  malt  extract  acts  upon  starch  paste  (gelatinised  starch)  with 
great  rapidity  and  energy.  In  100  c.c.  of  starch  solution,  containing  be- 
tween 3 and  4 per  cent,  of  solid  matter,  the  addition  of  from  5 to  10  c.c. 
of  the  malt  extract  causes  the  starch  to  become  perfectly  limpid  in  from 
one  to  three  minutes.  Immediately  after  arriving  at  this  point  the  solution 
ceases  to  give  a blue  colouration  with  iodine.  Amyloins  are  shown  to  be 
present  by  the  brown  reaction  with  iodine,  and  do  not  disappear  within 
some  five  or  six  minutes  from  the  commencement  of  the  experiment.  In 
this  case  also  a small  quantity  of  starch  cellulose  is  dissolved,  but  is  slowly 

K 


130 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


re-deposited  on  the  liquid  standing.  After  remaining  three  hours,  three 
experiments  gave  a mean  of — 

Maltose  . . . . . . . . . 80  *4 

Dextrin  .........  19*6 


100-0 

as  the  composition  of  the  solution,  resulting  from  hydrolysis  by  malt  extract. 

260.  Action  of  Malt  Extract  at  higher  temperatures. — ^At  temperatures 
of  40°  and  50°  C.,  the  ultimate  products  of  the  action  of  malt  extract  are 
found  to  be  practically  the  same  as  in  the  cold,  but  the  point  of  dis- 
appearance of  amyloins  is  reached  somewhat  less  rapidly.  At  60°  C.  the 
action  is  weakened,  but  still  proceeds  sufficiently  far  to  produce  practi- 
cally the  same  amount  of  maltose.  At  still  higher  temperatures  the 
transformation  of  the  dextrin,  first  formed,  into  maltose  goes  on  much 
more  slowly.  Also,  the  action  of  the  diastase  of  the  malt  extract  may 
be  weakened  by  the  addition  to  it  of  dilute  alkalies.  Such  treatment 
results  in  limiting  the  extent  to  which  the  conversion  of  dextrin  into  maltose 
proceeds.  The  results  may  be  summed  up  by  stating  that,  by  modifications 
of  the  treatment  of  starch  paste  with  malt  extract,  certain  fixed  points 
may  be  obtained  representing  several  different  molecular  transformations 
of  starch. 


261.  Molecular  Constitution  of  Starch,  Dextrin,  anl  Maltose. — ^The 
historical  development  of  the  modernly  held  hypothesis  of  the  molecular 
constitution  of  starch  is,  in  view  of  the  importance  of  the  subject,  of  con- 
siderable interest.  Brown  and  Heron,  in  their  paper  on  “ Starch  and  its 
Transformations,''  1879,  considered  that  the  most  natural  conclusion  that 
can  be  derived  from  the  varying  proportions  of  dextrin,  obtained  in  modi- 
fications of  the  hydrolysis  of  starch  paste  by  malt  extract,  is  that  there 
are  several  dextrins,  and  that  these  dextrins  are  polymeric,  and  not  meta- 
meric  bodies.  Having  adopted  this  view.  Brown  and  Heron's  results  led 
them  to  the  opinion  that  the  simplest  molecular  formula  for  soluble  starch 
is  IOC12H20O10,  which  may  also  be  written  Ci2xioH20xioGioxio*  The 
first  change  produced  by  the  addition  of  malt  extract  would,  then,  be 
represented  by — 


C 12  X 10H20  X loG  10  X 10 
Soluble  Starch. 


II2O  — C12  X9H20  xoOiO  x9 

Water.  Erythro-dextrin.  a. 


C12H22O  11. 
Maltose. 


That  is,  one  of  the  groups  of  Ci2H2oOio  having  combined  with  water  to 
form  maltose,  the  remaining  nine  groups  constitute  the  first  or  most  com- 
plex dextrin.  By  the  assimilation  of  another  molecule  of  water,  the  nine- 
group  dextrin  breaks  up  into  a second  molecule  of  maltose  and  an  eight- 
group  dextrin.  This  reaction  proceeds  through  successive  stages  until 
finally  the  one-group  dextrin,  Ci2H2oOio,  is  in  its  turn  transformed  into 
maltose.  There  are  thus  theoretically  possible  nine  polymeric  modifica- 
tions of  dextrin  ; the  two  higher  of  these  are  erythro-dextrins  ; the  remaining 
seven  are  achroo-dextrins.  The  most  stable  of  the  whole  of  these  dex- 
trins is  that  resulting  from  the  eighth  transformation,  having  the  compo- 
sition C12X2H20X2O10X2  • the  hydrolysis  of  starch,  with  the  production 
of  tliis  dextrin,  would  then  be  represented  by — 


Gi2x  I0H2OX  loGiOx  10  8H2O  — Ci2x  12H2OX2O1OX2  8Ci2H220ii. 
Soluble  Starch.  Achroo-dextrin.  ^ Maltose. 

In  the  more  recent  paper  by  Brown  and  Morris  (“  The  Non-cry stallisablc 
Products  of  the  Action  of  Diastase  upon  Starch,"  1885),  they  adduce 
evidence  in  favour  of  a third  body,  maltodextrin,  being  formed  as  an 


ENZYMES  AND  DIASTATIC  ACTION.  131 

intermediate  product  during  the  hydrolysis  of  starch  ; as  previously 

mentioned,  they  ascribe  to  this  body  the  formula,  - C12H20OJ0.  From 

(C12H20O10 

this  it  will  be  seen  that  maltodextrin  is  composed  of  a molecule  of  mal- 
tose united  with  two  of  the  one-group  dextrin.  Viewed  in  the  light  of 
the  existence  of  this  intermediate  product,  they  then  regarded  the  fol- 
lowing as  the  simplest  molecular  formula  for  starch,  capable  of  accounting 
for  the  various  reactions  observed  during  its  hydrolysis — 

/(C12H20O  10)3 
I (Ci2H2oOio)3 
■j  (C12H20O  10)3 

I (C12H20O  10)3 

(Ci2H2oOio)3 

In  accordance  with  this  hypothesis,  the  first  step  in  hydrolysis  consists 
in  the  lesion  of  one  of  the  ternary  groups,  which  is  transformed  into  malto- 
dextrin by  the  assimilation  of  a molecule  of  water,  thus — 

(C.H.„0.),  + H.0  = {fc'Sfo”). 

One  of  the  five  ternary  groups  Water.  Maltodextrin. 

constituting  the  starch  molecule. 

Malt  extract  effects  the  complete  conversion  of  maltodextrin  into 
maltose — 

fCi2ll2  20ii  I qtt  r\  TT 

1 /r<  TT  rk  \ > ^Xl2V^  — 'J'- 12^^22'-' n» 

''  ^'-^12-0-20'-'  10/2 

Maltodextrin.  Water.  Maltose. 

In  the  change  producing  maltodextrin,  the  remaining  four  ternary 
groups  of  (Ci2H2oOio)3  unite  to  form  the  most  complex  of  the  dextrins. 
As  the  hydrolysis  continues,  the  remaining  ternary  groups  undergo  suc- 
cessively the  same  change  until  one  only  remains  : this  is  identical  with 

that  before  referred  to  as  achroo-dextrin  The  view  that  the  starch  mole- 

cule contains  fifteen  of  the  C12II20O10  group  instead  of  ten,  requires  that 
this,  which  may  be  distinguished  as  “ stable  dextrin,""  shall  consist  of  three 
groups  of  C12II20O10  instead  of  two  : this,  of  course,  makes  the  formula 
the  same  as  that  of  one  of  the  ternary  groups.  The  reaction  for  the  pro- 
duction of  stable  dextrin  is  then  represented  by  the  following  equation  : — - 

'(C12II200 10)3 

(C12II200 10)3  (C12II20O10 

-^(Ci2H2oOio)3  + I2H2O  = Ci2H2oOm  + 12Ch2H220„. 

(Ci2ll2oOio)3  IC12II20O10 

,(^12^200  10)3 

Soluble  starch.  Water.  Stable  Dextrin.  Maltose. 

Such,  very  briefly  summarised,  were  the  opinions  advanced  by  Brown, 
Heron,  and  Morris,  up  to  1885,  as  to  the  relative  molecular  constitutions 
of  starch,  dextrin  and  maltose. 

In  1888  and  1889,  Brown  and  Morris  contributed  to  the  Chemical 
Society's  J our  nal  t\Yo  m.o^t  important  papers  on  “ The  Molecular  Weights 
of  the  Carbohydrates.”  To  these  papers  reference  has  already  been  made 
in  the  commencement  of  Chapter  VI.  By  the  application  of  Raoult"s 
method,  the  molecular  weights  of  starch  and  the  products  of  its  hydro- 
lysis were  definitely  determined.  Among  these  determinations,  probably 
the  most  important  was  that  of  dextrin.  This  was  made  as  a preliminary 
to  the  estimation  of  that  of  soluble  starch.  It  has  been  already  shown 
that  these  chemists  view  starch  as  a compound  of  five  dextrin  groups. 
In  their  1889  paper  they  say  : — 


132 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


‘‘  When  the  complex  molecule  of  starch  is  broken  down  by  diastase, 
under  the  conditions  most  favourable  to  its  complete  hydrolysis,  we  have 
shown  that  a point  of  equilibrium,  or,  speaking  more  strictly,  a resting 
point  in  the  reaction  is  reached,  when  the  amount  of  dextrin  produced 
corresponds  to  one-fifth  by  weight  of  the  amount  of  starch  taken  ; that  is, 
when  the  mixed  products  have  [a]  j 2-sq=  162*6°  and  K3.86  = 49*3. 

“ This  reaction  is  represented  in  the  simplest  form  by 

5C12H20O10  “h  4H2O  = C12H20O10  4Ci2H  220ii. 
starch.  Water.  Dextrin.  Maltose. 

If  the  production  of  maltose  and  dextrin  during  hydrolysis  is  to  be 
considered  as  due  to  a molecular  degradation  of  the  starch,  and  we  think 
the  evidence  in  favour  of  this  is  almost  conclusive  ; then,  no  matter  what 
view  we  may  take  of  the  actual  manner  in  which  this  degradation  takes 
place,  we  cannot  escape  from  the  conclusion  that  the  molecule  of  stable  dex- 
trin of  the  above  equation  is  one- fifth  of  the  size  of  the  soluble  starch  molecule 
from  which  it  has  been  derived” 

Brown  and  Heron  determined  by  RaoulFs  method  the  molecular  weight 
of  this  dextrin,  and  thus  indirectly  that  of  starch.  In  the  next  place  they 
proceeded  to  consider  whether  Raoult’s  method  was  capable  of  throwing 
any  light  on  the  relations  of  the  dextrins  to  each  other,  it  being  a matter 
of  the  highest  theoretical  importance  to  determine  whether  these  bodies 
constitute  a series  of  polymers,  or  whether  they  stand  merely  in  metameric 
relation  to  each  other.  Accordingly  some  of  the  so-called  higher  dextrins 
were  prepared  ; that  is,  those  which  result  from  starch  hydrolysis  arrested 
at  its  earlier  stages.  A comparison  of  the  results  thus  obtained  afforded 
no  evidence  of  there  being  any  difference  in  the  molecular  weights  of  the 
higher  and  lower  dextrins.  Brown  and  Morris  summarise  their  conclusions 
by  saying  that  there  being  no  differences  in  the  various  dextrins  when 
treated  by  Raoult’s  method,  “ goes,  in  our  opinion,  a long  way  towards 
proving  that,'  after  all  the  dextrins  are  metameric,  and  not  polymeric. 
If  this  is  admitted  as  even  probably  correct,  it  becomes  necessary  to  consider 
how  far  our  previous  views  on  the  breaking-down  of  the  starch  molecule 
must  be  modified  in  order  to  include  the  new  facts.”  Brown  and  Morris 
enunciate  the  following  hypothesis  as  being  more  in  accord  with  the  facts  : — 

“ We  may  picture  the  starch-molecule  as  consisting  of  four  complex 
amylin-groups  arranged  round  a fifth  similar  group,  constituting  a molecular' 
nucleus. 

“ The  first  action  of  hydrolysis  by  diastase  is  to  break  up  this  complex 
molecule,  and  to  liberate  all  the  five  amylin-groups.  Four  of  these  groups 
when  liberated  are  capable,  by  successive  hydrolysations  through  malto- 
dextrins,  of  being  rapidly  and  completely  converted  into  maltose,  whilst 
the  central  amylin  nucleus,  by  a closing  up  of  the  molecule,  withstands 
the  influence  of  hydrolysing  agents,  and  constitutes  the  stable  dextrin 
of  the  low  equation,  which,  as  we  know,  is  so  slowly  acted  upon  by  subsequent 
treatment  with  diastase.  The  four  readily  hydrolysable  amylin-groups 
we  look  upon  as  of  equal  value,  and  in  their  original  state  these  constitute 
the  so-called  high  dextrins,  which  can  never  be  separated  completely  from 
the  low  dextrin  by  any  ordinary  means  of  fractionation. 

‘‘  This  hypothesis  provides  for  intermediate  maltodextrins  or  amylo- 
dextrins,  whose  number  is  only  limited  by  the  size  of  the  original  amylin- 
grou}).^ 

Each  amylin-group  of  the  five  has  a formula  of  (Ci2H2oOio)2o>  a-nd 
a molecular  weight  of  64S0  ; so  that  the  entire  starch-molecule,  or,  more 
correctly  speaking,  that  of  soluble  starch,  is  represented  by  5(Ci2H2oOjo)-:u> 
having  a molecular  weight  of  32,400.” 


ENZYMES  AND  DIASTATIC  ACTION. 


133 


In  their  Text  Book  of  the  Science  of  Brewing,  publislied  in  1891,  Moritz 
and  Morris  further  explain  that  probably  the  outer  amylin-groups  cannot 
■exist  as  such,  but  immediately  on  separation  from  the  central  nucleus  are 
partially  hydrotysed,  yielding  amyloins  of  possibly  the  very  highest  type. 
These  amyloins  are  gradually  hydrolysed,  being  split  up  into  smaller  aggrega- 
tions, which  constitute  the  various  maltodextrins. 

Brown  and  Millar,  in  a paper  contributed  to  the  Journal  of  the  Chemical 
Society  in  1899,  point  out  that  the  so-called  stable  dextrin  has  a cupric 
reducing  power  of  B 5 *7-5  *9,  and  therefore  must  contain  a glucose  group. 
According  to  this  view,  the  hydrolysis  of  starch  is  thus  represented  : — 

lOOC.^H^oO.o  + 8IH2O  = 8OC.2H22O:. 

(t  61112^6 

Starch.  Water.  Maltose.  Stable  Dextrin. 

262.  Effect  of  Heat  on  Diastasis. — The  rapidity  of  diastatic  action  is 
■considerably  influenced  by  variations  of  temperature  ; extreme  cold  practi- 
cally inhibits  it.  Starting  from  ordinary  temperatures,  diastasis  rapidly 
increases  as  the  temperature  rises,  until,  according  to  Kjeldahl,  54°  C. 
(129°  E.)  is  reached — from  that  temperature  until  63°  C.  (145°  E.)  it  remains 
fairly  constant,  and  then  rapidly  decreases  with  any  further  rise  in  tempera- 
ture, being  entirely  destroyed  at  10-81°  C.  (176-177*8°  E.).  Lintner, 
working  with  soluble  starch,  places  the  optimum  temperature  at  50-55°  C. 
(122-131°  E.). 

Lintner  carefully  investigated  the  effect  of  heat  on  diastase  itself  by 
dissolving  similar  quantities  of  diastase  in  water,  and  then  heating  the 
various  solutions  to  55°  C.  (131°  E.)  for  varying  periods  of  time,  and  then 
determining  the  quantity  of  each  solution  requisite  to  convert  the  same 
amount  of  starch.  He  obtained  the  following  results  : — 

Of  the  untreated  solution  0*55  c.c.  was  required. 

After  heating  20  minutes  at  55°  C.,  1*10  c.c.  of  solution  was  requisite. 

„ 40  ,,  „ 1*75  c.c.  „ ,, 

,,  60  ,,  ,,  2*22  c.c.  ,,  were  ,, 

By  prolonged  subjection  to  this  temperature  the  diastase  Avas  much 
Aveakened  ; but,  AAfliere  starch  and  its  transformation  products  are  present, 
the  diastase  does  not  suffer  to  a like  extent  on  subjection  to  this  temperature, 
the  strength  being  reduced  by  about  only  half  the  amount  when  heated 
in  Avater  alone.  These  results  should  be  compared  Avith  those  of  BroAvn 
and  Heron,  quoted  in  paragraph  253,  on  Nature  of  Diastase. 

233.  Effect  of  Time  anl  ConcenLation  on  Diastasis. — Other  conditions 
being  the  same,  the  time  occupied  in  producing  a given  amount  of  reaction 
depends  on  the  quantity  of  diastase  present.  Concentration  AAuthin  AAude 
limits  has  little  effect  on  the  rapidity  of  diastatic  action  ; Kjeldahl  states 
that  equal  quantities  of  diastase,  acting  at  the  same  temperature  and  for 
the  same  period  of  time,  effect  the  same  amount  of  conversion  in  solutions 
differing  Avidely  in  degree  of  concentration. 

234.  0th 3r  Con  litions  Favourable  anl  Inimical  to  Diastasis. — Kjeldahl 
states  that  A^ery  minute  quantities  of  sulphuric,  hydrochloric,  and  organic 
acids  accelerate  diastasis,  but  large  quantities  retard  it.  Lintner  states 
that  sulphuric  acid,  to  the  extent  of  0*002  per  cent.,  very  slightly  increases 
the  activity  of  diastase  ; that  0*01  per  cent,  retards  it,  and  0*10  per  cent, 
•exercises  a destructive  action.  He  also  finds  that  0*001  per  cent,  of  ammonia 
retards  diastasis,  0*005  per  cent,  almost,  and  0*2  per  cent,  entirely  stops 
the  reaction.  The  influence,  not  only  of  these,  but,  of  course,  other  sub- 
stances, depends  on  their  degree  of  concentration.  Speaking  generally, 
acetic  and  hydrocyanic  acids,  strychnine,  quinine,  and  the  salts  of  these 


134 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


bases,  very  slightly  retard  the  action  of  diastase.  Alkaline  carbonates, 
dilute  caustic  alkalies,  ammonia,  arsenious  acid,  and  magnesia,  exercise 
a somewhat  greater  retarding  influence,  depending  on  the  amount  of  these 
bodies  added.  The  following  bodies  completely  prevent  the  action  of 
diastase  upon  starch — nitric,  sulphuric,  phosphoric,  hydrochloric,  oxalic, 
tartaric,  citric,  and  salicylic  acids  ; caustic  potash,  soda,  and  lime  ; copper 
sulphate  and  acetate  ; mercury  chloride,  silver  nitrate,  iron  persulphate, 
alum,  and  borax.  Among  antiseptics,  formic  aldehyde  acts  energetically, 
on  many  of  the  enzymes.  On  the  other  hand — alcohol,  ether,  chloroform, 
thymol,  creosote,  essence  of  turpentine,  cloves,  lemon,  mustard,  etc.,  exert 
no  retarding  influence. 

In  cases  where  it  is  desired  to  suddenly  arrest  the  action  of  diastase  in 
chemical  changes,  salicylic  acid  forms  a convenient  agent.  In  100  c.c. 
of  solution,  0*040  gram  of  salicylic  acid  almost  destroys  the  activity  of 
the  diastase  in  5 c.c.  of  40  per  cent,  malt  extract  solution,  while  0*050 
gram  completely  arrests  all  action.  In  any  material  containing  diastase 
and  starch,  treatment  with  hoiling  80  per  cent,  alcohol  completely  paralyses 
any  subsequent  action  of  the  diastase  without  gelatinising  the  starch. 

Where  it  is  wished  to  prevent  fermentation  or  putrefaction  without 
retarding  diastasis,  the  addition  of  small  quantities  of  chloroform  or  thymol 
produces  the  desired  effect.  Chloroform  is  conveniently  used  in  the  form 
of  chloroform  Ab  ater,  containing  5 c.c.  of  chloroform  to  the  litre.  Toluene 
may  also  be  employed  for  the  same  purpose,  and  is  very  slightly  if  at  all 
harmful  to  enzymes. 

265.  Ptyalin  and  Amylopsin. — Ptyalin  is  found  in  human  saliva,  and 
at  an  optimum  temperature  of  35°  C.  converts  starch  paste  into  dextrin 
and  maltose  ; the  reaction  being  identical  with  that  produced  by  diastase. 
Ptyalin  acts  best  in  a neutral  medium,  but  is  but  little  affected  by  small 
amounts  of  alkali  ; a very  small  quantity  of  acid,  however,  arrests  its 
activity,  consequently  the  diastatic  action  of  ptyalin  is  destroyed  on  the 
mixture  of  food  and  saliva  encountering  the  acid  gastric  juice  of  the  stomach. 
Ptyalin  is  without  effect  on  cellulose,  and  hence  intact  starch  granules 
are  not  digested  by  its  action. 

Amylopsin  is  an  enzyme,  very  similar  to  ptyalin,  found  in  the  pan- 
creatic juice,  where  it  performs  important  digestive  functions  on  starchy 
foods. 

266.  Raw  Grain  Diastases. — Earlier  observers  have  pointed  out  that 
barley  contains  more  coagulable  proteins  than  does  malt,  yet  fresh  barley 
extract  exerts  but  little  diastatic  action.  Experiments,  on  which  these  obser- 
vations were  based,  Avere  made  aa  itli  starch-paste,  but  more  recent  investiga- 
tions in  Avhicli  soluble  starch  Avas  employed  shoAV  that  in  some  cases  raAv 
barley  in  more  actively  diastatic  than  is  the  green  malt  prepared  from  it. 
Both  from  barley  and  Avheat  a diastase  may  be  obtained  by  the  same  methods 
as  employed  for  its  extraction  from  malt,  that  is,  by  treatment  witli  £0 
per  cent,  alcohol,  subsequent  precipitation  of  the  filtered  alcoholic  extract 
with  absolute  alcoliol,  and  drying  in  vacuo  over  sulphuric  acid.  Lintner 
and  Eckhardt  have  examined  this  enzyme  in  order  to  determine  whether 
or  not  it  is  identical  A\'ith  malt  diastase.  For  this  purpose  they  took  quantities 
of  malt  and  barley  extracts  respectively,  having  the  same  diastatic  value 
as  determined  by  Lintner ’s  method,  and  subjected  soluble  starch  to  their 
action  at  varying  temperatures.  They  found  that  malt  diastase  had  the 
greatest  activity  at  50°  C.,  and  the  most  favourable  period  at  60-55°. 
RaAV  grain  diastase,  on  the  other  hand,  shoAved  the  greatest  activity  at  50,. 
and  the  most  favourable  jjeriod  at  45-50°.  At  4°  the  raAv  grain  diastase: 


ENZYMES  AND  DIASTATIC  ACTION. 


135 


had  as  high  a reducing  power  as  was  possessed  by  that  of  malt  at  14-5°. 
The  conclusion  is  that  the  two  forms  of  diastase  are  distinct  from  each  other. 

A more  marked  and  important  distinction  between  these  two  enzymes 
is  the  inability  of  that  from  raw  grain  to  effect  liquefaction  of  starch-paste, 
while  if  by  some  other  means  such  liquefaction  is  effected,  raw  grain  diastase 
energetically  converts  the  soluble-starch  into  dextrin  and  maltose.  Brown 
and  Morris  notice  that  the  power  to  liquefy  starch-paste  and  to  erode  the 
starch-granule  go  hand  in  hand  : the  observed  presence  or  absence  of 
either  property  affords  safe  ground  for  predicting  the  presence  or  absence 
of  the  other  of  the  two.  But  Baker  in  a paper  communicated  to  the  Journal 
of  the  Chemical  Society  in  1902,  points  out  that  he  was  able  to  completely 
liquefy  starch-paste  by  barley  diastase,  in  from  two  to  three  hours  at 
50°  C.,  with  the  production  of  dextrin  and  maltose.  The  raw^  grain  diastase 
is  probably  an  unused  residue  of  an  enzyme  produced  during  the  previous 
history  of  the  plant. 

267.  “ Artificial  Diastase  ” of  Reychler. — ^This  worker  digested  freshly 
prepared  wheat  gluten  at  30-40°  for  a few  hours  with  very  dilute  acids, 
and  thus  formed  an  opalescent  solution  containing  considerable  quantities 
of  proteins.  The  solution  is  not  coagulated  by  boiling  ; it  gives  a pre- 
cipitate with  a few  drops  of  very  dilute  potash,  soluble  in  excess.  Tincture 
of  guaiacum  and  h3^drogen  peroxide  produce  an  intense  blue  colouration, 
but  not  if  the  solution  has  been  previously  boiled  or  treated  with  too  much 
acid.  A solution  of  the  gluten  from  10  grams  of  wheat  flour  in  50  c.c.  of 
dilute  acetic  acid  (1  in  10,000)  gives  this  reaction,  which  according  to 
Lintner  is  characteristic  of  diastase  most  distinctly.  Reychler  finds  such 
solutions  to  possess  a similar  hydrolytic  action  to  that  possessed  by  diastase, 
and  states  that  they  saccharify  starch-pas^e.  Reychler  finds  also  that  the 
soluble  proteins  of  wheaten  flour  give  Lintner’s  diastase  reaction  and  hydro- 
l3"se  starch. 

Brown  and  Morris  refer  to  Reychler’s  researches  on  artificial  diastase, 
but  point  out  that  the  starch  transforming  powers  of  the  product  are  essen- 
tially different  from  those  of  malt  diastase.  Lintner  and  Eckhardt  doubt 
the  existence  of  Reychler's  “ artificial  diastase,'"  and  consider  it  probably 
identical  with  the  enzyme  of  ungerminated  grain,  and  not  a conversion- 
])roduct  of  the  gluten.  This  view  is  based  on  the  fact  of  a close  examination 
1)3"  them  of  the  product  of  the  action  of  dilute  acid  upon  the  gluten  of  wheat. 
They  found  the  gluten  itself  to  possess  diastatic  power,  which  power  was 
greatly  increased  by  the  action  of  acids,  the  resultant  enzyme  closely  agree- 
ing with  raw  grain  diastase  in  its  optimum  temperature  of  activity  and 
general  character.  They  conclude  that  gluten  contains  a zymogen  (enzyme 
generating  substance),  from  which  the  artificial  diastase  is  produced  by 
the  action  of  the  dilute  acid.  Egoroff  experimented  by  dissolving  gluten 
in  0*1  per  cent,  acetic  acid,  but  found  no  fresh  diastase  to  be  formed,  and 
enunciated  the  opinion  that  the  greater  power  possessed  by  these  and  aqueous 
solutions  of  converting  starch  into  maltose  is  probably  due  to  the  develop- 
ment of  a bacterium  capable  of  effecting  this  transformation.  Moritz, 
and  Morris  practically  endorse  Lintner's  view  on  this  matter,  and  suggest 
the  identity  of  “ artificial  diastase  " with  that  of  raw  grain.  There  are 
two  points  of  discrepancy  here  : first,  the  enzyme  of  ungerminated  grain 
is  soluble  in  water,  and  must  be  entirely  washed  away  in  the  preparation 
of  gluten  ; second,  Reychler  distinctly  states  that  his  artificial  diastase 
acts  upon  starch-pas^e,  and  describes  how  he  prepares  the  same,  namely, 
by  making  2 grams  of  starch  into  a “ paste  " with  250  c.c.  of  water. 

It  is  interesting  to  note  that  as  early  as  1879,  Brown  and  Heron  pointed 
out  that  the  comparatively  inactive  proteins  of  barley,  and  also  wheat. 


136 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


may  be  rendered  more  efficient  as  diastatic  bodies,  after  being  obtained 
in  solution  ; and,  consequently,  independently  of  germination.  If  cold 
aqueous  infusions  of  barley  and  wheaten  flours,  respectively,  have  a little 
compressed  yeast  added  to  them,  and  then  are  allowed  to  stand  for  a feiv 
hours  at  30°  C.,  the  solution  in  each  case  will  be  found  to  have  considerably 
increased  in  diastatic  power.  A mixture  of  yeast  and  cane  sugar,  under 
the  same  conditions,  has  no  action  whatever  on  starch  : therefore,  growing 
yeast  must  be  considered  as  capable  of  producing  certain  changes  in  the 
inactive  proteins  of  wheat  and  barley,  by  means  of  which  they  are  enabled 
to  act  on  starch.  Such  action  on  starch  is,  however,  caused  by  the  affected 
proteins,  and  not  by  the  yeast  itself.  While  saccharomyces  act  thus  on 
wheat  proteins,  the  schizomycetes  not  merely  confer  no  diastatic  power, 
but  rapidly  destroy  that  which  the  solutions  may  have  originally  possessed. 
It  is  possible  that  the  action  here  ascribed  to  yeast  may  be  due  to  acidity 
formed  by  its  action. 

The  following  experiments  were  undertaken  by  one  of  the  authors  with 
the  view  of  further  elucidating  the  problem  of  artificial  diastase.  A filtered 
extract  of  flour  was  prepared  by  taking  50  grams  of  high-class  English 
flour  of  medium  strength,  and  shaking  up  with  500  c.c.  distilled  water,  in 
which  had  been  dissolved  2*5  c.c.  of  chloroform.  (The  object  of  the  addition 
of  chloroform  w^as  the  inhibition  of  any  bacterial  action,  without  hindering 
in  any  way  the  effects  of  diastase.)  This  solution  was  allowed  to  stand 
for  half-an-hour.  Altered  and  divided  into  two  portions — A and  B. 

A.  — To  portion  A,  an  equal  volume  of  chloroform  water  was  added, 
and  the  diastatic  value  on  soluble  starch  by  Lintner’s  scale  determined 
immediately  in  a part  of  the  solution,  according  to  the  method  described 
in  the  analytic  section  of  this  work.  Another  portion  of  this  diluted  solution 
was  treated  precisely  similarly,  except  that  freshly  prepared  starch  paste 
was  substituted  for  Lintner’s  soluble  starch. 

Al. — The  diastasic  action  reckoned  on  the  flour  was — 

With,  soluble  starch  . . . . . . 9*4°  Lintner. 

With  starch-paste  . . . . . . . . 5 0°  ,, 

B.  — To  portion  B,  an  equal  volume  of  0*2  per  cent,  hydrochloric  acid 
in  chloroform  water  was  added,  and  another  pair  of  similar  determinations 
to  those  preceding  made  immediately,  with  the  following  results  : — 

Bl. — The  diastatic  action  reckoned  on  the  flour  was — 


With  soluble  starch 
With  starch-paste 


less  than  2*5°  Lintner,  there  being 
practically  no  action  whatever. 

The  plain  5 per  cent,  solution  A,  and  the  5 per  cent,  solution  in  0*1 
per  cent,  hydrochloric  acid,  B were  then  digested  for  twenty  hours  at  30-35° 
C.,  and  the  diastatic  capacity  again  measured  with  results  as  follows  : — 
A2,  with  soluble-starch  . . 14*3°  Lintner. 

,,  with  starch  paste  . . 4*5°  ,, 


B2,  with  soluble  starch 
vdth  starch-paste 


less  than  2*5^ 


,,  practically  no 
action. 

In  the  next  place,  25  grams  of  flour  were  taken  with  250  c.c.  chloro- 
form water,  shaken  and  digested  together  for  twenty  hours  at  30-35° 

C.,  giving  preparation  C.  Another  25  grams  were  similarly  treated  with 
250  c.c.  of  0-1  percent,  hydrochloric  acid  in  chloroform  water,  and  digested, 
being  preparation  D.  After  digestion,  diastatic  measurements  were  made 
in  the  clear  filtrate,  with  the  following  results  : — 

C,  with  soluble  starch  . . 10-0°  Lintner. 

„ with  starch-paste  . . 4*0°  ,, 

D,  with  soluble  starch 
„ with  starch-paste 

Digestion  with  0*1  per  cent,  hydrochloric  acid  not  only  does  no  confer 


less  than  2-5^ 


ENZYMES  AND  DI ASTATIC  ACTION.  ’ 137 


additional  diastatic  capacity,  but  practically  inhibits  any  such  power  the 
flour  naturally  possessed. 

A series  of  experiments  was  next  made,  in  which  0*01  per  cent,  acetic  acid 
was  substituted  for  the  hydrochloric  acid.  As  previously,  all  solutions  were 
treated  with  chloroform  to  prevent  any  action  of  bacteria.  Of  the  same 
flour  as  before,  25  grams  were  taken,  shaken  up  Avith  250  c.c.  of  water,  and 
filtered  after  half-an-hour  standing.  An  equal  volume  of  0-02  per  cent, 
acetic  acid  was  added,  making  a 0-01  per  cent,  acetic  acid  solution,  called  E. 
Preparation  F consisted  of  25  grams  of  flour  with  250  c.c.  of  0 01  per  cent, 
acetic  acid,  shaken  up  and  not  filtered.  These  Avere  digested  for  tAventy 
hours  at  30-35°  C.,  and  the  mixture  F filtered.  In  each,  diastase  deter- 
minations AA’ere  then  made,  both  Avitli  soluble  starch  and  starch  paste. 


E,  Avitli  soluble  starch 
,,  AA'ith  starch  paste 

F,  AAuth  soluble  starch 
,,  AA'ith  starch  paste 


26-3°  Lintner. 
15.1° 

29*4° 

16*6° 


These  experiments  shoAv  that  very  dilute  acid  (O-Ol  per  cent,  acetic) 
considerably  increases  diastatic  activity,  even  Avlien  any  possible  bacterial 
action  is  prevented,  by  the  presence  of  chloroform,  throughout  the  Avhole 
course  of  the  experiment.  Comparing  A 2,  AAiiich  Avas  a plain  solution  of 
the  flour,  digested  for  tAventy  hours  after  filtration,  Avith  E,  Avhich  Avas  a 
solution  of  the  same  strength,  acidulated  to  the  extent  of  0*01  per  cent, 
with  acetic  acid,  after  filtration  but  before  digestion,  there  is  an  increase  in 
diastatic  capacity  from  14*3°  to  26*3°  Lintner  on  soluble  starch,  and  from 
4*5°  to  15*1°  on  starch  paste.  The  diastatic  activity  of  the  proteins  actually 
in  solution  has  been  definitely  increased  by  this  treatment.  It  should  be 
noticed  also  that  the  particular  diastase  present  is  not  only  capable  of  con- 
verting soluble  starch,  but  also  hydrolyses  starch  paste. 

In  D and  F,  the  Avhole  flour  and  water,  and  dilute  acid  respectively,  Avere 
digested  together  before  filtration.  Again  there  is  an  increase  in  diastatic 
capacity.  From  a comparison  of  E and  F,  it  AA^ould  seem  that  very  little  of 
the  increased  diastatic  action  is  due  to  any  change  in  the  insoluble  protein  of 
the  flour,  as  the  F results  are  only  slightly  in  excess  of  those  in  E.  It  is 
curious  to  note  that  in  A2  and  C,  both  experiments  with  plain  Avater,  diges- 
tion after  filtration  yields  a more  active  product  than  digestion  before 
filtration. 


268.  Invertase. — ^Although  diastase  is  unable  to  carry  the  hydrolysis 
of  starch  further  than  into  maltose,  yet,  as  already  stated,  there  is  evidence  of 
malt  extract  containing  an  enzyme  capable  of  converting  cane-sugar  into  glu- 
cose. BroAvn  and  Heron  adduce  experimental  proof  of  this  point  in  a contribu- 
tion to  the  Journal  of  the  Chemical  Society,  Vol.  XXXV,  1879,  page  609  ; 
they  show  that  a cane-sugar  solution,  after  being  digested  for  16  hours  at 
55°  C.  Avith  cold  water  extract  of  malt,  contained  £0*4  per  cent,  of  glucose. 
If,  on  the  other  hand,  the  malt  extract  were  previously  boiled  for  15  minutes, 
the  percentage  of  invert  sugar  Avas  reduced  to  0*2  per  cent.  This  enzyme 
has  been  termed  zymase,  but  is  noAV  knoAvn  as  invertase,  the  former  name, 
being  applied  to  another  enzyme,  Avhich  Avill  subsequently  be  described. 
For  practical  purposes  the  principal  source  of  invertase  is  beer-yeast,  from 
Avhich  it  may  be  separated  in  a fairly  concentrated  form.  O’Sullivan  and 
Tompson  recommend  for  this  purpose  that  sound  breAvers’  yeast  be  pressed, 
and  then  kept  at  the  ordinary  temperature  for  a month  or  tv^o,  during  AA'hich 
time  it  does  not  undergo  putrefaction,  but  changes  into  a heavy  yellow  liquid. 
On  filtering,  this  yields  a clear  solution  of  high  hydrolytic  poAver,  contain- 
ing all  the  invertase  of  the  yeast  in  solution.  This  liquid  has  a specific 


138 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gravity  of  about  lOSO,  and  is  termed  ‘‘  yeast  liquor  ” by  O’Sullivan  emd 
Tompson.  This  liquor  remains  for  a long  time  unaltered,  except  for  a darken- 
ing of  colour.  On  adding  spirit  to  yeast  liquor  till  it  contains  47  per  cent,  of 
alcohol,  the  invertase  is  precipitated,  and  may  be  washed  with  spirit  of  the 
same  strength  and  dried  in  vacuo,  or  preserved  as  a solution  by  extracting 
the  precipitate  with  10  per  cent,  alcohol,  and  filtering,  when  the  filtrate  con- 
tains the  invertase. 

Invertase  acts  rapidly  on  cane-sugar  according  to  the  equation : — ■ 

C12H22O11  = C6H12O6  "I-  C6H12O6. 

Cane-sugar.  Glucose.  Fructose. 

This  speed  of  inversion  increases  rapidly  with  the  temperature  until  55- 
60°  is  reached.  At  65°  invertase  is  slowly,  and  at  75°  immediately  destroyed. 
Minute  quantities  of  sulphuric  acid  are  exceedingly  favourable  to  the  action, 
but  a slight  increase  of  acidity  beyond  the  favourable  point  is  very  detri- 
mental. A sample  of  invertase  which  had  produced  inversion  of  100,000 
times  its  own  weight  of  cane-sugar  was  still  active  ; and  further,  invertase 
itself  is  not  injured  or  destroyed  by  its  action  on  cane-sugar.  There  is 
evidently  no  limit,  therefore,  to  the  amount  of  sugar  which  can  be  hydrolysed 
by  a given  amount  of  invertase.  The  caustic  alkalies,  even  in  very  small 
proportions,  are  instantly  and  irretrievably  destructive  of  invertase.  Inver- 
tase is  without  action  on  starch,  dextrin,  maltose,  glucose,  fructose  and  gum. 

Osborne  has  prepared  invertase  in  an  exceedingly  pure  form,  and  finds  it 
to  give  none  of  the  protein  reactions,  except  precipitation  by  copper  sul- 
phate, lead  acetate,  and  phospho-tungstic  acid  ; though  it  gave  Millon’s, 
the  xanthoprotein,  and  biuret  reactions  very  faintly.  He  therefore  con- 
cludes that  it  is  not  protein  in  nature. 

269.  Maltase. — In  addition  to  invertase,  Lintner  regards  yeast  as 
containing  another  and  distinct  enzyme,  to  which  has  been  given  the  name  of 
maltase.  This  body  possesses  the  power  of  changing  maltose  into  glucose. 

270.  Intestinal  Invertase. — The  secretions  of  the  small  intestines  contain 
an  enzyme  allied  to  the  invertase  of  beer-yeast,  inasmuch  as  it  inverts  cane- 
sugar  into  glucose  and  fructose ; it  also  inverts  maltose  into  glucose,  thus 
differing  from  the  invertase  of  yeast,  which  has  no  action  on  maltose.  Brown 
and  Heron  state  that  it  acts  on  starch,  but  Halliburton  is  of  opinion  that  the 
bulk  of  evidence  is  against  the  presence  of  any  such  diastatic  action. 

271.  Pepsin,  or  Peptasc,  and  Trypsin. — Collectively,  the  fluids  of  the 
stomach  are  known  as  gastric  juice,  and  contain  an  active  proteolytic  enzyme 
termed  pepsin.  Pepsin  may  be  obtained  from  the  mucous  membrane  of  the 
stomach  by  extraction  with  glycerin,  in  which  pepsin  is  soluble.  The  pepsin 
is  precipitated  from  its  glycerin  solution  by  alcohol,  dissolved  in  water  and 
freed  from  salts  and  peptones  by  dialysis.  Pepsin  is  soluble  in  water  to  a 
mucous  liquid,  but  is  insoluble  in  alcohol  or  ether.  Pepsin  has  been  pre- 
pared by  Pekelharing  in  a comparatively  pure  state  ; he  finds  it  to  give  the 
majority  of  protein  reactions,  but  not  to  contain  phosphorus,  thus  negativ- 
ing any  possibility  of  its  belonging  to  the  nucleo-proteins.  In  the  presence 
of  an  acid,  preferably  hydrochloric,  pepsin  attacks  and  rapidly  dissolves 
insoluble  protein  substances,  as  the  white  of  hard-boiled  eggs  or  lean  beef, 
converting  them  into  peptones.  Pepsin  is  most  active  at  about  40°  C.,  and 
loses  its  power  on  exposure  to  57-58°.  The  acid  condition  is  necessary  to  its 
action,  and  is  supplied  in  the  gastric  juice  by  the  presence  of  hydrochloric 
acid,  which  in  the  gastric  juice  obtained  from  the  human  stomach  amounts  to 
0 02  per  cent.,  and  in  that  of  the  dog  to  0*30  per  cent.  The  energy  of  pepsin 
is  impaired,  and  at  last  arrested  by  the  peptones  produced.  Dried  pepsin 


ENZYMES  AND  DIASTATIC  ACTION. 


139 


may  now  be  obtained  as  an  article  of  commerce,  being  prepared  by  drying 
under  100°  F.  the  fresh  mucous  lining  of  the  stomach  of  the  pig,  sheep,  or  calf. 
In  accordance  with  the  scheme  of  nomenclature  in  which  the  names  of  the 
enzymes  end  in  ase,  the  name  of  this  body  is  frequently  written  peptase. 

Trypsin  occurs  in  the  pancreatic  juice,  and  is  allied  in  its  general  behaviour 
to  pepsin,  possessing  like  it  the  power  of  converting  proteins  into  peptones, 
It  differs,  however,  in  the  fact  that  it  acts  best  in  an  alkaline  medium,  and 
less  energetically  in  neutral  or  slightly  acid  solutions.  The  action  is  arrested 
by  the  presence  of  hydrochloric  acid  in  excess. 

272.  Proteolytic  Enzyme  of  Resting  and  Germinating  Seeds. — Seeds 
generally  appear  to  contain  a proteolytic  enzyme  in  the  form  of  a zymogen, 
which  during  the  act  of  germination  becomes  converted  into  an  active  en- 
zyme, termed  protease.  This  body  converts  the  proteins  of  the  seed  into  pep- 
tones, leucin,  and  tyrosin.  Malt  extract  exerts  a marked  physical  and 
chemical  effect  on  the  proteins  of  flour  during  bread  fermentation,  a result 
due  to  the  presence  of  a proteolytic  enzyme,  or  form  of  protease. 

273.  Zymase. — Recent  researches  by  Buchner  and  others,  (Berichte  d. 
DeutscJi.  cliem.  Ges.,  1897),  have  shown  that  when  yeast  is  ground  up  with 
sand  and  kieselguhr,  and  then  subjected  to  filtration  under  hydraulic  pres- 
sure, a liquid  is  obtained  which  is  free  from  yeast  cells,  and  yet  is  capable  of 
converting  sugar  in  solution  into  alcohol  and  carbon  dioxide.  The  chemical 
action  commences  in  something  under  an  hour  and  continues  regularly  for 
some  days.  By  treatment  with  alcohol,  an  active  principle  can  be  separated 
from  the  yeast  filtrate.  Buchner  proposed  the  name  zymase  for  this  sub- 
stance, and  has  proved  its  action  to  be  due  neither  to  yeast  cells  nor  to  frag- 
ments of  yeast  protoplasm  contained  in  the  liquid.  Zymase  is,  therefore, 
to  be  regarded  as  a definite  member  of  the  enzyme  group. 

274.  Other  Enzymes. — -Among  other  enzymes  mentioned  in  the  classified 
list  previously  given,  a word  should  be  said  about  those  included  in  the 
group  of  coagulative  enzymes.  The  coagulation  of  blood  on  leaving  the 
body  is  due  to  an  enzyme  ; so  also  is  that  of  muscle  at  death,  in  the  case 
of  the  stiffening  termed  rigor  mortis,  known  in  this  instance  as  the  myosin- 
ferment  or  enzyme.  Interest  attaches  to  this,  as  the  animal  analogue 
of  Weyl  and  Bischoff's  hypothetical  myosin,  to  which  they  ascribe  the 
formation  of  gluten  in  the  doughing  of  wheaten  flour. 

Space  does  not  permit  any  further  reference  to  the  emulsive  and  steato- 
lytic enzymes. 


Details  of  Applied  Hydrolysis. 

275.  Empirical  Statement  of  Hydrolysis  of  Starch. — It  will  be  seen  that 
the  formulae,  representing  the  probable  constitution  of  the  molecules, 
are  much  more  complex  than  the  empirical  formulae  respectively  of  starch 
and  dextrin.  The  following  empirical  equation  represents  in  the  simplest 
possible  manner  the  above  reaction  ; it  must  not,  however,  be  viewed 
as  representing  the  true  nature  of  the  molecular  change  involved  : — 

(CsHioOsjs  + 2H2O  = CeHioOs  + 2Ci2H220n. 

Soluble  Starch.  Water.  Dextrin.  Maltose. 

276.  Hydrolysis  of  Cane-Sugar. — ^This  operation  is  slowly  effected  by 
the  action  of  malt  extract,  or  even  by  prolonged  boiling  with  water,  which 
effects  the  same  change  more  or  less  completely.  At  ordinary  tempera- 
tures, dilute  sulphuric  and  hydrochloric  acids  are  capable  of  slowly  in- 
verting cane-sugar  ; at  temperatures  of  from  65°  to  70°  C.  the  hydrolysis 


.140 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


occurs  with  extreme  rapidity.  For  laboratory  purposes,  complete  inversion 
is  effected  by  adding  to  the  moderately  strong  sugar  solution  one-tenth 
its  volume  of  strong  hydrochloric  acid,  and  then  heating  the  mixture  in  a 
water-bath  until  the  temperature  reaches  about  68°  C.  The  change  con- 
sists of  the  cane-sugar  molecule  splitting  up  into  two  molecules  of  glucose, 
the  one  being  dextro  and  the  other  laevo-rotary — 

C12H22O10  + H2O  = C6H12O6  -h  C6H12O6. 

Cane-Sugar.  Water.  Dextro-glucose.  Lsevo-glucose. 

Invertase  also  effects  this  change,  and  apparently  is  likely  to  be  em- 
ployed commercially  for  the  purpose.  O’Sullivan  recommends  its  employ- 
ment in  the  laboratory  for  the  hydrolysis  of  cane-sugar  as  a step  towards 
its  analytic  estimation. 

277.  — Hydrolysis  of  Dextrin. — By  the  action  of  acids,  and  also  of  malt 
extract,  this  body  may  be  entirely  converted  into  maltose  : the  nature 
of  the  chemical  change  has  been  described  when  treating  of  the  hydrolysis 
of  starch.  Under  ordinary  conditions,  neither  invertase  nor  yeast  itself 
is  capable  of  effecting  the  hydrolysis  of  dextrin. 

278.  Hydrolysis  of  Maltodextrin. — This  change  is  readily  effected  by 
the  action  of  malt  extract,  but  not  by  either  invertase  or  yeast. 

279.  Hydrolysis  of  Maltose  . — Maltose  is  a more  stable  sugar  than  is 
cane-sugar  : dilute  acids  effect  its  conversion  with  slowness  ; thus  a maltose 
solution  may  be  boiled  for  some  minutes  with  dilute  sulphuric  acid  without 
undergoing  change.  Complete  inversion  results  from  keeping  the  solution 
at  a temperature  of  100°  C.  for  some  six  or  eight  hours.  The  principal 
product  of  inversion  is  glucose.  As  has  been  previously  stated,  malt  extract 
has  no  hydrolysing  action  on  maltose.  Invertase  also  is  without  action 
on  maltose,  but  maltase  effects  its  hydrolysis. 

280.  Composition  of  Malt. — Prior  to  dealing  with  the  saccharification 
of  malt,  some  information  should  be  given  of  its  composition.  Treatment 
of  the  general  questions  of  the  transformation  of  barley  into  malt  must 
be  postponed  until  the  subject  of  the  physiology  of  grain  life  is  being  dis- 
cussed. Malts  differ  from  barley  in  that  the  protein  constituents  show 
proofs  of  considerable  degradation.  Hilger  and  Van  der  Becke  have  exam- 
ined barley,  barley  softened  by  steeping  in  water,  fresh  or  green  malt  (un- 
kilned), and  kiln-dried  malt.  The  following  table  gives  the  percentage 
of  nitrogen,  and  of  the  various  nitrogenous  constituents  : — 


Nitrogeneous  Constituents  of  Barley  and  Malt. 


Barley. 

Softened 

Barley. 

Fresh  Malt. 

Dried  Malt. 

Total  Nitrogen 

1-801 

1-750 

1-751 

1-542 

Nitrogen  of  Insoluble  constitu- 
ents . . 

1-6789 

1-6853 

1-372 

1-165 

Nitrogen  as  Albumin  (soluble) 

0-0600 

0-0354 

0-1571 

0-1194 

. as  Peptone  . . 

0-0046 

0-0009 

0-0058 

0-0233 

,,  as  Ammonium  Salts 

0-0169 

— 

0-0290 

0-0057 

,,  as  Amino-acids 

0-0417 

0-0294 

0-1417 

0-2257 

,,  as  Amides  . . 

— 

0-0505 

0-0029 

ENZYMES  AND  DIASTATIC  ACTION. 


141 


It  will  be  seen  that  the  insoluble  proteins  have  diminished  in  quantity, 
while  the  albumin  has  increased  ; so  also  have  the  products  of  further 
degradation,  peptone,  amino-acids,  and  amides. 

The  starch  in  barley  also  suffers  considerable  diminution  ; Brown  and 
Morris  found  the  quantities  of  starch  in  barley  before  and  after  germination 
to  amount  to 


Starch  ix  1000  Corns. 


i 

Starch  in  Barley  Starch  in  Barley  after 

before  Germination.  Six  Days’  Germination. 

Loss  of  Starch. 

' Expt.  1 

9 

>5  w • • 

20*0552  grams.  15*4398  gTams. 

19*9158  „ 15*3836  „ 

4-6154  grams. 
4-5522  „ 

Taking  the  mean  of  the  two  experiments,  22*5  per  cent,  of  the  starch 
has  disappeared.  A portion  of  this  has  been  dissipated  as  carbon  dioxide 
gas,  a portion  will  have  constituted  the  material  from  which  the  new  parts 
of  the  plant  have  been  formed,  while  a third  portion  will  have  been  changed' 
into  sugars,  which  remain  in  the  malt  at  the  end  of  its  manufacture.  The 
increase  of  sugars  is  well  shown  in  the  following  table,  which  gives  in  per- 
centages the  results  of  analyses  of  barley  before  and  after  germination, 
by  O’Sullivan. 


Sugars  in  Barley  before  and  after  Germination. 


i i 

i ' 

i SUG.\RS.  j 

1 

No.  1 Barley.  ! 

No.  2 Barley. 

1 Before  ! 

Germination. 

After 

Germination. 

Before 

Germination. 

After 

Germination. 

1 Sucrose  (Cane-Sugar)  . . 

0-9 

4*5  ' 

1*39 

4*5 

Maltose  . . 

! (1-2  1 

(1*98 

i Dextrose.  . 

1 U-1 

’ 3*1 

' 0*62 

1*57 

Laevulose . . 

i ) 

; 0*2 

1 j 

lo*71 

It  will  be  seen  that  cane-sugar  forms  a very  notable  constituent  of 
malt,  and  also  that  the  other  sugars  are  present  in  large  quantity. 

The  percentage  of  acid  considerably  increases  in  grain  during  malt- 
ing ; assuming  acidity  to  be  due  to  lactic  acid,  Belohoubek  gives  the  fol- 
lowing : — 

Barley  . . . . . . . . . . 0*338  per  cent,  as  lactic  acid. 

Green  Malt  . . . . . . . . 0*590  ,,  ,,  , ,, 

Kilned  Malt 0*942  ,,  „ ,, 

In  English  malts,  however,  the  percentage  of  acid  is  considerably  less 
than  this,  being  usually  about  0*2  per  cent.  ; so  much  as  0*4  per  cent,  is 
viewed  as  an  indication  of  unsoundness.  Although  the  acidity  of  malt  is 
usually  returned  as  lactic  acid,  a considerable  amount  is  due  to  the  presence 
of  acid  phosphates. 

• The  following  table  gives  the  approximate  composition  of  malt,  based 
principally  on  analyses  by  O’Sullivan  : — 


142 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Approximate  Composition  of  Malt. 


Per  Cent, 

Per  Cent. 

Starch  . . 

4400 

to 

50-00 

Sugars  . . 

9-00 

5) 

16-00 

,,  These  include  Sucrose,  from 

4-50  ) 

1 

,,  Maltose,  ,, 

1*20 

1 

16-00 

,,  Dextrose,  ,, 

L65  I 

^ JJ 

,,  Lsevulose,  ,, 

Unfer  men  table  Carbohydrates,  not  Dextrin 

0-20  1 

1 

5-00 

55 

7-00 

Cellular  Matter  (Cellulose)  . . 

1000 

55 

12-00 

Proteins,  soluble  in  cold  water 

30 

J 5 

4-50 

,,  insoluble  ,, 

8-00 

55 

10-00 

Fat 

1-50 

5 5 

2-00 

Ash 

1-90 

5 5 

2-60 

Water  . . 

2*50 

55 

7-00 

Acid  reckoned  as  Lactic  Acid 

0-20 

5 5 

0-40 

281.  Saccharification  of  Malt  during  the  Mashing  Process. — ^This  process 
is  of  interest  both  from  the  technical  point  of  view,  as  being  largely  used 
by  the  baker,  and  also  scientifically,  as  representing  an  important  example 
of  hydrolysis  by  malt  extract.  Malt  contains  the  active  hydrolysing  prin- 
ciple, diastase,  and  also  from  44  to  50  per  cent,  of  starch.  In  the  operation 
of  malting,  the  walls  of  the  starch  granules  get  more  or  less  ruptured  and 
fissured  ; hence  the  interior  granulose  is  at  the  outset  somewhat  exposed 
to  the  action  of  the  diastase.  As  a first  step  toward  the  preparation  of 
beer,  the  brewer  treats  his  ground  malt  with  water  at  a temperature  of 
from  65-5°  C.  (150° F)  to  71 -1°  C.  (160°  F.).  This  results  in  the  conversion 
of  the  starch  present  into  dextrin  and  maltose.  This  operation  he  terms 
“ mashing.”  The  first  change  is  that  the  starch  becomes  gelatinised, 
and  is  then  freely  susceptible  to  the  action  of  diastase.  At  temperatures 
below  the  gelatinising  point  of  starch,  diastasis  also  proceeds,  but  some- 
what more  slowly  (comp.  Lintner's  table,  par.  257).  At  a temperature 
of  about  60°  C.  (140°  F.)  almost  all  the  starch,  and  also  the  amyloins,  will 
have  disappeared  in  about  twenty  minutes  ; this  point  may  be  ascertained 
by  taking  out  a drop  of  the  liquid  and  testing  it  with  iodine.  An  increase 
of  temperature  weakens  the  action  of  the  diastase  ; hence  a mashing  made 
at  60°  C.  (140°  F.)  yields  in  two  hours,  for  the  same  malt,  about  7 per  cent, 
more  dextrin  and  maltose  than  when  mashed  at  76*6°  C.  (170°  F.)  Further, 
as  might  be  expected  from  the  results  already  mentioned,  the  proportion 
of  dextrin  is  much  greater  in  the  mashing  made  at  76*6°  C.  than  at  60°  C. 
The  duration  of  the  mashing  operation  has  also  an  influence  on  the  amount 
of  dextrin  and  maltose  produced.  With  a temperature  of  62*7°  C.  (145°  F.) 
most  of  the  starch  is  converted  into  dextrin  and  maltose  within  thirty 
minutes,  but  for  some  time  after,  the  yield  of  these  continues  to  slightly 
increase.  The  proportion  of  maltose  to  dextrin  also  becomes  higher  with  a 
longer  mashing.  The  following  is  the  result  of  an  experiment  by  Graham  : — 


Length  of 

Percentage  of 

Percentage  of 

Total  percentage 

Ratio  of  Maltose 

Mashing. 

Maltose.  ^ 

Dextrin. 

of  Maltose  & Dextrin. 

to  Dextrin. 

J hour. 

48-60 

14-61 

63-21 

3-3  : 1 

1 „ 

52-35 

12-23 

64-61 

4-2  : 1 

2 hours. 

53-56 

11-39 

64-95 

4-7  : 1 

54-60 

11-05 

64-65 

4-9  : 1 

7 „ 

61-47 

3-53 

65-00 

17-4  : 1 

It  will  be  seen  that  by  far  the  greatest  proportion  of  the  transformation 
is  effected  within  the  half-hour,  while  for  all  practical  purposes  the  hydrolysis 
is  completed  within  two  hours  at  the  furthest. 


ENZYMES  AND  DIASTATIC  ACTION. 


143 


282.  Mashing  Malt  together  with  Unmalted  Grain. — ^The  diastase  of 
good  malt  is  not  merely  capable  of  saccharifying  its  own  starch,  but  is 
competent  also  to  hydrolyse  in  addition  considerable  quantities  of  starch 
from  other  sources  ; hence,  in  brewing  operations,  malt  is  frequently  mixed 
with  flour  from  other  cereals,  either  rice  or  maize  being  commonly  chosen. 
The  diastase  of  the  malt  saccharifies  the  whole  of  the  starch  present  ; but 
with  the  proportion  of  malt  unduly  low,  the  ratio  of  maltose  to  dextrin 
produced  is  comparatively  small. 


Experimental  Work. 

283.  Hydrolysis  of  Starch. — ^Mix  10  grams  of  starch  with  200  c.c.  of 
water,  and  gelatinise  by  placing  in  the  hot  water-bath.  Take  50  c.c.  of 
this  solution  and  add  to  them  10  c.c.  of  five  per  cent,  sulphuric  acid.  Main- 
tain at  a temperature  of  100°  C.  until  a few  drops,  taken  out  with  a glass 
rod  or  tube,  and  placed  on  a porcelain  tile,  give  no  blue  colouration  on 
addition  of  iodine.  To  the  solution  add  precipitated  calcium  carbonate, 
or  powdered  marble,  until  it  ceases  to  produce  effervescence.  Allow  the 
precipitate  to  subside,  and  filter  ; taste  the  clear  solution,  notice  its  sweet- 
ness. Test  a portion  of  this  filtered  solution  with  Fehling’s  solution,  a red 
precipitate  is  produced,  showing  that  either  maltose  or  glucose  is  present. 

To  a test  tube,  containing  another  portion  of  the  original  starch  solu- 
tion, add  some  saliva,  and  stand  it  in  a water-bath  at  a temperature  of 
about  40°  C.  for  some  time  : notice  that  the  solution  becomes  more  limpid, 
and  ultimately  that  it  gives  no  starch  reaction,  on  a few  drops  being  taken 
out  and  treated  with  iodine.  Test  now  for  maltose,  by  means  of  Fehling's 
solution  ; a red  precipitate  is  produced.  As  a complement  to  this  experi- 
ment, boil  some  corn-flour  and  water,  allow'  the  paste  to  cool,  place  a spoon- 
ful in  the  mouth,  retaining  it  there  for  some  fifty  or  sixty  seconds,  and 
mixing  it  w ith  saliva  by  means  of  the  tongue  : notice  that  the  paste  becomes 
limpid,  and  acquires  a sweet  taste. 

Take  some  fresh  compressed  yeast,  mix  a little  wdth  some  of  the  starch 
solution  and  place  in  the  w'ater-bath  at  40°  C.  Notice  that  after  several 
hours  the  starch  remains  unaltered,  giving  a blue  colouration  with  iodine, 
and  little  or  no  reaction  wdth  Fehling’s  solution.  Prepare  some  “ yeast- 
W'ater  by  shaking  up  about  50  grams  of  the  compressed  yeast  wdth  150 
c.c.  of  cold  water  ; let  this  stand  for  from  four  to  six  hours,  shaking  occa- 
sionally, then  allow  to  subside  and  filter  the  supernatant  liquid.  Treat 
some  starch  solution  wdth  this  yeast-w'ater  in  the  same  w^ay  as  with  the 
yeast  itself  : notice  that  this  also  causes  no  alteration  in  the  starch. 

Make  an  aqueous  extract  of  malt,  as  described  in  paragraph  255.  Take 
some  sound  wheat  starch,  examine  it  under  the  microscope,  to  see  that 
none  of  the  granules  are  fissured  or  cracked.  Add  some  of  the  malt  extract 
to  a portion  of  this  starch,  and  allow"  it  to  remain  for  some  hours  at  a tem- 
perature of  20°  C.  Maintain  another  similarly  prepared  sample  at  a tem- 
perature of  40°  C.  for  from  six  to  tw'elve  hours.  At  intervals  from  the 
time  of  starting  the  experiment,  and  at  the  end  of  the  time,  examine  the 
starch  in  each  case  carefully  under  the  microscope,  in  order  to  see  w'hether 
any  of  the  granules  show  signs  of  cracking  or  pitting.  Make  a comparative 
series  of  experiments  on  potato  starch.  In  every  experiment,  at  the  end 
test  the  starch  granules  w ith  iodine,  in  order  to  see  w'hether  they  still  give 
the  starch  reaction. 

Shake  up  some  starch  wdth  w'ater,  and  filter  : notice  that  the  clear 
filtrate  gives  no  reaction  wdth  iodine.  Rub  a little  of  the  starch  in  a mor- 
tar with  powdered  glass  ; this  cuts  the  cellulose  envelopes.  Shake  up 
with  W"ater,  and  filter  ; to  the  clear  filtrate  add  iodine  solution  : a blue 


144 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


colouration  shows  the  presence  of  soluble  starch.  To  some  of  the  bruised 
starch  add  malt  extract,  and  allow  to  stand  for  twenty-four  hours  at  20° 
or  25°  C.,  examine  under  the  microscope,  and  notice  that  much  of  the 
interior  of  the  cells  is  dissolved  away.  Treat  a little  with  iodine,  and 
examine  under  the  microscope  in  order  to  determine  how  much  unaltered 
starch  remains.  Make  some  starch  paste,  as  described  in  paragraph  259  ; 
treat  it  with  malt  extract  as  there  mentioned,  and  at  intervals  of  a minute 
take  out  a drop  of  the  solution  by  means  of  a glass  rod,  and  test  with  iodine 
on  a porcelain  tile.  Note  the  time  when  the  starch  and  the  amyloins  dis- 
appear. Make  a series  of  similar  experiments  with  varying  temperatures, 
rising  by  10°  C.  at  a time,  from  15°  C.  to  the  point  at  which  diastasis 
ceases.  The  quantities  of  solution  should  be  measured  ; and  in  each  case, 
both  the  starch  and  the  malt  extract  solutions  should  be  allowed  to  stand 
in  the  water-bath,  regulated  to  the  desired  temperature,  until  both  have 
acquired  that  temperature,  then  mix  the  two  and  note  the  time.  If  desired, 
the  bath  may  be  regulated  for  this  experiment  by  means  of  the  regulator 
described  and  figured  in  Chapter  XI.  ; in  that  case  it  is  not  absolutely 
necessary  to  get  the  temperature  nearer  than  a degree,  but  the  exact  tem- 
perature, as  read  by  a thermometer,  should  be  noted. 

Make  a cold  aqueous  infusion  of  bran  or  pollard  in  the  same  way  as 
described  for  malt,  and  treat  starch  solution  with  it,  as  was  done  with 
the  malt  extract,  both  in  the  cold  and  at  higher  temperatures.  If  separated 
wheat  germ  is  obtainable,  make  a similar  series  of  experiments  with  that 
substance. 

284.  Hydrolysis  of  Cane-sugar. — ^Mix  cane-sugar  solution  with  strong 
hydrochloric  acid,  and  heat  to  68°  or  70°  C.,  as  described  in  paragraph 
276.  After  hydrolysis,  test  for  reducing  sugars  by  Eehling's  solution.  To 
another  portion  of  the  cane-sugar  solution  add  some  yeast-water,  and  main- 
tain for  three  or  four  hours  at  40°  C.,  after  which  test  for  maltose  or  glucose 
by  means  of  .Eehling’s  solution. 

285.  Mashing  of  Malt. — Take  100  grams  of  ground  malt,  and  mix  with 
500  c.c.  of  water  at  60°  C.  in  a large  beaker  ; weigh  the  beaker  and  its 
contents,  and  place  it  in  a water-bath  at  60°  C.  Stir  occasionally,  and 
from  time  to  time  take  out  small  quantities  of  the  well-stirred  liquid  on 
the  end  of  a glass  rod,  and  test  for  starch  by  iodine  solution.  Note  how 
long  it  is  before  the  starch  disappears  ; as  soon  as  iodine  produces  no  blue 
reaction,  wipe  the  outside  of  the  beaker,  place  it  in  the  balance,  and  add 
distilled  water  until  that  lost  by  evaporation  has  been  replaced  : when 
this  point  is  reached  the  beaker  weighs  just  the  same  as  before  being  placed 
in  the  bath.  Then  filter  the  clear  solution,  cool  rapidly  to  15°  C.,  and 
take  the  density  by  means  of  a hydrometer.  The  method  of  using  the 
hydrometer,  and  the  conclusions  to  be  drawn  from  the  density  of  the  wort, 
are  described  in  the  paragraph  on  “ Specific  Gravity  of  Worts  ''  in  Chapter 
XII  Make  similar  masliings  at  the  temperatures  respectively  of  50°  and 
70°  C.  ; note  in  each  case  the  time  requisite  for  saccharification,  and  the 
density  of  the  wort.  For  the  different  experiments  both  the  mashing 
liquor  and  the  bath  must  be  regulated  to  the  temperature  desired. 

286.  Substances  inimical  to  Diastasis. — Prepare  some  starch  solution 
and  malt  extract  as  in  paragraph  283.  To  a portion  of  the  malt  extract 
add  a small  quantity  of  caustic  potash,  and  note  the  time  it  takes  to  sac- 
charify the  starch,  both  starch  and  malt  being  used  in  the  same  proportions 
as  before.  Make  similar  tests  with  solutions  of  sulphuric,  tartaric  and 
salicylic  acids  ; lime,  copper,  sulphate,  alum,  borax,  alcohol,  and  essence 
of  turpentine. 


CHAPTER  IX. 


FERMENTATION. 

287.  Origin  of  Term. — When  a little  of  the  substance  called  yeast  is 
added  to  some  wort  (i.e.,  the  sweet  liquid  produced  by  the  infusion  of  malt 
with  warm  water),  at  a temperature  of  about  18°  C.,  it  induces  a most 
remarkable  change.  The  quiescent  liquid  after  a time  becomes  filled 
\vith  bubbles  ; these  rise  to  the  surface  and  form  a scum  there  ; as  the 
action  proceeds  these  bubbles  are  produced  with  increased  rapidity.  Their 
continuous  ascension  gives  the  liquid  a seething  or  boiling  appearance, 
and  from  this  has  arisen  the  application  of  the  term  “ fermentation  ""  to 
tliis  peculiar  phenomenon  ; that  word  being  derived  from  the  Latin  ferveo, 
I boil.  Fermentation  results  in  a disappearance  of  the  maltose  present 
in  tlie  wort,  together  with  the  production  of  alcohol  and  carbon  dioxide 
gas.  The  former  remains  in  the  liquid  ; the  latter  rises  to  the  surface 
and  causes  the  before-mentioned  boiling  appearance.  The  carbon  dioxide 
bubbles  carry  with  them  to  the  surface  a peculiar  sticky  “ scum  ” ; this 
substance  has  received  the  name  of  “ Yeast,”  and  on  being  added  to  a 
fresh  quantity  of  wort,  is  capable  of  setting  up  fermentation  therein.  During 
the  fermentation  of  wort,  the  quantity  of  this  “ scum  ” produced  is  many 
times  in  excess  of  that  in  the  first  place  added  to  the  wort. 

288.  History  of  the  Views  held  of  the  Nature  of  Fermentation. — The 

earlier  researches  and  published  articles  on  fermentation  regard  that  change 
as  one  of  spontaneous  decay.  Yeast,  with  which  fermentation  is  associated, 
vas  viewed  as  a peculiar  condition  which  nitrogenous  matter  assumed 
during  one  of  the  phases  of  its  decomposition.  That  in  this  state  it  was 
able  to  set  up  fermentation  in  a liquid,  which  was  not  at  the  time  fermenting, 
was  noticed  as  a remarkable  property  of  yeast,  which  nevertheless  was 
still  considered  as  only  nitrogenous  matter  in  a particular  stage  of  chemical 
change.  One  of  these  earlier  views  ascribed  alcoholic  fermentation  to  a 
vegeto-animal  substance  which  resided  in  grapes  as  well  as  in  corn.  When 
the  grapes  were  crushed,  and  the  flour  moistened,  this  fermentative  agent 
commenced  to  produce  active  change.  The  body  thus  capable  of  inducing 
fermentation  was  termed  a “ ferment.”  The  next  step  in  investigation 
of  this  matter  was  that  of  Thenard,  who  observed  that  the  ferment  con- 
tained nitrogen,  and  that  in  distillation  ammonia  was  yielded  ; he  there- 
fore ascribed  an  animal  nature  to  the  ferment.  (It  should  be  explained 
that  the  older  chemists  were  in  the  habit  of  looking  on  nitrogenous  organic 
matter  as  animal,  and  the  non-nitrogenous  as  vegetable  ; no  reference 
is  intended  to  the  peculiar  organic  structure  of  the  ferment.)  Opinion 
had  settled  down  to  the  view  that  yeast  was  an  immediate  principle  of 
plants,  when  the  microscope,  which  had  become  such  an  important  factor 
in  scientific  research,  was  brought  to  bear  on  the  construction  of  yeast. 
Leuwenhoeck  had,  as  early  as  1680,  discovered  that  yeast  consisted  of 
minute  granules  ; but  it  was  only  in  1836  that  de  Latour  again  called 


146 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


attention  to  its  microscopic  structure.  It  was  observed  by  him  that  yeast 
was  a mass  of  little  cells,  and,  further,  that  these  were  capable  of  repro- 
duction by  a process  of  budding.  “ Yeast,  therefore,"’  said  the  discoverer, 
“ must  be  an  organism  which  probably,  by  some  effect  of  its  growth,  effects 
the  decomposition  of  sugar  into  alcohol  and  carbon  dioxide.”  This  newly 
discovered  form  of  life  was,  after  some  discussion,  placed  among  the  fungi, 
a new  genus  being  created  for  it  by  Meyen,  to  which  was  given  the  name 
of  Saccharomyces. 

This  view  attracted  considerable  attention  from  scientists,  and  although 
the  basis  of  that  now  almost  universally  accepted,  encountered  most  uncom- 
promising opposition.  Prominent  among  its  antagonists  was  Liebig, 
who  in  1839  argued  yeast  to  be  a lifeless  albuminous  substance,  and  held 
that  the  cause  of  fermentation  is  the  internal  molecular  motion  which 
a body,  in  the  course  of  decomposition,  communicates  to  other  matter 
in  which  the  elements  are  connected  by  a very  feeble  affinity.  Said  Liebig, 
“yeast,  and  in  general  all  animal  and  vegetable  matter  in  a state  of  putre- 
faction, wiU  communicate  to  other  bodies  the  condition  of  decomposition 
in  which  they  are  themselves  placed  ; the  motion  which  is  given  to  their 
own  elements  by  the  disturbance  of  equilibrium  is  also  communicated 
to  the  elements  of  the  bodies  which  come  in  contact  with  them.”  Ampli- 
fying this  theory,  Liebig  asserted  that  the  protein  bodies  decomposed 
spontaneously,  and  the  molecular  disturbance  resulting  from  this  decom- 
position effected  also  the  decomposition  of  such  bodies  as  sugar,  when 
placed  in  contact  with  the  decomposing  proteins. 

For  some  years,  de  Latour’s,  or  the  vital  hypothesis,  Liebig’s,  or  the 
mechanical  hypothesis,  and  other  views  based  on  catalytic  action,  were 
three  contending  theories  of  fermentation. 

The  next  great  step  was  that  the  whole  problem  of  fermentation  received 
a most  careful  and  exhaustive  examination  at  the  hands  of  Pasteur,  who 
in  1857  gave  as  his  “most  decided  opinion”  that  “the  chemical  action 
of  fermentation  is  essentially  a correlative  phenomenon  of  a vital  act,  beginning 
and  ending  with  it.  I think  that  there  is  never  any  alcoholic  fermentation  without 
there  being  at  the  same  time  organisation,  development,  multiplication  of  globules, 
or  the  continued  consecutive  life  of  globules  already  formed.” 

In  1870,  Liebig  published  a long  memoir  on  fermentation,  in  which 
he  admitted  that  yeast  was  a living  organism,  but  stiU  maintained  that 
fermentation  was  a mechanical  act,  pointing  out  that  the  quantity  of 
sugar  decomposed  by  yeast  was  out  of  all  proportion  to  the  amount  of 
carbohydrate  (cellulose)  which  the  yeast  had  assimilated.  To  quote  his 
own  words — “ Yeast  consists  of  vegetable  cells  which  develop  and  multiply 
in  a solution  containing  sugar,  and  an  albuminate,  or  a substance  resulting 
from  an  albuminate  ...  It  is  possible  that  the  physiological  process 
stands  in  no  other  relation  to  the  process  of  fermentation  than  that  by 
means  of  it  a substance  is  formed  in  the  living  cell,  which,  by  an  action 
peculiar  to  itself — resembling  that  of  emulsin  on  salicin  or  amygdalin 
(enzyme) — determines  the  decomposition  of  sugar  and  other  organic  mole- 
cules.” The  admission  of  the  physiological  action  of  yeast  being  even 
indirectly  associated  with  the  decomposition  of  sugars  during  fermentation 
was  an  enormous  concession  by  Liebig.  Writing  in  1895,  one  of  the  authors 
summarised  the  then  position  in  the  following  terms  : — 

“ A study  of  the  action  of  enzymes  shows  that  Liebig’s  position  is 
partly  justified  : invertase  can  be  separated  from  yeast,  and  afterwards 
is  fully  capable  of  performing  its  functions  of  inverting  cane-sugar, 
but  such  study  does  not  lead  us  to  observe  a sufficiently  close  relation- 
.ship  between  enzymic  action  and  alcoholic  fermentation  as  to  prove  ” 


FERMENTATION. 


147 


their  identity.  Still  in  many  respects  there  is  great  similar it}^  At 
present  there  is  the  marked  distinction  that  alcoholic  fermentation 
is  inseparable  from  life,  while  enzymosis  occurs  in  the  absolute  absence 
of  living  organisms.  As  a result  of  prolonged  research  and  investigation 
the  vitalistic  theory  of  fermentation  is  now  practically  universally  accepted. 

“ A careful  study  of  the  preceding  sentence  shows,  however,  that  the 
statement  of  fermentation  being  a vitalistic  act  is  not  an  explanation  of 
fermentation.  Granted  that  fermentation  is  a concomitant  of  vitality 
(i.e.,  is  due  in  some  way  to  life),  there  must  be  some  agent  through 
which  life  acts  in  producing  the  chemical  change  of  sugar  into  alcohol 
and  carbon  dioxide.  In  itself,  this  change  is  no  more  striking  than  the 
change  of  starch,  by  diastase,  into  dextrin  and  maltose  ; yet  we  know 
that  diastase,  although  a direct  product  of  life,  is  a soluble  and  abso- 
lutely unorganised  body.  Is  there  any  such  unorganised  body  through 
Avhich  yeast  acts  when  effecting  the  decomposition  of  sugar  ? The 
answer  is — no  such  substance  has  as  yet  been  detected,  to  say  nothing 
of  its  isolation. 

“ Hoppe-Seyler  and  Halliburton  incline  to  the  hypothesis  that  the 
difference  between  organised  ferment  action  and  that  of  enzymes  is 
this  : an  organised  ferment  is  one  which  does  not  leave  the  living  cell 
during  the  progress  of  the  fermentation  ; an  unorganised  ferment,  or 
onzyme,  is  one  which  is  shed  out  from  the  cells,  and  then  exerts  its 
activity.  Probably  the  chemical  nature  of  the  ferment  is  in  the  two 
cases  the  same,  or  nearly  the  same. 

“ So  far  as  we  are  acquainted  with  the  nature  of  enzymes,  they  are 
either  identical  with,  or  closely  allied  to,  the  proteins.  If  fermentation 
be  due  to  an  enzyme-like  body  within  the  living  cell,  that  body  is  of 
the  nature  of  living  proteins — like  other  proteins  they  are  indiffusible, 
and  consequently  are  not  discoverable  outside  the  cell  wall.  “ Like 
all  living  things,  their  properties  during  life  are  different  from  those 
after  death  ; this  readily  accounts  for  the  fact  that,  with  a few  excep- 
tions, they  are  not  discoverable  inside  the  cell  wall  after  the  cell  has  been 
killed  by  alcohol.  The  few  exceptions  are  probably  those  which  are 
more  robust,  and  withstand  the  action  of  alcohol  better.'’  In  this 
way  does  Halliburton  endeavour  to  explain  the  difference  between 
organised  ferments  and  enzymes.  The  explanation,  unfortunately, 
does  not  cover  the  whole  problem.  Even  the  more  robust  “ ferments  " 
cannot  be  said  to  have  life  in  the  ordinary  sense  of  the  term  when 
extracted  by  dilute  alcohol,  and  obtained  in  a state  of  perfect  solution. 
Independently  of  any  organism,  the  enzymes  are  able  to  prosecute  their 
functions  ; but  alcoholic  fermentation  cannot  be  induced  by  any 
substance  contained  by  the  yeast  cell,  unless  that  cell  be  living.  If 
the  protoplasm  of  yeast  be  liberated  by  crushing  the  cells,  such  extracted 
protoplasm  does  not  cause  fermentation.  There  is  little  doubt  that 
fermentation  does  take  place  within  the  cell,  and  is  in  some  way  caused 
by  some  property  of  living  protein,  hut  it  is  an  essential  that  the  protein 
he  alive,  and  a part  of  a living  organism.  This  much  may  be  conceded, 
that  probably  the  living  protein  acts  in  a more  or  less  similar  manner 
to  an  enzyme.  In  view  of  this  it  is  interesting  to  note  the  agreement 
rather  than  the  differences  between  the  views  promulgated  by  the 
illustrious  savants  Liebig  and  Pasteur  ; but,  after  all,  there  is  the  broad 
line  of  demarcation — enzymosis  is  independent  of  living  organisms, 
while  “ fermentation  is  essentially  a correlative  phenomenon  of  a vital 
act,  beginning  and  ending  with  it.”  The  discussion  of  the  nature  of 
the  vital  act  producing  fermentation  does  not  dispose  of  the  fact  of 
its  being  vital.” 


148 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


289.  Zymase  Theory  of  Fermentation. — In  the  light  of  subsequent 
researches  these  views  must  now  be  considerably  modified.  In  1897, 
Buchner  made  the  first  announcement  of  the  discovery  of  zymase,  which 
is  referred  to  and  described  in  paragraph  273.  This  is  an  enzyme,  secreted 
within  the  yeast  cell,  but  which  may  be  extracted  from  it  and  apart  alto- 
gether from  the  living  organism  can  effect  the  decomposition  of  glucose 
into  alcohol  and  carbon  dioxide.  Work  in  this  field  of  investigation  was 
carried  still  further  by  the  researches  of  Buchner,  Rapp,  Albert,  Harden, 
and  others,  the  results  of  which  have  been  published  in  a series  of  papers 
extending  from  1897  to  1905.  The  net  result  of  such  investigation  is  to 
confirm  the  view  that  zymase  is  an  enzyme,  and  effects  the  decomposition 
of  glucose  independently  of  vital  functions  of  the  living  cell.  Of  this,  a 
striking  proof  is  afforded  by  some  experiments  of  Albert,  who  killed  yeast 
by  subjecting  it  to  the  action  of  a mixture  of  absolute  alcohol  and  ether. 
The  yeast  was  then  dried  and  still  possessed  the  power  of  exciting  alcoholic 
fermentation.  Consequent  on  the  indiffusibility  of  the  protein  eontents 
of  the  cell,  no  fermentative  enzyme  can  be  extracted  from  this  unbroken 
yeast  by  the  action  of  water.  But  if  the  eells  be  broken  up,  an  active 
extract  may  be  obtained.  A dried  preparation  of  zymase  has  been  patented, 
of  which  it  is  said  that  from  5 to  10  per  cent,  of  it  is  capable  of  raising  dough. 
Zymase  has  no  reproductive  action,  and  possesses  a fermentative  power 
which  is  only  a minute  fraction  of  that  of  yeast.  It  would  seem  that  zymase 
is  destroyed  during  fermentation  almost  immediately  as  formed,  so  that 
no  accumulated  store  of  the  enzyme  is  found  in  yeast.  Harden  believes 
that  zymase  alone  is  incapable  of  acting  on  sugar,  and  that  yeast  contains 
in  addition  another  substance  which  stimulates  the  zymase  into  activity. 
In  his  opinion  neither  of  these  alone  sets  up  fermentation  in  sugar  solutions, 
but  the  two  acting  in  conjunction  effect  the  decomposition.  In  accordance 
with  the  zymase  theory  of  fermentation,  sugar  finds  its  way  by  diffusion 
into  the  interior  of  the  living  cell  ; it  is  then  changed  into  glucose  by  the 
action  of  invertase ; then  the  decomposition  into  alcohol  and  carbon  dioxide 
is  effected  by  the  enzyme  zymase  secreted  by  the  cell  within  itself.  The 
zymase  is  being  continually  formed  and  destroyed  in  the  act  of  inducing 
fermentation.  The  discovery  of  zymase  is  the  discovery  of  the  agent  by 
w'hich  yeast  effects  the  decomposition  of  sugar  ; but  such  discovery  leads 
us  very  little  beyond  the  view  of  Pasteur  that  “ the  chemical  action  of 
fermentation  is  essentially  a correlative  phenomenon  of  a vital  act,’'  since 
tJie  zymase  is  produced  as  a function  of  the  life  of  yeast,  and  is  destroyed 
in  the  act  of  fermentation. 

290.  Definition  of  Fermentation. — The  particular  action  produced  by 
yeast  on  wort,  and  also  on  the  sweet  “must,”  or  expressed  juice  of  the 
grape,  was  found  on  investigation  to  be  but  one  of  many  chemical  actions 
whicli  are  associated  with  the  life,  growth,  and  development  of  microscopic 
organisms.  Among  these  may  be  cited  the  souring  of  milk,  also  of  wine 
into  vinegar,  and  likewise  the  changes  occurring  during  putrefaction.  Con- 
sequently tlie  term  fermentation  is  no  longer  used  in  its  original  sense,  as 
signifying  a condition  resulting  in  a peculiar  seething  or  boiling  appear- 
ance, but  is  applied  to  that  group  of  chemical  changes  which  are,  in  Pasteur’s 
words,  “ correlative  phenomena  of  vital  acts.”  Subject  to  the  limitations 
explained  in  the  preceding  paragraph,  and  used  in  its  extended  sense, 
fermentation  may  be  defined  as  a generic  term  applied  to  that  group  of  chemical 
changes  which  are  consequent  on  the  life  and  development  of  certain  minute  micrc- 
copic  organisms. 

In  the  chapter  on  the  proteins,  it  was  stated  that  putrefaction  is  regarded 
as  a species  of  fermentation  : equally,  with  the  conversion  of  maltose  into 


FERMENTATION. 


149 


alcohol  by  yeast,  it  is  a change  induced  by  living  organisms.  This  of  itself 
is  a conclusive  answer  to  Liebig’s  earlier  position,  that  fermentation  is  a 
secondary  result  of  the  spontaneous  decomposition  of  proteins,  inasmuch 
as  that,  in  the  absence  of  minute  organisms,  the  decomposition  of  proteins 
does  not  occur  : it  is  consequently  not  spontaneous,  and  therefore  fer- 
mentation cannot  be  considered  as  a process  dependent  on  spontaneous 
decomposition. 

291.  Modern  Theory  of  Fermentation. — The  following  is  a short  state- 
ment of  this  theory.  Maltose,  proteins,  and  other  fermentable  substances 
do  not  decompose  of  themselves,  even  when  subjected  to  favourable  con- 
ditions of  moisture,  warmth,  etc.,  provided  that  fermenting  organisms 
and  their  immediate  products  are  rigorously  excluded.  These,  on  their 
introduction,  thrive  and  multiply  ; taking  the  nourishment  requisite  for 
their  development  from  the  substance  which  is  fermented. 

A special  feature  characteristic  of  fermentation  is  that  the  amount 
of  matter  consumed  and  changed  into  other  compounds  is  excessively 
great,  compared  with  the  size  and  weight  of  the  consuming  organisms  ; 
consequently  a very  few  yeast  globules  decompose  very  many  times  their 
weight  of  sugar,  and  produce  a relatively  large  quantity  of  alcohol  and 
carbon  dioxide.  No  very  clear  reason  has  as  yet  been  given  for  this  char- 
acteristic of  fermentation,  but  one  explanation  is  that  the  decomposition 
of  sugar  furnishes  not  only  material  for  the  growth  and  development 
of  cells,  but  also  the  heat  necessary  for  the  continuance  of  yeast  life. 
It  is  this  double  function  of  sugar  in  fermentation  which  causes  the 
enormous  consumption  of  that  compound.  Fermentation  is  thus  seen 
to  be  like  enzymosis  in  that  a small  quantity  of  the  active  agents 
induces  chemical  change  in  much  larger  quantities  of  material  ; but  fer- 
mentation goes  further,  inasmuch  as  the  quantity  of  fermenting  agent 
itself  also  increases  during  its  continuance. 

In  alcoholic  fermentation  then,  yeast,  in  order  to  obtain  heat  and  nour- 
ishment, attacks  glucose  or  maltose,  and  excretes  or  voids  carbon  dioxide 
gas,  alcohol,  and  small  quantities  of  other  bodies.  The  assimilative  power 
of  yeast  is  limited  to  converting  the  sugar  into  these  substances,  which 
then  become,  so  far  as  it  is  concerned,  waste  products.  Other  organisms 
attack  the  proteins  and  produce  butyric  acid  and  other  compounds.  Each 
particular  organism  has  its  special  products  of  fermentation. 

292.  Experimental  Basis  of  Modern  Theory. — It  is  scarcely  within  the 
scope  of  the  present  Avork  to  trace  step  by  step  the  nature  of  the  various 
researches  which  have  led  to  the  adoption  of  the  theory  just  explained. 
Briefly  stated,  the  first  and  most  important  point  is  that  a liquid  free  from 
ferment  organisms,  or  their  germs  does  not  undergo  fermentation.  In 
proof  of  this  point,  liquids  were  placed  in  flasks  or  tubes,  the  necks  of  Avhicli 
were  tightly  plugged  with  cotton  avooI.  The  liquids  Avere  then  boiled 
for  some  time  ; the  heat  destroyed  any  organisms  that  might  have  been 
present  in  the  liquids  or  the  avooI.  As  the  flasks  cooled,  the  contained 
steam  condensed  ; and  air  forced  its  Avay  through  the  cotton  avooI,  AALich 
acted  as  a filter  and  stopped  off  any  germs  that  might  have  been  floating 
in  the  air.  Hay  and  beef  infusions,  must,  Avort,  urine,  and  other  liquids, 
on  being  treated  in  this  manner,  may  be  kept  for  any  length  of  time  AAuth- 
out  undergoing  fermentation  or  putrefaction.  That  the  resistance  to 
fermentation  is  due  to  the  absence  of  fermenting  organisms,  and  not  to 
the  liquids  having  been  so  changed  by  boiling  as  to  be  unfit  for  fermen- 
tation to  proceed,  is  proved,  by  adding  a small  quantity  of  yeast  or  other 
ferment  to  the  sterile  liquid,  when  fermentation  sets  in  and  proceeds  vigor- 
ously. The  chemical  changes  that  are  produced  depend  on  the  nature  of 


150 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  ferment  that  has  been  added.  Yeast  effects  the  decomposition  of 
sugar  into  alcohol  and  carbon  dioxide,  other  ferments  cause  putrefaction, 
and  result  in  the  typical  bodies  characteristic  of  that  change.  While  these 
actions  are  progressing,  the  ferment  is  found  to  be  developing  and  multi- 
plying. Further,  if  the  ferment  used  be  pure,  one  species  only  of  organism 
is  found  in  the  liquid.  Within  any  possible  limits  of  observation  no  trans- 
formation of  one  ferment  into  another  occurs  : each  belongs  to  a distinct 
and  separate  race  of  organisms.  This  statement  does  not  deny  the  possi- 
bility of  the  modification  of  species  by  means  of  a natural  process  of  evo- 
lution. There  is,  on  the  contrary,  strong  evidence  in  favour  of  the  gradual 
evolution  of  species  in  course  of  time. 

293.  Varieties  of  Fermentation. — ^Among  the  many  changes  included 
under  this  term,  the  following  are  of  importance  in  the  consideration  of 
our  present  subject  : — Alcoholic  fermentation,  resulting  in  the  production 
of  alcohol  and  carbon  dioxide  ; lactic  fermentation,  in  which  sugar  is 
converted  into  lactic  acid  ; acetous  fermentation,  in  which  alcohol  is  trans- 
formed into  acetic  acid  ; viscous  or  ropy  fermentation,  resulting  in  the 
production  of  mannite  and  different  viscous  bodies  ; and  putrefactive 
fermentation,  in  which  butyric  acid  and  a variety  of  offensive  products 
are  formed. 


Alcoholic  Fermentation  and  Yeast. 

294.  The  nature  of  alcoholic  fermentation  has  already  been  described. 
For  the  sake  of  exactness,  Pasteur's  definition  of  it  is  appended.  “ Al- 
coholic fermentation  is  that  which  sugar  undergoes  under  the  infiuence 
of  the  ferment  which  bears  the  name  of  yeast  or  barm."  When  the  word 
“ fermentation  " is  employed  without  any  qualifying  adjective,  alcoholic 
fermentation  is  always  understood. 

295.  Substances  susceptible  of  Alcoholic  Fermentation. — Pre-eminent 
among  these  are  the  glucoses,  which  are  directly  split  up  into  alcohol  and 
carbon  dioxide.  Most  other  sugars  may  also  be  fermented  ; but  usually, 
as  in  the  case  of  cane-sugar,  require  first  to  be  hydrolysed  to  glucose.  As 
already  explained,  this  change  is  effected,  when  yeast  is  added  direct  to 
cane-sugar,  by  the  enzyme,  invertase  ; which  latter  functions  indepen- 
dently of  the  cell  itself,  and  therefore  the  inversion  of  the  sugar  is  separate 
and  distinct  from  fermentation  proper.  Both  diastase  and  invertase 
are  without  action  upon  maltose  ; but  maltose  undergoes  inversion  into 
glucose  before  fermentation  by  the  action  of  maltase. 

Pure  yeast  is  incapable  of  producing  fermentation  in  either  starch 
paste  or  dextrin  ; neither  can  albuminous  bodies,  whether  of  vegetable 
or  animal  origin,  be  fermented. 

296.  Fermentation  viewed  as  a Chemical  Change. — ^The  conversion  of 
glucose  into  alcohol  and  carbon  dioxide  may  be  represented  very  simply 
by  the  equation — 

CeHi^Oe  = 2C2H5HO  -f  2CO2. 

Glucose.  Alcohol.  Carbon  Dioxide. 

Taking  the  action  on  the  glucose  as  the  more  simple  of  the  two,  the 
equation  given  above  does  not,  however,  represent  the  whole  of  the  change, 
for  100  parts  of  glucose  then  would  yield — 

Alcohol  ..  ..  ..  ..  ..  ..  •.  ..51*11 

Carbon  Dioxide  . . . . . . . . . • • . 48*89 


100*00 


FERMENTATION. 


151 


Pasteur  carefully  collected  the  whole  of  the  alcohol  and  carbon  dioxide 
produced  by  fermentation  of  a definite  weight  of  glucose,  and  found  that 
he  only  obtained — 

Alcohol  . . . . . . . . . . ..  48*51  per  cent. 

Carbon  Dioxide  . . . . . . . . ..  46*40  ,, 


100  — 94*91  = 5*09  parts 

of  glucose  not  transformed  into  alcohol  and  carbon  dioxide. 

The  following  bodies  occur  as  subsidiary  products — glycerin,  succinic 
acid  ; propyl,  butyl,  and  amyl  alcohols  ; acetic,  lactic,  and  butyric  acids. 
Of  these,  the  amount  of  glycerin  and  succinic  acid  produced  have  been 
found  to  be — 

Glycerin  . . . . . . . . . . . . 3*00  per  cent. 

Succinic  Acid  ..  ..  ..  ..  ..  1*13  ,, 


4*13 


This,  therefore,  leaves  but  0*96  per  cent,  for  the  various  higher  alcohols, 
and  the  acetic,  lactic,  and  butyric  acids  ; and  also  for  that  portion  of  the 
sugar  that  goes  to  help  to  build  up  fresh  yeast  cells. 

Buchner  and  Meissenheimer  point  out  that  acetic  and  lactic  acids  are 
invariably  produced  in  alcoholic  fermentation,  and  under  conditions  which 
negative  the  possibility  of  the  action  of  bacteria  or  oxidation  by  the  air. 
They  regard  the  lactic  acid  as  an  intermediate  product  between  the  glucose 
and  the  alcohol,  and  suggest  the  following  equation  as  representing  the 
change  which  occurs  : — 


CHO 

I 

CHOH 

I 

CHOH 

I 

CHOH 

I 

CHOH 

I 

CHOH 

Glucose. 


OH 

OH 

COOH 

COOH 

I 

CHOH 

1 

CH.OH 

H ^ 

j 

CH2H  -> 

1 

CH3 

OH 

I 

COOH 

I 

COOH 

OH 

I 

CH.OH 

1 

I 

CH.OH 

1 

H 

H 

1 

CH3 

1 

CH3 

Water, 

4 mols. 

Hypothetic 
Intermediate 
Product  + 

Lactic 

Acid, 

2 mols. 

! H2O. 


CH2OH 

^ + CO2 

CH3 


H"^  CH2OH 

+ CO2 

CH3 

Water,  Alcohol,  Carbon 

2 mols.  2 mols.  Dioxide, 

2 mols. 


Monoyer  proposes  the  following  equation  as  showing  the  production 
of  glycerin  and  succinic  acid  from  glucose — 

4C6H12O6  + 3H2O  = H2C4H4O4  + bCsHsCHOa  + 2CO2  + 0. 

Glucose.  Water.  Succinic  Acid.  Glycerin.  Carbon  Oxygen. 

Dioxide. 

No  free  oxygen  is  however,  detected  in  fermentation  ; any  that  may 
be  produced  during  the  decomposition  is  probably  used  up  by  the  yeast 
ceUs  for  purposes  of  respiration. 

Pasteur  claims  that  the  glycerin  and  succinic  acid,  as  well  as  the  alcohol 
and  carbon  dioxide,  are  normal  products  of  alcoholic  fermentation  ; and 
further,  that  these  bodies  are  produced  from  the  sugar,  and  not  from  the 
ferment.  He  also  shows  that  a portion  of  the  sugar  goes  to  help  to  build 
up  the  yeast  globules.  The  quantities  of  glycerin  and  succinic  acid  pro- 


152 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


duced  are  not  constant,  but  vary  with  the  conditions  under  which  fer- 
mentation proceeds  ; when  the  action  is  slow  the  proportion  of  glycerin 
and  succinic  acid  to  alcohol  is  higher  than  with  brisk  and  active  fermentation. 

Brefeld,  however,  argues  that  glycerin  and  succinic  acid  are  not 
products  of  alcoholic  fermentation  proper,  but  rather  are  pathological 
products  arising  out  of  the  death  of  the  yeast  cells.  The  same  view  is 
advanced  in  a more  modernly  expressed  opinion  that  these  bodies  are 
due  to  the  destructive  metabolism  ^ of  the  cells. 

A small  proportion  of  the  carbohydrate,  amounting  to  about  1 per 
cent.,  is  assimilated  by  the  yeast  and  employed  in  its  constructive  meta- 
bolism, being  transformed  into  cellulose  and  fats. 

Jorgensen  states  that  during  fermentation  by  the  pressed  juice  of  yeast, 
i.e.  by  the  separated  zymase,  glycerin  is  produced  to  the  extent  of  from 
3 to  8 per  cent,  of  the  fermented  sugar,  and  is  derived  from  the  sugar.  On 
the  other  hand,  no  succinic  acid  is  formed.  Acetic  acid  is  produced  in 
minute  quantities,  but  somewhat  more  than  in  the  fermentation  with  the 
living  cell.  This  is  probably  due  to  the  action  of  a special  enzyme.  {Micro- 
organisms and  Fermentation,  Fourth  Edition.) 

297.  Chemical  Composition  of  Yeast. — ^When  yeast  has  been  washed 
carefully  so  as  to  free  it  as  far  as  possible  from  foreign  matters,  and  then 
dried,  it  is  found  to  have,  according  to  Schlossberger,  the  following  com- 
position— 

Surface  Sedimentary 

Yeast.  Yeast. 


Carbon  . . 

Hydrogen 
Nitrogen 
Oxygen  . . 

Ash  (mineral  matter) 


. . 48-7  46-4 

6-4  6-2 

..  11-8  9-5 

. . 30-7  34-5 

. . 2-4  3-4 


1000  1000 


In~addition  to*  the  above  a number  of  other  analyses  might  be  quoted, 
showing  that  yeast  is  a body  of  somewhat  variable  composition  ; mean- 
while attention  is  directed  to  the  fact  that  yeast  collected  from  the  bottom 
of  the  fermenting  liquid  contains  less  nitrogen  and  carbon  than  does  surface 
yeast. 

Various  attempts  have  been  made  to  separate  yeast  into  its  proximate 
principles,  and  estimate  these  : as  a result  it  may  be  stated  that  yeast 
contains  one  or  more  bodies  of  the  protein  type.  There  are  in  addition, 
also  present,  cellulose  and  fatty  matters.  Payen  gives  the  following  as 


the  result  of  an  analysis  of  moisture-free  yeast  : — 

Nitrogenous  Matter  . . . . . . . . • • 62-73 

Cellulose  (envelopes)  . . . . • . - • - • 22-37 

Fatty  Matters  . . . . . . • • • • • • -*10 

Mineral  ,,  . . . . . . • • • • • • 5-80 


Naegeli  states  that  the  proximate  constituents  of  a sample  of  yeast 
examined  by  him  were  as  follows.  The  yeast  was  a sedimentary  one, 
containing  8 per  cent,  of  nitrogen  : — 

Cellulose,  Gum,  and  Cell  Membrane  . . . . 37  per  cent. 

Proteins  . . . . . . . • • • . . 45  ,, 

Peptones  . . . . . . • • • • • • 2 ,, 

Fat  . . . . • • • • • • • • • • 5 5 5 

Extractives  (Leucine,  Cholesterin,  Dextrin, 

Glycerin,  Succinic  Acid)  . . . . . . 4 ,, 


^ For  an  explanation  of  metabolism  refer  to  Chapter  XIII.,  par  415. 


FERMENTATION.  153 

A sample  of  distiller’s  compressed  yeast  examined  by  one  of  the  authors 
gave  the  following  results  on  analysis  : — 


Proteins 

Fat 

Mineral  Matter 

Water 

Cellulose,  etc.  (by  difference) 

. . 12-67 

0-80 
2-05 
. . 73-80 

. . 10-68 

100-00 

The  mineral  matter  of  yeast  is  of  great  importance,  and  has  been  made 
the  subject  of  careful  analysis  by  Mitscherlich  and  others.  The  following 
table  gives  the  composition  of  the  ash  of  surface  and  sedimentary  yeasts 
by  Mitscherlich,  and  of  the  surface  yeast  of  pale  ale  by  Bull — 

Surface  Y.  Sedimentary  Y. 


Phosphoric  Acid,  P2O5 

Mitscherlich. 

. . 53-9  59-4 

Pale  Ale, 

54-7 

Potash,  K2O . . 

. . 39-8 

28-3 

35-2 

Soda,  Na20  . . 

— 

— 

0-5 

Magnesia,  MgO 

6-0 

8-1 

4-1 

Lime,  CaO 

1-0 

4-3 

4-5 

Silica,  Si02  . . 

traces 

— 

— 

Iron  Oxide,  FesOs  . . 

■ — ■ 

— 

0-6 

Sulphuric  Acid,  SO3 

— 

— 

— 

Hydrochloric  Acid,  HCl 

— 

— 

0-1 

Yeast  ash  is  therefore  composed  principally  of  phosphoric  acid  and 
potash  : attention  is  directed  to  the  similarity  in  composition  between 
the  ash  of  yeast  and  that  of  wheat.  The  above  acids  and  bases  probably 
exist  in  combination  as  the  following  salts  : — 


Potassium  Phosphates 

Surf.  Y. 

. . 81-6 

Sed.  Y. 

67-8 

Magnesium  Phosphate,  Mg3(P04)2  • . 

. . 16-8 

22-6 

Calcium  Phosphate,  Ca3(P04)2 

..  2-3 

9-7 

The  potassium  phosphate  must  be  looked  on  as  a mixture  of  the  dihydric 
phosphate,  KH2PO4,  and  the  monohydric  phosphate,  K2HPO4.  The 
former  of  these  phosphates  contain  94  by  weight  of  K2O  to  142  of  P2O5  ; 
the  latter  contains  188  of  K2O  to  142  of  P2O5.  The  weight  of  K2O  in  the 
surface  yeast  ash  is  between  that  required  to  produce  either  of  these  two 
potassium  phosphates.  The  composition  of  the  potassium  phosphate 
of  the  sedimentary  yeast  ash  nearly  agrees  with  the  formula,  KH2PO4. 

298.  Yeast  as  an  Organism. — Viewed  as  an  organism,  yeast  may  be 
said  to  be  a plant  of  an  exceedingly  elementary  structure  ; it  is  in  fact 
one  of  the  simplest  plants  known.  In  very  minute  forms  of  life  it  is  diffi- 
cult to  distinguish  animals  and  vegetables  from  each  other,  for  with  almost 
any  definition  that  may  be  selected,  one  or  two  species  wander  over  the 
border  line.  One  of  the  most  marked  differences  between  the  higher  plants 
and  animals  is,  that  the  former  are  able  to  derive  their  sustenance  from 
inorganic  compounds,  their  carbon  from  carbon  dioxide,  and  their  nitrogen 
from  ammonia.  Animals,  on  the  contrary,  can  make  no  use  of  carbon 
or  nitrogen  for  the  purpose  of  building  up  their  tissues,  unless  these  bodies 
are  presented  to  them  in  the  form  of  organic  compounds.  Hence,  in  the 
economy  of  nature,  it  will  be  found  that  while  plants  live  and  develop,  as 
before  stated,  by  the  assimilation  of  the  elements  of  carbon  dioxide  and 
ammonia,  animals  subsist  either  on  vegetable  substances,  or  on  the  bodies 


154 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  other  animals.  Yeast  is  unable  to  assimilate  carbon  from  inorganic 
sources,  but  being  able  to  derive  its  nitrogenous  nutriment  from  inorganic 
bodies,  is  placed  in  the  vegetable  kingdom.  The  chemical  changes  pro- 
duced during  the  growth  of  the  higher  plants  result  in  the  building  up  of 
complex  compounds  from  very  simple  ones  : in  the  animal,  complex  bodies 
are  required  as  nourishment,  and  are  broken  down  into  simpler  bodies. 
The  complexity  here  referred  to  is  that  which  may  be  measured  by  the 
number  of  atoms  in  the  molecule  of  the  body  ; thus,  water  is  a very  simple 
compound,  while  starch  has  a most  complex  molecular  structure.  The 
chemical  operations  of  plant-life  may  be  summed  up  as  consisting  of  syn- 
thesis ; those  of  animal  existence  as  analysis.  In  order  to  effect  the  syn- 
thesis of  plant  compounds  from  the  substances  at  the  disposal  of  vegetables, 
force  is  required  ; this  they  usually  obtain  in  the  form  of  heat  from  the 
sun.  The  act  of  growth  of  a plant  means,  therefore,  a continual  absorption 
of  heat.  On  the  other  hand,  animals,  in  taking  complex  bodies  and  breaking 
them  down  into  simpler  ones,  liberate  heat  ; consequently,  one  result 
of  animal  life  is  that  heat  is  continuously  being  evolved.  Yeast,  in  this 
particular,  partakes  both  of  the  nature  of  an  animal  as  well  as  a plant. 
Its  nitrogen  may  be  obtained  from  inorganic  sources,  but  is  more  usually 
derived  from  suitable  protein  matter,  such  as  peptones.  On  the  other 
hand,  the  carbon  of  yeast  is  taken  from  sugar  with  the  breaking  down 
of  that  body  into  simpler  compounds,  and  the  consequent  liberation  of 
heat  ; therefore  during  fermentation  the  temperature  of  the  liquid  rises 
considerably.  From  a chemical  standpoint,  yeast  combines  in  itself  the 
vegetable  functions  of  synthesis  with  the  animal  functions  of  analysis. 

299.  Botanic  Position  of  Yeast. — This  organism  belongs  to  the  family 
of  Fungi. 

Fungi. — The  fungi  are  those  plants  which  are  destitute  of  chlorophyll 
(the  ordinary  green  colouring  matter  of  grass,  etc.).  They  reproduce  by 
buds  and  spores. 

Spores. — Spores  are  a variety  of  cell,  and  in  all  fungi  the  spores  are 
similar  in  essential  points  to  the  yeast  cell  ; notwithstanding  that  they 
may  vary  considerably  in  appearance  and  details  of  structure. 

Hyphce. — The  spore,  on  being  sown  in  a suitable  medium  for  its  growth, 
throws  out  a long  delicate  stem  of  tubular  structure,  termed  a “ hypha.'^ 
A group  of  these  hyphse  constitute  the  fungus. 

Mycelium. — One  of  the  best  typical  examples  of  a fungus  is  the  common 
green  mould  found  on  old  boots,  bread,  jam,  etc.  This  has  received  the 
name  Penicillium  glaucum.  On  examining  a specimen  of  such  mould 
from  the  top  of  a pot  of  jam  for  instance,  its  base  is  found  to  consist  of 
an  interlaced  growth  of  hyphse,  forming  a more  or  less  compact  web  or 
skin  on  the  jam.  This  layer  of  intermingled  hyphse  is  termed  the  “ my- 
celium.’’ From  its  upper  surface  a number  of  hyphse  project  into  the  air, 
each  bearing  a quantity  of  very  fine  green  powder,  these  are  termed  “ aerial 
hyphse.”  On  the  lower  surface  again,  other  hyphse  grow  down  root-like 
into  the  liquid,  which  supports  the  mould  ; these  are  the  “ submerged 
hyphse.” 

Conidia. — Some  of  the  aerial  hyphse  terminate  in  short  branches,  each 
of  which  is  divided  into  a series  of  rounded  spores  which  are  only  loosely 
attached  to  the  hyphse,  and  so  may  easily  be  shaken  off  ; these  spores 
are  termed  “ conidia.”  Each  separate  conidium,  if  sown  in  a suitable 
Liquid,  develops  a young  fungus,  which  in  its  turn  rapidly  multiplies. 

Sporangia. — Some  of  the  fungi,  as  for  instance  that  known  as  Mucor 
mucedo,  have  their  hyphae  terminated  in  rounded  heads  ; each  of  these 
is  called  a “ sporangium.” 


FERMENTATION. 


155 


300.  Varieties  of  Yeast. — The  yeast  fungi  constitute  the  genus  Saccha- 
romyces  ; they  are  so  named  because  they  mostly  live  in  saccharine  solu- 
tions, converting  the  sugar  present  into  alcohol.  The  saccliaromyces  have 
no  mycelium,  and  in  common  with  the  other  fungi  reproduce  by  buds 
and  spores.  The  genus  saccliaromyces  comprises  several  species,  a detailed 
description  of^which  will  subsequently  be  given.!! 

301.  Nature  of  Yeast  Cells. — ^The  yeast  organism  consists  of  cells,  mostly 
round,  or  slightly  oval,  from  8 to  9 /x  in  diameter  ; the  cells  may  occur 
either  singly  or  grouped  together  as  colonies.  It  is  impossible  to  obtain 
any  real  knowledge  of  the  physical  structure  of  yeast  without  a careful 
and  systematic  personal  examination  by  the  microscope  : it  has  been 
thought  well,  therefore,  to  arrange  the  following  description  in  such  a 
form  as  to  constitute  a guide  to  actual  yeast  examination. 

1.  Take  either  a little  brewers’  yeast,  or  bakers’  compressed  distillers’ 
yeast,  and  mix  with  some  water  until  a milky  fluid  is  produced.  By  means 
of  a pointed  glass  rod,  take  a small  drop  of  this  fluid  and  place  it  on  a clean 
microscopic  slide,  and  gently  cover  with  a cover-glass.  Arrange  the  micro- 
scope in  a vertical  position,  and  proceed  to  examine  the  yeast  by  means  of  a 
fairly  high  power  (|  objective).  Notice  that  the  yeast  consists  of  cells, 
of  which  measure  a few  by  means  of  the 
eye-piece  micrometer,  and  observe  that 
their  dimensions  agree  with  those  just 
given.  Each  cell  consists  of  a distinct 
wall  or  envelope,  containing,  within,  a 
mass  of  more  or  less  gelatinous  matter 
devoid  of  organic  structure.  The  interior 
substance  is  named  “ protoplasm  ” ; this 
term  being  applied  to  that  ultimate  form 
of  organic  matter  of  which  the  cells  of 
animals  and  plants  are  composed.  The 
protoplasm  of  the  yeast  cell  is  not  homo- 
geneous, but  is  always  more  or  less  dis- 
tinctly granular.  Run  in  magenta  solution 
under  the  cover-glass.  (This  is  readily 
done  by  placing  a drop  of  the  solution  in  contact  with  one  side  of  the 
cover-glass,  and  placing  a strip  of  blotting-paper  on  the  other.)  Notice 
that  the  sac  or  envelope  remains  uncoloured,  while  the  protoplasm  stains 
comparatively  deeply ; the  vacuoles  are  unstained.  One  or  more  circular 
spots  can  usually  be  seen  in  yeast  cells  as  obtained  from  a brewery  ; these 
are  caused  by  the  gelatinous  matter  moving  toward  the  sides  of  the  cell, 
and  leaving  a comparatively  empty  space,  containing  only  watery  cell-sap  ; 
hence  these  spots  are  termed  vacuoles.  A specimen  of  yeast  is  shown  in 
Figure  9. 

2.  Remove  the  slide  from  the  microscope,  and  burst  a few  of  the  cells 
by  placing  some  folds  of  blotting-paper  on  the  cover-glass,  and  then  pressing 
sharply  with  the  end  of  a pencil  or  rounded  glass  rod.  Again  examine 
under  the  microscope,  note  the  empty  sacs  and  the  extruded  protoplasm, 
which  does  not  readily  mix  with  the  water. 

If  practicable,  try  this  experiment  with  yeast  of  various  ages  ; very 
old  yeast  cells  break  more  easily,  and  the  protoplasm  is  more  fluid,  and 
takes  the  colour  more  readily.  By  using  the  magenta  stain  in  a dilute 
form,  old  and  dead  cells  may  be  differentiated  from  those  which  are  healthy 
and  vigorous — the  latter  remain  unstained,  or  take  up  the  stain  very  slightly, 
while  dead  cells  readily  and  quickly  acquire  a magenta  hue. 

3.  Take  six  clean  cover-glasses  and  coat  one  side  of  each  with  a thin 


Fig.  9. — Saccharomyces  Cerevisice. 

a,  a bud  colony  ; b,  two  spore-forming  cells 
(after  Liirssen). 


156  THE  TECHNOLOGY  OF  BREAD-MAKING. 

Iyer  of  yeast,  by  painting  on  the  mixture  of  yeast  and  water  by  means 
of  a earners  hair  brush,  and  set  aside  until  thoroughly  dry.  The  yeast 
adheres  firmly  to  the  glass,  showing  that  the  outside  of  the  cell-walls  is 
mucilaginous  in  character. 

4.  Add  a drop  of  solution  of  iodine  in  potassium  iodide  to  one  of  these 

cyers,  let  it  stand  five  minutes,  and  then  wash  slightly  in  water,  and  mount 
the  cover-glass,  yeast  side  downward,  on  a glass  slide.  The  cell-wall  stains 
slightly,  and  the  protoplasm  becomes  dark  brown;  but  no  blue  colour 
IS  produced  ; starch  therefore  is  absent.  As  the  cell  envelope  is  continuous, 
containing  no  apertures,  the  iodine  solution  must  have  passed  through 
its  substance.  ^ 

5.  Similarly  treat  another  cover  preparation  with  iodine,  and  then, 
without  washing,  add  one  or  two  drops  of  70  per  cent,  sulphuric  acid.  The 
cell-contents  acquire  a deeper  brown  stain,  and  the  cell  walls  become  brown- 
ish yellow,  but  do  not  show  any  blue  colouration. 

The  cellulose  of  the  walls  of  the  cells  of  most  higher  plants  acquire  a 
blue  colour  with  this  treatment,  showing  the  presence  of  a cellulose  allied 
to  that  of  starch,  but  the  cellulose  of  yeast,  and  of  fungi  generally,  is  devoid 
of  this  property. 

6 Treat  the  yeast  on  another  cover-glass  with  solution  of  potash.  Tlie 
protoplasm  is  dissolved,  leaving  nothing  to  be  seen  but  empty  cell-walls. 

7.  Treat  another  cover-glass  preparation  with  a solution  of  osmic  acid. 
Note  that  small,  sharply  defined,  dark  coloured  bodies  are  seen.  Jorgensen 
regards  these  as  cell-nuclei  of  the  same  nature  as  those  generally  observed 
in  the  majority  of  plants  without  this  treatment. 

8.  Break  down  a little  yeast  with  water,  and  focus  under  the  micro- 
scope, so  as  to  observe  distinctly  the  small  bright  granules  of  fat  within 
the  protoplasm  of  the  cells.  Put  a piece  of  blotting-paper  on  one  side 
of  the  cover-glass,  and  run  in  at  the  other  a few  drops  of  ether  from  a fine 
pipette — the  fat  granules  dissolve  and  disappear. 

^ 302.  Life  History. — On  examining  under  a microscope  a sample  of 
skimmed  yeast,  as  obtained  from  the  brewer,  it  is  found  to  consist  either 
of  single  cells,  or  cells  joined  together  in  pairs.  Such  yeast  having  usually 
remained  quiescent  for  some  time,  the  cells  rarely  occur  in  large  groups 
because,  with  standing,  they  tend  to  separate  from  each  other.  The  granu- 
lations in  the  protoplasm,  and  also  the  vacuoles,  should  be  visible.  On 
placing  a very  small  quantity  of  this  yeast  in  a suitable  liquid  for  its  groAvth, 
as  malt  wort,  at  a temperature  of  about  30°  C.  (86°  F.),  the  cells,  which 
at  first  were  somewhat  shrunken  and  filled  throughout  with  granular  matter, 
increase  in  size  from  absorption  of  the  liquid  in  which  they  are  placed.  At 
the  same  time  the  granulations  becomes  less  distinct,  and  the  whole  cell 
assumes  a more  transparent  and  distended  appearance. 

To  observe  this  effect,  mount  a few  cells  on  a microscopic  slide  with 
warm  malt  wort,  and  keep  under  observation  with  the  microscope.  After 
a time  the  round  yeast  cells  become  slightly  elongated  through  the  for- 
mation of  a small  protuberance  at  one  end  ; this  grows  more  marked, 
until  shortly  a neck  is  formed  by  a contraction  of  the  cell  wall.  But  still,' 
careful  examination  shows  that  there  is  a distinct  opening  through  this 
neck,  the  contents  of  the  smaller  portion  being  continuous  with  those 
of  the  cell.  As  the  growth  continues,  the  strangulation  at  the  neck  pro- 
ceeds until  the  cell  wall  completely  shuts  off  the  protuberance,  which  then 
constitutes  a new  or  daughter  cell,  attached  to  the  parent.  This  operation 
is  known  as  “ budding.”  The  one  parent  cell  is  capable  of  giving  off  several 
buds  in  succession  ; but  after  a time  its  reproductive  energy  is  exhausted, 
and  the  cell  breaks  up.  These  daughter  cells  in  their  turn  give  rise  to 


FERMEXTATIOX.  157 

other  cells,  and  so  the  multiplication  of  yeast  globules  proceeds  with  remark- 
able rapidity. 

Pasteur  states  that  on  one  occasion  he  Avatched  two  cells  for  two  hours  ; 
during  that  time  they  had  multiplied  by  budding  into  eight,  including 
the  original  pair  of  cells.  At  this  stage,  buds  of  every  size  may  be  seen 
attached  to  the  parent  cells  ; some  are  so  small  as  to  be  scarcely  visible, 
while  others  are  nearly  as  large  as  the  parents. 

With  the  progress  of  this  grov'th  and  development,  sugar  is  being  decom- 
posed, the  liquid  becomes  alcoholic,  and  its  specific  gravity  diminishes. 
The  brewer  terms  this  change  “ attenuation,”  or  a becoming  thinner. 
Another  reason  for  the  use  of  this  name  is  that  the  liquid  becomes  less 
viscous,  from  the  conversion 
of  the  sirupy  solution  of  mal- 
tose into  the  highly  mobile 
liquid,  alcohol.  Simultaneously 
with  the  production  of  alcohol, 
carbon  dioxide  gas  is  evolved  ; 
this  rapidly  rises  to  the  sur- 
face, and  carries  up  with  it  the 
yeast  cells,  which  float  on  the 
top  of  the  fermenting  wort. 

Yeast  now  skimmed  off  is  found 
to  consist  of  colonies  of  some 
scores  of  cells  linked  together  ; 
the  majority  of  these  are  clear 
and  almost  transparent.  Usu- 
ally in  the  middle  of  each  such 
group,  the  old  or  parent  cell 
can  be  recognised  by  its  darker 
contour  and  comparatively  ex- 
hausted appearance.  As  the 
quantity  of  sugar  in  the  liquid 
becomes  less,  the  fermentation 
slackens,  and  finally  ceases.  If 
the  cells  then  be  again  exam- 
ined, under  the  microscope,  they  will  be  found  to  have  a firmer  outline,  and 
tlieir  contents  will  be  more  granular.  In  what  may  be  termed  old  age 
of  the  yeast  cell,  the  walls  become  abnormally  thick,  and  the  granulations 
very  dense.  The  yeast,  on  being  removed  from  the  fermenting  tun,  is 
usually  set  aside  in  store  vats  ; on  standing,  it  gradually  assumes  the 
appearance  described  as  that  of  the  yeast  used  for  “ pitching  ” or  starting 
tlie  fermentation.  The  quantity  of  yeast  thus  obtained  is  considerably 
in  excess  of  that  first  added  to  the  malt  wort. 

In  the  moist  state,  yeast  decomposes  quickly  ; hence  if  the  store  be 
kept  for  any  length  of  time,  the  cells  rapidly  alter  in  character.  The  walls 
become  soft,  thin,  and  weak,  and  the  interior  protoplasm  changes  from 
its  normal  granular  gelatinous  condition  to  a watery  consistency.  After 
a time,  if  viewed  Avith  a high  poAAer,  a distinct  “ BroAvnian  ” moA^ement 
is  seen  of  particles  suspended  in  the  contents  of  the  cell.  The  particles 
may  A^ery  possibly  consist  of  minute  fragments  of  cellulose  from  the  enve- 
lojies.  After  a time  the  AAalls  also  break  doAAn  and  all  traces  of  the  yeast 
organism  disappear.  The  normal  bodies  produced  by  the  decomposition 
of  nitrogenous  and  protein  bodies  may  noAv  be  detected  in  the  liquid  : 
putrefaction  rapidly  folloAAS,  AA'ith  the  production  of  a most  offensive  odour. 
Such  is  in  broad  outlines  the  life  history  of  a yeast  cell,  AA'hen  soAA'n  under 
normal  conditions  in  malt  AAort. 


Fig.  10. — Saccharomyces  Cerevisice. 

a.  High  Yeast,  at  rest ; b,  High  Yeast,  actively  budding 
c,  Low  Yeast,  at  rest  ; d,  Low  Yeast,  actively  budding. 


158 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

Distillers’  yeast  putrefies  much  more  readily  than  does  that  of  the 
beer  brewer  : the  hops  used  in  the  latter  act  as  an  antiseptic,  and  the  yeast 
putrefies  much  less  rapidly.  Evidence  of  this  is  afforded  in  the  method 
employed  for  the  preparation  of  invertase  from  brewers’  yeast. 

High  yeast  produces  a beer  having  a special  and  characteristic  flavour, 
which  distinguishes  it  at  once  from  beer  brewed  with  low  yeast. 

303.  Influence  of  Temperature  on  Yeast  Growth.— The  temperature 
most  favourable  to  the  growth  of  yeast  is  from  25°  C.  to  35°  C.  (77°  and 
95  F.)  Between  these  points  yeast  flourishes  and  grows  well  ; at  tem- 
peratures lower  than  25°  growth  proceeds,  but  not  so  rapidly.  At  a tem- 
perature of  about  9°  C.  (49*6°  F.),  the  action  of  yeast  is  arrested  ; the 
vitality,  however,  of  the  ceU  is  only  suspended,  not  destroyed,  for  with 
a higher  temperature  it  again  acquires  the  power  of  inducing  fermenta- 
tion. Actual  freezing  does  not  destroy  yeast,  provided  the  cells  do  not 
get  mechanically  ruptured  or  injured.  Above  35°  C.,  the  effect  of  heat 
is  to  weaken  the  action  of  yeast,  until  at  a temperature  of  about  60°  C. 
(140°  F.),  being  that  at  which  protein  principles  begin  to  coagulate,  the 
yeast  is  destroyed.  This  applies  to  moist  yeast.  When  dry,  the  cells 
are  able  to  stand  higher  temperatures  than  when  suffused  with  water  ; 
thus,  dried  yeast  has  been  heated  to  100°  C.  without  destroying  its  vitality. 

Although  a temperature  of  from  25°  to  35°  C.  conduces  to  the  rapid 
growth  of  yeast,  yet  there  are  other  circumstances  which  render  it  ad- 
visable to  conduct  actual  brewing  operations  at  a much  lower  temperature. 
In  English  breweries,  a pitching  temperature  of  about  from  18°  to  19°  C. 
(65°  F.)  is  commonly  employed  : during  the  fermentation  the  heat  rises  to 
from  21°  to  22°  C.  (72°  F.). 

Faulkner  states  that  a tun  of  pale  ale,  containing  200  barrels  of  36 
gallons,  on  being  pitched  with  600  lbs.  of  yeast  at  14-5°  C.  (58*1°  F.)  had 
sufficiently  attenuated  in  46  hours,  during  which  time  the  temperature 
had  risen  to  22-2°  C.  (72°  F.). 

304.  Substances  Requisite  for  the  Nutriment  of  Yeast.— It  has  several 
times  been  stated  that  sugar  is  required  by  yeast  during  its  growth  : as 
yeast  cells  likewise  contain  nitrogenous  matter,  and  also  certain  inorganic 
constituents,  it  is  evident  that  nitrogen  in  some  form,  and  also  the  requisite 
mineral  salts,  must  be  supplied  to  the  growing  yeast.  Summing  these  uji, 
yeast  requires  for  its  growth,  sugar,  nitrogenous  compounds,  and  appro- 
priate inorganic  matter. 

305.  Saccharine  Matters. — These  occupy  the  first  and  paramount  position, 
as^being  absolutely  necessary  for  the  production  of  alcoholic  fermenta- 
tion. Pure  yeast  sown  in  a pure  sugar  solution  causes  it  to  ferment  ; but 
without  the  sugar  neither  alcohol  is  produced,  nor  carbon  dioxide  evolved. 
Malt  wort,  grape  juice  or  “ must,”  and  dough,  all  ferment  on  the  addition 
of  yeast,  because  they  all  contain  sugar.  “ It  is  necessary  indeed  that  sugar 
be  present ; for  if  we  abstracted  by  some  means  or  other  from  the  must  or  dough  all 
the  sugar  contained  in  it,  '[and  also  all  substances  capable,  by  the  addition  of  yeast 
to  flour,  of  being  converted  into  sugar],  without  touching  the  other  constituents, 
the  addition  of  yeast  would  produce  no  gas.  Everything  would  remain  quiet  until 
the  moment  when  signs  of  a more  or  less  advanced  putrefaction  showed  themselves.” 
(Pasteur).  It  should  be  mentioned  that  yeast  is  also  capable  of  inducing 
definite  chernical  changes  in  a few  other  bodies  : among  these  is  malic 
acid,  which  is  broken  up  into  succinic  and  acetic  acids,  carbon  dioxide, 
and_water.  It  is  also  stated  that  yeast  decomposes  glycerin  into  propionic 

Tho  clause  in  brackets,  [ ],  is  inserted  by  the  authors. 


FERMENTATION. 


159 


and  acetic  acids  ; this  change  has  been  denied  by  Roos  and  Brown.  As 
neither  malic  acid  nor  glycerin  (in  the  free  state)  occur  as  constituents 
of  flour,  their  fermentation  lies  altogether  outside  the  scope  of  the  present 
work. 

The  glucoses,  or  sugars  of  the  C6H12O6  group,  are  the  only  sugars  capable 
of  direct  fermentation  ; of  these,  glucose  or  dextrose  is  more  readily  decom- 
posed by  yeast  than  is  fructose.  The  two  being  together  in  the  same  solu- 
tion, the  fructose  remains  unacted  on  until  the  disappearance  of  the  whole  of 
the  glucose.  Certain  other  sugars  are  capable  of  indirect  fermentation  by 
yeast ; among  these  are  cane-sugar,  which  first,  however,  requires  to  be 
hydrolysed  to  glucose  by  the  action  of  the  invertase  or  soluble  diastatic  body 
secreted  by  the  yeast  cell.  As  already  explained,  this  preliminary  diastasis 
can  be  effected  by  yeast  water,  that  is,  water  with  which  yeast  has  been 
shaken  up,  and  then  filtered  in  order  to  remove  the  whole  of  the  yeast  cells ; 
such  yeast  water  is,  of  itself,  incapable  of  setting  up  alcoholic  fermentation. 

Yeast  causes  certain  effects,  of  which  it  is  difficult  to  say  whether  they  are 
absolutely  correlatives  of  vital  acts,  as  an  organism,  or  merely  results  of 
diastasis.  For  practical  purposes,  it  matters  little  to  which  of  these  two 
classes  of  chemical  action  any  specifice  change  produced  by  yeast  belongs  ; 
in  such  cases  it  is  the  action  of  yeast,  as  a whole,  that  is  of  importance. 

Sugar  of  milk  is  incapable  of  fermentation  by  yeast.  Yeast  alone  is  also 
unable  to  ferment  either  starch  paste  or  dextrin  : these  bodies  require  some 
more  powerful  agent  for  their  diastasis,  such  as  malt  extract.  As  mentioned 
in  Chapter  VIII.,  yeast,  indirectly  through  its  action  on  the  proteins  of  barley 
or  wheaten  flour,  transforms  starch  paste  into  dextrin  and  maltose,  after 
which  the  yeast  induces  fermentation.  Consequently,  the  two,  yeast  and 
proteins,  in  conjunction,  are  capable  of  effecting  changes  which  neither  can 
separately  produce. 

It  almost  goes  without  saying  that  water  is  necessary  for  the  develop- 
ment of  yeast,  so  requisite  is  it  that  saccharine  solutions  containing  over  35 
per  cent,  of  sugar  are  incapable  of  fermentation.  Such  a solution,  by  out- 
ward osmose  through  the  cell  wall,  deprives  the  yeast  of  its  normal  proportion 
of  water  as  a constituent. 

306.  Nitrogenous  Nutriment. — ^Yeast  is  capable  of  utilising,  during  its 
growth,  the  nitrogen  of  ammoniacal  salts  (but  not  that  of  the  acid  radical  of 
nitrates)  ; thus,  a solution  of  pure  sugar,  mixed  with  either  ammonium  tar- 
trate or  nitrate,  and  certain  non-nitrogenous  inorganic  salts,  permits  a 
healthy  development  of  yeast.  With  the  multiplication  of  the  yeast  cells, 
the  amount  of  protein  matters  present  increases  ; therefore,  by  the  action  of 
yeast,  the  ammonium  compounds  are  transformed  into  protein  bodies.  Al- 
though yeast  thus  acts  on  ammonium  salts,  organic  nitrogenous  compounds 
form  a more  suitable  nutriment ; among  such  substances,  the  soluble  pro- 
teins of  yeast  itself  are  especially  seized  on  by  yeast.  Consequently,  always 
supposing  the  presence  of  the  inorganic  salts  required  by  yeast,  yeast  water 
and  sugar  form  an  admirable  medium  for  its  growth  and  development ; so, 
too,  do  natural  saccharine  juices,  as  “ must,''  the  juice  of  apples,  pears,  etc. 
In  addition  to  these,  malt  infusion  must  be  mentioned. 

Albumin,  whether  from  the  white  of  egg  or  vegetable  albumin,  is  entirely 
unfit  for  the  nourishment  of  yeast.  This  fact  is  stated  with  force  by  Pasteur, 
whose  opinion  is  confirmed  by  that  of  Mayer,  who  ascribes  the  inactivity  of 
albumin,  casein,  and  other  similar  bodies,  to  their  highly  colloid  nature. 
The  solution  molecules  of  soluble  proteins  of  malt  have  such  an  appreciable 
volume,  that  filtration  of  the  solution  through  a thin  porous  earthenware 
diaphragm  under  slight  pressure  is  sufficient  to  prevent  these  bodies  from 
passing  through  into  the  filtrate  (Brown  and  Heron).  It  may  then  be  readily 


160 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


understood  that  yeast  cell  walls  are  impermeable  to  protein  bodies.  The- 
compounds  produced  by  digestion  of  albumin  and  its  congeners,  the  peptones, 
are  much  more  diffusible,  and  are  eminently  suited  for  affording  the  requisite 
nitrogenous  nutriment  to  yeast.  Pepsin  itself  forms  an  admirable  yeast 
food.  Schiitzenberger  considers  it  probable  that  must,  malt  wort,  and  yeast 
M ater  owe  their  power  of  nourishing  the  cells  of  yeast,  not  to  the  protein 
bodies,  but  to  certain  of  their  constituents  that  are  analogous  to  the  peptones, 
and  M'hich  have  the  property  by  osmose  of  passing  through  the  cell  v’alls. 

307.  Mineral  Matters  necessary  for  the  Growth  of  Yeast. — ^For  his  experi- 
ments on  yeast,  Pasteur  used  yeast  ash  as  the  source  of  his  mineral  matter. 
It  is  obvious  that  this  substance  may  be  replaced  by  an  artificial  mixture  of 
the  salts  contained  therein.  A reference  to  Mitscherlich's  analyses  of  yeast 
ash  shows  that  the  principal  ingredient  is  potassium  phosphate  ; together 
with  this,  there  is  magnesium  phosphate  and  small  quantities  of  phosphate 
of  calcium.  Pasteur  finds,  v hen  an  unw  eighable  quantity  of  yeast  is  sown 
in  a solution  of  pure  sugar  and  ammonium  tartrate,  that  development  of  cells 
and  fermentation  do  not  take  place  ; the  addition  of  yeast  ash  enables  both 
to  occur.  Mayer  endeavoured  further  to  ascertain  what  salts  are,  in  par- 
ticular, necessary  among  those  present  in  the  ash.  Potassium  phosphate  is 
absolutely  indispensable  ; neither  sodium  nor  calcium  phosphates  are  com- 
petent to  replace  it.  Magnesia  is  also  of  great  value,  if  not  indispensable,  to 
the  development  of  yeast  ; this  base  may  be  supplied  either  as  sulphate  or 
phosphate.  Lime  seems  not  to  be  absolutely  necessary  to  yeast  growth. 

308.  Insufficiency  of  either  Sugar  or  Nitrogenous  Matter  only  for  the 
Nutriment  of  Yeast. — ^Yeast  is  incapable  of  healthy  development  in  solutions 
of  sugar  alone.  A limited  growth  occurs  when  the  quantity  of  yeast  added 
is  considerable,  because,  by  a species  of  cannibalism,  the  healthier  and 
stronger  cells  survive  and  develop  to  some  extent  by  feeding  on  the  nitro- 
genous and  mineral  matters  obtained  from  the  others.  Necessarily,  such 
grovTli  must  soon  stop.  Yeast  was  stated  by  Pasteur  to  multiply  in  a nitro- 
genous liquid,  such  as  yeast  water,  “ even  when  there  was  not  a trace  of  sugar 
present,  provided  always  that  atmospheric  oxygen  is  present  in  large  quan- 
tities.’' Yeast  finds  air  to  be  under  these  conditions  an  absolute  necessity. 
Without  it  no  development  proceeds,  nor  is  there  any  but  the  slightest  trace 
of  alcohol  found  ; carbon  dioxide  gas  is  evolved,  being  formed  by  direct 
carbonisation  of  oxygen  derived  from  the  air.  But,  for  this  change,  it  must 
be  remembered  that  air  is  a necessity.  Assuming  the  correctness  of  Pas- 
teur’s viev'S  as  to  the  growth  of  yeast  by  the  assimilation  of  atmospheric 
oxygen,  and  expiration  of  carbon  dioxide,  it  is  necessary  to  remember  that 
the  conversion  of  oxygen  into  carbon  dioxide  gas  results  in  no  change  of 
volume  ; this  is  clearly  seen  by  reference  to  the  molecular  equation — 

C + O2  = CO2. 

Carbon.  Oxygen.  Carbon  Dioxide. 

Under  ordinary  conditions  of  fermentation,  albumin  does  not  evolve  alcohol 
or  carbon  dioxide  gas.  Neither  does  pepsin  when  similarly  treated,  although 
tills  body  is  v eil  adapted  as  a nitrogenous  food  for  yeast.  Albumin  is  also 
unacted  on  when  its  solution  is  first  of  all  mixed  'with  a 2J  per  cent,  solution 
of  sodium  chloride. 

309.  Behaviour  of  Free  Oxygen  on  Yeast. — ^As  stated  in  the  preceding 
])aragraph,  Pasteur  regarded  atmospheric  oxygen  as  capable  of  acting  as  a 
substitute  for  sugar  in  the  nutriment  of  yeast,  and  accordingly  he  examined 
very  carefully  the  general  behaviour  of  free  oxygen  and  yeast  to  each  otlier. 
In  consequence,  he  developed  the  follo'wing  theory  of  fermentation,  which  for 
some  time  was  generally  accepted. 


FERMENTATION. 


161 


Pasteur  states,  as  a result  of  experiment,  that  yeast  grows  better  in 
shallow  than  in  deep  vessels.  As  a result  of  some  determinations  made,  in 
which  one  sample  of  yeast  and  a saccharme  solution  were  kept  in  an  air-free 
flask,  and  another  in  a shallow  vessel,  by  which  it  was  freely  exposed  to  the 
atmosphere,  he  finds  that  the  proportion  of  yeast  produced  to  the  sugar  con- 
sumed was  much  greater  in  the  latter  than  in  the  former  instance.  By  dint 
of  most  careful  experiment  he  further  finds,  while  a fermentable  liquid  may 
be  made  to  ferment  out  of  contact  with  air,  yet  in  order  that  it  shall  do  so 
it  is  essential  that  young  and  vigorous  yeast  cells  shall  be  employed.  Witli 
older  yeast  the  fermentation  proceeds  more  slowly,  and  with  the  production 
of  mal-shaped  cells,  while  a yeast  still  older  is  absolutely  incapable  of  repro- 
duction in  a liquid  containing  no  free  oxygen.  This  is  not  due  to  the  yeast 
being  dead,  for  on  aerating  the  liquid,  either  with  atmospheric  air  or  oxygen, 
fermentation  proceeds  apace.  Pasteur  therefore  concluded  that  under 
favourable  circumstances  yeast  functions  as  a fungus  ; that  is,  it  lives  by 
direct  absorption  of  oxygen  from  the  air,  and  the  return  of  carbon  dioxide 
gas.  He  consequently  assumed  the  following  relationship  between  its  life 
in  free  oxygen  and  its  life  when  submerged  in  a sugar  solution — Let  some  yeast 
be  sown  in  a sample  of  malt  wort,  containing  as  much  oxygen  as  it  can  possi- 
bly dissolve  ; the  yeast  starts  active  growth,  and  rapidly  removes  all  the  free 
oxygen  from  the  liquid,  after  which  it  commences  to  attack  the  sugar.  Dur- 
ing this  time,  yeast  will  be  living  not  as  a ferment  but  as  a fungus,  namely,  by 
direct  absorption  of  oxygen.  Could  each  yeast  cell  be  supplied  with  all  the 
oxygen  it  requires  in  the  free  form,  it  is  probable  that  it  would  not  exert  the 
slightest  fermentative  action  ; it  would,  at  the  same  time,  grow  and  reproduce 
active  healthy  cells  with  great  rapidity.  As  soon  as  the  whole  of  the  air  is 
exhausted,  the  yeast  attacks  the  sugar,  and  obtains  its  oxygen  by  the  decom- 
position of  that  compound,  and  ordinary  fermentation  proceeds.  Conse- 
quently, yeast  must  be  viewed  as  being  capable  of  two  distinct  modes  of 
existence,  in  free  oxygen  as  a fungus  ; when  submerged  in  a saccharine  solu- 
tion, as  a ferment.  Of  the  two  the  fungus  life  is  the  easiest ; that  is,  yeast 
can  perform  its  vital  functions  more  readily  when  it  obtains  its  oxygen  in  the 
free  state  than  when  it  has  for  that  purpose  to  effect  the  decomposition  of 
large  quantities  of  sugar.  If  yeast  be  grown  continuously  in  saccharine 
solutions,  under  conditions  which  result  in  the  rigid  exclusion  of  air,  fermen- 
tation becomes  more  and  more  sluggish  : the  conditions  of  life  are  in  faet 
more  severe  than  the  yeast  can  stand,  the  struggle  for  existence  is  too  acute, 
and  its  vitality  succumbs.  But  if  a sample  of  fermenting  wort  be  taken  at 
a time  when,  although  the  sugar  is  far  from  exhausted,  the  fermentation  has 
become  sluggish,  and  then  thoroughly  aerated  by  some  means  which  shall 
bring  it  into  full  contact  with  air,  a remarkable  change  ensues.  At  first  the 
fermentation  slackens,  but  the  rate  of  growth  of  yeast  increases  ; this  is  due 
to  its  living  as  a fungus  on  the  dissolved  free  oxygen.  During  this  time  it 
exerts  little  action  as  a ferment,  but  grows  and  accumulates  vital  energy. 
After  a while,  the  fermentation  proceeds  much  more  vigorously  than  before 
the  aeration  ; this  is  a necessary  result  of  the  renewed  energy  and  vitality 
of  the  yeast  cells. 

That  oxygen  is  capable  of  acting  in  some  way  as  a stimulant  to  fermenta- 
tion was  known  to  brewers  long  before  the  announcement  of  this  theory  by 
Pasteur,  as  they  had  found  that  by  “ rousing  (stirring)  tuns  of  wort  that 
Avere  fermenting  sluggishly,  the  fermentation  was  invigorated.  The  agita- 
tion following  from  this  rousing  aerated  the  wort. 

To  borrow  his  own  words,  Pasteur  summed  up  his  theory  of  fermentation 
in  the  following  terms  : — “ Fermentation  by  yeast  is  the  direct  consequence 
of  the  processes  of  nutrition,  assimilation,  and  life,  when  these  are  carriep 
on  without  the  agency  of  free  oxygen.  . . . Fermentation  by  means  of  yeast 

M 


162 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


appears,  therefore,  to  be  essentially  connected  with  the  property  possessed 
by  this  minute  cellular  plant  of  performing  its  respiratory  functions,  some- 
how or  other,  with  oxygen  existing  combined  in  sugar.  Its  fermentative 
power  varies  considerably  between  two  limits,  fixed  by  the  greatest  and  least 
possible  access  to  free  oxygen  which  the  plant  has  in  the  process  of  nutrition. 
If  we  supply  it  with  a sufficient  quantity  of  free  oxygen  for  the  necessities 
of  life,  nutrition,  and  respiratory  combustions,  in  other  words,  if  we  cause  it  to 
live  after  the  manner  of  a mould,  properly  so  called,  it  ceases  to  be  a ferment ; 
that  is,  the  ratio  between  the  weight  of  the  plant  developed  and  that  of  the 
sugar  decomposed,  which  forms  its  principal  food,  is  similar  in  amount  to 
that  in  the  case  of  fungi.  On  the  other  hand,  if  we  deprive  the  yeast  of  air 
entirely,  or  cause  it  to  develop  in  a saccharine  medium  deprived  of  free  oxygen, 
it  will  multiply  just  as  if  air  were  present,  although  with  less  activity,  and 
under  these  circumstances  its  fermentative  character  will  be  most  marked  ; 
under  these  circumstances,  moreover,  we  shall  find  the  greatest  disproportion, 
all  other  conditions  being  the  same,  between  the  weight  of  yeast  formed  and 
the  weight  of  sugar  decomposed.  Lastly,  if  free  oxygen  occur  in  varying 
quantities,  the  ferment  power  of  the  yeast  may  pass  through  all  the  degrees 
comprehended  between  the  two  extreme  limits  of  which  we  have  spoken.” 
According  to  this  view,  fermentation  is  a starvation  phenomenon,  brought 
about  by  the  want  of  free  oxygen  during  the  life  of  yeast  cells  in  a fermentable 
liquid. 

310.  Brown  on  Influence  of  Oxygen  on  Fermentation. — In  1892,  Adrian 
J.  Brown  contributed  an  important  paper  on  this  subject  to  the  Journal  of 
the  Chemical  Society,  which  paper  necessitates  a reconsideration  of  the  theory 
of  fermentation.  In  his  experiments.  Brown  employed  the  method  of  count- 
ing the  yeast  cells  in  his  various  solutions,  by  means  of  the  hsematimeter, 
instead  of  weighing  the  yeast,  as  had  been  done  by  Pasteur  in  his  various 
researches.  This  method  of  working  has  the  advantage  that  the  results  are 
capable  of  being  referred  to  the  amount  of  effect  being  produced  by  the  action 
of  an  unit  cell. 

Brownes  first  conclusions  were  that  “ when  any  fermentable  nutritive 
solution,  such  as  malt  wort,  or  a solution  of  dextrose  in  yeast  water,  is  inocu- 
lated with  a high  fermentation  yeast,  and  kept  at  a temperature  favourable 
to  yeast  growth,  the  cells  reproduce  themselves  rapidly  for  a time,  and  then 
their  reproduction  ceases,  and  that  the  fermentation  of  the  solution  may  still 
be  carried  on  by  the  continued  life  of  the  cells  already  formed.”  Further,  he 
found  that  with  the  same  liquid,  under  the  same  conditions,  the  cells  increase 
to  about  the  same  maximum,  no  matter  how  the  number  of  cells  introduced 
to  start  the  fermentation  may  vary.  In  support  of  this  view,  the  following 
experiment  is  quoted — Two  flasks,  A and  B,  were  taken,  and  in  each  150 
c.c.  of  the  same  malt  wort  was  placed,  and  then  a different  amount  of  the 
same  yeast  added  to  each.  The  contents  of  the  flasks  were  throughly  agi- 
tated, and  the  cells  counted  by  the  haematimeter.  (The  standard  volume  of 
the  instrument  employed  was  4000  of  a cubic  millimetre,  called  hereafter 
“Standard  Volume.”)  The  flasks  A and  B contained  respectively  0*93 
and  7*44  cells  per  standard  volume.  The  flasks  were  kept  at  25°  C.  until 
fermentation  had  completely  ceased,  when  the  cells  were  again  counted.  In 
flask  A the  number  of  cells  per  standard  volume  had  increased  from  0'93  to' 
25*24  “ whereas  in  flask  B the  increase  was  from  7*44  to  27*08.  The  rate 
of  increase  differed  widely,  but  the  ultimate  number  of  cells  produced  was 
approximately  tlie  same.  From  these  and  a number  of  other  similar  experi- 
ments, the  conclusion  is  drawn  that  in  such  fermentations  the  number  of 
3^east  cells  increases  to  some  fixed  maximum,  irrespective  of  the  number 
originally  added  to  induce  fermentation. 


FERMENTATION. 


163 


The  next  point  was  to  experiment  by  adding  more  cells  than  this  maxi- 
mum number,  two  similar  flasks  of  malt  wort  were  respectively  seeded  with 
6*0  and  70*8  cells  of  yeast  per  standard  volume.  Fermentation  was  allowed 
to  proceed,  and,  at  its  close,  in  No.  1 flask  the  cells  had  increased  from  6*0 
to  24*9,  while  in  No.  2 they  had  decreased  from  70*8  to  68*2  cells.  In 
this  experiment  24*9  cells  may  be  regarded  as  the  maximum  number 
that  the  wort  used  would  grow,  consequently  with  No.  2 flask  there  is 
no  increase.  Brown  regards  the  actual  diminution  as  due  to  the  death 
and  disintegration  of  some  of  the  cells.  In  the  second  flask  as  well  as 
the  first,  fermentation  proceeded  with  great  rapidity.  Other  experiments 
made  yielded  the  same  results  ; therefore,  if  a nutritive  liquid  be  seeded  with 
a considerably  larger  number  of  yeast  cells  than  the  maximum  number  it  is 
capable  of  producing  by  reproduction,  fermentation  proceeds,  and  a method  is 
afforded  of  studying  fermentation  without  multiplication  of  yeast  cells. 
Having  a constant  quantity  of  yeast,  throughout  the  experiment,  evidently 
eliminates  many  disturbing  factors  present  when  the  quantity  of  yeast  is 
variable. 

Brown  in  the  first  place  applied  this  method  to  the  investigation  of  the 
action  of  oxygen  on  yeast.  A malt  wort  of  1065  sp.  gr.  was  taken,  and  yeast 
added  to  the  extent  of  85  cells  per  standard  volume.  120  c.c.  of  this  solution 
were  poured  into  a flask.  A,  so  as  to  nearly  fill  it ; its  mouth  was  then  stopped 
in  such  a manner  as  to  permit  the  escape  of  carbon  dioxide  gas,  but  to  prevent 
air  gaining  access  to  the  solution.  120  c.c.  of  the  same  solution  were  also 
placed  in  another  flask,  B,  of  about  1500  c.c.  capacity,so  that  it  simply  formed 
a thin  layer  on  the  bottom  ; this  flask  was  so  arranged  as  to  permit  a current 
of  air  being  drawn  through  the  liquid.  Both  flasks  were  thus  similar,  ex- 
cept that  from  the  one  air  was  excluded,  while  the  contents  of  the  other  were 
subjected  to  abundant  aeration.  The  fermentation  was  conducted  at  19°, 
and,  after  the  end  of  three  hours,  arrested  by  the  addition  of  salicylic  acid. 
The  liquids  were  distilled,  and  the  amount  of  alcohol  produced  estimated 
from  the  specific  gravity  of  the  distillate.  In  A,  flask,  without  aeration, 
3*35  grams  of  alcohol  had  been  formed  ; while  in  B,  through  which  a continu- 
ous current  of  air  had  been  drawn,  the  alcohol  amounted  to  3*56  grams.  The 
number  of  yeast  cells  remained  unaltered  at  the  close  of  the  experiment,  but 
slight  attempts  at  abortive  budding  were  observable,  particularly  in  the 
aerated  flask.  Another  experiment  was  tried,  in  which  the  fermentable 
medium  was  a solution  of  glucose  in  yeast-water,  which  was  seeded  with  90 
cells  per  standard  volume.  At  the  end  of  three  hours,  fermentation  was 
arrested,  and  the  residual  sugar  in  the  solutions  determined  polarimetrically 
In  A (unaerated)  1 *96  grams  of  glucose  had  been  fermented  ; while  in  B 
(aerated)  the  quantity  of  fermented  glucose  was  2*32  grams.  In  neither  case 
was  there  any  sign  of  budding  or  enlargement  of  the  cells. 

In  order  to  meet  the  objection  that  the  mechanical  effect  of  aeration  might 
stimulate  the  action  of  the  cells  in  the  B flasks,  the  following  pairs  of  experi- 
ments were  made  in  which  the  A flasks  were  subjected  to  the  action  of  currents 
of  carbon  dioxide  and  hydrogen  respectively,  and  at  about  the  same  rates  as 
the  air  through  the  B flasks.  The  following  were  the  results  : — 

“ A ''  flask,  with  carbon  dioxide  passed,  3-99  grams  of  glucose  fermented. 
Companion  B flask,  with  air  passed,  4*28  ,,  ,,  ,, 

“ A ” flask,  with  hydrogen  passed,  2*26  ,,  ,,  ,, 

Companion  B flask,  with  air  passed,  2*45  ,,  ,,  ,, 

In  every  case  the  most  work  is  done  in  the  presence  of  oxygen. 

In  all  the  preceding  experiments,  as  the  consequence  of  the  employment 
of  large  quantities  of  yeast,  fermentation  proceeded  very  rapidly  ; in  order 
to  watch  the  results  under  slower  conditions,  experiments  were  made  with 


164 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


fermentation  at  a low  temperature,  7°  C.  (44*6°  F.),  and  were  continued  for 
24  hours.  Through  A flask  hydrogen  had  been  passed,  and  4*882  grams  of 
glucose  had  been  fermented  ; while  in  B flask,  through  which  air  had  been 
passed,  the  quantity  was  5*289  grams.  During  the  24  hours  190  litres  of  air 
had  been  passed  through  B flask.  In  none  of  the  preceding  experiments  was 
there  any  multiplication  of  yeast. 

These  results  are  in  striking  contradiction  to  the  views  of  Pasteur,  who 
affirms  that  in  the  presence  of  excess  of  oxygen  fermentation  practically 
ceases.  Brown,  on  the  contrary,  finds  uniformly  that  in  the  presence  of  oxygen, 
fermentation  is  more  vigorous  than  in  its  absence. 

As  Pasteur’s  results  were  obtained  by  weighing  yeast,  Brown  in  one  ex- 
periment weighed  as  well  as  counted  his  yeast.  At  the  commencement 
there  were  in  each  flask  87*6  cells  per  standard  volume,  and  in  100  c.c.  1*903 
grams  of  Altered,  washed,  and  dried  yeast.  Fermentation  resulted  in  the 
destruction  of  6*20  grams  of  glucose  in  the  hydrogen  flask,  and  7*38  grams  in 
the  air  flask.  No  increase  in  the  number  of  cells  had  occurred,  but  the  weights 
of  yeast,  treated  as  before,  were  respectively  from  hydrogen  flask  2*130 
grams,  and  air  flask  2*060  grams.  In  both  cases  there  is  a slight  increase  in 
weight,  due  probably  to  assimilation  by  each  individual  cell,  but  in  both 
cases  at  the  flnish  of  the  fermentation  we  have  almost  exactly  the  same 
weight  of  yeast,  as  well  as  the  same  number  of  cells.  Hence  equal  amounts 
of  yeast,  whether  determined  by  weighing  or  counting,  ferment  rather  more 
sugar  when  supplied  with  air  than  when  deprived  of  it. 

Another  important  experiment  proceeded  on  different  lines.  The  object 
was  to  determine  the  rate  of  multiplication  of  cells,  and,  at  the  same  time,, 
the  rapidity  of  fermentation.  Six  similar  flasks  of  glucose  in  yeast  water 
were  taken,  and  each  seeded  with  0*65  yeast  cells  per  standard  volume.  All 
were  allowed  to  ferment  under  similar  conditions.  At  intervals,  one  of  the 
flasks  was  taken  and  the  number  of  yeast  cells  found,  and  the  quantity  o£ 
alcohol  produced  determined,  with  the  following  results  : — 


1 

A. 

B. 

C. 

D. 

E. 

F. 

Total 

Grams  of 

Proportion  , 

i 

Mean 

grams  of 

Alcohol 

of  grams 

1 

Number 

number  of 

Alcohol 

found  in 

of  Alcohol 

Interval 

Time  of  Commence- 

of Cells 

Cells  ' 

found  in 

each 

per  100  c.c. 

of  time  in 

ment  of  Experiment, 

found  in 

present 

each 

interval  of 

to  a 

each 

and  .subsequent 

eaeh 

during 

Experiment 

Time  in 

Single  Cell 

Experiment 

Ueterminations  in 

Experi- 

each 

in  100  c.c. 

100  c.c.  of 

in  each 

in  Hours. 

Separate  Flasks. 

ment. 

interval 

of  the 

the 

interval  of 

of  Time. 

Liquid. 

Liquid. 

Time. 

1 

Jan.  9,  11  p.m. 

0-65 

_ 



I 

,,  10,  11  a.m. 

4-87 

2-76 

0-654 

0-654 

0-237 

12 

,,  10,11p.m. 

1203 

8-45 

1-933 

1-279 

0-151 

1 12 

,,  11,11  a.m. 

15-38 

13-70 

2-975 

1-042 

0-076 

12 

,,  12,  1 1 a.m. 

15-88 

15-63 

4-217 

1-232 

0-083 

I 24 

„ 13,11a.m. 

15-80 

15-83 

6-187 

1-950 

0-123 

' 24 

It  will  be  noticed  tliat  tlie  number  of  cells  increases  rapidly  in  the  earlier 
stages  of  fermentation,  and  that  also  the  proportion  of  alcohol  produced  by 
each  single  cell  is  greatest  during  the  first  twelve  hours.  This  is  contrary  tO' 
general  views  that  fermentation  is  slower  during  the  more  rapid  multiplica- 
tion stage  of  the  development  of  yeast,  an  effect  which  was  supposed  to  be  a 
result  of  oxygen  in  the  liquid,  which,  while  aiding  the  reproduction  of  the- 


FERMENTATION.  165 

cells,  at  the  same  time  limited  their  fermentative  power.  Brown’s  experi- 
ments contradict  this  theory. 

In  a further  paper  communicated  to  the  Chemical  Society  in  1894,  A.  J. 
Brown  devotes  himself  to  a critical  examination  of  Pasteur’s  theory  ; of 
Avhich  criticism  the  following  is  a brief  outline  : — Pasteur,  as  previously  ex- 
plained, compared  the  fermentative  power  of  yeast  cells  under  varying  con- 
ditions of  aeration,  and  arrived  at  the  conclusion  that  when  aeration  is  per- 
fect, fermentative  power  ceases,  and  when  a oration  is  reduced,  fermentative 
power  increases.  The  type  of  experiment  used  for  this  purpose  was  that  of 
determining,  under  varying  conditions  of  aeration,  the  proportion  of  the 
weight  of  the  yeast  formed  to  the  weight  of  sugar  fermented.  This  ratio  of 
yeast  to  sugar  is,  Pasteur  considers,  an  expression  of  fermentative  power. 
If,  as  Pasteur  argued,  the  amount  of  yeast  formed  during  fermentation  were 
in  direct  proportion  to  the  sugar  fermented,  the  ratio  of  yeast  to  sugar  would 
remain  constant,  however  much  or  little  sugar  were  available.  Brown  con- 
tends that  his  experiments  show  conclusively  that  such  is  not  the  case,  there 
being  no  direct  proportion  between  weight  of  yeast  formed  and  sugar  fer- 
mented. In  order  to  show  that  the  total  fermentative  power  of  yeast  has 
not  been  measured  in  Pasteur’s  experiments,  a fermentation  was  carried  on 
under  aerobic  conditions,  until  the  sugar  originally  present  was  decomposed. 
Afterwards,  using  the  principle  of  overcrowding  as  a means  of  preventing 
reproduction,  the  crowded  cells  were  fed  with  more  sugar.  Feeding  was 
carried  on  at  intervals  until  three  times  the  original  weight  of  sugar  had  been 
thus  fermented,  but  no  increase  in  the  weight  of  yeast  had  occurred.  In 
Brown’s  opinion,  Pasteur’s  apparent  deficiency  in  fermentative  power  was 
due  to  the  employment  of  a limited  amount  of  sugar  in  the  experiment. 
Brown  objects  to  Pasteur’s  aerobic  experiments  in  shallow  dishes,  because 
they  were  allowed  to  continue  but  a limited  time,  and  therefore  a time  factor 
is  introduced  : further,  cane-sugar  was  used  as  the  fermentable  material, 
and  consequently  the  results  were  complicated  by  the  hydrolytic  functions  of 
the  yeast  having  to  precede  fermentation.  Pasteur’s  measure  of  fermentative 
power  in  the  experiments  referred  to  is  an  expression  of  the  action  of  the 
inversion  and  fermentative  functions  in  a limited  time.  Brown  concludes  by 
submitting,  in  place  of  Pasteur’s  theory  that  fermentation  is  “ life  without 
air,”  the  hypothesis  that  “ yeast  cells  can  use  oxygen  in  the  manner  of  ordinary 
aerobic  fungi,  and  probably  require  it  for  the  full  completion  of  their  life- 
history  ; but  the  exhibition  of  their  fermentative  functions  is  independent  of  their 
environment  with  regard  to  free  oxygen.  Nothing  in  the  results  of  any  of 
Pasteur’s  experiments  are  contradictory  to  such  an  hypothesis. 

311.  Buchner’s  Views  on  the  Action  of  Oxygen. — ^Mention  has  already 
been  made  of  Buchner’s  researches  on  zymase  as  the  agent  through  which 
yeast  effects  alcoholic  fermentation.  That  investigator,  together  with  Rapp, 
pointed  out  in  1898  that  Pasteur’s  views  of  fermentation  were  biologically 
■correct,  inasmuch  as  yeast  has  acquired  the  power  of  acquiring  its  oxygen  by 
means  of  fermentation  instead  of  by  the  more  usual  course  of  the  direct 
assimilation  of  oxygen.  They  show  further  that  oxygen  stimulates  the 
multiplication  of  yeast  cells.  So  thoroughly,  however,  has  yeast  acquired 
the  fermentation  habit,  that  even  in  the  presence  of  oxygen,  yeast  is  far 
more  active  as  a fermentative  agent,  than  as  a mere  respiratory  organism. 

312.  Mal-Nutrition  of  Yeast. — ^When  yeast  is  deprived  of  a normal 
proportion  of  each  of  the  necessary  constituents  for  its  healthy  life,  the  vital- 
ity of  the  cells  is  thereby  lessened.  One  result  of  this  is  that  the  cells  tend 
to  assume  abnormal  forms.  Thus,  in  the  case  of  prolonged  growth,  without 
access  of  free  oxygen,  yeast  cells  elongate,  and  at  times  are  observed  to 


166 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


be  several  times  as  long  as  broad  (sausage-shaped).  The  same  peculiarity  of 
outline  may  be  noticed  in  yeast  that  has  been  grown  in  sweetened  water. 
The  reason  may  be  that,  with  a deficient  supply  of  nutriment,  each  cell 
stretches  itself  out,  as  it  were,  in  order  to  expose  as  great  a surface  as  possible 
to  the  medium.  It  is  well  known  that  the  area  of  surface  of  a sphere  is  less 
in  proportion  to  its  cubical  contents  than  is  that  of  a cylinder  or  of  any  other 
solid  body.  By  offering  a greater  surface  to  the  liquid  in  which  it  is  growing, 
the  yeast  cell  presumably  is  enabled  to  absorb  a greater  amount  of  nutri- 
ment. In  breweries  where  sugar  is  largely  used  as  a substitute  for  malt  the 
yeast  suffers  from  the  low  percentage  of  nitrogenous  matters  contained  in  the 
wort  : the  result  is  that  such  yeast  has  little  vitality  and  is  soon  exhausted. 

Large  quantities  of  mineral  salts  also  effect  the  shape  of  the  yeast  cell  ; 
thus,  the  yeast  of  Burton  ale  is  oval  (egg-shaped)  in  outline  : the  Burton 
water  is  extremely  hard,  containing  calcium  sulphate  in  large  quantities. 

Badly  nourished  yeast,  on  examination,  is  usually  found  to  have  abnor- 
mally thin  and  fragile  cell  walls,  these  being  broken  by  the  slightest  pressure  ; 
the  contents  of  the  cells  are  also  thin  and  watery,  instead  of  full  of  healthy 
granulations  of  gelatinous  protoplasm. 


313.  Sporular  Reproduction  of  Yeast.— In  addition  to  the  budding 
process  already  described,  yeast  also  reproduces,  when  deprived  of  all  nour- 
ishment by  the  formation  of  spores  within  the  cell.  To  observe  this  effect, 
prepare  first  a block  of  plaster  of  Paris  by  taking  some  of  the  powder,  rapidly 
making  it  into  a thin  paste,  and  then  pouring  same  into  a cardboard  mould. 
Let  it  set  and  then  strip  away  the  cardboard.  Smear  on  the  smooth  surface  of 
tlie  plaster  a little  pressed  yeast  which  has  been  previously  washed  in  distilled 
water  Place  the  block  with  yeast  face  upwards  in  a shallow  dish,  and  pour 
in  water  until  its  surface  is  just  a little  below  that  of  the  yeast.  Cover  it 
over  with  a glass  shade  to  keep  out  dust,  etc.,  and  stand  in  a warm  place  (about 
20-25°  C.).  Each  day  remove  a little  and  examine  under  the  microscope  ; 

after  a few  days  some  of  the  cells  will 
show  denser  masses  of  protoplasm  aggre- 
gated around  from  two  to  four  points. 
These  gradually  grow,  and  at  last  occupy 
the  whole  of  the  interior  of  the  cell.  They 
become  coated  with  cell  envelopes,  and 
then  constitute  ascospores.  The  walls  of 
the  ascus  or  mother-cell  after  a time  dis- 
appear, and  the  liberated  spores  perform 
tlie  functions  of  yeast,  inducing  fermenta- 
tion  and  reproducing  by  the  ordinary  mode  of  budding.  Among  the  con- 
ditions necessary  for  spore  formation  are  young  and  vigorous  cells,  com- 
narative  absence  of  nutriment,  and  a fairly  warm  temperature.  The  speed 
of  spore  formation  is  greatly  influenced  by  the  latter  condition  ; within  ^rtam 
limits  increase  of  temperature  quickens  the  formation  of  spores.  This  is 
also  termed  multiplication  by  endogenous  division.  Cells  containing  ascos- 
pores are  sliown  in  Fig.  H,  which  represents  the  first  stages  of  development 
of  the  snores  of  S.  Cerevisiee  I.,  after  Hansen  : a,  6,  c,  d,  e contain  rudi- 
ments of  spores,  with  the  walls  not  yet  distinct  ; /,  g,  h,  i,  j are  completely 
develpped  spores  with  distinct  walls. 

314  Substances  inimical  to  Alcoholic  Fermentation.— Dumas  has  care- 
fully investigated  the  action  of  foreign  substances  on  alcoholic  fermenta- 
tion • Schutzenberger  quotes  largely  from  his  rsults  ; the  following  data 
obtained  by  Dumas  are  taken  from  the  English  translation  of  Schutzenber- 
ger’s  work^  In  the  first  place,  a series  may  be  given  of  those  bodies  which 


Fig.  11. — Ascospores. 


FERMENTATION. 


167 


retard,  and  when  in  sufficient  quantity  absolutely  arrest,  fermentation, 
These  include  the  mineral  acids  and  alkalies  (phosphoric  acid  excepted), 
soluble  silver,  iron,  copper,  and  lead  salts  ; free  chlorine,  bromine  and  iodine, 
alkaline  sulphites,  and  bisulphites  of  the  alkaline  earths,  manganese  peroxide  ; 
essences  of  mustard,  lemon,  and  turpentine  ; tannin,  carbolic  acid  (phenol), 
creosote,  salicylic  acid  ; sugar  in  excess,  alcohol  when  its  strength  is  over 
£0  per  cent.  ; and  hydrocyanic  and  oxalic  acids,  even  in  small  quantities. 
Phosphoric  and  arsenious  acids  are  inactive.  Sulphur  has  no  effect  on  fer- 
mentation, but  the  carbon  dioxide  gas  evolved  contains  from  one  to  two  per 
cent,  of  sulphuretted  hydrogen. 

As  may  be  gathered  from  the  statement  of  the  chemical  changes  produced 
by  yeast,  that  substance  gives  always  a more  or  less  acid  reaction.  Dumas 
states  that  this  acidity  requires,  for  its  neutralisation,  alkali,  equivalent  to 
0 *003  grams  of  normal  sulphuric  acid  per  gram  of  yeast.  In  his  experiments 
he  added  various  acids  to  yeast  in  proportions  of  from  one  to  a hundred  times 
the  normal  acid  of  the  yeast.  In  this  manner  was  determined  the  retarding 
or  other  action  of  the  various  acids  on  fermentation.  Similar  experiments 
were  made  with  bases,  and  also  salts  ; with  the  latter,  saturated  solutions 
were  first  made  ; the  yeast  was  allowed  to  soak  in  these  for  three  days,  and 
then  its  fermenting  power  tested  by  its  action  on  pure  sugar.  Dumas  divided 
the  salts  into  four  groups.  First,  those  under  wdiose  influence  the  fermenta- 
tion of  the  sugar  is  entire,  and  more  or  less  rapid  ; second,  those  which  permit 
partial  but  more  or  less  retarded  fermentation  ; third,  those  which  permit  the 
sugar  to  be  more  or  less  changed,  but  without  fermentation  ; fourth,  those 
that  prevent  both  change  and  fermentation.  Alum  is  placed  in  the  first  of 
these  classes,  borax  in  the  second,  and  sodium  chloride  (salt)  in  the  third. 
Strychnine  has  no  effect  on  the  properties  of  yeast.  For  a detailed  account 
of  Dumas’  results  the  student  is  referred  to  Schiitzenberger’s  work. 

315.  Isolation  of  Yeast  and  other  Organisms. — ^As  a preliminary  to  the 
study  of  varieties  of  yeast,  it  is  absolutely  necessary  to  have  some  means 
of  separating  and  growing  each  variety  in  a state  of  absolute  purity.  Pas- 
teur did  an  enormous  amount  of  work  in  this  direction  ; but  the  crucial 
point  in  all  such  investigations  as  these  is  the  purity  or  otherwise  of  the  yeast 
used  to  commence  the  experiment  ; in  all  Pas- 
teur’s researches  he  used  an  apparatus  which 
afforded  most  excellent  means  for  the  prevention 
of  the  incursion  of  foreign  germs  during  his 
growth  ; but  he  does  not  give  us  an  absolutely 
certain  method  of  obtaining  a perfectly  pure  yeast 
to  start  with.  In  flasks  of  special  construction, 
well  known  as  “ Pasteur’s  Flasks  ” (Fig.  12), 

Pasteur  introduces  wort,  then  sterilises  the  same 
by  boiling  it,  and  afterwards  sows  therein  a small 
quantity  of  the  yeast  he  wishes  to  cultivate  in  the 
pure  state.  The  Pasteur’s  Fasks  have  a long 
narrow  neck,  which,  as  shown  in  the  illustration, 
is  bent  twice  on  itself,  the  end  being  stopped  with 
a plug  of  cotton  wool.  In  addition,  there  is  a 
side  tubulure,  stopped  with  india  rubber  tubing 
and  a glass  plug.  The  wort  is  introduced  through 
the  side  tube,  and  when  boiled  the  steam  escapes 
through  the  bent  tube.  On  cooling,  the  air 
which  enters  is  sterilised  by  filtration  through  the  cotton  wool.  The  yeast 
is  sown  during  a momentary  removal  of  the  glass  plug.  On  the  com- 
pletion of  this  fermentation,  a little  of  the  new  growth  of  yeast  is  taken 


Fig.  12. — “ Pasteur’s 
Flask.” 


168 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  transferred  with  all  due  precautions  to  a second  Pasteur's  Flask  of  steri- 
lised wort,  and  there  again  fermented.  The  yeast  was  grown  in  this  way 
again  and  again,  until  the  experimenter  was  of  opinion  that  the  preponderat- 
ing growth  of  the  yeast  would  have  crowded  out  of  existence  any  foreign 
germs.  To  further  aid  in  accomplishing  this  object,  Pasteur  also  introduced 
in  his  growth-flasks  some  substances  inimical  to  the  organisms  he  wished  to 
exclude,  or  else  worked  at  a temperature  specially  favourable  to  the  particu- 
lar organism  whose  growth  he  desired  to  favour.  The  yeast  obtained  in  this 
manner  he  terms  pure  yeast  ; undoubtedly  this  may  be  possible,  and  in  many 
experiments  was  probably  the  case  ; but  it  is  nevertheless  only  a possibility 
we  have  to  deal  with,  for  the  germs  of  foreign  organisms  may  not  be  really 
dead,  but  only  present  in  smaller  quantity  and  in  a weaker  condition.  More 
recent  investigators  have  described  methods  by  which  it  is  possible  to  culti- 
vate and  develop  the  growth  of  yeast  from  one  single  isolated  cell  ; in  this 
manner  giving  the  surest  guarantee  of  the  actual  purity  of  the  yeast  produced. 

A first  step  in  this  direction  is  the  adoption  of  what  is  known  as  “ Naegeli's 
Dilution  Method,"  which  is  based  on  diluting  down  the  liquid  under  examin- 
ation until  a single  drop  will,  on  the  average,  contain  but  one  organism.  This 
may  be  accomplished  in  the  case  of  yeast  by  taking  a drop  of  the  mixture  of 
yeast  and  water,  diluting  it  down  considerably  with  water  previously  steri- 
lised by  boiling,  until  the  number  of  cells  present  in  a drop  can  be  counted 
under  -the  microscope.  If  these  are  estimated,  for  instance,  to  be  about  one 
hundred,  then  this  liquid  is  further  diluted  to  a hundred  times  its  volume. 
Every  precaution  must  be  taken  to  sterilise  all  vessels  and  liquids  used  in 
the  operation.  Each  drop  of  this  ultimate  dilution  of  yeast  should  contain 
one  cell  only.  Ten  drops  are  then  placed  in  20  c.c.  of  sterilised  water,  and 
thoroughly  agitated.  One  c.c.  is  then  placed  in  each  of  20  separate  flasks 
containing  culture  fluid,  which  may,  for  example,  be  sterilised  wort.  The 
probability  is  that  ten  out  of  the  twenty  flasks  will  contain  but  one  organ- 
ism only,  the  others  remaining  unimpregnated.  But  here  again  it  is  only  a 
balance  of  probabilities,  and  no  certain  inferences  may  be  drawn.  Hansen 
proceeded  a step  further  by  showing  that,  if  the  inoculated  flasks  are  vigor- 
ously shaken,  and  then  allowed  to  stand,  the  yeast  cells  will  sink  to  the 
bottom  and  attach  themselves  to  the  sides  of  the  flask.  If  more  than  one 
cell  be  present,  the  probabilities  are  that  they  vdll  lie  on  the  bottom  some  dis- 
tance apart.  After  some  days  the  flask  is  raised  carefully,  and  each  yeast 
cell  will  be  the  centre  of  a small  white  speck  visible  to  the  naked  eye,  and 
consisting  of  a colony  of  yeast.  If  only  one  such  speck  be  found,  the  flask  con- 
tains a pure  culture  from  one  cell  only.  Subsequent  cultivation  may  proceed  on 
the  lines  laid  down  by  Pasteur. 

Koch,  in  his  experiments  on  Bacteria  (certain  minute  organisms  to  be 
hereafter  described),  used  specially  prepared  gelatin  as  a cultivating  medium. 
The  material  was  mixed  with  water  until  it  acquired  such  a consistency  as  to 
set,  when  cold,  into  a jelly,  which  became  fluid  at  a temperature  of  35°  C. 
lYr  a cultivation  experiment  some  of  the  gelatin  is  melted,  a few  of  the  bac- 
teria are  taken  out  on  the  point  of  a needle  and  added  to  the  gelatin.  They 
are  then  diffused  by  shaking  up  the  mixture,  which  is  next  poured  out  upon  a 
flat  surface  properly  protected.  After  some  hours,  a separate  and  pure  cul- 
ture is  obtained  from  each  single  bacterium  present.  On  taking  a minute 
particle  from  one  of  these  little  culture  spots,  and  again  sowing  it  in  gelatin, 
a single  species  of  bacterium  was  obtained.  It  was  by  experiments  based  on 
this  principle,  but  carried  out  with  most  special  precautions,  that  Koch  iso- 
lated and  exhaustively  studied  the  ''Comma  Bacillus''  of  cholera,  so 
inseparably  associated  with  his  name. 

Hansen  modified  this  method  for  yeast  culture,  using,  instead  of  Koch's 
nutrient  gelatin  (which  consisted  usually  of  meat  broth  and  gelatin),  a mix- 


FERMENTATION. 


169 


ture  of  hopped  wort  and  gelatin.  In  a bright  hopped  wort  of  about  1058 
gravity  is  dissolved  from  5-10  per  cent,  of  gelatin,  the  quantity  being  regulated 
so  as  to  cause  the  mixture  to  “ set  ” at  30-35°  C.,  being  solid  below,  and  liquid 
above  those  temperatures.  This  mixture  must,  of  course,  be  thoroughly 
sterilised.  Some  of  the  yeast  which  it  is  desired  to  cultivate  is  first  diluted 
doum  by  the  Naegeli  method  until  of  a convenient  degree  of  dilution.  This 
must  be  ascertained  by  experience  : a drop  of  this  solution  is  next  taken  by 
means  of  a sterilised  piece  of  platinum  wire,  and  transferred,  wire  and  all,  to 
a flask  containing  some  of  the  treated  gelatin  preparation.  This  is  agitated, 
so  as  to  secure  thorough  mixture,  but  at  the  same  time  the  production  of  froth 
must  be  avoided.  A drop  of  this  gelatin  is  taken  out  and  examined  micro- 
scopically to  determine  whether  a sufficient  number  of  yeast  cells  are  present. 
Should  they  be  too  crowded,  the  contents  of  the  flask  are  diluted  with  more 
gelatin  ; if  too  few  are  present,  some  more  must  be  taken  from  the  yeast- 
containing  flask  by  means  of  another  piece  of  platinum  wire.  To  cultivate 
the  yeast,  a modification  of  Koch's  glass-plate  known  as  Bottcher’s  moist 
chamber,  is  employed. 

The  chamber  consists  of  a microscope  slide,  on  which  is  cemented  the 
glass  ring,  c,  the  upper  surface  of  which  is  ground  flat.  In  use,  a small 


Fig.  13. — Bottcher’s  Moist  Chamber. 

a,  Thin  Cover-glass  ; b,  Layer  of  Nutritive  Material ; c,  Glass  Ring ; d.  Layer  of  Sterilised  Water. 


quantity  of  the  gelatin  and  yeast,  as  prepared  above,  is  placed  on  the  under 
side  of  the  cover-glass.  The  upper  edge  of  the  glass  ring  is  smeared  with 
vaseline,  and  a few  drops  of  water  placed  in  the  bottom  of  the  chamber. 
The  cover-glass  and  gelatin  is  placed  on  the  ring  and  gently  pressed  down, 
when  the  vaseline  makes  a tight  joint  between  it  and  the  chamber.  Each 
yeast  cell  embedded  in  the  gelatin  can  now  be  subjected  to  microscopio 
examination,  and  any  particular  one  kept  under  observation.  To  do  this, 
any  of  the  devices  in  common  use  as  finders  for  any  particular  part  of  a 
microscopic  object  may  be  employed,  but  a very  convenient  one  is  Klonne 
and  Muller’s  marker,  which  consists  of  an  appliance  that  can  be  screwed  con- 
centrieally  into  the  screw  of  the  microscope  which  carries  the  objective. 
The  desired  cell  is  brought  into  the  centre  of  the  field  : the  objective  is 
removed  and  the  marker  substituted  for  it.  By  means  of  the  focussing 
screw  it  is  lowered  gently  on  to  the  cover,  on  which  it  marks  a small  ring 
encircling  the  cell  required  to  be  kept  under  observation.  The  cell  is  allowed 
to  develop  until  a visible  colony  is  formed.  By  means  of  a sterilised  piece 
of  platinum  wire  it  is  now  picked  off,  and  used  to  seed  a prepared  culture 
solution  in  a Pasteur’s  or  other  flask.  This  operation  of  transference  may 
be  conducted  in  a dust-free  room  in  the  open  air,  but  preferably  in  a small 
eupboard  kept  for  the  purpose,  the  walls  of  which  have  been  moistened 
with  glycerin,  so  as  to  maintain  the  interior  as  a germ-free  space.  The 
apparatus,  and  the  hands  of  the  operator,  are  introduced  through  a door 
just  sufficiently  large  to  provide  for  their  admission.  Large  cultures  are 
made,  as  before,  by  successive  transferences  to  larger  flasks. 

Hansen’s  experiments  on  the  effect  on  brewing,  of  specific  varieties  of 
yeast,  were  made  with  cultures  obtained  in  this  manner  from  single  cells. 


170 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


316.  Classification  of  Yeasts. — In  classifying  yeasts  as  a genus  of  the 
fungi,  they  have  received  the  following  definition,  based  upon  that  of  Rees. 

Classification  of  the  Genus  Saccharomyces. 

Budding  Fungi,  mostly  without  a mycelium,  the  individual  species  of 
which  occur  with  cells  of  different  form  and  size.  Under  certain  treat- 
ment, and  sometimes  also  without  any  previous  treatment,  cell-nuclei  are 
seen.  Under  certain  conditions  the  cells  develop  endogenous  spores  ; the 
germinating  spores  of  most  species  grow  to  budding  cells  ; in  exceptional 
cases  a promycelium  is  first  formed.  Number  of  spores  I to  10,  most  fre- 
quently I to  4.  Under  favourable  conditions  the  cells  secrete  a gelatinous 
network,  in  which  they  lie  embedded. 

The  greater  number  of  the  species  induce  fermentation. 

The  following  is  a list  of  the  more  important  species  : — 

Saccharomyces  cerevisice  . . 

,,  Minor 

,,  Ellipsoideus 

„ Pastor  ianus. 

317.  Saccharomyces  Cerevisae,  or  Ordinary  Yeast. — At  least  two  distinct 
varieties  of  ordinary  yeast  are  known,  to  which  the  names  of  “ High 
and  “ Low  ” yeast  have  been  given.  The  former  of  these  is  the  common 
yeast  of  English  ale  fermentation  ; the  other,  that  of  the  well-known  “ lager 
beer  of  continental  production.  Saccharomyces  minor,  a species  of  yeast 
found  in  leaven,  is  also  possibly  a sub-variety  of  S.  cerevisice,  so,  too,  is  the 
distillers'  yeast  made  in  this  country,  and  also  imported  from  Holland  and 
France,  and  sold  as  compressed  yeast. 

318.  High  Yeast  . — This  variety  is  so-called  beeause  of  its  ascending  to 
the  top  of  the  fermenting  liquid  during  fermentation.  It  consists  of  cells 
mostly  round  or  slightly  oval,  from  8 to  9 /x  in  diameter,  and  answering 
generally  to  the  description  of  yeast  given  in  paragraphs  301  and  302. 
Illustrations  of  Brewers'  High  Yeast,  Distillers'  Yeast,  and  Bakers'  Patent 
Yeasts  are  given  in  Plate  II.,  to  which  reference  is  also  made  in  Chapter 
XII. 

319.  Low  Yeast. — ^Sedimentary  yeast,  or  the  “ low  " variety  of  Saccharo- 
myces cerevisice,  is  that  used  in  the  manufaeture  of  lager  beer.  In  general 
properties  it  much  resembles  the  high  yeast  which  has  already  been  studied. 
In  form  the  cells  are  somewhat  smaller,  and  also  rather  more  oval  than  those 
of  normal  high  yeast  ; but  differ  very  little  in  shape  from  high  yeast  when 
grown,  as  at  Burton,  in  very  hard  waters.  Fig.  9,  paragraph  301,  gives 
illustrations  of  low  yeast. 

320.  Distinctions  between  High  and  Low  Yeast. — ^Whereas  high  yeast 
rises  to  the  surface  of  the  liquid  during  fermentation,  “ low  " yeast  always 
falls  to  the  bottom,  and  forms  a sediment  there  ; hence  the  name  “ sedi- 
mentary " yeast.  Brewing  with  low  yeast  is  performed  at  much  lower 
temperatures  than  with  high  ; thus,  whereas  with  the  latter  pitching  tem- 
peratures of  20°  or  21°  C.  (68°  or  70°  F.)  are  employed,  the  lager  beer  brewer 
starts  his  fermentation  at  as  low  as  8°C.  (47°  F.),  or  even  6°C.  (43°  F.). 
Working  with  this  low  temperature,  fermentation  proceeds  much  less  rapidly 
than  with  high  yeast  ; growth  and  reproduction  proceed  more  slowly,  and 
tlie  budding  gives  rise  to  less  extensive  colonies  of  cells.  As  Pasteur  aptly 


( High  Yeast. 

1 Low  Yeast. 
Ferment  of  Leaven. 
Ferment  of  Wine. 


Plate  II. 


J^re-yrars’  . 


Iiakjer.<  7c(tent  Y£,<jbsTy._ 


Various  Commercial  Yeasts. 

JiXocJiarofnyoes  Ccr&vuu'xr., 
^ixy/ti/Zed  ctbavit  400  Tyicurxjytcrs. 


171 


172 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


describes  it,  low  yeast  when  growing  has  a much  less  ramified  appearance. 
(See  Fig.  10.)  It  is  doubtful  whether  the  term  “ low,''  as  applied  to  this 
yeast,  has  been  given  from  the  lowness  of  the  temperature  employed  for 
fermentation,  or  because  the  yeast  always  drops  to  the  bottom  of  the  fer- 
menting vat  ; both  are  characteristics  of  this  variety.  This  yeast  is  further 
distinguished  by  its  producing  a different  type  of  beer  to  the  celebratee 
product  by  high  fermentation  of  English  and  Scotch  breweries. 

It  may  be  well  to  mention  that  the  low  yeast  of  lager  beer  is  not  that  which 
is  being  imported  from  the  continent,  and  sold  so  largely  for  bread-making 
purposes.  As  a matter  of  fact,  lager  beer  yeast  is  very  badly  suited  for  the 
fermentation  of  bread  ; its  action  is  extremely  slow,  and  results  in  the  pro- 
duction of  a heavy,  sodden,  and  frequently  sour,  loaf. 

321.  Convertibility  of  High  and  Low  Yeasts. — This  has  been  for  many 
years  a much-discussed  problem  both  by  brewers  and  scientists,  and  is 
typical  of  the  discussions  which  arise  on  the  general  question  of  the  immuta  - 
bility  or  otherwise  of  the  different  yeast  species  and  varieties.  Students 
who  approach  this  subject  with  a previous  knowledge  of  the  laws  of  the 
origin  of  species  as  a result  of  evolution,  as  enunciated  and  demonstrated 
by  Darwin,  will  be  prepared  to  expect  from  the  general  evidence  of  biology 
that  not  only  high  and  low  yeasts,  but  also  all  forms  and  species  of  sac- 
cliaromyces,  have  had  one  common  origin,  their  diversities  having  been  pro- 
duced by  differences  in  environment  extending  over  numberless  generations. 
When  discussing,  however,  whether  or  not  low  and  high  yeast  are  convert- 
ible, and  really  therefore  of  the  same  species,  it  is  understood  that  the 
question  refers  to  convertibility  during  small  amounts  of  time,  not  such 
lengthy  periods  as  are  requisite  for  an  actual  evolution  of  distinct  species. 
Pasteur,  at  an  earlier  period  of  his  researches,  considered  the  two  yeasts  to  be 
convertible,  but  as  the  result  of  later  investigations,  affirmed  the  two  yeasts 
to  be  distinct.  This  belief  is  founded  on  experiments  in  which  high  yeast  is 
grown  repeatedly  at  the  lowest  possible  temperature,  and  low  yeast  at  the 
temperature  employed  for  high  fermentation.  Supposing  the  yeasts  to  be 
pure  at  the  commencement  of  such  an  experiment,  he  asserts  that  no  trans- 
formation of  the  one  variety  into  the  other  is  effected.  In  this  opinion  he 
differs  from  many  brewers,  who  state  that  under  such  conditions  the  one 
yeast  is  converted  into  the  other.  Pasteur  gives  the  following  explanation 
of  the  observed  change  : if  the  high  yeast  had  in  it  a few  cells  of  low  yeast 
as  impurity,  on  being  sown  and  caused  to  reproduce  at  a low  temperature, 
the  low  yeast  cells  present  would  thrive  well,  while  the  high  yeast  would 
languish.  The  minute  quantity  of  low  yeast  cells,  finding  the  conditions 
favourable  to  their  growth,  develop  ; and  the  others,  through  the  conditions 
being  unfavourable,  are  after  a time  outnumbered  and  disappear.  The 
change  of  low  into  high  yeast  is  explained  as  being  just  the  converse  of  that 
now  described.  The  latest  authoritative  dictum  on  this  subject  is  that  of 
Jorgensen,  who,  in  1893,  asserts  that,  “ in  spite  of  many  assertions  to  the 
contrary,  it  has  not  hitherto  been  possible  to  bring  about  an  actual  conver- 
sion of  top-yeast  into  bottom-yeast,  or  vice  versa.  The  investigations  of 
Hansen  and  Kiihle  show  that  it  is  certainly  possible  for  a bottom-fermenta- 
tion yeast  to  produce  transitory  top-fermentation  phenomena  ; these,  how- 
ever, quickly  disappear  Avith  the  progressive  development  of  the  yeast." 

322.  Distillers’  Yeast. — The  yeasts  employed  by  distillers  for  the  purpose 
of  fermenting  their  worts  differ  in  some  most  important  characteristics  from 
ordinary  brewers'  yeast.  They  are,  in  the  first  place,  grown  in  un-hopped 
worts,  as  against  the  hopped  worts  of  the  brewer.  In  appearance  they 
resemble  low  yeast  more  closely  than  the  normal  brewers'  high  yeast,  aver- 


FERMENTATION. 


173 


aging  slightly  smaller  in  size,  and  forming  less  extensive  colonies.  The 
yeast  is  less  mucilaginous  than  that  of  the  brewer,  and  so  does  not  form  so 
sticky  a mass.  The  distillers’  yeasts  are  ordinarily  high  yeasts,  but  see  the 
subsequent  account  of  compressed  yeast  manufacture.  Chapter  XII.  They 
are’sharply  separated  from  the  brew  ers’  yeast  by  their  capacity  for  inducing 
a vigorous  fermentation  in  dilute  mixtures  of  flour  and  w ater.  If  equal  w eights 
of  brew  ers’  and  distillers’  yeast  be  sowm  in  a solution  of  sugar  in  water,  and 
fermented  under  the  same  conditions,  the  brew  ers’  yeast  will  usually  cause 
a slightly  more  rapid  evolution  of  gas  ; but  if,  instead,  a mixture  of  flour 
and  w ater  be  used,  the  distillers’  yeast  w ill  cause  many  times  more  gas  to  be 
evolved  than  does  that  from  the  brew^er.  This  difference  is  not  ow  ing  to 
the  absence  of  sugar,  for  if  to  the  flour  and  w'ater  sugar  be  added  in  the  same 
proportion  as  in  the  pure  sugar  solution,  there  is  still  little  or  no  more  fer- 
mentation caused  by  the  brew  ers’  yeast.  The  probable  reason  is  the  actual 
toxic  effect  of  certain  constituents  of  flour  on  brewers’  yeast.  (See  para- 
graph 378.) 

Jorgensen  states  that  distillery  yeasts  exhibit  marked  differences  in 
their  sedimentary  forms,  and  in  ascospore  formation,  to  browsers’  yeasts. 
Microscopic  examination  of  compressed  yeast,  according  to  Belohoubek, 
indicates,  in  the  following  manner,  alterations  in  the  appearance  of  the 
cells.  As  decomposition  sets  in,  the  protoplasm  becomes  darker  in  colour 
and  more  liquid  ; the  vacuoles  become  larger,  and  the  sharp  outline  betw^een 
them  and  the  plasma  gradually  disappears  : the  plasma  shrinks  from  the 
cell-wall,  and  Anally  collects  in  irregular  masses  in  the  cell-fluid.  At  times 
cells  appear  in  pressed  yeast,  which  suddenly  develop  a number  of  small 
vacuoles  ; these  abnormal  vacuolar  cells  speedily  jrerish. 


323.  Saccharomyces  Minor. — This  is  a form  of  yeast  described  by  Engel 
as  being  obtained  by  him  from  leaven  (a  name  given  to  old  dough).  To 
obtain  the  ferment  he  w ashes  a piece  of  leaven  in  the  same  w^ay  as  described 
in  a previous  chapter  for  the  separation  of  the  gluten  of  flour  from  its  starch. 
The  yeast  cells  pass  through,  and  may  be  detected  by  microscopic  examina- 
tion of  the  liquid  after  the  larger  starch  cells  have  settled  to  the  bottom.  The 
cells  of  Saccharomyces  minor  are  globular,  occurring  either  isolated  or  in  pairs 
or  groups  of  three.  They  are  about  6 mkms.  in  diameter,  and  have  an  indis- 
inct  vacuole.  In  Pasteur’s  fluid  they  reproduce  but  slowly,  and  form  new 
cells  of  the  same  dimensions  as  were  the  original.  They  easily  reproduce  by 
sporulation,  the  spores  being  about  3 mkms.  in  diameter,  and  are  united  in 
twos  or  threes.  They,  on  the  whole,  closely  resemble  the  yeast  of  beer. 
Although  Engel  treats  saccharomyces  minor  as  a distinct  variety,  the  balance 
of  evidence  is  in  favour  of  its  identity  with  S.  cerevisice.  Grove,  considers  it 
to  be  but  a form  of  that  ferment.  The  lesser  size  and  activity  may  be  attri- 
buted to  its  having  continually  reproduced  itself  in  an  unfavourable  medium, 
such  as  dough  ; hence  its  stunted  appearance  and  slow  growth,  as  compared 
with  the  more  favourably  environed  yeast  of  beer. 

Engel  view  s this  form  of  yeast  as  being  the  active  ferment  in  the  fermen- 
tation of  bread.  In  this,  of  course,  he  is  referring  to  continental  black  bread, 
in  the  fermentation  of  which  leaven  is  employed,  this  being  made  by  knead- 
ing together  flour,  bran,  and  W'ater,  and  allowing  the  mass  to  undergo  spon- 
taneous fermentation. 

White  bread  fermented  w ith  either  brewers’  or  distillers’  yeast  belongs  to  a 
totally  different  category. 

Saccharomyces  minor  and  other  yeast  varieties  are  illustrated  in  Plate  III. 
The  numbers  following  the  multiplying  sign  give  the  magnification  in  dia- 
meters. 


174 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


324.  Saccharomyces  Ellipsoideus. — ^This  is  the  ordinary  ferment  of 
vinous  fermentation,  that  is,  that  by  which  “ must,""  or  the  expressed  juice 
of  the  grape,  is  converted  into  wine.  The  cells  of  this  variety  of  yeast  are 
oval,  and  about  6 mkms.  long  ; they  reproduce  both  by  budding  and  spores. 
When  grown  in  malt  wort,  they  produce  a beer  of  a decided  vinous  flavour, 
which  is  sometimes  made  and  sold  as  “ barley  wine."" 

325.  Saccharomyces  Pastorianus. — The  cells  of  this  variety  of  yeast 
vary  considerably  in  size  ; they  are  cylindrical  in  shape,  with  oval  ends,  and 

appear  when  seen  in  colonies  some- 
what like  strings  of  sausages.  Bud- 
ding occurs  at  the  joints,  where 
groups  of  smaller  daughter  cells  may 
be  observed  ; these  are  first  either 
round  or  slightly  oval.  The  elon- 
gated cells  are  from  18  to  22  mkms. 
long,  and  about  4 mkms.  in  dia- 
meter ; the  daughter  cells  are  about 
5 to  6 mkms.  in  length. 

S.  Pastorianus  occurs  in  the 
after-fermentation  of  wine  and  beer, 
and  also  in  bakers"  “ patent  ""  yeasts. 
As  it  is  found  in  English  beers  which 
have  been  kept  for  some  time  in 
store,  cells  of  it  are  probably  more 
or  less  present  in  all  commercial 
English  yeasts.  Being  a less  active 
variety  than  S.  cerevisice,  it  remains  dormant  while  the  first  or  principal 
fermentation  proceeds  ; but  when  the  most  of  the  sugar  has  disappeared, 
the  S.  'pastorianus,  being  able  to  live  and  develop  in  a less  nutritious  medium, 
grows  and  reproduces.  Brown  and  Morris  point  out  that  the  amyloins 
cannot  be  either  fermented  or  hydrolysed  by  ordinary  yeast  ; but  that 
8.  pastorianus  is  capable  of  hydrolysing  maltodextrin  for  itself,  thus  giving 
rise  to  an  apparent  direct  fermentation  of  that  body.  This  will  explain  how 
this  latter  ferment  thrives  and  reproduces  in  a medium  so  deficient  of  sugar 
as  not  to  permit  the  growth  of  Saccharomyces  cerevisice. 

328.  Saccharomyces  Mycoderma,  or  Mycoderma  Vini. — Closely  allied 
to  the  saccharomyces  already  described  under  the  name  of  yeast  is  this  species, 
which  belongs  to  the  fungus  family  proper.  Saccharomyces  mycoderma  re- 
quires for  its  growth  and  development  free  oxygen,  and  belongs  to  Pasteur’s 
division  of  “ aerobian  ""  plants.  Although  the  fungi  proper  luxuriate  rapidly 
when  growing  with  free  access  to  air,  yet  they  are  speedily  destroyed  by 
enforced  submergence  below  the  surface  of  a liquid.  Saccharomyces  myco- 
derma occurs  on  the  surface  of  wine,  beer,  and  bakers"  yeasts,  on  their  being 
exposed  for  some  days  to  the  air,  forming  after  a time  a thick  wrinkled  skin  or 
mycelium  ; in  which  state  it  is  said  to  be  “ mothery.""  The  mycoderma 
is  known  as  that  of  wine  (vini),  or  of  beer  (cerevisiae)  according  to  the  liquid 
on  wliicli  it  appears.  Viewed  under  the  microscope,  the  mycelium  is  found 
to  consist  of  extending  brandies  of  elongated  cells  closely  felted  or  inter- 
twined togetlier.  8ee  illustration  on  Plate  III.,  and  Fig.  15  of  Mycoderma 
cerevisice.  The  individual  cells  are  either  oval  or  cylindrical,  with  rounded 
ends.  They  are  about  6-7  mkms.  long,  and  2-3  mkms.  in  diameter.  The 
Mycoderma  vini  reproduces  either  by  budding  or  by  spores.  The  spore  form- 
ing cells  attain  a length  of  as  much  as  20  mkms.  Particularly  in  summer  time, 


Fig.  14. — Saccharomyces  Pastorianus. 
a,  The  same  more  highly  magnified  (after  Pasteur).' 


Plate  ID. 


Caseous  Yeasts . x J60 
L H N?/  R.H.  NO  2. 

ri^3. 


S.Cxiguus.  X 300. 

L.  f Afar  Ret'ss.  R.H.  fA.&L. 


F,  q 6. 


S Clhpsoideus.  X JOO 
U R ifttx  Re^ss  R H. 


Mycoderma  Vini  x 300 
L h Aerobicut  form.  R H.  Submerged  form. 


( after  Moathje>ffs  & law ) 


Various  “Foreign”  Yeasts. 


175 


176 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

the  growth  of  this  fungus  proceeds  with  extreme  celerity,  the  mycelium  first 
formed  being  thrown  into  folds  by  its  rapid  development  ; at  the  same  time 
considerable  heat  is  produced.  Microscopic  examination  shows  that  Myco- 
derma  vini  is  very  like  yeast  in  appearance  ; for  a long  time  it  was  supposed 
that  the  two  were  identical,  and  that  the  mouldiness  of  beer  was  produced  by 

the  yeast  cells  ascending  to  the  surface, 
and  there  developing  as  a fungoid 
growth.  The  two  organisms  are,  how- 
ever, distinct  species,  and  have  not 
been  transformed  one  into  the  other. 
My  coderma  vini  during  its  growth 
seizes  oxygen  with  great  avidity,  entirely 
preventing,  during  the  period  of  its 
actual  life,  the  development  of  other 
organisms  also  requiring  oxygen,  but 
endowed  with  less  vital  energy.  Pas- 
teur states  that  on  submerging  this 
mould  during  its  actual  growth  into 
malt  wort,  or  other  saccharine  liquid,  it 
for  a short  time  causes  fermentation, 
with  the  production  of  small  quantities 
of  alcohol ; but  this  action  soon  ceases 
with  the  early  death  of  the  fungus.  In  addition  to  this  limited  fermentative 
action,  Mycoderma  vini  acts  on  wines  and  beers  as  a somewhat  powerful 
oxidising  agent  ; it  conveys  the  oxygen  of  the  air  to  the  alcohol  of  the 
liquid,  causing  its  complete  slow  combustion  into  carbon  dioxide  and  water,, 
and  consequently  rapidly  lessening  the  alcoholic  strength  of  the  medium. 
Although  wines  and  beers  become  sour  simultaneously  with  the  development 
of  Mycoderma  vini,  the  souring  is  not  due  to  this  organism,  but  to  another 
distinct  growth. 

The  limited  alcoholic  fermentation  produced  hj  Mycoderma  vini  leads  to- 
its  being  classed  among  the  saccliaromyces. 

327.  Hansen  on  Analysis  of  Yeasts. — It  is  principally  due  to  the  researches 
of  Hansen  that  we  are  able  to  classify  yeasts  into  species  and  races  with  such 
accuracy  as  is  now  possible.  The  results  of  his  work  have  had  such  important 
effects  on  the  brewing  industry,  and  indirectly  on  that  of  bread-making,  that 
the  present  book  would  not  be  complete  without  some  reference  to  these 
classical  investigations. 

Hansen's  fundamental  idea  was  that  the  shape,  relative  size,  and  appear- 
ance of  yeast  cells,  taken  by  themselves,  were  not  sufficient  to  characterise  a 
species,  since  the  same  species  under  different  external  conditions  could 
assume  very  different  forms.  Further,  although,  for  example,  a microscopic 
field  of  pure  S.  cerevisice  could  be  distinguished  by  its  appearance  from  pure  S. 
pastorianus,  yet  in  a mixture  of  the  two  it  is  not  possible  to  distinguish  indi- 
vidual cells  of  the  one  from  those  of  the  other.  S,  cerevisice  forms  at  times 
sausage-shaped  cells,  while  S.  pastorianus  occurs  to  a certain  extent  as  round' 
or  oval  cells.  Some  other  method,  then,  than  microscopic  examination  is 
necessary  for  their  differentiation. 

328.  Formation  of  Ascos  pores. — By  investigation  of  the  conditions 
under  which  different  races  of  yeast  formed  ascospores,  Hansen  was  enabled 
to  arrive  at  a mode  of  analysis  of  yeasts.  A description  of  the  mode  of  pro- 
cedure by  which  ascospores  are  obtained  has  already  been  given,  but  Hansen 
ascertained  with  more  exactitude  the  precise  conditions  necessary,  and  thus 
sums  up  his  conclusions  : — The  cells  must  be  kept  moist  and  have  a plentiful 


Fig.  15. — Mycoderma  cerevisice. 
From  Copenhagen  Breweries. 


PlAT£  IV. 


Farmation  of  Ascoepores 

I . Saucch  cer'ortetce  I.  2.  . Soucchj . Pcustcrruiruis  I . 

3.  Sauced  PcLSWf^tanujS  11 . A.  Soucchi . J^astxrriciTia^  in . 

5 . ScLcchj.  eUXpsotdbt;cu6  I 6 . Scucch'.  cUlpsoidezhe  II . 

( alter  llaJiserv  x 2000 . ) 


177 


N 


178 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


supply  of  air  ; further,  to  form  spores  they  must  be  young  and  vigorous. 
For  most  species  a temperature  of  25°  C.  is  the  most  favourable  ; for  all 
species  this  temperature  favours  their  development. 

Hansen  found  the  process  of  spore-formation  to  vary  in  different  species. 
S.S.  cerevisice,  'pastorianus,  and  ellipsoideus  germinate  into  spores  in  essen- 
tially the  same  way.  S.  ludwigii  and  8.  anomalus  have  each  a separate 
and  distinct  mode  of  spore  growth. 

While  all  species  form  spores  at  25°,  Hansen  set  himself  to  determine 
whether  with  different  species  there  was  any  difference  in  their  behaviour 
under  varying  conditions  of  temperature.  In  making  observations,  he  regis- 
tered the  time  when  the  cells  first  showed  distinct  indications  of  spore  forma- 
tion. The  limits  of  temperature  for  all  species  are  between  from  0*5  to  3°G. 
and  37*5°  C.  At  the  highest  temperature  all  species  develop  first  indications 
in  about  30  hours,  and  show  very  little  difference  in  time  at  25°  C.  ; but  with 
lower  temperatures  very  evident  differences  occurred.  Hansen  also  found 
that  there  were  differences  in  anatomical  structure  of  spores  that  could  be 
utilised  for  analytic  purposes.  In  the  so-called  cultivated  yeasts,  8.  cere- 
visice employed  for  brewing,  the  spores  have  a distinct  membrane,  with  non- 
homogeneous  granular  contents  and  a definite  vacuole.-  In  the  case  of  the 
so-called  wild  yeasts,  the  spore  wall  is  frequently  indistinct,  the  cell  contents 
homogeneous,  and  the  vacuole  absent. 

Hansen  investigated  very  closely  the  following  six  species  of  yeast,  par- 
ticulars of  which  are  furnished. 

Illustrations  of  the  formation  of  ascospores  are  given  in  Plate  IV. 

8accharomyces  cerevisice  /.,  Enghsh  top -fermentation  yeast.  Ferments 
glucose  and  maltose  very  vigorously.  Spores  strongly  refractive  to  light, 
V alls  very  distinct ; size,  2*5-6  /x. 

8,  pastorianus  /.,  Bottom-fermentation  yeasts  ; frequently  occurs  in  the 
air  of  fermenting  rooms  ; imparts  to  beer  a disagreeable  bitter  taste  and  un- 
pleasant odour  ; can  also  produce  turbidity  and  interfere  with  clarification 
in  fermenting  vat.  Size  of  spores,  1*5-5  ju,. 

8.  pastorianus  //.,  Feeble  top-fermentation  yeast  ; found  in  air  of 
breweries  ; apparently  does  not  cause  diseases  in  beer.  Size  of  spores,  2-5  p. 

8.  pastorianus  III.,  Top-fermentation  yeast,  one  of  the  species  which 
produce  yeast-turhidity  in  beer  ; but  in  certain  cases  clarify  opalescent 
w'orts.  Size  of  spores,  2-5  p. 

8.  ellipsoideus  /.,  Bottom-fermentation  yeast  ; occurs  on  ripe  grapes. 
Size  of  spores,  2-4  /x. 

8.  ellipsoideus  II.,  Usually  bottom-fermentation  yeast  ; causes  yeast 
turbidity,  more  dangerous  than  8.  pastorianus  III.  ; also  imparts  a sweetish, 
disagreeable,  aromatic  taste  to  beer,  and  a bitter,  astringent  after-taste.  Size 
of  spores,  2-5  y,. 

It  will  be  noticed  that  Hansen  sub-divides  both  8.  pastorianus  and  ellip- 
-soideus.  He  also  sub-divides  other  species  into  different  races  or  varieties. 
The  leading  points  of  connection  between  temperature  and  spore  formation  are 
given  in  the  following  table  : — 


FERMENTATION. 

Temperature  and  Spore-Formation  of  Yeasts. 


179 


Sacch. 
Cerev.  I. 

i Sacch. 

' Past.  1- 

Sacch. 
Past.  II. 

Sacch. 
Past.  III. 

Sacch. 
Ellip.  I. 

Sacch. 

I Ellip.  II. 

Highest  limit  of  development. 
Temperature  of  . . 

37-5° 

I 

31-5° 

29° 

29° 

32-5° 

35° 

Most  rapid  development. 
Temperature  of  . . 

30° 

i 27-5° 

25° 

25° 

25° 

29° 

Most  rapid  development. 
Time,  in  hours,  of  appear- 
ance of  first  indication  of 
spores 

20 

i 

i 

1 24 

25 

28 

21 

22 

Time,  in  hours,  of  appearance 
of  first  indications  at  15°  C. 

110 

50 

48 

48 

45  ' 

62 

Lowest  limit  of  development. 
Temperature  of  . . . . 

9° 

0-5° 

0-5° 

4° 

40 

1 

4° 

It  will  be  seen  that  considerable  differences  exist  between  the  various 
yeasts  in  the  particulars  given.  In  addition,  Hansen  has  also  investigated 
the  conditions  of  film  formation  and  other  properties  which  aid  in  the  task 
of  yeast  differentiation. 

329.  Detection  of  “ Wild  ” Yeasts. — In  utilising  spore  formation,  cultures 
are'^made  at  temperatures  of  25°  and  15°  respectively,  the  latter  being  exam- 
ined after  three  days — 72  hours.  All  the  wild  yeasts  will  have  commenced 
to  show  indications,  while  the  cultivated  yeast  will  be  free  from  them. 
When  used  practically  for  technical  purposes,  this  method  is  capable  of  detect- 
ing with  certainty  an  admixture  of  0 *5  per  cent,  of  a wild  yeast  in  an  other- 
wise pure  culture.  For  this  and  other  tests  applied  to  yeast  by  Hansen's 
methods,  it  is  essential  that  the  preliminary  trials  of  the  yeast  be  uniform, 
so  as  to  make  the  tests  comparative. 

330.  Varieties  of  Cultivated  Yeast. — ^Not  only  have  distinctions  been 
drawn  between  cultivated  and  wild  yeasts  by  the  methods  just  described, 
but  also  well-marked  and  distinct  varieties  of  cultivated  yeast  have  been 
grown.  Each  of  these  possesses  distinct  characteristics,  and  is  valued  for 
certain  kinds  of  beer.  Thus,  Jorgensen,  for  'practical  purposes,  classifies 
different  races  of  yeast  prepared  by  pure  culture  methods  in  his  laboratory 
into  the  following  groups  : — 

A. — Bottom-Fermentation  Species. 

1.  Species  which  clarify  very  quickly  and  give  a feeble  fermentation  in 
the  fermenting  vessel  ; the  beer  holds  a strong  head.  The  beer,  if  kept 
long,  is  liable  to  yeast-turbidity.  Such  yeasts  are  only  suitable  for  draught- 
beer. 

2.  Species  which  clarify  fairly  quickly  and  do  not  give  a vigorous  fermen- 
tation ; the  beer  holds  a strong  head  ; high  foam  ; yeast  settles  to  a firm 
layer  in  the  fermenting  vessel.  Beer,  not  particularly  stable  as  regards  yeast- 
turbidity.  Yeasts  are  suitable  for  draught-beer,  and  partly  for  lager  beer. 

3.  Species  which  clarify  slowly  and  attenuate  more  strongly  ; the  beer 
has  a good  taste  and  odour  ; the  yeast  deposit  is  less  firm  in  the  fermenting 
vessel.  Beer  is  very  stable  against  yeast-turbidity.  These  yeasts  are  suit- 
able for  lager  beer,  and  especially  for  export  beers  which  are  not  pasteurised 
or  treated  with  antiseptics. 


180 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


B. — ^Top-Fermentation  Species. 

1.  Species  which  attenuate  slightly  and  clarify  quickly.  The  beer  has 
a sweet  taste. 

2.  Species  which  attenuate  strongly  and  clarify  quickly.  Taste  of  beer 
more  pronounced. 

3.  Species  which  attenuate  strongly,  clarify  slowly,  and  give  a normal 
after-fermentation.  The  beer  is  stable  against  yeast-turbidity. 

Hansen  has  isolated  two  yeast  races  from  ordinary  yeast,  both  of  which 
are  employed  in  the  Carlsberg  breweries  ; these  are  known  as  Carlsberg  No.  I. 
and  Carlsberg  No.  II.  Each  has  distinct  properties  of  its  own  ; thus.  No.  I. 
gives  a beer  well  adapted  for  bottling,  containing  less  carbon  dioxide  than 
No.  II.,  and  possessing  a lower  degree  of  attenuation  ; well  adapted  for  home 
use.  No.  II.  is  principally  cultivated  for  export,  giving  a good  draught-beer 
containing  more  carbon  dioxide. 

Passing  for  a moment  the  work  of  different  investigators  in  review, 
Pasteur  freed  yeasts  from  weeds  or  foreign  vegetable  growths  of  the  bacteria 
group.  Hansen  first  eliminated  wild  yeasts  as  a fruit  grower  might  elimin- 
ate crab-apples  and  other  wild  fruits  from  his  orchard.  Lastly,  he  has  de- 
voted his  attention  to  the  growth  of  distinct  breeds  of  cultivated  yeast,  each 
specialised  for  a particular  type  of  beer.  Jorgensen’s  recent  experiments 
carry  the  analogy  a step  further.  He  finds  that  among  the  progeny  of  a 
single  yeast-cell,  cells  can  be  selected  which  may  show  important  differences 
in  respect  of  the  taste,  smell,  and  other  properties  of  the  fermented  liquid. 
Such  cells  may,  in  fact,  differ  from  each  other  as  do  children  of  the  same 
parents. 

In  yeast  factories  much  the  same  is  being  done  for'the  bakers.  Yeasts  are 
selected  for  their  vigour  and  capacity  for  fermentation,  and  these  are  culti- 
vated to  the  exclusion  of  types  incapable  of  yielding  such  excellent  results. 
Thus  Lindner  has  introduced  a variety  of  pure  culture  yeast  in  most  of  the 
distilleries  of  Germany,  under  the  name  of  Race  II.  The  results  have  been 
good.  A further  development  on  the  same  lines  is  the  employment  of  pure 
cultures  of  the  bacillus  of  lactic  acid  in  distilleries.  As  subsequently  de- 
scribed, this  serves  to  inhibit  excessive  development  of  lactic  acid  itself,  and 
butyric  acid  fermentation.  Race  V.  has  been  specially  recommended  for  this 
purpose. 


Experimental  Work. 

331.  Substances  produced  by  Alcoholic  Fermentation. — Prepare  some 
ten  or  twelve  ounces  of  malt  wort,  by  mashing  ground  malt  in  five  times  its 
weight  in  water  ; and  take  its  density  by  a hydrometer.  To  the  wort  add 
a small  quantity  of  either  brewer’s  or  compressed  yeast,  place  it  in  a flask 
arranged  with  a cork  and  leading  tube,  and  set  it  in  a warm  place 
C.) . Attach  the  leading  tube  to  a flask  containing  lime-water,  so  that  any  gas 
evolved  by  the  yeast  has  to  bubble  through  the  liquid.  Notice  that  after  a 
time  fermentation  sets  in,  and  that  the  yeast  rises  to  the  top  ; gas  bubbles 
tlirough  the  lime-water  and  turns  it  milky,  thus  showing  that  carbon  dioxide 
is  being  evolved.  When  the  liquid  becomes  quiescent  through  the  cessation 
of  fermentation,  again  take  its  density  with  the  hydrometer,  notice  that  it  is 
less  than  before  ; return  the  liquid  to  the  flask,  and  connect  to  a Liebig’s 
condenser  and  distil  ; notice  that  the  first  drops  of  the  distillate  have  the 
appearance  of  tears,  as  described  in  paragraph  100,  Chapter  III.  Cease  dis- 
tilling when  about  one-tenth  of  the  liquid  has  distilled  over  ; notice  that  the 
distillate  has  an  alcoholic  or  spirituous  odour.  Test  it  for  alcohol  by  the 
iodoform  reaction. 


FERMENTATION. 


181 


332.  Microscopic  Study. — ^Proceed  with  this  on  the  lines  of  paragraph  301. 

Mount  a trace  of  the  yeast  in  a little  warm  malt  wort,  and  examine  care- 
fully : notice  alteration  in  appearance  of  the  yeast  cells  as  they  set  up  fer- 
mentation : keep  the  microscope  with  slide  in  focus  for  some  time  in  a warm 
place,  and  observe  from  time  to  time  the  changes  as  they  proceed.  Watch 
specially  for  the  development  of  budding,  and  as  soon  as  any  signs  are  de- 
tected watch  the  cell  at  short  intervals  until  the  bud  has  become  completely 
detached  from  the  parent  cell. 

Sow  a little  yeast  in  a beaker  in  a small  quantity  of  wort  ; take  out  a 
little  and  examine  under  the  microscope  a few  hours  later  : examine  again 
on  each  successive  day  until  some  three  or  four  days  have  olapsed  since  the 
fermentation  has  ceased.  Note  during  the  height  of  the  fermentation  the 
colonies  of  cells,  sketch  some  of  these  : observe  the  clear  outlines  and  trans- 
parent protoplasm  of  the  new  cells  as  compared  with  the  shrunken  appear- 
ance of  the  parent  cells.  As  time  proceeds,  notice  the  gradual  alteration 
in  appearance  of  the  yeast,  until  at  last  the  new  cells  are  similar  in  appearance 
to  those  originally  sown. 

Study  sporular  reproduction  as  directed  in  paragraph  313. 


CHAPTER  X. 

BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS. 


Moulds. 

333.  Schizomycetes. — Grove  defines  the  Schizomycetes  or  “ splitting 
fungi  ” (Spaltpilze)  as  being  unicellular  plants,  which  multiply  by  repeated 
subdivision,  and  also  frequently  reproduce  themselves  by  spores,  which  are 
formed  endogenously.  They  live,  either  isolated  or  combined  in  various 
ways,  in  fluids  and  in  living  or  dead  organisms,  in  which  they  produce 
decompositions  and  fermentations,  but  not  alcoholic  fermentation. 

Among  these  organisms  are  included  bacteria,  bacilli,  vibrios,  etc.,  but 
comparatively  few  of  these  have  an  immediate  bearing  on  the  present 
subject,  and  so  the  great  majority  need  not  here  be  described. 


a,  Cocci ; b,  Diplococci  and  Sarcina  ; c.  Streptococci ; d,  Zoogloea  ; e,  Bacteria  and  Bacilli ; /,  Clostridium  ; 
g,  Pseudo-ftlament,  Leptothrix,  Cladothrix ; h.  Vibrio,  Spirillum  Spirochsete,  [and  Spirulina ; t,  Involution- 
forms  ; k.  Bacilli  and  Spirilla,  with  cilia  or  flagella ; I,  Spore-forming  Bacteria ; m,  Germination  of  the  Spore. 

The  difficulty  of  classifying  the  Schizomycetes  increases  with  a more 
minute  acquaintance  with  these  organisms,  as  investigation  shows  that 
one  and  the  same  organism  occurs  in  varying  forms  under  different  con- 
ditions. Some  of  the  various  growth-forms  are  illustrated  in  Fig. 
16.  If,  on  the  other  hand,  grouped  according  to  the  chemical  changes 
they  produce,  then  in  many  mstances  more  than  one  organism  is  found 
capable  of  inducing  the  same  chemical  reaction.  For  the  purposes  of 
the  present  work,  it  will  be  more  convenient  to  accept  provisionally  a 
classification  according  to  chemical  effects  produced. 

The  Schizomycetes  possess  the  property  of  surrounding  themselves  with 

182 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  183 


a gelatinous  substance,  in  which  large  colonies  of  them  may  be  seen  im- 
bedded. They  are  then  said  to  be  in  the  “ Zoogloea  ''  stage. 

334.  Bacteria. — ^These  organisms  consist  of  small  cells,  commonly 
cylindrical  in  shape  ; they  increase  by  transverse  divisions  of  cells,  and 
reproduce  by  sporulation.  Bacteria  have  a spontaneous  power  of  move- 
ment. 


Organisms  of  Putrefaction. 

335.  Bacterium  Termo. — ^This  is  essentially  the  ferment  of  putrefaction. 
It  is  present  in  air,  and  also  in  waters  contaminated  with  sewage.  Hay, 
meat,  or  flour  infusions,  malt  wort  and  other  liquids,  on  being  exposed 
to  the  atmosphere,  become  turbid,  and  are  then  found  on  microscopic 
examination  to  be  densely  crowded  with  bacteria.  The  cells  are  oval  in 
shape  and  about  1*5  to  2 mkms.  in  length  : they  are  constricted  in  the 
middle,  giving  them  a sort  of  hour-glass  appearance  ; at  each  end  is  an 
extremely  fine  filament,  termed  a “ flagellum,”  and  sometimes  a “ cilium.” 
This  is  probably  the  organ  by  which  the  bacterium  exerts  its  motile  or 
moving  power.  For  illustrations  of  this  and  other  forms  of  bacteria  see 
Plate  V. 

This  definite  movement  of  the  bacterium  must  not  be  confounded  with 
the  simple  oscillatory  movement  of  small  particles  of  matter  when  sus- 
pended in  a fluid.  This  latter  may  be  observed  by  rubbing  up  a little 
gamboge  in  water,  and  microscopically  examining  a drop  of  the  liquid  : 
the  small  solid  particles  are  seen  to  be  in  a continual  state  of  motion.  This 
latter  is  termed  the  “ Brownian  ” movement. 

The  spores  of  the  bacteria,  in  common  with  most  other  of  those  of  the- 
schizomycetes,  are  extremely  tenacious  of  life.  They  may  be  dried  up 
and  exist  in  a dormant  state  for  an  indefinite  time  without  losing  their 
vitality  ; for  immediately  on  being  again  moistened  and  placed  in  a suitable 
medium,  they  commence  an  active  existence  and  cause  putrefaction.  The 
dry  spores  are  not  destroyed  by  even  boiling  them  for  so  long  as  a quarter 
of  an  hour  ; they  are  also  not  affected  by  weak  acids. 

336.  Bacilli. — ^The  word  bacillus  literally  means  a stick  or  rod,  and 
is  applied  to  the  organisms  of  this  genus  because  of  their  rod-like  shape.. 
The  cells  are  long  and  cylindrical  and  occur  attached  to  each  other,  thus 
forming  rod-like  filaments  of  considerable  length.  There  is  little  or  no 
constriction  at  the  joints,  which  with  low  microscopic  powers  are  scarcely 
observable.  They  increase  by  splitting  transversely,  and  reproduce  by 
spores.  Bacteria  and  bacilli  are  closely  allied  genera,  some  species  of  the 
one  closely  resembling  species  of  the  other.  In  the  very  long  cells  of  bacteria 
the  transverse  divisions  may  be  detected,  while  in  the  equally  long  cells 
of  bacilli  no  traces  of  division  can  be  seen.  Bacilli  are  sometimes  motile, 
but  after  a time  pass  into  a condition  of  rest,  or  zoogloea  stage.  The  long 
threads  of  bacilli  often  assume  a zig-zag  or  bent  form  ; and  unless  sub- 
jected to  very  careful  examination,  appear  to  be  continuous.  Pasteur's 
filaments  of  turned  beer  “ consist  of  bacilli.” 

337.  Bacillus  Subtilis. — ^This  organism  is  also  termed  “ Vibrio  subtilis,” 
and  is  largely  present  in  air.  Owing  to  its  being  the  predominant  organism 
produced  when  an  aqueous  infusion  of  hay  is  exposed  to  the  air,  it  is  fre* 
quently  referred  to  as  the  bacillus  of  hay.  The  cells  are  cylindrical,  and 
grow  to  about  6 mkms.  in  length,  and  are  provided  with  a fiagellum  at 
either  end.  They  usually  occur  adherent  to  each  other,  forming  long 
filaments,  as  shown  in  Plate  V. 


Plate  V 


Fig.  1 


Fig.  2 , 


Ch  PcLSVeur  b IdhtPienvs  Sr  Lott. 


Fig:  5 . 


F^. 


BacxPbae  suPuKxs  (Cohn/ ) x 650.  CLostriPbCarri/  hwtyri/xvnv  (PraffrrujwPou)  x 650  (oJboat/)^- 

Various  Disease  Ferments. 


18 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  185 


The  term  “ vibrio,”  applied  to  certain  forms  of  schizomycetes,  is  derived 
from  their  appearing  to  have  a wriggling  or  undulatory  motion  ; this 
•effect  is  illusory,  being  actually  caused  by  their  rotating  on  their  long  axis. 
An  enlarged  illustration  of  B.  suhtilis  is  given  in  the  following  figure,  17. 


Fig.  17. — Bacillus  suhtilis  X 4000  (after  Ballinger). 


They  increase  by  transverse  division,  and  reproduce  by  spores.  As  the 
spore  formation  of  B.  suhtilis  has  been  most  carefully  observed,  a descrip- 
tion of  its  mode  of  reproduction  will  be  of  service  as  a type  of  that  of  the 
schizomycetes  generally.  In  spore  formation  the  protoplasmic  contents 
of  the  cell  accumulate  at  the  one  end,  causing  an  enlargement  there  ; the 
rest  of  the  cell  after  a time  drops  off  and  dies  ; the  mature  spore  may  then 
live  for  even  years  without  losing  its  vitality  ; and  being  of  extreme  minute- 
ness, these  spores  permeate  the  atmosphere,  and  are  ever  ready  to  germinate 
on  finding  a suitable  medium.  In  the  act  of  germination  the  spore  splits 
its  membrane  open,  and  a new  rod  grows  and  projects  through  the  opening. 
The  dry  spores  are  extremely  tenacious  of  life,  and  withstand  boiling  for  an 
hour  in  water  without  losing  their  vitality.  Some  three  or  four  consecu- 
tive boilings  in  a flask  plugged  with  cotton- wool,  with  a few  hours’  interval 
between,  are  necessary  to  ensure  sterilisation  from  this  organism. 

Various  writers  impute  different  specific  fermentative  actions  to  B. 
subtilis,  but  it  is  doubtful  whether  the  production  of  any  particular  chemical 
compound  should  be  associated  with  it.  It  is  essentially  the  organism 
of  putrefaction,  and  effects  the  decomposition  both  of  nitrogenous  and 
carbonaceous  bodies  with  the  evolution  of  mal-odorous  gases.  Both  it 
and  B.  termo  are  stated  to  possess  the  power  of  peptonising  proteins,  this 
operation  being  a preliminary  to  their  further  conversion  into  leucin,  tyrosin, 
and  allied  bodies. 

338.  Diastatic  Action  of  Bacteria. — ^This  latter  action  is  a consequence 
of  the  property  possessed  by  the  bacteria  of  attacking  protein  bodies  and 
eon  verting  them  into  peptones.  Wortmann  has  devoted  considerable 
attention  to  the  investigation  of  the  problem  whether  or  not  bacteria  have 
any  action  on  starch  : whether  or  not,  by  the  secretion  of  a starch-trans- 
lorming  substance  similar  to  diastase,  or  in  any  other  but  not  clearly  defined 
way,  they  are  capable  of  transforming  starch  into  soluble  and  diffusible 
•compounds.  In  order  if  possible  to  obtain  a solution  of  this  problem, 
Wortmann  experimented  in  the  following  manner  : — 

To  about  20  or  25  c.c.  of  water  a mixture  of  inorganic  salts  (sodium 
•chloride,  magnesium  sulphate,  potassium  nitrate,  and  acid  ammonium 
phosphate,  in  equal  proportions)  was  added  to  the  extent  of  I per  cent. 
The  same  quantity  of  solid  wheat-starch  was  next  added,  and  the  liquid 
then  inoculated  with  one  or  two  drops  of  a strongly  bacterial  solution  ; 
shaken,  corked,  and  allowed  to  remain  in  a room  at  a temperature  of  18° 
to  22°  C.  {Bacterium  termo  was  the  predominating  organism  in  the  inocu- 
lating fluids  employed.)  In  from  five  to  seven  days,  the  first  signs  of 
commencing  corrosion  of  the  starch  granules  had  become  visible,  the  larger 
grains  being  first  attacked,  and  much  later,  when  these  had  almost  com- 
pletely disappeared,  those  of  lesser  size. 

In  a second  series  of  experiments,  soluble  starch  was  substituted  for 


186 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  solid  form,  the  progress  of  the  reaction  being  watched  by  the  aid  of 
iodine.  Samples  taken  from  time  to  time  exhibited  at  first  the  blue  colour, 
then  violet  or  dark  red,  passing  to  wine  red,  and  finally,  when  the  starch 
had  disappeared,  underwent  no  change. 

Wlieat-starch  gvains  are  found  to  be  by  far  the  most  readily  attacked 
by  bacteria  when  compared  with  other  varieties,  in  several  experiments 
having  even  completely  disappeared  before  other  sorts  of  starch  were 
affected.  Of  a number  of  starches,  that  of  potatoes  alone  entirely  re- 
sisted attack.  When  wheat-starch  in  the  solid  state  was  mixed  with  starch 
solution  or  with  starch  paste,  the  solution  became  entirely  (and  the  paste 
in  greater  part)  changed  before  any  action  occurred  on  the  solid  granules. 

With  regard  to  this  unequal  power  of  resistance  shown  by  different 
kinds  of  starch,  Wortmann  concludes  from  his  further  observations  that 
the  difference  of  rapidity  with  which  a given  kind  is  attacked  and  dis- 
solved by  a ferment  is  inversely  proportional  to  its  density,  provided  always 
that  the  granules  in  question  are  entire  and  uninjured  by  cracks  or  fissures. 
In  the  same  way  are  explained  the  differences  in  point  of  time  in  which 
granules  of  the  same  kind  are  sometimes  observed  to  undergo  change  accord- 
ingly as  they  are  intact  or  otherwise. 

The  cause  of  potato-starch,  or  of  bean-starch,  and  even  under  certain 
conditions,  wheaten  starch,  resisting  attack,  in  spite  of  the  abundant  pres- 
ence of  bacteria,  is  apparently  to  be  sought  for  in  the  fact  that  other  more 
easily  accessible  sources  of  carbon  nutriment  were  also  present,  certain 
protein  constituents  of  the  potato  slices,  or  of  the  beans  employed  affording 
this  more  readily  than  the  starch  granules,  just  as  in  the  experiments  above 
cited,  with  wheaten  starch  solution  and  solid  wheaten  starch,  the  former 
was  preferentially  attacked  ; only  after  all,  or  at  least  the  chief  portion, 
of  the  proteins  present  had  been  used  up,  was  the  starch  in  these  cases 
attacked. 

Another  point  was  also  established  in  the  course  of  these  experiments 
— that  if  air  is  excluded,  no  appearance  of  corrosion  or  solution  of  the 
starch  granules  is  manifested. 

That  the  starch  in  the  process  became  changed  in  part  to  glucose  was 
easily  ascertained  by  testing  with  Fehling’s  solution,  and  a detailed  series 
of  experiments,  made  with  a view  to  eliminating  if  possible  the  ferment 
itself,  yielded  evidence  showing  that  bacteria  possess  the  remarkable  property 
of  producing  a starch-transforming  ferment,  only  when  no  source  of  carbon 
other  than  starch  is  at  their  disposal,  and  this  ferment  is  incapable  of  chang- 
ing albumin  into  peptone,  just  as  in  the  case  of  diastase.  The  results  of 
Wortmann's  researches  may  be  briefly  recapitulated — 

1.  Bacteria  are  capable  of  acting  on  starch,  whether  in  the  solid  state, 
as  paste,  or  in  solution,  in  a manner  analogous  to  diastase. 

2.  As  in  the  case  of  diastase,  different  kinds  of  starch  are  attacked 
by  bacteria  with  different  degrees  of  rapidity. 

3.  The  action  of  bacteria  on  starch  is  manifested  only  in  the  absence 
of  other  sources  of  carbon  nutriment,  and  when  access  of  air  is  not  pre- 
vented. 

4.  The  action  of  bacteria  on  starch  is  effected  by  a substance  secreted 
by  them,  and  which,  like  diastase,  is  soluble  in  water,  but  precipitable 
by  alcohol. 

5. *  This  substance  acts  precisely  as  diastase  in  changing  starch  into 
a sugar  capable  of  reducing  cupric  oxide,  but  is  not  possessed  of  peptonising 
properties. 

These  results  of  Wortmann's  are  quoted  at  some  length  because  of 
their  bearing  on  the  action  of  bacteria  in  dough.  One  most  important 
point  is,  that  the  diastatic  action  of  bacteria,  or  their  secretions,  only  occurs 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  187 

in  the  absence  of  protein  matter,  which  is  the  substance  most  specially 
suited  for  the  development  of  these  organisms  ; consequently,  with  the 
exception  of  the  transformation  of  sugar  more  or  less  into  lactic  acid,  the 
carbohydrates  are  unattacked  by  the  schizomycetes  during  normal  dough 
fermentation.  The  bacteria  cause  more  or  less  change  in  proteins,  but 
exert  no  diastatic  action.  These  protein  changes  are,  by  the  way,  un- 
accompanied by  any  appreciable  evolution  of  gas. 

It  will  be  noticed  that  Wortmann  expressly  states  that  the  bacteria 
have  no  peptonising  action  ; while  it  is  also  as  expressly  stated  that  they 
readily  attack  the  proteins.  He  does  not  state  what  substances  he  finds 
produced  by  this  action.  The  opinion  is,  nevertheless,  very  generally 
held  that  peptones  are  produced  during  changes  which  occur  during  the 
fermentation  of  dough,  and  it  has  been  supposed  that  the  bacteria  were 
the  active  agents.  Thus,  Peters  describes  a bacillus  which  he  found  among 
the  organisms  of  leaven  which  possesses  a peptonising  power. 

339.  Putrefactive  Fermentation. — ^Putrefaction  is  that  change  by  which 
most  organic  bodies  containing  nitrogen  in  a protein  form  are  first  resolved 
into  substances  having  a most  putrid  odour,  and  ultimately  into  inorganic 
products  of  oxidation.  Bacterium  termo  and  B.  subtilis  have  already  been 
mentioned  as  the  principal  organisms  of  putrefaction.  Pasteur  divides 
the  act  of  putrefaction  into  tw'o  distinct  stages,  which  it  will  be  well  here 
to  describe.  On  exposing  a putrescible  liquid  to  the  air,  there  forms  on 
the  surface  a film  composed  of  bacteria,  etc.  ; these  completely  exclude 
any  oxygen  from  the  liquid,  by  themselves  rapidly  absorbing  that  gas. 
Beneath,  other  more  active  organisms,  which  Pasteur  groups  together 
under  the  name  of  “ vibrios,’'  act  as  ferments  on  the  protein  matters  of 
the  liquid,  and  decompose  them  into  simpler  products  ; these  simpler 
products  are  in  their  turn  oxidised  still  further  by  the  surface  bacteria, 
Pasteur  practically  defines  putrefaction,  or  putrid  fermentation,  as  fer- 
mentation without  oxygen. 

340.  Action  of  Oxygen  on  Bacterial  and  Putrefactive  Ferments. — Pasteur 
draws  a hard  and  fast  line  between  certain  bacteria  which  he  affirms  live 
in  oxygen,  and  absolutely  require  it,  and  others  to  which  oxygen  acts  as 
a poison  ; to  which  latter  class  he  states  that  the  vibrios  belong.  This 
name  is  used  by  him  seemingly  to  refer  to  those  micro-organisms  which 
are  in  active  motion.  Of  the  bacteria  of  the  first  type,  he  mentions  that 
if  a drop  full  of  these  organisms  be  placed  on  a glass  slide,  and  examined 
with  a microscope,  there  is  soon  a cessation  of  motion  in  the  centre  of  the 
drop,  while  those  bacteria  nearest  the  edges  of  the  cover-glass  remain  in 
active  movement  in  consequence  of  the  supply  of  air.  On  the  other  hand, 
if  a drop  of  liquid  containing  the  vibrios  of  putrefactive  fermentation  be 
studied  in  a similar  way,  motion  at  once  ceases  at  the  edge  of  the  cover- 
glass  ; and,  gradually,  from  the  circumference  to  the  centre,  the  pene- 
tration of  atmospheric  oxygen  arrests  the  vitality  of  the  vibrios.  Pasteur 
thus  divides  the  bacteria  into  an  aerobian  and  an  anaerobian  variety  ; the 
former  require  oxygen,  the  latter  find  it  a poison,  and  live  and  thrive  best 
in  its  total  absence.  In  proof  of  this  view  he  describes  experiments  of  a 
most  careful  character  made  by  him. 

341.  Conditions  Inimical  to  Putrefaction. — ^First  and  foremost  among 
these  is  the  keeping  out  of  the  germs  of  putrefactive  ferments  from  the 
substance.  Meat  and  protein  bodies,  generally,  have  come  to  be  ordinarily 
viewed  as  very  changeable  substances,  whereas  in  the  absence  of  germ 
life  they  are  very  stable  bodies.  Putrefaction  is  the  concomitant,  not 
of  death  but  of  life.  If  animal  fluids  are  drawn  off  into  sterilised  vessels 


188 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


without  access  of  air,  they  keep  for  an  indefinite  length  of  time.  Or  the 
germs  may  be  destroyed  heat,  when  putrescible  substances  also  remain 
unchanged.  This  latter  is  the  basis  of  Appert's  methods  for  the  preser- 
vation of  animal  substances.  These  methods  consist  of  exposing  the 
substances  to  a sufficiently  high  temperature  in  hermetically  sealed  vessels  ; 
or  they  may  be  heated  in  vessels  so  arranged  that  air  may  escape,  but  that 
any  re-entering  shall  be  freed  from  bacterial  germs  either  by  passing  through 
a red-hot  tube,  or  by  being  filtered  through  a thick  layer  of  cotton-wool. 

Tinned  meats,  milk,  etc.,  are  preserved  on  this  principle  of  ApperCs. 

Putrefaction  may  be  arrested  by  intense  cold,  although  even  freezing 
bacteria  does  not  destroy  their  power  of  inducing  putrefaction  when  again 
warmed.  As  a consequence  of  this  action  of  cold,  meat  when  thoroughly 
frozen  may  be  preserved  almost  indefinitely.  The  absence  of  water  is 
another  preventative  of  putrefaction.  Vegetables  and  meat,  if  thoroughly 
desiccated,  show,  on  keeping,  no  signs  of  putrefying.  In  the  same  way, 
yeast,  although  in  the  moist  state  one  of  the  most  putrescible  substances 
known,  may,  by  being  carefully  dried,  be  kept  for  months,  not  merely 
without  putrefying,  but  also  without  destroying  the  life  of  the  cell. 

342.  Products  of  Putrefaction. — These  are  exceedingly  numerous  and 
complex,  among  them  may  be  found  volatile  fatty  acids,  but3n*ic,  and 
other  of  the  series  ; ammonia,  and  some  of  the  compound  or  substitu- 
tion ammonias  ; ethylamine,  trimethylamine,  propylamine,  etc.  ; carbon 
dioxide,  sulphuretted  hydrogen,  hydrogen,  and  nitrogen. 

Lactic  and  Other  Fermentations. 

343.  Lactic  Fermentation. — ^This  is  primarily  the  fermentation  by 
means  of  which  milk  becomes  sour.  The  chemical  change  is  a very  simple 
one.  Milk  contains  the  variety  of  sugar  known  as  lactose  or  sugar  of  milk, 
C12H22O11.  By  hydrolysis,  this  splits  up  into  two  molecules  of  a glucose 
called  lactose,  galactose,  or  lacto-glucose,  C6H12O6.  When  subjected  to 
the  influence  of  the  lactic  ferment,  lacto-glucose  is  decomposed  according 
to  the  following  equation  : — 

C6H12O6  = 2HC3H5O3. 

Lacto  Glucose.  Lactic  Acid. 

Ordinary  glucose,  and  also  cane-sugar  and  maltose,  are  susceptible  of 
the  same  transformation.  From  numerous  recent  researches,  there  is 
evidence  of  a number  of  organisms  which  possess  the  power  of  produc- 
ing lactic  acid  by  the  conversion  of  glucose.  One  or  more  of  these  is  always 
found  present  in  greater  or  less  quantity  in  commercial  yeasts,  also  on 
the  surface  of  malt  ; in  the  latter  case  it  may  be  detected  by  washing  a 

few  of  the  grains  in  water,  and  then 
examining  the  liquid  under  the  micro- 
scope. Its  shape,  according  to  Lister, 
when  developed  in  milk,  is  shown  in 
the  accompanying  illustration.  When 
viewed  with  a lower  power  in  a field 
of  yeast,  The  lactic  ferment  appears 
as  small  elongated  cells  somewhat 
constricted  in  the  middle,  generally 
detached,  but  occurring  sometimes  in  twos  and  threes  ; their  length  is 
about  half  that  of  an  ordinary  yeast  cell.  When  single  they  exhibit  the 
Brownian  movement. 

Lactic  fermentation  proceeds  most  favourably  at  a temperature  of 
about  35°  C.,  and  is  retarded  and  practically  arrested  at  a temperature 


Fig.  18. — Bacterium  lactis  X 1140 


(after  Lister). 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  18J> 


^A'hicli  still  permits  the  growth  and  development  of  the  yeast  organism, 
and  consequent  alcoholic  fermentation.  For  this  reason  brewers  always 
take  care  to  ferment  their  worts  at  a low  temperature,  thus  preventing 
the  lactic  ferment,  which  is  always  more  or  less  present,  from  any  rapid 
development.  The  other  bacterial  and  allied  ferments  are  also  affected 
in  a similar  manner  by  temperature.  Dilute  solutions  of  carbolic  and 
salicylic  acids  (and  also  hydrofluoric  acid)  greatly  retard  lactic  fermen- 
tation, while  in  such  very  weak  solutions  they  have  but  little  action  on 
the  yeast  organism  ; hence  yeast  is  sometimes  purified  by  being  repeatedly 
grown  in  worts,  to  vliich  small  quantities  of  these  acids  have  been  added. 
The  most  favourable  medium  for  lactic  fermentation  is  a saccharine  solu- 
tion rather  more  dilute  than  that  used  for  cultivating  yeast,  and  containing 
proteins  in  an  incipient  stage  of  decomposition.  The  analogy  between 
this  fermentation  and  the  alcoholic  is  close,  because  the  two  may  proceed 
side  by  side  in  the  same  liquid.  The  presence  of  acid  is  inimical  to  lactic 
fermentation  ; hence  the  fermentation  arrests  itself  after  a time  by  tho 
development  of  lactic  acid  ; provided  this  is  neutralised  from  time  to 
time  by  the  addition  of  carbonate  of  lime  or  magnesia,  the  fermentation 
proceeds  until  the  whole  of  the  sugar  has  disappeared.  In  a slightly  acid 
liquid,  as  for  instance  the  juice  of  the  grape,  alcoholic  fermentation  pro- 
ceeds almost  alone  ; but  with  wort,  which  is  much  more  nearly  neutral 
(if  made  with  good  malt),  lactic  fermentation  sets  in  with  readiness,  and 
consequently  has  to  be  specially  guarded  against.  Some  varieties  of  the 
lactic  acid  ferment  require  air  for  their  growth  and  development,  whilo 
others  are  anaerobic  in  their  character. 

In  addition  to  its  specific  action  on  glucose,  converting  it  into  lactic 
acid,  the  lactic  ferment  has  other  functions  of  importance  in  commercial 
operations  ; thus,  the  presence  of  lactic  ferment  germs  on  malt  result  in 
the  formation  of  a little  lactic  acid  during  the  mashing  ; in  distillers’  mashes 
this  is  found  to  be  somewhat  valuable,  and  is  encouraged,  as  it  apparently 
helps  to  effect  a more  complete  saccharification  of  the  malt,  and  conse- 
quently increases  the  yield  of  alcohol.  It  also  peptonises  the  proteins, 
bringing  them  into  a condition  more  adapted  for  the  nutrition  of  yeast. 
Distillers,  therefore,  frequently  allow  their  malts  to  develop  considerable- 
acidity  before  using  them,  find  give  new  mash  tuns  a coating  of  sour  milk 
before  bringing  them  into  use.  In  bread-making,  by  the  Scotch  system, 
the  presence  of  the  lactic  ferment  is  deemed  to  make  better  bread  : either 
the  ferment,  or  the  lactic  acid  produced,  softens  and  renders  the  gluten 
of  the  flour  more  elastic. 

Hansen’s  methods  have  been  applied  to  the  preparation  of  pure  cul- 
tivations of  lactic  ferments,  with  the  view  of  securing  a more  satisfactory 
acidification  of  cream  preparatory  to  its  being  made  into  butter.  Two 
distinct  species  have  been  isolated,  which  give  particularly  favourable 
results  in  butter-making  ; one  of  these  is  stated  by  Storch  to  give  a pure 
and  mild  slightly  sour  taste,  imparting  at  the  same  time  a very  pure  aroma 
to  the  cream  and  butter  made  therefrom.  There  are  other  lactic  acid- 
forming bacteria,  which,  on  the  contrary,  produce  diseases  in  milk  ; thus, 
one  species  causes  the  milk  to  become  viscous  at  the  same  time  as  it  under- 
goes lactic  fermentation.  Further,  certain  bacteria  induce  a tallow-like 
flavour  in  butter.  Not  only  may  we  have  a fermentation  producing  lactic 
acid  as  distinct  from  other  acids,  but  also  there  are  differentiations  in  the 
character  of  the  secondary  products  formed  at  the  same  time  as  the  lactic 
acid,  and  which  secondary  products  affect  most  vitally  the  success  or  other- 
wise of  the  particular  process  from  its  manufacturing  standpoint.  It  is 
more  than  possible  that  these  variations  in  the  nature  of  lactic  fermentation 
itself  may  have  a direct  bearing  on  the  success  of  bread-making  operations. 


190 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


344.  Butyric  Fermentation. — ^At  the  close  of  the  lactic  fermentation 
of  milk,  the  lactic  acid  or  lactic  salts,  as  the  case  may  be,  seem  to  be  acted 
on  by  ferment  organisms  and  converted  into  butyric  acid  with  the  evolution 
of  carbon  dioxide  and  hydrogen — 

2HC3H5O3  = HC4H7O2  + 2CO2  + 2H2. 

Lactic  Acid.  Butyric  Acid.  Carbon  Dioxide.  Hydrogen. 

Several  species  of  bacteria  are  capable  of  inducing  butyric  acid  fer- 
mentation. The  most  carefully  examined  among  these  is  Clostridium 
hutyricum,  known  also  as  Vibrio  butyricus,  which  occurs  in  the  form  of 
short  or  long  rods,  and  is  in  shape  and  general  appearance  very  similar 
to  B.  subtilis,  differing,  however,  from  that  organism  in  that  it  contains 
starch.  In  breweries  and  pressed  yeast  factories,  butyric  fermentation 
is  often  caused  by  organisms  of  altogether  different  type  to  C.  butyricum. 
This  particular  organism  is  anaerobic  in  character,  but  others  of  the  species 
producing  butyric  acid  are  distinctly  tolerant  of  oxygen.  The  general 
conditions  of  butyric  fermentation  are  similar  to  those  of  lactic  fermen- 
tation. A temperature  of  about  40° C.  (104° F.)  is  specially  suitable; 
the  presence  of  acids  is  to  be  avoided  ; or  w4iere  butyric  fermentation 
is  not  wished,  its  prevention  is  more  or  less  attained  by  working  at  a lower 
temperature  and  with  a slightly  acid  liquid.  However,  with  the  fully 
developed  organism,  a slight  acidity  is  unable  to  prevent  butyric  fermen- 
tation. Although  butyric  fermentation  is  usually  preceded  by  lactic 
fermentation,  the  butyric  ferment  is  also  capable  of  acting  directly  on 
sugar  itself,  and  also  on  starch,  dextrin,  and  even  cellulose. 

Tannin  has  a markedly  prejudicial  effect  on  the  growth  and  develop- 
ment of  bacterial  life,  hence  the  addition  of  this  substance,  or  any  com- 
pound containing  it,  to  a fermenting  liquid,  exercises  great  preventive 
action  on  the  development  of  lactic  and  butyric  fermentation.  Hops 
contain  tannin  as  one  of  their  constituents,  and  also  the  bitter  principles 
of  the  hop  cause  a hopped  wort  to  be  much  less  liable  to  lactic  fermentation 
than  one  unhopped.  For  a similar  reason,  bakers  add  hops  to  their  patent 
yeast  worts. 

345.  Acetic  Fermentation. — Certain  organisms  effect  the  change  of 
wine  and  beer  into  vinegar.  The  reaction  is  one  of  oxidation  of  the  alcohol 
present  : in  the  first  place,  aldehyde  is  formed,  and  then  this  body  is  oxidised 
into  acetic  acid,  according  to  the  following  equations  : — ■ 

2C2H5HO  + 02  = 2C2H4O  + 2H2O. 

Alcohol.  Oxygen.  Aldehyde.  Water. 

2C2H40  + 02  = 2HC2H3O2. 

Aldehyde.  Oxygen.  Acetic  Acid. 

Pasteur  described  under  the  name  of  My  coderma  aceti  an  organism 
through  whose  agency  alcohol  is  oxidised  into  acetic  acid.  Hansen  has 
detected  two  distinct  species  under  this  name,  distinguished  by  the  one 
staining  yellow,  and  the  other  blue,  with  iodine  solution.  Both  possess 
the  same  chemical  properties,  and  in  order  to  develop  vigorously  require 
a plentiful  supply  of  oxygen.  They  are,  in  fact,  strictly  aerobic.  A tem- 
perature of  about  33°  C.  is  the  most  favourable  to  the  production  of  acetic 
fermentation.  Bacterium  aceti  also  converts  propyl  alcohol  into  propionic 
acid,  but  is  without  action  on  either  butyl  alcohol  or  the  amyl  alcohol 
of  fermentation. 

Bacterium  aceti  forms  a mycelium  on  the  surface  of  liquids,  pos- 
sessing a certain  amount  of  tenacity  : viewed  under  the  microscope,  this 
mycelium  is  seen  to  consist  of  chains  of  cells,  as  shown  in  Plate  V. 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  191 


In  the  substance  known  as  “ mother  of  vinegar  ” or  the  vinegar  plant, 
long  supposed  to  be  identical  with  B.  aceti,  A.  J.  Brown  discovered  a separ- 
u,te  organism,  which,  in  addition  to  producing  acetic  acid,  is  also  marked 
by  the  property  of  causing  the  formation  of  cellulose  ; to  this  he  has  given 
the  name  of  Bacterium  xylinum. 

Peters  has  discovered  in  extremely  old  and  sour  leaven  an  acetic  acid 
bacterium,  distinct  from  those  just  described.  The  individuals  are  about 
1 *6  /X  long,  and  0 *8  /x  broad,  truncated  at  one  end,  and  tapering  at  the  other. 
Interest  attaches  to  the  isolation  of  this  specific  organism,  inasmuch  as  a 
small  proportion  of  the  acidity  of  bread  is  due  to  acetic  acid. 

K temperature  below  18°  C.  is  almost  inhibitory  to  the  action  of  the 
acetic  acid  ferment,  while  most  antiseptics,  and  especially  sulphur  dioxide, 
are  exceedingly  inimical  to  acetous  fermentation. 

Jorgensen  remarks  that  “ an  important  advance  was  made  in  our  know- 
ledge of  acetic  bacteria  when  Buchner  and  Meisenheimer,  as  well  as  Herzog, 
proved  that  this  remarkable  fermentation  is  brought  about  by  the  activity 
of  an  enzyme.  The  cells  may  be  killed  with  acetone,  and  then  treated 
in  the  same  way  as  the  alcohol  yeasts  (see  Chapter  IX. , paragraph  289),  and  it 
can  then  be  shown  that,  after  evaporating  the  liquid,  the  residue  can  bring 
about  the  acetic  fermentation,  although  it  contains  no  living  cells.  By 
this  discovery  the  real  nature  of  the  fermentation  becomes  clear.  Like 
the  alcoholic  fermentation,  it  is  caused  by  an  enzyme,  which  may  react 
independently  of  the  living  cell  that  brought  it  into  existence."’  (Micro- 
organ'sms  and  Fermentation,  Fourth  English  Edition.) 

346.  Viscous  Fermentation. — ^Viscous  fermentation  is  that  variety 
-which  causes  “ ropy  beer.”  Pasteur  supposed  this  to  be  due  to  an  organism 
consisting  of  globular  cells  of  from  1*2  to  1*4  /x  in  diameter,  adhering  to- 
gether in  long  chains.  Moritz  and  Morris,  who  have  devoted  particular 
attention  to  this  subject,  disagree  with  Pasteur’s  views,  and  ascribe  ropi- 
ness principally  to  a ferment  known  as  Pediococcus  cerevisice.  This  organism 
occurs  either  in  pairs  of  cells  or  tetrads  (i.e.,  four  cells  arranged  in  the  corners 
of  a square),  diameter  of  each  cell  being  0-9-1 -5  /X-  These  organisms 
are  similar  in  appearance  to  those  marked  b,  Fig.  15.  Beer,  after  haviiig 
undergone  this  fermentation,  runs  from  the  tap  in  a thick  stream  ; and 
in  very  bad  cases,  a little,  when  placed  between  the  fingers,  pulls  out  into 
strings. 

A somewhat  similar  condition  sometimes  holds  in  bread,  which  then  is 
termed  ropy  bread  ; this  is  discussed  very  fully  in  Chapter  XVIII. 

347.  Disease  Ferments. — ^The  ferments  of  lactic,  viscous,  and  other 
than  alcoholic  fermentation,  are  frequently  called  “ disease  ferments,” 
from  their  producing  unhealthy  or  diseased  fermentations  in  beer. 

348.  Spontaneous  Fermentation. — ^In  this  country,  alcoholic  fermenta- 
tion is  usually  started  by  the  addition  of  more  or  less  yeast  from  a previous 
brewing  ; it  was  formerly  the  custom  to  allow  the  fermentation  to  start 
of  itself.  This  is  said  still  to  be  practised  in  some  parts  of  Belgium  in  the 
manufacture  of  a variety  of  beer,  known  as  “ Faro  ” beer.  In  manu- 
facturing such  beers,  the  vats  of  wort  are  allowed  to  remain  exposed  to 
the  air,  and  fermentation  is  excited  by  any  germs  of  yeast  that  may  find 
their  way  therein.  It  is  possible  that  under  such  circumstances  a wort 
may  only  be  impregnated  by  yeast  germs,  in  which  case  pure  alcoholic 
fermentation  alone  will  be  set  up.  It  is  far  more  likely,  however,  that 
germs  of  lactic  ferment  and  other  organisms  will  also  get  into  the  wort  ; 
consequently  the  beer  will  be  hard  or  sour,  and  also  likely  to  speedily  be- 


192 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


come  unsound.  On  the  other  hand,  grape  juice  is  always  allowed  to  fer^ 
ment  spontaneously,  but  then  this  liquid  is  distinctly  acid,  through  the 
presence  of  potassium  bitartrate  ; and  acidity  retards  or  prevents 
bacterial  fermentation. 

Bakers’  barms  or  patent  yeasts  are  at  times  allowed  to  ferment  spon- 
taneously ; they  are  then  found  to  contain  a large  proportion  of  foreign 
organisms,  principally  the  lactic  ferment.  Except  where  very  special 
precautions  are  adopted,  they  are  liable  to  be  uncertain  in  their  action, 
and  often  produce  sour  bread. 

But  in  all  cases  of  so-called  “ spontaneous  ” fermentation  it  must  be 
remembered  that  the  fermentation  is  due  to  the  presence  in  the  wort  of 
yeast  cells  or  spores  that  either  have  been  introduced  along  with  the  malt 
and  hops  without  being  destroyed,  or  else  have  found  their  way  into  the 
wort  from  some  external  source,  such  as  germs  floating  in  the  air.  It  is 
also  frequently  possible  that  a sufficient  quantity  of  yeast  remains  about 
the  fermenting  vessel  from  the  last  brewing  to  again  start  fermentation. 

Moulds  and  Fungoid  Growths. 

349.  The  nature  of  these  has  been  already  referred  to  in  Chapter  IX. 
and  the  mould  of  beer,  Mycoderma  cerevisice,  described  and  its  properties 
explained.  The  moulds  are  all  of  them  members  of  the  fungus  family.  A 
few  other  varieties,  because  of  their  having  more  or  less  connection  with 
the  subject  of  this  work,  requires  description. 

350.  Penicillium  Glaucum. — This  is  the  ordinary  green  mould  of  bread 
jam,  etc.  The  base  of  this  consists  of  a mycelium  bearing  both  submerged 
and  aerial  hyphse.  The  upper  ends  of  the  aerial  hyphsc  terminate  in  a 
string  of  conidia  or  spores,  which  break  off  on  the  slightest  touch  ; these 
constitute  the  green  powder  which  gives  this  mould  its  characteristic  appear- 
ance. One  of  these  spores,  on  being  sowti  in  an  appropriate  medium,  as 
hay  infusion  or  Pasteur’s  fluid,  germinates  and  produces  a young  'penicillium. 
The  conidia  retain  their  vitality  for  a long  time,  and  from  their  extreme 
minuteness  are  readily  carried  about  by  the  air  ; hence  substances  that 
offer  a suitable  medium  for  the  growth  and  development  of  moulds,  become 
impregnated  on  being  exposed  to  the  atmosphere. 

Under  favourable  circumstances  penicillium  developes  with  extreme 
rapidity  ; some  few  years  since  the  barrack  bread  at  Paris  was  attacked 
by  this  fungus,  a few  hours  was  sufficient  for  its  development,  and  the 
mould  was  in  active  growth  almost  before  the  bread  was  cold.  It  is  stated 
that  the  spores  of  this  species  are  capable  of  withstanding  the  heat  of  boiling 
water,  so  that  the  act  of  baking  an  infested  flour  would  not  necessarily 
destroy  the  spores. 

351.  Aspergillus  Glaucus. — This  is  another  mould  very  similar  to 
penicillium  in  appearance  and  colour,  but  having  at  the  ends  of  its  hyphse 
small  globose  bodies  containing  the  spores  ; these  bodies  being  termed 
sporangia. 

352.  Mucor  Mucedo. — This  mould  develops  well  on  the  surface  of  fresh 
horse  dung  ; this  substance,  if  kept  warm,  will  be  found  after  two  or  three 
days  covered  with  white  filaments,  these  being  the  hyphse,  and  terminating 
in  rounded  heads  or  sporangia.  In  form  M.  mucedo  somewhat  resembles 
A.  glaucus,  but  is  distinguished  from  it  by  having  a whitish  aspect,  A. 
glaucus  being  of  a greenish  colour. 

353.  Micrococcus  Prodigiosus. — This  organism  consists  of  round  or 


BACTERIAL  AND  PUFREFACTIVE  FERMENTATIONS.  193 


oval  cells,  from  0*1  to  I mkm.  diameter. 
These  are  at  first  colourless,  but  gradually 
assume  a blood-red  tint  : they  grow  on  wheat- 
bread,  starch  paste,  etc.  M.  prodigiosus  is  the 
cause  of  the  appearance  known  as  blood-rain 
occasionally  seen  on  bread  : at  times  the 
growths  proceed  so  far  as  to  produce  dripping 
blood-red  patches  on  the  bread. 


£ 


Fig,  19. — Micrococcus 
prodigiosus,  Cohn  X 1200 
(from  nature). 


354.  Red  Spots  in  Bread. — ^A  phenome- 
non sometimes  confused  with  the  effect 
of  M.  prodigiosus,  but  nevertheless  quite  distinct  therefrom,  is  that 
of  intensely  red-coloured  spots  in  freshly  baked  bread.  These  are  so 
bright  as  to  lead  to  the  suspicion  that  concentrated  tincture  of  cochineal 
or  other  powerful  dye  had  by  accident  got  on  to  the  dough  and  been  baked 
with  it.  Fortunately  for  the  baker,  the  occurrence  of  these  spots  is  rare, 
and  consequently  there  are  few  opportunities  of  minutely  investigating 
them.  So  far  as  the  authors'  experience  goes,  the  spots  occur  most  fre- 
quently in  bread  made  from  flour  of  the  very  highest  class,  such  as  Hun- 
garian patents  : they  have  also  seen  them  in  bread  containing  a large 
admixture  of  Oregon  flours.  The  spots  in  bread  do  not  increase  in  size  as 
the  bread  grows  old,  nor  are  they  apparently  associated  with  any  change 
in  its  constituents  : there  are  no  signs,  in  fact,  of  the  colouration  being 
due  to  the  presence  of  any  living  and  multiplying  organism.  It  is  exceed- 
ingly difficult  to  obtain  specimens  of  the  colour  spots  in  unbaked  dough, 
and  only  on  one  occasion  has  such  a specimen  come  into  the  hands  of  one 
of  the  authors.  In  that  case  a small  patch  of  dough  was  sent  him  while 
absent  from  home,  and  was  only  examined  by  him  on  his  return  after  two 
days.  The  dough  had  then  got  a slight  dry  skin  on,  but  there  were  no  signs 
of  any  growth  or  spreading  in  the  dough  ; so  far,  therefore,  as  any  con- 
clusion may  be  drawn  from  this,  it  is  against  the  source  of  colour  being 
any  organism  developing  in  the  dough.  Careful  microscopic  examination 
of  coloured  portions  of  the  bread  show  in  the  fainter  spots  that  while  the 
starch  is  uncoloured,  there  is  a red  dyeing  of  the  gluten.  In  the  larger 
and  darker  spots  there  may  be  sometimes  seen  by  the  naked  eye  a nucleus, 
which  is  so  dark  in  colour  as  to  be  almost  black.  On  breaking  down  a 
little  of  this  nucleus  with  water,  and  examining  microscopically,  the  author 
has  invariably  found  fragments  of  the  outer  integument  of  the  grain.  Among 
these  have  been  detected  portions  of  the  outside  layer  of  bran,  showing 
its  characteristic  markings,  and  also  hairs  of  the  beard  of  the  wheat,  all 
of  which  are  intensely  coloured.  In  one  sample,  only  cursorily  examined 
some  years  ago,  a number  of  filaments  somewhat  similar  to  cotton- wool 
were  observed,  but  not  identified  ; these,  too,  were  coloured  a very  deep 
red.  No  signs  of  fungus  spores  or  other  special  organisms  were  observable, 
but  spores  might  possibly  be  crushed  in  the  breaking  down  with  water. 
The  lack  of  material  for  purposes  of  further  examination  has  prevented  the 
author  from  carrying  these  investigations  beyond  this  point,  and  such  tests 
as  are  here  recorded  were  made  a number  of  years  ago.  The  most  probable 
cause  of  the  colour  is  its  deposit  on  the  outside  of  the  grain  after  its  removal 
from  the  husk  and  prior  to  its  being  milled.  It  is  suggested  as  its  possible 
source  either  some  insect  of  the  cochineal  species,  or  an  intensely  coloured 
microscopic  vegetable  growth,  such  as  a mould.  These  minute  particles 
of  outer  bran  carrying  the  colour  on  the  surface  are  sufficiently  fine  to 
pass  through  the  dressing  silks,  and  so  get  into  the  flour.  They  would  be 
so  small  as  to  be  perfectly  invisible  in  any  ordinary  examination  by  the 
naked  eye.  On  being  wetted  the  colour  spreads  and  stains  the  surrounding 


194 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gluten,  hence  the  colour  in  the  dough,  which  remains  also  and  is  seen  most 
distinctly  in  the  baked  bread. 

355.  Musty  and  Mouldy  Bread. — ^Mouldiness  may  be  very  often  noticed 
in  bread  which  has  been  kept  for  a few  days  : at  times  a loaf  of  one  day's 
production  will  remain  quite  sound,  while  another  will  rapidly  become 
mouldy.  The  Analyst,  October,  1885,  contains  an  article  by  Percy  Smith, 
giving  an  account  of  some  experiments  made  by  him  on  musty  bread. 
The  bread  when  new  had  no  disagreeable  taste,  but  on  the  second  day 
had  become  uneatable.  Smith  made  a series  of  experiments,  among  Avhich 
were  the  following  : — 

(а)  Musty  bread,  one  day  old,  soaked  in  v ater,  enclosed  between  watch 

glasses. 

(б)  Flour  from  which  the  bread  was  made,  similarly  treated. 

In  six  days  a had  begun  to  turn  yellow,  emitted  a disagreeable  odour, 
and  began  to  assume  a moist  cheesy  consistency  and  appearance.  This 
portion  was  found  to  be  swarming  with  bacteria.  On  6,  mucor  muceclo 
grew  in  abundance  ; the  flour  ultimately  dried  up  without  further  change. 

(c)  Sweet  bread  similarly  treated. 

Aspergillus  glaucus  appears,  but  no  mucor,  neither  does  the  bread  become 
cheesy  nor  evolve  odour  of  musty  bread.  The  following  are  Smith's  con- 
clusions based  on  these  and  other  experiments. 

“ Ordinary  bread  turns  mouldy  owing  to  the  growth  of  A.  glaucus. 
Musty  bread,  on  the  other  hand,  yields  both  A.  glaucus  and  M.  mucedo, 
and  then  undergoes  putrefactive  decomposition,  becoming  the  home  of 
vibriones  and  bacteria.  These  organisms,  of  course,  can  have  nothing  to 
do  with  the  mustiness  ; they  only  flourish  because  there  is  a suitable  nidus 
for 'their  growth.  It  is,  however,  curious  that  the  musty  bread  should 
decay  while  the  sweet  bread  should  not,  whilst  the  only  apparent  difference 
between  them  is  in  the  growth  of  M.  mucedo.  The  suspected  flour  pro- 
duces an  abundant  crop  of  mucor,  but  does  not  decay.  This  is  no  doubt 
due  to  the  fact  that  starch  is  not  so  suitable  a nidus  as  is  dextrin  for  bacteria. 
Perfectly  pure  flour  failed  to  decompose  when  kept  between  watch  glasses, 
but  when  placed  in  a damp  cellar  readily  became  musty,  and  produced  a 
crop  of  M.  mucedo.”  He  further  concludes  that  this  fungus  is  the  cause 
of  the  mustiness  in  the  cases  cited,  although  other  species  may  possess 
similar  properties.  When  the  flour  was  baked  into  bread,  the  assimilation 
of  moisture  regenerated  the  fungus,  thus  causing  the  bread  to  become  musty, 
for  which  result  it  is  not  necessary  for  the  plant  to  arrive  at  maturity  ; 
the  disagreeable  taste  being  developed  as  soon  as  flocci  are  visible  under 
the  microscope.  Mucor  has  apparently  a specific  chemical  action  on  bread 
that  is  not  possessed  by  Aspergillus  glaucus. 

Hebebrand  has  recently  published  the  results  of  some  investigations 
on  mouldy  bread.  He  infected  some  samples  of  rye  bread  from  mouldy 
bread,  the  organisms  being  chiefly  Penicillium  glaucum  and  Mucor  mucedo. 
These  were  kept  for  periods  of  seven  and  fourteen  days,  and  similar  samples 
at  once  dried  for  analysis.  The  results  showed  that  the  mould  caused 
a considerable  loss  of  substance,  carboliydrate  being  converted  into  water 
and  carbon  dioxide.  There  was  only  a slight  loss  of  proteins,  but  the 
loss  of  carbohydrates  caused  the  percentage  of  proteins  to  appear  much 
higher  in  the  dry  substance  of  the  mouldy  bread.  The  decomposed  protein 
was  converted  into  amides.  The  following  numbers  show  the  percentage 
composition  (1)  of  dried  fresh  bread,  and  (2)  of  the  dried  mouldy  bread  : — 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  195 


No.  l.  No.  2. 


Protein,  Insoluble  . . 

9*75  per  cent. 

9-77  per  cent. 

,,  Soluble 

1-92 

5-15. 

Maltose 

1*54 

5) 

0-50 

Dextrin 

8-02 

?? 

11-86 

Starch 

. . 76-75 

63-52 

Fat  . . 

. . 0-26 

55 

2-II  „ ( 

Ash 

1-44 

55 

2-41 

Crude  Fibre . . 

. . 0-05 

55 

2-47 

356.  Diseases  of  Cereals. — Certain  disea  ses  to  which  the  cereal  plants 
are  subject  are  due  to  parasitic  fungoid  growths.  Among  these  are  mildew, 
smut,  bunt,  and  ergot.  Their  nature  may  briefly  be  considered  at  this 
stage  of  our  work. 

357.  Mildew. — ^To  the  farmer  this  blight  is  unhappily  too  familiar  ; if 
a wheat  field  be  examined  in  May  or  June,  a greater  or  less  number  of  the 
plants  will  appear  as  though  some  of  the  lower  leaves  had  become  rusty  ; 
at  the  same  time  the  leaves  are  sickly  and  atrophied.  As  the  disease  develops 
the  number  of  rusty  leaves  increases  ; the  “ rust ""  itself  will  be  found  on 
examination  to  consist  of  the  spores  of  a fungus,  known  as  the  Puccinia 
graminis  or  corn  mildew.  The  mycelium  penetrates  the  tissues  of  the 
leaves,  occupying  the  intercellular  spaces,  and  thus  gradually  destroys 
them,  with  the  effect  of  seriously  injuring  and  reducing  the  corn  crop. 

Shutt  collected  by  hand  on  the  same  day  in  the  same  field  samples 
of  rust-free  and  rust-attacked  wheat.  The  former  have  a normal  ear  both 
as  to  size  and  colour,  and  a plump,  well-filled  grain.  The  straw  of  the 
latter  showed  many  spots  of  infection,  while  the  ears  were  smaller  than 
normal  and  the  grains  light  and  much  shrivelled.  The  following  are  the 
results  of  analysis  of  the  two  samples  of  wheat  : — 


E-ust-free.  Eusted. 


Weight  of  100  grains  in  grams  . . 

3-0504 

1-49 

Water  per  cent. 

. . 12-26 

10-66 

Crude  Protein  ,, 

. . 10-50 

13-69 

Crude  Fat  ,, 

. . 2-56 

2-35 

Carbohydrates  ,, 

. . 70-55 

68-03 

Fibre  ,, 

2-29 

3-03 

Mineral  Matter  ,, 

1-84 

2-24 

The  protein  is  considerably  higher  in  the  rusted  grain,  a result  probably 
due  to  the  fact  that  protein  is  first  lodged  in  the  grain  during  the  processes 
of  metabolism,  and  afterward  the  carbohydrates.  A result  of  rust  attack 
is  that  the  maturation  of  the  grain  is  retarded,  and  the  lodgment  of  starch 
is  incomplete.  But  though  the  total  protein  is  high,  the  wheat  will  probably 
be  found  to  be  lacking  in  strength  [Jour.  Amer.  Chem.  Soc.,  1905,  366). 

358.  Smut. — ^This  disease  is  also  known  as  “ dust  brand,”  “ chimney 
sweeper,”  and  by  other  names  all  referring  to  the  black  appearance  of 
ears  of  grain  infested  by  it.  When  the  grain  is  nearly  ripe,  there  will  be 
noticed  here  and  there  in  a wheat  field  shrivelled  looking  ears,  which  look 
as  though  covered  with  soot.  Smut  is  due  to  a fungus  which  has  received 
the  name  of  Ustilago  segetum.  The  fungus  develops  within  the  seeds, 
destroying  the  contents  of  the  grain,  and  replacing  them  by  a mass  of  spores 
which  appear  as  a fine  brownish  black  powder.  Smut  is  a very  destructive 
parasite,  and  attacks  barley,  oats,  and  rye,  and  also,  although  to  a some- 
what lesser  extent,  wheat.  Viewed  microscopically,  the  spores  of  U . 


196 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

segetuTU  are  found  to  be  spherical,  and  to  have  a diameter  of  about  8 inkms.  ^ 
their  appearance  is  shown  in  the  following  figure. 


Fig.  20. — a.  Smut,  h,  Buxt  X 400  diameters. 

359.  Bunt  or  Stinking  Rust.— Unlike  smut,  bunt  produces  no  external 
signs  of  its  presence  in  a wheat  field  : there  is  no  sooty  appearance  o ® 
ear,  nor  any  rust  above  the  leaves.  It  is  not  until  the  wheat  is  ^ 

from  the  straw  that  the  bunted  grains  are  discovered  in  the  sample.  x er 
nally,  these  grains  are  plumper  than  those  which  are  sound  ; but  on  tnem 
being  broken,  the  interior,  instead  of  being  white  and  fiour-bke  is  louna 
to  be  filled  with  a black  powder,  having  a greasy  feel  when  rubbed  between 
the  fingers,  and  a most  foetid  and  unpleasant  odour.  This  dust  consists 
of  the  spores  of  a fungus  termed  Tilletea  caries,  mixed  with  portions  ot 
its  mycelium.  The  spores  are  much  larger  than  those  of  smut,  and,  viewed 
under  the  miscroscope,  appear  as  shown  in  Fig.  20  : they  are  about  17 
mkms.  in  diameter. 

The  presence  of  bunt  is  said  not  to  affect  the  wholesomeness  ot  Hour  ; 
it  is  stated  that  bunted  flour  is  at  times  made  up  into  gingerbread  ; the 
other  condiments  used  masking  its  colour  and  odour.  With  the  extreme 
care  manifested  in  modern  systems  of  milling,  it  is  improbable  that  bun 
often  finds  its  way  into  the  flour. 

360.  Ergot.— This  disease  is  almost  exclusively  confined  to  rye  ; like 
bunt  and  smut,  ergot  is  due  to  a fungus  which  develops  within  the  gram, 
filling  its  interior  with  a compact  mass  of  mycelium  and  spores,  and  altering 
the  starch  cells  by  replacing  the  amylose  with  a peculiar  oily  matter,  ihis 
fungus  is  termed  Oidium  ahortifaciens.  The  ergotised  grams  are  violet- 
brown  or  black  in  colour,  moderately  brittle  ; and  when  m quantity  evolve 
a peculiar  nauseous  fishy  odour,  due  to  the  presence  of  trimethylamme. 
Ergot  possesses  powerful  medicinal  effects,  and  when  taken  m anything 
over  medicinal  doses,  acts  as  a violent  poison.  The  presence  of  ergo  m 
flour  is  tlierefore  extremely  dangerous.  . . 

Chemical  tests  for  the  detection  of  ergot  and  moulds  will  be  given  in 
the  analytic  section  of  this  work. 

Experimental*  Work. 

361.  Prepare  some  malt  wort;  filter  and  allow  the  liquid  to  remain 
for  some  days  in  an  open  flask.  In  about  24  hours  the  liquid  becomes 


BACTERIAL  AND  PUTREFACTIVE  FERMENTATIONS.  197 


turbid  ; examine  a drop  under  the  microscope  with  the  highest  power  at 
disposal.  Bacteria  will  be  seen  in  abundance  ; notice  that  they  have  a 
distinct  migratory  movement.  Examine  a sample  each  day,  and  observe 
that  the  bacteria  grow  less  active,  and  ultimately  become  motionless  ; 
they  have  then  assumed  the  zoogloea  stage.  Carefully  search  the  liquid 
for  other  organisms  ; bacilli  should  be  detected,  being  recognised  by  their 
filamentous  appearance.  Vibrios  should  also  be  observed  ; they  appear 
very  like  bacilli,  except  that  they  have  bent  joints.  When  actively  moving 
they  exhibit  an  undulatory  movement,  depending  on  their  rotation  on 
their  long  axis. 

Examine  microscopically  some  of  the  sediment  of  “ turned  ""  beer  ; 
large  quantities  of  bacilli  can  usually  be  observed.  These  organisms  are 
also  commonly  found  in  bakers"  patent  yeasts. 

Place  some  fresh  clear  wort  in  a flask  and  plug  the  neck  moderately 
tightly  with  cotton- wool  ; boil  the  liquid  for  5 minutes  and  allow  to  cool  : 
notice  that  the  contents  of  the  flask  remain  clear.  At  the  end  of  a week, 
remove  the  plug  and  examine  a drop  of  the  liquid  under  the  microscope, 
bacteria  and  other  organisms  are  absent.  The  wort  is  still  sweet  and  free 
from  putrefactive  odour.  Let  the  flask  now  stand  freely  open  to  the  atmo- 
sphere : organic  germs  gain  entrance,  and  putrefactive  or  other  changes 
rapidly  occur.  On  the  next  and  succeeding  days,  examine  microscopically. 

Procure  a small  quantity  of  milk  and  allow  it  to  become  sour  ; examine 
microscopically  for  Bacterium  lactis.  Also,  wash  a few  grains  of  malt  in  a 
very  little  water,  and  examine  the  washings  for  this  organism. 

Prepare  two  samples  of  wort,  strongly  hop  the  one  by  adding  hops  in, 
the'  proportion  of  one-tenth  the  malt  used  : boil  the  two  samples,  filter 
and  set  aside  under  precisely  the  same  conditions.  Observe  the  relative 
rate  of  growth  and  development  of  bacterial  life  in  the  two. 


CHAPTER  XI. 

TECHNICAL  RESEARCHES  ON  FERMENTATION. 

362.  — ^In  this  chapter  are  contained  the  results  of  certain  technical 
researches  made  by  the  authors  and  others  on  matters  having  a more  or 
less  direct  bearing  on  bread-fermentation. 

363.  Strength  of  Yeast. — ^To  the  baker,  the  first  consideration  about 
yeast  is  its  strength  or  gas-yielding  power  : there  are  other  effects  which 
it  also  produces,  but  its  all-round  activity  may  be  fairly  measured  by  the 
quantity  of  gas  it  evolves  from  a suitable  saccharine  medium.  The  term 
“ strength  is  therefore  used  in  this  sense  ; it  follows  that  the  strongest 
yeast  will  also  raise  bread  better,  because  the  rising  of  the  dough  is  due 
to  the  gas  evolved  by  the  yeast  from  the  saccharine  constituents  of  the 
flour.  Different  modes  have  been  adopted  from  time  to  time  for  the  pur- 
pose of  testing  the  strength  of  yeast.  The  essential  principle  of  these 
has  been  to  ferment  a definite  quantity  of  some  saccharine  fluid  with  a 
constant  weight  of  yeast,  at  a constant  temperature,  and  to  then  deter- 
mine the  volume  of  gas  evolved  in  a given  time.  Meissl,  of  Vienna,  used 
the  following  process,  which,  like  most  others  of  its  kind,  is  based  on  the 
principle  that  the  strength  of  the  yeast  can  be  judged  from  the  amount  of 
carbon  dioxide  it  produces  from  a certain  quantity  of  sugar,  the  other 
substances  being  in  equal  proportions. 

In  order  to  carry  out  the  test,  the  following  substances  must  be  pre- 
pared by  rubbing  them  together  : 400  grams  of  refined  cane-sugar,  25 
grams  of  phosphate  of  ammonium,  and  25  grams  of  phosphate  of  potassium. 
A small  vessel  should  be  ready  at  hand  of  70  to  80  c.c.  capacity,  and  fitted 
with  an  india-rubber  stopper  containing  two  holes,  in  one  of  which  should 
be  placed  a bent  glass  tube,  the  long  end  of  which  should  nearly  reach 
the  bottom  of  the  vessel,  and  the  top  end,  during  the  fermentation,  should 
be  corked  up.  The  second  hole  serves  for  the  reception  of  a small  chloride 
of  calcium  tube. 

The  testing  of  the  yeast  may  then  be  commenced  in  the  following  manner  : 
4*5  grams  of  the  above  mixture  should  be  stirred  gently,  and  dissolved 
in  50  c.c.  of  distilled  water.  In  this  liquid  one  gram  of  the  yeast  on  which 
the  experiment  is  to  be  tried  should  be  carefully  stirred  and  mixed  until 
no  lumps  are  to  be  seen.  The  vessel  with  its  contents  must  be  weighed 
and  then  placed  in  water  at  a temperature  of  30°  C.,  and  left  to  remain 
during  six  hours.  At  the  end  of  this  time  it  must  be  taken  out  and  plunged 
immediately  into  cold  water  in  order  to  cool  it  as  quickly  as  possible.  The 
stopper  is  then  taken  out  of  the  bent  glass  tube,  and  the  air  allowed  to 
enter  during  a minute  or  two,  so  as  to  drive  out  the  carbon  dioxide.  Tlie 
vessel  and  its  contents  must  then  be  weighed.  The  loss  of  ■weight  arises 
from  the  quantity  of  carbon  dioxide  which  has  been  thrown  ofi  during  the 
process.  By  this  method,  the  carbon  dioxide  is  estimated  by  weight  : 
the  chloride  of  calcium  tube  is  affixed  for  the  purpose  of  retaining  any 
traces  of  aqueous  vapour  which  otherwise  would  escape. 

In  many  ways  this  apparatus  and  method  were  susceptible  of  improve- 
ment, at  least  when  used  for  technical  and  commercial  purposes.  In 
the  first  place  the  actual  weight  of  the  flask  with  contents  amounts  to 
some  80  or  90  grams,  while  the  weight  of  carbon  dioxide  evolved  varied, 
in  some  experiments  made  by  the  author,  from  0*291  to  1*237  grams.  To 

198 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


199 


accurately  measure  these  differences  of  weight  in  an  apparatus,  itself  weigh- 
ing so  much,  a very  delicate  balance  is  requisite.  This  method  is  capable, 
in  competent  hands,  of  yielding  accurate  results  ; but  it  is  tedious,  and 
does  not  give  all  the  information  that  could  be  wished. 

Another  mode  of  procedure  is  to  collect  the  gas  in  a jar  over  mercury 
in  a pneumatic  trough  ; this  undoubtedly  gives  the  most  accurate  results, 
but  is  open  to  the  objection  that  mercury  is  expensive,  and  the  apparatus, 
from  its  great  weight,  heavy  and  cumbersome.  The  reader  is  already 
aware  that  water  is  capable  of  dissolving  carbon  dioxide  gas  to  the  ex- 
tent of  its  own  volume  ; this,  therefore,  is  an  obstacle  to  the  employment 
of  water  for  its  collection.  One  of  the  authors,  nevertheless,  made  the  experi- 
ment, and  found  that  on  collecting  the  gas  evolved  by  the  yeast  during 
fermentation,  in  the  ordinary  manner  in  a graduated  gas  jar  over  water, 
most  interesting  results  could  be  obtained.  These  were  of  course  not 
absolutely  correct,  because  a certain  quantity  of  the  gas  was  absorbed 
by  the  water  ; still,  duplicate  experiments  gave  corresponding  quantities  of 
gas,  while  most  important  information  was  gained  as  to  the  general  char- 
acter of  different  yeasts  when  examined  in  this  manner.  Results  obtained 
in  this  way  may  therefore  be  viewed  as  comparable  with  each  other. 

364.  Yeast  Testing  Apparatus. — ^In  the  next  place  a series  of  experiments 
were  made  in  which  the  gas  was  admitted  to  the  graduated  jar  through 
the  top,  and  so  did  not  bubble  through  the  water  at  all.  When  collected 
in  this  way  the  amount  of  absorption  was  small  and  very  uniform.  Two 
jars  were  two-thirds  filled  in  this  manner  with  washed  carbon  dioxide 
gas  prepared  from  marble  and  hydrochloric  acid.  They  were  then  allowed 
to  stand,  and  the  amount  of  absorption  observed  hourly.  The  rate  of 
absorption,  with  the  particular  jars  used,  was  as  nearly  as  possible  a cubic 
inch  per  hour.  Subsequent  trials  with  jars  of  one  hundred  cubic  inch 
capacity  gave  an  outside  rate  of  absorption  of  two  cubic  inches  per  hour. 
A still  better  plan  is  to  use  instead  of  water  an  aqueous  solution  of  cal- 
cium chloride  of  a degree  of  concentration  giving  a specific  gravity  of  1 *4. 
With  this  solution  there  is  practically  no  absorption  of  carbon  dioxide. 
A saturated  solution  of  common  salt  (brine)  may  be  used  instead  of  the 
calcium  chloride,  with  only  slightly  more  absorption.  As  a result  of 
numerous  experiments,  the  authors  employ  one  or  other  of  the  forms  of 
apparatus  figured  below. 


200 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  glass  bottle,  marked  a in  the  figure,  is  of  about  12  ounces  capacity, 
and  is  fitted  with  india-rubber  cork  and  leading  tube,  h.  The  sugar  or 
other  saccharine  mixture  to  be  fermented  is  raised  to  the  desired  tem- 
perature, and  then  placed  in  this  bottle.  The  yeast  is  weighed  out,  and 
then  also  added  ; they  are  then  thoroughly  mixed  by  gentle  agitation. 
By  means  of  an  india-rubber  tubing  joint  at  c,  the  generating  bottle  is 
connected  to  the  leading  tube,  e,  of  the  glass  jar,  /.  This  leading  tube  is 
provided  at  d with  a branch  tube,  which  may  be  opened  or  closed  by  means 
of  a stopper  of  glass  rod  and  piece  of  india-rubber  tubing.  The  jar,  /, 
is  graduated,  as  shown,  into  cubic  centimetres  commencing  immediately 
below  the  shoulder  with  0,  and  ending  near  the  bottom  with  1000.  This 
constitutes  the  apparatus  proper  ; in  use  the  generating  bottle,  a,  is  placed 
in  a water-bath,  g g.  This  bath  is  fixed  on  a tripod  over  a bunsen  burner, 
and  is  provided  with  an  iron  grid,  A,  in  order  to  prevent  the  generating 
bottle  coming  in  absolute  contact  with  the  bottom  of  the  bath.  By  means 
of  an  automatic  regulator  the  bath  is  maintained  at  any  desired  temperature. 
The  gas  jar,  /,  stands  in  a pneumatic  trough,  i i. 

As  a rule,  more  than  one  test  is  made  at  a time,  the  water-bath  should 
therefore  be  sufficiently  large  to  take  four  or  six  bottles  at  once  : two 
pneumatic  troughs  are  then  employed,  and  either  two  or  three  of  the  gas 
jars,  /,  arranged  in  each.  While  for  strictly  accurate  experiments  it  is 
essential  that  the  yeast  bottles  be  kept  as  nearly  as  possible  at  a definite 
temperature,  yet  results  of  interest  may  be  obtained  without  the  employ- 
ment of  a water-bath.  The  whole  apparatus  should,  under  those  circum- 
stances, be  placed  in  some  situation  where,  as  nearly  as  possible,  a constant 
temperature  is  maintained. 

At  the  start  of  the  experiment  the  air  is  exhausted  through  d,  which 
is  again  closed  with  the  stopper.  As  the  fermentation  goes  on  the  gas 
evolved  is  collected  in  /,  and  its  volume  read  off,  from  the  surface  of  the 
water,  at  the  end  of  each  half-hour  or  hour.  Full  and  detailed  particu- 
lars are  given  at  the  end  of  this  chapter  as  to  the  exact  mode  of  procedure 
in  using  this  apparatus. 

When  the  requisite  allowance  is  made  for  the  absorption  of  the  gas 
by  water,  the  corrected  reading  very  nearly  corresponds  with  the  absolute 
amount  of  gas  which  has  been  evolved.  It  is  far  better,  however,  to  use 
brine  and  so  prevent  any  absorption  of  the  gas.  There  are  slight  varia- 
tions due  to  alterations  of  barometric  pressure  and  of  temperature  ; these 
can,  if  wished,  be  calculated  out  and  allowed  for — that  is  not,  however, 
for  ordinary  purposes  necessary.  Gases  are  usually  measured  at  a stan- 
dard pressure  of  760  millimetres,  or  very  nearly  30  inches  of  mercury, 
that  is  with  the  barometer  standing  at  30.  A rise  or  fall  of  the  barometer 
through  half  an  inch  only  makes  a difference  of  one-sixtieth  on  the  total 
reading,  and  this  may  as  a rule  be  neglected.  In  case  the  estimation  is 
being  made  in  either  the  laboratory  or  a bakehouse,  the  temperature  is, 
as  a rule,  fairly  constant.  Supposing  it  be  taken  at  70°  F.,  then  it  will 
be  found  that  a difference  of  5°  either  way  only  causes  a variation  in  the 
volume  of  the  gas  of  one  hundredth  the  total  amount.  Barometric  and 
thermometric  variations  may,  therefore,  for  most  practical  purposes,  be 
neglected.  Further,  whatever  variations  there  may  be  either  in  tem- 
perature or  pressure,  all  the  tests  made  at  the  same  time  are  made  under 
precisely  similar  conditions. 

In  all  the  experiments  quoted,  except  the  later  ones,  the  gas  was  col- 
lected over  water.  No  corrections  were,  however,  made  for  absorption, 
because  it  is  evident  that  at  the  outset  the  carbon  dioxide  remains  as  a 
layer  of  gas  within  the  bottle,  simply  displacing  air  over  into  / ; during 
this  time  no  absorption  can  take  place.  It  should,  however,  be  remem- 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  201 

bered  that,  when  the  gas  remains  stationary  for  any  length  of  time,  a quan- 
tity must  have  been  evolved  about  equal  to  that  being  absorbed. 

In  the  alternative  apparatus,  the  generating  bottle,  a,  and  leading 
tube,  h,  are  the  same  as  before.  At  c^,  a glass  stop-cock  is  fixed  in  the 
leading  tube  which  is  attached  by  means  of  india-rubber  tubing  to  the 
further  end  of  which  just  passes  through  an  india  rubber  cork  fixed  in  the 
glass  bottle,  e^,  having  a capacity  of  600  c.c.  or  thereabouts.  Another 
tube,  /^,  leads  from  the  bottom  of  and  has  its  lower  end  open.  Under 
this  is  placed  a graduated  measuring  jar,  of  500  c.c.  capacity.  In  use 
the  yeast  and  fermenting  medium  are  placed  as  before  in  the  generating 
bottle,  a.  The  bottle  is  filled  with  brine,  and  the  apparatus  fixed  to- 
gether and  arranged  in  position  as  shown  in  the  figure.  As  gas  is  generated 
in  the  bottle,  a,  it  displaces  an  equivalent  amount  of  brine  in  the  liquid 
passing  over  and  being  collected  in  the  measuring  jar,  g^.  Readings  of 
the  volume  of  brine  thus  displaced  may  be  made  hourly,  and  thus  results 
obtained  of  a similar  character  to  those  with  the  other  apparatus.  When 
the  collecting  jar  is  filled  to  the  500  c.c.  mark,  the  stop-cock,  may  be  closed 
and  the  brine  in  g^  returns  to  e,^  and  the  collection  and  measurement  of 
gas  again  commenced  on  reopening  the  stop-cock,  c^.  This  second  form 
of  apparatus  can  be  the  more  readily  fixed  up  from  appliances  found  in  the 
laboratory,  while  both  are  practically  identical  in  their  working.  In  the 
first  form,  the  gas  within  is  under  diminished  pressure,  any  leakage  there- 
fore will  increase  the  apparent  amount  of  gas  evolved.  In  the  second 
arrangement,  the  gas  is  under  increased  pressure,  and  consequently  any 
leakage  will  result  in  loss  of  gas. 


365.  Degree  oUAccuracy  of  Method. — ^This  is  a matter  of  great  impor- 
tance, because  unless  fairly  constant  and  accurate  results  are  obtainable, 
little  or  no  confidence  can  be  placed  in  them,  or  any  deductions  based 
thereon.  A number  of  duplicate  experiments  were  therefore  first  made 
in  order  to  test  the  accuracy  of  the  estimations  ; the  results  are  appended. 
They  serve  also  to  show  how  the  results  may  be  entered  up  in  the  labora- 
tory note-book.  For  the  composition  of  “ Yeast  mixture  ”,  see  paragraph 
367 

No.  1.  Brewers’  Yeast,  ^ oz.  ; Yeast  Mixture,  J oz.  ; Water,  6 oz.  at 
30°  C. 

No.  2.  Duplicate  of  No.  1. 

No.  3.  French  Compressed  Yeas^-.  J oz.  ; Yeast  Mixture,  J oz.  ; Water, 
6 oz.  at  30°  C. 

No.  4.  Duplicate  of  No.  3. 


202 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Time. 


0 

J hour 
1 „ 


IJ  hours 


2 

2i 

3 

4 


41 


No.  1. 


No.  2. 


0-0 


0-7 


6-5 


14-2 


i 22-0 


30-0 


! 41-0 


0-7 


5-8 


7-7 


7-8 


8-0 


j 11-0 


47*0 ! 


54-5 


G-0 


’•5 


0-0 


0-5 


0-5 


6-0 


I ... 


5-5 


I-  74 


13-8 


8-2 


22-0 


29-7 


I 74 


41-0; 


46-7 

53-7 


11-3 


8-0 


i Cubic  Inches. 

1 Temper;!-  i 

ture.  ! 

No.  3. 

No.  4. 

! ' ’ 

0*0 

0*0. 

2*5 

: 29*7  ■ 

3*1 

! i 

I i 

3*1 

2*5 

15*2 

17*7 

1 30*0 

16*1 

, 

19*2 

30*0 

^ 21*8 

21*4 

41*0 

39*1 

29*8 

21*0 

20*7 

62*0 

59*8 

^ 28*9 

20*0 

20*4 

82*0 

80*2 

29*5  ; 

21*5 

21*0 

103*5 

101*2 

30*0 

'-22*3 

23*2 

125*8 

17*8 

124*4 

30*25 

20*4 

1 

r 

143*6 

144*8 

30*25 

14*9 

'15*9 

158*5 

9*5 

160*7! 

30*0  ! 

9*3  ; 

168*0 

170*0 

30*0 

7*0 

5*0  : 

175*0 

175*0 

30*0 

2*8 

0*8  1 

177*8' 

1 

175*8'  : 

29*9  j 

The  figures  placed  opposite  the  brackets  represent  the  volume  of  gas 
given  off  in  each  successive  half-hour.  A thermometer  was  placed  in 
the  water-bath  and  the  temperature  observed  at  the  time  of  each  read- 
ing, and  registered  in  the  last  column.  The  temperature  in  this  experi- 
ment shows  considerably  greater  variations  than  that  in  those  made  later. 
It  will  be  noticed  that  both  pairs  of  du2:)licates  agree  very  closely  throughout 
the  entire  fermentation. 

It  may  here  be  mentioned  that  a half- ounce  of  sugar  yields,  on  the 
supposition  that  the  whole  is  transformed  with  carbon  dioxide  and  alcohol, 
the  following  quantities  : — 

I oz.  of  sugar  =14*2  grams,  and  yields  7*30  grams  of  CO2  = 

3*705  litres  = 226  cubic  inches  at  0°  C.  = 

242  „ 20°C. 

(One  cubic  inch  = 16*4  c.c.) 

It  will  be  remembered  that  actually  only  about  95  per  cent,  of  the 
sugar  is  thus  converted  into  carbon  dioxide  and  alcohol  ; these  quantities 
in  strictness,  therefore,  require  to  be  reduced  about  5 per  cent. 

As  in  the  experiments  to  be  now  described  the  same  brand  or  kind 
of  yeast  was  used  on  different  days,  it  was  necessary,  as  a preliminary, 
to  ascertain  the  degree  of  constancy  of  strength  of  the  same  yeast.  Deter- 
minations were  made  on  one  brand  of  compressed  yeast  with  the  following 


results  : — 

No.  1.— April  27,  1885, 
No.  2.— May  7,  1885, 
No.  3.— June  30,  1885, 


) Yeast,  I oz.  ; Yeast  Mixture,  J oz.  ; 
J Water,  6 oz.  at  30°  C. 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  203 


Gas 

Evolved  in  Cijdic  Inches. 

Time. 

No.  1. 

No.  2. 

No.  3. 

1 

0 

0-0. 

0-0, 

0-0, 

21-7 

1 

[24-5 

1 

[28-7 

I liour. . 

21-7 

24-5 1 

1 

28-7| 

41-3 

1 

'36-4 

1 

[31-9 

2 hours 

63-0 

60-9 1 

60-6 1 

33-0 

1 

^43-1 

1 

143-6 

3 „ 

96-0 

104-0 1 

1 

104-2 1 

1 

34-3 

1 

'32-0 

1 

[40-8 

4 „ 

130-3 

24-2 

136-o| 

1 

[22-5 

145-0 1 

[30-0 

5 „ 

154-5 

158-5| 

1 

175-0| 

15-7 

1 

1 

17-5 

1 

[ 2-8 

6 ,, 

i 

170-2' 

175-0 

1 

1 

177-8' 

1 

Although  these  results  do  not  agree  with  that  closeness  observable  in 
the  duplicates,  yet  it  will  be  seen  that  the  yeast  is  throughout  fairly  simi- 
lar in  behaviour  ; still,  it  must  be  remembered  that  in  experiments  made 
on  different  days  the  results  are  not  always  strictly  comparable,  because 
the  yeast  is  sure  to  be  not  absolutely  the  same  in  each  case. 

366.  Effect  of  Different  Media  on  Yeast  Growth. — ^That  certain  substances 
are  eminently  fitted  for  aiding  the  gro^wth  and  development  of  yeast,  while 
others  are  not  so  suited,  has  already  been  stated.  In  order  to  measure 
quantitatively  the  effect  of  sowing  yeast  in  different  solutions,  the  following 
determinations  were  made. 


367.  Comparison  between  Sugar,  “ Yeast  Mixture,”  Pepsin,  and  Albumin. 

— The  “ yeast  mixture  ” referred  to  is  based  on  the  fluid  in  which  Pasteur 
cultivated  a yeast,  and  which  is  known  as  “ Pasteur’s  Fluid.”  Pasteur 
employed  a solution  of  sugar  and  ammonium  tartrate  to  supply  saccharine 
matter  and  nitrogen  ; to  this  he  added  some  yeast  ash  as  a source  of  mineral 
constituents.  This  fluid  may  be  closely  imitated  by  use  of  the  following 
formula — 

Potassium  Phosphate  . . . . , . . . . . 20  parts. 

Calcium  Phosphate  . . . . . . . . . . 2 ,, 

Magnesium  Sulphate 


Ammonium  Tartrate 
Purest  Cane  Sugar 
Water 


2 

100 

1500 

8376 


10,000  parts. 

As  this  solution  keeps  badly,  the  yeast  mixture  consists  of  Pasteur’s  Fluid, 
minus  the  Avater.  The  salts  are  first  powdered  and  dried,  and  then  mixed 
until  thoroughly  incorporated.  This  mixture  has  the  great  advantage 
that  while  dry  it  can  be  kept  any  length  of  time  without  change. 

Date,  April  26,  1885. 

No.  I.  Pure  sugar,  J oz.  (14*2  grams^)  ; compressed  yeast,  J oz.  (3*5 
grams)  ; water,  6 oz.  (170  grams)  at  30°  C. 

^ In  these  experiments  an  anomaly  will  be  noticed  in  the  systems  of  w'eights  em- 
ployed. In  deference  to  the  fact  that  many  of  the  readers  of  this  book  will  be  much  more 


204 


THE  TECHNOLOGY  OF  BREAD-MAKING 


No.  2.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C. 

No.  3.  Pure  Sugar,  J oz.  ; pepsin,  1 *5  grams  ; compressed  yeast,  J oz.  ; 
water,  6 oz.  at  30°  C. 

No.  4.  Yeast  mixture,  J oz.  ; pepsin,  1*5  grams  ; compressed  yeast, 
J oz.  ; water,  6 oz.  at  30°  C. 

At  the  expiration  of  seven  liours,  the  following  quantities  of  gas  had 
been  evolved  : — 

No.  1 ..  51*3  cubic  inches.  i No.  3 ..  112*0  cubic  inches. 

No.  2 ..  132*0  „ 1 No.  4 ..  181*5 

Experiments  were  also  made  with  pepsin  and  albumin  by  themselves, 
but  neither  of  these  gave  practically  any  evolution  of  gas. 

From  these  experiments  the  following  conclusions  are  derived  : — 

Pure  sugar  undergoes  a regular  but  somewhat  slow  fermentation. 

Sugar  mixed  with  about  ten  per  cent,  of  pepsin  ferments  at  first  more  slowly, 
but  afterwards  much  more  rapidly. 

“ Yeast  mixture,”  consisting  of  sugar,  ammonium  tartrate,  and  inorganic  salts, 
ferments  from  the  commencement  still  more  rapidly. 

Yeast  mixture,  with  about  10  per  cent,  of  pepsin,  undergoes  still  more  rapid 
fermentation. 

Nitrogenous  bodies  alone,  as  pepsin,  albumin,  in  water,  or  2J  per  cent,  salt 
solution,  evolve  practically  no  gas. 

Pepsin  and  other  nitrogenous  bodies  must  therefore  be  considered, 
not  as  the  substances  from  which  yeast  causes  the  evolution  of  gas,  but 
as  stimulating  nitrogenous  yeast  foods. 

368.  Comparison  between  Filtered  Flour  Infusion,  Wort,  and  Yeast  Mix- 
ture Solution. — Pursuing  the  same  line  of  investigation,  experiments  were 
next  made  for  the  purpose  of  examining  and  comparing  flour  infusion, 
wort,  and  yeast  mixture,  as  fermentable  substances.  An  infusion  of  flour 
w^as  made  by  taking  400  grams  of  flour,  and  1000  c.c.  of  water  ; these 
were  shaken  thoroughly  in  a flask,  from  time  to  time,  for  half  an  hour,  and 
then  allowed  to  subside  : the  clear  liquid  was  filtered,  and  its  specific  gravity 
taken  ; this  amounted  to  1007  *2.  Meantime,  some  malt  wort  had  been 
prepared  ; this  was  divided  into  two  portions,  the  one  of  which  was  boiled, 
the  other  allowed  to  remain  at  the  mashing  heat.  These  were  next  cooled, 
and  each  diluted  down  until  the  specific  gravity  coincided  with  that  of  the 
flour  infusion.  A solution  of  yeast  mixture  of  the  same  density  was  also 
prepared.  Fermentation  was  started  in  each  of  these  with  the  results 
given  in  the  following  table  : — 

Date,  May  8,  1885. 

No.  1.  40  per  cent,  filtered  flour  infusion,  Sp.  G.  1007*2,  6 oz.  at  30°  C.  ; 
compressed  yeast,  J oz. 

No.  2.  Unboiled  malt  wort,  Sp.  G.  1007*2,  6 oz.  at  30°  C.  ; compressed 
yeast,  J oz. 

No.  3.  Boiled  Avort,  Sp.  G.  1007*2,  6 oz.  at  30°  C.  ; compressed  yeast, 
i oz. 

familiar  with  the  English  than  the  metric  weights  and  measures,  the  authors  have,  where 
practicable,  used  the  former  system. 

The  relation  between  grams  and  fractions  of  an  ounce  may  be  understood  by  remem- 
bering once  for  all  that 

1 ounce  or  16  drams  = 28 '35  grams 
1 „ „ 8 „ = 14-2 


99 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  205 

No.  4.  Yeast  mixture  and  water,  Sp.  G.  1007*2,  6 oz.  at  30°  C.  ; com- 
pressed yeast,  oz. 

At  tlie  end  of  five  hours,  the  following  quantities  of  gas  had  been 
evolved  : — • 

No.  1 . . 8*3  cubic  inches.  i No.  3 . . 18*2  cubic  inches. 

No.  2 ..  17*1  „ 1 No.  4 ..  24*3 

The  flour  mfusion  evolved  gas  but  slowly,  and  toward  the  end  of  five 
hours,  over  which  the  experiment  lasted,  had  fallen  off  considerably.  The 
two  malt  infusions  yielded  carbon  dioxide  at  about  double  the  speed  ; 
that  in  the  boiled  wort  being  the  higher.  The  greater  quantity  of  gas 
in  the  latter  instance  is  due  to  the  fact  that  boiling  coagulates  some  of 
the  proteins  of  the  wort,  and  so  leaves  a greater  percentage  of  sugar  in 
the  liquid,  when  both  are  diluted  to  the  same  density.  This  is  an  interesting 
instance  of  the  removal  of  proteins  resulting  in  a more  copious  and  rapid 
evolution  of  gas.  The  yeast  mixture  causes  the  carbon  dioxide  to  be  evolved 
with  still  greater  rapidity.  Summing  up  the  results  : — 

In  solutions  of  the  same  density, 

Flour  infusion,  on  fermentation,  yields  gas  somewhat  slowly ; 

Unboiled  wort,  at  about  double  the  speed  ; 

Boiled  wort,  slightly  more  rapidly  than  the  unboiled  ; and 

Yeast  mixture  solution,  at  about  three  times  the  rate  of  the  flour  infusion. 

The  soluble  extract  of  flour  is  thereby  shown  to  be  capable  of  only 
a slow  fermentation  ; this  is  due  to  its  containing  a comparatively  low 
proportion  of  sugar,  and  much  of  that  of  a kind  which  requires  to  be  inverted 
before  it  can  be  fermented. 

369.  Comparison  between  Flour  and  its  Various  Constituents  fermented 
separately. — From  the  baker’s  point  of  view,  it  is  of  very  great  im_portance 
that  he  should  know  which  of  the  several  constituents  of  flour  it  is  that 
affords,  during  fermentation,  the  gas  by  which  his  dough  is  distended. 
The  following  experiments  were  made  for  the  purpose  of  obtaining  definite 
information  on  this  subject — No.  I requires  no  further  explanation.  In 
No.  2,  34  grams  of  flour  were  mixed  with  6 oz.  (=170  c.c.)  of  water,  being 
equivalent  to  20  per  cent,  of  flour  in  the  water.  In  No.  3,  the  flour  was 
agitated  several  times  with  large  quantities  of  water,  and  allowed  to  sub- 
side between  each  washing,  the  supernatant  liquid  being  poured  off,  and 
only  the  insoluble  residue  retained.  In  this  manner,  the  washed  insoluble 
residue  is  obtained  comparatively  free  from  the  other  constituents.  Of 
these  three  samples.  No.  2 represents  the  whole  of  the  flour.  No.  I the 
soluble,  and  No.  3 the  insoluble  portion.  No.  4 consisted  of  £0  per  cent, 
flour  infusion,  with  gelatinised  starch  added  ; the  whole  being  subjected 
to  a temperature  of  30°  C.  for  12  hours  before  fermentation  : this  method 
was  adopted  in  order  to  determine  what  diastatic  effect  was  produced 
by  the  flour  infusion  on  the  gelatinised  starch,  it  being  assumed  that  what- 
ever starch  was  converted  into  sugar  would,  under  the  influence  of  the 
yeast,  be  decomposed  with  the  evolution  of  carbon  dioxide  gas.  No.  5 
was  a somewhat  similar  experiment,  made  with  gluten  ; some  flour  was 
doughed,  and  then  the  gluten  washed  as  weU  as  practicable  in  a stream 
of  water.  In  order  to  get  as  large  a surface  as  possible,  this  gluten  was 
next  rubbed  in  a mortar  with  clean  sand  ; it  was  in  this  way  cut  up  into 
a ragged  mass.  The  gluten  was  mixed  with  water  and  kept  at  30°  C.  for 
12  hours,  in  order  to  permit  any  degrading  action,  that  warm  water  is 
capable  of  exerting  on  gluten  during  that  time,  to  assert  itself.  In  Nos. 
4 and  5,  yeast  was  added  at  the  end  of  12  hours.  No.  6 was  a repetition 
of  No.  4,  except  that  the  gelatinised  starch  and  flour  infusion  were  mixed 
immediately  before  fermentation.  In  No.  7 the  starch  was  simply  added 


206 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


to  the  flour  infusion  without  previous  gelatinisation.  No.  8 consisted  of 
wheat-starch  and  water  only,  to  which  yeast  was  added.  The  starch 
used  for  these  experiments  was  specially  prepared  in  the  laboratory  from 
the  best  Hungarian  flour  by  washing  the  dough,  enclosed  in  muslin,  thus 
separating  the  gluten.  The  starch  was  allowed  to  settle,  and  the  super- 
natant liquid  poured  ofl  ; the  starch  was  then  stirred  up  with  some  more 
water,  and  again  allowed  to  subside.  These  washings  were  repeated  daily 
for  about  a fortnight,  at  the  end  of  which  time  the  starch  was  air- dried. 
On  being  tested  with  Fehling’s  solution  the  starch  gave  no  trace  of  preci- 
pitate : its  purity  was  therefore  assured.  This  series  of  fermentation  tests 
altogether  extended  over  a period  of  three  days. 

Date,  May  11,  1885. 

No.  1.  20  per  cent.  Altered  infusion  of  flour,  6 oz.  at  30°  C.,  compressed 
yeast,  J oz. 

No.  2.  34  grams  flour  ; water,  6 oz.  at  30°  C.  ; compressed  yeast,  J oz. 

No.  3.  Washed  insoluble  residue  from  34  grams  of  flour  : water,  6 oz. 
at  30°  C.  ; compressed  yeast,  J oz. 

Date,  May  12,  1885. 

No.  4.  20  per  cent,  filtered  flour  infusion,  6 oz.  at  30°  C.  ; wheat  starch, 
5 grams  taken  and  gelatinised,  cooled,  then  added  to  flour 
infusion.  Mixture  placed  in  bottle  and  maintained  at  30° 
0.  for  12  hours  ; then  J oz.  compressed  yeast  added  and  fer- 
mentation commenced. 

No.  5.  Moist  thoroughly  washed  gluten,  5 grams,  triturated  in  mortar 
with  sand  in  order  to  expose  large  surface  : gluten  with  6 oz. 
of  water  at  30°  C.  placed  in  bottle  and  maintained  at  30°  C. 
for  12  hours  ; then  ^ oz.  compressed  yeast  added  and  fer- 
mentation commenced. 

Date,  May  13,  1885. 

No.  6.  20  per  cent,  filtered  flour  infusion,  6 oz.  at  30°  C.  ; wheat  starch, 
5 grams,  gelatinised  ; compressed  yeast,  J oz. 

No.  7.  20  per  cent,  filtered  flour  infusion,  6 oz.  at  30°  C.  ; wheat  starch, 
5 grams,  ungelatinised  ; compressed  yeast,  J oz. 

Date,  May  11,  1885. 

No.  8.  Wheat  starch,  5 grams,  gelatinised,  water  6 oz.  at  30°  C.  ; com- 
pressed yeast,  J oz. 

At  the  expiration  of  six  hours,  the  following  quantities  of  gas  had  been 


evolved 

No.  1 

2*5  cubic  inches. 

No.  5 . . 1*3  cubic 

inches. 

No.  2 

..  17-5 

No.  6 . . 33-7 

No.  3 

. . 3-0 

No.  7 ..  8-2 

No.  4 

..  37-5 

No.  8 ..  0-9 

y 

No.  1, 

consisting  of  20  i)er  cent,  flour  infusion,  gave  ofl  very 

little  gas. 

the  quantity  amounting  to  only  2*5  cubic  inches  in  six  hours  ; this  is  very 
much  less  than  that  obtained  in  the  previous  series  of  experiments  in  which 
a 40  per  cent,  infusion  was  employed  ; the  latter  gave  ofl  8*3  cubic  inches 
in  five  hours.  No.  2,  containing  the  whole  of  the  flour,  gave  ofl  gas  much 
more  copiously,  in  six  hours  there  being  17*5  cubic  inches  of  gas  evolved. 
After  the  second  hour,  the  evolution  fell  ofl  slowly  but  regularly.^  The 
washed  residue  gave  ofl  just  the  same  amount  of  gas  as  did  the  filtered 
infusion  ; in  fact,  at  the  end  of  the  fifth  hour.  No.  3 gave  the  higher  reading. 

^ In  all  these  tests,  readings  were  made  either  every  hour  or  half-hour,  but  usually 
the  result  of  one  reading  only  is  here  given.  When  of  special  interest,  howev^er,  the 
explanatory  remarks  contain  also  references  to  other  readings. 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


207 


It  will  be  noticed  that  the  whole  of  the  flour  gives  off  three  times  as  much 
gas  as  do  the  filtered  infusion  and  the  washed  residue  together.  The  reason 
is  that,  when  flour  is  shaken  with  water  and  then  filtered,  tlie  substances 
which  under  the  action  of  yeast  evolve  gas  are  not  all  removed  in  the  fil- 
trate : they  are  only  separated  from  the  insoluble  residue  with  great  diffi- 
culty, and  several  washings  do  not  so  thoroughly  remove  fermentable 
matter  as  to  leave  the  residue  completely  unfermentable.  That  the  fer- 
mentation in  No.  3 is  not  due  to  the  insoluble  residue  is  proved  by  the  result 
of  experiment  No.  5 ; for  with  well  washed  and  kneaded  gluten,  but  very 
little  gas  is  evolved,  the  total  amount  in  nine  hours  being  only  1*5  cubic 
inches,  and  this  although  the  gluten  for  twelve  hours  previous  to  fermen- 
tation was  digested  with  water  at  30°  C.  Much  of  the  fermentable  matter 
•of  flour  belongs  to  what  may  be  called  the  semi-soluble  portion,  that  is, 
the  part  of  the  flour  which  is  retained  by  an  ordinary  filter  paper,  but  on 
kneading  is  readily  separated  by  the  mechanical  action  from  the  gluten. 
In  Nos.  4 and  6 the  quantities  used  are  the  same,  but  the  former  of  the 
two  samples  affords  evidence  of  diastasis  having  been  occasioned  during 
the  twelve  hours  for  which  the  gelatinised  starch  was  subjected  to  the 
action  of  the  flour  infusion.  No.  6 at  first  proceeded  somewhat  the  more 
rapidly,  but  evolved  very  little  gas  during  the  second  hour  ; during  the 
third  hour,  however,  it  recovered  itself  and  proceeded  regularly,  until 
at  the  expiration  of  six  hours  the  evolution  of  gas  ceased,  with  a total  of 
33*7  inches.  In  No.  4 the  fermentation  proceeds  rapidly  and  regularly, 
falling  off  towards  the  end,  and  finishing  at  five  hours  with  37  *5  cubic  inches. 
As  a result  of  the  previous  diastasis,  a larger  quantity  of  gas  is  evolved, 
but  in  each  instance  the  greater  part  of  the  starch  remained  behind,  as  if 
5 grams  of  starch  were  completely  changed  into  sugar,  and  then  by  fer- 
mentation into  carbon  dioxide  and  alcohol,  the  yield  of  gas  would  roughly 
be  about  85  cubic  inches  at  20°  C.  The  diastatic  action  of  the  flour  infusion 
will  have  more  or  less  effected  the  hydrolysis  of  the  starch  into  dextrin  and 
maltose  ; the  latter  will  have  undergone  fermentation,  while  the  former 
is  unfermentable.  Experiment  No.  8 shows  that  the  diastasis  of  the  starch 
is  effected  by  the  flour  infusion,  and  not  by  the  yeast,  for  where  pure  gela- 
tinised starch  and  yeast  alone  are  employed,  exceedingly  little  gas  is  evolved  ; 
during  eight  hours,  but  1*2  cubic  inches  only  having  accumulated.  This 
experiment  was  allowed  to  proceed  overnight,  and  at  the  end  of  twenty- 
one  hours,  7*0  cubic  inches  had  been  evolved.  Another  reading  \va.s  taken 
at  the  end  of  the  twenty-second  hour,  and  showed  that  0*8  cubic  inches 
had  been  evolved  during  the  hour.  It  would  seem  that  the  diastatic  action 
of  yeast  on  pure  starch  increases  somewhat  after  some  hours  ; but  within 
a limit  of  eight  hours,  which  covers  the  time  that  flour  is  in  most  instances 
subjected  to  fermentation,  little  or  no  action  has  occurred.  The  greater 
evolution  of  gas  after  twenty-one  hours  may  possibly  be  due  to  sugar  formed 
by  the  action  of  bacteria  on  the  starch.  Very  striking  in  connection  with 
this  is  the  result  obtained  in  experiment  No.  7 for  when  the  ungelatinised 
starch  was  mixed  with  flour  infusion  and  subjected  to  fermentation,  8*5 
cubic  inches  of  gas  were  obtained  in  eight  hours.  The  flour  infusion  must 
under  these  circumstances  have  succeeded  in  hydrolysing  some  of  the 
starch  ; for  although  starch  is  washed  most  carefully,  there  will  always 
be  a certain  number  of  cells  whose  walls  are  sufficiently  thin  to  permit 
diastasis  to  occur  ; and  as  stated  in  a previous  chapter,  some  investigators 
are  of  opinion  that  even  unbroken  wheat  starch  cells  are  comparatively 
readily  attacked  by  hydrolysing  agents.  (Refer  to  Chapter  VIII.,  para- 
graph 257).  Summing  up  the  results  obtained  in  these  experiments,  it  is 
found  that — 

Filtered  flour  infusion  supports  fermentation  slowly. 


208 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  frequently  washed  residue  of  flour  supports  fermentation  at  alout  the  same 
rate. 

The  entire  flour,  mixed  with  water,  evolves  about  six  times  as  much  gas  as  either 
the  Altered  infusion  or  the  washed  residue  from  the  same  weight. 

Kneaded  and  washed  gluten  evolves  practically  no  gas. 

Flour  infusion  and  gelatinised  starch  together  evolve  gas  in  considerable  quantity. 

The  quantity  of  gas  is  increased  when  the  infusion  and  the  gelatinised  starch 
remain  together  some  time  before  fermentation  ; which  result  is  due  to  diastasis- 
by  the  proteins  of  the  infusion. 

Ungelatinised  starch,  under  the  influence  of  yeast  and  flour  infusion,  evolves- 
a moderately  large  quantity  of  gas. 

Gelatinised  starch  alone  undergoes  little  or  no  fermentation  during  a period 
of  eight  hours,  but  ferments  slowly  after  standing  some  twenty  hours. 

370.  Further  Investigation  of  Fermentation  of  Flour  Infusion. — ^In  order 
to  further  determine  the  source  of  gas  during  the  fermentation  of  flour  infu- 
sion, the  following  experiments  were  made  : — A forty  per  cent,  filtered 
infusion  of  stone  milled  flour,  from  English  wheat,  was  prepared  by  taking 
600  grams  of  flour,  and  1500  c.c.  of  distilled  water  : these  were  several 
times  shaken  together  during  half  an  hour,  and  then  allowed  to  subside. 
The  upper  layer  of  liquid  was  next  poured  off  and  filtered  through  washed 
calico  : this  was  subsequently  again  filtered  in  the  ordinary  manner  through 
paper  until  perfectly  clear.  On  testing  with  iodine  no  colour  was  pro- 
duced, thus  showing  the  absence  of  both  starch  and  amyloins.  The  specific 
gravity  of  the  infusion  v^as  1008*5,  being  somewhat  higher  than  that  of  the 
forty  per  cent,  infusion  used  in  a previous  experiment.  A portion  of  the 
infusion  was  tested  for  sugar,  before  and  after  inversion,  and  also  for  pro- 
teins. Six  ounces  of  the  infusion  were  then  fermented  at  25°  C.,  with  a 
quarter-ounce  of  compressed  yeast.  The  experiment  was  continued  for 
twenty-two  hours,  at  the  end  of  which  time  fermentation  had  entirely 
ceased.  The  clear  liquid  was  then  decanted  off  from  the  layer  of  yeast 
at  the  bottom,  and  tested  for  sugar  and  proteins  as  was  done  in  the  separate 
portion  of  the  original  infusion.  To  the  yeast  remaining  in  the  bottle 
there  was  at  once  added  a half-ounce  of  sugar  and  six  ounces  of  water  at 
25°  C.,  and  the  testing  apparatus  set  up,  and  the  quantity  of  gas  evolved 
measured. 

The  sugar  was  estimated  by  Fehling’s  process  in  the  following  rnan- 
i^er  : — A weighed  quantity  of  the  flour  infusion  was  raised  to  the  boiling 
])oint,  and  maintained  at  that  temperature  for  about  five  minutes,  in  order 
to  coagulate  proteins  ; the  loss  by  evaporation  was  then  made  up  by  the 
addition  of  distilled  water,  and  the  solution  filtered. 

Quantities  taken  = 25  c.c.  Fehling's  Solution. 

50  c.c.  Water. 

20  c.c.  Forty  per  cent.  Flour  Infusion. 

IV  eight  of  cuprous  oxide,  CuaO,  yielded  = 0*1531  grams.  Assuming 
tliis  ])recipitate  to  be  due  to  maltose,  then 

0*1531  X 0*7758  = 0*1187  grams  of  maltose  in  20  c.c.  of  the  flour 
infusion  = 1*48  per  cent,  of  maltose  in  the  flour. 

In  the  next  place,  50  c.c.  of  the  flour  infusion  were  taken,  5 c.c.  of  fuming 
hydrochloric  acid  added,  and  the  solution  inverted  by  being  raised  to  68  C. 
Tlie  acid  was  tlien  neutralised  by  solid  sodium  carbonate,  and  the  solution 
made  up  to  100  c.c.  with  water.  This  produced  a twenty  per  cent,  inverted 
solution. 

Quantities  taken  = 25  c.c.  Fehling^s  Solution. 

50  c.c.  Water. 

20  c.c.  Twenty  per  cent,  inverted  Flour  Infusion,  j 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


209 


Weight  of  cuprous  oxide,  CU2O,  yielded  = 0*1860  grams. 

In  20  c.c.  of  a forty  per  cent,  solution  there  would  be  double  this  quan- 
tity = 0*1860  X 2 = 0*3720  grams.  From  this  must  be  deducted  the 
amount  of  precipitate  due  to  the  maltose  present. 

0*3720  — 0*1531  = 0*2189  grams  of  CU2O  due  to  a reducing  sugar  pro- 
duced by  inversion.  Assuming  this  sugar  to  be  cane-sugar,  or  at  least 
to  have  the  same  reducing  power,  then 

0*2189  X 0*4791  = 0*1048  grams  of  cane-sugar  in  20  c.c.  of  the  forty 
per  cent,  infusion  = 1*31  per  cent,  of  cane-sugar  in  the  flour. 

[^The  total  sugar  in  the  flour  would  thus  be  2*79  per  cent. 

After  fermentation,  the  upper  liquid  from  the  yeast  bottle  was  also 
tested  for  sugars,  after  filtration  and  coagulation  of  proteins  as  before. 
The  uninverted  solution  gave  no  precipitate  whatever  with  Fehling’s  solu- 
tion. A portion  was  next  inverted  with  acid  in  the  manner  already  des- 
cribed ; 20  c.c.  of  this  solution  gave  a slight  trace  of  precipitate  with  Fehling's 
solution,  which  was  too  little  to  weigh.  So  far,  the  practical  result  may 
be  summed  up  in  the  statement  that  filtered  aqueous  flour  infusion  contains 
two  or  more  varieties  of  sugar  ; these  during  the  act  of  fermentation  entirely  dis- 
appear. 

The  infusion  was  tested  for  proteins  by  distillation  with  alkaline  per- 
mcinganate  solution,  with  the  following  results,  calculated  to  the  percentage 
present  in  the  flour — 

In  the  infusion  before  fermentation — 0*76  per  cent. 

,,  ,,  after  ,,  0*78  ,, 

Compared  with  analyses  of  other  flours,  these  quantities  are  low  ; this 
is  probably  accounted  for  by  a forty  per  cent,  infusion  being  made,  whereas 
a ten  per  cent,  infusion  is  used  in  most  analyses  ; the  more  dilute  solution 
extracts  the  somewhat  viscous  proteins  with  greater  readiness.  The 
only  deduction  from  these  determinations  is,  that  the  amount  of  proteins 
in  a filtered  flour  infusion  is  practically  unchanged  by  the  act  of  fermentation,  there 
being  no  disappearance  whatever  of  these  bodies. 

The  following  are  the  results  of  the  fermentation  experiments — 

No.  1.  Flour  Infusion,  6 oz.  ; compressed  Yeast,  J oz.  ; Temperature, 
25°  C. 

No.  2.  Yeast  from  previous  experiment  after  cessation  of  fermenta- 
tion : Sugar,  J oz.  ; Water,  6 oz.,  at  25°  C. 

At  the  expiration  of  six  hours,  the  following  quantities  of  gas  had  been 
evolved  : — 

No  1 . . 9’6  cubic  inches.  | No  2 . . 73‘5  cubic  inches. 

As  six  ounces  of  the  forty  per  cent,  flour  infusion  would  contain  the 
soluble  matter  of  68  grams  of  flour,  it  follows  that  there  would  be  present, 
according  to  the  analysis,  1*89  grams  of  sugar.  This  quantity,  if  entirely 
converted  during  fermentation  into  carbon  dioxide  and  alcohol,  would 
yield  about  32  cubic  inches  of  gas  at  20°  C.  By  the  method  adopted  for 
testing,  15  cubic  inches  were  registered  at  the  end  of  twenty- two  hours  ; 
to  this  would  have  to  be  added  a correction  for  the  amount  lost  by  absorp- 
tion by  the  water,  in  order  to  obtain  a correct  estimate.  It  is  difficult, 
when  the  total  quantity  of  gas  evolved  is  small,  to  determine  with  accuracy 
the  loss  by  absorption,  because  the  gas  in  the  apparatus  consists  of  a mix- 
ture in  which  air  is  predominant,  consequently  the  rate  of  absorption  is 
less  than  with  pure  carbon  dioxide  gas.  If  it  were  desired  to  accurately 
estimate  the  quantity  of  gas,  collection  over  mercury  would  have  to  be 
adopted.  This  is  of  little  importance  in  the  present  experiment,  because  the 
total  measured  comes  well  within  the  amount  of  gas  that  the  sugar  would 
theoretically  yield.  In  other  words,  there  is  no  need  to  go  outside  the 
sugar  to  find  a source  from  which  the  carbon  dioxide  is  obtained,  as  the 

p 


210 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


whole  of  the  sugar  disappears,  and  in  the  act  of  fermentation  is  capable 
of  yielding  more  gas  than  that  observed  to  be  evolved.  That  the  cessation 
of  fermentation  is  not  due  to  the  exhaustion  of  the  yeast  is  proved  by  experi- 
ment No.  2,  in  which  the  same  yeast  has  more  sugar  added  to  it,  when  a 
vigorous  fermentation  was  immediately  set  up.  That  the  cessation  of 
fermentation  is  due  to  the  exhaustion  of  the  sugar  is  proved  by  that  com- 
pound being  absent  on  analysis  of  the  infusion  after  fermentation.  Summing 
up  the  whole  of  the  results — 

Flour  Infusion. 


Before  Fermentation. 

Sugar,  1*89  grams  in  the  six  ounces 
of  infusion. 

Proteins,  0*517  grams  present. 


j After  Fermentation. 

Sugar,  absent. 

Proteins,  0*530  grams  present. 

When  Fermentation  had  ceased, 
15  cubic  inches  of  gas  had  been 
evolved,  and  the  yeast  was  still 
unexhausted,  and  capable  of  in- 
I ducing  fermentation  in  fresh  sugar 
j solution.  , 


Reasoning  on  these  results,  together  with  those  obtained  in  the  series 
of  experiments  on  flour  and  its  various  constituents  taken  separately, 
the  only  logical  conclusion  is  that  the  fermentation  of  dough  is  essentially 
a saccharine  fermentation. 

It  may  be  demurred  that  the  circumstances  are  different  as  an  aqueous 
infusion  to  those  which  hold  in  a tough  elastic  mass  such  as  dough.  But 
it  is  inconceivable  that  the  fermentation  actually  immediately  depends 
on  the  conversion  of  any  but  soluble  constituents  of  the  flour  into  gas  ; 
therefore,  if  those  proteins,  so  soluble  as  to  pass  through  filter  paper,  are 
not  capable  of  yielding  gas  as  a result  of  fermentation  by  yeast,  it  follows 
that  the  more  insoluble  protein  compounds  likewise  will  not  yield  gas. 
The  fact  that  washed  gluten  yields  no  gas  affords  corroborative  proof  of 
this  point.  (The  small  quantity  actually  obtained  by  experiment  may 
be  accounted  for  by  the  well-known  difficulty  of  perfectly  freeing  gluten 
from  all  starchy  and  soluble  matters).  That  the  fermentation  of  the  flour 
itself  yields  several  times  more  gas  than  does  the  Altered  infusion,  lends  no 
support  to  the  theory  that  it  is  the  protein  matter  that  is  evolving  gas, 
because  it  has  been  shown  that  pure  ungelatinised  starch  causes  a marked 
evolution  of  gas,  being  doubtless  first  converted  into  dextrin  and  maltose  by 
diastasis.  The  fermentability  of  the  washed  residue  is  also  accounted 
for  by  its  containing  starch.  Supposing  even  that  in  dough,  after  fer- 
mentation had  ceased,  sugar  as  such  existed  and  could  be  removed  and 
detected  by  analytic  methods,  that  of  itself  would  be  no  proof  of  the  evolu- 
tion of  gas  being  at  the  expense  of  the  proteins,  or  peptones  derived  there- 
from (for  the  argument  equally  applies  to  these  latter  bodies),  because 
simultaneously  with  the  fermentation  produced  by  the  yeast  there  is  a pro- 
duction of  sugar  by  diastasis  of  the  starch.  Fermentation  of  sugar  in  a 
stiff  dough  is  rough  work  for  yeast  cells,  and  it  may  well  be  that  after  a 
few  hours  they  are  thoroughly  exhausted,  and  disappear  through  disrupt- 
ion of  their  cell  walls  : the  continuance  of  diastasis  would  still  cause  the 
slow  production  of  more  or  less  sugar.  Further,  the  diastasis  of  the  starch 
must  throughout  fermentation  precede  its  subsequent  conversion  into 
car})on  dioxide  and  alcohol  ; and  so,  if  the  reaction  be  stopped  at  any 
point,  more  or  less  sugar  would  as  a rule  be  found.  Again  drawing  a con- 


II 


'ECHNICAL  RESEARCHES  ON  FERMENTATION.  . 211 


elusion,  the  fermentation  of  dough  is  in  part  due  to  the  fermentation  of  the  sugar 
present,  in  part  to  the  diastasis  of  a portion  of  the  starch  of  the  flour  and  its  subse- 
quent fermentation  ; these  sources  are  sufficient,  and  more  than  sufficient,  for  the 
production  of  all  the  gas  evolved  ; these  statements  admit  of  experimntal  proof. 
There  is  no  satisfactory  evidence  in  favour  of  the  gas  evolved  being  in  any  sensible 
degree  derived  from  the  protein  constituents  of  dough.  It  should  be  noticed 
that  no  assertion  is  made  that  no  gas  whatever  is  derived  from  the  protein 
constituents  of  flour  ; it  is  possible  that  in  extreme  cases  gas  is  produced 
from  protein  matters  as  a result  of  butyric  and  putrefactive  fermentations  ; 
but  in  ordinary  bread-making,  as  it  holds  in  the  United  Kingdom,  the  amount 
of  gas  derived  from  this  source  is  of  no  importance  compared  with  that 
from  sugar,  and  indirectly  from  starch.  Whatever  amount  of  gas  there 
is  that  is  thus  obtained  from  proteins  is  the  result,  not  of  the  action 
of  yeast,  but  of  bacteria.  Further,  the  statement  that  protein  bodies 
do  not  themselves  evolve  gas  during  panary  fermentation  must  not  be 
construed  into  meaning  that  they  do  not  affect  the  quantity  evolved. 
In  their  capacity  as  nitrogenous  yeast  foods,  they  aid  the  yeast  in  its 
development,  and  consequently  in  its  production  of  gas  by  decomposition 
of  saccharine  bodies. 

371.  Effect  of  Salt  on  the  Fermentation  of  Flour. — Most  bakers  are 
familiar  with  the  general  statement  that  salt  retards  fermentation  : in 
order  to  determine  the  amount  of  such  retardation  the  following  experi- 
ments were  made.  In  the  first,  flour  and  water  alone  were  fermented  ; 
the  others  consisted  of  flour  mixed  with  salt  solutions  of  various  strengths. 
The  appended  table  contains  the  results  : — • 

Date,  May  27,  1885. 

No.  1.  Flour,  34  grams  ; water,  6 oz.  at  30°  C.  ; compressed  yeast, 
J oz. 

No.  2.  Flour,  34  grams  ; water,  6 oz.  at  30°  C.  ; compressed  yeast, 
J oz.  ; salt,  2*5  grams  = 1*4  per  cent,  salt  solution. 

No.  3.  Flour,  34  grams  ; water,  6 oz.  at  30°  C.  ; compressed  yeast, 
J oz.  ; salt,  5*0  grams  = 2*9  per  cent,  salt  solution. 

No.  4.  Flour,  34  grams  ; water,  6 oz.  at  30°  C.  ; compressed  yeast, 
J oz.  ; salt,  8*5  grams  = 5*0  per  cent,  salt  solution. 

At  the  termination  of  six  hours,  the  following  quantities  of  gas  had 
been  evolved  : — 

No.  1 . . 18*2  cubic  inches.  | No.  3 . . 15*1  cubic  inches. 

No.  2 . . 15*2  „ I No.  4 . . 13-3 

In  the  first  test,  19*2  cubic  inches  of  gas  were  evolved  in  seven  hours, 

while  with  1*4  per  cent,  of  salt  present  in  the  solution  (No.  2)  the  gas  was 

diminished  to  15*8  cubic  inches.  Summing  up  the  conclusions  derived 
from  this  series  of  experiments — 

The  use  of  a 1*4  per  cent,  solution  of  salt  instead  of  water  produced  a marked 
diminution  in  the  evolution  of  gas. 

Increasing  the  amount  of  salt  to  2*9  per  cent,  made  very  little  difference  on 
the  speed  of  fermentation. 

With  5*0  per  cent,  of  salt,  gas  was  evolved  still  more  slowly. 

372.  Effect  on  Fermentation  of  addition  of  Various  Substances  to  Yeast 
Mixture. — Taking  yeast  mixture  as  being  a substance  well  fitted  to  undergo 
fermentation,  the  following  experiments  were  made  in  order  to  determine 
the  effect  of  the  addition  of  certain  other  substances  which  have  an  impor- 
tant bearing  on  the  fermentation  operations  involved  in  bread-making.  The 
appended  table  describes  sufficiently  the  substances  used  in  each  test  of 
the  series  ; the  quantity  of  yeast  mixture  was  constant  throughout. 


212 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Date,  May  19,  1885. 

No.  1.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C. 

Date,  May  12,  1885. 

No.  2.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; pure  wheat  starch,  5 grams. 

No.  3.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; wheat  starch,  5 grams,  gelatinised  and  allowed  to 
cool. 

Date,  May  14,  1885. 

No.  4.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; raw  flour,  5 grams. 

Date,  May  13,  1885. 

No.  5.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; flour,  5 grams,  gelatinised  with  small  quantity  of 
water,  and  allowed  to  cool. 

No.  6.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; potato,  5 grams,  boiled. 

Date,  May  18,  1885. 

No.  7.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; potato,  5 grams, 
in  small  pieces,  boiled  ; clear  filtered  water  employed  for 
boiling  them,  made  up  to  6 oz.  at  30°  C.,  and  used  instead 
of  ordinary  water. 

No.  8.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; salt,  5 grams  = 2*9  per  cent,  salt  solution. 

Date,  May  19,  1885. 

No.  9.  Yeast  mixture,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; salt,  2*5  grams  = 1*4  per  cent,  salt  solution. 

No.  10.  Yeast  mixture,  ^ oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at 
30°  C.  ; salt,  8*5  grams  = 5 per  cent,  salt  solution. 

In  six  hours,  the  following  quantities  of  gas  had  been  evolved  : — 


No. 

I 

. . 174*5  cubic  inches. 

No. 

6 

. . 188*0  cubic  inches. 

No. 

2 

. . 173*7 

No. 

7 

. . 183*5 

No. 

3 

. . 167*8 

No. 

8 

..  170*2 

No. 

4 

..  173*5 

No. 

9 

..  1780 

No. 

5 

..  205*2 

No. 

10 

..  150*5 

The  results  of  No.  2 are  identical  with  those  of  No.  1,  showing  that  the 
starch  under  these  circumstances  is  unacted  on.  This  experiment  stands 
out  in  contrast  to  that  in  a previous  series  (paragraph  369)  in  which  un- 
gelatinised starch  was  added  to  flour  infusion.  There,  a diastatic  agent 
was  present,  and  diastasis  of  the  starch  ensued  ; here,  with  yeast  only, 
the  starch  remains  throughout  unaltered.  In  No.  3 the  starch  was  gela-  I 
tinised  and  allowed  to  cool  ; in  this  case  there  is  a marked  diminution  j 
in  the  evolution  of  gas  : this  is  most  likely  due  to  the  viscous  nature  of 
the  liquid  containing  starch  in  solution,  the  effect  being  a mechanical  one, 
resulting  from  a physical  retardation  of  fermentation.  During  the  latter 
part  of  the  experiment,  which  altogether  extended  to  ten  hours,  the  pro- 
duction of  gas  exceeds  that  in  No.  1,  amounting  to  183*5  against  174*5 
cubic  inches,  and  does  not  terminate  until  the  end  of  the  ten  hours,  whereas  | 
both  Nos.  1 and  2 ceased  within  six  hours.  In  No.  4 raw  flour  is  substituted  j 
for  ungelatinised  starch  : again  a series  of  readings  are  obtained  closely  |i 
resembling  Nos.  1 and  2,  and  showing  that  with  yeast  mixture  as  a basis,  I 
raw  flour  produces  no  appreciable  action.  But  when  the  flour  is  gelatinised  i 


TECHNICAL  RESEARCHES  ON  FERMENTATION 


213 


as  in  No.  5,  the  evolution  of  gas  is  more  copious  and  more  rapid,  and  at 
the  end  of  eight  hours  a total  of  209*4  cubic  inches  of  gas  is  registered, 
with  an  increase  during  the  last  hour  of  1*2  cubic  inches.  Gelatinised 
flour  favours  fermentation  to  a much  greater  extent  than  does  gelatinised 
starch  ; the  principal  chemical  difference  between  the  two  is  that  in  the 
former  there  are  present  the  proteins  of  the  flour  non-coagulable  by  heat. 
To  No.  6 were  added  5 grams  of  potato,  boiled  ; the  result  is  a considerable 
increase  in  the  amount  of  gas  evolved,  which  shows  itseK  more  particularly 
during  the  earlier  period  of  fermentation  : boiled  potato  therefore  acts  as  a 
stimulant,  and  also  furnishes  saccharine  matter  as  food  for  the  yeast.  In 
experiment  No.  7,  it  is  remarkable,  and  contrary  to  the  generally  received 
ideas,  to  find  that  the  clear  filtered  water  in  which  potatoes  were  simply 
boiled  exercises  such  marked  influence  on  fermentation.  The  increase  in 
rapidity  of  production  of  gas  is  very  nearly  as  great  as  when  the  whole 
of  the  potatoes  are  used.  In  No.  7,  9 more  cubic  inches  of  gas  were  evolved 
than  in  No.  1,  the  action  terminating  at  the  same  time.  It  may  be  of 
interest  to  mention  here  that  in  some  parts  of  Lancashire,  where  it  is  a 
prevalent  custom  for  families  to  make  their  own  bread,  they  adopt  the 
plan  of  setting  the  sponge  with  water  in  which  the  potatoes  have  been 
boiled.  Nos.  8,  9,  and  10,  were  similar  experiments  to  those  of  the  pre- 
ceding series  (paragraph  371),  except  that  the  action  of  salt  was  tested 
on  yeast  mixture  instead  of  on  flour.  No.  8 shows  a slightly  less  quantity 
of  gas  evolved  than  does  No.  1.  No.  9,  on  the  other  hand,  shows  a decided 
increase  in  the  quantity  of  gas  over  that  evolved  either  in  Nos.  1 or  8.  In 
No.  10,  however,  where  5 per  cent,  of  salt  is  employed,  the  gas  falls  off  to 
165*2  cubic  inches  in  seven  hours,  although  at  the  end  of  the  time  fermenta- 
tion is  still  actively  proceeding.  Summarising  the  results  of  these  experi- 
ments. 

The  addition  to  yeast  mixture  of — 

Ungelatinised  wheat-starch  has  no  practical  effect  on  fermentation. 

Gelatinised  wheat-starch  at  first  retards  the  action,  which  afterward  is 
slightly  accelerated. 

Raw  flour  produces  very  little  action. 

Gelatinised  flour  induces  a much  more  rapid  and  copious  evolution  of  gas. 

Boiled  potato  produces  a similar  effect  to  gelatinised  flour,  but  to  a less 
extent. 

The  water  used  for  boiling  potatoes  is  almost  as  effective  as  the  potatoes 
themselves. 

Quantities  of  salt,  up  to  3 per  cent,  of  water  used,  do  not  retard  fermen- 
tation greatly  : above  that  quantity  salt  considerably  diminishes  the 
evolution  of  gas. 

373.  Effect  on  the  Fermentation  of  Sugar  of  the  addition  of  Flour  and 
Potatoes. — ^As  yeast  mixture  contains  within  itself  not  only  sugar,  but 
also  other  ingredients  which  stimulate  a rapid  fermentation,  it  was  thought 
advisable  to  repeat  some  of  the  preceding  experiments  with  sugar  only. 
Accordingly,  the  experiments  reeorded  in  the  following  table  were  per- 
formed. 

Date,  May  21,  1885. 

No.  1.  Sugar,  ^ oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at  30°  C.  ; 
raw  flour,  5 grams. 

No.  2.  Sugar,  J oz.  ; eompressed  yeast,  J oz.  ; water,  6 oz.  at  30°  C.  ; 

flour,  5 grams,  gelatinised  in  small  quantity  of  water  and 
allowed  to  cool. 

Date,  May  18,  1885. 

No.  3.  Sugar,  J oz.  ; compressed  yeast,  J oz.  ; water,  6 oz.  at  30°  C.  ; 
potato,  5 grams,  boiled. 


214  THE  TECHNOLOGY  OF  BREAD-MAKING. 

No.  4.  Sugar,  J oz.  ; compressed  yeast,  J oz.  ; potato,  5 grams, 
in  small  pieces,  boiled  ; clear  filtered  water  employed  for 
boiling  them,  made  up  to  6 oz.  at  30°  C.,  and  used  instead 
of  ordinary  water. 

Quantities  of  gas  evolved  in  six  hours  : — 

No.  1 . . 84*3  cubic  inches.  No.  3 . . 138*1  cubic  inches. 

No.  2 ..  135-0  „ ' No.  4 ..  133*6 

In  the  first  experiment,  with  raw  flour,  the  quantity  of  gas  evolved 
keeps  very  close  to  that  evolved  from  the  sugar  solution  and  yeast  only, 
until  three  hours  have  elapsed.  After  that  time  the  speed  of  evolution 
of  gas  falls  off  sharply,  until  in  nine  hours  the  quantity  of  gas  evolved 
is  only  just  as  much  as  the  sugar  alone  had  evolved  in  six  hours.  The 
actual  diminution  of  speed  of  the  evolution  of  gas,  as  a result  of  the  pre- 
sence of  flour,  is  noticeable  in  several  experiments.  With  gelatinised 
flour,  on  the  other  hand,  the  fermentation  proceeds  more  rapidly,  and 
to  a greater  extent  than  with  sugar  only.  The  speed  of  production  of 
gas  is  less  than  in  the  corresponding  experiment  of  the  previous  series 
with  yeast  mixture,  but  as  the  action  continues  longer  before  commencing 
to  fall  off,  the  actual  amount  of  gas  evolved  is  about  the  same.  The  result 
of  No.  3 with  boiled  potato  is  almost  similar  to  No.  2.  No.  4,  containing 
boiled  potato  water,  ferments  at  almost  exactly  the  same  rate  as  did  No.  2 
with  the  whole  of  the  potato.  Summing  up. 

The  addition  to  sugar  of — 

Raw  flour  retarded  the  fermentation  in  the  latter  part  of  the  experiment. 
Gelatinised  flour,  boiled  potato,  and  boiled  potato  water,  each  stimulated 
and  increased  the  amount  of  fermentation  to  about  the  same  degree. 


374.  Effect  of  Temperature  on  Fermentation. — In  order  to  measure 
quantitatively  the  effect  of  variations  of  temperature  on  the  produetion 
of  gas  by  fermentation,  the  following  experiments  were  made  : — Tw^o 
different  brands  of  compressed  yeast  were  employed,  one  of  which  is  desig- 
nated yeast  “A,”  the  other  yeast  “ B ; the  same  quantity  of  yeast  was 
employed  throughout  the  experiment.  The  series  included  tests  by  each 
yeast  on  sugar,  yeast  mixture,  and  flour,  at  the  respective  temperatures 
of  20°,  25°,  30°,  and  35°  C.  = (68°,  77°,  86°,  and  95°  F.). 

The  following  are  the  results  of  one  set  of  tests  : — 

Date,  July  3,  1885. — The  complete  series  at  20°  C.  made  this  day. 

„ July  2,  1885.—  „ „ 25°  C. 

„ June  30,  1885.—  „ „ 30°  C. 

„ June  29,  1885.—  „ „ 35°  C. 

No.  1.  Yeast  mixture,  J oz.  ; compressed  yeast.  A,  J oz.  ; water,  6 oz. 
at  20°  C. 

No.  2.  Yeast  mixture,  J oz.  ; compressed  yeast.  A,  J oz.  ; water,  6 oz. 
at  25°  C. 

No.  3.  Yeast  mixture,  J oz.  ; compressed  yeast.  A,  J oz.  ; water,  6 oz. 
at  30°  C. 

No.  4.  Yeast  mixture,  4 oz.  ; compressed  yeast.  A,  J oz.  ; water,  6 oz. 
at  35°  C. 

Gas  evolved  at  the  end  of  six  hours  : — 

No.  1 . . 83*8  cubic  inches.  1 No.  3 . . 177*8  cubic  inches. 

No.  2 ..  113*3  „ I No.  4 ..  175-0 

(At  the  end  of  three  hours.  Nos.  3 and  4 had  evolved  104*2  and  128*0 
cubic  inches  respectively). 

Considering  first  the  series  consisting  of  yeast  A with  yeast  mixture, 
a temperature  of  25°  C.  increases  the  total  quantity  of  gas  considerably 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


215 


over~tliat  evolved  at  20°  C.  ; a further  increase  to  30°  more  than  doubles 
the  average  speed  of  evolution  of  gas.  Beyond  30°  the  amount  of  gas 
evolved  is  not  materially  increased  with  the  rise  in  temperature,  thus  at 
35°  C.  there  is  very  little  more  gas  evolved  than  at  30°  C.  In  the  series 
where  sugar  is  substituted  for  yeast  mixture,  the  production  of  gas  is  less, 
but  the  same  general  relation  exists  between  the  various  members  of  the  series. 

With  flour,  on  the  other  hand,  there  is  a more  equal  increase,  as  shown 
by  the  following  table,  still  there  is  a greater  increase  between  Nos.  2 and  3 
than  the  others  : — 

No.  1.  Flour,  34  grams  ; compressed  yeast.  A,  J oz.  ; water,  6 oz.  at 
20°  C. 

No.  2.  Flour,  34  grams  ; compressed  yeast.  A,  J oz.  ; water,  6 oz.  at 
25°  C. 

No.  3.  Flour,  34  grams  ; compressed  yeast,  A,  J oz.  ; water,  6 oz.  at 


30°  C. 

No.  4.  Flour,  34  grams  ; compressed  yeast.  A,  J oz.  ; 


water,  6 oz.  at 


35°  C. 


Gas  evolved  at  the  end  of  six  hours  : — 


No.  1 . . 14*6  cubic  inches. 

No.  2 . . 18'-2 


No.  3 . . 24*4  cubic  inches. 

No.  4 ..  28-3 


Another  precisely  similar  series  of  experiments  were  made  with  B 
yeast,  which,  being  the  stronger  yeast  of  the  two,  gave  off  in  every  case 
more  gas  than  did  yeast  A in  the  corresponding  experiment.  This  differ- 
ence was  not  so  striking  when  yeast  mixture  was  used,  because  its  stimu- 
lating effect  helped  the  weak  yeast  proportionally  the  more.  But  in  sugar 
each  yeast  has  to  depend  more  fully  on  its  own  vitality  in  producing  fer- 
mentation. Consequently  the  stronger  yeast  B causes  the  evolution  of  a 
proportionately  higher  quantity  of  gas  than  does  the  yeast  A. 

Summarising  the  results  obtained — 

In  the  three  media  employed,  the  rapidity  of  production  of  gas  increases  with 
the  temperature  ; this  increase  is  more  marked  between  25°  and  30°  than  between 
30°  and  35°  C. 

375.  Behaviour  of  Yeasts  at  High  Temperatures. — ^In  view  of  the  fact 
that,  in  baking,  some  of  the  work  of  the  yeast  is  done  in  the  oven,  it  be- 
comes of  interest  to  ascertain  how  different  yeasts  behave  as  fermenting 
agents  at  high  temperatures.  For  this  purpose  the  following  experiments 
were  made  in  1895  : — 


Experiment  on  Yeast  at  77°  F.  (25°  C.) 
Quantities  taken — yeast,  J oz  ; flour,  2*4  oz.  ; water,  6 oz. 
No.  1. — Compressed  distillers’  yeast. 

,,  2. — Compressed  brewers’  yeast,  ordinary. 

,,  3. — ,,  ,,  ,,  special. 

„ 4. — Thin  brewers’  yeast. 


Gas  Evolved  in  Cubic  Inches. 


Time. 

No.  1. 

No.  2. 

No.  3. 

No.  4. 

1 hour 

4-0 

2-0 

7-0 

2 hours  . . 

— 

6-0 

15-0 

— 

3 

15-0 

10-0 

18-5 

4-0 

4 

— 

13-0 

22-5 

6-5 

5 

— 

— 

— 

8-0 

5J  ,, 

21-0 

— 

— 

— 

7 

22-0 

— 

l 

216 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Yeasts  Nos.  1 and  4 were  next  tested  in  precisely  the  same  manner, 
except  that  the  temperature  was  raised  to  122°  F.  (50°  C.)  The  following 
were  the  results  : — 

Gas  Evolved  in  Cubic  Inches. 


Time. 

No.  1. 

No.  4. 

1 hour 

13-0 

1-0 

2 hours  . . ■ . . 

22-75 

— 

2i  „ 

23-15 

— 

3 „ 

Stop 

1-5 

Notice  how  completely  No.  4 ceases  work  at  this  higher  temperature  ; 
while  No.  1 for  a time  is  even  more  energetic  in  action. 

In  the  next  place  a series  of  tests  were  made  at  131°  F.  (55°  C.).  The 
quantities  taken  were  not  precisely  the  same  as  in  the  previous  tests,  but 
are  given  in  detail. 

No.  1.  Compressed  distillers’  yeast,  J oz.  ; flour,  1*2  oz.  ; water,  6 oz. 
No.  la.  Yeast  as  No.  1 ; sugar,  J oz.  ; water,  6 oz. 

[No.  4.  Thin  brewers’  yeast  did  not  work  with  flour  at  122°  F.] 

No.  4a.  Thin  brewers’  yeast,  J oz.  ; sugar,  J oz.  ; water,  6 oz. 

No.  5.  Another  sample  compressed  distillers’  yeast,  J oz.  ; flour, 
* 1*2  oz.  ; water,  6 oz. 

No.  5a.  Yeast  as  No.  5 ; sugar,  J oz.  ; water,  6 oz. 

Gas  Evolved  in  Cubic  Inches. 


Time. 

No.  1. 

No.  la. 

No.  4a. 

No.  5. 

No.  5a. 

15  minutes 

1-0 

1-25 

2-0 

2-0 

30 

4-0 

5-0 

— 

2-75 

3-0 

1 hour  . . 

6-25 

7-75 

2-75 

3-0 

3-5 

2 hours  . . 

6-5 

8-75 

4-0 

3-5 

5-5 

3 „ 

7-0 

10-0 

5-75 

— 

— 

4 

Stop 

10-75 

Stop 

4-0 

7*5 

Comparing  the  two  samples  of  distillers’  yeast  ; No.  I,  it  will  be  noticed, 
works  more  vigorously,  both  in  flour  and  in  sugar,  than  No.  5.  The  thin 
brewers’  yeast.  No.  4,  works  at  this  temperature  in  sugar  ; although  inactive 
in  flour  and  water,  at  a temperature  lower  by  nine  degrees.  At  a tem- 
perature of  140°  F.,  neither  Nos.  1 nor  4 evolved  any  gas  in  a sugar 
solution.  These  results  agree  broadly  with  the  general  behaviour  of  the 
yeasts  during  baking.  They  were  first  published  by  one  of  the  authors 
in  The  Science  and  Art  of  Bread-making,  1895,  and  establish  the  fact  that 
at  high  temperatures,  distillers’  yeast  retains  its  activity  to  a much  higher 
point^than  does  English  brewers’  yeast. 

370.  Comparative  Fermentative  Tests  with  Brewers’  and  Distillers^ 
Yeasts  in  Flour  and  Sugar  Solutions. — ^The  following  experiments  were 
made  with  the  view  of  comparing  the  fermentative  capacity  of  brewers’  and 
distillers’  yeasts  in  flour  and  sugar  solutions  respectively  : — 

Date,  October  22,  1885. 

No.  1.  Yeast  mixture,  J oz.  ; water,  6 oz.  at  25°  C.  ; French  com- 
pressed  yeast,  J oz. 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  217 

No.  2.  Sugar,  J oz.  ; water,  6 oz.  at  25°  C.  ; French  compressed  yeast, 
i oz. 

No.  3.  Flour,  68  grams  ; water,  6 oz.  at  25°  C.  ; French  compressed 
yeast,  J oz.  f- 

No.  4.  Yeast  mixture,  J oz.  ; water,  6 oz.  at  25°  C.  ; compressed  Eng- 
lish brewers'  yeast,  J oz. 

No.  5.  Sugar,  J oz.  ; water,  6 oz.  at  25°  C.  ; compressed  English  brewers' 
yeast,  J oz. 

No.  6.  Flour,  68  grams  ; water,  6 oz.  at  25°  C.  ; compressed  English 
brewers'  yeast,  J oz. 

Date,  October  23,  1885. 

No.  7.  Sugar,  J oz.  ; water,  6 oz.  at  25°  C.  ; compressed  English  brewers' 
yeast,  J oz. 

No.  8.  Flour,  68  grams  ; water,  6 oz.  at  25°  C.  ; compressed  English 
brewers'  yeast,  J oz. 

No.  9.  Flour,  68  grams  ; sugar,  f oz.  ; water,  6 oz.  at  25°  C.  ; com- 
pressed English  brewers'  yeast,  J oz. 

No.  10.  Sugar,  J oz.  ; water,  6 oz.  at  25°  C.  ; Brighton  brewers'  yeast, 
as  skimmed,  J oz. 


JJo.  11. 

Flour,  68  grams  ; water. 

6 oz.  at  25°  C. 

; Brighton  brewers' 

yeast,  \ oz. 

The  following  were  the  quantities  of  gas  evolved 

in  six  hours  : — 

No.  1 

91  *2  cubic  inches. 

No.  7 . . 

80*3  cubic  inches. 

No.  2 

..  40-8 

No.  8 

0*5 

No.  3 

..  32-3 

No.  9 . . 

1*0 

No.  4 

..  115.2 

No.  10  .. 

720 

No.  5 

. . 80-0 

No.  11  .. 

DO 

No.  6 

..  1*9 

Nos.  1 and  2 call  for  no  special  remark,  being  similar  in  character  to 
many  tests  previously  made.  The  quantity  of  flour  in  No.  3 is  double 
that  used  in  previous  experiments,  the  object  being  to  get  a mixture  which 
should  be  a nearer  assimilation  to  dough,  while  still  possessing  sufflcient 
fluidity  to  permit  the  escape  of  the  produced  gas.  As  might  be  expected, 
the  amount  of  gas  evolved  is  higher  than  in  tests  where  34  grams  were  used. 
Nos.  4 and  5 were  tests  with  the  compressed  brewers'  yeast — there  is  a 
more  rapid  evolution  of  gas  than  in  the  corresponding  tests  with  the  French 
distillers'  yeast  ; so  far,  the  verdict  would  be  in  favour  of  the  English 
yeast  as  being  a stronger  yeast.  This  verdict  is  borne  out  by  the  results 
of  commercial  use  of  the  yeast  for  brewing  purposes.  Next  comes  test 
No.  6,  the  results  of  which  are  most  remarkable  ; the  English  brewers' 
yeast,  which  had  been  by  far  the  stronger  in  both  yeast  mixture  and  sugar 
solutions,  causes  practically  no  evolution  of  gas  whatever  from  the  flour 
mixture.  On  the  next  day  some  of  the  experiments  were  repeated,  to- 
gether with  others.  No.  7 was  a duplicate  of  No.  5 (with  sugar)  and  yields 
similar  results  ; No.  8 was  a duplicate  of  No.  6,  and  of  the  two,  results  in  the 
production  of  still  less  gas  ; therefore,  the  results  of  the  first  day's  experi- 
ments were  confirmed  by  those  of  the  second.  In  No.  9,  there  was  added, 
in  addition  to  flour,  a half-ounce  of  sugar,  with  the  surprising  result  that 
in  this  case  also  only  one  cubic  inch  of  gas  was  evolved  in  six  hours.  No. 
10,  in  which  a local  brewers'  yeast  was  used,  showed  an  evolution  of  gas 
in  large  quantity  ; but  in  No.  11  the  same  yeast  caused  an  evolution  of 
but  one  cubic  inch  of  gas  in  six  hours.  The  foregoing  experiments  were 
made  on  the  date  given  in  1885,  and  were  published  by  one  of  the  authors 
in  The  Chemistry  of  Wheat,  Flour,  and  Bread,  in  1886. 


218 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


In  further  examination  of  this  point  the  following  experiments  were 
made  and  published  in  1895  : — 

No.  1.  Sugar,  20  grams  ; water,  200  c.c.  at  30°  C.  ; distillers’  yeast, 

1 gram. 

No.  2.  Flour  (soft  English),  50  grams  ; water,  200  c.c.  at  30°  C.  ; dis- 
tillers’ yeast,  1 gram. 

No.  3.  Sugar,  20  grams  ; water,  200  c.c.  at  30°  C.  ; brewers’  yeast 
(uncompressed),  2 grams. 

No.  4.  Flour,  50  grams  ; water,  200  c.c.  at  30°  C.  ; brewers’  yeast, 

2 grams. 

The  following  w^ere  the  quantities  of  gas  evolved  at  the  end  of  six  hours  : — 

No.  1 . . 334  cubic  centimetres.  No.  3 . . 516  cubic  centimetres. 

No.  2 . . 345  „ „ I No.  4 . . 36  „ 


It  will  be  noticed  once  more  that  whereas  the  brewers’  yeast  gave  more 
gas  from  sugar,  yet  it  was  practically  inoperative  on  flour,  confirming 
again  the  results  of  the  previous  series. 

Another  set  of  experiments  was  next  made  in  order  to  determine  the 
effect  of  the  presence  of  varying  quantities  of  flour  on  the  fermentation 
of  brewers’  yeast  and  sugar.  The  following  quantities  were  taken  : — 


Sugar. 

Flour. 

Water. 

Brewers’  Yeast. 

No.  1. 

10  grams. 

0 grams. 

200  C.C. 

2 grams. 

No.  2. 

55 

10  „ 

55 

55 

No.  3. 

55 

20  „ 

55 

No.  4. 

55 

30  „ 

55 

55 

No.  5. 

5 5 

40  „ 

55 

55 

No.  6. 

55 

50  „ 

55 

55 

At  the  end  of  six  hours  the  following  quantities  of  gas  had  been  evolved  : — 


No.  1 
No.  2 
No.  3 


. . 320  cubic  centimetres. 


50 

20 


55 


No.  4 
No.  5 
No.  6 


27  cubic  centimetres. 
17  „ 


The  addition  of  10  grams  only  of  flour  to  No.  2 was  sufficient  to  drop 
the  evolution  of  gas  from  320  c.c.  to  50  c.c.  in  the  six  hours,  while  20  grams 
of  flour  restricted  the  evolution  of  gas  to  20  c.c.  Beyond  this  amount 
an  increase  of  flour  did  not  cause  a marked  diminution  in  gas  : in  No.^  4, 
in  fact,  the  quantity  of  gas  is  more,  due,  doubtless,  to  some  irregularity 
in  the  experiment.  Nos.  5 and  6 had  both  evolved  17  c.c.  in  4 hours,  and 
remained  stationary  from  that  time  onwards. 

In  order  to  still  further  elucidate  these  points,  the  following  experi- 
ments were  made  : — 


A Series. 


Sugar. 

No.  1.  10  grams.  0 

No.  2.  „ 5 

No.  3.  „ 10 

No.  4.  „ 20 


Flour. 

Water. 

Brewers’  Yeast. 

grams. 

200  c.c. 

1 gram. 

55 

55 

5? 

55 

55 

55 

55 

5? 

In  all  cases  fermentation  was  conducted  at  a temperature  of  25°  C. 
The  following  are  the  quantities  of  gas  evolved  in  cubic  centimetres,  readings 
being  taken  at  the  end  of  each  hour  from  the  commencement.  The  figures 
opposite  the  brackets  are  the  quantities  of  gas  evolved  in  each  separate 
hour  : — 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  219 


Gas  Evolved. 


Time. 

No.  1. 

No.  2. 

No.  3. 

No.  4. 

0 

1 

7 

1 ^ 

1 ! 

1 

11 

1 hour. . 

8 

1 

16 

|l4 

1 12 

1 

^14 

2 hours 

23  i 

1 

20 

20 

25 1 

1 

1 

1 

[ 2 

1 ^ 

1 0 

0 

3 „ 

25 1 

20 

20 

25 1 

) 

i 

1 

[ 3 

1 2 

1 ^ 

1 

0 

4 „ 

28; 

\ 

\ 

22 

20 

i 25; 

1 

\ 

2 

1 ^ 

1 ^ 

1 

5 „ 

30; 

1 

I 

27 

24 

26; 

1 

1 

20 

1 ^ 

1 ^ 

4 

6 

50 

) 

36^ 

30^ 

CO 

o 

) 

B Series. 


These  were  similar  to  A,  except  that  compressed  distillers"  yeast  was 
used  throughout  instead  of  brewers"  yeast  ; quantities  as  before,  I gram. 

Gas  Evolved. 


Time. 

No.  1. 

No.  2. 

No.  3. 

No, 

. 4. 

0 

i 

1 

- 6 

“1 

9 

*^1 

■ ^ 

10 

1 hour. . 

11 

9^ 

1 

HI 

U2 

loj 

20 

2 hours 

17j 

1 

Us 

20 1 

U5 

20| 

i ' 

1 

[37 

30 1 

1 

[47 

3 „ 

65; 

1 

[25 

65 1 

[15 

! 57; 

• 

77 1 

[ « 

4 „ 

90; 

[73 

80; 

[37 

66; 

) 

[50 

85; 

[20 

5 „ 

163 

[84 

117; 

[58 

116 

[72 

105: 

[37 

6 „ 

247’ 

175 

) 

188' 

142 

; 

A curious  point  in  both  these  series  of  tests  is  the  falling  off  in  gas  evo- 
lution during  the  middle  portion  of  the  time  of  fermentation.  The  fer- 
menting vessels  of  all  the  numbers  of  each  series  were  placed  in  the  same 
water-bath,  and  so  were  subjected  to  the  same  conditions  of  temperature. 
The  two  series,  however,  show  the  same  characteristics  in  every  case, 
though  the  tests  w^ere  made  on  different  days.  With  brewers"  yeast  the 
addition  of  even  smaller  quantities  of  flour  exerts  in  every  case  a retarding 
influence  on  the  evolution  of  gas.  The  sample  of  yeast  employed  in  these 
experiments  was  in  the  liquid  form,  and  much  weaker  than  some  obtained 
for  the  tests  described  in  preceding  paragraphs.  Some  judgment  must, 
therefore,  be  exercised  in  comparing  the  results  of  one  series  with  others 
made  at  other  times  with  totally  different  yeasts. 

Flour  also  exerted  a retarding  influence  on  the  fermentation  with  dis- 
tillers" yeast. 


220 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


An  attempt  was  next  made  to  determine  if  possible  which  of  the  con- 
stituents of  flour  exerts  the  retarding  influence.  The  most  important  of 
these  are  starch,  gluten,  and  soluble  proteins.  A series  of  experiments 
with  starch  instead  of  flour  was  easily  arranged.  It  is  obviously  impossible 
to  incorporate  gluten  with  water  and  sugar  in  the  same, way  as  flour,  water, 
and  sugar  can  be  mixed,  so  no  direct  experiments  were  made  with  gluten. 
In  imitation  of  the  soluble  flour  proteins,  mixtures  were  made  of  water, 
sugar,  and  desiccated  white  of  egg  (albumin).  Particulars  follow  of  the 


various  fermentation  experiments  : — 

C Series. 

Sugar.  Wheat  Starch.  Water. 

Brewers’  Yeast. 

No.  I. 

10  grams. 

0 grams.  200  c.c. 

1 gram. 

No.  2. 

5? 

b jj  55 

yy 

No.  3. 

yy 

10  5, 

yy 

No.  4. 

yy 

20  „ 

Gas  Evolved. 

yy 

Time. 

No.  1. 

No. 

2. 

No.  3.  No.  4. 

0 

1 

, i 

»| 

^1 

1 

5 

1 

1 

1 ^ 

5 

1 

hour. . 

H 

[ 2 ! 

3 

1 

1 

' 3 

5 

8 

13  : 

2 

hours 

vl 

1 ! 

8 

8 

1 

1 

1 

[ 3 

io{ 

2 

1 

[ 4 

10  1 

3 

yy 

10 

1 1 

12j 

23  ! 

1 

5 

1 

[ ^ 

2 

4 

yy 

15j 

1 

' 1 

[17  ! 

15[ 

r 

10 

20 1 

[18 

25 

i r® 

1 40 

5 

yy 

32 1 

1 

'12 

25 1 
35^ 

10 

38 1 

[15 

13 

1 53^ 

6 

yy 

44^ 

1 

53^ 

1 

D Series. 

These  were  similar  to  C,  except  that  I gram  of  compressed  distillers’  yeast 
was  substituted  for  the  brewers’  yeast. 

Gas  Evolved. 


Time. 

No.  1. 

No.  2.  ' 

No.  3. 

No.  4. 

0 

*^1 

1 

t 9 

Il5 

1 

[17 

20 

1 hour.  . 

o] 

1 

15 1 

nj 

20 

1 

1 

■ 6 

|l5 

1 

[16 

19 

2 hours 

15 

1 

30 

33! 

1 

1 

39 

1 

1 

[13 

ll9 

1 

24 

27 

3 5, 

28 

1 

49 

57[ 

1 

1 

66 

1 

^22 

24 

73 

1 

30 

34 

4 ‘55 

50 1 

1 

87 1 

\ 

\ 

100 

1 

[45 

50 

47 

50 

5 5, 

95! 

[35 

123 

20 

143^ 

134j 

1 

[33 

150 

35 

185' 

0 ,5 

130^ 

1 

167^ 

1 

TECHNICAL  RESEARCHES  ON  FERMENTATION. 


221 


With  both  brewers’  yeast  and  distillers’  yeast  the  presence  of  starch 
is  accompanied  by  an  increased  evolution  of  gas.  The  increase  is  some- 
what erratic  in  the  brewers’  yeast  series,  but  still  is  very  noticeable.  With 
the  distillers’  yeast,  a regularly  increasing  amount  is  obtained  with  each 
increase  of  added  starch.  Wheat  starch,  then,  cannot  be  viewed  under 
these  conditions  as  the  agent  of  retardation  : the  curious  point  is  its  stimu- 
lating effect.  This  can  scarcely  be  ascribed  to  the  starch  itself.  Possibly 
a trace  of  stimulating  nitrogenous  matter  was  present  in  the  starch. 


. E Series. 

Sugar.  Albumin.  Water.  Brewers’  Yeast. 


No. 

1. 

10  grams. 

0 grams. 

200  c.c. 

1 gram, 

No. 

2. 

55 

0-5  „ 

55 

No. 

3. 

55 

1-0  „ 

55 

No. 

4. 

55 

2-0  „ 

55 

55 

No. 

5. 

55 

5-0  „ 

55 

55 

Gas  Evolved. 


E Series. 

These  were  similar  to  E,  except  that  1 gram  of  compressed  distillers’  yeast 
was  substituted  for  the  brewers’  yeast. 

Gas  Evolved. 


222 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


With  both  brewers’  and  distillers’  yeasts,  the  addition  of  a small  quantity 
of  albumin,  0 *5  grams,  depressed  the  evolution  of  gas  ; with  larger  quantities 
a decidedly  stimulating  action  occurred,  due  probably  to  more  or  less 
peptonisation  of  the  protein. 

With  starch  and  soluble  protein  matter  eliminated  from  among  the 
retarding  agents,  we  must  fall  back  on  gluten  as  the  probable  effective  body 
in  slowing  down  the  fermentation  of  flour  and  water.  This  effect  is  most 
likely  due  to  its  peculiar  physical  characters.  As  to  why  distillers’  yeast 
is  so  much  better  able  to  overcome  this  resistance  of  gluten  than  is  brewers’ 
yeast  is  a matter  still  awaiting  investigation.  On  the  assumption  that 
the  explanation  may  possibly  be  found  in  there  being  differences  in  their 
power  of  inducing  physical  alteration,  experiments  were  made  to  elucidate 
this  point.  Two  doughs  were  machine-mixed  from  the  following  ingredi- 
ents : — 

No.  1,  Spring  American  Second  Patent  Flour.  . 840  grams 

Salt 9 „ 

Water  . . . . . . . . . . 466  ,, 

Compressed  Distillers’  Yeast  . . . . 15  ,, 

No.  2 same  as  No.  1,  except  that  30  grams  of  liquid  brewers’  yeast 
were  substituted  for  the  distillers’  yeast. 

The  temperatures  of  the  doughs  when  made  was  83°  F.  ; they  were 
kept  warm,  and  covered  with  a damp  cloth  to  prevent  evaporation.  At 
intervals,  portions  of  each  dough  were  removed,  and  kneaded  to  exactly 
the  same  extent  in  a small  doughing  machine,  so  as  to  drive  out  the  whole 
of  the  gas.  The  stiffness  of  this  dough  was  then  tested  by  the  viscometer 
(see  Chapter  XXVI.),  and  the  percentage  of  gluten  determined.  The 
following  are  the  results  : — 


Comparative  Tests  with  Distillers’  and  Brewers’  Yeasts^ 


Time  of  Test. 

■'  No.  1,  Distillers’. 

1 No.  2,  Brewers’. 

Viscometer 

Reading. 

Wet  Gluten 
Per  Cent. 

Dry  Gluten 
Per  Cent. 

Viscometer 

Reading. 

Wet  Gluten 
Per  Cent. 

Dry  Gluten 
Per  Cent. 

Immediate  . . 

110" 

26-7 

8-3 

138"  1 

28-7 

9d 

1 hour 

94" 

28-8 

8-7 

‘ 73"  ! 

29-7 

8-9 

3 hours 

173" 

26-7 

8-5 

1 65"  i 

32-0 

9-2 

5 „ 

96" 

28-7 

9-1 

38"  : 

31-3 

8-9 

10  „ 

50" 

27-3 

8-7 

37" 

; 30-7 

9-2 

22  „ 

101" 

28-7 

8-9 

60" 

32-7 

9-2 

With  No.  1,  the  viscometer  result  at  the  end  of  three  hours  was  some- 
what anomalous,  but  was  confirmed  by  a duplicate  test.  In  each  case 
there  is  a falling  off  in  stiffness  during  the  ten  hours,  but  considerably 
more  with  the  brewers’  than  the  compressed  yeast.  On  standing  over- 
night, tlie  viscosity  of  both  had  risen.  No  great  alteration  occurs  during 
this  time  in  the  percentage  of  dry  gluten  obtained,  but  in  the  case  of  the 
brewers’  yeast  dough  the  gluten  became  much  softer  and  more  watery, 
this  being  shown  by  a marked  increase  in  weight  in  the  wet  state.  The  greater 
softening  of  the  gluten  may  be  the  cause  of  brewers’  made  dough  yielding 
a “ runny  ” loaf  ; but  this  does  not  account  for  the  much  slower  evolution 
of  gas  wlien  a thin  batter  of  flour,  water,  and  sugar  is  subjected  to  fermenta- 
tion. The  probable  solution  of  this  problem  is  further  dealt  with  in  para- 
graph 378. 


223 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


377.  Brewers*  Yeast  and  Ferments. — ^When  brewers’  yeast  is  employed 
for  bread-making  purposes  it  is  usual  first  to  allow  the  yeast  to  develop 
in  a “ ferment,”  generally  composed  of  boiled  potatoes  rubbed  down  through 
a sieve  into  water,  and  a little  raw  flour  added.  In  order  to  ascertain  the 
effect  of  different  substances  as  constituents  of  a “ ferment,”  the  following 
experiments  were  made  : — 

Water. 

No.  1.  Sugar,  I gram  . . . . . . 200  c.c. 

No.  2.  Boiled  potatoes,  5 grams  . . . . ,, 

No.  3.  Filtered  potato  juice,  10  grams  . . ,, 

No.  4.  Malt  extract,  2*5  grams  . . . . ,, 

No.  5.  Diastatic  malt  extract,  2*5  grams.  . ,, 

No.  6.  ,,  ,,  ,,  killed,  2*5  grams  ,, 

No.  6.  was  precisely  similar  to  No.  5,  except  that  the  solution  had  been 
raised  to  the  boiling  point,  with  the  view  of  destroying  the  diastase  present. 

The  following  were  the  quantities  of  gas  evolved  after  six  and  a half 
hours’  fermentation  at  30°  C.  : — 


Brewers’  Yeast. 

2 grams. 


No.  I . . 125  cubic  centimetres. 

No.  2 . . 25 

No.  3 ..  16 


No.  4 . . 160  cubic  centimetres. 

No.  5 ..  76 

No.  6 . . 74 


After  fermentation  had  ceased,  and  about  twenty  hours  from  the  com- 
mencement of  the  experiment,  50  grams  of  flour  were  added  to  each  “ fer- 
ment,’' and  the  bottle  again  immersed  in  the  bath  at  30°  C.,  and  readings 
taken  of  the  quantities  of  gas  evolved.  At  the  end  of  six  hours,  these 
were  : — 

No.  1 . . 23  cubic  centimetres.  i No.  4 . . 43  cubic  centimetres. 

No.  2 ..11  „ > No.  5 ..  15“ 

No.  3 . . 31  „ : No.  6 . . 30 

As  a ferment  constituent  potato  juice  causes  the  evolution  of  less  gas 

than  do  potatoes,  while  as  a stimulant  on  the  yeast’s  after-power  of  inducing 
fermentation  in  flour  the  juice  is  far  the  more  efficacious.  While  the  gas 
evolved  in  the  two  diastatic  malt  extract  solutions  is  practically  the  same, 
that  in  which  the  diastase  had  been  destroyed  acted  in  this  case  as  the  more 
energetic  after-stimulant  of  flour  fermentation.  Possibly  a concentrated 
solution  of  diastase  may  exert  some  retarding  influence  on  the  energy  of 
yeast.  In  an  experiment  conducted  in  this  fashion  the  action  of  the  yeast 
in  the  mixture  of  flour  and  water  is  less  in  all  cases,  except  No.  4,  than  when 
the  yeast  and  flour  mixture  are  fermented  direct  (36  cubic  centimetres). 
During  the  working  of  the  “ ferment,”  the  operation  was  carried  on  without 
access  of  air,  a condition  which  may  have  had  a retarding  action  on  the 
energy  of  the  yeast  {Science  and  Art  of  Bread-making,  Jago,  1895,  p.  223, 
et  seq.). 


378.  Toxicity  of  Flour  to  Yeast. — ^In  view  of  recent  investigations  on 
the  toxic  behaviour  of  flour  towards  yeast,  the  experiments  described  in 
the  foregoing  paragraphs  have  some  historic  interest.  They  serve  to 
show  that  flour  retards  the  fermentative  action  on  sugar  of  both  distillers’ 
and  brewers’  yeasts,  but  that  the  latter  is  far  more  affected.  That  the 
retardation  is  not  due  either  to  starch  or  carbohydrate  bodies  is  very  appar- 
ent. Soluble  proteins  in  the  form  of  egg-albumin  are  shown  to  possess 
little  or  no  retarding  effect,  though  this  is  scarcely  conclusive,  since  egg- 
albumin  and  soluble  wheat  proteins  are  not  necessarily  identical  in  this 
respect.  Finally  by  a process  of  elimination,  rather  than  direct  proof, 
the  suggestion  is  made  that  the  inhibitive  action  is  due  to  the  gluten  of 
the  flour,  though  the  gluten  action  was  evidently  regarded  rather  as  a 
physical  than  a chemical  one.  In  this  relation  it  is  interesting  to  note 


224 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  work  that  has  been  done  on  what  are  called  “ toxalbumins."'  In  investi- 
gations carried  out  on  the  proteins  of  the  seed  of  Ricinus,  it  has  been  shown 
that  its  toxic  property  belongs  to  the  protein,  and  is  closely  related  to 
the  proportion  of  coagulable  albumin  contained  in  various  fractions  of  the 
seed  protein.  It  seems,  therefore,  almost  certain  that  true  toxalbumins 
occur  in  seeds  {The  Vegetable  Proteins,  Osborne,  1909,  p.  96).  Michaelis 
has  also  pointed  out  that  foreign  protein  matter  is  under  all  circumstances 
a deadly  poison  for  yeast,  and  that  this  is  rendered  innocuous  by  the 
proteolytic  enzyme  present. 

Baker  and  Hulton  have  recently  (1909, 1910)  re-investigated  this  matter, 
and  have  confirmed  the  just  quoted  conclusions  of  one  of  the  authors,  viz., 
that  the  presence  of  flour  inhibits  the  fermentation  of  a solution  of  sugar 
by  brewers’  yeast.  Independently,  Lange,  in  the  course  of  a series  of 
investigations,  conducted  in  1904  and  1905,  re-discovered  that  the  flour  of 
wheat  and  certain  other  grains  exercised  a poisonous  action  on  yeast,  and 
especially  brewers’  types  of  yeast.  The  following  is  a synopsis  of  the  work 
and  conclusions  of  Lange,  Henneberg,  Hay  duck,  Wendel,  Baker,  and  Hulton 
on  this  and  closely  allied  subjects.  The  authors  are  indebted  to  the  Treatise 
on  Brewing  by  Sykes  and  Ling  for  a resume  of  a lecture  by  Delbriick  before 
the  London  section  of  the  Institute  of  Brewing  in  1906,  from  wfiiich  many 
of  the  conclusions  of  the  above  named  German  authorities  are  gleaned. 
The  lecture  is  reported  more  fully  in  Journ.  Inst.  Brewing,  1906,  642. 
From  Hayduck’s  researches,  the  lecturer,  Delbriick,  derived  the  laws  that 
in  the  production  of  yeast,  the  fermenting  power  is  in  inverse  ratio  to  the 
multiplication  of  the  yeast-cells.  Moderate  multiplication  produced  a 
yeast  rich  in  protein  ; a rapid  multiplication,  on  the  other  hand,  produced 
a yeast  poor  in  protein.  Therefore  everything  which  hindered  multiplica- 
tion, such  as  a low  temperature,  the  shutting  off  of  air,  lack  of  movement, 
fermentation  under  carbon  dioxide  pressure,  conduced  to  the  yielding  of 
a yeast  which  was  rich  in  protein  and  in  fermenting  power.  Obviously, 
therefore,  these  are  among  the  matters  to  be  considered  in  the  manufacture 
of  a vigorous  yeast.  It  is  also  evident  that  such  treatment  must  not  be 
carried  to  extremes,  since  an  undue  restriction  of  multiplication  would 
seriously  restrict  the  output  of  yeast.  In  yeast  manufacture  the  con- 
ditions must  be  so  balanced  as  to  obtain  the  maximum  of  vigour  combined 
with  a fair  production  of  yeast. 

Delbriick  also  dealt  with  the  inquiry  which  is  so  frequently  made, 
Wliat  important  physiological  significance  has  the  peculiar  dynamic  effect 
of  the  splitting  up  of  sugar  into  alcohol  and  carbon  dioxide  ? To  this  he 
replies  that  it  is  easy  to  say  that  a sort  of  subtle  respiration  process  was 
going  on  here — that  the  cleavage  was  a hidden  source  of  heat  ; but  the 
significance  of  this  activity  was,  particularly  from  a zy mo -technological 
point  of  view,  far  more  comprehensive.  It  w^as  known  that  the  most 
powerful  defensive  agencies  of  the  yeast  against  the  attacks  of  foreign 
organisms  lay  in  its  fermentation  energy.  Delbriick  had  always  looked 
upon  the  fermentative  effect  of  the  yeast  in  this  light,  and  had  demon- 
strated that  its  organism,  in  sending  out  carbon  dioxide  and  alcohol, 
thus  protected  itself  against  all  the  organisms  for  which  these  substances 
were  j)oisonous.  Tlie  effect  of  the  carbon  dioxide  is  ten  times  as  deadly 
as  that  of  tlie  alcohol.  Delbriick  therefore  arrives  at  the  conclusion  that 
zymfise  (the  yeast  enzyme  which  decomposes  sugar  into  alcohol  and  carbon 
dioxide)  is  not  only  a respiration  enzyme,  but  also  a fighting  enzyme.  He 
also  regards  the  proteolytic  enzyme  of  yeast,  as  a part  of  its  fighting  organisa-  , 
tion,  inasmuch  as  it  attacks  all  inimical  organisms,  dissolving  and  killing 
them.  As  already  mentioned,  foreign  protein  matter  is  a poison  to  yeast,  j 
and  this  is  rendered  innocuous  by  the  action  of  the  proteolytic  enzyme  by  || 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


225 


M^iich  it  is  degraded.  The  law  that  in  the  struggle  for  existence,  those 
organisms  which  specialised  in  the  production  of  fighting  substances  and 
in  the  cultivation  of  fighting  enzymes,  would  be  the  strongest,  applies 
especially  to  the  micro-organisms.  Lactic  acid  bacteria  possessed  means 
of  defence  in  the  lactic  acid  enzyme,  while  the  butyric  acid  bacteria  were 
similarly  protected  by  the  production  of  butyric  acid,  a substance  which 
is  pernicious  in  its  effects  on  other  organisms.  It  was  in  the  course  of 
these  researches  that  Lange  independently  re-discovered  that  bruised 
grain  (or  bran)  or  meal,  or  even  an  aqueous  extract  of  them,  had  a poisonous 
effect  on  yeast.  He  further  found  that  different  kinds  of  yeast  varied 
in  susceptibility  to  this  poisonous  action.  Thus  the  distillers'  yeast  races 
were  capable  of  offering  resistance,  but  such  power  was  less  marked  in 
brewers'  top -fermentation  yeast,  and  still  less  so  in  the  bottom-fermentation 
type  of  brewers'  yeast.  As  to  the  nature  of  these  poisonous  substances, 
there  was  some  probability  that  they  belonged  to  the  proteins  and  to  the 
enzymes  produced  by  them,  since  the  injurious  action  could  be  neutralised 
by  heating  the  grain  or  its  aqueous  extract.  The  following  are  some  of 
the  more  important  conclusions  of  the  German  authorities.  The  toxic 
action  only  becomes  manifest  when  the  yeast  and  cereals  are  present  together 
in  distilled  water.  Rye,  wheat,  and  barley,  in  the  form  of  grits  or  flour, 
placed  with  bottom-fermentation  beer-yeast  in  a solution  of  saccharose, 
will  kill  up  to  99  per  cent,  of  the  yeast  in  a few  minutes.  Maize  and  oats 
do  not  show  this  toxic  action.  By  agitation  with  distilled  water,  the  flour 
of  rye  and  wheat  furnish  extracts  that  are  also  toxic  toward  beer-yeast, 
but  to  a far  less  extent  than  the  corresponding  solid  substances.  The 
protein  sludge  separating  from  the  coarser  particles  when  rye  grits  are 
shaken  up  with  water  is  specially  poisonous.  The  same  effect  is  produced 
by  the  glutinous  mass  obtained  by  kneading  wheaten  flour  under  water. 
It  is  probable  that  the  toxic  substance  must  be  sought  among  the  proteins,  or 
may  be  produced  therefrom  by  the  action  of  the  yeast.  All  these  toxie 
effects  are  completely  obviated  by  the  addition  of  a small  quantity  of 
inorganic  salts  to  the  solution,  lime  salts  being  the  most  effective,  and 
next  to  them  magnesia  salts.  A partial  or  complete  removal  of  the  toxic 
action  can  be  effected  even  by  replacing  distilled  water  by  tap-water. 
Among  other  substances  exerting  a strongly  poisonous  action  on  low- 
fermentation  beer-yeast  is  egg -albumin.  Wheaten  flour  seems  also  to 
exert  a toxic  action  on  high-fermentation  distilling  yeast,  but  this  requires 
confirmation  {Treatise  on  Brewing,  Sykes  and  Ling). 

These  conclusions,  it  will  be  noticed,  apply  to  bottom-fermentation 
beer-yeast,  whereas  in  the  experiments  previously  described  as  having 
been  made  by  one  of  the  authors  top -fermentation  beer-yeast  was  employed. 
This,  although  admittedly  less  susceptible  to  the  inhibitory  action  of  the 
active  cereals,  is  nevertheless  similarly  affected.  Further,  in  these  experi- 
ments, no  definite  retarding  action  was  caused  by  the  addition  of  egg- 
albumin.  It  is  possible  that  the  low  temperature  evaporation  of  this 
body  to  dryness  in  the  preparation  of  the  desiccated  product  may  have 
modified  its  inhibitive  action. 

379.  Baker  and  Hulton’s  Researches. — ^In  1909,  these  writers  communi- 
cated to  the  Society  of  Chemical  Industry  the  results  of  some  researches 
on  the  action  of  wheaten  flour  on  brewers'  yeast.  This  was  followed  by 
a paper  on  The  “Toxins  in  Cereals,”  which  appeared  in  the  Journal  of  the 
Institute  of  Brewing  in  1910.  The  experimental  work  confirms  that  pre- 
viously described,  and  among  other  things  goes  to  show  that  with  mixtures 
of  flour  and  water,  tap-water  enables  a greater  amount  of  gas  to  be  evolved 
than  does  distilled  water.  Thus  with  20  grams  of  Hungarian  flour,  50  c.c. 

Q 


226 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  water,  and  1 gram  of  unwashed  pressed  brewers’  yeast,  fermented  at 
110°  F.,  the  following  results  were  obtained  at  the  end  of  four  hours  ; — 


Carbon  Dioxide  Evolved. 

Brewers’  Yeast  and  Distilled  Water  . . . . 10  c.c. 

Distillers’  ,,  ,,  ,,  ....  287  „ 

Brewers’  Yeast  and  Tap- water  . . . . . . 35  ,, 

Distillers’  ,,  „ • • • • • • 287  „ 

The  tap- water  contained  in  grains  per  gallon  : — 

Total  Solids  2142 

Solids  after  ignition  . . . . . . . . . . 19*74 

Silica  0*28 

Lime  . . . . . . . . . . . . . . 7*60 

Magnesia  . . . . . . . . . . . . . . 0*71 

Sulphuric  Acid  (SO3)  . . . . . . . . . . 2*69 

Potash  . . . . . . . . . . . . . . 0*42 

Soda  . . . . . . . . . . . . . . 1*26 

Chlorine  . . . . . . . . . . . . . . 1*40 

Nitric  Acid  (N2O5)  . . . . . . . . . . 0*31 


Using  the  tap-water  it  will  be  noticed  that  the  activity  of  the  brewers’ 
yeast  is  much  increased.  On  examination  of  the  results  caused  by  the 
addition  of  various  inorganic  salts  to  tap-water,  it  was  found  that  potassium 
sulphate,  calcium  chloride,  sodium  chloride,  and  many  other  salts  act  as 
accelerants.  Baker  and  Hulton  regard  potassium  sulphate  as  the  most 
favourable  of  these,  and  find  that  a solution  containing  0*6  gram  per 
100  c.c.  exerts  a very  decided  accelerating  action.  They  make  the  follow- 
ing suggestion  as  to  the  reason  of  the  difference  between  the  two  yeasts 
(distillers’  and  brewers’) — 

In  a distillery  wash,  before  the  yeast  is  introduced,  there  are  present 
large  quantities  of  raw  cereals,  such  as  barley  and  rye,  containing  toxins, 
and  since  the  distiller  pitches  his  yeast  into  unboiled  wort  and  therefore 
one  with  this  cereal  poison  still  active,  only  those  yeast  cells  which  can 
survive  and  are  immune  to  such  toxic  substances  and  can  reproduce  in 
this  environment  will  carry  on  the  race,  giving  rise  to  cells  inheriting  this 
advantageous  variation.  There  will  thus  be  obtained  in  a few  generations 
by  natural  selection  what  is  to  all  intents  a new  species  bearing  this  char- 
acter of  immunity  to  cereal  poison.  Mdien  such  yeast  is  used  for  bread- 
making,  where  it  is  again  exposed  to  the  action  of  the  toxic  substance  in 
wheaten  flour,  the  high  gas  yield  at  once  shows  that  it  is  now  immune, 
wliile  brewers’  yeast  which  has  always  been  grown  in  a boiled,  and  therefore 
non-poisonous  wort,  is  readily  susceptible.  The  accelerating  influence 
of  potassium  sulphate,  sodium  chloride,  etc.,  on  the  fermentation  of  flour 
with  brewers’  yeast  is  thus  seen  to  be  correlated  with  the  protective  function 
these  salts  exert  on  the  yeast  by  negativing  the  toxic  effect  of  the  flour, 
wliile  distillery  yeast  which  is  already  immune  to  these  toxins,  from  having 
been  grown  in  their  presence,  needs  no  such  protection,  and  is,  in  fact, 
not  activated  by  these  salts  {Journ.  Inst.  Chem.,  July,  1909). 

Baker  and  Hulton  do  not  attribute  the  protective  action  of  potassium 
sulphate  to  any  “ salting  out  ” of  proteins,  but  conceive  that  it  may  lie 
in  some  kind  of  physiological  stimulation  of  the  yeast,  whereby  it  is  rendered  [ 
more,  resistant  to  an  unsuitable  environment.  They  further  point  out  | 
that  brewers’  yeast,  which  was  formerly  used  for  bread-making,  is  now  | 
practically  useless,  tlie  reason  being  possibly  due  to  the  fact  that  modern  ! 
flours  being  better  milled  contain  a smaller  proportion  of  fibre,  husk,  etc.,  | 
than  formerly.  The  husk  probably  has  a protective  action  towards  brewers’ 
yeast  similar  to  that  of  salts  (“  Toxins  in  Cereals,”  Journ.  Inst.  Brewing, 
xvi,  April,  1910).  11 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


227 


In  making  this  suggestion  the  writers  have  apparently  overlooked  the 
fact  that  when  brewers’  yeast  was  so  largely  employed  for  bread-making, 
it  was  the  custom  to  use  a ferment  consisting  of  boiled  potatoes  with  their 
skins  on,  the  water  in  which  they  were  boiled,  and  raw  flour.  The  yeast 
was  allowed  to  work  and  multiply  in  this  mixture  before  being  introduced 
into  the  sponge  (earlier  dough  stage).  The  stimulating  effect  of  potatoes 
as  an  agent  in  fermentation  has  been  already  described  in  paragraphs  372 
and  373. 

Experimental  Work. 

380.  The  student  who  has  the  opportunity  will  do  well  to  perform  for 
himself  most  of  the  experiments  described  in  this  chapter,  and  compare 
the  results  he  obtains  with  those  here  recorded.  He  should  commence 
by  making  duplicate  tests  with  the  same  yeasts,  in  order  to  gain  the  requisite 
accuracy  and  practice  in  working.  The  experiments  described  in  the 
365th  and  following  paragraphs,  or  as  many  of  them  as  practicable,  should 
be  performed.  It  is  recommended  that  25°  C.  be  adopted  as  the  standard 
temperature  throughout  the  experiments,  instead  of  30°  C.  Practical 
directions  follow. 

381.  Apparatus  requisite. — ^Water-bath  to  hold  yeast  bottles,  sets  of 
yeast  testing  apparatus,  pneumatic  troughs,  bunsen  burner  and  automatic 
temperature  regulator,  thermometer,  etc. 

The  water-bath  may  conveniently  consist  of  a large  iron  saucepan  (or  Scotch 
“ goblet  ”)  ; to  this  should  be  attached  a side-tube,  by  means  of  which  the 
height  of  the  water  in  the  bath  may  be  regulated  : for  description  of  this  very 
useful  device  see  “ The  Hot- Water  Oven,”  Chapter  XXVI.  Adjust  the  height 
of  the  water  in  the  bath,  so  that  the  yeast  bottles,  when  charged,  shall  be  on 
the  verge  of  floating,  the  surface  of  the  liquid  in  the  bottle  will  then  be  about 
an  inch  below  that  of  the  water  in  the  bath.  During  very  hot  weather, 
and  particularly  when  working  at  the  lower  temperatures,  it  is  advisable 
to  have  a stream  of  cold  water  running  through  the  bath.  For  this  purpose, 
lead  the  end  of  a piece  of  bent  tube,  connected  with  a water  tap,  into  the 
bath  over  the  top,  on  the  opposite  side  to  side-tube  before  referred  to  : turn 
on  a small  stream  of  water  through  this  bent  tube,  scarcely  more  than 
what  would  cause  rapid  dropping  from  its  end.  Water  will  then  be  con- 
tinually finding  its  way  in  through  this  tube,  and  making  its  exit  through 
the  side-tube  : thus  lowering  the  temperature  when  necessary.  Do  not 
let  the  stream  from  this  cold  water  tube  impinge  directly  on  either  of  the 
yeast  bottles. 

The  construction  and  arrangement  of  the  yeast  testing  apparatus  and 
pneumatic  troughs  have  already  been  sufficiently  fully  described. 

382.  Automatic  Temperature  Regulator. — ^The  bath  is  warmed  b}^  means 
of  a bunsen  burner  arranged  underneath,  and,  in  order  to  maintain  the 
temperature  at  any  desired  point,  an  automatic  regulator  is  employed. 
As  an  unvarying  temperature  is  necessary  for  several  other  chemical  opera- 
tions, a detailed  description  of  such  an  automatic  regulator  is  given.  There 
are  several  of  these  instruments  made  and  sold  under  various  names  ; but 
for  general  purposes  the  following  modification,  designed  by  one  of  the 
authors,  and  shown  in  Fig.  22,  is  simple  and  not  likely  to  get  out  of  order. 

The  instrument  consists  of  a bulb,  a,  about  4 inches  long,  and  | inch 
in  diameter  ; to  this  is  attached  a stem,  h b,  about  a J inch  diameter,  and 
6 inches  long.  This  stem  bends  over  at  the  top,  and  is  connected  with  a 
U-tube,  c d e,  ^ inch  diameter,  in  which  are  blown  2 bulbs  as  figured,  / /, 
about  I inch  diameter.  The  one  end,  c,  of  this  U-tube  is  closed  with  a 
.stopper,  g,  which  is  ground  in  with  extreme  accuracy.  From  the  centre 


228  THE  TECHNOLOGY  OF  BREAD-MAKING. 

of  the  bottom  of  this  stopper,  a hole  is  bored  upwards  for  a short  distance, 
which  hole  joins  another  bored  inwards  through  the  side  of  the  stopper  ; 

this  hole,  therefore,  affords  a passage  up  through  the 
^ ^ bottom  of  the  stopper  and  out  through  its  side.  A cor- 
/ 5^  responding  hole  is  bored  through  the  side  of  the  neck, 

c,  of  the  U-tube,  so  that  if  the  stopper  be  turned  so  that 
these  two  holes  coincide,  a passage  is  provided  from  the 
U-tube  to  the  exterior  ; this  exit  may  be  closed  at  will 
by  slightly  turning  this  stopper,  g.  To  the  other  end, 
c,  of  the  U-tube,  c d e,  is  sealed  a bent  tube,  h i j ; 
below  the  point,  e,  this  tube,  h i j,  is  made  much  finer, 
having  its  smaller  end,  j,  inch  in  diameter,  and 
ground  obliquely  as  shown  in  the  figure.  Below  the 
joint,  e,  but  as  near  to  it  as  possible,  an  outlet  tube,  hi, 
is  sealed  into  the  U-tube,  c d e.  This  completes  the 
regulator  ; the  method  of  using  the  instrument,  and 
its  principle,  may  be  conveniently  described  together. 

By  means  of  a screw-clamp  carried  on  a retort- 
stand,  or  any  other  suitable  holder,  fix  the  regulator 
upright,  and  so  that  the  bulb,  a,  shall  be  wholly  im- 
mersed in  the  water  of  the  bath,  and  the  ends  of  the 
tubes,  h and  I,  projecting  over  its  side.  The  regulator 
should  be  perfectly  rigid  when  fixed  ; the  clamp  is  best 
screwed  on  to  the  stem,  h h.  Connect  up  h by  india- 
rubber  tubing  with  the  gas  tap,  and  join  up  I to  the  bun- 
sen  burner.  Partly  fill  the  U-tube,  c d e,  with  care- 
fully cleaned  mercury  through  c.  Turn  on  the  gas 
and  light  the  bunsen  burner,  then  continue  the  filling 
oi  c d e with  mercury  until  the  level  rises  sufficiently 
high  in  the  limb,  d e,  to  very  nearly  close  the  end  of 
jet  j.  The  quantity  of  mercury  added  should  be  suffi- 
cient to  just  begin  to  shut  off  the  supply  of  gas  to  the 
bunsen  ; it  is  evident  that  then  a very  slight  rise  in 
level  of  the  mercury  would  either  considerably  diminish 
or  entirely  shut  off  the  gas  from  the  burner.  Next  heat 
a little  india-rubber  sufficiently  to  liquefy  it  ; smear  the 
stopper,  g,  and  its  neck  with  this  liquid,  taking  care  to 
preserve  a clear  passage  through  the  hole  in  the  stopper. 
Then  pour  some  of  the  strongest  alcohol  obtainable, 
which  has  been  recently  boiled,  through  c,  until  the 
bulb,  a,  its  stem,  h h,  and  the  part  of  c are  completely 
^ filled  with  alcohol.  Insert  the  stopper,  g,  so  that  the 

hole  through  it  is  open  ; the  excess  of  spirit  escapes.  It 
sometimes  happens,  in  filling  the  instrument  with  spirits, 
Regulator.  that  the  level  of  the  mercury  in  the  U-tube  is  dis- 
turbed, the  spirits  floating  on  its  surface  at  c,  for- 
cing up  the  level  in  e sufficiently  far  to  entirely  close  the  jet,  j.  Should 
this  happen,  the  mercury  must  again  be  adjusted  by  removing  a small 
drop  by  means  of  a fine  pipette.  Having  made  these  adjustments,  the 
instrument  may  be  regulated  for  any  desired  temperature.  Place  a ther- 
mometer in  the  bath,  so  that  the  height  of  the  mercury  can  be  easily  read 
and  that  its  bulb  does  not  touch  the  bottom.  Suppose  it  is  wished  to 
maintain  the  bath  at  25°  C.,  turn  the  stopper,  g,  so  that  the  hole  is  open, 
and  light  up  the  burner.  The  gas  finds  its  way  through  the  tubes,  h i j h I, 
in  the  directions  of  the  arrows.  As  the  temperature  of  the  water  m the 
bath  increases,  so  does  that  of  the  spirits  in  a.  With  a rise  in  temperature 


a 


TECHNICAL  RESEARCHES  ON  FERMENTATION. 


229 


the  alcohol  expands,  and  a small  portion  finds  its  way  out  through  the 
hole  in  the  stopper,  g.  Watch  the  thermometer  carefully,  and  when  the 
temperature  stands  at  about  one- tenth  of  a degree  below  25°  C.,  turn  the 
stopper,  g,  so  as  to  close  the  hole  through  it.  The  spirits,  in  expanding, 
now  find  no  means  of  escape,  and  therefore  drive  down  the  mercury  in  c d, 
causing  a corresponding  rise  in  d e \ the  consequence  is  that  the  jet,  j,  is 
either  wholly  or  partly  closed,  and  the  gas  either  completely  or  partly 
shut  off  from  the  burner.  The  bunsen  used  should  have  a cap  of  fine  wire 
gauze  fastened  on  to  it,  so  as  to  prevent  its  lighting  at  the  bottom  when 
the  flame  is  turned  very  low.  A small  pin-hole  burner  should  be  fixed  to 
the  bunsen,  and  fed  from  an  independent  supply,  so  as  to  re-light  it  should 
the  regulator  turn  it  completely  out  ; this  “ pilot burner  must  be  turned 
down  so  as  to  only  give  a flame  about  J inch  high,  and  should  not  be  able 
to  appreciably  warm  the  bath.  The  regulator  will  at  first  most  likeiy  shut 
off  the  gas  completely  ; the  bath  will  then  cool  slightly,  and  as  the  alcohol 
in  a contracts,  the  level  of  the  mercury  in  d e will  fall,  and  so  the  jet,  j, 
will  once  more  be  opened,  and  a passage  of  gas  to  the  burner  permitted. 
With  this  regulator  properly  set,  the  temperature  keeps  between  two 
extremes  that  after  a short  time  closely  approach  each  other  ; in  fact,  the 
mercury  so  adjusts  itself  as  to  partly  close  the  aperture  j,  allowing  just 
sufficient  gas  to  pass  to  keep  the  bath  at  a constant  temperature.  The 
end  of  j is  cut  obliquely  in  order  to  prevent  the  mercury  sticking  to  it, 
and  so  acting  irregularly.  Alcohol  is  used  in  a instead  of  air,  because  it 
is  not  affected  by  changes  of  atmospheric  pressure  ; when  temperatures 
above  the  boiling  point  of  alcohol  are  required,  the  instrument  must  be 
used  with  air,  or  else  some  liquid  having  a sufficiently  high  boiling  point. 
Alcohol  is  preferable  to  water,  because  it  has  a much  higher  co-efficient  of 
expansion,  that  is,  for  an  equal  rise  in  temperature  it  expands  much  more. 
With  the  instrument  set  as  described,  it  should  maintain  the  temperature 
closely  at  25°  C.  ; if  it  should  be  found  to  be  somewhat  higher,  the  instru- 
ment may  be  made  more  delicate  by  adding  a very  little  more  mercury, 
or  it  may  be  shut  off  somewhat  earlier  ; thus,  if  it  be  found  to  give  a con- 
stant temperature  0*4°  over  that  at  which  the  stopper,  g,  is  shut  off,  then 
all  that  is  necessary  is  to  always  shut  off  at  0*4°  below  any  temperature 
that  may  be  required.  Should  the  temperature  be  too  low,  it  may  be  raised 
•slightly  by  carefully  turning  the  stopper,  g,  momentarily,  until  the  slightest 
drop  of  spirits  oozes  out  ; if  the  temperature  is  too  high,  the  bath  must 
be  cooled  down,  and  again  regulated  on  the  rising  temperature.  If  the 
bath  is  required  to  be  used  for  several  days  at  the  same  temperature,  all 
that  is  requisite  is  to  turn  off  the  gas  when  the  day’s  work  is  done  ; as  the 
bath  cools,  the  mercury  rises  in  c d through  contraction  of  the  alcohol  ; 
the  bulbs,  / /,  are  provided  in  order  to  allow  of  this  rise  without  its  altering 
the  regulator.  When  the  bath  is  next  required,  simply  turn  on  the  gas, 
and  the  regulator,  without  any  attention,  will  maintain  the  temperature 
■at  the  point  for  which  it  was  adjusted.  The  advantage  of  this  form  of 
regulator  is  that  it  keeps  perfectly  constant  for  a very  long  time,  as  there 
are  no  parts  to  shift,  or  places  from  which  leakage  may  occur  ; the  stopper, 
•g,  smeared  with  melted  india-rubber,  is  perfectly  air-tight.  Grease  will 
not  answer  as  well  as  the  india-rubber,  as  it  is  dissolved  by  the  alcohol. 

383.  Method  of  Testing. — ^To  make  one  or  more  experiments  proceed 
in  the  following  manner  : — First,  carefully  enter  in  the  notebook  the 
particulars  of  each  experiment,  and  number  them  : place  corresponding 
numbers  on  the  bottles.  Regulate  the  water-bath  at  the  desired  tempera- 
ture, and  place  in  it  a flask  containing  sufficient  water  for  the  experiments 
ithat  are  to  be  made.  Having  cleaned  the  whole  apparatus,  arrange  in 


230 


THE  TECHNOLOGY  OF  BREAD-MAKING 


order  the  generating  bottles  required,  and  weigh  out  and  introduce  into 
them  the  yeast  mixture  or  other  substance  to  be  fermented.  Next  weigh 
the  yeast,  taking  care  that  a good  representative  sample  is  obtained.  With 
pressed  yeast  cut  a thin  slice  off  the  middle  of  the  slab,  avoiding  dry  and 
crumbling  fragments.  Brewers"  yeast  must  first  be  well  stirred,  and  then 
weighed  out  in  a counterpoised  dish.  Break  up  the  pressed  yeast  carefully 
in  a small  evaporating  basin,  with  some  of  the  water  which  has  been  raised 
to  the  right  temperature  ; for  this  purpose  an  india-rubber  finger  stall 
placed  on  the  finger  is  useful.  Pour  the  yeast  and  water  into  the  bottle  ; 
rinse  the  basin  with  the  remainder  of  the  six  ounces  of  water.  As  rapidly 
as  possible  introduce  each  sample  of  yeast,  to  be  tested,  in  its  respective 
bottle  in  precisely  the  same  manner.  Having  introduced  the  yeast,  yeast 
mixture,  or  other  substance,  and  water,  into  the  respective  bottles,  gently 
shake  each  bottle  so  as  to  thoroughly  mix  the  ingredients  ; then  tightly 
cork  each  bottle,  and  arrange  the  apparatus  as  shown  in  Fig.  21,  given  at 
the  commencement  of  the  chapter.  Remove  the  glass  stopper  at  d,  and 
suck  out  the  air  from  the  apparatus  until  the  water  or  brine  rises  in  the  jar, 
/,  somewhat  above  the  zero,  then  again  insert  the  glass  stopper.  Pinch 
the  india-rubber  tubing  on  one  side  of  d so  as  to  make  a slight  opening, 
and  thus  permit  air  to  enter  ; in  this  way  lower  the  liquid  in  / until  its 
level  exactly  coincides  with  the  zero.  Perform  this  operation  as  rapidly 
as  possible  with  all  the  apparatus  being  used,  and  note  the  exact  time  in 
the  notebook.  As  the  fermentation  proceeds,  the  surface  of  the  liquid 
in  the  jars  will  become  lower,  and  in  this  way  a measure  of  the  amount  of 
gas  yielded  is  obtained.  At  the  end  of  every  half-hour  or  hour  from  the 
commencement,  read  off  the  volume  of  gas,  and  enter  the  same  in  the  note- 
book. When  the  jars  are  nearly  full  of  gas  watch  them  carefully,  and  as 
soon  as  the  100  cubic  inches,  or  500  c.c.,  mark  is  reached,  withdraw  the 
plug  at  d,  blow  into  the  jar  for  a few  seconds  so  as  to  displace  carbon  dioxide 
through  the  bottom,  and  then  suck  out  the  air  until  the  liquid  again  rises 
to  the  top  of  jar,  re-insert  the  plug,  and  rapidly  adjust  the  surface  of  the 
liquid  to  the  zero.  This  operation  should  last  only  a very  short  time, 
and  does  not  practically  affect  the  results  that  are  being  obtained.  The 
readings  may  be  taken  for  from,  say,  two  to  six  hours  ; or,  if  wished,  until 
the  action  ceases.  These  directions  apply  equally  to  the  ordinary  use  of 
the  apparatus  for  testing  the  strength  of  yeasts.  With  the  alternative 
displacement  apparatus,  the  earlier  part  of  the  procedure  is  the  same. 
The  difference  in  the  mode  of  collecting  and  measuring  the  evolved  gas 
has  been  already  sufficiently  explained. 

384.  Preparation  of  Yeast  Mixture. — It  is  essential  that  the  substances 
composing  this  mixture  be  thoroughly  mixed.  The  following  is  the  best 
mode  of  procedure.  First,  dry  tlie  substances  at  a gentle  heat  (100°  C.).  In 
the  laboratory  this  is  done  by  placing  them  in  a hot-water  oven  ; then 
finely  powder  each  in  a mortar,  and  weigh  out  the  right  quantities.  Then 
thorouglily  mix  the  first  four  ingredients  ; afterwards  add  the  fifth,  and 
again  mix  ; then  add  the  sugar  little  by  little,  mixing  between  each  addition. 
In  this  way  an  equal  composition  of  the  mixture  throughout  is  assured. 
Coarse  crystalline  coffee  sugar  is  almost  chemically  pure  ; failing  this, 
the  best  loaf  sugar  may  be  used. 

The  pepsin  necessary  for  the  experiments  may  be  obtained  from  the 
chemist. 

The  malt  wort  may  be  prepared  by  infusing  coarsely  ground  malt  with 
ten  times  its  weight  of  water  for  two  hours  at  65°  C.  : it  is  then  filtered 
and  diluted  down  with  w'ater  until  at  the  right  density. 

In  experiments  w ith  flour,  the  flour  and  part  of  the  water  should  first 


TECHNICAL  RESEARCHES  ON  FERMENTATION.  231 

be  placed  in  the  generating  bottle,  and  thoroughly  shaken  before  the 
addition  of  yeast. 

In  experiments  with  flour,  the  flour  and  part  of  the  water  should  first 
be  placed  in  the  generating  bottle,  and  thoroughly  shaken  before  the 
addition  of  yeast. 

The  starch  is  gelatinised  by  allowing  it  to  stand  in  a small  beaker,  with 
some  water,  for  about  five  minutes  in  the  hot  water-bath,  stirring  thoroughly 
meanwhile. 

The  experiments  on  flour  infusion,  in  which  the  sugar  is  determined 
before  and  after  the  fermentation,  are  very  important,  but  had  better  be 
postponed  until  the  student  has  proceeded  with  his  studies  of  analysis. 

In  the  temperature  experiments  the  tests  at  the  same  temperature 
should  be  made  on  the  same  day,  and  the  complete  series  with  as  little 
interval  as  possible  between. 

In  addition  to  the  experiments  described  in  this  chapter,  many  others 
will  suggest  themselves  to  the  practical  baker  : these  he  may  arrange  for 
himself,  and  use  the  yeast  apparatus  as  a means  of  measuring  the  evolution 
of  gas,  under  any  conditions  that  may  be  of  interest  to  him.  The  student 
will  do  well,  in  addition,  to  perform  the  following  series  of  tests. 

385.  Keeping  Properties  of  Different  Yeasts. — Procure  samples  as  fresh 
as  possible  of  different  pressed,  brewers’,  and  patent  yeasts.  Test  immedi- 
ately after  procuring  them  ; then  store  in  a cool  cellar,  and  test  each  sample 
on  successive  days  until  they  are  eapable  of  setting  up  little  or  no  fermenta- 
tion. To  ensure  perfect  accuracy  it  is  well  to  keep  each  sample  of  yeast 
in  a weighed  vessel  ; any  loss  by  evaporation  may  then  in  the  case  of  the 
liquid  yeasts  be  made  up  each  day  by  the  addition  of  distilled  water.  The 
pressed  yeast  may  be  kept  in  a stoppered  bottle,  or,  preferably,  the  portion 
for  each  estimation  should  be  taken  from  the  interior  of  the  mass  ; as  a 
check,  moisture  should  then  be  estimated  in  the  yeast  each  day. 

386.  Use  of  Testing  Apparatus  without  Temperature  Regulator. — In 

the  foregoing  descriptions  given  it  has  been  directed  that  the  yeast  bottle 
stand  in  a water-bath  regulated  by  an  automatic  temperature  regulator. 
While  such  an  arrangement  is  extremely  useful,  it  is  not  absolutely  necessary. 
For  actual  bakehouse  use  the  following  plan  answers  well.  Select  a place 
somewhere  near  the  oven  where  the  temperature  is  pretty  constant,  and, 
if  possible,  between  70°  and  80°  F.  Arrange  on  a shelf,  clamped  to  the 
wall,  a saucepan  sufficiently  large  to  take  the  yeast  bottles,  and  fix  the 
trough  for  the  graduated  jar  in  position.  The  saucepan  will  have  to  be 
raised  sufficiently  high  by  means  of  blocking  ; this  should  be  properly 
done  at  the  outset,  as  the  apparatus  should  remain  there  permanently. 
When  about  to  use  the  apparatus,  first  of  all  fill  the  saucepan  with  water 
at  the  desired  temperature  F.,  and  then  make  the  estimation.  A warm 
place  being  chosen,  the  water  in  the  saucepan  will  not  fall  very  much  in 
temperature  during  the  time  necessary  for  carrying  out  the  experiment. 
This  method  of  using  the  apparatus  applies  more  particularly  to  yeast 
testing  than  to  the  more  delicate  experiments  described  in  the  preceding 
pages. 


CHAPTER  XII. 
MANUFACTURE  OF  YEASTS. 


387.  For  baking  purposes  three  commercial  varieties  of  yeast  are  em- 
ployed, namely,  Brewers’,  Distillers’  Compressed,  and  “ Patent  ” yeasts. 
These  latter  may  again  be  subdivided  into  malt  and  hop  yeasts  as  used  in 
England,  and  the  Scotch  flour  barms.  The  superior  quality  of  the  dis- 
tillers’ compressed  yeast  has  led  to  its  now  being  used  to  the  almost  entire 
exclusion  of  the  other  kinds.  Still  there  are  districts  where  distillers’  yeast 
cannot  be  obtained,  and  therefore  bakers  still  have  to  manufacture  their 
o^vn  “ patent  ” yeast.  Descriptions  follow  of  how  these  different  types  of 
yeast  are  manufactured. 

Brewers’  Yeast. 

388.  In  the  chapter  on  Fermentation  an  account  is  given  of  the  appear- 
ance of  an  actively  fermenting  tun  of  brewers’  wort.  The  brewer  first  treats 
his  malt  with  water  at  a temperature  of  about  65°  C.  for  about  two  hours, 
more  or  less  ; during  that  time  the  starch  of  the  malt  is  converted  into 
dextrin  and  maltose.  The  liquor  is  then  allowed  to  drain  from  the  grains, 
or  husks  of  malt,  and  is  transferred  to  a copper  in  which  it  is  boiled  with 
hops  : the  hops  are  removed  and  the  wort  rapidly  cooled,  either- by  being 
exposed  to  the  air  in  shallow  open  coolers,  or  poured  over  a specially  arranged 
apparatus,  consisting  of  a series  of  pipes  through  which  cold  water  is  passing, 
and  which  is  termed  a refrigerator.  This  cooling  must  be  done  as  rapidly 
as  possible,  as  a temperature  of  about  30°  C.  is  particularly  suited  to  the 
rapid  growth  and  development  of  disease  ferments.  On  the  wort  being 
cooled  toTSor  19°  C.  (65°  F.),  about  one  one-hundred  and  fiftieth  part  of  its 
weight  of  yeast  from  a previous  brewing  is  added.  Fermentation  sets  in, 
and  after  a time  yeast  rises  to  the  surface,  and  is  skimmed  off.  The  flrst 
is  rejected  because  any  lactic  ferments  or  other  bacteria  that  may  be  present 
are,  from  their  small  size,  floated  up  to  the  surface  with  the  yeast  on  its 
flrst  ascent.  At  the  time  when  the  fermentation  is  most  active  and  vigorous, 
the  best  yeast  is  being  produced.  As  fermentation  slackens,  cells  are 
thrown  to  the  surface  which  have  been  grown  in  a comparatively  exhausted 
medium.  Such  yeast  is  weak,  and  possesses  less  vitality.  For  their  own 
pitching  purposes,  the  brewers  reserve  the  middle  yeast.  Bakers  who  use 
brewers’  yeast  should  be  supplied  with  that  equal  in  quality  to  what  the 
brewer  himself  uses  for  starting  fermentation.  The  yeast,  when  skimmed, 
should  be  stored  in  shallow  vats,  so  as  to  admit  of  free  access  of  atmospheric 
oxygen. 

In  some  breweries  the  beer  is  allowed  to  finish  its  fermentation  in  large 
casks,  arranged  so  that  the  bung-hole  is  very  slightly  on  one  side  : the 
yeasty  slowly  works  out  of  the  bung-hole  and  flows  in  a shallow  stream 
down  the  outside  of  the  cask  until  it  reaches  the  bottom,  when  it  drops  in 
a gutter  arranged  to  receive  it.  A number  of  these  casks  are  usually  arranged 
side  by  side,  and  connected  together  by  a pipe  at  the  bottom  ; they  are 
consequently  technically  termed  “ unions.”  The  one  gutter  receives  the 
yeast  from  the  series  of  unions  and  conveys  it  to  the  proper  receptacle. 

232 


MANUFACTURE  OF  YEASTS. 


233 


Tlie  yeast  from  these  unions  is  found  to  make  far  better  bread  than  that 
.skimmed  from  large  fermenting  tuns.  The  reason  is  that  the  yeast  gets 
thoroughly  aerated  during  its  flow  down  the  side  of  the  cask.  For  baking 
purposes,  the  thorough  aeration  of  yeast  is  essential. 

389.  Employment  of  Brewers’ Yeast. — Brewers'  yeast  is  used  in  the  pro- 
duction of  what  is  called  “ farmhouse  " bread  : it  is  supposed  to  produce 
a sweeter  flavoured  loaf  than  do  other  varieties.  On  the  other  hand,  brewers’ 
yeasts  darken  the  colour  of  bread.  For  reasons  explained  in  the  preceding 
chapter,  for  bakers’  purposes,  brewers’  yeast  is  weak,  and  if  used  alone  must 
be  employed  in  considerable  quantity.  Almost  invariably  a potato  ferment, 
or  some  substitute  therefore,  is  employed  together  with  brewers’  yeast.  It  is 
apt  when  freely  used  to  impart  a bitter  taste  to  the  bread  : this  may  be 
in  part  obviated  by  washing  the  yeast,  but  even  then  it  is  exceedingly 
difficult  to  remove  the  bitter  taste.  Particularly  in  summer  time  brewer’s 
yeast  is  found  to  be  very  unreliable  and  uncertain  in  its  actions.  Even 
those  bakers  who  prefer  brewers’  yeast,  when  they  can  procure  it  good, 
find  themselves  compelled  to  resort  to  compressed  yeast  during  the  hot 
summer  months. 

In  selecting  a brewers’  yeast  for  bakers’  purposes,  those  breweries  should 
be  avoided  where  large  quantities  of  sugar  or  other  malt  substitutes  are 
used  instead  of  malt  itself.  Such  brewing  mixtures  contain  a deficiency 
of  appropriate  nitrogenous  matters,  and,  although  the  resultant  beer  is 
sounder,  and  better  meets  the  present  requirements  of  the  public,  the 
yeast  produced  is,  from  the  bakers’  standpoint,  weak  and  impoverished 
through  ill  nourishment. 

390.  Microscopic  Examination  of  Yeast. — This  operation  requires  a 
fair  amount  of  experience  before  a trustworthy  judgment  can  be  formed. 
For  the  examination  of  yeast  under  the  microscope,  it  should  be  diluted 
with  water  until  so  weak  as  simply  to  give  a milky  appearance  to  the  water. 
A minute  drop  is  then  put  on  a slide,  over  which  a cover  is  gently  placed. 
In  microscopically  examining  yeast,  there  are  two  distinct  points  to  be 
observed  : first,  the  presence  or  absence  of  disease  ferments,  bacteria,  etc.  ; 
second,  the  appearance  of  the  yeast  cells  themselves.  For  satisfactory 
work,  a power  of  six  or  eight  hundred  diameters  is  necessary  : the  objective 
must  be  a good  one,  giving  not  only  magnification,  but  also  clear  and  accurate 
definition.  It  is  a good  plan  to  use  a microscope  in  which  several  objectives 
are  fastened  to  one  “ nose-piece,”  so  that  the  powers  may  be  changed 
instantaneously,  without  the  trouble  of  unscrewing  the  one  objective  and 
then  replacing  it  by  another.  Working  with  an  instrument  the  yeast 
may  first  be  examined  with  a magnification  of  about  440  diameters,  and 
then,  having  seen  the  aspect  of  a fairly  large  field,  a few  typical  ceUs  may 
be  observed  more  closely  with  a magnifying  power  of  about  1000  diameters. 

First,  with  regard  to  the  presence  or  absence  of  foreign  ferments.  The 
fewer  of  these  the  better  the  yeast.  A yeast  for  bakers’  purposes  needs 
to  be  judged  by  a somewhat  different  standard  to  that  adopted  by  the 
brewer.  To  the  latter,  the  presence  of  lactic  or  but3rric  ferments  or  other 
disease  organisms  means  that,  during  the  period  the  beer  is  stored  before 
it  is  all  consumed,  there  is  ample  time  for  changes  to  go  on  which  will  result 
in  either  a marked  deterioration  or  spoiling  of  the  beer.  But  if  this  change 
does  not  make  itseK  rperceptible  until,  say  two  or  three  weeks  have  elapsed, 
it  follows,  as  bread  is  fermented,  baked  and  eaten  within  about  three  days, 
that  under  ordinary  circumstances  such  changes  cannot  take  place  in  bread. 
This  explanation  is  necessary,  because  it  is  well  known  as  a matter  of  fact 
that  many  bakers  do  succeed  in  producing  very  good  bread,  who  use  a 
yeast  in  which  there  is  frequently  an  abundance  of  foreign  organisms.  It 


234 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


will  in  such  cases,  however,  be  found  that  they  take  special  precautions 
which  serve  to  prevent  an  injurious  action  of  these  during  fermentation. 
Summing  up,  yeasts  may  be  used  by  bakers  which  could  not  possibly  be 
employed  by  the  brewer,  because  the  fermenting  process  of  the  former  is 
so  much  shorter  ; nevertheless  an  excess  of  disease  ferments  may  set  up 
injurious  action  even  during  the  time  of  panary  fermentation  unless  special 
precautions  are  taken.  It  is  consequently  safely  laid  down  that  the  fewer 
of  these  foreign  organisms  the  better.  The  presence  or  absence  of  disease 
ferments  affords  a valuable  indication  as  to  the  previous  history  of  the 
yeast,  apart  from  their  own  specific  action  on  the  dough.  A yeast  largely 
contaminated  with  foreign  organisms  has  been  badly  made  : unsound  malt 
will  very  likely  have  been  used  for  its  manufacture,  and  the  whole  process 
of  fermentation  conducted  in  dirty  vessels.  As  in  a brewer’s  yeast  the 
presence  of  disease  ferments  tells  us  this  of  its  previous  history,  the  yeast 
should  be  condemned,  because,  when  carelessly  produced  under  such 
unfavourable  conditions,  the  yeast  itself  is  likely  to  be  unsound,  or  at  least 
very  uncertain  in  its  quality. 

Secondly,  with  reference  to  the  yeast  cells  themselves,  the  actual  shape 
of  the  cells  will  vary  with  its  origin.  Ordinary  English  brewers’  yeast 
consists  of  round  cells,  but  Burton  yeast  is  oval  ; so  also  is  that  in  other 
districts  where  very  hard  water  is  used.  With  any  yeast  the  cells  should 
be  about  equal  in  size  ; not  irregular,  with  some  very  large  and  others 
small.  The  cells  should  be  isolated,  or  at  most  only  attached  in  pairs  ; 
where  they  occur  in  large  colonies,  the  yeast  is  too  young,  and  has  not 
had  time  to  thoroughly  mature.  The  cells  should  appear  plump  and  not 
shrunken.  The  cell-walls  should  be  of  moderate  thickness  : if  very  thin 
the  yeast  is  too  young,  and  has  not  attained  maturity  ; on  the  other  hand, 
very  thick  integuments  denote  an  old,  worked  out  yeast.  Thin  cells-walls 
may  also  be  due  not  only  to  very  young  yeast,  but  also  to  the  yeast  being 
over  kept  long  enough  for  the  breaking  down  of  the  walls  to  have  com- 
menced : under  these  circumstances  the  protoplasm  of  the  interior  of  the 
cells  is  seen  to  be  broken  down  and  frequently  exhibits  a “ Brownian  ” 
movement.  If  in  this  condition,  the  yeast  is  far  gone,  and  will  be  found 
weak  and  exhausted  for  bread-making.  As  in  this  operation  yeast  does 
not  bud  or  reproduce,  but  does  its  work  in  virtue  of  the  energy  and  vitality 
of  the  original  cells  introduced,  it  is  in  the  highest  degree  important  that 
these  cells  should  be  strong,  healthy,  and,  as  far  as  is  possible,  in  full  maturity ; 
when  in  this  condition,  the  contents  of  the  cells  should  show  slight  granula- 
tions. Each  cell  should  have  one,  or  at  most  two,  vacuoles  ; but  when 
placed  in  a drop  of  clear  beer  wort  on  the  slide,  the  fluid  should  rapidly 
penetrate  the  cell-walls,  causing  the  contents  to  become  lighter,  and  the 
vacuoles  to  disappear.  These  changes  occur  but  slowly  in  old  cells  that 
have  been  worked  for  a long  time. 

In  Plate  II.,  Chapter  IX.,  illustrations  have  already  been  given  of 
different  varieties  of  yeast  employed  by  the  baker.  The  drawings  of  brewers’ 
yeast  for  this  plate  were  made  in  the  summer,  and  represent  samples  of 
brewers’  yeast  during  practically  the  hottest  weather  of  the  year.  The 
specimens  marked  a and  h were  taken  from  two  London  samples  of  yeast,  | 
as  sold  to  London  bakers  by  yeast  merchants.  A considerable  number  | 
of  disease  ferments  are  present  in  both,  marking  them  as  being  in  an  unhealthy  ; 
condition.  It  is  to  be  feared  that  often  sufficient  care  is  not  taken  for  the  I 
storage  and  preservation  of  yeast,  especially  during  the  hot  weather,  by  j 
those  who  collect  brewers’  yeast  for  redistribution  among  bakers.  For  ; 
purposes  of  comparison,  some  yeast  was  obtained  from  a Brighton  brewery  : 
this  is  figured  in  section  c.  It  was  found  to  be  far  away  purer  than  either  i 
of  the  London  samples  ; one  or  two  bacteria  are  shown  in  the  sketch,  but  ! 


MANUFACTURE  OF  YEASTS. 


235 


there  were  several  microscopic  fields  that  contained  no  foreign  ferments 
whatever.  In  general  aspect,  the  cells  of  yeast  c were  firmer  in  outline, 
the  walls  being  thicker  while  the  interior  matter  showed  more  distinct  and 
darker  granulations.  It  should  be  added  that  in  these  drawings  the 
estimated  magnification  is  only  approximate.  In  every  case  w^here  it  is 
wished  to  ascertain  exact  dimensions,  the  eye-piece  micrometer  should  be 
called  into  requisition. 

Manufacture  of  Compressed  Yeasts. 

391.  These  yeasts  are  now^  so  w idely  and  successfully  used  that  an  account 
of  their  origin  and  mode  of  manufacture  claims  a place  in  this  work.  They 
find  their  way  into  this  country  from  Holland  and  France,  and  are  also 
largely  manufactured  in  the  United  Kingdom.  They  are  not,  as  has  been 
stated,  low  or  bottom  yeasts  of  lager  beer  fermentation,  but  are  distillers’ 
yeasts,  and  are  formed  as  the  principal  product  in  the  manufacture  of 
spirits  from  malt  and  raw  grain  ; the  spirits  being  used  in  the  manufacture 
and  treatment  of  liqueurs,  perfumes,  wine,  and  brandy.  This  manufacture 
can  only  be  successfully  conducted  on  a very  large  scale,  and  cannot  be 
imitated  by  the  baker  who  simply  wishes  to  make  yeast  for  his  own  con- 
sumption. 

Being  desirous  of  giving  as  accurate  an  account  as  possible  of  the  most 
advanced  and  scientific  methods  of  manufacturing  compressed  distillers’ 
yeast  for  bakers’  purposes,  the  authors  put  themselves  in  communication 
with  the  directors  of  the  Netherlands  Yeast  and  Spirit  Manufactory  of 
Delft,  Holland.  In  response  they  received  an  invitation  to  visit  the  factory 
and  personally  inspect  the  processes  of  manufacture.  The  following  de- 
scription is  compiled  from  information  thus  gained,  supplemented  by  data 
furnished  for  the  purpose  by  the  directors  of  the  factory. 

The  operations  of  yeast  manufacture  resolve  themselves  into  four  groups 
w’hich  may  be  classified  under  the  following  heads  : — 

1.  Treatment  of  the  raw  grain,  including  the  malting  of  barley. 

2.  Mashing  and  preparation  of  the  wort. 

3.  Fermentation. 

4.  Collection  and  packing  of  the  yeast. 

(1)  Treatment  of  the  raw  grain.  The  grain  required  is  brought  by  barge 
and  directly  discharged  by  elevators  into  granaries  provided  for  that  pur- 
pose. For  yeast  and  spirit  manufacture,  there  must  be  a sufficiency  of 
appropriate  protein  matter,  and  also  of  carbohydrates.  Brewing  sugars 
are  inadmissible,  because  by  unduly  reducing  the  proportion  of  protein 
matter,  they  w^ould  cause  the  production  of  an  unhealthy  and  weak  yeast. 
The  cereals  most  commonly  used  are  barley,  rye,  and  maize.  Rice  is  not 
well  fitted  for  yeast  production,  because  of  its  comparatively  non-nitrogenous 
character.  The  grain  on  arrival  is  first  subjected  to  such  cleaning  opera- 
tions as  may  be  necessary,  including  gravity  separations  of  lighter  and 
heavier  foreign  matter,  and  then  a thorough  washing.  The  cleaned  grain 
is  next  conveyed  to  the  mill,  where  the  rye  and  maize  are  reduced  to  a 
moderately  fine  meal  by  roller  mills.  The  barley  is  first  converted  into 
malt.  In  order  to  effect  this  object,  two  separate  systems  are  in  use. 

Ordinary  Malting  System.  On  this,  known  also  as  the  old  system,  the 
barley  is  first  soaked  in  water  of  a suitable  temperature  in  large  tanks. 
When  sufficiently  moistened,  which  operation  may  take  from  fifty  to  sixty 
hours,  the  grain  is  transferred  to  the  malting  floors  and  there  allowed  to 
germinate  or  sprout.  As  previously  explained,  this  treatment  destroys 
the  parenchymatous  cell-walls,  and  thus  renders  the  interior  of  the  grain 
more  readily  amenable  to  diastatic  action.  At  the  same  time  diastase 
itself  is  developed,  and  the  nitrogenous  matter  rendered  more  soluble. 


236 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


When  germination  has  proceeded  sufficiently  far,  the  malt  is  dried  in  kilns. 
The  malt  kilns  are  conical  buildings  in  which  the  grain  is  laid  on  perforated 
plates.  At  the  base  the  source  of  heat  is  fixed  and  consists  of  a species  of 
grate  in  which  the  fuel  is  consumed.  By  means  of  a fan  placed  at  the 
top  of  the  kiln,  a current  of  air  is  continually  drawn  through  the  grain, 
which  is  thus  effectually  dried. 

Pneumatic  Mailings.  On  this  system  the  malt  floors  are  replaced  by 
revolving  drums,  which  are  charged  with  barley.  Air  saturated  with  water 
is  led  into  the  drums  and  thus  moistens  the  grain.  Germination  proceeds 
under  efficient  control,  and  when  it  has  proceeded  sufficiently  far,  the 
malt  is  conveyed  to  kiln-drums  and  there  dried  by  means  of  heated  air. 

Whether  prepared  by  the  old  or  floor-system,  or  pneumatically,  the 
finished  malt  is  ground  to  meal. 

(2)  Mashing  and  'preparation  of  the  Wort.  The  meal  of  the  raw  grains, 
maize  and  rye,  is  treated  by  boiling  with  water  in  large  boilers  by  the  action 
of  high  pressure  steam.  When  thoroughly  cooked  the  mixture  of  grain 
and  water  is  cooled  and  passed  into  the  saccharification  tuns,  where  the 
malt  is  added.  Mashing  then  proceeds  until  the  hydrolysis  of  the  whole 
of  the  carbohydrates  to  maltose  is  as  complete  as  possible.  While  the 
brewer  finds  it  advantageous  to  retain  dextrin  and  some  amount  of  malto- 
dextrins  in  his  wort,  the  distiller  has  practically  no  use  for  anything  except 
the  maltose,  and  so  pushes  the  enzymic  action  to  its  utmost  limit.  At 
the  close  of  the  mashing  the  wort  requires  to  be  reduced  to  the  fermenting 
temperature.  It  is  important  that  this  be  effected  as  rapidly  as  possible, 
as  the  intermediate  cooling  stage  is  one  at  which  the  wort  is  most  sus- 
ceptible to  disease  fermentation.  For  this  purpose,  refrigerators  are  em- 
ployed, of  which  there  are  several  patterns.  One  of  the  most  convenient 
is  that  originally  devised  by  Lawrence,  in  which  a copper  pipe  is  bent  again 
and  again  on  itseK  so  as  to  form  a vertical  rack,  with  connected  horizontal 
pipes  in  a series  one  over  the  other.  Cold  water  passes  through  the  pipe, 
and  the  wort  is  allowed  to  flow  over  the  outer  surface,  thus  being  rapidly 
cooled  and  at  the  same  time  aerated.  The  cooled  wort  is  then  conveyed 
to  the  fermentation  vats,  where  it  awaits  the  next  stage  in  the  process  of 
manufacture. 

(3)  Fermentation.  Of  late  years,  the  necessity  of  starting  fermentation 
with  a pure  yeast  culture  has  been  more  and  more  fully  recognised.  As 
explained  in  a previous  chapter,  paragraph  330,  certain  races  of  yeast  are 
specially  adapted  for  dough  fermentation.  For  the  preparation  of  these 
a specially  equipped  chemical  and  biological  laboratory  is  provided.  By 
appropriate  methods,  such  yeasts  are  cultivated  from  a single  cell  until  an 
appreciable  quantity  is  obtained.  In  larger  apparatus  constructed  on 
the  principle  of  the  Pasteur  flask,  a more  abundant  growth  of  the  pure 
yeast  is  obtained,  and  this  is  used  in  starting  the  fermentation  of  the  wort. 
The  finished  yeast  is  similarly  controlled  by  tests  as  to  purity  and  strength 
made  in  the  laboratory  ; and  as  occasion  arises,  the  pitching  yeasts  are 
reinforced  by  addition  or  substitution  of  new  pure  culture  yeast.  The 
firm  employs  two  distinct  methods  of  fermentation,  known  respectively 
as  the  “ Vienna  and  the  “ Aerating  systems. 

Vienna  System.  The  first  step  in  this  system  is  the  preparation  of  what, 
in  the  bakers’  phraseology,  may  be  termed  a “ ferment,”  that  is,  a pre- 
liminary fermentation  of  a relatively  small  proportion  of  the  grain.  Malt 
and  rye  are  taken  together  for  this  purpose,  and  mashed  at  a convenient 
temperature,  so  as  to  obtain  as  complete  a transformation  as  possible  of 
the  starch  into  maltose.  The  mash  thus  produced  is  alloAved  to  stand  in 
the  tubs  at  a temperature  most  suitable  for  the  production  of  lactic  acid, 
that  is  about  35°  C.  The  lactic  acid  germs  on  the  skin  of  the  malt  rapidly 


MANUFACTURE  OF  YEASTS. 


237 


develop,  and  a marked  acidulation  ensues.  This  is  a most  interesting 
step  in  the  fermentation,  and  while  the  immediate  result  is  the  production 
of  lactic  acid,  yet  its  ultimate  effect  is  the  prevention  of  development  of 
the  lactic  acid  ferment.  This  organism  is  peculiarly  sensitive  to  the  effect 
of  its  own  product,  and  as  little  as  0*15  per  cent,  of  lactic  acid  added  to  a 
mash  is  sufficient  to  prevent  lactic  fermentation  taking  place,  although, 
on  the  contrary,  if  lactic  fermentation  be  once  started,  it  will  proceed  until 
something  like  1 *5  per  cent,  of  lactic  acid  has  been  formed.  The  reason 
of  this  inhibitory  effect  is  that  the  addition  of  lactic  acid  is  a deterrent 
not  only  to  lactic  fermentation,  but  also  to  the  multiplication  of  lactic 
acid  hacteria,  so  that,  by  its  addition  in  the  earlier  stage,  any  reproduction 
of  these  organisms,  and  consequently  any  but  the  smallest  possible  produc- 
tion of  lactic  acid,  is  prevented.  This  first  development  of  lactic  acid, 
then,  in  what  may  be  for  convenience  called  the  “ ferment,''  serves  to 
check  undue  development  of  acidity  in  the  main  fermentation.  It  also 
further  serves  the  useful  purpose  of  peptonising  and  otherwise  breaking 
down  the  nitrogenous  matter  of  the  grains  in  the  mash,  so  as  to  render 
them  available  as  yeast  foods. 

The  unfiltered  wort,  containing  the  “ grains  " or  husks  of  the  malt 
and  the  raw  grains,  is  treated  at  the  desired  temperature  with  pitching 
yeast  in  the  form  of  the  ferment  already  described.  Air  is  driven  through 
the  wort  by  mechanical  means  in  order  to  secure  thorough  aeration,  and 
this  operation  is  repeated  from  time  to  time  as  fermentation  proceeds,  as 
found  necessary.  The  grains  contained  in  the  mash  rise  to  the  surface 
and  there  act  as  a non-conductor  of  heat.  In  from  three  to  four  hours 
after  pitching,  the  carbon  dioxide  forces  itseK  up  in  a sort  of  cauliflower 
head  through  the  grains  and  “ breaks."  The  grains  are  removed  by  a 
skimming  operation,  and  fermentation  is  allowed  to  continue  for  from 
ten  till  twelve  hours  from  the  commencement,  and  then  the  process  of 
skimming  off  the  yeast  is  commenced.  The  skimming  is  effected  by  means 
of  a long  arm  which  sweeps  right  round  the  vat  and  collects  the  yeast  from 
the  top  into  an  inverted  cone,  which  from  its  shape  is  called  a parachute. 
The  alcohol  from  the  fermentation  remains  in  the  wort,  which  liquid  is 
distilled,  and  the  alcohol  thus  obtained  in  a concentrated  form.  The 
residual  liquid,  together  with  insoluble  matter  consisting  principally  of 
fibre  from  the  grains,  is  prepared  for,  and  used  as,  cattle-food.  The  fol- 
lowing figure.  No.  23,  shows  diagrammatically  the  “ Vienna  " method  of 
yeast  manufacture. 

Barge 

Jlo 

Rye,  Maize  Barley 

Maltings 


■Mill- 


Wort 


Fermentation 

I 


Yeast,  Spirit  Wash  Carbon 

cleansed,  by  (cattle-  dioxide 

washed,  distillation.  food).  in  air. 

pressed. 

Fig.  23. — Vienna  System  of  Yeast  Making. 


238 


THE  TECHNOLOGY  OF  BHEAD-MAKING. 


Aerating  System.  By  this  method,  the  wort  is  filtered  from  the  grains 
before  fermentation.  The  pitching  or  starting  yeast  is  added  to  the  clear 
wort,  through  which  a strong  current  of  air  is  forced.  The  yeast  as  pro- 
duced does  not  rise  to  the  surface  of  the  fermenting  wort,  but  sinks  and 
forms  a deposit  on*  the  bottom  of  the  vats  or  tuns.  At  the  close  of  the 
fermentation,  the  supernatant  clear  liquid  contains  the  alcohol,  and  is 
removed  for  purposes  of  distillation.  The  residual  liquid,  together  with 
the  filtered  grains,  is  prepared  for  use  as  cattle-food.  The  course  of  the 
various  operations  of  the  ‘‘  aerated  system  is  shown  diagrammatically 
in  Fig.  24. 

Wort 

I 

Filtration 


Residue  Fermentation  of  filtered 

wort  with  supply  of  air 


Deposit  Clear  liquid  from  Carbon 

of  which  through  dioxide 

yeast.  distillation  in  air. 

\ 


Alcohol.  Clear  liquid 

wash 

Wash  (cattle-food). ^ 

Fig.  24. — Aerated  System  of  Yeast-Making. 

(4)  Collection  of  the  Yeast.  The  yeast,  whether  skimmed  on  the  old 
system  or  deposited  on  the  new,  has  to  be  cleansed.  For  this  purpose 
it  is  mixed  with  water  and  passed  through  a series  of  sieves  (20  holes  to  the 
square  millimetre).  The  sieves  retain  any  grains  and  allow  the  yeast  to 
pass  through.  The  yeast  is  then  washed  by  decantation,  and  allowed  to 
settle.  Any  minute  particles  which  have  passed  through  with  the  yeast, 
being  lighter  than  w^ater,  rise  to  the  surface  and  are  thus  separated.  The 
deposited  yeast,  still  containing  much  water,  is  passed  through  centrifugal 
machines  by  which  much  of  the  water  is  removed.  The  thick  yeasty  liquid 
is  next  pumped  into  filtering  presses  and  thus  obtained  in  the  familiar 
dry  state.  The  yeast  is  now  ready  to  be  packed,  and  for  the  British  market 
is  filled  into  jute  bags,  which  are  mechanically  pressed  into  block  shape 
and  finally  branded  with  the  name  and  description  of  the  manufacturers. 
As  thus  prepared  “ N.G.  and  S.F.''  yeast  consists  of  pure  yeast  cells  of  a 
specially  selected  type.  It  is  practically  free  from  foreign  or  “ wild  ” 
yeast  and  also  from  bacteria. 

The  secrets  of  successful  yeast  manufacture  are  raw  materials  of  the 
highest  quality,  absolute  cleanliness  during  the  whole  process  of  manu- 
facture, and  finally  eternal  vigilance.  This  last  is  the  invariable  price 
of  excellence  in  yeast.  Cleanliness  of  vessels  is  ensured  by  washing  and 
scalding  with  live  steam.  As  an  additional  precaution,  all  vats  and  tuns 
are  periodically  treated  either  with  sulphurous  acid  or  bisulphite  of  lime, 
both  of  which  are  absolutely  harmless  and  most  efficient  antiseptics.  All 
floors  are  kept  clean  by  continual  rinsings  with  water,  the  pathways  con- 
sisting of  raised  planks,  under  which  the  Avater  passes  freely.  In  the  yeast- 
cleansing rooms,  Avhere,  being  in  the  quiescent  stage,  the  risk  of  contamina- 
tion is  greatest,  the  floors  and  walls  are  continually  treated  with  solution 
of  chloride  of  lime,  thus  most  effectively  destroying  all  disease  germs. 
8uch  is  in  outline  the  process  of  manufacture  employed  in  the  production 


MANUFACTURE  OF  YEASTS.  239 

of  one  of  the  most  widely  used  and  highest  character  yeasts  imported  from 
the  continent  into  the  United  Kingdom. 

392.  Characteristics  of  Compressed  Yeasts. — ^A  good  sample  of  com- 
pressed yeast  has  the  following  characteristics — it  should  be  only  very 
slightly  moist,  not  sloppy  to  the  touch  ; the  colour  should  be  a creamy 
white  ; when  broken  it  should  show  a fine  fracture  ; when  placed  on  the 
tongue  it  should  melt  readily  in  the  mouth  ; it  should  have  an  odour  of 
apples,  not  like  that  of  cheese  ; neither  should  it  have  an  acid  odour  or 
taste.  Any  cheesy  odour  shows  that  the  yeast  is  stale,  and  that  incipient 
decomposition  has  set  in. 

Viewed  under  the  microscope,  compressed  yeast  consists  of  somewhat 
smaller  and  more  oval  cells  than  those  of  brewers’  yeast.  In  the  best 
varieties  are  found  no,  or  only  traces  of,  foreign  ferments  ; other  brands 
contain  them  in  large  numbers.  The  yeast  cells  themselves  should  possess 
the  same  characteristics  as  have  already  been  described  w^hile  treating 
brew'ers’  yeast.  A drawing  of  compressed  yeast  is  given  in  Plate  II.  The 
cells  were  found,  on  measurement,  to  have  the  following  dimensions — 
Longer  diameter  . . . . 10  mkms.  = 0*0004  inch. 

Shorter  diameter  ..  ..  7*6  mkms.  = 0*0003  ,, 

Diameter  of  round  cells  . . . . 7*6  mkms.  = 0*0003  ,, 

The  sample  in  question  was  remarkably  free  from  disease  ferments, 
one  only  being  seen  in  the  field  sketched,  while  several  fields  showed  no 
foreign  organisms  whatever.  The  granulations  show  very  distinctly. 
The  yeast  in  question  was  a very  pure  one,  and  yielded  exceedingly  good 
results  when  subjected  to  strength  tests. 

In  general  character,  the  compressed  yeasts  are  steady  and  trustw^orthy 
in  their  action  ; they  produce  sw^eet,  well-flavoured  breads,  to  wdiich, 
w4ien  in  good  condition,  they  do  not  impart  any  yeasty  taste.  Their  good 
qualities  stand  out  most  distinctly  in  summer  time,  w'hen  other  yeasts 
so  frequently  fail  entirely  to  produce  a satisfactory  loaf  of  bread.  Their 
being  produced  in  such  large  quantity  causes  their  manufacture  to  be 
entrusted  to  men  who  bring  the  highest  skill  that  practical  experience 
and  science  can  furnish  to  bear  on  every  detail  of  manufacturing  processes. 
The  many  good  properties  of  distillers’  compressed  yeast  have  led  to  its 
almost  universal  employment  where  obtainable,  in  place  of  other  kinds  of 
yeast. 

393.  Admixture  of  Starch  with  Yeast. — It  is  a matter  of  history  that 
in  the  earlier  production  of  compressed  yeast  for  commercial  purposes 
starch  w^as  invariably  used.  This  is  simply  following  a common  practice, 
for  frequently  in  pharmaceutical  and  other  preparations  starch  is  employed 
as  a drying  agent  : for  this  purpose  it  is  w^ell  adapted,  being  neutral  in  its 
qualities,  inert  and  absolutely  harmless.  Yeast,  containing  bacteria,  has  a 
peculiar  slimy  nature  and,  therefore,  cannot  be  pressed  w^ell  ; henee  the 
addition  of  starch  permits  not  only  the  more  rapid,  but  also  the  more  com- 
plete removal  of  water.  With  improvements  in  yeast  manufaeture,  the 
difficulty  of  pressing  has  been  diminished,  as  purer  yeasts  are  “ cleaner  ” 
in  the  sense  of  freedom  from  external  sliminess,  and  so  filter  more  readily. 
With  these  improvements  the  previous  difficulties  have  almost  entirely 
disappeared,  and  the  addition  of  starch  can  no  longer  be  regarded  as  a 
neeessity  in  the  manufaeture  of  compressed  yeast.  Although  many,  if 
not  most,  yeasts  are  now  offered  to  buyers  as  consisting  of  pure  yeast  cells 
only,  samples  containing  starch  are  still  on  the  market.  For  this  there 
are  probably  several  reasons.  It  has  been  stated  that  eommercial  yeast 
contains  quantities  of  stareh  varying  from  5 to  as  much  as  75  per  cent.  ; 
if  this  be  so,  evidently  the  wdiole  of  the  larger  amount  is  not  added  for  the 


240 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


purpose  of  effecting  more  rapid  filtration,  but  is  an  adulterant  pure  and 
simple.  So  far  as  smaller  quantities  are  concerned,  the  authors’  opinion 
is  that  one  and  the  same  yeast,  if  mixed  with  a small  quantity  of  starch,, 
has  superior  keeping  powers  to  those  it  possessed  when  free  from  this  ad- 
mixture, especially  during  hot  weather.  This  conclusion  is  based  on  the- 
observation  of  samples  of  such  yeast  in  the  laboratory,  and  also  on  the 
testimony  of  bakers  in  provincial  districts  whose  yeast  is  comparatively 
old  when  it  reaches  them,  and  then  has  to  be  kept  some  days.  The  presence 
of  starch  diminishes  the  moisture  present,  and  this,  no  doubt,  is  the  reason 
of  its  better  keeping  qualities.  On  the  other  hand  it  may  be  argued  that 
modern  high-class  unmixed  yeasts  possess  sufficiently  good  keeping  qualities- 
to  satisfy  any  ordinary  requirements  of  commercial  use. 

Briant  states  that  “ordinary  pressed  yeast  contains  from  70  to  75  per 
cent,  of  moisture,  and  that  if  starch  be  introduced,  the  proportion  present 
is  considerably  smaller,  and,  within  certain  limits,  it  can  be  shown  that 
the  starch  only  replaces  a proportion  of  the  moisture,  and  reduces  that  in 
the  yeast  itself,  so  that  it  is  possible  that  the  percentage  of  yeast  may  be 
even  greater  instead  of  smaller.  The  starch  abstracts  moisture  from  tho 
yeast  cells  themselves,  so  that  it  is  possible  that  the  addition  of  starch 
may  increase  the  proportion  of  actual  yeast  in  the  ssmple,  as  shown  by 
the  following  figures  : — 


Sample. 

Yeast. 

starch. 

Moisture,  Ash,  etc. 

No.  I 

24-60  per  cent. 

None  per  cent. 

75-40  per  cent. 

„ 2 

. . 25-10 

None  ,, 

74-90 

„ 3 

. . 26-15 

5-70 

68-15 

,,  4 

. . 24-08 

12-15  „ 

63-77 

„ 5 

. . 20-50 

17-20  „ 

62-30 

It  will  be  seen  that  the  yeasts  containing  starch  are  decidedly  drier. 
In  No.  3 sample  it  will  be  further  seen  that  the  percentage  of  starch  intro- 
duced has  actually  increased  the  quantity  of  real  yeast  present,  so  that 
the  purchaser,  although  buying  a proportion  of  starch  for  yeast,  would 
nevertheless  obtain  more  yeast  than  he  would  have,  had  the  sample  been 
perfectly  pure.  . . . There  is  one  direction  in  which  the  use  of  starch 
is  really  commendable,  namely,  by  the  reduction  it  effects  in  the  percentage 
of  moisture  in  the  sample,  and  the  consequent  increased  keeping  quality 
imparted  thereto.  . . . The  drier  the  yeast,  the  better  it  will  keep,  and 
it  is  in  this  sense  that  the  use  of  starch  in  yeast  may  be  of  service  to  the 
baker.” 

The  following  determinations  were  made  by  one  of  the  authors  on  two 
samples  of  the  same  manufacturer’s  yeast,  unmixed  and  mixed. 

Unmixed.  Mixed. 

Starch 0*00  per  cent.  19-20  per  cent. 

Water 72-88  „ 60-40 

The  unmixed  yeast  therefore  contained  12-48  per  cent,  more  water 
tlian  the  mixed  sample,  which  latter  contained  19-20  per  cent,  of  starch 
Of  this  starch,  therefore,  12-48  per  cent,  simply  replaced  water,  leaving  a 
surplus  of  6-72  per  cent,  of  starch,  which  had  gone  to  increase  the  weight. 
A test  was  made  of  the  gas-evolving  power  of  the  two  yeasts,  with  the 
result  that  the  unmixed  sample  yielded  440,  and  the  mixed  sample  443 
volumes  of  gas  in  four  hours. 

Granted  that  small  amounts  of  starch  act  beneficially,  this  is  no  justifica- 
tion of  the  addition  of  inordinately  large  quantities.  In  suggesting  a 
limit,  beyond  which  the  presence  of  starch  should  be  considered  by  the 
baker  in  the  light  of  an  adulterant,  the  maximum  of  20  per  cent,  is  suggested, 
wliich  amount  will  usually,  so  far  as  the  authors’  experience  goes,  coincide 


MANUFACTURE  OF  YEASTS. 


241 


with  an  actual  increase  of  weight  of  the  mixed  yeast  by  about  8 per  cent, 
over  the  weight  of  the  same  yeast  if  supplied  pure.  It  goes  without  saying 
that  the  sale  of  a mixed  yeast,  as  unmixed,  constitutes  a fraud  on  the  pur- 
chaser. There  is  no  reason  in  fact  why  the  addition  should  not  be  declared, 
with  an  explanation  that  it  serves  to  improve  the  keeping  qualities  of  the 
yeast. 

In  the  case  of  James  v.  Jones,  1894,  l.Q.  B.  304,  it  was  held  that  baking 
powder  was  not  an  article  of  food  within  the  meaning  of  the  Sale  of  Food 
and  Drugs  Act,  1875,  and  following  this  decision  magistrates  have  held 
that  it  followed  that  as  yeast  belongs  to  the  same  category  as  baking  powder, 
it  is  also  excluded  from  the  legal  definition  of  food.  No  doubt  as  a result 
of  this  decision,  the  definition  of  food  is  extended  as  follows  in  section  26 
of  the  Sale  of  Food  and  Drugs  Act,  1899  : — 

“ For  the  purposes  of  the  Sale  of  Food  and  Drugs  Acts  the  expression 
“ food  ""  shall  include  every  article  used  for  food  or  drink  by  man^  other 
than  drugs  or  water,  and  any  article  which  ordinarily  enters  into  or  is 
used  in  the  composition  or  [preparation  of  human  food  ; and  shall  also 
include  flavouring  matters  and  condiments."' 

Yeast  and  baking  powder  are  now  therefore  both  clearly  articles  of 
food  within  the  meaning  of  Food  and  Drugs  Acts. 

“Patent,”  or  Bakers’  Home-Made  Yeasts. 

394.  As  already  explained,  these  are  now  largely  replaced  by  com- 
pressed yeast.  But  there  are  still  districts  where  this  is  unobtainable, 
and  where  bakers  must  perforce  prepare  their  own  yeast.  It  is  hoped 
that  these  will  find  the  following  paragraphs  of  service.  Bakers’  home-made 
yeasts  may  be  divided  into  two  varieties — malt  and  hop  yeasts  as  used 
in  England,  and  flour  barms  as  employed  in  Scotland. 

395.  Bakers’  Malt  and  Hop  Yeasts. — ^These  consist  essentially  of  small 
mashes  of  malt  and  hops,  fermented  either  by  the  addition  of  some  yeast 
from  a previous  brewing,  or  allowed  to  ferment  spontaneously  : the  latter 
is  known  as  “ virgin  ” yeast.  The  hops  present  tend  to  prevent  disease 
fermentations,  as  their  bitter  principle  is  inimical  to  bacterial  growth  and 
development.  In  virgin  yeasts,  particularly,  it  is  necessary  to  use  hops 
largely,  and  also  plenty  of  malt  ; as  lactic  and  other  foreign  ferments 
flourish  far  better  in  a dilute  saccharine  medium  than  in  a stronger  one. 
The  reader  will  already  be  familiar  with  the  general  outlines  of  the  fermenta- 
tion of  a hopped  wort  : as  an  introductory  to  directions  for  the  preparation 
of  patent  yeast  a careful  study  of  the  following  experiment,  made  by  one 
of  the  authors,  will  be  of  service.  The  student  will  do  well  to  repeat  the 
experiment  for  himself  : sufficiently  full  directions  are  therefore  given  to 
enable  him  to  do  so. 

Take  two  quarts  of  water  and  half  an  ounce  of  good  hops  ; set  these  to 
i boil  in  a large  glass  flask  or  other  clean  vessel  ; boil  for  half  an  hour,  and 
I then  cool  down  to  65°  C.  (149°  F.).  Scald  out  a large  glass  beaker,  or 
» failmg  this,  a vessel  of  copper  or  enamelled  ware  ; wood  will  not  answer 
I well.  Weigh  out  12  ounces  of  ground  malt  and  mix  with  the  hops  and 
i water  in  the  beaker.  Maintain  the  whole  at  a temperature  of  from  65° 
to  70°  C.  (149°  to  158°  F.)  for  two  hours  ; this  may  be  done  by  standing 
the  beaker  in  a hot  water-bath.  By  the  end  of  this  time  the  saccharification 
; of  the  malt  should  be  complete.  Have  ready  another  glass  vessel  perfectly 
p clean  and  scalded.  Strain  the  wort,  from  the  grains,  through  calico  into 
p this  second  clean  vessel  ; cool  down  as  rapidly  as  possible  to  25°  C.  (77°  F.). 
b In  the  meantime  have  ready  a large  water-bath,  carefully  regulated  at  a 
k'  temperature  of  25°  C.  by  means  of  an  automatic  temperature  regulator. 


242 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Also  thoroughly  clean  and  scald  six  glass  beakers  of  about  16  ounces  capacity, 
and  have  ready  glass  covers  for  each  beaker.  Pour  the  filtered  wort  into 
these  beakers,  placing  about  an  equal  quantity  in  each.  Label  both  beakers 
and  cover  with  numbers  from  1 to  6.  Let  No.  1 remain  in  the  condition 
of  plain  wort  ; to  No.  2 add  1 gram  (15  grains)  of  good  brewers’  yeast  ; 
to  No.  3 add  0*7  gram  (10  grains)  of  good  compressed  yeast.  Prepare 
Nos.  4,  5,  and  6 in  exactly  the  same  manner,  so  as  to  form  a corresponding 
set.  Cover  each  beaker  with  its  glass  cover  and  stand  the  whole  in  the 
water-bath.  Let  the  first  series  remain  undisturbed,  but  aerate  those  of 
the  second  by,  some  five  or  six  times  a day,  pouring  the  contents  of  each 
beaker  into  a clean  empty  beaker,  and  then  back  again  several  times.  After 
each  aeration  replace  the  covers  and  stand  the  beakers  again  in  the  bath. 

After  about  24  hours  examine  each  sample  under  the  microscope.  In 
the  authors’  experiment.  No.  1 at  that  time  contained  no  yeast  ; Fig. 
25  represents  its  appearance  after  three  days.  This,  and  also  several 
figures  which  follow,  are  simply  facsimiles  of  rapid  sketches  made  in  a 
laboratory  notebook. 

The  most  careful  examination  of  field  after  field  revealed  not  a single 


Fig.  25. — Malt  Wort  Allowed  to  Ferment  Spontaneously. 

Left  half  of  field  taken  from  ferment;  right  from  the  same  after  being  sown  in  warm  “yeast  mixture  ” 
for  about  three  hours.  Magnified  about  440  diameters. 

yeast  cell,  while  the  whole  liquid  was  swarming  with  bacteria  ; a slight 
frothy  had  formed  on  the  top.  The  left  hand  side  of  the  figure  shows  the 
wort  ^ as  taken  from  the  beaker,  one  or  two  grains  of  starch  being  visible. 
A portion  of  this  wort  was  then  sown  in  Pasteur’s  Fluid  (Yeast  Mixture), 
and  again  examined  at  the  end  of  three  hours,  being  maintained  for  that 
time  at  26*6°  C.  (80°  F.)  ; its  appearance  is  shown  in  the  right  hand  portion 
of  the  figure.  The  student  is  recommended  to  employ  a fermenting  tem- 
perature of  25°  C.  This  result  was  obtained  not  merely  once,  but  also 
in  a complete  duplicate  series  of  experiments.  The  mode  of  procedure  is 
the  same  as  that  employed  by  those  bakers  who  are  in  the  habit  of  allowing 
their  yeast  to  ferment  spontaneously — except  that  chemically  clean  vessels 
are  employed  throughout.  Another  interesting  point  is  that  although 
yeast  was  being  used  in  the  room  at  the  time,  and  even  beakers,  containing 
actively  fermenting  worts,  were  standing  side  by  side  in  the  same  water- 
bath,  yet  the  loosely  fitting  glass  covers  were  sufficient  to  prevent  the 


MANUFACTURE  OF  YEASTS. 


243 


entrance  of  yeast  cells  or  spores  into  beaker  No.  1 from  external  sources. 

Within  twenty-four  hours  after  being  pitched,  each  sample  was  thus 
examined  under  the  microsocpe.  Nos.  2,  3,  5,  and  6 were  in  a state  of 
vigorous  fermentation.  Subjoined  are  sketches  made  in  Nos.  5 and  6 
respectively. 

Fig.  26  shows  the  yeast  to  be  in  an  actively  budding  state.  Notice 
that  buds  of  different  sizes,  d,  are  attached  to  the  various  cells.  The  interior 
of  the  cells  is  free  from  granulations  ; a few  show,  however,  as  for  instance  c, 
a distinct  vacuole.  In  the  centre  of  one  group  an  old  or  parent  cell,  a, 
is  seen.  The  irregular  fragment  marked  6 is  a small  piece  of  cellulose 
from  the  malt. 


r Fig.  26. — Brewers’  Yeast,  24  hours  after  being  sown  in  Malt  Wort. 
Magnified  about  440  diameters. 


' Fig.  27. — Compressed  Yeast,  24  hours  after  being  in  Malt  Wort. 

U Magnified  about  440  diameters, 

" The  appearance  of  Fig.  27  is  very  similar  to  that  of  the  preceding  one. 
An  example  of  an  old  cell  is  to  be  seen  toward  the  left,  while  the  field  gener- 
ally is  occupied  by  new  cells,  perfectly  free  from  granulation,  and  containing 


244 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


no  vacuoles.  In  general  aspect  the  cells  are  more  ovoid  in  shape,  and 
smaller,  than  those  of  the  brewers’  yeast. 

At  the  end  of  three  days  the  yeasts  were  again  examined,  having  been 
maintained  at  a temperature  of  26*6°  C.  (80°  F.)  for  this  time  ; a sketch 
was  then  made  of  No.  2 sample  of  brewers’  yeast. 


Fig.  28. — Brewers’  Yeast,  three  days  after  being  sown  in  ]\Ialt  Wort. 

Magnified  about  440  diameters. 

After  this  lapse  of  time  the  fermentation  had  very  nearly  ceased.  Instead 
of  observing  a field  covered  with  perfectly  new  cells,  the  majority  of  which 
were  actively  budding,  the  aspect  of  the  yeast  is  far  more  quiescent.  Here 
and  there  an  old  cell  is  still  to  be  seen,  as  at  a.  The  new  cells,  however, 
have  begun  to  assume  somewhat  the  same  appearance.  In  some  of  them 
vacuoles  are  to  be  seen,  but  only  in  a few.  The  sketch  does  not  faithfully 
represent  the  appearance  of  tlie  vacuoles,  as  these  really  only  appear  as 
lighter  parts  of  the  cells,  and  are  not  circumscribed  with  a dark  line,  such 
as  one  has  to  use  in  sketching  them  in  these  figures.  All  the  cells  are  more 
or  less  filled  with  faint,  but  distinct,  granulations. 


Fig.  29. — Compressed  Yeast,  throe  days  after  being  sown  in  Malt  Wort. 
Magnified  about  440  diameters. 


MANUFACTURE  OF  YEASTS. 


245 


There  is  at  the  end  of  this  time  a marked  difference  in  appearance  between 
the  pressed  as  compared  with  the  brew^ers'  yeast.  The  vacuoles  show  much 
more  distinctly,  so  also  the  interiors  of  the  cells  are  much  darker  ; the  sketch 
shows  several  of  parent  cells,  as  at  a,  a. 

Particular  attention  is  drawn  to  the  fact  that  whereas  samples  Nos.  1 
and  4,  which  were  allowed  to  ferment  spontaneously,  swarmed,  after  three 
days,  with  'bacteria  ; the  whole  of  the  other  four  specimens  which  had 
been  sown  with  yeast  showed,  on  observation,  no  foreign  ferments  what- 
ever. It  is  possible  that  some  may  have  been  discovered  by  careful  and 
systematic  examination,  but  the  main  point  is  that,  compared  with  Nos. 
1 and  4,  they  were  to  all  intents  absent.  Now,  save  by  the  addition  of 
yeast,  all  the  samples  were  exposed  to  precisely  the  same  conditions  ; the 
only  conclusion  to  be  drawn  is  that  the  presence  of  yeast  growth  is  more 
or  less  inimical  to  that  of  foreign  or  disease  ferments.  The  practical  lesson 
to  be  learned  from  this  is  that  bakers  who  prepare  their  own  malt  and  hop 
yeasts,  by  sowing  them  with  small  quantities  of  pure  yeast,  not  only  induce 
a healthy  growth  of  pure  yeast  ferments,  but  also  retard  the  growth  and 
development  of  disease  ferments.  The  most  probable  explanation  of  this 
lies  in  the  fact  that,  under  the  conditions  of  the  experiment,  there  is  a 
more  or  less  acute  struggle  for  existence  betv/een  the  two  organisms,  and 
yeast,  being  the  more  vigorous  and  hardy,  grows  and  develops  at  the  expense 
of  the  bacteria.  (Compare  with  the  views  advanced  in  paragraph  378.) 

After  standing  some  time  the  vessels  of  yeast  were  covered  with  a film 
of  Mycoderma  cerevisice  ; a growth  which  has  been  described  in  Chapter  IX., 
and  illustrated  in  Fig.  15. 

Nothing  has  as  yet  been  said  about  the  difference  between  the  series 
of  beakers  that  were  allowed  to  remain  undisturbed,  and  those  which  were 
aerated  from  time  to  time.  Before  doing  so  it  would  be  well  to  describe 
the  results  of  determining  the  amounts  of  gas  evolved  by  the  respective 
samples  on  being  tested  in  the  yeast  apparatus.  At  the  time  these  experi- 
ments were  made,  the  older  form  of  apparatus  was  employed,  in  which 
the  gas  bubbled  up  through  the  water. 

After  standing  three  days  these  samples  of  yeast  were  tested  by  being 
inserted  in  the  testing  apparatus.  Half  an  ounce  of  yeast  mixture  was 
taken,  to  this  was  added  six  ounces  of  the  thoroughly  stirred  yeast.  At 
the  end  of  three  hours  the  following  quantities  of  gas  were  found  to  have 
been  evolved  from  each  : — 

Cubic  Inches. 


No.  I.  Spontaneous  ferment,  undisturbed  . . . . 3*1 

No.  2.  Pitched  with  brewers’  yeast,  undisturbed  . . 16*8 

No.  3.  Pitched  with  pressed  yeast,  undisturbed  . . 35*6 

No.  4.  Spontaneous  ferment,  agitated  . . . . . . 3*7 

No.  5.  Pitched  with  brewers’  yeast,  agitated  . . . . 18*6 

No.  6.  Pitched  with  pressed  yeast,  agitated  . . . . 42*8 


The  experiment  shows  very  clearly  that  the  agitation  has  resulted  in 
the  yeast  being  in  every  instance  more  vigorous  in  action.  In  the  ease 
of  the  spontaneous  ferment  there  was  a distinct,  though  slow,  evolution 
of  gas.  The  samples  pitched  with  the  pressed  yeast  had,  by  the  bye,  more 
than  twice  the  capacity  for  causing  the  evolution  of  gas  than  had  those 
which  were  pitched  with  brewers’  yeast.  It  is  plain  that  agitation  in  some 
way  increases  the  vigour  of  yeast.  Those  students  who  have  earefully 
read  the  section  of  Chapter  IX.,  dealing  with  the  influence  of  oxygen  on 
fermentation,  will  clearly  understand  the  eause  of  such  increase  in  fermenta- 
tive power. 

When  yeast  is  being  made  by  bakers  from  malt  and  hops,  although 


246 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


fermentation  goes  on,  it  is  not  the  fermentation,  as  such,  that  is  wanted. 
The  change  required  is  not  the  production  of  beer,  but  the  growth  and 
development  of  yeast  ; hence  the  operation  should  be  so  conducted  as  to 
induce  the  greatest  yield  of  yeast  in  the  most  active  and  vigorous  form. 
Aeration,  or  “ rousing,""  as  it  is  often  termed,  is,  as  will  now  be  well  under- 
stood, of  considerable  service.  In  brewing  large  quantities  of  yeast,  it 
would  obviously  be  difficult  to  aerate  by  pouring  from  vessel  to  vessel  ; 
the  same  object  may  be  served  by  from  time  to  time  thoroughly  stirring 
the  fermenting  yeast.  This  free  access  of  air  not  only  stimulates  the  growth 
of  yeast,  but  in  addition  is  inimical  to  the  development  of  disease  ferments  ; 
so  much  so,  that  by  careful  working  with  plenty  of  air  a yeast  can  be  made 
to  give  moderately  good  results,  that  would  be  absolutely  unusable  if  fer- 
mentation were  conducted  in  closed  vessels.  It  follows  that  yeast  is  better 
brewed  in  comparatively  shallow  and  open  tubs  than  in  deep  and  closed 
ones. 

The  careful  performance  throughout  of  this  experiment  will  not  only 
be~an  instructive  exercise  on  fermentation,  but  will  also  afford  good  practice 
with  the  microscope. 

396.  Formula  for  Manufacture  of  Malt  and  Hops  Patent  Yeast. — The 

following  formula  for  the  manufacture  of  patent  yeast  is  taken  from  “ The 
Miller,"" — 40  gallons  of  water  and  2 lbs.  of  sound  hops  are  boiled  together 
for  half  an  hour  in  a copper,  and  then  passed  over  a refrigerator,  and  thus 
cooled  to  a temperature  of  71°  C.  (160°F.).  The  liquor  passes  from  the 
refrigerator  to  a stout  tub  ; IJ  bushels  (about  63  lbs.)  of  crushed  malt  are 
then  added,  and  the  mixture  thoroughly  stirred.  The  mash  is  allowed 
to  stand  at  that  temperature  for  IJ  hours,  filtered  from  the  grains,  and 
then  rapidly  cooled  to  21°  C.  (70°  F.)  The  passage  over  the  refrigerator 
serves  also  to  thoroughly  aerate  the  wort.  Spontaneous  fermentation  is  then 
allowed  to  set  in,  and  the  yeast  is  usually  ready  for  use  in  24  hours,  but 
is  in  better  condition  at  the  end  of  two  days.  All  fermenting  tubs,  and 
other  vessels  and  implements  used,  are  kept  clean  by  being  from  time  to 
time  thoroughly  scalded  out  with  live  steam.  The  result  is  the  production 
of  a yeast  of  very  high  quality.  Or  fermentation  ^may  be  started  by  the 
addition  of  a small  quantity  of  good  yeast. 

397.  Suggestions  on  Yeast  Brewing ; what  to  do,  and  what  to  avoid.— 

The  quantities  given  above  are  larger  than  those  required  by  many  bakers, 
but  the  formula  may  be  adopted  for  smaller  brewings  by  taking  a half, 
or  quarter,  or  some  other  proportion  of  each  ingredient.  In  connection 
with  brewing,  the  first  consideration  is  the  room  ; this  should  not  be  in 
the  same  part  of  the  bakehouse  as  the  ovens.  Select,  if  possible,  a room 
having  an  equable  temperature  of  from  65  to  70°  F.  Stout  tubs  of  appro- 
2>riate  size  should  be  used  for  brewing  ; these  should  be  about  the  same 
w'idth  as  depth.  Before  commencing,  clean  all  tubs  and  implements  with 
boiling  water.  The  hops  are  better  boiled  in  a copper  ; iron  vessels  are 
apt  to  discolour  them,  especially  if  the  vessels  are  in  the  slightest  degree 
rusty.  Let  the  hop  liquor  cool  down  to  the  temperature  given,  before 
adding  the  malt,  as  a temperature  much  higher  than  from  65  to  70°  C. 
destroys  the  diastatic  power.  On  no  account  boil  the  malt  : some  bakers 
place  malt  and  hops  together,  and  boil  the  two,  under  a mistaken  idea 
that  'they  get  more  extract  from  the  malt.  The  result  is  that  diastasis 
is  arrested  long  before  the  whole  of  the  starch  is  converted  into  dextrin 
and  maltose.  For  the  same  reason,  fifteen  minutes  is  too  short  a time  for 
the  mashing  to  be  continued.  The  baker  not  only  requires  to  saccharify 
his  malt,  but  it  is  also  necessary  for  him  to  convert  as  large  a proportion 
as  possible  of  his  dextrin  into  maltose.  This  is  hindered  either  by  using; 


MANUFACTURE  OF  YEASTS. 


247 


too  high  a temperature,  or  mashing  for  too  short  a time.  Starting  with  a 
mashing  liquor  at  65  to  70°  C.,  and  mashing  for  from  IJ  to  2 hours,  gives 
about  the  best  results.  The  cooling  after  removal  from  the  grains,  which 
may  be  washed  or  “ sparged  ""  with  a small  quantity  more  water,  must 
be  done  quickly,  so  to  as  have  the  wort  for  as  short  a time  as  possible  at  a 
temperature  of  from  35  to  40°  C.,  as  at  that  temperature  bacterial  fer- 
mentations proceed  most  vigorously.  The  wort  at  21  *5°  C.  (70°  F.)  may 
either  be  pitched  with  a small  quantity  of  yeast  reserved  from  the  last 
brewing,  or  by  the  addition  of  a small  quantity  of  good  fresh  compressed 
yeast.  If  wished,  the  fermentation  may  be  allowed  to  set  in  spontaneously, 
as  suggested  in  the  preceding  paragraph,  in  which  case  a “ virgin  ""  yeast 
is  produced.  It  is  doubtful,  however,  whether  this  is  to  be  recommended 
in  most  cases.  The  risk  of  spoiled  yeast  is  greater,  and  at  times  alcoholic 
fermentation  does  not  set  in  at  all,  or  too  late  to  prevent  its  being  preceded 
by  excessive  lactic  and  other  foreign  fermentations.  The  temperature 
should  not  be  allowed  to  rise,  during  fermentation,  much  above  21  to  22°  C. 
In  summer  time  there  is  a great  tendency  for  a rapid  rise  to  set  in  ; this 
may  be  controlled  by  placing  an  attemperator  in  the  wort,  and  passing 
a stream  of  cold  water  through.  An  attemperator  consists  of  a properly 
arranged  series  of  pipes,  through  which  hot  or  cold  water  at  will  may  be 
passed.  Temperatures  must  in  all  cases  be  got  right  by  actual  use  of  the 
thermometer.  From  time  to  time,  stir  the  fermenting  wort  so  as  to  rouse 
or  aerate  it.  When  the  yeast  is  made,  keep  it  freely  exposed  to  air.  In 
making  patent  yeast  it  is  very  poor  economy  to  stint  either  malt  or  hops  : 
a weak  wort  produces  a much  less  healthy  and  vigorous  yeast  than  does  a 
strong  one,  beside  being  much  more  subject  to  disease  fermentation,  and 
eonsequent  acidity.  And,  when  made,  the  dilute  yeast  shows  no  saving, 
because  so  much  more  of  it  has  to  be  taken  in  order  to  do  the  same  work. 


398.  Specific  Gravity  of  Worts,  and  Attenuation. — ^In  addition  to  taking 
the  temperature  of  his  worts,  the  brewer  also  tests  the  density  or  specific 
gravity  of  each  sample.  This  is  done  as  a means  of  estimating  the  amount 
of  soluble  extract  obtained  from  the  malt.  The  maltose  and  other  soluble 
carbohydrates,  yielded  on  mashing,  increase  the  specific  gravity  of  the 
wort.  Taking  the  density  of  water  as  1000,  each  gram  of  carbohydrate 
in  100  C.C.,  or,  what  amounts  to  the  same  thing,  each  lb.  of  carbohydrate 
in  10  gallons  of  the  wortincreasesthedensity  of  the  solution  by  3*85.  Thus, 
suppose  that  a wort  is  found  at  15*5°  C.  (60°  F.)  to  have  a specific  gravity  of 
1011*5,  then 


1011*5  - 1000 
3*85 


= 3 = weight  in  lbs.  of 


sugar  and  other  solid  matter  in  10  gallons  of  the  clear  wort.  As  the  density 
of  a liquid  varies  with  its  temperature,  all  densities  are  best  taken  at  the 
uniform  temperature  of  15*5°  C. 

The  Inland  Revenue  Act  of  1880  assumes  that  2 bushels  of  average 
malt,  weighing  84  lbs.,  will  produce  a barrel  (36  gallons)  of  wort  having 
a density  of  1057.  Accepting  this  estimate  as  correct,  and  assuming  that 
the  40  gallons  of  water  employed  in  the  previously  given  recipe,  together 
with  the  small  extra  quantity  used  in  sparging  or  washing  the  grains,  yield 
after  loss  through  evaporation  40  gallons  of  wort  ; then  the  wort  produced 
ought  to  have  a density  of  1038*3,  which  is  equal  to  almost  exactly  10  lbs. 
of  solid  extract  per  10  gallons  of  wort.  Working  with  comparatively 
imperfect  methods,  and  in  small  quantities,  the  baker  cannot  expect  his 
malt  to  yield  the  full  extract,  but  as  a matter  of  practice  he  ought  at  any 
rate  to  get  nothing  less  than  a density  of  1030.  One  of  the  most  important 
sources  of  loss  arises  from  imperfect  sparging  of  the  grains  ; these  should 


248 


THE  TECHNOLOGY  OF  BREAD-MAKING 


be  washed  once,  and  may  then  with  economy  be  put  into  a small  press 
and  squeezed  dry.  Of  course,  if  with  extra  washing  water  the  volume  of 
the  wort  is  increased,  then  the  density  will  naturally  fall.  Testing  the 
density  of  his  wort  is  not  only  of  importance  to  the  baker,  as  a measure 
of  the  degree  of  efficiency  with  which  he  is  extracting  the  valuable  matters 
of  his  malt,  but  is  also  a test,  of  the  highest  value,  of  the  regularity  of  his 
work.  If  one  day  a wort  of  comparatively  high  density  is  being  attained, 
and  on  another  one  of  low  density,  something  is  wrong,  and  must  be  righted. 
The  baker  should  always  endeavour  to  have  his  worts  at  the  same  density 
when  ready  for  pitching  : 1030  may  be  taken  as  a very  good  standard 
to  work  at.  If  it  is  found  in  practice  that  the  densities  fall  below  this, 
mash  with  comparatively  less  water  ; if  the  densities  run  too  high,  dilute 
the  wort  with  water  until  of  the  right  density  before  pitching.  The  neces- 
sary quantity  of  water  to  add  may  be  easily  calculated,  on  remembering 
that  the  volume  of  the  wort  is  in  inverse  proportion  to  the  density,  less  1000. 
Thus,  supposing  that  the  40  gallons  of  wort  are  found  to  have  a density 
of  1035,  then 

as  30  : 35  : : 40  : 46  gallons. 

The  wort  will  have  to  be  made  up  to  46  gallons,  therefore  6 gallons  of  water 
must  be  added.  The  quantity  of  wort  produced  should  always  be  mea- 
sured ; to  do  this,  determine  once  for  all  the  capacity  of  the  fermenting 
tubs  in  the  following  manner  : — Prepare  a staff  about  an  inch  square ; 
pour  water  into  the  tub,  gallon  by  gallon,  and  at  each  addition  put  in  the 
staff  and  mark  on  it  the  height  of  the  water.  This  operation  once  com- 
pleted, the  quantity  of  wort  made  can  at  any  time  be  determined  simply 
by  plunging  the  staff  into  the  tub  and  reading  off  the  number  of  gallons 
as  marked  on  it. 

For  practical  purposes,  the  density  of  a wort  is  best  determined  by  a 
hydrometer ; this  instrument  is  made  either  of  brass  or  glass.  It  has  a 
weighted  bulb  at  the  bottom,  and  a long  graduated  stem  ; accompanying 
the  hydrometer  is  a tall  glass  jar,  known  as  a hydrometer  jar.  Fill  this 
jar  with  wort  at  the  right  temperature,  and  place  in  the  hydrometer  ; 
as  soon  as  it  comes  to  rest,  read  off  the  graduation  which  coincides  with 
the  level  of  the  liquid  ; the  number  gives  the  density.  For  the  baker, 
the  most  convenient  hydrometer  is  one  graduated  in  single  degrees,  from 
1000  to  1040.  The  hydrometer  is  also  sometimes  known  as  a saccharometer. 

As  fermentation  proceeds,  the  density  of  the  liquid  becomes  less,  and 
at  the  same  time  it  loses  its  sirupy  consistency — hence  the  brewer  states 
it  to  have  become  “ attenuated.'' 

399.  Microscopic  Sketches  of  Patent  Yeast. — In  Plate  II.  are  given 
microscopic  sketches  made  of  patent  yeasts  collected  in  the  South  of  England. 

The  sketches  marked  respectively  a and  h were  drawn  from  samples 
of  patent  yeast,  both  obtained  in  the  same  town,  but  from  different  bakers, 
during  the  summer.  The  sample  marked  a was  evidently  prepared  in 
a strong  wort  ; in  fact,  at  the  time  of  examination  the  yeast  was  still  sweet 
through  presence  of  maltose  in  considerable  quantity,  and  had  a high 
density.  The  yeast  was  not  free  from  disease  ferments,  but  still  compared 
remarkably  favourably  in  this  respect  with  all  other  samples  examined. 
One  specially  noticeable  point  about  the  sample  was  the  elongated  shape 
of  the  cells  ; some  were  not  merely  ovoid,  but  even  decidedly  pear-shaped. 
One  sketched  shows  this  peculiarity  in  a very  marked  manner.  This  yeast 
was  at  the  time  yielding  very  good  results  ; the  bread  was  sweet  and  of 
good  flavour.  One  is  in  doubt  with  regard  to  sample  h,  whether  it  should 
be  viewed  as  an  example  of  alcoholic  or  bacterial  fermentation  ; certainly 
the  latter  ferments  are  about  as  plentiful  as  yeast  cells.  The  yeast  con- 


MANUFACTURE  OF  YEASTS. 


249 


tained  very  little  either  of  maltose  or  hops  ; in  fact,  it  had  evidently  been 
brewed  with  as  little  as  possible  of  these  ingredients  employed.  Readers 
will  probably  not  be  surprised  that  yeast  a produced  a far  superior  loaf 
of  bread  than  did  yeast  h.  The  sample  c is  likewise  of  considerable  interest ; 
it  was  also  taken  during  the  summer.  The  baker  was  in  the  habit  of,  at 
the  close  of  his  yeast  brewing,  setting  aside  a portion  for  the  purpose  of 
pitching  his  next  lot  of  wort.  This  pitching  yeast  was  stored  in  a corked 
bottle.  This  also  was  a yeast  brewed  in  a poor  wort,  although  not  so  bad  as 
sample  h.  Notice  particularly,  in  c,  the  chain  of  elongated  cells  ; these 
are  often  noticed  in  yeast  grown  without  sufficient  aliment,  and  the  sketch 
sliows  a striking  example. 

Scotch  Flour  Barms. 

400.  Flour  Barms,  Thoms’  Formulae. — The  following  descriptions  of 
Scotch  Flour  Barms  are  from  the  pen  of  the  late  Mr.  Thoms  of  Alyth,  a 
well-known  authority  on  Bread-making.  Although  WTitten  some  time 
ago,  they  describe  very  closely  the  methods  still  in  use  in  Scotland  : — 

“ There  are  many  kinds  of  flour  barms  used  in  Scotland,  in  fact  all 
are  flour  barms  ; but  for  the  present  I will  treat  of  two  of  the  latest  and 
best.  These  are  ‘ Parisian  Barm  ’ and  ‘ Virgin  Barm.’  Virgin  differs 
from  Parisian  only  in  being  spontaneously  or  self-fermented.  Parisian 
barm  was  introduced  from  Paris  to  Scotland,  by  a baker  near  Edinburgh, 
about  the  year  1865.  It  is  essentially  a leavening  ferment  ; a scientiflc 
modiflcation  of  the  systems  of  ancient  Egypt  and  present  France.  After 
its  introduction  to  Scotland  its  use  spread  rapidly,  and  it  alone  is  used  in 
all  the  machine  bread  factories  there,  and  in  a number  of  the  best  estab- 
lishments in  the  north  of  Ireland.  The  Parisian  is  easier  to  make,  but 
easier  to  spoil.  All  that  is  required  is  skiU  to  select  the  materials,  and 
knowledge,  founded  on  experience,  to  guide  the  process  of  fermentation, 
which  results  in  inert  flour  and  water,  and  infusions  of  malt  and  hops,  being 
converted  into  the  vital,  seff-propagating  and  carbonic  acid  producing 
substance  we  call  barm,  which  makes  fermented  bread  light  and  vesiculated.” 

401.  “ Virgin  Barm  : Things  Required. — ^A  30  or  32  gallon  tub  ; a 
small  tub  or  vessel  for  malt-mashing  ; 10  lbs.  malt  ; 3 oz.  hops,  and  a jar 
in  which  to  infuse  them  ; about  40  lbs.  flour,  of  which  one-third  should  be 
American  Spring  straight  and  two-thirds  Talavera  wheat  flour,  or  sound 
red  Winter  ; 2 or  3 oz.  salt  ; 8 or  12  oz.  sugar  ; a handful  of  flour  ; and 
about  18  gallons  of  boiling  water.  (The  gallon  here  means  the  Imperial, 
holding  10  lbs.  water  at  a temperature  of  60° F.) 

402.  “ How  to  Use  or  Manipulate  them. — ^Mash  the  malt  for  1 J hours 
in  3 gallons  of  water  after  it  has  been  cooled  to  160°  F.  ; infuse  the  hops 
the  same  time  in  1 gallon  of  water  poured  over  the  hops  at  a boiling  tem- 
perature ; then  strain  the  malt  and  hop  infusions  into  the  barm  tub  : now 
sparge  or  wash  the  draining  malt  grains  with  another  gallon  of  water  at  a 
temperature  of  190°  or  200°  F.  Note,  the  malt  grains  are  not  pressed  in 
any  way,  only  allowed  to  drain.  When  the  water  has  about  stopped  running 
from  the  grains,  the  liquor  in  the  tub  should  show  a temperature  of  140° 
-146°  F.,  then  well  and  thoroughly  mix  in  the  flour  with  the  hands.  The 
next  stage  is  scalding  this  mixture  or  thin  batter  with  7 gallons  of  boiling 
water,  and  stirring  sharply  with  a stick.  Begin  by  pouring  in  2 gallons, 
and  stirring  it  well  up  and  from  the  bottom  and  all  round,  then  add  another 
3 gallons  and  give  more  and  sharp  stirring,  and  finish  with  another  2 gallons 
and  more  stick  work.  The  scalded  batter  is  then  a thick  jellyish  paste. 
The  water  used  in  malt  and  hop  infusions  and  sparging  is  5 gallons,  in 


250 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


scalding  7 gallons,  making  in  all  12  gallons.  I mentioned  18  gallons  because 
it  is  desirable  to  have  more  boiling  water  than  required. 

403.  “ Fermentation. — ^The  barm  tub  and  contents  are  left  in  the  brew- 
house  uncovered  for  21  hours  or  so.  During  that  time  the  mixture  under- 
goes several  changes.  The  scalding  water  bursts  a proportion  of  the  starch 
granules  of  the  flour,  converting  them  into  starch  paste  : the  diastase 
of  the  malt  inverts  or  hydrates  this  paste  into  a sugar,  maltose,  and  a brown^ 
gummy  body,  dextrin.  The  mixture,  after  scalding,  tastes  very  sweet  ; 
in  half  an  hour  after  it  is  sweeter,  and  thinner,  and  browner.  These  changes 
continue  for  several  hours,  then  a distinct  acid  taste  is  felt.  At  the  end 
of  21  hours  the  mixture  is  strained  from  one  tub  into  another,  so  as  to 
aerate  it.  When  it  has  cooled  down  to  84°  F.,  mix  in  the  salt,  sugar,  and 
a handful  of  flour,  and  keep  the  tub  lightly  covered,  or  uncovered,  in  a 
place  where  the  now  slightly  fermenting  mixture  will  not  fall  below  a tem- 
perature of  80°  F.,  or  rise  over  84°  F.  Supposing  this  is  done  24  hours 
after  brewing,  then  during  the  next  24  hours  stir  up  the  mixture  three 
times — the  number  of  times  depends  on  the  fermentation  being  free  or 
sluggish — and  note  the  heat,  and  at  the  end  of  the  24  hours  again  strain 
gently  from  one  tub  to  another.  In  another  12  hours  stir  up  again  ; it 
will  then  be  in  vigorous  fermentation,  and  will  rise  and  then  fall.  When 
nearly  full  dowm,  or  when  a lighted  match  will  burn  within  three  or  four 
inches  of  the  surface,  remove  the  tub  to  a cool  place.  This  will  be  on  the 
third  day  after  brewing.  This  barm  could  be  used  in  a sponge  the  same 
day,  but  it  is  far  better  on  the  fourth  and  fifth  day  after  brewing. 

404.  “ Parisian  Barm. — ^The  materials,  and  quantities  and  manipulation, 
are  the  same  as  for  Virgin.  Only  in  about  24  or  27  hours  after  brewing, 
and  when  the  mixture  has  cooled  dowm  to  84°-86°  F.  in  winter,  and  76°- 
78°  F.  in  summer,  instead  of  putting  in  salt,  sugar,  and  flour,  and  letting 
it  self -ferment,  it  is  stored  or  set  aw^ay,  with,  in  winter,  about  IJ  gallons 
old  barm,  or  Virgin  ; in  summer,  about  1 gallon  ; and  the  tub  is  best  kept 
uncovered  during  and  after  fermentation,  wiiere  the  temperature  is  be- 
tween 60°  F.  and  70°  F.  In  this  case  active  fermentation  is  about  over 
in  16  to  24  hours,  wiien  it  is  better  to  remove  the  tub  to  a cooler  place. 
With  this  barm,  as  with  Virgin,  and  every  other  yeast,  it  is  not  advisable 
to  use  it  in  sponge  immediately  or  shortly  after  it  has  dropped.  They 
should  be  left  undisturbed  in  a cool  place  at  a temperature  betw^een  40°  F. 
and  60°  F.  Barm  at  this  stage  should  be  kept  in  shallow^  tubs,  or  coolers, 
where  a large  surface  is  exposed  to  free  oxygen.'' 

405.  Microscopic  Character. — ^View^ed  under  the  microscope,  Scotch 
flour  barms  ahvays  show^  a certain  proportion  of  lactic  ferments  as  a nor- 
mal constituent.  Thoms  argues  that  their  presence  is  beneficial,  and  states, 
in  favour  of  that  view,  that  when  he  has  taken  steps  for  brewing  barm 
in  w'hich  lactic  ferments  are  absent,  that  the  bread  is  of  inferior  quality. 
The  probable  function  of  lactic  ferments  during  panification  will  be  dealt 
w'itli  in  a future  cliapter.  Scotch  bread  has  always  a slight  acid  flavour, 
totally  distinct  from  wFat  is  understood  in  England  as  “ sourness  " of 
bread,  but  more  resembling  in  type  the  flavour  of  buttermilk.  It  should 
be  exj^lained  that  this  peculiarity  is  not  quoted  as  a fault  : in  fact,  those 
accustomed  to  bread  of  tliis  flavour  find  something  lacking  if  the  acidity 
be  absent. 

406.  Parisian  Barm,  Montgomerie. — On  the  occasion  of  the  writing  of 
the  present  edition  of  this  work  Mr.  J.  Montgomerie,  of  Glasgow,  furnished 
the  authors  wdth  the  follow  ing  account  of  the  manufacture  of  Parisian  barm 
as  now'  conducted  in  Scotland. 


MANUFACTURE  OF  YEASTS. 


251 


“ Sixteen  Scotch  pints  (of  two  Imperial  quarts  each)  of  water  at  164°  F. 
are  mashed  with  24  lbs.  of  crushed  malt  for  from  to  4 hours,  stand- 
ing in  a warm  place  so  as  to  ensure  as  little  loss  of  temperature  as 
possible.  It  is  then  transferred  to  a malt  press,  and  the  wort  drawn  off. 
The  wort,  with  the  exception  of  3 pints,  is  put  in  the  tub,  and  3 pints  of 
water  added  at  a temperature  to  bring  it  up  to  120°  F.  (You  have  13 
pints  of  wort  and  3 pints  of  water,  making  1 J lbs.  malt  to  the  pint  of  water). 
Put  in  112  lbs.  flour.  A good  barm  flour  is  a blend  of  flour  obtained  from 
spring  and  winter  wheats  in  about  equal  proportions.  The  wort  and  flour 
are  then  stirred  into  a batter.  Forty  pints  of  boiling  water  are  then  stirred 
in,  4 pints  at  a time.  The  starch  in  the  flour  will  gelatinise  at  the  thirty- 
second  pint.  The  last  8 pints  are  added  when  it  begins  to  liquefy.  The 
3 pints  of  wort  are  then  added. 

To  take  off  a scald  with  a 

4 pint  mash,  the  temperature  of  the  wort  is  140  degrees  F. 


6 

55 

55 

55 

134 

55 

8 

55 

55 

55 

132 

55 

10 

55 

55 

55 

130 

55 

12 

55 

55 

55 

126 

55 

14 

55 

5 5 

55 

124 

55 

16 

55 

55 

120 

55 

20 

55 

55 

55 

120 

55 

24 

55 

55 

55 

120 

55 

30 

55 

55 

55 

116 

55 

35 

55 

55 

5 5 

110 

55 

40 

55 

55 

100 

% s 

The  last  is  the  biggest  taken  off  in  any  factory. 

“ The  scald  is  then  cooled  until  the  temperature  drops  to  between  80 
and  90°  F.  in  winter,  and  60  and  70°  F.  in  summer.  If  the  Barm  Cellar  is 
kept  at  a constant  temperature  of,  say,  56°  F.,  then  80°  F.  is  a very  good 
temperature  to  scald  at. 

“ Storing  the  Scald.  Take  the  temperature  of  the  scald  and  add  13  pints  of 
matured  barm  as  a store,  ^.e.,  1 pint  of  barm  to  4 pints  of  scald.  (As  may 
be  gathered  from  the  preceding  description,  the  “ store  ” is  a portion  of  old 
barm  added  for  the  purpose  of  pitching,  or  starting  fermentation.)  Allow 
it  to  lie  for  3 or  4 hours,  then  divide  into  two  or  three  suitable  vessels  and 
remove  to  the  Barm  Cellar,  which  should  be  large  and  airy,  to  ferment. 
The  barm  will  come  up  its  height  in  18  hours,  and  then  gradually  settle 
down  with  a clear  round  bell  on  the  top  on  the  second  day  of  fermenting. 
On  the  third  day  it  will  begin  to  clear  off,  and  on  the  fourth  will  be  cleared 
off.  The  barm  is  now  ready  for  using,  but  most  bakers  prefer  to  allow 
it  to  mature  to  the  fifth  day,  as  it  gives  a better  flavoured  loaf,  and  the 
fermentation  of  the  dough  is  more  easily  controlled.  In  the  event  of  the 
barm  showdng  signs  of  hardness,  decrease  the  quantity  of  malt  used  at 
mashing,  and  if  of  greenness,  increase  the  quantity  of  malt. 

“ To  keep  barm  right,  it  is  essential  that  everything  should  be  kept 
scrupulously  clean,  with  a plentiful  supply  of  fresh  air,  and  that  the  barm 
be  stored  and  kept  at  a constant  temperature."^ 

407.  Scottish  Barms,  Meikle. — ^Mr.  J.  Meikle,  the  well-known  baker 
and  teacher  of  bread-making  classes  in  Belfast,  has  read  through  the  de- 
scriptions of  Scottish  methods  given  on  the  authority  of  Thoms  in  the  older 
edition  of  this  work,  and  has  supplied  the  following  addendum  thereto  for 
which  the  authors  express  their  acknowledgments  and  thanks.  The  various 
data  were  submitted  by  Mr.  Meikle  to  a number  of  bakers  in  Scotland,  and 
may  therefore  be  taken  as  thoroughly  reliable  in  every  way. 


252 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

Compound  Barm. 

40  lbs.  Water. 

10  lbs.  Malt. 

4 lbs.  Store. 

4 oz.  Hops. 

2 oz.  Salt. 

Mash  3 hours. 

“ Compound  Barm  is  not  now  used  to  the  extent  it  was  at  onetime,  but 
many  of  ithe  older  bakers  agree  that  it  is  the  barm  for  flavour  in  bread. 
Take  10  lbs.  of  water  and  mix  in  the  hops,  bring  the  water  to  the  boil  and 
allow  to  simmer  for  a few  minutes.  Transfer  this  to  a 5 gallon  tub  and 
add  30  lbs.  of  water  at  180°  F.  to  make  up  to  40  lbs.  Throw  a flour  bag  over 
the  tub  and  allow  the  liquor  to  cool  to  164°  F.,  then  stir  in  the  malt,  cover 
up  the  tub  well,  and  keep  it  in  a warm  corner  for  about  three  hours.  At 
the  end  of  that  time  run  the  ‘ mash  " into  a barm  press  and  press  out  all 
the  liquor.  Cool  this  as  quickly  as  possible  to  72°  F.,  stir  in  the  store  and 
the  salt,  then  set  the  whole  to  ferment  for  36  hours.  At  the  end  of  that 
time  the  gas  should  all  be  gone  ; it  should  in  fact  have  ceased  to  hiss  : if 
hissing  still  goes  on  the  barm  must  not  be  used  as  it  is  not  ready.  Some 
Scotch  bakers  will  not  touch  this  barm  until  hissing  ceases,  but  a good 
rousing  stir  will  help  matters  considerably. 

“I  have  used  pounds  in  connection  with  liquor,  and  will  use  this  system 
in  what  follows  for  the  reason  that  the  Scotch  ‘ pint " does  not  always 
mean  a definite  quantity.  It  generally  means  half  an  Imperial  gallon, 
but  often  it  means  a real  old  Scotch  pint,  which  is  equal  to  about  3 Imperial 
pints  or  almost  4 lbs.  avoirdupois.  An  Imperial  gallon  of  water  weighs 
10  lbs.  avoirdupois,  so  that  the  figures  given  divided  by  5 give  the  number 
of  Scotch  pints  (half  gallons)  as  generally  in  use,  and  divided  by  4 give 
old  Scotch  pints. 

Virgin  Barm. 

20  lbs.  Water  at  125°  F. 

32  lbs.  Flour. 

45  lbs.  Water  at  212°  F. 

10  lbs.  Store. 

“To  lie  12  hours  before  ‘Storing,’  or  till  it  falls  to  80° F.  ; 60  hours 
afterwards  it  will  be  ready. 

“ Mix  the  water  at  125°  F.  with  the  flour  into  a stiff  paste  by  hand,  making 
sure  that  boiling  water  is  immediately  afterwards  available.  Scrape  down 
the  batter  in  the  inside  of  the  tub,  then  add  boiling  water  2 pints  at  a- 
time  (a  gallon)  stirring  vigorously  between  each  addition  with  a stick  of 
the  nature  of  a broom  handle.  The  mixture  will  be  easy  to  stir  at  first, 
but  when  the  starch  cells  begin  to  burst  it  will  ‘ grip,’  and  care  must  be 
taken,  first,  to  keep  clear  of  lumps,  second,  not  to  add  too  much  water. 
Tlie  strength  of  the  final  barm  depends  on  the  solids,  not  upon  the  amount 
of  water  added.  The  scald  must  now  lie  for  about  12  hours,  when  it  will 
have  not  only  become  cool,  but  also  thin,  and  slightly  tart  (acid.)  Now 
add  the  store  and  a handful  of  flour,  stir  well  and  allow  to  ferment  for  56 
liours..  Foaming  will  start  at  the  sides  and  will  gradually  cover  the  top  : 
if  a ring  still  remains  in  the  centre  when  the  barm  is  to  be  used  the  baker  must 
make  up  his  mind  for  weak  fermentation.  Real  Virgin  Barm  is  not  stored 
at  all,  but  I have  never  seen  such  barm  worked.  Virgin,  so  called,  has  been 
gradually  displaced  by  Parisian,  but  I have  seen  it  used  many  years  and 
have  seen  much  good  bread  made  from  it. 


253 


MANUFACTURE  OF  YEASTS. 

Parisian  Barm. 

15  lbs.  Water)  , , ^ac\o^ 

3f  lbs.  Malt 
22  lbs.  Flour. 

35  lbs.  Water  at  212°  F. 

10  lbs.  Store. 

‘‘To  lie  12  hours  before  storing  or  until  it  reaches  76°  F.  ; ready  50  hours 
afterwards. 

“This  is  the  barm  of  Scotland  to-day  and  is  made  as  follows.  Mash  the 
malt  and  water  as  for  compound  barm  ; that  is  measure  the  water  in  a 
clean  tub  at  a temperature  of  about  180°  F.,  cover  this  up  and  allow  the 
temperature  to  fall  to  162°  F.,  then  add  the  malt.  The  reason  for  using 
water  at  180°  F.  is  to  ensure  the  tub  being  thoroughly  warmed  up  : by 
well  covering  up  after  mashing  the  proper  temperature  is  kept  up  for  a 
longer  period — the  subsequent  barm  will  be  no  good  unless  care  is  exercised 
at  the  very  start.  In  two  and  a half  hours  wring  off  the  liquor  and  add 
sufficient  water  at  150°  F.  to  bring  up  the  total  to  15  lbs.  and  the  temperature 
to  128°  F.,  stir  in  the  flour  by  hand,  and  afterwards  add  the  boiling  water, 
and  stir  vigorously  as  already  described  for  Virgin  barm.  The  scald  should 
not  be  so  stiff  as  for  Virgin,  and  should  taste  sweet  when  newly  made. 
It  begins  to  thin  almost  immediately,  and  as  it  lies  gets  a little  sharper  in  taste; 
it  should  not,  however,  be  cooled  artificially.  When  storing  stir  vigorously 
and  well.  Parisian  barm  while  fermenting  behaves  like  a thin  ferment 
made  with  distillers^  yeast,  sugar  and  a handful  of  flour,  only  the  bells  or 
gas  bubbles  are  larger  and  brighter.  The  barm  has  the  strength,  with- 
out the  “ rampness,'"  of  compound,  and  the  mildness  without  the  weakness 
of  Virgin.  Of  suitable  barm  flours  more  further  on.  In  the  making  of 
scalds  in  large  places  machinery  has  been  utilised.  The  stirring  machine 
is  used  with  success  in  making  large  scalds  in  the  factories,  such  scalds 
being  afterwards  divided  amongst  several  tubs  for  fermenting  purposes.'* 
{Personal  Communication,  October,  1910). 


CHAPTER  XIII. 

PHYSICAL  STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN. 


408.  Functions  of  the  Wheat  Grain. — ^The  wheat  grain  is  that  part  of  the 
plant  on  which  falls  the  task  of  performing  the  functions  of  reproduction, 
hence  all  its  parts  are  specially  adapted  to  that  purpose.  The  germ,  or 
embryo,  of  wheat,  really  the  true  seed,  is  that  portion  of  the  grain  which 
ultimately  develops  into  the  future  plant.  The  main  body,  composed 
principally  of  starchy  matter,  is  termed  the  “ endosperm  ''  : its  function  is 
to  supply  the  germ  with  food  during  the  first  stages  of  its  growth.  Besides 
these  there  are  the  various  outer  and  other  coverings,  destined  for  the  ade- 
quate protection  of  the  seed,  which  together  constitute  the  bran.  The 
physical  structure  of  the  wheat  grain  requires  for  its  systematic  study  the 
use  of  the  microscope  : the  descriptions  following  therefore  include  practical 
directions  for  microscopic  observation.  The  arrangement  adopted  is  that 
most  easily  followed  by  the  student  in  a course  of  actual  microscopic  work. 
For  earlier  studies  it  is  well  to  obtain  from  the  dealer  ready-mounted  longi- 
tudinal and  vertical  sections  of  a grain  of  wheat.  In  every  case,  practise 
sketching  what  is  seen  : as  before  stated,  the  accompanying  figures  are 
facsimiles  of  those  which  the  student  should  himself  make. 

409.  Longitudinal  Section  of  Whole  Grain. — In  the  first  place,  examine 
the  longitudinal  section  of  the  grain  of  wheat  with  the  3-inch  objective  ; the 
whole  of  the  grain  will  then  be  in  the  field.  Try,  in  the  next  place,  to  make 
a sketch  of  it.  For  this  purpose  the  student  should  use  a camera  lucida  if 
he  should  possess  one.  Trace  in  the  outline  and  other  principal  lines  with 
a hard  pencil  ; then  go  over  them  with  a lithographic  pen  and  liquid  Indian 
ink.  It  will  be  impossible  to  get  in  all  the  details  ; the  effort  should  be 
rather  to  show  what  is  essential  ; thus  the  object  of  the  sketch  with  the  low 
objective  is  to  get  an  idea  of  the  general  shape  and  arrangement  of  the 
diferent  constituent  parts  of  the  grain.  When  the  drawing  is  complete, 
mark  underneath  the  number  of  diameters  to  which  it  has  been  magnified. 

In  Plate  VI.  is  given  a section  through  the  crease  of  the  grain,  which  is 
shown  in  elevation  by  shading  on  the  left-hand  side  of  the  figure.  The 
whole  of  the  figure  has  been  obtained  by  careful  tracing  in  the  authors' 
laboratory  from  typical  slides,  and  is  throughout  a faithful  representation 
of  the  grain.  The  germ  is  seen  at  the  lower  end  of  the  figure,  and  a fair 
idea  of  its  size,  compared  with  that  of  the  endosperm,  which  constitutes  the 
remainder  of  the  grain,  may  be  obtained.  Enclosing  both  germ  and  endo- 
sperm is  the  bran.  With  the  low  power,  which  the  student  has  been  directed 
to  use,  the  square  cells  of  the  bran  lining  the  interior,  and  known  as  aleurone 
cells,  are  just  visible.  The  name  commonly  given  to  theseis,  by  the  by,  a 
misnomer  ; they  are  not  “ gluten  " cells,  for  the  reason  that  they  contain 
no  gluten.  The  more  minute  examination  of  the  grain  is  best  made  by  the 
aid  of  tlie  liiglier  powers,  and  sliows  more  of  the  details  drawn  in  Plate  VI., 
to  which  reference  is  made  in  the  paragraphs  which  follow. 

The  various  parts  of  the  grain  are  fully  indicated  on  the  plate  itself. 

254 


Plate  VI. 


Tlairs  of  J5,c^‘cl, 


CutCcLe, 
E/tCc/ir;z, 
Entio^-arfL 
Epfspjcmv,  \ 
A^jCAzrone.  ColLy 


} Bran. 


WarcA^Cef  l Efllcxi. 

\uAthy  yrrojzfj 7/^*5. 

e%rerfrJz^m/xtDtLS . 
'UitlosG  dimdfji^ 
C7idvs//er/?v/j7tb 
. Stcu'cTi.  cgILs. 


ConyiresscA  ompt^ 

(rf  'eJ7Ao.3prrm  . 

Tcrmirta/yort'  of 
'I  aZGurono  c^7Ms  ctZ 
lcoiiiiTtencent£77f  of  Germ. 

iAbsorpZiye  ^ sec7'AX*f\ 
[op/ffr^ZCLi/rG'^  I 

P(AUTtula>  SIviaXiL,  I 

/SxMitellf/jrv,  / 

J^Joi'igaCojdL  cxdJs  of 

A ^CAJLtC^UAAJIl^^ 

^RcfoLinijCrr/cfrt/ 
cf  JRmoivuXcju,  ^ 

i^sCcz,  crcco.CbiA.wu^ 
l^.nro,(opp  enclosfrJjg 
1 boTJzEtbclok^peyni 
\anfl  Geonv. 

TLcuticle', 

Ttco.tJ  Sfteceffb, 

EucHclCy  Cafv 


E.  Endosperm. 

G.  Germ. 

Longitudimal  Section  through  a Grain  of  Wheat. 

Ma^jn/fLcAi  ayboLA  aC dfxAjrictyCf''S . 


256 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


410.  Transverse  Section  of  Wheat  Grain. — Examine  next  a transverse 
section  of  a grain  of  wheat  ; the  section,  below  figured,  Fig.  30,  was  cut  from 
a grain  of  Kubanka  wheat,  and  passes  through  the  germ. 


Fig.  30. — Transverse  Section  of  Grain  of  Wheat,  magnified  ISMiameters. 

On  examining  carefully  such  a section  as  that  shown,  the  pigment-con- 
taining cells  are  seen  in  a line  passing  completely  round  the  grain,  and  forming 
a thick  spot  of  colour  in  the  crease.  Notice  that  the  aleurone  ceUs  of  the 
bran  do  not  continue  round  the  germ.  Observe  also  as  much  as  possible 
of  the  structure  of  the  germ  itself,  and  the  relative  dimensions  and  positions 
of  germ  and  endosperm. 

Examine  the  same  section  in  the  next  place  with  the  1-inch  objective 
(Fig.  31).  The  outer  skins  of  the  bran  are  here  seen  more  plainly  ; the 


Fig.  31. — View  of  Crease  in  Grain  or  Wheat,  as  shown  in  a transverse 
section,  magnified  110  diameters. 

square  aleurone  or  cerealin  cells  are  also  plainly  visible.  Notice  that  near 
the  bottom  of  the  crease,  the  cells,  instead  of  being  in  single  line,  are  in 
double,  becoming  more  numerous  and  irregularly  arranged  as  the  bottom 
is  approached.  The  crease  distinctly  bifurcates  at  the  bottom  ; the  pig- 
ment layer  of  the  grain  becomes  considerably  enlarged,  and  its  section  is 
seen  at  the  middle  of  the  fork  as  a dark  yellow  spot  of  considerable  size. 
With  this  power  the  starch  granules  also  become  visible. 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  257 


411.  Section  Cutting  and  Mounting. — It  has  been  assumed  that,  for  the 
purposes  of  making  these  studies  and  sketches,  the  student  has  had  in  his 
possession  sections  that  he  has  purchased  ready  mounted.  He  will  probably 
at  this  stage  of  his  work  wish  to  prepare  and  mount  sections  of  his  own. 
Wheat  in  its  ordinary  state  is  too  brittle  to  permit  of  its  being  cut  in  thin 
sections.  In  the  first  place,  therefore,  soak  a few  grains  in  water  for  about 
twenty-four  hours  ; the  water  may  be  luke-warm,  say  at  a temperature  of 
80°  to  90°  F.  When  the  grains  have  become  moderately  soft,  sections  may 
be  cut  from  one  of  them.  For  this  purpose  a very  sharp  razor,  which  has 
been  ground  fiat  on  one  side,  is  generally  used.  Take  one  of  the  grains 
between  the  thumb  and  finger,  cut  off  one  end,  and  then  proceed  to  slice  off 
sections  as  thin  as  possible.  Some  little  practice  will  be  necessary  before 
they  can  be  successfully  cut  of  the  requisite  thinness. 

This  operation  is  rendered  easier  by  the  use  of  a section  cutting  table. 
This  little  piece  of  apparatus  consists  of  a plate  of  brass,  the  surface  of  which 
has  been  turned  perfectly  plane  ; in  the  centre  is  fixed  a tube  containing  a 
piston,  which  may  be  raised  by  means  of  a screw.  The  object  whose  section 
it  is  wished  to  procure  is  first  cast  into  a block  of  either  cocoa  butter  or  solid 
paraffin.  In  either  case  the  temperature  of  these  must  only  just  be  raised 
to  the  melting  point.  This  block  of  solid  paraffin  or  other  substance  is  next 
trimmed  down  so  as  to  go  into  the  tube  of  the  section  cutting  table.  Adjust 
the  screw  at  the  bottom  so  that  the  grain  is  in  about  the  right  position,  then 
draw  the  razor  across  the  top  of  the  tube  and  cut  off  the  upper  part  of  the 
grain  ; screw  up  the  piston  at  the  bottom  of  the  tube  very  slightly,  and  cut 
off  a section  by  again  drawing  the  razor  across  the  plane  surface  of  the  table. 
In  this  manner  thin  sections  may  be  cut  with  comparative  ease.  Having 
thus  obtained  the  sections,  wash  them  in  a little  spirits  of  wine  and  transfer 
to  a slide.  If  it  is  only  wished  to  examine  them  without  this  being  pre- 
served, they  may  be  mounted  in  a mixture  of  water  and  glycerin  in  equal 
volumes,  protected  with  a cover  slip,  and  at  once  placed  under  the  micro- 
scope. When,  however,  it  is  wished  to  make  a permanent  mount,  they 
may  be  embedded  in  glycerin  jelly  (Deane’s  medium).  Having  washed  and 
prepared  a section,  and  also  the  slip  and  cover,  place  a very  little  of  the  gly- 
cerin jelly  on  the  slide,  warm  very  gently,  and  the  jelly  becomes  liquid. 
Place  the  section  carefully  in  the  liquid  medium,  taking  care  that  it  is  tho- 
roughly immersed.  Remove  all  air  bubbles,  place  on  the  cover  as  carefully 
as  possible,  gently  squeeze  out  any  superfluous  medium,  and  allow  to  cool. 
The  jelly  will  then  again  become  solid.  Clean  the  edge  of  the  cover  glass, 
and  coat  round  with  asphalt  varnish. 

412.  The  Germ. — The  appearance  and  general  characteristics  of  the 
germ  itself  should  now  be  carefully  studied  ; for  this  purpose  use  the  1-inch 
objective. 

In  Plate  VI.  the  germ  is  shown  very  distinctly,  and  the  whole  of  its  parts 
named  and  indicated  by  reference  marks.  This  should  be  carefully  studied. 
Notice  that  the  aleurone  cells  of  the  bran  terminate  at  the  junction  of  the 
endosperm  and  germ,  and  only  the  “ testa  ” or  envelope  of  the  true  seed 
encloses  the  embryo.  The  “ plumule  ” is  that  part  of  the  young  plant  which 
penetrates  to  the  surface  during  growth,  and  then  constitutes  the  growing 
stem  and  leaves  of  the  plant.  It  consists  of  four  rudimentary  leaves  en- 
closed within  the  plumule  sheath.  The  radicle,  or  rootlet,  on  commencing 
its  growth,  forces  its  way  downward  into  the  earth.  The  germ  constitutes 
about  2-0  per  cent,  of  the  whole  grain,  while  its  enclosing  membrane  is  stated 
by  Mege  Mouries  to  amount  to  as  much  as  3-0  per  cent. 

The  nature  of  the  other  portions  of  the  germ  had  best  be  described  when 
dealing  with  their  functions  in  connexion  with  the  act  of  germination  (para- 
graph 418). 


258 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


413.  Endosperm  and  Bran. — ^Attention  must  next  be  directed  to  the 
structure  of  the  endosperm  and  the  branny  coatings  by  which  it  is  enveloped. 
For  this  purpose  a very  thin  section  should  be  selected  and  then  examined 
under  the  |-inch  objective. 

The  bran  of  wheat  is  divided  into  the  outer  envelopes  of  the  grain  and 
those  of  the  seed  proper.  Following  these  in  the  order  of  the  letters  given 
in  Fig.  32  : — 

a — is  the  outer  “ epidermis/"  or  “ cuticle.""  According  to  Mege  Mouries 
this  constitutes  0*5  per  cent,  by  weight  of  the  whole  grain. 

h — is  the  “ epicarp/"  and  amounts  to  about  1*0  per  cent,  of  the  grain. 

c — is  the  last  of  the  outer  series  of  the  envelopes  of  the  grain,  and  is 
known  as  the  “ endocarp.""  It  is  remarkable  for  the  well-defined  round  cells 
of  which  it  is  composed.  The  endocarp  amounts  to  1*5  per  cent,  of  the 
grain. 

d — is  the  first  of  the  envelopes  of  the  seed  proper  ; it  is  that  to  which 
reference  has  already  been  made  as  the  “ testa  "";  it  has  also  received  the 
name  of  “ episperm.""  The  colouring  matter  of  the  bran  occurs  principally 
in  the  episperm. 

e — is  a thin  membrane  lying  underneath  the  testa,  and  enveloping  the 
aleurone  cells.  This  membrane  and  the  testa  together  form  2 per  cent,  of 
the  grain. 

/ — is  the  layer  of  “ aleurone  ""  cells,  so  called  from  the  protein  of  that 
name  which  they  contain.  As  may  be  seen  from  the  figure,  the  cells  are 


Fig.  32. — Longitudinal  Section  through  Bran  and  Portion  of  Endosperm 
OF  Grain  of  Wheat,  magnified  440  diameters. 


almost  square  in  outline  ; one  is  at  times  replaced  by  two  lesser  ones,  as 
occurs  immediately  above  the  cell  /.  Notice  particularly  that  this  layer 
does,  not  envelop  the  germ,  but  only  encloses  the  endosperm. 

g — represents  the  layer  of  parenchymatous  cellulose  by  which  the  in- 
terior of  the  endosperm  is  divided  up  into  a number  of  cells  of  comparatively 
large  size,  these  in  turn  being  filled  with  starch  granules,  and  embedded  in 
gluten. 

h — shows  the  “ hilum  ""  of  an  individual  starch  granule. 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  259 


In  order  to  complete  the  investigations  of  the  appearance,  when  viewed 
under  the  microscope,  of  the  various  coatings  of  the  wheat  grain,  it  is  not 
only  necessary  to  examine  these  skins  in  section,  but  also,  so  far  as  possible, 
as  seen  on  the  flat.  The  bran  of  wheat  can  be  split  up  with  comparative 
ease  into  three  layers,  which  can  be  successively  peeled  off  from  the  endo- 
sperm. The  first  of  these  consists  of  the  epidermis,  or  cuticle,  and  also 
epicarp.  Following  these  are  the  endocarp  and  episperm,  which  usually 
peel  off  together.  The  inner  and  last  skin  consists  of  that  containing  the 
cerealin  cells. 

Take  a few  grains  of  soft  red  wheat  and  soak  them  for  a few  hours  in 
warm  water  ; when  they  are  sufficiently  softened,  take  one,  and  mth  a fine 
pair  of  forceps  strip  off  the  outer  skin  and  place  it  in  a watch  glass.  When 
the  whole  of  the  outer  skin  has  thus  been  removed,  carefully  strip  off  the 
middle  layer  in  the  same  manner,  and  also  reserve  it  for  examination.  The 
division  of  the  inner  layer  from  the  endosperm  is  often  only  accomplished 
with  difficulty  ; in  case  they  do  not  separate  well,  let  the  grain  soak  some 
time  longer. 

Next  proceed  to  examine  these  several  coatings.  Mount  each  on  a slide 
in  a drop  of  water  (or  preferably,  when  wished  to  examine  the  mount  for 
some  time,  in  a drop  of  glycerin),  so  that  it  is  practically  freed  from  bubbles, 
and  lying  flat  and  without  creases.  Put  on  a glass  cover  and  press  gently 
down.  Examine  with  either  a quarter  or  eighth-of-an-inch  objective. 


Fig.  33. — Outer  Layer  of  the  Bran  of  Wheat,  magnified  250  diameters. 
Observe  in  the  outer  layer  that  it  consists  of  a series  of  cells,  some  four 
to  six  times  long  as  broad,  and  arranged  longitudinally  in  the  direction  of 
the  length  of  the  grain.  A portion  of  the  outer  layer  is  shown  in  Fig.  33. 
Notice  at  the  one  end  (of  the  actual  section,  not  the  figure)  the  beard  of  the 
grain,  and  note  particularly  the  attachment  of  each  hair  to  the  skin  (the 
root).  Observe  also  the  canal  extending  about  half  the  length  of  the  hair. 
Fig.  34  is  a drawing  of  such  hairs. 


Fig.  34. — Beard  of  Grain  of  Wheat. 


260 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Next  observe  the  appearance  of  the  second  layer  of  skin  that  has  been 
detached  ; this  is  shown  in  Fig.  35. 


Fig.  35. — Middle  Layer  of  the  Bran  of  Wheat,  magnified  250  diameters. 

In  this  will  be  seen  two  layers  of  cells  that  are  not  both  in  focus^at  the 
same  time,  the  one  layer  being,  in  fact,  underneath  the  other.  There  are  in 
the  first  place  a series  of  long  cells  arranged  transversely  to  the  longitudinal 
section  of  bran  shown  in  Fig.  32,  where  they  are  marked  c.  Because  Ahey 
are  thus  arranged  around  the  grain  of  wheat  they  are  frequently  termed 
“ girdle  ''  cells.  The  great  difference  between  looking  at  the  same  thing  in 
one  direction  and  then  in  another  is  strongly  exemplified  in  this  study  of 
these  particular  cells  in  plan  and  in  section.  An  instructive  lesson  may  be 
gained  by  comparing  the  section  illustrated  in  Fig.  32  with  a similar  section 
cut  transversely  instead  of  longitudinally.  Such  a section  is  given  latter  in 
the  series.  The  colour-containing  cells  underlie  those  to  which  reference 
has  just  been  made. 

In  the  next  place  examine  the  inner,  or  aleurone  cell,  layer  of  the  bran. 


Fig.  3G.— Inner  or  Aleurone  Layer  of  the  Bran  of  Wheat,  magnified  440 

diameters. 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  261 


The  aleurone  or  cerealin  cells  of  the  bran  are  often  referred  to  as  being 
cubical ; that  this,  however,  is  not  the  fact  is  well  shown  in  Fig.  36.  They 
certainly  have  a square  or  rectangular  outline  when  seen  in  section,  whether 
longitudinal  or  transverse,  but  the  skin,  viewed  on  the  flat  surface,  shows 
that  the  cells  are  irregular  in  outline,  each  accommodating  its  contour  to 
that  of  those  surrounding. 

There  follows  a sketch  of  the  transverse  section  through  the  bran  of 
wheat  ; this  should  be  carefully  compared  with  the  longitudinal  section. 
Fig.  32. 


Fig.  37. — Transverse  Section  through  Bran  of  Wheat,  magnified  250 

diameters. 

The  actual  section  from  which  this  drawing  has  been  made  is  not  so  good  a 
one  as  the  longitudinal  section,  from  which  Fig.  32  was  drawn.  Viewed 
with  a moderately  high  power  it  is  difficult  to  get  very  much  of  the  thickness 
of  the  section  in  focus  at  the  same  time  ; still  sufficient  is  noticed,  on  careful 
observation,  to  show  the  general  structure  of  the  bran.  The  outline  of  the 
aleurone  cells  is  more  irregular  than  was  the  case  in  the  longitudinal  section  ; 
they  are  also  noticed  to  be,  in  several  instances,  overlapping  each  other. 
Looking  at  the  cells  of  the  middle  skin  of  the  bran,  they  are  seen  to  be  of 
considerable  length,  justifying  the  remarks  made  about  them  when  studying 
their  appearance  as  seen  on  the  flat.  While,  however,  these  middle  cells 
are  seen  lengthwise,  it  follows  of  necessity  that  the  ends  of  the  cells  of  the 
outer  skin  must  be  presented  to  the  eye.  This  sketch,  taken  with  the  others, 
gives  a tolerably  complete  idea  of  the  microscopical  structure  of  a grain  of 
wheat. 

A careful  study  of  these  sections  of  the  wheat  grain  and  of  the  various 
layers  into  which  the  bran  can  be  divided  should  give  the  miller  in  particular 
a clearer  and  more  real  idea  than  he  can  otherwise  have  of  the  nature  of 
these  outer  integuments  of  the  wheat  grain,  which  it  should  be  his  object  to 
remove.  The  study  should  not  merely  be  confined  to  the  drawings  given 
in  this  work,  but  should  extend  to  the  actual  slides  themselves  under  the 
microscope. 

414.  Bran  Cellulose. — ^The  bran  of  wheat  consists  largely,  as  is  well- 
known,  of  cellulose  or  woody  fibre,  together  with  a considerable  proportion 
of  soluble  albuminous  matter.  Cellulose  may  be  obtained  in  a fairly  pure 
state  by  alternate  treatment  with  hot  dilute  solutions  of  acid  and  alkali. 
The  actual  structure  of  the  cellulose  of  the  different  layers  of  the  bran  pos- 
sesses considerable  interest,  and  may  be  studied  in  the  following  manner  : 
Strip  off  the  different  layers  of  skin  as  before  directed,  put  pieces  of  each  in  a 
separate  test-tube,  and  first  digest  for  an  hour  with  dilute  sulphuric  acid  ; 
pour  ofl  the  acid,  and  digest  with  caustic  soda  solution  for  another  hour. 
-Make  up  solutions  of  1 part  respectively  of  acid  and£alkali,  and  20  parts  of 


262 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


water.  Wash  the  resulting  cellulose,  and  mount  carefully  on  a glass  slide  ; 
examine  under  the  microscope. 


Fig.  38. — Cellulose  of  Outer  Skin  of  Bran,  magnified  250  diameters. 

This  is  rendered  almost  transparent,  and  presents  no  striking  differences 
in  structure  from  the  original  skin. 


Fig.  39. — Cellulose  of  Middle  Skin  of  Bran,  magnified  250  diameters. 

In  this  again  the  resemblance  to  the  skin  before  treatment  is  very  notice- 
able. One  special  point  of  interest  occurs  in  this  drawing  ; the  two  layers, 
of  cells  to  which  reference  was  made  when  previously  speaking  of  the  appear- 
ance of  this  layer  have  become  separated.  The  upper  cells  extend  over  the 
whole  field,  wliile  the  lower  or  pigment  layer  is  stripped  from  the  one  portion 
Tlie  result  is  that  the  distinction  between  the  two  is  seen  very  clearly. 

As  tlie  aleurone  layer  or  inner  skin  of  the  bran  contains  so  large  a quan- 
titv  of  protein  matter,  it  will  readily  be  imagined  that  treatment  with  alkali 
will  cause  considerable  difference  in  its  appearance. 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  263 


Fig.  40. — Cellulose  of  Aleueone  Layer  of  Bean,  with  portion  of  protein] 
remaining,  magnified  440  diameters. 

In  Fig.  40  such  a specimen  is  shown  ; it  will  be  noticed  that  a portion 
only  of  the  protein  remains,  the  greater  part  having  been  removed  by  the 
action  of  the  caustic  soda. 


Fig.  41. — Cellulose  of  Aleueone  Layer  of  Bran,  with  only  the  slightest  trace 
of  protein  still  remaining  in  some  of  the  cells,  magnified  440  diameters. 

This  figure  shows  in  most  striking  fashion  how  small  a proportion  of  the 
interior  layer  consists  actually  of  cellulose.  Reviewing  the  whole  three 
layers,  one  finds  that  the  outer  one  is  largely  composed  of  cellulose,  and 
consequently  is  condemned  as  an  article  of  human  food.  The  middle  layer 
contains  less  cellulose,  but  contains  a higher  proportion  of  colouring  matter. 
The  proportion  of  cellulose  in  the  inner  layer  is  still  less,  but  the  amount  of 
protein  is  high.  This  protein  body  is  injurious  to  the  flour,  inasmuch  as  it 
exerts  considerable  action  on  broken  starch  granules.  There  are  therefore 
cogent  reasons  for  the  non-admission  of  any  part  of  the  bran  into  the  flour. 

415.  Cellulose  of  Endosperm. — On  taking  a grain  of  wheat  and  carefully 
cutting  off  the  bran  so  as  bo  have  a piece  of  the  endosperm  only,  and  treating 


264 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


this  interior  portion  of  the  grain  with  acid  and  alkali,  a trace  of  cellulose  is 
obtained  which  shows  no  distinctive  organisation  under  the  microscope. 
The  student  will  do  well  to  verify  this  fact  for  himself.  Let  him  also  treat 
small  quantities  of  different  varieties  of  flour  in  a similar  fashion,  and  exam- 
ine the  remaining  cellulose.  Such  an  inspection  is  calculated  to  teach 
much  concerning  the  success  of  the  operation  of  milling.  He  will  be  able  to 
see  whether  or  not  the  number  of  small  particles  of  bran  in  the  flour  is  large. 
He  will  also  learn  whether  or  not  the  bran  itself  is  intact,  or  whether  portions 
of  one  or  other  of  the  surfaces  have  been  removed  and  ground  up  into  the 
flour. 

Physiology  of  Grain  Life. 

416.  Protoplasm. — In  explaining  the  nature  of  yeast,  Chapter  IX., 
reference  has  already  been  made  to  the  fact  that  the  interior  of  the  cells  is 
filled  with  “ protoplasm,"'  and  that  this  material  is  the  “ ultimate  form  of 
organic  matter  of  which  the  cells  of  plants  and  animals  are  composed."’ 
Protoplasm  has  also  been  defined  as  the  “ physical  basis  of  life,""  and  for 
that  reason  merits  in  this  place  some  little  examination.  Yeast  may  be 
viewed  as  an  unicellular  plant,  whereas  wheat  and  the  higher  plants  generally 
are  multicellular  in  nature,  so  that  yeast  serves  as  an  introduction  to  their 
study.  From  what  has  been  already  described  of  the  life-history  of  yeast, 
the  following  conclusions  as  to  the  nature  of  its  protoplasm  may  be  drawn  : 
First,  that  protoplasm  is  the  seat  of  those  chemical  changes  which  are  in- 
separable from  the  life  of  the  organism.  Such  chemical  changes,  collectively, 
are  termed  the  metabolism  of  the  organism.  Those  processes  which  go  to  the 
building  up  of  more  complex  chemical  compounds  are  termed  constructive 
metabolic  processes,  while  those  in  which  complex  compounds  are  broken  down 
into  simpler  compounds  or  elements  are  termed  destructive  metabolic  processes 
In  the  most  recent  nomenclature,  the  term  metabolism  is  sometimes  re- 
stricted to  the  constructive  processes,  while  the  changes  of  destruction  or 
degeneration  are  referred  to  as  processes  of  katabolism.  Vines  classifies 
the  fundamental  properties  of  the  protoplasm  of  the  yeast  plant  as  follows  : — 

“I.  It  is  absorptive,  in  that  it  is  capable  of  taking  up  into  itseK  the 
substances  which  constitute  its  food. 

“2.  It  is  metabolic,  in  that  it  is  capable  of  building  up  from  the  relatively 
simple  chemical  molecules  of  its  food  the  complex  chemical  mole- 
cules of  the  organic  substances  present  in  the  cell  ; and  in  that 
it  is  capable  of  decomposing  the  complex  molecules  of  these 
substances  into  others  of  simpler  composition. 

“3.  It  is  excretory,  in  that  it  gives  off  certain  of  the  products  of  its  des- 
tructive metabolism. 

“4.  It  is  reproductive,  in  that  portions  of  it  can  become  separate  from 
the  remainder,  and  lead  an  independent  existence  as  distinct 
individuals."" 

The  protoplasm  of  certain  more  highly  organised  unicellular  plants  have, 
in  addition,  other  distinct  properties,  such  as  contractibility , irritability,  etc. 
In  the  lower  multicellular  plants  all  the  cells  appear  to  be  exactly  alike,  but 
in  most  the  constituent  cells  vary  and  have  special  functions  allotted  to 
them  : such  groups  or  arrangements  of  cells  constitute  what  is  known  as  an 
organ.  Thus,  certain  cells  are  absorptive  in  their  nature,  while  others  are 
excretory  : others,  again,  are  charged  with  the  functions  of  reproduction, 
and  these  are  known  as  the  reproductory  organs.  The  seed  or  grain  of 
wheat  is  one  of  the  most  important  among  these  latter,  and  it  is  only  such 
other  functions  of  the  plant  as  are  directly  associated  with  seed  life  that  can 
be  touched  on  in  this  place. 

Like  other  parts  of  plants,  the  seed  is  built  up  of  parenchymatous  cells 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  265 


containing  modified  protoplasm,  wiiich  consists  of  a series  of  meshes  or 
network  enclosing  within  them,  in  the  ripe  seed,  grains  of  starch.  The 
network  portion  is  composed  of  proteins,  and  of  these  an  exhaustive  descrip- 
tion has  already  been  given.  The  insoluble  proteins  constitute  what  Reinke 
named  the  plastin  of  the  cell,  while  the  more  soluble  portions  are  the  globulins 
and  peptones  ; of  which  latter,  seeds  usually  contain  considerable  quantities. 
The  plastin  is  probably  the  organised  protoplasm  of  the  cell,  while  the  globu- 
lins and  peptones  are  unorganised  or  dead  protoplasm.  The  higher  plants, 
such  as  the  cereals,  contain  in  certain  of  their  cells  differentiated  proto- 
plasmic bodies,  which  may  contain  colouring  matter,  in  which  case  they  are 
knovTi  as  chlorophyll-  or  etiolin-corpuscles  ; or  they  may  be  colourless,  in 
which  case  they  are  starch-forming  corpuscles  or  amyloplasts. 

417.  Constructive  Metabolism  of  Plants. — ^The  roots  serve  as  the  absorb- 
ing medium  through  which  the  plant  obtains  water  and  substances  which 
may  be  in  solution  in  water.  From  the  atmosphere  plants  absorb  carbon 
dioxide.  Much  of  the  oxygen  of  this  carbon  dioxide  is  returned  to  the  atmo- 
sphere in  the  free  state,  the  carbon  being  used  in  the  constructive  metabolism 
of  the  plant.  In  addition  to  the  carbon  dioxide  and  water,  the  plant  has  at 
its  disposal  for  metabolic  purposes  salts  containing  nitrogen  and  sulphur. 

A most  important  point  in  the  study  of  metabolism  is  that  the  assimila- 
tion of  carbon  from  carbon  dioxide  is  eonfined  to  those  portions  of  plants 
which  contain  green  colouring  matter  (or  closely  allied  matter  to  be  subse- 
quently described).  Further,  the  decomposition  of  carbon  dioxide  can  only 
take  place  in  the  presence  of  light.  On  treating  green  leaves  of  plants  with 
alcohol,  the  green  colouring  matter  is  dissolved  out,  and  has  received  the 
name  of  chlorophyll.  Within  the  leaves  this  ehlorophyll  exists  in  cells  or 
corpuscles  known  as  chlorophyll-corpuscles,  the  chlorophyll  itself  having 
apparently  a similar  composition  to  other  protoplasm.  Etiolated  plants — 
that  is,  plants  grown  in  the  absence  of  light — contain  corpuscles  in  which 
the  colouring  matter  is  yellow,  not  green  ; this  matter  has  received  the 
name  of  eiiolin,  and  is  doubtless  closely  allied  to  chlorophyll  in  properties. 
On  exposure  to  light,  the  etiolin  corpuscles  absorb  carbon  dioxide  and  exhale 
oxygen,  the  etiolin  being  converted  into  chlorophyll.  Investigation  of  a 
most  eareful  and  exhaustive  nature  demonstrates  that  the  absorption  of  carbon 
dioxide  aned  exhalation  of  oxygen,  with  the  formation  de  novo  of  organic  matter  in 
plants,  is  ssentially  a function  of  chlorophyll  (including  etiolin),  and  cannot  occur 
in  its  absence. 

But  little  can  be  stated  positively  as  to  the  exact  nature  of  the  chemical 
changes  induced  by  chlorophyll,  but  they  may  be  summed  up  in  the  state- 
ment that  it  produces,  by  synthesis,  protein  matter.  The  first  step  is  pro- 
bably the  formation,  from  carbon,  hydrogen,  and  oxygen,  of  comparatively 
simple  substances,  such,  perhaps,  as  formic  aldehyde,  CH2O  (the  simplest 
possible  carbohydrate),  and  its  polymers.  (Glucose  and  other  of  the  higher 
carbohydrates  may  be  viewed  as  polymers  of  formic  aldehyde,  thus  6CH2O 
=C6Hi206,  glucose.)  The  next  upward  step  might  be  the  production  of 
nitrogenous  substances  of  the  amide  type  (asparagin,  etc.),  and  finally,  by 
further  synthesis,  the  still  more  complex  protein.  Differences  of  opinions 
exist  as  to  the  manner  in  which  starch  is  formed  by  the  plant — there  is  first 
the  observed  fact  that  the  chlorophyll-corpuscles  of  a growing  plant  exposed 
to  fight  contain  starch  grains,  and  that  these  disappear  during  darkness. 
Vines  is  of  opinion  that  “ the  starch  which  makes  its  appearance  in  the 
chlorophyll-corpuscles,  when  constructive  metabolism  is  in  active  operation, 
is  not  the  first  product  of  the  synthetic  processes,  but  only  an  indirect  pro- 
duct : protoplasm  is  the  substance  which  is  formed  in  the  chlorophyll- 
corpuscles,  and  it  is  only  in  consequence  of  the  decomposition  of  the  proto- 


266 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


plasm  formed  that  starch  is  produced.”  In  a paper  contributed  to  the 
Journal  of  the  Chemical  Society,  in  1893,  by  Brown  and  Morris,  these  chemist 
advance  the  view  that  cane  sugar  is  first  formed  as  an  up-grade  product  of 
constructive  metabolism,  and  that  the  starch  is  formed  within  the  chlorc- 
phyll-corpuscles  from  this  compound.  There  is  proof  that  protein  matter 
is  capable  of  being  so  decomposed  as  to  result  in  the  splitting  off  of  a carbo- 
liydrate  molecule  from  its  substance,  as  in  the  production,  for  example,  of 
the  cellulose  cell-wall  of  yeast  from  its  protoplasm.^  On  the  other  hand, 
Brown  and  Morris  have  shown  that  the  chloroplasts  of  the  leaf  can  form 
starch  when  fed  directly  with  cane-sugar  solution,  and  claim  that  “ both 
under  the  natural  conditions  of  assimilation  and  the  artificial  conditions  of 
nutrition  with  sugar  solutions,  the  chloro-plasts  form  their  included  starch 
from  antecedent  sugar.”  However,  in  whatever  manner  formed,  chlorophyll 
causes,  in  the  presence  of  light,  the  production  both  of  proteins  and  carbo- 
liydrates,  including  starch,  within  the  leaf.  The  final  process  of  constructive 
metabolism  is  the  conversion  of  dead  protein  matter  into  living  organised 
protoplasm  ; but  our  knowledge  of  the  difference  between  these  is  very 
slight.  Vines  points  out  “ that  the  primordial  utricle  of  dead  cells  readily 
allows  of  the  passage  into  it  and  through  it  of  substances  which  could  not 
enter  or  pass  through  it  in  life.  This  is  in  accordance  with  the  well-known 
fact  that  it  is  impossible  to  stain  living  protoplasm  ; it  is  when  protoplasm 
is  dead  that  colouring  matters  can  penetrate  into  it.” 

Having  traced  the  synthesis  of  protoplasm  and  other  organic  matter  in 
the  leaf,  the  next  problem  is  the  mode  of  their  translocation  or  transference 
to  other  parts  of  the  plant.  Brown  and  Morris  have  proved  the  existence 
in  leaves  of  a diastase,  which  they  term  leaf  diastase,  or  “ translocation 
diastase,”  from  its  functions  as  an  agent  in  the  translocation  of  the  chloro- 
phyll products.  They  show  that  by  the  agency  of  this  diastase  the  starch 
(which  during  darkness  disappears  from  the  chlorophyll  corpuscles  of  the 
leaves)  is  converted  into  maltose.  They  further  are  of  opinion  that  the 
cane-sugar  which  the  leaves  may  contain  is  converted  into  dextrose  and 
Isevulose.  Probably  also  the  proteins  are  changed  by  analogous  processes 
into  peptones,  and  from  these  into  amides,  in  which  form  the  nitrogenous 
organic  substances  are  most  likely  distributed  through  the  plant.  The 
diastase  and  proteolytic  enzymes,  then,  pour  into  the  various  vessels  of  the 
plant  a solution  of  maltose,  dextrose,  laevulose,  and  peptones  and  amides. 
These  are  carried  to  the  new  parts  of  plants  for  the  purpose  of  forming  buds, 
roots,  etc.,  and  to  the  seed  portion,  there  to  be  stored  u]d  as  provision  for 
the  young  plant  during  its  first  stages  of  growth,  and  before  able  to  obtain 
nutriment  by  the  action  of  its  own  chlorophyll. 

The  physical  structure  of  the  wheat  seed  or  grain  has  been  already  de- 
scribed, the  embryo  of  the  plant  being  at  the  lower  end,  near  where  the  seed 
is  attached  to  the  ear,  and  the  upper  portion  being  the  endosperm,  the  whole 
})eing  enclosed  witliin  the  cuticle  known  as  bran.  Of  the  formation  of  the 
seed  as  the  plant  grows,  we  cannot  here  speak  ; but  assuming  the  seed  to 
have  formed  its  outer  envelope,  it  before  ripening  is  found,  on  examination, 
to  be  full  of  a milky  looking  fluid,  which  consists  of  the  sap  which  is  being 
supplied  by  the  vessels  of  the  plant. 

Within  the  seed  a synthetical  process  proceeds,  by  which  is  caused  the 
formation  of  protein  matter  from  the  sugar  and  amides  supplied  by  the  sap. 
From  this  is  derived  the  starch  of  starchy  seeds,  while  the  residuum  of  the 
])rotein  forms  what  are  known  as  aleurone-grains.  Vines  points  out  that 
comparatively  little  is  known  of  the  manner  in  which  starch  is  formed  in 

^ Pavy,  in  some  investigations  of  the  chemical  pathology  of  diabetes,  shows  that 
glucose  may  be  formed  from  proteins  during  human  digestion. 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  267 


seeds,  but  it  is  assumed  that  it  is  produced  in  the  same  way  as  in  other  parts 
of  the  plant.  Schimper  has  observed  that  in  the  parts  of  the  plant  not 
exposed  to  light,  the  formation  of  starch  is  effected  by  certain  specialised 
portions  of  the  protoplasm,  which  are  termed  starch- forming  corpuscles  or 
amyloplasts.  These  amyloplasts  resemble  in  nature  the  chlorophyll  cor- 
puscles or  chloroplasts,  and  act  by  conversion  of  protoplasm,  from  which 
the  starch-molecule  is  cleaved  off  by  decom- 
position. They  differ,  in  that  amyloplasts  act 
in  the  absence  of  light,  and  can  only  commence 
the  production  of  starch  from  comparatively 
complex  substances,  whereas  chlorophyll  cor- 
puscles synthesise  this  body  from  simple 
inorganic  compounds.  The  grains  of  starch  as 
at  first  formed  are  very  minute,  but'  grow  by 
deposition  of  further  starchy  matter,  such 
growth  continuing  either  within  the  amyloplast, 
or  frequently  outside  it,  the  latter  being  the 
case  in  the  wheat  grain.  The  mark  on  the 
starch  corpuscle  known  as  the  hilum  indicates  the  point  of  first  growth  in 
an  externally  formed  starch  grain,  and  is  gradually  separated  from  the 
amyloplast  by  the  deposit  of  more  starch  in  stratified  layers,  finally  leaving 
the  hilum  at  the  far  end  of  the  longer  axis  of  the  ovoid  starch  corpuscle. 

After  the  separation  of  the  starch,  there  remains  behind  in  the  seed  a 
small  proportion  of  sugar  ; part  of  which  consists  of  sucrose,  and  is  probably 
an  up-grade  sugar,  and  the  remainder  of  glucose  or  allied  sugar  produced 
by  the  subsequent  degradation  of  the  cane  sugar.  In  some  seeds  the  non- 
nitrogenous  matter  is  stored  up  as  oil  instead  of  starch — comparatively 
little  fatty  matter  is  present,  however,  in  wheat,  except  in  the  embryo 
itself. 


Fig.  42. — Group  of  Amylo- 
plasts. 


The  residual  matter  of  the  protoplasm,  after  the  separation  of  starch, 
is  stored  up  in  the  form  of  small  granules,  known  as  aleurone-grains.  These 
form  the  matrix  in  which  the  starch  grains  are  imbedded,  and  constitute 
the  protein  matter  of  the  endosperm.  The  series  of  cuboidal  cells  forming 
the  interior  layer  of  the  bran  are  also  filled  with  aleurone,  and  have  the 
name  aleurone-layer. 

During  the  growth  of  the  seed  from  the  milky  stage  before  referred  to, 
the  sap  continues  to  bring  supplies  of  maltose  and  nitrogenous  matters, 
which  undergo  the  constructive  metabolic  process  just  described  ; while 
under  the  influence  of  a ripening  sun  the  water  is  evaporated.  Gradually 
the  contents  of  the  seed  acquire  a firmer  consistency,  until  at  last  the  solid 
ripened  grain  of  wheat  is  produced.  In  this  condition  the  seed  is  in  a resting 
stage,  and  may  without  injury  be  subjected  to  desiccation  and  extremes  of 
temperature,  which  would  be  fatal  were  it  in  its  active  state.  Under  the 
influence  of  moisture  and  warmth,  active  changes  are  set  up  in  the  resting 
seed,  and  the  development  of  the  new  plant  commences. 


418.  Germination  of  Wheat  and  Barley. — In  order  to  understand  the 
phenomena  of  germination,  reference  should  at  this  stage  be  made  to  the 
section  of  the  wheat  germ  given  in  Plate  VI.  Although  in  the  resting  stage 
the  wheat  germ  contains  no  starch,  yet  within  twenty-four  hours  of  the 
seed  being  kept  in  a moist  state,  starch  is  found  in  abundance  within  the 
germ,  although  no  alteration  has  occurred  in  the  endosperm,  being  doubtless 
produced  by  dissociation  of  the  protoplasm  of  the  embryo.  This  is  followed 
by  an  elongation  of  the  radicle,  which  at  this  stage  contains  starch,  as  do 
also  the  leaves  of  the  plumule.  The  plumule,  with  its  further  growth,  first 
bursts  through  the  envelope,  and  finds  itself  in  contact  with  the  “ pericarp,’ 


268 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


or  outer  skin  of  the  grain  (enveloping  the  testa).  The  pericarp  is  next 
ruptured,  and  the  growth  of  the  plumule  proceeds  outside  the  grain.  On 
looking  at  the  figure  of  the  germ  (or,  still  better,  an  actual  section  under 
the  microscope),  there  viU  be  noticed  a series  of  elongated  cells,  constituting 
what  is  known  as  the  scutellum  : between  this  and  the  endosperm  is  a series 
of  cells  of  another  type,  arranged  with  their  longest  diameters  directed 
toward  the  endosperm  ; these  latter  form  what  is  called  the  absorptive  and 
secretive  epithelium.  At  the  time  when  the  radicle  breaks  through  its 
sheath,  the  cells  of  the  scutellum  lying  next  the  epithelium  begin  to  show 
starch  granules,  which  gradually  pervade  the  tissue  of  the  germ  : these  may 
be  taken  as  the  first  indication  of  the  passage  of  reserve  material  from  the 
endosperm  to  the  germ,  while  the  epithelium  is  regarded  as  the  absorptive 
contrivance  by  which  the  germ  thus  derives  sustenance  from  the  endosperm. 
The  first  visible  effect  on  the  endosperm  is  the  breaking  down  of  the  paren- 
chymatous cell-walls,  and  following  on  this  we  have  the  starch  corpuscles 
attacked.  There  are,  in  the  first  place,  minute  pittings  on  the  surface  of 
the  grains  of  starch,  which  increase  both  in  size  and  number  until  the  whole 
granule  is  completely  dissolved,  with  the  formation  of  maltose.  The  disso- 
lution and  assimilation  of  the  starch  of  the  endosperm  proceeds  gradually, 
the  more  remote  parts  being  last  to  suffer  attack.  The  protein  matter  of 
the  endosperm  is  at  the  same  time  converted  into  peptone,  and  probably 
amides,  by  a proteolytic  enzyme.  By  means  of  the  epithelium,  these  are 
transferred  to  the  growing  plant.  The  aleurone  cells  of  the  bran  show  no 
signs  of  change  until  the  reserve  starch  is  nearly  exhausted,  when  they  begin 
to  suffer  attack,  the  cell-walls  undergoing  dissolution.  Doubtless  the 
function  of  the  aleurone  cells  is  to  provide  protein  nutriment  for  the  plant 
at  a comparatively  late  stage  of  its  growth,  hence  the  highly  resistant  cell- 
walls.  In  their  researches  on  the  Germination  of  the  Gramince,  Brown  and 
Morris  demonstrate  that  the  epithelium  of  the  germ  secretes  diastase  during 
germination,  and  this  is  the  agent  of  transformation  of  the  contents  of  the 
endosperm.  They  also,  as  has  been  previously  mentioned,  have  shown 
that  the  diastase  of  germinating  grain  is  cyto-hydrolytic  (cellulose  dissolving) 
as  well  as  amylo-hydrolytic.  They  consider  the  former  action  to  be  due  to 
a distinct  and  separate  enzyme  from  diastase  proper,  and  that  it  also  is 
secreted  by  the  epithelium. 

Two  varieties  of  diastase  have  been  described  in  the  chapter  on  Enzymes, 
that  from  raw  grain,  and  ordinary  or  malt  diastase — the  former  is  probably 
identical  with  the  diastase  of  translocation,  by  which  the  starch  of  the 
chloroplasts  is  converted  into  sugar  ; while  the  latter  is  essentially  a diastase 
of  germination,  and  is  only  secreted  by  the  epithelium  of  the  scutellum. 
Tlie  power  to  liquefy  starch-paste  and  to  erode  starch -granules  always 
accompany  each  other,  and,  in  fact,  are  never  separable,  being  in  each  case 
functions  of  germination  diastase,  or  diastase  of  secretion.  Raw  grain  dias- 
tase is  produced  during  the  production  of  the  embryo  in  the  growing  and 
unripe  seed,  and  probably  then  acts  as  translocation  diastase  for  the  purpose 
of  preparing  nutritive  matter  for  the  developing  embryo.  The  i3ortion  of 
such  diastase  remaining  unused  in  the  ripe  seed  constitutes  the  diastase  of 
raw  or  ungerminated  grain. 

The  changes  just  described  are  those  which  wheat  undergoes  during 
germination,  and  occur  in  an  incipient  form  in  sprouted  or  “ growy  ''  wheat, 
in  wliich  tlie  diastase  of  secretion,  together  with  cytase,  will  have  more  or 
less  broken  down  the  parenchymatous  cell-walls,  and  also  possibly  have 
eroded  some  of  the  starch.  A useful  test  for  growy  wheat  is  to  examine 
tlie  germ  for  starch  ; if  any  such  granules  are  found  within  a section  when 
viewed  under  the  microscope,  it  may  safely  be  concluded  that  the  wheat  is 
unsound.  The  changes  to  which  malt  owes  its  properties  are  practically 


STRUCTURE  AND  PHYSIOLOGY  OF  THE  WHEAT  GRAIN.  269 


the  same  ; when  germination  has  proceeded  sufficiently  far,  its  further 
course  is  arrested  in  malting  by  kiln-drying  the  grain. 

Experimental  Work. 

419.  The  experimental  work  undertaken  in  connexion  with  the  subject- 
matter  of  this  chapter  should  consist  in  following  its  detailed  directions  for 
microscopic  examination  of  wheat. 


CHAPTER  XIV. 

CHEMICAL  COMPOSITION  OF  WHEAT. 

420.  Principal  Constituents  of  Cereals. — ^Proximate  analysis  of  tne 
cereal  grains  shows  that  they  contain  as  their  principal  constituents — fat, 
starch,  cellulose,  dextrin,  sucrose,  raffinose,  and  possibly  other  sugars ; 
soluble  protein  bodies,  consisting  of  albumin,  globulin,  and  proteose  ; in- 
soluble protein  bodies,  consisting  of  glutenin  and  gliadin,  which  together 
constitute  gluten  ; mineral  matters,  consisting  principally  of  potassium 
phosphate  and  water. 

The  following,  according  to  Bell,  is  the  average  composition  of  the  differ- 
ent members  of  the  cereal  family  : — • 


Wheat. 

Long- 

eared 

Carolina 

Constituents. 

English 

Maize. 

Eye. 

Eice 

Oats. 

without 

Winter. 

Spring. 

Barley. 

Husk. 

Fat 

1-48 

1*56 

1*03 

5*14 

3*58 

1*43 

0*19 

Starch 

63*71 

65*86 

63*51 

49*78 

64*66 

61*87 

77*66 

Cellulose 

3*03 

2*93 

7*28 

13*53 

1*86 

3*23 

Traces 

Sugar  (as  Cane) 

2*57 

2*24 

1*34 

2*36 

1*94 

4*30 

0*38 

Albumin,  etc.,  insolu- 1 
ble  in  alcohol  . . J 
Other  nitrogenous  1 

1 

10*70 

7*19 

8*18 

10*62 

9*67 

9*78 

7*94 

matter,  soluble  , 
in  alcohol  . . . . 1 

4*83 

4*40 

3*28 

4*05 

4*60 

5*09 

1*40 

Mineral  matter 

1*60 

1*74 

2*32 

2*66 

1*35 

1*85 

0*28 

Moisture 

12*08 

14*08 

13*06 

11*86 

12*34 

12*45 

12*15 

Total 

100*00 

100-00 

1 

100*00  100*00 

j 

100*00 

100*00 

100*00 

The  following  is  a series  of  later  analyses  by  Clifford  Ricliardson  of  the 
various  cereals.  It  will  be  noticed  that  the  water  runs  very  considerably 
lower  than  in  Bell’s  analyses,  a result  due  probably  to  the  greater  dryness 
of  the  American  climate. 


270 


CHEMICAL  COMPOSITION  OF  WHEAT. 
Averages  of  Detailed  Analyses  of  Cereals. 


271 


Wheat. 

' Barley. 

i Oats. 

Maize. 

Eye. 

No.  of  Analyses—. 

27 

14 

18 

21 

17 

Fat 

2-30 

2-67 

7-87 

5-54 

1-83 

Starch  . . 

67-88 

62-09 

56-91 

66-91 

61-87 

Cellulose. . 

1-90 

3-81 

1-29 

1-41 

1-47 

Sugar,  etc. 

Dextrin  and  Soluble 

3-50 

7-02 

6-07 

2-18 

7-57 

Starch.  . 

1 Proteins  insoluble  in  80  ^ 

230 

7-45 

3 55 

7-86 

3-47 

13-43 

2-18  i 

4-96 

4-75 

9-07 

per  cent,  alcohol  . . j 

Proteins  soluble  in  80] 
per  cent,  alcohol  . . j 

3-58 

3-66 

1-82 

5-84  1 

2-53 

Mineral  matter  . . 

1-84 

2-87 

2-22 

1-54 

2-06 

Moisture . . 

9-25 

6-47 

6-92 

9-34'  ' 

8-85 

100-00 

100-00 

100-00 

100-00 

100-00 

Ratio  of  Proteins  to  Car- 

bohydrates . . 

6-9 

6-5 

4-8 

7-6 

6-5 

In  a later  table  compiled  by  Hutchison,  the  general  composition  of  the 
cereals  is  given  as  follows  : — 


Constituents. 

Wheat. 

Barley. 

Oats, 

Hulled. 

Maize. 

Eye. 

Bice, 
no  Husk. 

Millet. 

Buck- 

wheat. 

Fat  . . 

1-7 

1-9 

8-1 

5-4 

2-3 

2-0 

3-9 

2-2 

Carbohydrates 

71-2 

69-5 

68-6 

68-9 

72-3 

76-8 

68-3 

61-3 

Cellulose 

2-2 

3-8 

1-3 

2-0 

2-1 

1-0 

2-9 

IM 

Proteins 

11-0 

10-1 

13-0 

9-7 

10-2 

7-2 

10-4 

10-2 

Mineral  matter 

1-9 

2-4 

2-1 

1-5 

2-1 

1-0 

2-2 

2-2 

Water 

12-0 

12-3 

6-9 

12-5 

11-0 

12-0 

12-3 

13-0 

421.  Banana  and  .Bread-fruit  Flours. — Attempts  have  been  made  to 
introduce  for  bread-making  purposes,  flours  prepared  from  the  banana  and 
bread-fruit.  Ballard  gives  the  following  as  their  mode  of  preparation  and 
composition  : — 

Banana  flour  is  prepared  from  the  unripe  fruit  of  Musa  saj)ientium 
(banana),  before  any  sugar  has  been  formed  therein.  The  peeled  fruit  is  cut 
transversely  in  round  slices,  dried,  powdered  and  sifted.  It  is  much  used 
in  certain  parts  of  the  tropics  in  the  form  of  porridge,  damper,  or  cake. 

Bread-fruit  flour  is  obtained  from  the  dried  unripe  fruit  of  Artocarpus 
incisa,  which  on  being  powdered  and  sifted,  yields  an  insipid  non-saccharine 
substance  used  as  food  by  the  Tahitians.  The  whole  fruit,  while  unripe, 
and  still  hard  through  its  starch  not  having  yet  been  converted  into  sugar, 
is  also  cooked  and  eaten  as  bread. 


272 


THE  TECHNOLOGY  OF  BREAD-MAKING. 
Composition. 


Banana 

Flour. 

Cape  Verde 
Bread-fruit  Four. 

Tahiti 

Bread-fruit  Flour. 

Water  . . 

1L90 

13-80 

14-30 

Proteins 

3-68 

2-61 

1-10 

Fat 

0-55 

0-85 

0-20 

Starch  . . 

79-82 

80-64 

83-85 

Cellulose 

1-95 

0-10 

0-15 

Ash 

2-10 

2-00 

0-40 

422.  Analyses  of  English  and  Foreign  Wheats. — ^The  analyses  embodied 
in  the  following  tables  are  selected  from  those  of  a number  of  wheats  analysed 
by  one  of  the  authors. 

Nos.  1-18  inclusive  w^ere  analysed  in  April,  1884  ; they  are,  except 
where  otherwise  mentioned,  1883  wheats. 

Nos.  19-27  inclusive  were  analysed  in  September,  1884,  and  are  all  1883^ 
wheats. 

Nos.  28-38  inclusive  were  analysed  in  November,  1884,  and  are  all  1884 
wheats. 

Reviewing  Nos.  1-18  as  a whole  it  may  be  remarked  that  the  moisture- 
is  high  ; as  might  be  expected  No.  18  heads  the  list.  The  soluble  extracts 
and  proteins  average  a somewhat  high  figure.  Taking  the  glutens  through- 
out these  are  lower  than  in  foreign  wdieats,  the  highest  figure  being  only 
8*21.  As  might  be  expected  the  Revitts  are  exceedingly  low  ; the  trace  of 
gluten  was  so  small  that  it  was  practically  impossible  to  recover  it  from  the 
bran.  Of  the  other  wheats.  Nos.  6 and  18  contain  the  lowest  quantities  of 
gluten. 

Samples  Nos.  19-27  call  for  no  special  remark,  representing  as  they  do 
the  class  of  wdieats  largely  used,  particularly  in  the  south  of  England,  in  the 
manufacture  of  flour.  It  is  interesting  to  note  the  variations  in  the  charac- 
ter of  the  same  variety  of  wheat  when  grown  in  different  localities,  and  under 
different  conditions.  Nos.  19  and  20  were  considered  by  sender,  a miller 
whose  flours  are  familiar  in  the  London  market,  to  be  exceptionally  fine 
samples  of  their  kind.  No.  21  is  of  interest  as  showing  the  composition  of 
a wlieat  damaged  during  growdh. 

The  English  wheats  of  the  harvest  of  1884  were  of  exceptionally  fine 
quality.  The  samples  given  were  selected  from  the  South  and  Western 
Counties.  Compared  with  the  series  of  English  and  Scotch  wdieats  of  1883 
liar  vest  the  moistures  run  much  lower,  the  average  being  13*55  against 
14*82  in  the  1883  wheats.  The  same  remark  applies  to  the  soluble  extract 
and  soluble  proteins.  The  average  of  the  glutens  is  also  somewhat  lower, 
being  6*40  against  6*87.  The  lowest  gluten  of  the  1883  series  was  5*00  in 
a Scotch  West  Country  wheat  ; this  had  also  the  highest  moisture  ; like 
the  Scotch  sample.  No.  38  in  the  new  series  is  grown  in  a damp  climate,  S. 
Devon,  and  yields  the  same  percentage  of  gluten.  The  highest  gluten,  8*61, 
is  yielded  by  a sample  of  white  wheat,  the  highest  of  the  1883  wheat  being 
a saipple  of  rough  chaff  grown  at  Didcot,  and  containing  8*21  of  gluten. 

Although  made  some  time  ago,  the  foregoing  analyses  are  still  fairly 
representative  of  tlie  general  composition  and  character  of  English  wheats. 

Many  new  varieties  of  wheat  have  now  been  introduced  and  have  dis- 
placed older  kinds  to  a very  great  extent.  “ Tiverson’s  ” and  “ Webb’s 
Stand-up  ” are  two  kinds  largely  grown  in  England  at  present. 


English  and  Scotch  Wheats. 


CHEMICAL  COMPOSITION  OF  WHEAT, 


273 


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274 


THE  TECHNOLOGY  OF  BREAD-MAKING, 


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(MCNCOCOCOCOCOCOCOCCiCOfO 


CHEMICAL  COMPOSITION  OF  WHEAT.  275 

French  wheats  are  being  grown  in  this  country  to  some  extent,  and  Hard 
Fife  wheat  in  a lesser  degree. 

The  foreign  wheats  are  naturally  more  varied  than  those  grovm  in  Eng- 
land and  Scotland.  The  Russian  wheats,  as  a class,  show  a higher  percent- 
age of  gluten  than  do  the  American.  Readers  may  make  an  interesting 
comparison  between  the  moistures  of  wheats  and  the  flours  produced  from 
them  ; the  comparison  may  also  be  extended  to  the  glutens. 

Indian  and  Persian  wheats  have  of  late  been  receiving  considerable 
attention  from  millers,  and  also  bakers  who  are  equally  interested  in  the 
wheat  supply  of  the  country.  The  Indian  wheats  are  characterised  as  a 
class  by  being  very  low  in  gluten,  and  this  is  accompanied  by  a low  per- 
centage of  moisture.  The  meals,  when  worked  up  with  water,  are  almost 
sandy  in  their  nature  ; it  is  only  after  standing  some  little  time  that  they 
begin  to  acquire  the  characteristic  ductility  of  wheaten  flours.  The  Persian 
wheats  are  decidedly  richer  in  gluten  than  the  Indian  ; this  holds  especially 
with  the  clean  Persian,  No.  68. 

No.  79  was  forwarded  by  the  L.C.  Porter  Milling  Co.,  of  Winona,  U.S.A., 
and  is  the  wheat  from  which  flours  Nos.  8 and  9 were  made.  The  higher 
line  of  figures  represents  the  results  obtained  on  allowing  the  dough  to  lie 
two  hours  before  extracting  the  gluten.  One  very  special  feature  of  this 
wheat,  and  also  the  flours  produced  from  it,  was  the  extreme  slowmess  with 
which  they  absorbed  water  and  became  thoroughly  softened  and  hydrated. 

Wheat  No.  80  was  grown  on  land  400  to  800  miles  west  of  Winnipeg, 
Manitoba.  The  comparatively  high  moisture,  soluble  extract,  and  proteins, 
are  indications  of  the  cold  climate  in  which  it  has  been  grown.  The  com- 
parison between  this  sample  and  No.  79  are  of  interest.  The  Canadian 
flours  referred  to  in  a subsequent  table  were  made  from  this  wheat. 

Since  these  analyses  were  made  considerable  changes  have  taken  place 
in  the  sources  of  British  wheat  supply.  Hardly  any  U.S.  spring  wheat  now 
comes  to  London.  What  does  come  is  described  as  No.  1 Hard  Duluth, 
No.  1 Northern  Duluth,  and  No.  2 Northern  Duluth.  These  wheats  have 
been  largely  replaced  by  the  No.  1 Hard  Manitoba  and  Nos.  1 to  6 Northern 
Manitoba.  Considerable  quantities  of  Durum  wheats  now  come  from 
U.S.A.  The  winter  Americans  are  now  sold  as  Red  Winter  (soft)  and  Hard 
Winter  (of  moderate  strength — the  wheat  from  which  the  Hard  Kansas 
flours  are  milled). 

Similarly  Saxonska  and  Kubanka  wheats  are  now  almost  unknown. 
Instead,  the  London  Market  is  supplied  with  Reval  and  Petersburg  wheats 
from  the  North  and  Black  Sea  and  Azoff,  and  Ghirka  and  Azima  from  the 
South. 

Plate  wheats  are  now  a most  important  source  of  supply. 

423.  Average  Composition  of  American  Wheats. — On  page  278  is  given 
the  average  composition  of  American  wheats,  according  to  Richardson, 
Chemist  to  the  United  States  Department  of  Agriculture.  The  carbohy- 
drates consist  of  the  starch,  dextrin,  and  sugar.  The  total  quantities  of 
proteins  are  given,  being  derived  from  the  percentage  of  nitrogen  found. 

424.  McDougall  Brothers’  Report  on  Indian  and  other  Wheats. — In  1892, 
these  gentlemen,  who  are  millers  and  bakers  of  London,  were  commissioned 
by  the  Secretary  of  State  for  India  to  grind  some  selected  samples  of  wheat, 
and  make  baking  tests  on  the  resultant  flours,  and  report  generally  on  their 
milling  and  baking  characteristics.  The  table  on  page  279  gives  the  results 
of  their  general  milling  tests.  Reference  is  made  to  the  baking  tests  in  a 
subsequent  chapter  on  flour  testing. 


Foreign  Wheats. 


276  THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Foreign  Wheats — Continued. 


CHEMICAL  COMPOSITION  OF  WHEAT. 


27’ 


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Average  Composition  of  American  Wheats, 


278  THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Milling  Tests — McDougall  Brothers. 


CHEMICAL  COMPOSITION  OF  WHEAT. 


27  £► 


Gluten 
by  Water 
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280 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


425.  Composition  of  Wheats,  Fleurent.— Fleurent  gives  the  following 
as  the  composition  of  certain  hard  wheats  examined  by  him,  viz.,  Russian, 
Algerian,  and  Canadian  wheat.  (The  last,  however,  contained  from  25  to 
30  per  cent,  of  soft  wheat.)  The  relative  weight  of  endosperm,  embryo, 
and  husk,  is  of  interest  : — 


Russian  Algerian 

Wheat.  Wheat. 

Average  weight  of  a grain  in  grams  0*030  ..  0*048 

Constitution,  per  cent.  : — 

Endosperm  . . . . . . 84*95  . . 84*99 

Embryo 2*00  . . 1*50 

Husk  13*05  . . 13*51 


Composition  of  the  Entire  Wheat. 


Water 

Nitrogenous  matters  : — 
Gluten 

Soluble  (Diastases,  etc.) 
Ligneous,  of  husk 
Starch 

Fatty  Matters 
Soluble  Carbohydrates  .* — 
Sugars 
Galactose  . . 

Of  husk  . . 

Cellulose 
Mineral  Matters 
Undetermined  and  loss 


. . 11*42 

. . 11*34 

. . 14*76 

. . 11*00 

. . 2*25 

1*82 

. . 1*92 

1*90 

. . 50*15 

. . 55*05 

. . 1*18 

1*93 

. . 2*14 

2*68 

. . 0*65 

. . 0*46 

1*76 

2*19 

. . 9*73 

. . 9*40 

1*56 

1*42 

. . 2*48 

. . 0*81 

Canadian  Goose 
Wheat. 

. 0*037 

. 84*94 

2*05 
. 13*01 


11*36 

10*88 

1*67 

1*91 

54*55 

2*70 

2*18 

0*75 

1*90 

9*21 

1*35 

1*54 


100*00  . . 100*00 


100*00 


The  gluten  of  the  Russian  wheat  was  found  to  contain  : gliadin,  46*45  ; 
glutenin,  37*89  ; congluten,  15*66  per  cent.  To  the  congluten,  Fleurent 
ascribes  the  tenacity  and  want  of  elasticity  of  the  flour  of  these  hard  wheats, 
w^hich  make  inferior  bread  (Com'ptes  Rend.  133,  944). 


426.  Durum  Wheat,  Norton. — ^This  variety  of  wheat,  Triticum  durum, 
is  largely  grown  near  the  Mediterranean,  and  in  Southern  Russia,  for  the 
manufacture  of  macaroni.  Of  recent  years  it  has  been  somewhat  exten- 
sively grown  in  America,  and  used  in  the  manufacture  of  bread  flours.  In 
consequence,  durum  wheat  has  attracted  considerable  attention,  not  only 
in  America,  but  also  from  European  importers  of  American  flours.  An 
extensive  investigation  of  its  properties  was  carried  out  at  the  South  Dakota 
Agricultural  Experiment  Station,  U.S.A.,  by  Norton,  with  the  following 
results.  Samples  of  the  wheat  were  grown  at  the  station  and  compared 
with  European  durum  wheat,  and  also  other  American  varieties  of  wheat. 

The  Grain.  The  durum  wheats  have  a very  large  kernel,  being  nearly 
twice  as  large  as  that  of  ordinary  bread  wheats.  The  grains  are  hard,  of 
an  amber  colour,  and  appear  almost  translucent. 

Composition  of  the  Wheat.  In  order  to  compare  the  general  composition 
of  durum  Avheats  with  the  bread  wheats,  a proximate  analysis  of  Kubanka, 
one  of  the  best  Russian  durum  wheats,  and  one  of  the  best  American  bread 
w'heats  (Blue  Stem,  Minnesota),  was  made.  The  results  of  these  analyses, 
together  with  the  mean  of  American  wheats  as  published  by  the  Bureau  of 
Chemistry  of  the  Department  of  Agriculture,  U.S.A.,  are  given  in  the  follow- 
ing table. 


CHEMICAL  COMPOSITION  OF  WHEAT. 


281 


1 

Constituents, 

Kubanka 

Durum 

Wheat. 

Minnesota 

Bread 

Wheat. 

Mean  of 
American 
Wheats, 

; 

Water  . . . . . . . . . . i 

9-32 

6-00 

10-62  f 

1 Mineral  Matter 

1-71 

2-46 

1-82  1 

Fat 

2-34 

2-49 

1-77 

Crude  Fibre  . . 

2-52 

3-35 

2-36 

Crude  Protein,  N x 5-7 

14-46 

13-21 

12-23 

Carbohydrates  other  than  Crude  Fibre 

69-65 

72-49 

71-18 

Sugar  . . 

I 3-26 

1-42 

— 

Dextrin 

j 1-25 

— 

— 

Invert  Sugar,  Soluble  Starch 

Nil 

Nil 

This  wheat  was  found  to  be  remarkably  sweet,  and  hence  the  sugar  was 
determined  with  as  shown,  a very  high  percentage.  The  dextrin  is  also 
extremely  high  as  compared  with  quoted  analyses  by  Stone,  in  which  0*27 
and  0*41  per  cent,  respectively  of  dextrin  were  found  in  whole  wheats.  In 
the  case  of  the  flours,  as  a result  of  indirect  indications,  macaroni  or  durum 
flours  are  estimated  to  contain  from  1 to  2 per  cent,  of  sucrose  as  against 
0*18  and  0*20  per  cent,  in  two  samples  analysed  by  Stone. 

Protein  Content  of  American  Crops.  In  American  durum  wheat  crops, 
there  is  an  increase  in  protein  matter  as  against  original  imported  seed.  The 
following  are  some  results  calculated  to  the  water-free  basis  : — 


Number  of 
Analyses. 

Protein,  N x 5-7 
per  cent. 

Imported  seed 

..  7 

15-73 

Crop  of  1901 

. . 31 

18-13 

„ 1902 

. . 32 

14-57 

„ 1903 

. . 45 

17-34 

The  year  1902  was  a very  unfavourable  one  for  durum  wheat. 

Durum  Flour.  A straight  flour  was  prepared  from  durum  wheats, 
apparently  of  the  1903  crop,  and  various  determinations  made  thereon. 

Colour.  The  durum  wheats  possess  a yeUow  colouring  principle  which 
is  also  found  in  the  flour,  which  is  in  consequence  of  a deep  yellow  tint 
expressed  on  the  Lovibond  tintometer  scale  by  0*25  yellow  + 0*17  orange. 
This  colouring  matter  is  soluble  in  alcohol  and  ether,  but  is  insoluble  in 
distilled  water.  It  is  somewhat  readily  soluble  in  dilute  alkalies,  and  is 
'discharged  from  solution  by  acids.  (It  is  probably  as  a result  of  a similar 
reaction  that  flour  is  stained  yellow  by  the  addition  of  sodium  carbonate.) 

Protein. — The  following  are  the  means  of  a number  of  determinations 
made  on  durum  flours  : — 


Crude  Protein  . . 

Wet  Gluten 
Dry 

Gliadin  . . 

„ of  total  Protein 


15-00  per  cent. 
53-77 
17-68 
7-87 
47-17 


The  gliadin  determinations  are  calculated  on  a water-free  basis. 

The  durum  flours  have  a large  gluten  content,  but  the  quality  is  not 
good,  usually  showing  very  poor  adhesive  qualities,  and  but  little  elasticity. 
These  are  properties  commonly  ascribed  to  lack  of  ghadin.  Though  all  the 
durum  flours  have  high  glutens  and  sugar  contents,  yet  the  bread  from  many 
of  the  poorer  durum  wheat  flours  neither  rises  during  the  fermentation  nor 
in  the  oven. 


282 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Bakers'  Tests.  On  being  subjected  to  a baker’s  sponging  test  in  which 
the  flour  is  made  into  a sponge,  allowed  to  ferment,  and  the  volume  read  off, 
the  volume  of  the  best  durum  flours  was  as  high  as  that  of  the  bread  wheat 
flours.  In  baking  tests,  durum  flour  becomes  more  sticky  than  bread  wheat 
flours ; also  if  the  doughs  are  a little  too  stiff  they  do  not  rise  properly,  and 
the  bread  is  heavy  and  of  poor  texture.  With  a sufficiency  of  water,  the 
volume,  weight,  and  texture  of  the  best  durum  wheat  breads  compare 
favourably  with  those  from  the  best  bread  wheats,  and  the  flavour  is  decidedly 
pleasing  {Jour.  Amer.  Chem.  Soc.,  1905,  922). 


427.  Voller  on  Wheats. — The  tables  on  pages  234-9,  headed  “Dictionary 
of  Wheat,”  are  taken  from  Voller ’s  excellent  work  on  “ Modern  Flour  Mil- 
ling.” They  are  particularly  valuable  as  a succinct  record  of  the  milling 
and  baking  characteristics  of  the  most  important  wheats  and  their  flours  to 
be  found  on  the  British  market.  Mr.  Voller  has  very  kindly  made  specially 
for  this  work  a number  of  corrections  and  additions  to  these  tables,  thus 
bringing  them  down  to  actual  date. 

Voller  also  gives  some  useful  rules  as  to  selection  of  wheats  for  different 
characters,  and  also  a table  of  mixtures  equivalent  to  certain  single  wheats, 
which  may  be  used  to  replace  the  latter  on  their  becoming  exhausted. 
Thus — 


For  largest  loaf,  use  good  Minnesota  or  Manitoba,  run  very  close  by  fine 
Saxonska,  Azima  or  Ghirka. 

For  whitest  flour,  use  good  White  English,  Oregon,  Australian,  or  Ros  Fe 
Plate,  with  choice  for  the  latter. 

For  sweetest  bread,  use  good  English  and  Manitoban  in  about  equal  parts. 
The  following  are  examples  of  replacing  mixtures,  but  are  not  intended  as 


exact  equivalents  in  any  sense  : — * 

Single  VV’^heats. 

2 American  Spring | 

2 Red  Winter  American  . . . | 

3 Manitoban  | 

1 Manitoban  

2 Australian  | 

2 California  (or  Walla)  . . . . | 
2 Red  Winter  American  . . . | 
2 Californian  or  Australian  | 

2 Mixed  Indian  | 

2 Bar-Russo  Plate | 


May  be  replaced  by 

1 Manitoban. 

1 Red  Winter  Kansas. 

1 Bahia  Plate. 

1 Ros  Fe  Plate. 

2 Saxonska. 

1 Ghirka. 

1 Ghirka,  Azima,  or  Ulka. 

1 Californian  or  Walla. 

1 C.W.  Kurrachee 
1 Australian. 

1 Chilian. 

1 Plate. 

1 Canadian  (Soft). 

1 White  Bombay. 

1 Walla. 

1 Australian. 

1 Bahia. 

1 Manitoban 

1 Calcutta,No.  2,or  Red  Kurrachee. 


428.  Chemical  Changes  during  the  Formation  and  Ripening  of  the  Wheat 
Grain,  Teller. — ^The  following  experiments  were  made  in  Arkansas,  U.S.A., 
1897.  Half  an  acre  of  growing  grain  was  purchased  early  in  May,  and  on 
the  22nd  instant,  when  the  wheat  was  past  blossoming,  and  the  grain  was 
set,  a portion  was  cut.  A further  portion  was  cut  on  each  successive  day, 

* The  best  substitutes  for  English  sorts  are  the  following : — Soft  Canadians,  and 
Winter  Americans,  Dantzic,  German,  French  and  Mild  Plates. 


CHEMICAL  COMPOSITION  OF  WHEAT. 


283 


till  forty-two  portions  in  all  were  obtained.  The  portions  ranged  in  weight 
from  80-90  pounds  at  the  commencement  to  about  50  pounds  at  the  close 
of  the  series.  Immediately  on  cutting  they  were  carefully  air-dried,  and 
then  stored  in  bundles  till  threshing  time.  The  summer  was  unusually  dry. 
The  wheat  was  threshed  and  cleaned  at  the  end  of  September.  Analyses 
were  then  made  on  samples  which  were  hand-picked  to  free  them  from  all 
foreign  matter. 

For  various  reasons  the  forty-two  samples  were  arranged  in  fourteen 
groups  of  three  each.  The  following  table  shows  the — 

Stage  of  Development  of  Wheat  when  Cut. 

Koman  numerals  indicate  number  of  the  group  of  three  cuttings  each. 
Figures  in  parenthesis  indicate  numbers  of  the  cuttings. 

I.  (1,  2,  3)  A little  past  blossom.  Grain  set. 

II.  (4,  5,  6)  Berries  one-half  to  full  length  of  ripe  grain. 

III.  (7,  8,  9)  Crushed  berries  exude  a thin  milky  liquid.  Lower 

leaves  beginning  to  die. 

IV.  (10,  11,  12)  Grain  well  in  milk. 

V.  (13,  14,  15)  Heads  and  kernels  well  developed.  Interior  of 

the  grain  a thin  dough. 

VI.  (16,  17,  18)  Grain  in  dough. 

VII.  (19,  20,  21)  Grain  in  stiff  dough.  Straw  becoming  yellow  at 

butt.  Grain  shells  a little  with  rough  handling. 

VIII.  (22,  23,  24)  Straw  in  field  much  yellowed  but  still  decidedly 
green. 

IX.  (25,  26,  27)  Grain  oozes  a thin  liquid  when  crushed  betAveen 
the  thumb  nails.  Contents  still  slightly  viscid.  .StraAv  still  a 
little  green. 

X.  (28,  29,  30)  Wheat  fit  to  cut  at  beginning  of  this  period.  Straw 
has  lost  all  its  green  colour  and  is  dark  purple  immediately 
below  the  heads.  Berry  nearly  dry.  May  be  crushed  between 
the  thumb  nails  but  without  contents  adhering  to  them. 

XI.  (31,  32,  33)  More  than  ripe.  Straw  bright  and  stands  up  well. 

XII.  (34,35,36) 

XIII.  (37,38,39) 

XIV.  (40,41,42) 

The  wheat  was  of  the  variety  known  as  the  Fulcaster.  It  is  a red, 
bearded,  wheat  which  is  extensively  grown  in  Arkansas. 


284 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


DICTIONARY  OF  WHEAT  (FOREIGN 


Wheat. 

Quality  of  Bread. 

Yield  ! 

Weight 

of 

Sort.  1 

i 

Colour. 

Structure. 

Taste. 

Strength. 

Colour. 

of  i 
Flour. 

Wheat 

per 

Bushel. 

AMERICA 
(UNITED  STATES). 

i 

Michgan  . . 

White 

Soft  or  mild 

Sweet 

Moderate 

Good 

68-72 

60-63 

Oregon 

White 

Mild 

Dry  insipid 

Low 

Fine 

70-74 ' 

1 

61-63 

Blue  Stem . . 

White 

Mild,  dry 

70-74 

61-63 

Walla  Walla 

White 

Dry  to  brittle 

Poor,  insipid 

Fair  to  good 

68-71 

60-62 

Californian  . . 

White 

>> 

99 

Good  to  fine 

68-72 

60-63 

Goose  or  Durum 

Yellow 

Very  hard 

Dry,  coarse 

Low  to  fair 

62-66 

60-62 

Wheat 

CANADIAN  (Soft) 

White 

Mild,  soft 

Sweet 

Fair 

Good  to  fine 

68-72 

60-63 

CHILIAN  . . . . 

W or  M 

Dry  to  hard 

Insipid 

Low 

68-73 

60-64 

ARGENTINE. 

Plate — Candeal  . . 

Yellow 

Hard,  flinty 

Coarse 

Fair  to  good 

Poor  to  fair 

62-66 

60-64 

„ Saldome  . . 

Yellow 

„ 

62-66 

60-64 

OCEANIA. 

Australian — V ict  or  - 

White 

Soft  to  dry 

Sweet 

Fair 

Good  to  flne 

70-74 

61-64 

ian  & New  S.  Wales 

South  and  West 

White 

,, 

,, 

99 

70-74 

61-64 

Australian 

New  Zealand 

White 

Soft,  mild 

99 

Low  to  fair 

Fine 

70-73 

61-64 

INDIA. 

Bombay  (Soft) 

White 

Mild,  dry,  or 
brittle 

Strong 

Fair  to  good 

Good  to  flne 

70-73 

62-64 

Delhi  

White 

„ 

„ 

70-73 

62-64 

Kurrachee  . . 

W or  M 

1 

Fair  to  good 

66-70 

60-64 

Calcutta 

W or  M 

66-70 

60-64 

GERMANY. 

Dantzic 

White 

Soft,  mild 

Sweet 

Fair 

Good  to  flne 

, 68-71 

60-63 

Konigsberg  . . 

White 

68-71 

60-63 

Rostock 

White 

68-71 

60-63 

RUSSIA. 

Taganrog  Cones  . . 

Yellow 

Hard,  flinty 

Dry,  coarse 

Low 

Low  to  fair 

62-66 

60-63 

Kubanka  Cones  . . 

Yellow 

Good  or  sweet 

Good 

Fair  to  good 

64-70 

60-63 

EGYPTIAN  . . . . 

White 

or 

mixed 

Mild  to  hard 

Dry,  coarse 

Low 

Low  to  fair 

64-72 

68-62 

ENGLAND. 

Talavera 

White 

Mild,  soft 

Sweet 

Low  to  fair 

Good  to  flne 

68-72 

60-64 

Chidham 

White 

■ 99 

68-72 

60-64 

Rough  Chaff.. 

White 

99 

99 

„ 

68-71 

i 60-64 

Webb’s  Challenge 

W’hite 

99 

68-71 

60-64 

Hallett’s  Victoria 

White 

„ 

68-71 

I 60-64 

Salvator 

White 

,, 

67-70 

, 60-63 

Essex  WTiite . . 

WTiite 

1 

” 

68-71 

1 

1 60-64 

CHEMICAL  COMPOSITION  OF  WHEAT. 


285 


raiTES  AND  ENGLISH). 


Impurities  Present. 

1 

Regular.  Occasional. 

Pro- 

bable 

0 

/o 

General  Remarks. 

Chaff,  screening, 

Dirt,  oats,  barley 

1-3 

Clean,  good  wheat.  Satisfactory  substitute  for 

seeds,  maize 

English. 

Chaff,  oats,  barley. 

Smut,  stone 

1-3 

Fine  handsome  grain.  Low  cleaning  loss.  High 

seeds 

flour  yield. 

„ „ „ 

Smut,  dirt,  stone 

1-3 

,,  ,,  ,,  ,,  ,, 

Chaff,  smut,  oats,  j 

Dirt,  stone 

1-4 

Yellow  tint  to  flour.  Fair  quality  as  2nd  class 

barley,  seeds 

white  wheat. 

Short  straws,  smut. 

Oats,  barley,  stone. 

1-5 

Invaluable  mixing  sort.  Useful  all-round  white. 

seeds,  screenings 

scented  seeds 

Maize,  chaff,  screen- 

Peas,  oats,  barley. 

1-4 

Low  flour  yield.  Washing  alone  can  tone  its 

ings 

dirt 

hardness.  Difficult  to  flnish. 

1-5 

A good  coloury  wheat  of  mild  character . 

Stone,  dirt,  seeds. 

Oats  and  barley 

2-6 

Variable  quality.  Well  worked  mills  a dead  white 

chaff 

flour.  Very  fine  in  grain. 

Oats,  barley,  seeds 

Dirt,  smut 

2-6 

Needs  careful  washing  and  milling.  Not  good 

flouring  wheat. 

2-6 

i » 

1 

Chaff,  screenings 

Oats,  barley,  seeds 

1-3 

Choice  colour  wheat.  Valuable  with  reds  as 

mixing. 

99  99 

1-3 

1 

„ „ „ 

1-3 

: 

Stones,  dirt,  gram. 

Oats,  barley 

3-6 

Variable.  Often  fine  quality,  but  purchases  need 

seeds 

close  watching.  Indians  all  need  washing. 

99  99  99 

,,  ,, 

3-6 

99  99  99  99  99 

99  99  99 

,,  ,, 

3-6 

Useful  blending  sorts.  Absorb  water  freely.  Fair 

colour. 

„ 

! 

3-6 

Chaff,  screenings. 

i Oats,  barley,  smut 

2-5 

Excellent  mild  w’orking  colour  wheat. 

dirt 

99  99  99 

,,  ,,  ,, 

2-5 

,.  ..  ,, 

! » - „ 

2-5 

Oats,  barley,  seeds. 

1 Smut,  dirt,  stone 

2-6 

Very  hard  to  mill.  ' Low  in  flour  yield. 

rye 

: „ 

1-5 

Strong  hard  grain.  Washes  to  advantage. 

Dirt,  stone,  seeds. 

1 Peas,  beans 

3-8 

Washing  absolutely  needed.  Colour  of  flour  dead 

barley 

white. 

Chaff,  screenings 

Seeds,  garlic,  smut. 

1-2 

Large  good  wheat  of  top  quality. 

dirt,  vetches 

,,  ,, 

1 ,,  ,, 

1-2 

Brilliant  handsome  quality.  Highest  colour  form. 

1-2 

1 9 

Very  reliable  and  a general  favourite. 

1-2 

Unexcelled  for  colour  when  well  grown. 

,,  ,,  ,, 

1-2 

Large,  but  hardly  fine  quality.  Too  coarse. 

” ” 

1 » 

, 1-2 

i 

Fine  medium  grain,  clear  skinned  and  white. 

286  THE  TECHNOLOGY  OF  BREAD-MAKING. 


DICTIONARY  OF  WHEAT  (FOREIGN) 


Wheat. 

Quality  of  Bread. 

Yield 

of 

Flour. 

Weight 
: of 

Wheat 
per 

Bushel. 

1 

Sort. 

Colour. 

Structure. 

Taste. 

Strength. 

Colour. 

ENGLAND — contd. 

Red  Lammas 

Red 

Mild,  soft 

Sweet  • 

Low  to  fair 

Good  to  fine 

67-70 

60-64 

Nursery 

Red 

67-70 

1 60-64 

Riddle’s  Imperial . . 

Red 

- 

! 

67-70 

1 60-64 

Browick 

Red 

Good 

67-70 

60-63 

Square  Head 

Red 

,, 

5, 

67-70 

60-63 

Square  Head’s  Mas- 

Red 

,, 

5, 

67-70 

60-63 

ter 

April  

Red 

,, 

5, 

Fair  to  good 

65-68 

60-62 

Blue  Cones  . . 

Red 

Dry  to  hard 

5, 

66-69 

60-63 

Rivetts  Cones 

Red 

” 

66-70 

60-63 

Golden  Drop 

Red 

Mild,  soft 

66-68 

60-63 

Prolific 

Red 

Good 

67-70 

60-64 

Windsor  Forest  . . 

Red 

- 

67-70 

60-64 

FIFE  (new  type). 

Red 

Firm  to  Hard 

Good 

„ 

68-72 

1 

60-66 

SCOTCH  . . . . 

R or  W 

” i 

„ 

67-70  1 

60-63 

IRISH  .. 

R or  W 

1 

” 

67-70 

60-63 

DICTIONARY  OF  WHEAT 


Wheat. 

Quality  of  Bread. 

Yield 

of 

Flour. 

Weight! 
of  1 

Sort. 

Colour. 

Structure. 

Taste. 

Strength. 

Colour. 

Wheat 

per 

Bushel 

! 

AMERICA 

(UNITED  STATES). 

No.  1 Hard  Spring 

Red 

Hard 

Sweet 

Full 

Good 

70-72 

60-65 

No.  1 Northern  ,, 

Red 

,, 

,, 

„ 

,, 

68-71 

58-64 

j 2 

Red 

Good  to  full 

67-70 

57-63 

No.  2 Chicago  ,, 

Red 

Good 

67-70 

57-62 

No.  3 Spring  ,, 

Red 

Fair  to  good 

Fair 

62-66 

56-60 

No.  1 Red  Winter 

Red 

Mild,  dry 

Fair 

Good  to 

70-73 

60-64 

(Choice) 

choice 

No.  2 Red  Winter 

Red 

Good 

68-72 

58-62 

Kansas  Winter 

Red 

Hard 

Fair  to  good 

67-71 

58-62 

(Hard) 

Western  Winter  . . 

Red 

Mild  or  hard 

66-70 

57-61  1 , 

! 1' 

CANADIAN. 

No.  1 MANITOBAN 

Red 

Hard 

Good  to  full 

Good 

70-73 

60-65 

No.  2 

Red 

Good 

>> 

68-71 

58-64 

No.  3 

1 

>> 

68-70 

58-62 

CHEMICAL  COMPOSITION  OF  WHEAT. 


287 


WHITES  AND  ENGLISH)— 


Impupjties  Present. 

General  Remarks. 

Pegular. 

Occasional. 

Pro- 

bable 

o/ 

/O 

Chaff,  screenings. 

Smut,  garlic,  seeds. 

1-3 

Safe  old-fashioned  sort.  Works  very  white.  i 

vetches 

dirt 

1-3 

Small  regular  grain.  Excellent  quality. 

1-3 

„ 

■ „ 

1-3 

Large  bright  red  wheat.  Average  working  sort. 

,,  ,, 

j ” 

1-3 

„ ,,  ,,  „ „ 

1-3 

1-3 

Thin  grain.  Not  of  highest  milling  quality. 

» >» 

^ ,,  ,,  ,, 

1-3 

In  good  repute  for  fine  taste  and  colour. 

,,  ;> 

t 5»  J> 

1-3 

Makes  weak,  coarse  grained  flour  of  dead  white 

’’  ” ” 

1-3 

colour. 

Rather  a low  class  among  the  native  reds. 

f 9 9 9 9 9 

1-3 

Good  standard  quality.  Liked  by  millers. 

„ 

1-3 

» 

\ 1 

! „ „ „ i 

Seeds  and  dirt 

1-2 

Valuable  type  grown  from  Manitoban  seed. 

1-3 

Like  much  of  the  English,  rather  too  soft  and  weak. 

” ” ” t 

1-3 

(FOREIGN  REDS). 


Impurities  Present. 

General  Remarks, 

Regular. 

Occasional. 

Pro- 

bable 

% 

Cockle,  seeds,  spelt. 

Peas,  barley  smut. 

1-3 

The  premier  strong  wheat.  Reliable  for  grade  and 

white  oats,  chaff. 

stone 

working  quality. 

maize 

1-3 

Nearly  equal  to  No.  I.  Hard  for  strength.  In  good 

2-5 

repute  amongst  millers. 

Less  reliable  than  No.  1 of  same  class.  Thinner, 

2-5 

with  more  waste. 

A safe  grade  of  moderate  strength.  Small  bright 

3-8 

wheat. 

Must  be  handled  with  caution  as  being  distinctly 

Cockle,  grass  seeds, 

Peas,  seeds,  garlic. 

1-3 

a risky  grade 

Should  be  long  berried  of  brilliant  quality.  Works 

oats,  maize 

stone,  barley 

mild  and  white. 

„ „ „ 

Stone,  garlic,  peas. 

2-4 

A safe  and  favourite  grade.  Dry  and  mild,  with- 

barley 

Stone,  peas,  barley 

2-4 

out  great  strength. 

Usually  clean  and  regular.  Of  hard  ricey  struc-  i 

„ 

Smut,  peas,  barley 

2-5 

ture.  Moderate  strength.  | 

An  off  grade — not  invariably  regular  in  quality,  j 

Cockle  & seeds,spelt. 

Peas,  dirt,  stone. 

1-3 

Fine  handsome  as  grain.  Larger,  but  hardly  as 

white  oats,  maize 

barley 

strong  as  Duluth  I. 

» 

2-4 

Good  as  a substitute  for  I.  Northern  Spring,  though 

2-4 

a trifle  weaker. 

Useful  as  a cheaper  substitute  for  No.  2 grade. 

288 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


DICTIONARY  OF  WHEAT 


Wheat. 

Quality  of  Bread. 

i ■ 

Yield 
of  i 

Weight 

of 

Wheat 

per 

Bushel. 

Sort. 

1 

Colour. 

Structure. 

Taste. 

Strength. 

1 

Colour. 

Flour. 

P 

CANADIAN.— co»f(Z. 

1 

! 

No.  4 MANITOBAN 

Red 

Hard 

Variable 

Low  to  fair 

Fair 

62-65  ! 

56-60 

(SometimesFrosted) 

Canadian  (Soft)  . . 

Red 

Soft  or  mild,dry 

Sweet 

Fair 

Good 

70-72  : 

60-62 

RUSSIAN. 

1 

Choice  Azima 

Red 

Hard  or  med. 
hard 

Dry,  strong 

Good  to  full 

Good 

68-72 

i 

60-65 

,,  Ghirka 

Red 

99  ^9 

Good 

,, 

68-72  ^ 

60-65 

Azima,  2nd  quality 

Red 

„ 

Fair  to  good 

Fair  to  good 

64-68  ; 

58-62 

Ghirka  ,,  „ 

Red 

64-68  ; 

58-62 

Azima  or  Ghirka, 
third  quality 

Red 

Soft  or  med. 
hard 

Fair 

Low,  uncer- 
tain 

60-65 1 

1 

55-60 

Saxonska 

Red 

Dry,  hard 

Good 

Good  to  full 

Good 

68-72 

60-66 

Norfh  Russian 

Red 

68-72  1 

60-66 

Polish 

Red 

Med.,  hard,  or 
mild 

Sweet 

Fair  to  good 

66-71  i 

i 

60-62 

Siberian 

Red 

Medium 

Dry,  strong 

,,  „ 

Fair 

65-70 

56-60 

Ulka  

TURKEY. 

Red 

Mild  to  Hard 

Good 

Good 

Good 

66-72 

1 60-64 

Danubian,  first 

quality 

Red 

Hard  or  flinty 

Dry 

Low,  fair  to 
good 

Fair  to  good 

68-72 

60-64 

Danubian,  second 
quality 

Red 

Med.  hard  to 
flinty 

Low  to  fair 

66-70 

59-63 

Salonica 

Red 

Dry  to  hard 

1 

Fair  to  good 

66-70 

60-63 

Dede  Agatch 

Red 

» 

1 

” 

66-70 

60-63 

HUNGARIAN  (Hard) 

Red 

1 

Dry  hard  to 
flinty 

1 

Dry,  sweet 

! 

Good  to 

full 

Good 

68-72 

60-64 

ARGENTINE. 

Choice  Plate,  No.  1 

j Red 

Mild  to  dry  hard 

Sweet 

Fair  to  good 

Choice 

67-70 

62-64 

Barletta  (Ros  Fe) 

59-63 

F.A.Q.  Plate,  No.  2 
Barletta 

i Red 

Mild  to  med. 
hard 

: 

Good  to 

choice 

65-68 

Bar-Russu  (Barisco) 

Red 

Hard 

Sweet 

Fair  to  good 

Bright 

66-72 

60-65 

Bahia 

1 

Red 

Mild  to  dry  hard 

Sweet 

Fair  to  good 

Good  to 
choice 

67-70 

60-64 

CALIFORNIAN  . . 

Red 

Brittle  to  dry 
hard 

Dry,  rough 

Low 

I 

Fair  to  good 

' 68-72 

60-63 

DANTZIC  . . . . 

Red 

Soft,  mild,  to 
dry 

Sweet 

1 Fair 

Good 

68-71 

60-63 

KONIGSBERG  . . 

Red 

,, 

„ 

,, 

68-71 

60-63 

INDIAN,  No.  l(Hard 

Red 

Hard  to  flinty 

Dry,  ricey 

Fair  to  good 

Fair  to  good 

, 68-72 

62-66 

Delhi) 

61-64 

„ No.  1 (Soft) 

Red 

Mild  to  dry  hard 

Dry 

,, 

„ 

66-70 

„ No.  2 (Mixed) 

Red 

- 

” 

66-70 

60-63 

SAMSOON  (Asia 

Red 

Dry  to  brittle 

Low  to  fair 

Low  to  fair 

66-70 

60-63 

Minor) 

65-70 

60-63 

PERSIAN  . . . . 

Red 

Brittle  to  hard 

MANCHURIAN  . . 

Red 

Medium,  hard 

” 

Fair 

65-70 

56-62 

MOLDAVIAN 

Red 

Dry  to  hard 

Dry  or  sweet 

i 

Fair  to  good 

Fair  to  good 

68-7  2 

60-64 

Weight  per  bushel  is  for  Imperial  measure,  and  wheat  supposed  uncleaned  as  imported  unless  grossly  mixed  with 
coarse  light  refuse — then  after  a light  screening  only.  The  weights,  flour  yields,  and  losses  in  cleaning,  as  also  the 
ordinary  refuse  contained  in  the  different  sorts,  arc  all  to  be  taken  as  the  fair  average  range.  Russian  samples  admit  of 


CHEMICAL  COMPOSITION  OF  WHEAT. 


289 


FOREIGN  REDS) — continued. 


IMPURITIE3  Present. 

General  Remarks. 

Pro- 

Regular. 

Occasional. 

bable 

O' 

O 

Smut,  seeds,  oats. 

Peas,  dirt,  stone 

3-6 

The  presence  of  frosted  grain  should  induce  cau- 

barley 

tion.  Low  yields. 

White  maize,  oats, 

Dirt,  stone,  smut 

2-4 

Excellent  substitute  for  English.  Decidedly  weak 

seeds,  peas 

in  baking. 

Rye,  seeds,  dirt, 

Smut,  barley,  oats 

2-3 

The  best  all  the  year  round  wheats  to  fill  place  of 

screenings 

2 3 

American  Springs. 

>>  M 

3-8 

More  waste  than  in  No.  1 grades,  and  a lower  flour 

3-8 

yield  to  be  expected  always. 

Rye,smut,dirt,seeds 

Barley,  oats,  stone 

5-12 

99  99  99  99  99 

Excess  of  rye,  smut,  and  seeds  demands  great  care 

in  working. 

Cockle,  screenings, 

Smut,  rye,  oats. 

2-6 

When  available  a useful  change  for  best  Ghirkas. 

dirt 

barley 

2-6 

3-8 

Cockle,  rye,  dirt, 

Smut,  oats,  barley 

Somewhat  softer  than  Azimas  and  Ghirkas.  Often 

seeds 

a better  colour. 

Rye,  seeds,  dirt 

,,  ,,  ,, 

3-8 

inferior  to  standard  grades  of  Russian. 

99  99  99 

3-8 

Now  largely  used  to  replace  Azima  and  Ghirka. 

Tares,  seeds,  screen- 

Smut,  oats,  barley 

2-4 

Clean  bright  grain.  Hard  usually,  and  requires 

ings 

plenty  of  water. 

Tares,  rye,  smut. 

Dirt,  oats,  barley 

3-8 

Often  difficult  to  clean  satisfactorily  owing  to 

seeds 

large  tares  and  other  seeds. 

Screenings,  barley. 

Stones,  rye 

3-8 

Not  a high  grade,  though  useful  cheap  mixing  sort. 

smut,  dirt 

99  99 

3-8 

Seeds  and  screen- 

Rye, oats,  barley 

1-4 

Bright  regular  grain.  Should  be  of  maximum 

ings,  dirt 

strength. 

, Black  oats,  barley. 

Smut,  dirt 

2-4 

Long  berried  and  fairly  clean.  Will  produce  very 

seeds 

white  flour. 

Blach  oats,  barley. 

Dirt,  stone 

3-6 

Variable  as  to  waste  and  growm  grain.  Well 

1 smut,  seeds 

cleaned  will  work  white. 

Oats,  Barley 

Smut,  seeds 

2-6 

Dry  brittle  variety  very  useful  for  replacing  Ameri- 

can Winters  or  Ros  Fe  Plates. 

Black  oats,  barley. 

Smut,  maize,  dirt 

2-5 

Nearly  as  good  quality  as  good  Plate  Barlettas 

seeds 

Short  straws,  oats. 

Dirt,  stone,  scented  ; 

2-5 

1 Yields  a characteristic  yellow  flour.  As  a rule 

barley  seeds 

seeds 

very  weak. 

Seeds,  barley,  oats 

Dirt,  smut,  rye 

2-5 

More  akin  to  English  in  work  than  any  other. 

I White  flour. 

»»  >> 

,,  ,,  ,, 

2-5 

Generally  as  the  Dantzic  grades.  Mild  coloury  wheat. 

Dirt,  stone,  seeds. 

Gram,  oats,  spice 

3-6 

Often  large  and  good  grain.  Requires  great  care 

barley,  peas 

3-6 

5-12 

in  cleaning  and  milling. 

» » " 

99  99  99 

Being  under  top  grade,  will  call  for  greater  care  in 

1 

working. 

Dirt,  stone,  barley,  ; 

Oats,  peas,  beans 

4-12  I 

Variable  as  a rule ; needs  extreme  care  in  cleaning. 

seeds 

,,  ,,  ,, 

>>  »»  >> 

4-10  i 

Must  be  washed  well  to  get  full  value  from  these 

hard  wheats. 

Rye,  seeds 

Barley,  oats 

3-8 

Useful  to  replace  any  secondary  reds  of  fair 

2-6  ! 

strength. 

Tares,  seeds,  rye. 

Barley,  oats,  dirt 

At  times  will  mill  and  bake  very  well.  Heavy 

smut 

I 

1 

sound  wheats. 

almost  endless  classification  under  names  of  ports — Berdianski,  Novorrossisk,  Ghenighesk,  Marianople,  Nicolaieff, 
Odessa,  and  many  others.  The  general  types  are  in  all  these  instances  Aziinas  and  Ghirkas,  and  the  above  analysis  will 
therefore  apply  unless  a new  grade  is  specified. 

u 


290  THE  TECHNOLOGY  OF  BREAD -MAKING. 

The  composition  of  the  wheat  at  each  stage  is  given  in  the  following 
table  : — 

Table  showing  the  Proximate  Composition  of  Wheat,  in  Per  Cent. 
OF  THE  Total  Dry  Matter,  at  Fourteen  Different  Periods  of 
Three  Days  each  from  the  Setting  of  the  Grain  to  Past  Ripe- 
ness, THE  Wheat  being  Gathered  and  Dried  on  the  Straw. 


Groups. 

I. 

II. 

HI. 

IV. 

V. 

VI. 

VII. 

Ash 

* 4-81 

4-16 

3-24 

2-52 

2-16 

2-07 

1-82 

Proteins 

17-80 

17-30 

15-36 

14-30 

13-75 

13-15 

13-64 

Amides 

2-83 

1-40 

1-01 

0-91 

0-78 

0-56 

0-51 

Fats 

4-32 

3-09 

2-64 

2-51 

2-31 

2-38 

2-45 

Crude  Fibre  . . 

8-69 

6-96 

5-50 

4-56 

3-72 

3-30 

3-10 

Pentosans ' 

13-54 

12-84 

12-28 

11-10 

9-73 

9-66 

9-32 

Dextrins 

2-00 

3-07 

2-86 

2-66 

2-26 

2-11 

1-94 

Sucrose.  . 

2-95 

2-80 

2-26 

1-94 

1-42 

1-45 

1-45 

Glucose 

1-55 

0-64 

0-17 

0-08 

007 

0-05 

0-05 

Starch  and  Un- 

termined 

41-51 

47-74 

54-68 

59-42 

63-80 

65-27 

65-72 

Groups. 

VIII. 

IX. 

X. 

XI. 

XII. 

XIII. 

XIV. 

Ash 

1-80 

1-68 

1-79 

1-77 

1-59 

1-87 

1-67 

Proteins 

14-55 

15-40 

16-24 

14-96 

16-59 

16-56 

17-26 

Amides. . 

0-50 

0-44 

0-50 

0-44 

0-61 

0-62 

0-56 

Fats 

2-59 

2-60 

2-44 

2-50 

2-37 

2-46 

2-52 

Crude  Fibre  . . 

3-11 

3-01 

3-03 

3-04 

2-98 

3-00 

2-96 

Pentosans 

8-82 

8-50 

8-41 

8-08 

8-16 

8-33 

8-63 

Dextrins 

1-75 

1-72 

1-83 

2-46 

1-77 

1-79 

1-75 

Sucrose. . 

1-43 

1-28 

1-44 

1-52 

1-51 

1-53 

1-50 

Glucose 

Trace 

0-01 

Trace 

Trace 

Trace 

Trace 

Trace 

Starch  and  Un- 

determined . . 

65-45 

65-36 

64-32 

65-23 

64-42 

63-84 

63-15 

(Bull,  53,  1898, 

Arkansas 

Agric. 

Expt.  Stn.) 

429.  Effect  of  Shade  on  Wheat  Composition,  Thatcher  and  Watkins. — 

As  a result  of  comparative  experiments  made  on  the  same  wheat  grown 
and  ripened  in  sunshine  and  in  shade  respectively,  Thatcher  and  Watkins 
find  that  the  shaded  wheat  gives  grains  wRich  are  darker  in  colour.  The 
protein  is  slightly  higher  and  the  starch  lower  than  in  the  unshaded  samples 
{Jour.  Amer.  Chem.  Soc.,  1907,  764). 

430.  Frosted  Wheat,  Shutt. — ^Shutt  finds  on  analysis  that  the  protein 
content  of  frosted  wheat  is  considerably  higher  than  that  in  the  unfrosted 
mature  grain.  The  effect  of  frost  is  a premature  ripening,  or  rather  drying- 
out  of  the  grain,  with  as  a consequence,  a kernel  high  in  protein,  but  low 
in  starch  (Jour.  Amer.  Chem.  Soc.,  1905,  368). 


CHAPTER  XV. 

THE  STRENGTH  OF  FLOUR. 

431.  Physical  Properties  of  Flour. — In  addition  to  its  purely  chemical 
composition,  flour  possesses  certain  physical  properties  which  are  of  the 
highest  importance  to  the  baker,  and  consequently  to  the  miller.  These 
are  “ Strength and  “ Colour.”  Flavour  may  also  be  mentioned,  but 
this  is  essentially  rather  a matter  of  the  palate  than  of  chemical  analysis, 
hence  a judgment  of  the  flavour  of  flour  is  best  made  by  the  actual  con- 
sumer. These  three  properties  of  Strength,  Colour,  and  Flavour,  together 
with  certain  side  issues  connected  with  them,  largely,  if  not  entirely,  deter- 
mine the  commercial  value  of  a sample  of  flour. 

432.  Nature  of  Strength. — There  are  certain  desirable  qualities  in  a 
bread-making  flour  which  commonly  go  together.  Among  these  are  a 
large  relative  yield  of  bread  due  to  a high  water-absorbing  capacity,  the 
power  of  producing  a large  loaf,  that  of  producing  a bold  loaf,  and  a well- 
piled  loaf.  In  consequence  of  these  usually,  but  not  invariably,  accom- 
panying each  other,  strength  has  been  variously  defined  as  the  property  of 
causing  one  or  other  of  these  effects.  In  the  1895  edition  of  this  work  the 
following  occurs  : — 

“ Strength. — This  particular  term  is  sometimes  employed  with  different 
meanings  by  various  handlers  of  flour.  In  former  works  by  the  author 
on  this  subject,  he  used  it  as  meaning  a measure  of  the  water-absorbing 
power  of  the  flour,  and  explained  that  the  term  ‘ Strength  is  also  some- 
times used  as  the  measure  of  the  capacity  of  the  flour  for  producing  a 
well-risen  loaf."  In  deference  to  the  fact  that  its  employment  in  this 
latter  sense  is  the  more  general,  the  author  also  adopts  the  same  defini- 
tion, especially  as  the  term  ‘ water-absorbing  power " is  very  con- 
venient, and  in  itself  explanatory.  Strength,  then,  is  defined  as  the  measure 
of  the  capacity  of  the  flour  for  producing  a bold,  large-volumed,  well-risen, 
loaf.  It  is  in  this  sense  that  the  word  is  throughout  used  in  the  present 
work.  Unfortunately  at  present  there  is  no  very  satisfactory  method 
of  numerically  registering  strength  except  through  a baking  test,  when 
the  actual  volume  or  girth  of  the  loaf  may  be  measured.  Inferentially, 
the  strength  of  a flour  may  be  deduced  from  the  character  and  quality 
of  the  gluten."" 

433.  Home-grown  Wheat  Committee’s  Definition. — Humphries  and 
Biffen,  in  a paper  on  “ The  Improvement  of  English  Wheat,”  define  their 
view  of  “ strength.""  They  dismiss  those  estimates  which  are  based  on 
measurements  of  water- absorbing  power  to  produce  a dough  of  standard 
consistency,  remarking  that  bakers  do  not  make  the  various  kinds  of  flour 
up  to  one  and  the  same  consistency  in  the  doughs.  To  give  the  best  pos- 
sible loaves,  some  require  to  be  made  into  “ tight,""  others  into  slack  doughs, 
and  the  baker  simply  learns  by  experience  what  particular  degree  of  con- 
sistency is  the  most  suitable  for  the  flour  in  hand.  Number  of  loaves  per 
sack  is  another  common  method  (being  a variant  of  water-absorbing  power) . 
But  some  Russian  and  most  Indian  wheats  give  a large  number  of  loaves 

291 


292 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


but  small  and  close  of  texture.  This  also  is  regarded  as  unsatisfactory. 
“ A third  view,  apparently  largely  adopted  by  the  bakers,  is  to  judge  strength 
by  the  way  a flour  behaves  in  the  doughs,  by  its  toughness,  elasticity, 
freedom  from  stickiness,  etc.  ; in  other  words,  by  the  facility  with  which 
large  masses  of  dough  can  be  handled  in  the  bakehouse.  It  seems  more 
satisfactory  to  regard  them  as  separate  characteristics,  for  though  of  un* 
doubted  importance  to  the  baker,  they  are  not  necessarily  associated  with 
the  production  of  satisfactory  loaves.  The  fact  that  some  of  the  Russian 
wheats  from  St.  Petersburg  or  Reval  are  esteemed  strong,  but  w^ork  very 
badly  in  the  doughs,  will  show'  the  necessity  for  this  distinction.’' 

“ The  deflnition  finally  adopted  by  the  Committee  [Home-growm 
Wheat  Committee  of  the  National  Association  of  British  and  Irish 
Millers]  is,  that  a strong  wheat  is  one  which  yields  flour  capable  of  making  large 
well-piled  loaves,  the  latter  qualification  thus  excludes  those  wheats  pro- 
ducing large  loaves  w'hich  do  not  rise  satisfactorily.  To  estimate  the 
strength  of  any  particular  sample  of'  wlieat  then  it  is  necessary  to  grind  it 
and  make  the  final  tests  in  the  bakehouse.” 

The  baking  tests  w'ere  carried  out  in  the  following  manner  : — “ In  the 
first  place  the  baking  trials  are  made  with  sufficient  flour  to  yield  a batch 
of  about  half-a-dozen  loaves — the  ‘ cottage  ’ shape  being  considered  the 
most  satisfactory.  With  each  set  to  be  tried,  loaves  are  baked  from  flour 
whose  quality  has  been  accurately  ascertained.  To  these  standard  loaves- 
a certain  number  of  marks  are  assigned,  and  by  comparison  the  baker 
records  in  marks  his  opinion  of  the  strength  of  the  flour  under  test.  On 
this  arbitrary  scale  the  strongest  wlieats  in  commerce  mark  about  100, 
‘ London  Households  ’ 80  to  85,  and  average  Engfish  60  to  65.  The  tests 
are  always  carried  out  by  a man  wlio  devotes  the  whole  of  his  time  to  this 
kind  of  w'ork,  and  repeated  trials  have  shown  that  they  may  be  rehed  upon 
to  express  the  strength  with  substantial  accuracy  ” (Jour.  Agric.  Science^ 
1907,  IL,  1). 

This  definition  of  strength  is  in  close  agreement  with  that  of  one  of  the 
authors,  previously  quoted.  In  the  one  there  is  the  expression  “ well- 
risen,”  and  in  the  other  “ w'ell-piled  ” ; the  latter  term  being  employed 
to  exclude  large  loaves  which  do  not  rise  satisfactorily.  A large  loaf  of 
coarse  and  ragged  texture,  and  full  of  big  holes,  would  not  be  regarded  as 
either  w'ell-risen  or  w'ell-piled. 

434.  Definition  of  Pile. — ^An  explanation  of  the  meaning  attached  to  the 
w'ord  “ pile  ” may  here  be  of  service.  It  is  stated  on  the  authority  of  a 
w'ell-knowTi  Scottish  baker,  that  the  baker’s  use  of  the  word  originated  in 
Scotland.  Their  very  high  close-packed  loaves  are  smeared  on  the  sides 
with  melted  lard  before  being  placed  in  the  oven.  They  are  then  easily 
pulled  asunder,  and  the  surface  of  the  separated  sides  should  have  a smooth 
silky  texture,  a texture  in  fact  recalling  the  “ pile  ” of  velvet.  Such  loaves 
are  said  to  have  a good  pile,  or  to  be  w'ell-piled.  A good  pile  is  associated 
with  the  same  fine  evenness  of  texture  throughout  the  interior  of  the  loaf, 
and  hence  the  term  has  acquired  the  secondary  meaning  of  an  even,  finely 
vesiculated,  and  silky  texture  of  the  substance  of  the  loaf. 

435.  Value  of  Baking  Tests. — Any  carefully  devised  method  of  making 
baking  tests  can  scarcely  fail  to  differentiate  strong  from  w'eak  flours.  The 
difficulty  is  with  those  of  intermediate  and  approximating  character  and 
quality,  and  here  much  must  depend  on  the  suitability  of  the  method  of 
working  to  the  particular  flour.  To  give  an  example  of  what  is  m.eant, 
suppose  a baker  of  one  district  adopts  a four  hours’  system  of  fermentation, 
and  another  a six  hours’  system.  A flour  wliich  is  just  exactly  ripe  at  the 
end  of  four  hours  would  appear  much  stronger  to  the  four  hours’  baker 


THE  STRENGTH  OF  FLOUR. 


293 


than  to  the  latter.  Conversely  a six  hours'  flour  would  be  relatively  strong 
to  the  six  hours'  baker  and  weaker  to  the  four  hours'  workman.  An  alter- 
native method  would  be  to  allow  the  fermentation  to  proceed  to  the  best 
possible  point  for  each  particular  flour  and  then  bake  it.  This,  however, 
introduces  another  element,  in  which  there  would  almost  certainly  be  con- 
siderable variations  in  judgment.  As  a result  of  variations  such  as  these, 
it  is  probable  that  out  of  six  baking  experts  no  two  would  arrange  a series 
of  flours  in  quite  the  same  order.  Therefore,  though  Humphries'  and  Bif- 
fens'  baking  tests  may  be  regarded  as  comparative  among  themselves,  the 
reservation  must  always  be  borne  in  mind  that  there  is  no  absolute  and 
unvarying  standard  of  strength.  That  flour  is  strongest  which  under  the 
particular  conditions  of  fermentation  employed  or  required  by  any  particu- 
lar baker  or  district  best  conforms  to  the  definition  previously  given  of 
strength. 

436.  Conditions  requisite  for  Strength. — A loaf  of  bread  consists  of  a 
baked  aerated  mass  of  elastic  dough.  The  first  requisite  of  a strong  flour 
is  that  there  must  be  a sufficiency  of  sugar  or  other  material  available  for 
fermentation  and  consequent  production  of  gas  in  the  dough.  As  dough 
fermentation  involves  a series  of  changes  in  Avhich  the  distention  by  gas  is 
but  one,  the  source  of  gas  must  be  sufficient  for  its  continuous  produc- 
tion, not  only  at  the  earher  stages,  but  throughout  the  whole  process,  and 
essentially  during  that  period  in  which  the  loaf  is  acquiring  its  final  shape 
and  volume  ; that  is  to  say,  some  little  time  before  and  after  it  is  placed 
in  the  oven. 

Then  next  there  must  be  some  substance  present  in  the  flour  which 
shall  be  capable  of  retaining  a sufficiency  of  the  gas  generated  in  the  dough, 
and  elastic  enough  to  be  evenly  distended  by  such  gas.  According  to  the 
kind  of  loaves  to  be  made,  the  requirements  for  strength  somewhat  vary. 
If  the  bread  is  to  be  baked  in  a tin,  it  is  supported  on  all  its  four  sides,  the 
top  only  being  open  ; the  same  holds  good,  though  to  a slightly  lesser 
degree,  in  close-packed  oven-bottom  bread,  where  the  loaves  support  each 
other.  For  bread  of  this  kind,  the  dough  may  be  very  soft  and  even 
“ runny,"  provided  it  is  elastic  and  of  good  gas-retaining  capacity.  But 
when  the  bread  is  baked  into  crusty  loaves,  whether  of  the  cottage  or  Coburg 
type,  the  dough  must  not  only  be  elastic  and  gas-retaining,  but  it  must 
also  possess  sufficient  rigidity  to  maintain  its  shape  when  standing  alone 
and  independently.  Otherwise  it  may  make  a large  but  flat  loaf,  and  not 
a bold  well-risen  one.  The  requisites  necessary  for  strength  under  one  of 
these  sets  of  conditions  are  not  precisely  the  same  as  in  the  other. 

It  is  generally  recognized  that  the  constituent  of  wiieaten  flour  in  virtue 
of  which  its  dough  possesses  these  qualities  of  gas-retaining  power  and 
elasticity,  is  that  known  as  gluten,  that  curious  body  largely  composed 
of  gliadin  and  glutenin.  There  must  be  sufficient  gluten  present  to  ade- 
quately retain  gas  and  confer  elasticity.  Too  much  may  be  injurious, 
inasmuch  as  it  may  offer  too  great  a resistance  to  the  action  of  the  distend- 
ing gas  ; the  consequence  of  this  is  the  production  of  small  and  what  are 
sometimes  called  “ gluten-bound  " loaves.  Further  the  gluten  must  be 
of  the  right  quality,  it  must  be  sufficiently  impermeable  to  gas  ; it  must  be 
highly  elastic,  yielding  readily  to  distention  wdthout  breaking,  and  yet 
it  must  be  sufficiently  rigid,  particularly  in  the  case  of  crusty  loaves,  to 
maintain  a well-upstanding  bold  shape.  Quantity  and  character  of  gluten 
may  to  a certain  extent  compensate  each  other.  If  the  gluten  is  excep- 
tionally good,  a little  less  of  it  may  suffice,  while  slight  deficiency  in  quality 
may  be  made  up  by  a little  extra  in  amount.  Added  to  all  this,  important 
changes  are  going  on  in  the  gluten  during  the  whole  of  the  time  of  its  fer- 


294 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


mentation.  Normally,  it  is  softening  as  fermentation  proceeds,  and  becomes 
more  yielding  and  gas-retaining  during  that  operation.  There  comes  a 
time,  however,  when  the  gas-retaining  power  is  at  its  best,  and  further 
change  simply  injures  and  diminishes  its  tenacity.  The  art  of  the  baker 
in  part  consists  in  so  balancing  all  these  various  factors  as  to  get  the  best 
possible  result  out  of  the  flour  with  which  he  is  working. 

437.  Research  on  Strength. — In  view  of  the  importance  of  this  problem 
of  strength,  it  has  always  received  the  keenest  attention  from  those  who 
have  in  any  way  made  a study  of  bread-making.  In  particular,  there  has 
been  an  immense  amount  of  work  done  in  this  direction  during  the  past 
fifteen  years,  and  especially  since  Osborne  and  Voorhees  established  de- 
finitely the  composition  and  properties  of  the  proteins  of  flour.  The  investi- 
gations referred  to  have  been  made  by  eminent  scientists  in  conjunction 
vdth  advanced  manufacturers  in  both  America  and  Europe  including  this 
country.  There  seems  no  adequate  method  of  presenting  the  results  to 
the  students  of  bread-making  other  than  by  giving  a resume  of  the  work 
that  has  been  done,  followed  by  a summary  of  the  conclusions  which  may 
at  this  stage  be  formed.  Probably  the  best  and  simplest  way  will  be  to 
arrange  the  abstracts  of  such  research  work  in  chronological  order. 

438.  Knowledge  in  1895. — As  a starting  point,  the  following  paragraphs 
on  the  effect  of  each  leading  constituent  of  wheat  are  quoted  from  the  1895 
edition  of  this  work.  When  originally  prepared  they  were  intended  as  a 
summary  of  the  general  knowledge  at  that  time. 

“ Fat. — As  far  as  is  at  present  known,  the  quantity  of  fat  in  wheat 
is  not  a very  important  element  in  determining  its  value.^  Fat  is  of 
course  an  important  food  stuff,  and  as  such  is  of  service.  The  germ 
of  flour  contains  a very  high  percentage  of  fat,  and  when  removed 
must  necessarily  lessen  the  percentage  of  this  body  present. 

Starch. — This  makes  up  the  principal  part  of  the  grain,  and  in  the 
analyses  given  varies  from  63*71  to  67*88  in  the  different  wheats. 
In  these  analyses  the  starch  was  probably  determined  by  difference  ; 
that  is,  the  percentage  of  the  other  constituents  was  subtracted  from 
100,  and  the  remainder  considered  to  be  starch  : the  quantity  of  starch 
will  therefore  naturally  be  the  complement  of  the  other  bodies  rising 
when  they  fall  and  falling  when  they  rise.  Starch  is  of  course  of  great 
importance  as  being  the  principal  food-stuff  of  bread  : in  sound  wheat 
the  starch  granules  are  whole,  while  in  wheat  which  has  sprouted,  or 
heated  unduly  through  damp,  the  starch  granules  are  pitted,  and  often 
fissured.  The  result  is  that  their  contents  become  more  or  less  changed 
into  dextrin  and  sugar. 

Cellulose. — This  substance  is  of  considerable  service  to  the  plant  ; 
but  to  the  miller  it  has  no  value,  as  being  useless  as  an  article  of  food, 
he  endeavours  to  keep  it  out  of  the  flour.  As  the  cellulose  is  found 
principally  in  the  bran,  the  thinner  skmned  wheats  will  yield,  on  analysis, 
less  cellulose.  Judgmg  the  cellulose  alone,  the  less  quantity  present 
the  better  is  the  wheat. 

Dextrin  and  Sugar. — Dextrin  exists  in  sound  wheat  in  but  small 
quantity  ; but  when  hydrolysis  of  the  starch  has  set  in,  the  percentage 
may  considerably  increase  : in  wheats  or  flours  the  presence  of  large^ 
quantities  of  dextrin  would  be  decidedly  objectionable.  Sugar  is. 
always  present  to  a slight  extent  in  wheat.  Bell  states  that  the  sugar- 
^ See  Fatty  Matters  and  Acidity  of  Flour,  paragraph  498. 


THE  STRENGTH  OF  FLOUR. 


295 


“ corresponds  in  properties  to  cane  sugar,  as  it  does  not  reduce  Fehling’s 
solution,  but  may  be  readily  inverted  by  sulphuric  acid.  Bell  extracts 
the  sugar  vitli  70  per  cent,  alcohol,  and  so  prevents  any  action  on  the 
sugar  by  the  proteins.  The  author  finds  that  on  extraction  with  water 
the  sugar  invariably  produces  more  or  less  precipitate  with  Fehling’s 
solution  ; the  amount  of  precipitate  being  increased  by  treatment 
vith  sulphuric  or  hydrochloric  acid.  Paragraph  370,  chapter  XI., 
gives  some  results  of  sugar  determinations  in  the  aqueous  extract  of 
flour.  The  explanation  of  these  results  seems  to  be  that,  in  perfectly 
sound  wheat  or  flour,  small  quantities  of  cane  sugar,  only,  exist.  In 
ansound  wheats  or  flour,  in  which  the  starch  has  been  subjected  to 
diastasis,  maltose  may  also  be  detected.  Wanklyn  makes  the  useful 
suggestion  that  estimations  of  sugar  should  be  made  in  both  aqueous 
and  alcoholic  extracts  : unsoundness  in  flour  would  be  indicated  by 
the  presence  of  an  increased  amount  of  maltose  in  the  alcoholic  extract. 

Assuming  the  correctness  of  Bell's  statement  that  sound  wheat 
sugar  does  not  reduce  Fehling's  solution,  an  alcoholic  extract  of  sound 
wheat  should  give  no  precipitate  with  that  reagent.  Any  maltose 
therefore  in  an  alcoholic  extract  is  the  measure  of  diastasis  of  the  starch 
of  the  grain  that  had  occurred  previous  to  analysis.  If  the  flour  be 
then  mixed  with  water,  and  allowed  to  stand  for  a definite  time,  and 
then  the  maltose  estimated  in  the  aqueous  extract,  the  difference  be- 
tween the  amount  obtained  in  this  estimation  and  the  former  one  would 
be  a measure  of  the  quantity  of  soluble  starch,  arising  from  fissured 
granules,  present  in  the  flour.  A series  of  comparative  estimations  of 
this  kind  would  be  of  service. 

As  the  sugar  of  a flour  affords  the  saccharine  body  necessary  in  fer- 
mentation, the  presence  of  this  compound  in  small  quantity  may  be 
tolerated,  but  as  before  pointed  out,  it  should  consist  principally  of 
cane  sugar,  the  presence  of  much  maltose  being  evidence  of  unsoundness. 

Soluble  Proteins. — In  technical  wheat  analysis  no  attempt  is  made 
to  separate  the  albumin  from  the  globulin.  In  the  following  analyses 
these  bodies  are  estimated  in  a portion  of  the  aqueous  extract  of  the 
flour,  by  either  what  is  known  as  the  albuminoid  ammonia  process, 
or  by  Kjeldahl's  process  ; of  which  latter,  in  common  with  other 
analytic  methods,  a description  is  given  hereafter.  As  has  been  already 
stated,  these  bodies  have  a serious  action  on  starch,  and  also  on  gluten  ; 
under  the  influence  of  yeast,  during  fermentation,  they  act  on  the 
starch  and  convert  that  body  into  dextrin  and  maltose.  In  the  para- 
graph on  artificial  diastase.  No.  267,  this  action  is  somewhat  fully  de- 
scribed. A relatively  low  percentage  of  soluble  proteins  is  usually  to 
be  preferred  as  indicating  soundness  both  in  flours  and  wheats.  In  the 
case  of  wheat  it  is  somewhat  difficult  to  form  a judgment,  because  the 
bran  and  germ  contain  considerable  quantities  of  soluble  proteins  ; as 
these  are  removed  in  the  operation  of  milling  the  proportion  differs 
somewhat  in  the  wheat  from  that  in  the  dressed  flour.  It  is  in  damp 
years  and  wet  climates  that  inferior  wheats  are  grown  ; the  excess  of 
moisture,  and  lack  of  warm,  dry  sunshine,  leave  the  grain  damp,  and 
also  leave  the  proteins  in  the  soluble  condition,  instead  of  thoroughly 
ripening  the  grain,  and  thus  causing  them  to  assume  the  insoluble  form. 

From  time  to  time  attention  has  been  directed  to  the  problem  of 
artificially  drying  wheats.  With  some  samples  of  wheat  this  is  prac- 
tically a necessity,  as  otherwise  they  are  absolutely  unfitted  for  flour 
producing  purposes.  A gentle  kiln-drying  at  a temperature  of  from 
100°  to  120°  F.,  by  driving  off  the  excess  of  water,  arrests  its  degrading 


296 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


“ action  on  the  gluten,  and  causes  the  wheat  to  yield  a sounder  and 
stronger  flour.  The  drying  is  necessarily  accompanied  by  loss  of 
weight  ; against  this  must,  however,  be  set  the  improved  quahty  of 
the  flour.  In  connection  Avith  this,  attention  is  directed  to  the  para- 
graph on  artificially  drying  wheats  and  flours,  in  the  next  chapter. 

Soluble  Extract. — In  the  following  analyses  by  the  author  the 
percentage  of  ‘ soluble  extract ' is  in  most  cases  given.  This  repre- 
sents the  proportion  of  the  wheat  or  flour  soluble  in  cold  water.  The 
sample  is  continuously  shaken  up  with  water  for  five  minutes,  allowed 
to  settle  for  the  remainder  of  half  an  hour,  then  filtered  from  the  sohd 
matter,  the  clear  liquid  evaporated,  dried  at  100°  C.  (212°  F.)  and 
weighed.  This  extract  consists  of  soluble  proteins,  sugar  and  dex- 
trin, and  potassium  phosphate.  Considerable  importance  attaches 
to  the  amount  of  soluble  extract,  as  being  the  measure  of  the  amount 
of  degradation  of  the  gluten  and  starch  of  the  wheat  or  flour  ; conse- 
quently an  excess  of  soluble  extract  indicates  unsoundness.  On  the 
other  hand,  a very  low  percentage  of  sugar  in  a flour  or  wheat  is  accom- 
panied by  an  absence  of  that  sweetness  characteristic  of  the  best 
flavoured  wheats  and  flours. 

Insoluble  Proteins,  Gluten. — The  insoluble  proteins  are,  for  practical 
purposes,  estimated  by  doughing  the  flour,  and  washing  away  the 
starch,  leaving  behind  the  tough  and  elastic  gluten.  The  gluten  of 
wheat  is  of  great  importance,  as  being  that  constituent  which  imparts 
to  wheaten  flour  its  remarkable  property  of  rising  into  a light  and 
spongy  loaf.  The  gluten  is  usually  weighed  both  in  the  moist  or  wet 
state,  and  also  when  dry  ; it  weighs  from  2*7  to  3 times  as  much  when 
moist  as  dry.  As  the  gluten  of  wheat  is  that  constituent  which  causes 
the  flour  to  be  a strong  flour,  wheats  to  be  of  high  quality  should  con- 
tain a high  percentage  of  gluten.  This,  how^ever,  is  not  of  itself  suffi- 
cient ; the  glutens  of  different  wheats  vary  not  only  in  quantity  but 
in  quahty — some  glutens  are  tough  and  elastic,  others  are  soft  and 
‘ rotten."  These  latter  yield  weak  flours,  and  consequently  bread  which 
is  not  well  risen  ; further,  the  quantity  of  water  they  are  capable  of 
retaining  is  but  small.  They  as  a result  produce  a comparative  low 
number  of  loaves  from  a sack  of  the  flour.  The  gluten  then  should  not 
only  be  present  in  considerable  quantity,  but  should  also  be  highly 
elastic. 

Between  the  amount  of  gluten  and  of  soluble  proteins  in  a wheat  a 
close  relation  exists.  With  an  increase  of  total  proteins,  both  the 
soluble  and  insoluble  varieties  will  simultaneously  rise  in  amount.  In 
interpreting  analytical  results,  high  soluble  proteins  should  not  be 
considered  alone — they  are  the  natural  concomitants  of  high  total 
proteins  and  gluten.  But  where  the  soluble  proteins  are  high,  and  the 
gluten  low,  then  distinct  evidence  of  a low  grade  or  unsound  wheat  is 
afforded. 

The  aleurometer  is  an  instrument  designed  for  the  purpose  of  estimat- 
ing the  elasticity  of  gluten  ; the  higher  the  figures  obtained  by  its 
use,  the  more  elastic  the  gluten  is  supposed  to  be. 

‘ True  Gluten.’ — It  is  difficult,  and  in  many  cases  impossible,  to 
wash  away  the  whole  of  the  starch  from  flour  or  wheat  meal  without 
also  washing  away  some  of  the  more  soluble  parts  of  the  gluten  itself. 
In  consequence,  gluten  determinations  will  vary  according  to  the  thor- 
oughness of  the  washing,  and  this  differs  in  different  hands.  As  a 
clieck,  therefore,  on  gluten  determinations  in  cases  of  importance. 


THE  STRENGTH  OF  FLOUR. 


297 


“ the  author  advises  the  making  of  a nitrogen  estimation  on  the  dried 
gluten,  and  deducing  therefrom  the  amount  of  protein  it  contains  ; 
this  latter,  being  calculated  as  a percentage  on  the  whole  wheat  or 
flour,  is  denominated  percentage  of  ‘ true  " gluten.  The  amount  should 
be  at  least  80  per  cent,  of  the  crude  dry  gluten.  With  even  considerable 
differences  between  percentages  of  crude  gluten,  the  amounts  of  true 
gluten  agree  very  closely.  In  the  further  chapters  on  flour,  data  of 
various  estimations  are  given. 

Gliadin. — ^The  estimations  of  proteins  soluble  in  80  per  cent,  alcohol 
are  practically,  in  the  case  of  wheat  and  wheaten  flour,  estimations 
of  gliadin.  As  affording  evidence  of  the  quality  of  gluten,  gliadin 
estimations  may  possibly  prove  of  value.  It  is  probable  that  soft, 
ductile,  tenacious  glutens  may  contain  a high  percentage  of  gliadin, 
but  a sufficient  number  of  estimations  has  not  as  yet  been  made  to 
permit  the  drawing  of  any  deflnite  conclusions. 

Ash. — This  gives  the  quantity  of  mineral  matter  present  in  a wheat 
or  flour  ; the  ash  consists  principally  of  potassium  phosphate,  a sub- 
stance of  considerable  value  from  a nutritive  point  of  view  ; the  mineral 
matter  of  wheat  is  contained  principally  in  the  bran. 

Water. — ^The  water  of  wheat  is  found  to  be  mostly  associated  with 
the  starch  of  the  grain  ; that  body  is  extremely  hygroscopic,  and  can 
only  be  obtained  actually  free  from  water  by  prolonged  and  careful 
drying.  The  quantity  of  water  in  flour  and  wheat  does  not  vary  vdthin 
very  wide  limits,  the  highest  percentage  being  about  15,  and  the  lowest 
about  8 per  cent.  The  question  of  importance  is  the  influence  of  the 
water  on  the  quahty  of  the  grain  or  flour,  and  the  interpretation  to  be 
placed  on  such  results  as  are  here  given.  As  may  readily  be  supposed, 
a wheat  that  is  grown  either  in  a naturally  damp  climate,  or  during  an 
unusually  wet  season,  contains  more  water  than  one  grown  under  the 
opposite  conditions.  Taken  into  consideration  without  reference  to  the 
other  constituents  of  the  grain,  a large  proportion  of  water  is  to  be 
deprecated,  for  the  very  simple  reason  that  water  is  scarcely  worth 
purchasing  at  the  price  given  for  wheat  or  flour.  This,  however,  is  not 
the  only  objection  to  the  presence  of  a large  percentage  of  water  ; a 
much  more  serious  objection  is  based  on  the  fact  that  such  high  propor- 
tions show  that  the  wheat  is  unsound,  and  that  in  all  probabihty  the 
other  constituents  will  not  be  of  the  most  promising  character.  In  the 
first  place,  damp  wheats  and  flours  favour  the  development  of  those 
organisms  which  produce  mustiness  and  acidity.  In  the  presence  of 
excess  of  moisture,  too,  the  gluten  of  flour  is  rendered  soluble  in  part, 
and  also  loses  its  elasticity.  Further,  more  or  less  of  the  starch  will  be 
found  to  have  been  degraded  into  dextrin  and  maltose  by  diastasis. 

Valuation  of  Gluten — A number  of  attempts  have  been  made  to 
satisfactorily  determine  the  quality  of  gluten,  as  considered  apart  from 
its  actual  percentage  ; it  must  be  confessed,  however,  that  the  results 
obtained  have  been,  from  the  standpoint  of  commercial  testing,  some- 
what disappointing.  As  a result  of  experience  in  gluten  testing,  a 
judgment  can  be  formed  from  the  feel  and  appearance  of  the  gluten 
when  wet.  Some  glutens  are  soft  and  sticky,  possessing  at  the  same 
time  but  little  or  no  toughness.  Others,  again,  are  highly  elastic,  and 
firm  and  springy  to  the  touch  ; these  latter  are  special  qualities  which 
render  a flour  of  value  for  bread-making  purposes. 

The  Aleurometer. — The  instrument  knowm  as  the  aleurometer  is 
the  result  of  one  attempt  to  measure  these  qualities  of  gluten.  The 


298 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


“ principle  is  that  of  measuring  the  degree  of  expansion  of  the  wet  gluten 
on  being  maintained  for  som^e  time  at  a temperature  of  150°  C.  A small 
cylinder  is  provided,  to  which  is  attached  by  bayonet  catches  a bottom 
and  top  ; through  the  latter  of  these  passes  a graduated  piston  rod, 
fixed  in  its  turn  to  a piston  sliding  within  the  cylinder.  A weighed 
quantity  of  gluten  is  placed  in  the  cylinder,  and  the  whole  apparatus 
put  in  a hot  oil  or  glycerin  bath,  maintained  at  150°  C.  The  gluten 
expands  with  the  heat,  and  raises  the  piston,  its  maximum  expansion 
being  read  on  the  piston  rod.  This  instrument  certainly  divides  the 
glutens  of  flour  and  wheat  into  strong  and  weak  classes,  but  no  very 
fine  lines  of  distinction  can  with  accuracy  be  drawn. 

True  Gluten. — The  value  of  estimations  of  true  gluten  as  a check  on 
those  of  crude  gluten  has  already  been  indicated  ; but  they  have  also 
an  additional  importance.  Suppose,  for  example,  two  flours  each  yield 
35*0  per  cent,  of  wet  gluten.  One  is  hard,  elastic  and  springy,  while 
the  other  is  soft  and  flabby,  and  causes  the  washing  water  to  become 
‘ lathery.'  It  will  at  once  be  said  that  the  former  is  the  higher  quality 
gluten  of  the  two,  and  quite  correctly  : but,  further,  the  results  would 
be  entered  that  each  yielded  the  same  quantity  of  gluten.  This  latter 
deduction  is  not  all  the  truth,  for  in  the  former  case  hardness  of  the 
gluten  will  have  permitted  most  of  the  starch  to  be  entirely  eliminated 
with  the  least  possible  loss  of  real  gluten  constituents.  In  the  second 
instance  the  gluten  will  have  begun  to  wash  away  while  yet  there  is  a 
considerable  quantity  of  starch  remaining.  Therefore  the  35*0  per 
cent,  in  the  first  case  will  contain  more  real  gluten  and  less  foreign 
matter  than  in  the  second.  The  estimation  of  ‘ true  gluten  ' by  a 
nitrogen  determination  will  show  that  in  No.  I there  is  a higher  per- 
centage of  actual  gluten  protein  matter  than  in  No.  2,  and  that  there- 
fore the  weaker  character  of  the  second  flour  is  due  not  only  to  inferior 
quality  of  gluten,  but  also  in  part  at  least  to  a lower  percentage  of  true 
gluten. 

Gliadin  Determinations. — It  has  already  been  sliovn  that  gluten 
consists  of  two  protein  bodies  knowui  as  gliadin  and  glutenin,  and  that 
the  former  of  these,  which  is  soluble  in  80  per  cent,  alcohol,  acts  as  the 
binding  and  toughening  agent  in  gluten.  In  a following  chapter  an 
account  is  given  of  percentages  of  protein  in  alcoholic  extracts  of 
flours  ; as  the  protein  thus  extracted  consists  almost  entirely  of  gliadin, 
some  light  is  thrown  on  its  effect  on  the  particular  character  and  quality 
of  the  flours  discussed. 

Viscometric  Gluten  Valuations. — It  being  an  accepted  fact  that  the 
characteristic  elasticity  of  wheaten  flour  is  due  to  the  quantity  and 
quality  of  gluten,  we  are  confronted  with  the  following  problem  : — If 
a spring  American  flour  be  taken  which  yields  46*25  per  cent,  of  'wet 
gluten,  and  has  a viscometer  value  of  67  quarts  per  sack,  it  may  be 
compared  with  a winter  American  flour  containing  27*93  per  cent,  of 
wet  gluten,  and  having  a viscometer  value  of  54*5  quarts  per  sack.  Is 
the  difference  in  absorptive  power  as  registered  by  the  viscometer  due 
entirely  to  the  different  quantity  of  gluten  present  or  partly  to  the 
quality  of  that  gluten  ? As  an  attempt  to  solve  this  question,  various 
flours  "were  taken,  and  their  gluten  and  viscometer  readings  determined. 
The  dry  flours  were  then  mixed  with  different  quantities  of  pure  wheat 
starch  until  they  all  yielded  the  same  percentages  of  gluten  ; visco- 
metric determinations  were  then  made  on  these  mixtures.  The  folio 'sw- 
ing table  gives  the  results  of  such  tests  : — 


THE  STRENGTH  OF  FLOUR. 


299 


“ Viscometer  Determinations  on  Mixtures  of  Flour  and 

Starch. 


1. 

Spring 

Ameri- 

can 

Patent. 

II. 

Winter 

Ameri- 

can 

Patent. 

III. 

Second 

Class 

Winter 

Ameri- 

can 

Bakers. 

IV. 

Hun- 

garian 

Patent. 

V. 

English 

Wheat 

Patent. 

VI. 

British 

MUled 

First 

Patent. 

VII. 

British 

MiUed 

Second 

Patent. 

Original  Percentage  of  Wet 
Gluten 

39-2  1 

28-2 

i 

1 

320 

350 

27-75! 

31-9 

38-4 

Water-absorbing  Power  by 
Viscometer  . , . . 

■ 

68-6 

i 

54-8 

690 

76-0 

61-0 

60-5 

64-0 

Viscometer  Readings,  on 
Gluten  being  reduced  by 
admixture  of  Starch  to 

35  per  cent. 

65-0 

30  „ 

62-7 

1 

1 

7’l’3 

60-0 

63-0 

25  „ 

620 

: 55-5 

66*0 

70-7 

59-5 

20  „ 

Weight  of  Starch  added  to 
100  parts  of  Flour  to 
reduce  Gluten  to  20  per 
cent. 

61-4 

55-4 

620 

66-0 

57-5 

5*7-5 

58*5 

960 

41-0 

600 

75-0 

38-75 

59-5 

92-0 

It  will  be  seen  that  in  the  case  of  the  flours  with  high  water-absorbing 
capacity,  they  still  retain  that  property  on  being  diluted  with  starch  to 
an  uniform  wet  gluten-percentage  level.  Therefore,  so  far  as  wet  gluten 
is  concerned,  it  is  evident  that  not  merely  quantity  but  also  quahty  has 
a direct  influence  on  the  water-absorbing  capacity  of  the  flour.  The 
calculation  of  how  much  starch  has  to  be  added  is  a very  simple  one, 
and  is  best  illustrated  by  an  actual  example  : thus,  taking  the  first  flour 
in  the  table,  we  And  it  yielded  39*2  per  cent,  of  wet  gluten.  If  100 
parts  yield  39*2  per  cent.,  how  much  starch  must  be  added  to  reduce 
the  percentage  to  20  on  the  mixture  ? 

As  20  : 39*2  : : 100  = 

1 : 39*2  : : 5 = 

39*2  X 5 = 196*0,  weight  of  mixture. 

196  — 100  = 96,  weight  of  starch  to  be  added. 

This  calculation  resolves  itself  into  the  simple  one  : 

(Weight  of  wet  gluten  X 5)  — 100  = weight  of  starch  to  be  added. 

In  connection  with  the  stronger  flours,  an  interesting  point  is  the 
bearing  these  experiments  have  on  their  capacity  for  mixing  purposes. 
Such  flours  are  largely  employed  in  connection  with  weaker  flours 
Avhich,  while  used  for  colour  and  flavour,  are  more  allied  to  starch  in 
strength  properties.  Evidence  is  here  given  of  the  comparative  capacity 
these  various  flours  have  of  bearing  such  admixture. 

In  view  of  the  importance  of  true  gluten  estimations  as  a control  on 
those  of  wet  gluten,  a series  of  determinations  made  on  flours  diluted 
with  starch  to  an  uniform  true  gluten  basis  would  be  of  interest. 

Estimation  of  Proteins  Soluble  in  Alcohol. — The  albumins  and 
globulins  of  flour  are  soluble  in  water  and  insoluble  in  alcohol  ; gliadin 
is  insoluble  in  water,  but  soluble  in  80  per  cent,  spirit  ; while  glutenin 
is  insoluble  in  both  reagents  : it  is  therefore  possible  to  make  a proxi- 
mate analysis  of  the  proteins  of  flour  by  determining  proteins  soluble 
in  water,  proteins  soluble  in  80  per  cent,  alcohol,  and  total  proteins. 
Proteins  soluble  in  alcohol  may  be  determined  in  the  follovung  manner  : 


300 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


“ To  10  grams  of  the  flour  in  a flask  add  100  c.c.  of  80  per  cent,  alcohol, 
and  shake  up  thoroughly  : weigh  the  flask  and  contents  on  the  balance, 
and  then  raise  the  alcohol  to  boiling  point  by  immersion  of  the  flask 
in  a hot-water  bath.  Take  out,  re-weigh,  and  if  necessary  make  up, 
loss  of  weight  by  adding  a few  drops  more  alcohol.  Cork  up  and  shake 
vigorously  several  times  while  warm.  Let  the  flask  stand  over  night, 
shake  again  in  the  morning,  allow  to  settle  and  Alter.  Take  20  c.c.  of 
the  flltrate  in  an  acid  flask,  evaporate  to  dryness,  and  determine 
proteins  in  the  usual  manner.  Twenty  c.c  will  contain  the  proteins 
soluble  in  alcohol  of  2 grams  of  the  flour.  The  following  table  contains 
the  result  of  a number  of  estimations  made  in  this  manner,  except 
that  the  alcoholic  solution  was  Altered  hot.  The  results  are  compara- 
tive among  themselves,  but  subsequent  investigation  shows  that  more 
than  the  gliadin  proper  is  held  in  solution  by  the  hot  alcohol  : — 


Proximate  Analysis  of  Proteins  in  Flour. 


Flour. 

Proteins. 

Dry 

Gluten. 

Total. 

Soluble 
in  Water, 
Globulin, 
etc. 

Soluble 

in 

Alcohol, 

Gliadin. 

Insoluble. 

Glutenin, 

1 . Spring  Patent 

2.  Spring  Bakers  . . . . 

3.  Winter  Patent  . . . . 

4.  Winter  Bakers  . . . . 

5.  English  Wheat  Patent 

6.  Hungarian  Patent  . . . . ! 

12-64 

14-95 

8-77 

10-86 

8-78 

11-53 

2-60 

1-58 

1-45 

1-31 

1-38 

1-47 

i 

4-81 

6-08 

3- 63 

4- 43 

4- 33 

5- 27 

5-23 

7-29 

3-69 

5-12 

3- 07  i 

4- 79 

13- 05 

14- 99 

8- 89 
11-00 

9- 15 
11-45 

The  above  table  gives  the  percentage  of  albumin  and  globulin,  and 
also  the  gliadin  : the  glutenin  may  be  obtained  by  difference,  and  is 
given  in  the  fourth  column.  The  few  analyses  made  do  not  afford  suffi- 
cient evidence  on  which  to  generalise  : as  might  be  expected  from  its 
soft,  tenacious  gluten,  the  Hungarian  Patent  contains  a very  high  pro- 
portion of  gliadin.  But  the  Spring  Bakers  , which  is  as  different  a flour 
as  one  can  well  conceive,  contains  still  more  gliadin.  On  the  other  hand, 
the  English  Wheat  Patent,  also  a totally  different  flour,  contains  more 
gliadin  in  proportion  to  its  glutenin  than  does  the  Hungarian  flour.  So 
far  as  percentages  of  gliadin  and  glutenin  are  concerned,  the  Hungarian 
flour  can  be  reduced  to  the  same  condition  as  the  English  by  dilu- 
tion with  starch  ; but  as  shovn  above  (page  298,  Viscometric  Gluten 
Valuations),  such  diluted  Hungarian  flour  behaves  altogether  differently 
to  English  flour.  Further  experiments  on  this  point  are  necessary 
before  absolute  conclusions  can  be  drawn.  More  analytic  data  must 
first  be  accumulated,  and  then  an  interesting  research  should  be  made 
on  the  lines  of  adding  gliadin  and  glutenin  respectively  to  different 
flours,  and  studying  how  far  such  additions  modified  their  characteristics. 
It  would  be  necessary  at  first,  of  course,  to  determine  whether  or  not  the 
processes  themselves,  employed  for  the  extraction  of  these  proteins  from 
flour,  altered  their  essential  properties.’’ 

439.  Gliadin  and  Glutenin  Estimations,  Guthrie.— In  June,  1896,  Guthrie 
made  a communication  on  the  above  subject  to  the  Royal  Society  of  N.S. 
Wales.  He  therein  adopts  the  power  of  absorbing  water  as  his  definition 
of  strength  and  uses  the  term  in  that  sense.  His  strength  results  are  ex- 
pressed in  quarts  of  water  absorbed  by  a sack  of  200  lbs.  The  gluten  was 


THE  STRENGTH  OF  FLOUR, 


301 


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302 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


extracted,  by  careful  and  thorough  washing,  from  a number  of  flours,  and 
then  determinations  of  the  glutenin  and  gliadin  in  the  gluten  were  made 
according  to  the  method  adopted  by  Osborne  and  Voorhees.  Fifty  grams 
of  flour  were  made  into  a dough  with  water,  and  allowed  to  stand  for  one 
hour,  the  gluten  was  then  extracted  and  weighed.  The  still  moist  gluten 
was  then  cut  up  into  very  small  pieces  and  introduced  into  a flask  contain- 
ing 300  c.c.  of  70  per  cent,  alcohol.  The  extraction  of  the  gliadin  was  con- 
tinued for  four  and  a half  days,  the  alcohol  being  replaced  by  fresh  and 
measured  quantities  at  stated  times,  so  that  all  the  glutens  should  undergo 
exactly  the  same  treatment.  The  alcoholic  solutions  of  the  gliadin  were 
evaporated  to  dryness  and  the  gliadin  dried  at  100°  to  constant  weight. 
The  insoluble  glutenin  was  introduced  into  a weighed  dish,  washed  once  with 
alcohol  and  three  times  with  ether,  and  dried  at  100°  to  constant  weight. 

The  foregoing  table  shows  the  results  obtained  : — 

Guthrie  draws  the  following  conclusions  from  these  experiments  : — 

The  strength  or  water- absorbing  capacity  of  a flour  depends  directly  upon 
the  relative  proportion  in  which  the  two  proteins  are  present  in  the  gluten. 

If  the  gluten  contents  of  two  flours  be  nearly  the  same,  that  will  be  the 
stronger  flour  which  contains  the  larger  proportion  of  glutenin. 

Flours  in  wLich  glutenin  preponderates  yield  strong,  tough,  elastic,  non- 
adhesive glutens. 

Increased  gliadin  content  produces  a weak,  sticky,  and  inelastic  gluten 
(Agricultural  Gazette,  N.S.  Wales,  September,  1896). 

44-0.  Gliadin  and  Glutenin  Estimations,  Fleurent. — In  August,  1896,  a 
paper  by  Fleurent  was  published,  in  which  he  stated  that  he  regards  the 
differences  in  properties  of  different  flours  as  being  clearly  marked  by  corre- 
sponding variations  in  the  relative  proportions  of  glutenin  and  gliadin 
present  in  the  flour,  and  suggests  the  following  method  of  examination. 
Gluten  is  washed  out  in  the  usual  manner  from  33*33  grams  of  flour.  The 
mass  is  cut  into  small  pieces,  and  treated  in  a stoppered  bottle  vdth  80  c.c. 
of  alcoholic  potash  (3  grams  of  KHO  per  litre  of  70  per  cent,  alcohol).  In 
order  to  aid  the  solution,  a quantity  of  glass  beads  is  also  added,  and  the 
whole  shaken  at  intervals  until  complete  solution  has  been  effected,  which 
usually  takes  from  36-48  hours.  A current  of  carbon  dioxide  is  next  passed 
through  the  liquid  until  complete  saturation  is  effected,  the  potash  being 
by  this  means  converted  into  the  carbonate  or  acid  carbonate.  The  liquid 
is  next  transferred  to  a graduated  flask  and  made  up  to  110  c.c.  by  the 
addition  of  water.  The  liquid  is  briskly  mixed  and  20  c.c.  drawn  off,  before 
the  solid  matters  have  had  time  to  settle,  and  transferred  to  a tared  dish. 
On  drying  and  weighing  the  residue,  the  quantity  found,  less  the  K2CO3  pre- 
sent, represents  the  total  gluten.  Another  portion  of  the  liquid  is  Altered 
to  remove  the  insoluble  glutenin,  and  20  c.c.  of  the  flltrate  evaporated,  dried 
and  weighed,  in  order  to  determine  the  gliadin.  The  difference  between  the 
gluten  and  gliadin  represents  the  glutenin.  In  case  of  flours  containing 
9 per  cent,  of  gluten  or  over,  it  is  recommended  to  use  150  c.c.  of  alcoholic 
potash  and  make  up  the  treated  solution  to  200  c.c.  On  subjecting  a num- 
ber of  flours  to  this  mode  of  examination,  Fleurent  arrived  at  the  following 
conclusions  : — 

I.  Ignoring  the  actual  percentage  of  gluten,  the  proportions  of  glutenin 
and  gliadin  wliich  are  found  in  flours  giving  the  best  bread-making  results  are 
glutenin,  25  per  cent.  ; gliadin,  75  per  cent,  (ratio,  1:3). 

II.  Flour  in  which  the  ratio  of  glutenin  to  gliadin  is  1 : 4,  develops  well 
during  fermentation ; but  the  dough  again  collapses  and  becomes  compact 
during  baking.  With  such  flour,  the  proportion  of  water  normally  em- 
ployed must  be  reduced. 


THE  STRENGTH  OF  FLOUR. 


303 


III.  When  the  ratio  of  glutenin  to  gliadin  rises  to  1 : 2,  the  flour  becomes 
almost  unworkable  ; the  dough  does  not  develop  either  during  fermenta- 
tion or  baking,  and  the  bread  remains  solid  and  indigestible. 

IV.  A comparison  between  bread  baked  from  flour  conforming  to  the 
standard  laid  down  under  I,  and  that  produced  from  flour  varying  2 per 
cent,  either  way  from  the  typical  value,  reveals  differences  that  are  readily 
perceived  by  an  expert  {Comptes  Rend.,  1896,  123,  755). 

The  method  adopted  consisted  in  first  dissolving  the  whole  of  the  gluten, 
and  then  removing  the  potash  by  its  conversion  into  carbonate,  potassium 
carbonate  being  insoluble  in  strong  alcohol.  On  repeating  FleurenUs 
method,  one  of  the  authors  finds  that  with  alcohol  of  only  70  per  cent, 
strength,  the  potassium  carbonate  is  not  entirely  insoluble.  In  consequence 
it  would  be  expected  that  the  glutenin  would  partly  remain  in  solution. 
In  fact,  Fleurent's  proportions  of  gliadin  are  considerably  higher  than  those 
of  most  other  chemists. 

441.  Identity  of  Proteose  and  Gliadin,  Teller. — ^Por  some  time  there 
had  been  discussion  between  Teller  and  Osborne  as  to  the  nature  of  pro- 
teose. A reference  to  paragraph  218  will  show  Osborne’s  method  of  extract- 
ing proteose.  Teller  sums  up  his  conclusions  as  follows  : The  properties  of 
gliadin  are  such  that  we  would  expect  to  find,  in  the  very  situation  in  which 
they  found  their  “ Proteose,”  small  quantities  of  a body  having  proteose 
reactions,  and  that  no  distinguishing  characteristic  or  reactions  between 
that  “ Proteose  ” and  gliadin  is  known.  The  proteins  of  wheat  are,  then, 
four  : Edestin,  Leucosin,  Gliadin,  Glutenin.  Of  these  edestin  and  leucosin 
are  readily  soluble  in  dilute  solutions  of  common  salt,  but  are  insoluble  in 
dilute  alcohol  ; gliadin  is  slightly  soluble  in  dilute  salt  solutions  and  is  readily 
soluble  in  hot  dilute  alcohol,  while  glutenin  is  insoluble  in  both  of  these 
liquids. 

Teller  further  investigated  the  extent  to  which  the  degree  of  solubility 
of  gliadin  is  affected  by  the  strength  of  the  alcohol  used  as  a solvent.  For  this 
purpose,  extracts  were  made  on  the  same  wheat  meal  with  alcohols  ranging 
from  40  to  95  per  cent,  in  strength,  there  being  a difference  of  5 per  cent, 
of  alcohol  between  each  solvent  and  the  next  stronger.  The  results  were 
as  given,  the  nitrogen  in  the  extracts  being  computed  to  per  cent,  on  the 
one  gram  of  wheat  used. 


strength  of  Alcohol 
in  Per  Cent. 

Per  Cent.  Nitrogen 
in  Extract. 

strength  of  Alcohol 

1 in  Per  Cent. 

Per  Cent.  Nitrogen 
in  Extract. 

95 

0-21 

65 

1-30 

90 

0-31 

60 

1-38 

85 

0-61 

55 

1-40 

80 

0-89 

50 

140 

75 

1-08 

45 

1 40 

70 

1 

M8 

1 

40 

1 40 

i 

Accordingly  alcohol  of  the  specific  gravity  of  0*90  strength,  57*05  per 
cent,  of  alcohol  by  weight,  has  been  adopted  by  him  for  this  solvent  {Agric. 
Expt.  Station,  Arkansas,  Bull.,  No.  53,  September,  1898). 

442.  Gliadin  and  Glutenin  Estimations,  Guess. — In  1600,  Guess  made 
a number  of  estimations  of  these  bodies  in  flour,  and  reported  the  results. 
He  determined  gliadin  and  glutenin,  and  assumed  there  were  present  in 
the  samples  ghadin,  glutenin,  edestin,  leucosin  and  amides. 


304 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Amides  were  determined  separately  by  extraction  of  5 grams  \\dth  one 
per  cent,  salt  solution  in  250  c.c.  flask,  salt  solution  was  added  to  mark,  shaken 
at  intervals  for  an  hour,  allowed  to  stand  for  two  hours,  filtered.  In  100 
c.c.  of  filtrate,  the  proteins  were  separated  by  a few  c.c.  of  10  per  cent,  solu- 
tion of  phospho- tungstic  acid,  filtrated,  50  c.c.  of  the  filtrate  evaporated 
with  sulphuric  acid,  and  the  amide  nitrogen  determined. 

Gliadin. — One  gram  of  the  sample  w^as  digested  with  100  c.c.  of  alcohol 
of  0*90  sp.  gr.  (57*0  per  cent.),  maintained  just  below  alcohol  boiling 
point  for  one  hour,  being  shaken  at  intervals  of  ten  minutes.  Allowed  to 
settle  for  one  hour  and  decanted  into  a flask,  avoiding  carrying  over  any 
turbidity.  The  residue  was  washed  three  times  with  25  c.c.  hot  alcohol, 
allowing  to  settle  for  twenty  minutes  between  each  operation,  and  the 
washings  added  to  the  main  portion  of  solution.  The  alcohol  is  distilled  off 
and  nitrogen  determined  in  residue,  the  amide  nitrogen  is  substracted 
and  the  remainder  calculated  as  gliadin  (N  X 5*7). 

Glutenin. — The  residue  of  the  flour  from  the  gliadin  extraction  is  after 
cooling  treated  with  250  c.c.  by  1 per  cent,  salt  solution,  shaken,  allowed 
to  settle  for  an  hour,  and  filtered  ; 250  c.c.  more  salt  solution  are  added, 
again  shaken  at  intervals  during  one  hour,  allowed  to  settle  for  two  hours, 
and  filtered  through  the  same  Alter.  The  Alter  and  residue  in  the  flask 
are  together  evaporated  to  dryness,  nitrogen  determined  and  calculated 
as  glutenin.  Guess  finds  that  the  elastic  quality  of  the  gluten  was  improved 
as  the  ratio  of  gliadin  to  glutenin  increased,  and  reached  no  limit  beyond 
wLich  an  increase  in  gliadin  w-as  harmful.  He  suggests  as  a valuing  factor 
the  percentage  of  gluten  X ratio  of  gliadin  to  glutenin.  The  following  are 
a few'  of  his  results  : — 


Flour. 

Grade. 

Gliadin 

Per  Cent. 

Glutenin 
Per  Cent. 

Ratio  of 
Gliadin  to 
Glutenin. 

Gluten 

X 

Ratio,  j 

Keew'atin 

Patent 

813 

2-24 

3-62 

37-54 

Bakers’ 

8-47 

3-90 

217 

26-84 

Portage 

Patent 

8-4 

21 

4-0 

42-00 

Bakers’ 

8-65 

2-6 

3-32 

37-25 

Ogilvie’s 

Patent 

8*04 

2-92 

2-76 

30-24 

5 ? • • 

Bakers’ 

74 

3-6 

2*05 

22-55 

Hungarian 

Best  . . 

9-38 

2-80 

3*35 

40-80 

The  wiiole  of  these  flours  except  the  last  w^ere  of  Canadian  manufacture. 
It  will  be  noticed  that  the  percentage  of  gliadin  runs  from  2*17  to  4*0  times 
as  much  as  that  of  glutenin  {Jour.  Amer.  Chem.  Soc.,  1900,  263). 

Amides  are  first  determined  in  order  to  make  the  necessary  corrections 
on  gliadin,  as  they  also  are  soluble  in  alcohol  of  the  strength  employed. 
It  will  be  noticed  that  the  gliadin  is  filtered  and  washed  out  hot.  After 
extracting  the  residual  flour  with  salt  solution,  the  remaining  protein  is 
assumed  to  be  glutenin.  Contrary  to  Fleurent,  Guess  found  without  any 
limit  that  the  more  gliadin  there  w'as  present  the  more  elastic  and  better 
was  the  gluten.  His  valuing  factor  is  based  on  the  view  that  a flour  is 
improved  both  by  the  amount  of  gluten  and  also  the  height  of  the  ratio  of 
gliadin.  His  factor  therefore  embraces  the  both  of  these.  Examination 
of  his  results  show's  that  they  run  fairly  closely  to  those  of  Fleurent,  not- 
withstanding that  their  methods  of  analysis  w'ere  very  different. 

443.  Rapid  Gliadin  Estimations,  Fleurent. — In  HOI,  Fleurent  suggested 
or  the  purpose  of  rapidly  determining  with  approximate  correctness  the 


THE  STRENGTH  OF  FLOUR. 


305 


proportion  of  gliadin  present  in  a flour  the  use  of  a specially  graduated 
densimeter  (hydrometer).  The  instrument  is  furnished  with  two  scales 
reckoned  from  the  same  zero.  The  upper  is  for  the  purpose  of  measuring 
the  density  of  alcohol,  so  as  to  have  it  of  a density  corresponding  to  74  per 
cent,  strength.  The  low'er  is  for  measuring  the  density  of  the  gliadin  solution 
obtained  from  the  flour  by  means  of  this  74  per  cent,  alcohol.  The  dry 
gluten  of  the  flour  must  be  previously  determined,  and  then  a quantity  is 
taken  wiiicli  contains  5 grams  of  dry  gluten.  To  this  is  added  150  c.c.  of 
the  74  per  cent,  alcohol,  and  the  mixture  shaken  and  allow^ed  to  stand  for 
some  time.  The  density  is  then  observed  and  is  read  off  into  amount  or 
percentage  of  gliadin  by  means  of  a table  of  densities  compiled  from  those 
of  flours  in  wLich  the  gliadin  has  been  directly  determined.  Fleurent 
states  that  variations  in  the  gliadin  from  different  flours,  in  the  amount  of 
other  substances  dissolved,  and  in  the  humidity  of  the  flours,  do  not  affect 
the  results  to  an  extent  appreciable  for  the  purposes  of  the  baker  {Comptes 
Rend.,  1901,  122,  1421). 

It  wall  be  observed  that  these  determinations  are  to  be  made  direct  on 
the  flour,  and  in  the  cold.  The  principle  is  that  of  estimating  gliadin  by 
the  density  of  its  solution. 

444.  Effect  of  .Varying  Proportions  of  Starch  on  Fiour,  Snyder. — In  1901, 

Snyder  published  the  results  of  some  experiments  on  the  quality  of  bread 
as  affected  by  increasing  and  diminishing  the  proportion  of  starch  in  the 
flour.  Quantities  of  starch,  equal  to  10  and  20  per  cent,  respectively,  w^ere 
added  to  a strong  flour  containing  12  per  cent,  of  protein.  Baking  tests 
(tin  loaves)  w^ere  made  on  the  mixtures,  and  as  a result  the  WTiter  arrived 
at  the  conclusion  that  wheat  starch  may  be  added  to  a flour  of  this  kind  to 
the  extent  of  20  per  cent,  without  materially  diminishing  the  expansion 
of  the  dough,  and  consequently  decreasing  the  size  of  the  loaf.  The  effect 
of  increasing  the  proportion  of  starch  was  to  lessen  the  water- absorbing 
capacity  of  the  flouf.'^  Converse  experiments  were  made  in  which  the  pro- 
portion of  gluten  w^as  increased, or  more  strictly  that  of  starch  w^as  diminished 
by  removing  some  of  the  starch  from  the  flour.  The  bread  made  from  the 
flour,  having  a low  starch  content  and  a correspondingly  high  gluten 
content,  w^as,  in  appearance,  in  every  respect  hke  normal  bread.  The  size 
of  the  loaf  was  not  materially  affected.  Therefore  it  is  the  character  rather 
than  the  quantity  of  the  gluten  content  w4iich  govern  the  quality  of  the 
bread  {U.S.  Dept,  of  Agric.  Bull.,  101,  56). 

These  results  agree  with  the  conclusions  derived  from  the  viscometer 
determinations  on  mixtures  of  flour  and  starch,  page  298. 

445.  Gluten  Determination,  Arpin. — The  abstract  of  a description  of 
Arpin's  method  of  determining  gluten  is  prefaced  by  the  somewhat  curious 
remark  that  “ although  there  are  numerous  sources  of  error  in  the  separa- 
tion of  the  gluten,  the  valuation  of  a flour  on  the  basis  of  its  content  in 
moist  gluten  has  not  yet  been  suppressed.’"  Arpin  uses  a somewhat  large 
quantity  of  flour  for  his  determinations,  33*33  grams,  and  apparently 
w ashes  out  the  gluten  immediately  on  making  the  dough.  After  w'eighing, 
he  then  dries  for  ten  minutes  at  120°-130°  C.,  cuts  it  up  and  dries  for  ten 
hours  at  105°  C.,  to  constant  w^eight.  He  points  out  that  the  yield  of  gluten 
is  increased  with  an  increase  in  the  temperature  of  the  w^ater  used ; presum- 
ably for  washing).  With  the  same  flour  he  obtained  the  following  results  : — • 

Temperature  of  w'ater  ..  ..  ..  5°  C.  15°  C.  25°  C. 

Moist  Gluten,  per  cent.  . . . . . . 23*98  25*26  26*42 

Dry  Gluten  „ 7*83  8*08  9*24 

In  a subsequent  communication,  Arpin  refers  to  Balland’s  statement 
that  the  yield  of  moist  gluten  increases  with  the  time  the  dough  is  allowed 

X 

f 


306 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


to  stand  before  kneading.  This  is  confirmed  by  an  experiment  of  his  in 
which  as  a result  of  allowing  the  dough  to  stand  for  four  hours  the  yield  of 
moist  gluten  was  increased  by  1*66  per  cent.,  that  of  the  dry  gluten  remain- 
ing unaltered.  The  increase  is  simply  due  to  the  water- absorbing  power  of 
the  gluten  having  become  higher  by  standing.  Another  interesting  point 
is  that  the  yield  of  gluten  increases  with  the  hardness  of  the  water  used, 
this  increase  in  certain  experiments  amounting  to  4*7  per  cent,  of  the  amount 
of  dry  gluten  {Jour.  Soc.  Chem.  Ind.,  1902,  1417  and  1560,  abstracted  from 
Chem.  Centr.,  1902,  2,  1019  and  1347). 

The  connection  between  an  increased  yield  of  gluten  and  hardness  of 
water  has  an  intimate  relation  to  the  solubility  of  ghadin  in  pure  water, 
and  also  may  be  borne  in  mind  when  subsequently  studying  the  results  of 
Wood’s  researches. 

445.  Fermentation  of  Dough,  Parenti. — This  chemist  made  analyses  of 
flour,  and  of  dough  prepared  therefrom,  both  before  and  after  fermentation. 
The  quantity  of  starch  and  of  dextrin  was  found  to  have  suffered  no  altera- 
tion by  fermentation,  but  the  reducing  sugar  was  reduced  to  a trace  or  to 
nil  (from  2*31  to  0*13  per  cent,  was  the  average  reduction  in  four  experi- 
ments). The  amount  of  the  substances  precipitable  by  alcohol  increased, 
however,  from  2*86  to  4*15  per  cent,  on  an  average.  Parenti  found  him- 
self unable  to  obtain  any  gluten  by  washing  the  fermented  dough.  He 
regards  his  results  as  confirming  those  of  Boutroux,  whose  view  is  that 
panary  fermentation  consists  chiefly  in  the  alcoholic  fermentation  of  the 
sugar  in  the  flour  by  the  yeast  added,  and  in  a conversion  of  the  gluten, 
which,  in  breaking  up,  produces  soluble  proteins.  The  origin  of  this  con- 
version he  finds,  not  in  the  yeast,  but  in  an  enzyme  contained  in  the  flour 
{Boll.  Chim.  farmae.,  1903,  42,  353). 

Parenti’s  results  and  conclusions  should  be  compared  with  those  given 
in  paragraph  466,  in  which  the  fermented  dough  was  kneaded  until  free  from 
gas  before  washing  out  the  gluten.  Under  those  circumstances  a consider- 
able amount  of  gluten  is  recoverable  from  the  dough  even  after  excessive 
fermentation. 

446.  Polarimetric  Estimation  of  Gliadin,  Snyder. — Snyder  quotes  the 
following  method  of  Osborne  and  Voorhees  for  the  determination  of  gliadin 
direct  on  flour.  Five  grams  of  the  flour  are  w^eighed  into  a flask,  and  250 
c.c.  of  70  per  cent,  alcohol  added  ; the  flask  is  shaken  at  half-hour  intervals 
for  three  hours.  After  twelve  to  eighteen  hours  the  alcohol  is  filtered  off, 
and  100  c.c.  of  the  filtrate  transferred  to  a Kjeldahl  digestion  flask,  3 c.c. 
of  sulphuric  acid  added,  and  the  contents  evaporated  on  a water  bath,  and 
then  the  nitrogen  determined  in  the  usual  w^ay.  While  recognising  the 
accuracy  of  this  method,  Snyder  recommends  polarimetric  determinations 
as  being  preferable  in  point  of  speed  and  of  sufficient  accuracy  for  technical 
purposes.  The  combined  alcohol-soluble  carbohydrates  and  non-gliadin 
proteins  affect  prolarisation  to  so  slight  an  extent  as  to  be  negligible  for 
practical  purposes.  The  following  is  his  proposed  method.  Weigh  15*97 
grams  of  flour  into  a flask  and  add  100  c.c.  of  70  per  cent,  alcohol.  Shake 
moderately  at  intervals  of  a half-hour  for  two  or  three  hours.  Leave  the 
alcohol  in  contact  with  the  flour  for  from  twelve  to  eighteen  hours,  at  a 
temperature  of  about  20°  C.  Filter,  and  determine  the  opticity  of  the 
solution  in  a 220  m.m.  tube.  Read  off  on  the  sugar  scale,  and  multiply 
by  0*2,  w’liich  gives  approximately  the  per  cent,  of  gliadin.  The  following 
are  comparative  results  obtained  by  the  two  methods : — 


THE  STRENGTH  OF  FLOUR. 


307 


Flours. 

Giiadin  Nitrogen. 

By  Kjeldahl. 

By  Polarimeter. 

Spring  Wheat  Flour 

M2 

MO 

Winter  ,,  ,, 

1-02 

1-04 

1 ,,  Wlieat,  Patent  Flour 

1 

1-28 

1-31 

{Jour.  Amer.  Chem.  Soc.,  1904,  263). 

448.  Commercial  Wheat  Testing,  Snyder. — In  1905,  Snyder  communi- 
cated  a paper  on  this  subject  to  the  American  Chemical  Society  in  which  he 
first  points  out  that  the  percentage  of  proteins  in  a flour  is  not  necessarily  a 
measure  of  its  value  for  bread-making  purposes.  The  following  are  some 
examples  taken  from  the  work  of  the  Minnesota  Agricultural  Experiment 
Station  : — 


Grade  of  Flour. 

Protein  per  cent. 

Commercial  Bank  of 
Loaf. 

First  Patent 

13-19 

1 1 

14-47 

2 

Second  ,, 

14-15 

5 

» ” 

15-32 

9 

The  following  determinations  are  recommended  as  having  given  the 
best  satisfaction  in  flour-testing : Moisture,  ash,  total  nitrogen,  giiadin 
nitrogen,  granulation,  absorptive  capacity,  and  colour. 

Moisture. — Especially  helpful,  as  an  excessive  moisture  content,  above 
13,  has  a tendency  to  induce  fermentative  changes. 

Ash. — The  determination  is  exceedingly  useful  in  establishing  the  com- 
mercial grade  of  flour.  First  and  second  grades  of  patent  flour 
invariably  contain  less  than  0*48  per  cent,  of  ash  ; in  case  a flour  contains 
0*5  per  cent,  of  ash  it  would  not  be  entitled  to  rank  with  the  patent  grades. 
Straight  grade  flour  rarely  contains  more  than  0*55  percent,  of  ash,  while  the 
first  and  second  clear  grades  contain  higher  amounts,  0*8  and  1*75  per  cent, 
respectively. 

Nitrogen  content. — The  best  bread-making  flours  have  a total  nitrogen 
content  of  from  1*8  to  2*1  per  cent.  A lower  figure  than  1*5  per  cent,  indi- 
cates deficiency  in  gluten,  and  poorer  bread.  Flours  containing  an  excess 
over  2*1  do  not  as  a rule  have  improved  bread-making  values,  as  a very  high 
gluten  is  not  beneficial  for  bread-making  purposes. 

Giiadin  Nitrogen. — The  principal  proteins  of  flour  being  giiadin  and 
glutenin,  it  has  been  believed  that  their  ratio  determines  largely  the  value 
of  the  glutinous  material  for  bread-making  purposes.  Snyder  finds,  how- 
ever, that  “ during  some  years  as  high  as  70  per  cent,  of  the  total  nitrogenous 
material  of  wheat  jis  soluble  in  70  per  cent,  alcohol,  while  in  other  years  flour 
from  wheat  grown  under  similar  conditions  contains  as  low  as  45  per  cent, 
of  its  proteins  soluble  in  70  per  cent,  alcohol,  and  that  these  differences 
have  been  associated  with  only  minor  variations  in  the  size  of  the  loaf  or 
general  bread-making  value  of  the  flour.’' 

Snyder  believes  that  the  percentage  of  giiadin  in  a flour  is  of  more  im- 
portance than  the  gliadin-glutenin  ratio.  In  flours  from  the  sam.e  wheat, 


308 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  lower’grades  contain  more  total  protein,  but  proportionately  less  gliadin 
than  the  higher  ones.  He  also  finds  that  any  slight  increase  of  acidity  of 
the  grain  materially  influences  the  gliadin  percentage,  which  factjs  shown 
in  the  following  table  ; — 


Constituents,  etc. 

First 

Patent. 

Flour. 

Second 

Patent. 

1 Clear 

Grade. 

Ash 

. . per  cent. 

0-39 

0-47 

0.84 

Protein 

• • 9 ? 

13-56 

14-70 

7-27 

Gliadin,  of  total  Protein  . . 

• • 99 

59-07 

56-25 

54-21 

Acidity 

• • 99 

0-07 

0-08 

0-12 

Commercial  rank  of  loaf 

I 

II 

1 

III 

Snyder  does  not  find  gliadin  to  be  of  uniform  com^position,  there  being 
as  great  a difference  as  one  or  more  per  cent,  in  the  nitrogen  content  of 
ghadin  from  different  wiieats  milled  under  similar  conditions.  This  sug- 
gests that  gliadin  is  lacking  in  definite  chemical  composition,  possibly  as  a 
result  of  wheat  containing  m^ore  than  one  protein  soluble  in  70  per  cent, 
alcohol.  He  concludes  that  wheat  gliadin  is  not  as  constant  in  chemical 
composition  or  physical  properties  as  would  be  expected  of  a definite  chemi- 
cal compound. 

Granulation. — This  should  be  of  mmdium  fineness  as  such  insures  m-ore 
complete  digestion  and  absorption  of  the  nutrients  of  flour  by  the  body. 

Colour. — This  is  one  of  the  m.ain  factors  in  determining  flour  value,  as 
each  type  of  wheat  has  a tendency  to  produce  flour  of  a distinct  shade. 

Bread-making  Tests. — As  yet  chemical  tests  are  not  capable  of  accurately 
determining  the  bread-making  value  of  a flour.  They  often  indicate,  how- 
ever, why  a flour  is  deficient  in  desirable  bread-making  characteristics,  and 
from  the  chemical  tests  ways  are  suggested  for  improving  the  flour,  but  the 
actual  bread-making  value  can  be  determined  only  by  comparative  bread- 
n:aking  tests.  These  give  accurate  data,  including  absorptive  capacity 
and  consequent  yield  {Jour.  Amer.  Chem.  Soc.,  1905,  1068). 

With  an  excess  of  nitrogen  the  gluten-bound  condition  before  referred 
to  comes  into  operation.  The  abstract  of  this  paper  is  purposely  introduced 
here  because  of  the  strong  expression  of  opinion  as  to  effect  of  the  ratio  of 
gliadin  to  glutenin  on  the  quality  of  a flour.  Snyder’s  authoritative  state- 
mient  as  to  variations  in  the  composition  of  ghadin  also  deserves  careful 
attention.  It]  should  be  compared  with  those  following  of  Osborne  and 
Wood,  paragraphs  449  and  453.  Snyder  ultimately  falls  back  on  the  baking 
test  as  most  accurately  determining  the  bread-making  value  of  a flour. 

449.  Gliadin,  Osborne  and  Harris. — In  reply  to  Kutscher’s  statement 
that  the  protein  matter  of  wheat,  soluble  in  70  per  cent,  alcohol,  consists 
of  two  separate  proteins,  the  authors  have  fractionally  precipitated  the 
protein  matter  and  find  all  the  fractions  yield  practically  the  same  amount 
of  glutamic  acid.  They  therefore  come  to  the  conclusion  that  taking  into 
consideration  the  composition  and  the  physical  and  chemical  properties 
of  the  protein,  that  only  one  such  substance  is  present  in  gluten,  and  this, 
substance,  gliadin,  does  not  consist  of  two  separate  proteins  {Z.  Anal.  Chem. 
1905,  44,  516). 

This  is  not  a specific  reply  to  Snyder’s  statement  as  to  variations  in  the 
composition  of  gliadin  from  various  sources. 


THE  STRENGTH  OF  FLOUR. 


309 


450.  Crude  Gluten,  Norton. — Norton  has  made  a very  full  analysis  of 
crude  gluten  as  obtained  from  durum  flour.  The  gluten  was  washed  out, 
partly  dried,  flnely  ground  and  again  dried  until  it  ceased  to  lose  weight  at 
100°  C.  On  analysis  it  then  gave  the  following  results  : — 


Fats  or  ether  extract  . . 
Carbohydrates  other  than  flbre 
Fibre 

Mineral  Matter  . . 

Gliadin 
Glutenin  . . 

Globulin,  10  per  cent.  NaCl  extract 


4.20  per  cent. 


9-44 
2-02 
2*48 
39-09 
35-07  ’ 
6-75 


99-05 

The  gliadin  was  first  removed  from  the  gluten  by  alcohol,  the  residue 
was  then  extracted  with  10  per  cent,  sodium  chloride  solution  for  globulin, 
and  the  residue  Anally  extracted  with  0-2  per  cent,  potassium  hydroxide. 
Nitrogen  was  determined  in  each  extract  and  multiplied  by  5-7  for  protein. 
From  the  above  analysis,  crude  gluten  may  be  regarded  as  consisting  of 
about  75  per  cent,  of  true  gluten  (gliadin  and  glutenin)  together  with  other 
matters  as  indicated,  and  which  include  approximately  7 per  cent,  of  non- 
gluten protein  matter. 

In  summarising  his  results,  Norton  points  out  that  the  crude  gluten  of 
flours  is  very  close  in  amount  to  that  of  total  protein  (N  X 5-7),  the  varia- 
tion being  in  a number  of  samples  from  an  excess  of  crude  gluten  of  2-31, 
to  a deficit  of  1 *30.  As  a rule  the  crude  gluten  is  the  higher  for  straight  and 
low  grade  flours,  nearly  the  same  for  patents,  and  less  for  wLole  wheat  meal. 
It  follows  that  crude  gluten  is  a body  in  which  there  has  been  a loss  of  non 
gluten  proteins,  more  or  less  balanced  by  the  retention  of  non-protein 
matters.  Crude  gluten  is  a very  rough  expression  of  the  gluten  content  of 
a flour  or  wheat,  and  the  determination  has  but  little  worth  in  the  valuation 
of  flours.  The  determination  of  total  nitrogen  and  gliadin-nitrogen  with 
expression  of  the  ratio  of  ghadin  to  total  protein  (N  X 5-7)  seems  to  be  the 
best  simple  method  at  hand  for  estimating  the  gluten  content  and  ascer- 
taining the  character  of  the  gluten  in  the  valuation  of  wheats  or  flours  (Jour. 
Amer.  Chem.  Soc.,  1906,  8). 

Any  review  of  opinions  as  to  the  value  of  gluten  determinations  is  best 
postponed  until  a later  stage.  Meantime,  the  results  of  a very  complete 
analysis  of  crude  gluten  is  here  placed  on  record.  The  most  noticeable 
feature  is  the  retention  of  6-75  per  cent,  of  globulin,  a non-gluten  protein. 
The  comparative  purity  of  crude  gluten  must  depend  somewhat  on  the 
thoroughness  of  the  washing  treatment  ; it  will  be  observed  that  in  the 
1895  edition  of  this  work  about  80  per  cent,  of  crude  gluten  is  assumed  to 
be  true  gluten.  This  was  determined  by  a direct  nitrogen  estimation  and 
substantially  agrees  with  the  sum  of  gliadin,  glutenin,  and  globulin  found 
by  Norton. 

451.  Polarimetric  Estimation  of  Gliadin,  Matthewson. — In  view  of  the 
fact  that  it  has  been  proposed  to  estimate  ghadin  both  by  polarimetric 
readings  and  also  by  density  determinations  of  its  alcoholic  solution,  Matthew- 
«on  has  investigated  the  extent  to  which  the  degree  of  accuracy  of  these 
methods  is  affected  by  the  variations  which  may  occur  in  practice.  He 
arrives  at  the  following  conclusions  ; The  specific  rotation  of  ghadin  in 
70  to  75  per  cent,  alcohol  is  practically  independent  of  the  ghadin  concen- 
tration. With  70  to  80  per  cent,  alcohol  it  decreases  with  increase  in 
the  alcohol  concentration.  Increase  in  temperature  between  the  limits 
20-45°  C.  produces  a shght  increase  in  the  specific  rotation.  The  change  in 


310 


THE  TECHNOLOGY  OF  BREAD -MAKING. 


density  in  gliadin  solutions  for  such  differences  as  would  be  met  with  in  flour 
analysis  would  allow  rather  a narrow  margin  for  experimental  error.  Thus 
solutions  of  gliadin  in  70  per  cent,  alcohol  had  the  following  densities  : — 

Grams  of  Gliadin  per  cent.  Density. 

0-000000  0-8686 

0-004795  ■ 0-8702 

0-05390  0-8865 

Matthewson  therefore  concludes  that  if  density  of  the  solution  be  rehed 
on,  there  are  disturbing  causes  which  could  easily  vitiate  the  results  (Jour, 
Amer.  Chem.  Soc.,  1906,  624). 

Matthewson  confirms  the  accuracy  of  the  polarimetric  method  of  gliadin 
estimation,  but  condemns  that  based  on  the  density  of  its  solutions.  The 
following  is  an  abstract  of  an  important  paper  on  wheat  proteins. 


452.  Properties  of  Wheat  Proteins,  Chamberlain. — Chamberlain  has 
invertigated  various  methods  of  making  gliadin  and  other  protein 
determinations  in  wheat  and  flour,  and  gives  the  following  results  : — 

Action  of  hot  alcohol. — Experiments  on  the  direct  extraction  of  flour  were 
made  with  70  per  cent,  alcohol  in  order  to  see  if  hot  alcohol  would  dissolve 
out  more  protein  than  cold,  with  the  following  results  : — 


Cold  Alcohol  on  Air-dry  Flour 
Hot 

Cold  „ ,,  Dry  Flour 


Protein 

Protein 

per  cent. 

per  cent,  of 

of  Flour. 

Total  Proteins. 

7*47  . 

. 56-80 

7*32  . 

. 54-43 

4-58  . 

. 34-82 

The  use  of  hot  alcohol,  and  also  the  practice  of  drying  the  flour  before 
extraction,  both  result  in  lessening  the  amount  extracted — an  effect  pro- 
bably due  to  the  coagulating  effect  of  heat. 

Effect  of  different  proportions  of  flour  and  extracting  liquid. — Tw^o  series 
of  extractions  were  made.  In  the  first,  1,000  grams  of  flour  were  extracted 
with  4,000  c.c.  of  70  per  cent,  alcohol,  followed  by  subsequent  extractions 
using  2,000  c.c.  of  alcohol  each  time,  until  a total  amount  of  10,000  c.c.  had 
been  used.  (Total  equals  10  c.c.  of  alcohol  to  1 gram  of  flour).  In  the  next 
place  2 to  4 grams  of  flour  were  extracted,  once  with  100  c.c.  of  alcohol  (25 
to  50  c.c.  of  alcohol  to  1 gram  of  flour).  With  the  larger  quantity  of  flour, 
the  alcohol  extracted  43-56  per  cent,  of  the  total  proteins,  and  with  the 
smaller  proportion  of  flour,  47*15  per  cent. 

In  some  further  experiments  flour  was  extracted  by  70  per  cent,  alcohol 
and  10  per  cent,  salt  solution  in  the  ways  and  wdth  the  results  given  in  the 
following  table  : — 


Modes  of  Extraction. 

Protein 
per  cent, 
of  Flour. 

Protein 
per  cent,  of 
Total  Proteins. 

Direct  extraction  w ith  Alcohol 

Extraction  with  Salt  Solution  after  pre- 
ceding Extraction  with  Alcohol 

Direct  Extraction  with  Salt  Solution 
Extraction  with  Alcohol  after  preceding 
Extraction  with  Salt  Solution  . . . . j 

1 

1 

7*47) 

8-04 

0-57j 

2-18) 

7*68 

5-50  J 

56-80) 

[61-13 
4-33  j 

16-57) 

[55-83 
39-26 j 

When  flour  is  acted  on  direct  with  salt  solution,  the  albumin,  globulin, 
and  proteose  are  extracted.  The  salt  remaining  in  the  flour  affects  the 


THE  STRENGTH  OF  FLOUR. 


311 


solubility  of  the  other  proteins,  and  consequently  there  is  not  such  a high 
degree  of  extraction  by  alcohol  as  where  that  reagent  is  employed  direct. 
But  when  alcohol  is  first  employed  and  the  flour  is  carefully  freed  from  it 
before  the  subsequent  extraction  with  salt  solution,  it  would  be  expected 
that  the  yield  to  the  salt  solution  would  be  the  same  as  with  a direct  extrac- 
tion. Such,  however,  is  not  the  case,  for  whereas  salt  solution  direct  ex- 
tracted 16*57  per  cent,  of  the  proteins,  it  only  extracted  4*33  per  cent,  when 
used  after  alcohol.  ‘‘This  can  mean  only  one  thing,  viz.  that  alcohol  dis- 
solves, with  the  gliadin,  a large  part  of  the  albumin,  globulin,  and  proteose, 
which  are  soluble  in  salt  solutions.''  It  is  probable  that  of  these  it  dissolves 
the  albumin  and  proteose  and  leaves  the  globulin.  Chamberlain  arrives 
at  tlie  following  conclusions  : — 

1.  For  the  proper  extraction  of  the  proteins  of  wheat  by  means  of 
of  alcohol,  cold  70  per  cent,  alcohol  should  be  used  directly  upon  the 
air-dry  wheat  or  flour.  Relatively  large  amounts  of  solvent,  in  proportion 
to  the  flour,  should  be  taken,  viz.  2 to  4 grams  flour  per  100  c.c.  alcohol,  and 
the  extraction  continued  for  twenty-four  hours  with  frequent  or  continuous 
shaking.  Either  hot  alcohol  or  dry  flour  gives  abnormal  results. 

2.  The  same  conditions  of  extraction  should  be  observed  in  using  the 
salt  solution,  4 to  6 grams  being  taken  to  the  100  c.c.  of  solvent.  Five  per 
cent,  potassium  sulphate  solution  extracts  practically  the  same  as  10  per 
cent,  sodium  chloride  and  is  better  in  practice,  because  it  avoids  the  evolu- 
tion of  hydrochloric  acid  gas  when  digested  in  the  Kjeldahl  operation. 

3.  Alcohol  extracts  together  vdth  gliadin  a large  part  of  the  salt-soluble 
proteins. 

Chamberlain  agrees  vdth  the  conclusions  arrived  at  by  Norton,  para- 
graph 450,  and  confirms  them  by  an  examination  of  the  protein  material 
lost  in  the  washing  out  of  gluten,  and  contained  in  the  wash-water  there- 
from. From  the  results  of  this  investigation,  he  comes  to  the  following 
conclusions  : — 

1.  Dry  gluten  is  about  75  per  cent,  proteins  and  25  per  cent,  non-pro- 
teins. 

2.  Of  the  total  proteins  present  in  wheat  about  60  to  65  per  cent,  are 
present  in  the  gluten,  and  about  35  to  40  per  cent,  are  lost  in  the  washings. 

3.  The  balance  between  non-proteins  present  in  gluten  and  the  loss  of 
proteins  in  washing,  makes  gluten  estimations  agree  roughly  with  total 
proteins  calculated  from  total  nitrogen,  but  they  wall  usually  fall  below 
with  whole  wheat  and  above  with  flours. 

4.  The  amount  of  total  proteins  present  in  gluten  is  about  15  per  cent, 
less  than  the  sum  of  the  gliadin  and  glutenin  determined  by  extraction  of 
the  wheat,  and  the  loss  of  proteins  in  washing  out  gluten  is  more  than  equal 
to  the  salt  solution-soluble  proteins.  Therefore  the  loss  of  proteins,  in  the 
determination  of  gluten,  is  at  the  expense  of  gliadin  or  glutenin,  the  true 
gluten  proteins  of  wheat. 

5.  On  account  of  these  losses  and  errors  it  would  seem  that  the  deter- 
mination of  gluten  is  not  able  to  yield  any  information  that  cannot  be  gained 
either  from  the  determination  of  total  proteins  or  that  of  the  alcohol-soluble 
and  insoluble  proteins  {Jour.  Amer.  Chem.  Soc.,  1906,  1657). 

Chamberlain's  conclusions  are  principally  of  value  as  throwing  light  on 
methods  of  analysis.  They  go  also  to  show  that  the  alcohol  extract  of  flour 
is  not  pure  gliadin. 

453.  The  Chemistry  of  Strength  of  Wheat  Flour,  Wood. — There  comes 
next  in  chronological  order  the  account  of  Wood's  researches.  This  subject 
has  been  dealt  with  in  papers  pubhshed  by  Wood  in  the  Journal  of  Agri- 
cultural Science,  of  which  the  following  are  abstracts.  The  authors  are 


312 


THE  TECHNOLOGY  OF  BHEAH-MAKING. 


indebted  to  the  courtesy  of  Professor  Wood  for  copies  of  these  and  other 
valuable  papers. 

The  earlier  paper  commences  vdth  a discussion  of  the  definition  of 
Strength,  and  finally  the  writer  adopts  that  given  by  one  of  the  authors 
as  above  quoted,  and  also  chosen  by  Humphries  and  Biffen  in  their  paper 
quoted  supra.  Reference  is  made  to  the  connection  between  strength 
and  gluten,  and  especially  to  the  effect  caused  by  the  presence  of  a proper 
proportion  of  ghadin  to  glutenin.  It  is  held  as  proven  that  neither  the 
absolute  percentage  of  gliadin  in  the  flour,  nor  the  ratio  of  gliadin  to  total 
protein  gives  satisfactory  indications  of  strength.  It  was  therefore  thought 
possible  that  gliadin  might  be  a mixture  of  different  proteins,  or  at  any  rate 
the  ghadin  of  strong  flours  might  differ  from  that  of  weak  flours.  Accord- 
ingly Wood  made  a series  of  determinations  on  the  gliadins  of  strong  and 
weak  flour  by  Osborne  and  Harris"  method  of  hydrolysis  by  hydrochloric 
acid,  and  proved  the  ghadin  of  both  to  be  the  same  in  chemical  composition. 
Among  others  examined  three  flours  gave  results  as  under  : — 


Source  of 
Gluten. 

Bakers’ 

Percentage  in  Flour. 

Percentage 

Gliadin 

Percentage 
of  Nitrogen 

Reference 
Letter  of 
Flour. 

Marks 
of  Flour. 

Total 

Nitrogen. 

Gliadin 

Nitrogen. 

Nitrogen 
of  total 
Nitrogen. 

found  in 
Gluten 
Samples. 

D 

95 

1-69 

1-01 

60 

130 

E 

80 

2-44 

1-23 

50 

121 

C 

40 

1 

1-86 

101 

54 

12-2 

Examination  of  this  table  shows  that  neither  the  percentage  of  total 
nitrogen,  nor  of  ghadin,  nor  the  ratio  of  ghadin  in  glutenin,  can  be  taken 
as  a measure  of  the  strength  of  flour.  Thus  T>  and  E,  which  are  at  the 
extreme  ends  of  the  scale  of  strength,  are  strikingly  similar  in  nitrogen  and 
protein  composition. 

Attention  was  next  directed  to  the  water-soluble  constituents  of  different 
flours.  Acidities  were  first  determined  and  found  to  have  no  relation 
to  strength.  Estimations  were  then  made  of  total  soluble  matter,  soluble 
ash,  potash,  and  phosphoric  acid.  The  results  of  such  tests  are  set  out  in  the 
following  table  : — 


Reference 

Letter 

of 

Flour. 

1 

Bakers’ 

Marks. 

Total 
per  cent. 
Nitrogen 
in  Flour. 

^ Percentages  of  Soluble  Constituents  in  Flour. 

Total 

Solids. 

Ash. 

Nitrogen. 

Alkali 

as 

K2O. 

Phosphoric 

Acid, 

P2O5. 

j Nitrogen 
and  Ash- 
1 free 

Extract. 

K 

95 

1-88 

7-18 

0-194 

0-506 

0-067 

0-048 

4-11 

G 

(75) 

2*32 

4-67 

0-261 

0-378 

0-113 

0-079 

2-26 

I 

70 

L62 

616 

0-360 

0-370 

0-137 

0-091  i 

3-70 

J 

66 

1-32 

5-82 

0-241 

0-308 

0-109 

0-075  j 

3-82 

1 C 

. 40 

1-88 

4-23 

0-243 

0-353 

0-087 

0-074  i 

1 

1-98 

The  ratios  of  soluble  ash,  alkali,  phosphoric  acid,  and  nitrogen  and  ash- 
free extract,  to  nitrogen  are  set  out  as  follows  : — 


THE  STRENGTH  OF  FLOUR. 


313 


Kefer<"nce 
Letter 
of  Flour. 

1 

1 

1 

Bakers’ 
Marks.  | 

1 

Ratios  to  Nitrogen  of  Soluble 

Ash. 

Alkali  as 
K2O. 

Phosphoric 

1 Aci.1,  P2O5. 

! Nitrogen  and  Ash- 
free Extract. 

K 

95 

9-7  1 

39 

39 

0-45 

G 

(75) 

8-8  * 

28 

29 

102 

I 

70  j 

4-5 

16 

18 

j 0-44 

J 

66 

5-5 

16 

18 

j 0-34 

C i 

1 

40 

7-7 

29  I 

25 

0*91 

In  these  ratios,  the  figure,  9*7  for  example,  means  that  there  is  9*7 
times  as  much  nitrogen  present  in  the  flour  as  there  is  of  ash.  Examination 
of  these  data  shows  that  the  higher  the  nitrogen  or  proteins  in  the  flour  is 
in  proportion  to  the  soluble  ash,  the  greater  is  the  strength  of  flour.  But 
to  this  C is  an  exception,  since  the  ratio  is  very  high,  though  the  strength 
is  low.  If  instead,  the  nitrogen  and  ash-free  extract,  which  may  be  re- 
garded as  carbohydrate  matter,  sugars  and  dextrin,  be  taken  both  G and 
C are  exceptions.  [For  convenience  the  soluble  carbohydrates  may  be 
termed  “ sugars,”  since  these  are  doubtless  the  effective  constituents.  The 
authors.]  In  these  flours  the  nitrogen  and  “ sugars  ” are  practically  equal, 
while  in  the  others  there  are  between  two  and  three  times  as  much  sugars 
as  nitrogen.  Wood  remarks  that  “ the  stronger  flours  contain  more  total 
nitrogen  in  proportion  to  their  soluble  salt  content  than  the  w^eaker  ones, 
but  to  this  regularity  G and  C are  exceptions.”  [It  is  difficult  to  see  how 
the  position  of  G agrees  with  this  statement,  since  it  seems  to  fall  fairly 
regularly  into  line.  G is  in  fact  marked  by  a high  percentage  of  nitrogen 
(and  protein)  coupled  with  a low  percentage  of  “ sugars,”  and  C also  pos- 
sesses the  same  characteristics  ; and  one  is  a strong  and  the  other  a weak 
flour.] 

Dealing  with  this  flour  G,  Wood  remarks  of  its  baking  properties  that 
it  will  not  make  large  loaves  when  baked  by  itself,  but  when  blended  with 
certain  other  flours  it  behaves  as  if  it  possessed  great  strength.  This  he 
regards  as  an  indication  of  two  distinct  factors,  one  probably  governing  the 
shape  of  the  loaf,  the  other  its  volume.  The  first  would  be  the  ratio  of 
soluble  salts  to  total  protein,  or  at  any  rate  some  factor  which  modifies 
the  physical  properties  of  the  protein.  This  is  governed  by  the  amount 
of  nitrogen  and  ash-free  extract,  “sugars,”  present  in  the  flour.  K contains 
high  protein  and  high  “ sugars,”  the  former  being  subjected  to  suitable 
conditions.  I and  J are  weaker  as  they  contain  less  protein,  and  a higher 
proportion  of  ash,  while  the  sugars  are  also  lower.  In  G the  conditions 
of  good  shape  are  fulfilled,  since  the  protein  is  high,  and  its  condition  of 
environment  probably  good,  but  it  cannot  make  large  loaves  because  of 
the  low  percentage  of  “ sugars  ” present.  C has  high  protein,  but  low 
“ sugars  ” ; and  an  ash  figure  which  lies  betw^een  those  of  K and  G. 

Having  separated  strength  into  at  least  two  independent  factors,  those 
of  shape  and  volume.  Wood  further  investigated  the  volume  factor.  For 
this  purpose  G was  compared  with  L,  a flour  from  the  same  kind  of  wheat 
grovm  in  the  following  year.  The  nitrogen  of  the  two  flours  closely  approxi- 
mated, so  also  did  the  ratio  of  soluble  ash  to  proteins,  but  L contains  more 
than  twice  as  much  “sugars.”  The  latter  flour  yielded  large  loaves  of 
good  shape. 

Wood  next  proceeds  to  explain  that  some  form  or  forms  of  sugar  are 
the  active  ingredient  of  his  nitrogen  and  ash-free  extract,  and  proceeded 


314:  THE  TECHNOLOGY  OF  BREAD-MAKING. 

to  make  an  indirect  determination  of  the  amount  in  a number  of  flours 
by  fermentation  tests.  He  took  20  grams  each  of  flour  and  water,  and 
0-5  gram  of  yeast  and  fermented  at  35°  C.  in  an  apparatus  similar  to  that 
described  in  paragraph  364  of  this  book.  The  fermentation  was  allowed 
to  proceed  for  24  hours  and  the  volume  of  gas  was  then  observed.  The 
actual  amount  of  gas  evolved  ranged  from  131  to  345  c.c.  The  results 
are  set  out  in  the  follovung  table  : — 


Eeference 
i Letter  of 

' Flour. 

1 

Bakers’ 

Marks. 

Volume  of 
CO2  evolved 
(S  = 100). 

Percentage 
total  Sugar 
in  Flour 
calculated 
as  Glucose. 

Increase  in 
Sugar  after 
incubating  three 
hours  with 
Water  at  40°  C. 

Volume  of  | 

Loaf  made  1 

from  100  grams  ^ 

Flour 

fS  = ioo).  : 

s 

85 

ICO 

2-3 

2-7 

ICO 

p 

90 

1 94 

2-6 

0-6 

85 

0 

96 

! 90 

■ — * 

— 

80  i 

1 L 

85 

88 

2-5 

— 

88 

1 T 

(20) 

83 

1-8 

0-4 

81 

' M 

73 

79 

2-0 

0-6 

78  - ■ 

! N 

(96) 

77 

2-2 

0-4 

— 

Q 

68 

66 

2-5 

0-5 

— 

G2 

(85) 

64 

— ' 

— 

76 

G3 

(85) 

62  1 

— 

— 

76 

R 

65 

60  ! 

1-9 

0-3 

70  i 

J 

63 

59 

— 

■ — 

60  1 

C 

40 

48  ; 

— 

— 

V 

45 

45  1 

1-7 

01 

— j 

U2 

60 

45 

— 

— 

67 

G 

(75) 

44  I 

1-6  1 

— 

— ! 

U 

36 

37 

1-6 

1 

04 

The  figures  in  this  table  are  self-explanatory,  except  that  it  may  be 
pointed  out  that  the  highest  volunie  of  carbon  dioxide  evolved  has  been 
taken  as  100,  and  the  others  calculated  in  proportion.  The  same  thing 
has  been  done  with  the  volum^e  of  the  loaf.  The  fifth  column  giving  increase 
of  sugar  is  apparently  the  result  of  independent  experiments. 

Generally  speaking,  there  is  a general  relation  between  the  strength  of 
the  flour  as  shown  by  bakers'  marks,  and  the  volume  of  carbon  dioxide 
evolved  during  fermentation.  But  to  this  general  rule,  flours  T,  N,  and 
G are  exceptions.  An  investigation  of  these  showed  that  G was  deficient 
in  sugar,  and  that  Avhen  sugar  was  added  it  was  found  to  give  a large  loaf. 
N had  had  malt  extract  added  to  it  when  baked,  and  thus  also  its  deficiency 
in  sugar  had  been  made  up.  T had  been  kept  some  time  after  baking, 
and  in  the  interval  had  probably  developed  sugar  or  sugar- producing 
bodies.  A subsequent  baking  showed  a marked  improvement  in  strength. 
From  these  experiments  Wood  reasons  that  they  “ seem  to  justify  the 
conclusion  that  the  capacity  of  a flour  for  giving  off  gas  when  incubated 
with  yeast  and  water  is  the  factor  which  in  the  first  instance  determines 
the  size  of  the  loaf."  Particular  attention  should  however  be  paid  to  the 
rate  of  gas  evolution  in  the  later  stages  of  fermentation,  as  this  is  shown 
to  be  more  directly  connected  with  the  size  of  the  loaf.  {Wood,  Journ. 
Agric.  Science,  1907,  2,  139). 

The  suggestion  in  this  paper  that  strength  runs  parallel  with  percentage 
of  sugar  is  somewhat  contrary  to  the  hitherto  generally  accepted  views. 
Thus  the  descriptions  “ a weak  sweet  flour,"  and  “ a strong,  harsh,  dry 


THE  STRENGTH  OF  FLOUR. 


315 


flour  are  very  familiar.  A reference  to  the  1895  edition  of  the  present 
work  shows  (page  291)  that  No.  2 Calcutta  yields  8*34  per  cent,  of  soluble 
extract,  and  (page  339)  that  the  loaf  is  small  and  runny,  devoid  of  texture, 
and  foxy.  On  the  other  hand  reference  (page  292)  shows  that  a sample 
of  No.  1 American  Hard  Fyfe  Wheat,  yielded  4*35  per  cent,  of  soluble 
extract,  while  the  corresponding  Spring  American  patent  flour  (page  338) 
yielded  a loaf  which  was  very  bold  and  of  good  texture,  but  with  a ten- 
dency to  become  somewhat  rapidly  harsh  and  dry,  and  comparatively  flavour- 
less. (The  following  are  the  corresponding  references  in  the  present  edition 
— 291,  276  ; 339,  373  ; 292,  277  ; 338,  372.  No  determinations  were  made  of 
sugars,  but  it  is  practically  certain  that  they  rise  and  fall  with  the  total  soluble 
extract.  In  paragraph  450  an  account  is  given  of  some  investigations  of 
durum  wheat  by  Norton.  He  there  remarks  that  though  all  the  durum 
flours  have  high  gluten  and  sugar  contents,  yet  the  bread  from  many  of 
the  poorer  durum  wheat  flours  neither  rises  during  the  fermentation  nor 
in  the  oven. 


454.  Effect  of  Sugar  on  Flour — An  interesting  side-light  is  thrown  on 
the  effect  of  the  presence  of  sugar  in  flour  by  the  following  experiments. 
In  sweet  biscuit  doughs  it  is  well-known  that  the  physical  condition  of 
the  dough  is  materially  affected  by  the  presence  of  the  sugar.  Thus  a 
dough  made  from  100  grams  of  flour  and  50  grams  of  water  is  much  stifler 
than  one  made  from  100  grams  of  flour,  20  grams  of  sugar,  and  50  grams  of 
water,  the  latter  being  soft  and  sticky.  For  example,  with  such  doughs, 
when  tested  with  the  viscometer,  the  following  results  were  obtained.  In 
order  that  the  sugar  dough  should  register  equally  the  water  had  to  be 
reduced  to  shghtly  less  than  40  grams  thus : — 


I.  Flour  100,  water  50  . . 

II.  Flour  100,  sugar  20,  water  50 

III.  Flour  100,  sugar  20,  water  48 

IV.  Flour  100,  sugar  20,  water  46 

V.  Flour  100,  sugar  20,  water  44 

VI.  Flour  100,  sugar  20,  water  42 

VII.  Flour  100,  sugar  20,  water  40 

VIII.  Flour  100,  sugar  20,  water  38 
for  the  half  descent  of  the  viscometer  piston. 


Viscometer  Time. 

106  seconds. 

9 

16  „ 

28  „ 

50  „ 

64  „ 

86  „ 

364 


In  view  of  these  facts,  tests  were  made  on  behalf  of  a firm  of  biscuit 
manufactureis,  and  communicated  to  them  by  one  of  the  authors  in  1902. 
Particulars  of  the  flours  are  given.  The  sugar  was  supplied  by  the  firm  in 
question  and  gave  the  following  results  on  analysis : — 

Cane  Sugar  from  opticity  . . . . . . 98*45  per  cent. 

Reducing  Sugar  as  Glucose  . . . . . . 0*80  ,,  ,, 

Water  . . . . . . . . . . . . 0*10  ,,  ,, 

Mineral  matter  . . . . . . . . . . 0*04 


I.  Doughs  were  made  with  flour  A and  B.  The  wet  and  dry  gluten 
were  determined  by  washing  and  drying ; the  true  gluten  by  a Kjeldahl 
estimation  on  dry  gluten ; gliadin  by  dissolving  the  wet  gluten  with  70 
per  cent,  alcohol,  filtering  and  Kjeldahl  estimation  on  the  filtrate  ; glutenin 
by  subtracting  gliadin  from  the  true  gluten. 

II.  Doughs  were  made  from  100  parts  of  flour  and  20  parts  of  sugar 
(sugar-dough).  The  gluten  was  washed  out  with  water,  and  weighed 
wet  and  dry.  True  gluten  was  determined  as  before.  Gliadin  was  deter- 
mined by  dissolving  wet  gluten  with  70  per  cent,  alcohol,  containing  to 
100  parts  of  alcohol,  20  parts  of  sugar  (sugar-spirit),  filtering,  and  a Kjeldahl 


316  THE  TECHNOLOGY  OF  BREAD-MAKING. 

estimation  in  the  filtrate;  glutenin,  by  subtracting  gliadin  from  true 
gluten. 


Constituents. 

A. 

B. 

Ordinary, 

Sugar-dough. 

i 

Ordinary. 

Sugar-dough. 

1 

i 

Gluten,  wet  . . . . 

37*2 

35-9 

26-7 

23-9 

! „ dry 

11-3 

11-7 

8-2 

7-7 

,,  true 

10-4 

100 

7-5 

7-2 

Gliadin  ex  Gluten  . . ' 

3-6 

7-2 

30 

5-6 

Glutenin  . . 

6-8 

2-8 

4-5 

1-6 

In  all  cases  the  sugar  caused  a diminution  of  the  quantity  of  gluten 
recovered,  except  in  the  case  of  the  dry  gluten  of  flour  A.  When  extracted 
with,  alcohol,  much  more  of  the  gluten  was  dissolved  by  the  sugar-spirit, 
than  the  ordinary  alcohol,  showing  that  sugar  has  a marked  solvent  action 
on  wet  gluten.  (As  all  these  gliadin  determinations  were  made  in  the  pre- 
sence of  excess  of  carefully  washed  precipitated  chalk,  CaCOg,  there  could 
have  been  no  free  acid  present.) 

In  the  next  place,  the  total  protein  of  the  flours  w^as  directly  estimated 
by  Kjeldahl’s  method.  The  proteins  soluble  in  water  were  determined 
by  directly  treating  the  flour,  filtering  and  Kjeldahl’s  process  on  the  filtrate. 
The  proteins  extracted  by  a 20  per  cent,  aqueous  sugar  solution  were  simi- 
larly determined.  The  proteins  soluble  in  70  per  cent,  alcohol  were  estimated 
by  direct  treatment  of  the  flours,  and  a Kjeldahl  estimation  on  the  filtrate. 
The  proteins  similarly  dissolved  by  20  per  cent,  of  sugar  in  70  per  cent, 
alcohol  (sugar-spirit)  were  also  determined.  The  following  are  the  results 
in  percentages  obtained  on  the  same  two  flours  : — 


Constituents. 

A. 

B. 

Total  Proteins 

11-6 

11-6 

9-9 

9-9 

Proteins  soluble  in  Water 

,,  ,,  Sugar- water 

10 

1-5 

0-5  ; 

i 

2-5 

Gliadin  and  Glutenin 

10-6 

101 

9-4 

7-4 

Soluble  in  Alcohol,  Gliadin 
,,  ,,  “ Sugar-spirit  ” 

6-4 

7-5 

4-6 

5-7 

Insoluble,  Glutenin 

4-2 

2-6 

4-8 

1-7 

It  is  assumed  here  that  water  and  sugar-water  respectively  do  not 
dissolve  the  same  proteins  as  are  dissolved  by  alcohol  and  sugar-spirit ; 
probably  however  there  is  some  overlapping.  As  the  experiments  are  com- 
parative this  does  not  affect  the  point  under  consideration.  It  will  be 
noticed  that  in  eveiy  case  there  is  an  increased  solvent  power  exerted 
when  sugar  is  present.  These  tests  were  confirmed  by  others  on  four 
other  samples  of  flour.  In  all  cases,  sugar-spirit  dissolved  considerably 
more  protein  than  did  plain  alcohol.  Sugar  diminishes  rather  than  increases 
the  water  absorptive  power  of  the  flour.  In  small  quantities  it  is  very 


THE  STRENGTH  OF  FLOUR.  317 

possible  that  its  solvent  action  on  the  gluten  may  effect  sufficient  softening 
to  increase  the  gas-retaining  power  of  the  dough  and  thus  indirectly  increase 
the  strength  of  the  flour. 

455.  The  Shape  of  the  Loaf,  Wood. — ^Following  up  his  previous  paper, 
Wood  made  a subsequent  communication  on  what  he  regards  as  the  second 
factor  of  strength,  viz.  that  which  decides  the  shape  of  the  loaf,  and  this 
was  tentatively  ascribed  to  the  soluble  salts  present  in  the  flour.  A 
further  investigation  was  made  of  this  hypothesis,  and  first  acidity  and 
soluble  salts  were  determined  in  a number  of  wddely  differing  flours.  But 
bakers'  marks  were  found  to  exhibit  no  relationship  to  either  acidity  or 
soluble  ash,  though  there  appeared  to  be  some  relation  between  bakers' 
marks  and  the  ratio  of  soluble  ash  to  total  nitrogen.  Further  investigation 
confirmed  this  relationship,  and  led  to  a study  of  the  effects  produced 
on  wet  gluten  by  its  immersion  in  various  solutions. 

Apparatus  used. — A quantity  of  gluten  was  prepared  from  ordinary 
flour.  A large  number  of  small  beakers  was  each  marked  at  80  c.c.  Nor- 
mal hydrochloric  acid  was  then  run  into  each  in  such  quantity  as  to  pro- 
duce the  desired  strength  when  water  had  been  added  to  the  80  c.c.  mark. 
Pieces  of  V-shaped  glass  rod  were  prepared  which  would  rest  on  the  edge 
of  the  beaker  and  with  the  lower  point  in  the  solution.  A piece  of  gluten 
was  taken  for  each  experiment  about  two  inches  long  and  as  thick  as  a 
pencil  : this  was  hung  by  its  middle  point  on  the  V-shaped  glass  support, 
the  gluten  being  thus  immiersed  in  the  solution.  With  mineral  acids,  no 
antiseptic  was  necessary,  but  in  all  other  cases  the  solutions  were  made 
up  with  water  which  had  been  shaken  with  toluene.  With  distilled  water, 
the  gluten  retained  its  coherence  until  changed  by  bacterial  action,  or  with 
frequent  changes  of  the  w^ater  until  all  acids  and  salts  had  disappeared. 

Effect  of  Acids. — Very  dilute  hydrochloric  acid,  N / 1000  caused  rapid  disin- 
tegration and  loss  of  coherence  in  the  submerged  gluten.  This  change  w^as 
accelerated  by  an  increase  of  the  strength  of  the  acid  up  to  N/20.  Further 
concentration  slow^ed  down  the  rate  of  charge  until  at  A /1 2 the  gluten  became 
permanently  coherent  and  much  harder  and  more  elastic,  and  less  sticky 
than  in  its  original  condition.  [Compare  this  with  the  effects  of  w^eak  and 
somewhat  stronger  acids  on  the  diastatic  capacity  of  flour,  par.  137,  1895.] 
Experim^ents  with  sulphuric,  phosphoric,  and  oxahc  acids,  show^ed  them 
to  behave  similarly  to  hydrochloric  acid,  but  with  different  limits  of  con- 
centration for  permanent  coherence.  Working  upwards  from  a very 


dilute  solution,  the  following  are  such  limits  ; — 

Hydrochloric  Acid  . . . . . . . . . . A/12 

Sulphuric  ,,  . . . . . . . . . . A/25 

Phosphoric  ,,  ..  ..  ..  ..  ..  1*75  N 

Oxalic  . . , , . . . . . . . . . . A/4 


Experiments  with  acetic,  lactic,  citric,  and  tartaric  acids,  show'ed  these 
to  behave  differently.  Dilute  solutions  caused  disintegration,  and  this 
becam.e  more  rapid  with  greater  concentration.  At  no  point  did  coherence 
reappear. 

Mixtures  of  Acids  and  Salts. — An  extensive  series  of  experim^ents  w^as 
next  made  with  gluten  and  mixtures  of  acids  and  salts.  The  proportion 
of  each  was  varied,  and  the  results  noted.  In  the  first  place  hydrochloric 
acid  and  sodium  chloride  (common  salt)  were  employed.  Using  A/50  acid 
(which  was  a disintegrating  strength)  it  was  found  that  salt  was  required 
up  to  a degree  of  concentration  of  N/12  in  order  to  secure  coherence  of  the 
immersed  gluten.  With  either  more  or  less  acid,  less  salt  was  required. 
The  action  generally  of  the  salt  was  a binding  one,  and  in  certain  quantity 
it  overcame  the  disintegrating  effect  of  the  acid.  In  conj  unction  with  acids. 


318 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


three  sodium  salts  were  made  the  subject  of  experiment,  the  chloride, 
sulphate,  and  phosphate.  The  chloride  and  phosphate  were  about  equal 
in  power  of  producing  coherence,  the  sulphate  being  much  more  active 
than  either  of  the  others.  On  making  similar  tests  with  the  sulphates 
of  sodium,  magnesium,  and  aluminium,  their  activity 'increased  in  the  order 
given,  the  ratios  being  roughly  expressed  by  1:2:4. 

As  lactic  acid  disintegrates  gluten  at  all  strengths  it  shows  a different 
behaviour  with  salts.  As  the  concentration  of  the  acid  is  increased,  so 
must  also  that  of  the  salt  in  order  to  preserve  coherence. 

The  amount  of  soluble  salt  required  to  produce  a certain  degree  of  co- 
herence with  such  an  acid  as  hydrochloric  acid  at  first  increases  with  the 
acidity  up  to  a maximum  and  then  falls  off  again.  During  the  period  in 
which  the  acid  is  acting  as  a disintegration  agent,  the  more  that  action 
increases,  the  greater  the  amount  of  the  binding  salt  is  necessary  in  order 
to  counteract  that  effect.  But  as  the  acid  action  diminishes  with  a further 
increase  in  concentration,  less  of  the  binding  salt  becomes  necessary.  The 
connection  between  the  two  is  therefore  not  so  obvious  as  it  otherwise 
might  be.  [In  passing  it  may  be  stated  that  no  mention  is  made  of  experi- 
ments with  neutral  salts  only  in  the  absence  of  acids.] 

On  immersion  of  pieces  of  gluten  for  forty-eight  hours  in  mixtures  of  acid 
and  salt  in  which  the  proportions  are  such  as  just  to  maintain  coherence,  they 
are  found  to  be  far  inferior  in  coherence,  toughness,  and  elasticity  to  samples 
of  fresh  gluten  from  the  same  flours.  On  weighing  such  gluten  both  in 
the  wet  and  dry  state,  the  ratios  were  found  to  be  approximately  5:1. 
With  an  increase  in  the  degree  of  concentration  of  the  salt,  the  gluten  gets 
drier,  and  the  ratio  more  nearly  approaching  that  of  freshly  washed  gluten. 
This  property  seems  to  offer  an  explanation  of  the  well-knovTi  difference 
in  water-absorbing  capacity  found  in  certain  flours,  and  since  the  tough- 
ness of  the  gluten  increases  as  the  water  content  falls,  to  connect  both  water 
absorption  and  toughness  of  gluten  with  acidity  and  content  of  soluble 
salt. 

Conclusions. — Wood  sums  up  his  conclusions  as  follows  : — “ The  experi- 
ments above  described  suggest  that  the  variations  in  coherence,  elasticity, 
and  water  content,  observed  in  gluten  extracted  from  different  flours, 
are  due  rather  to  varying  concentrations  of  acid  and  soluble  salts  in  the 
natural  surroundings  of  the  gluten  than  to  any  intrinsic  difference  in  the 
composition  of  the  glutens  themselves.  These  properties  must  undoubtedly 
have  a direct  bearing  on  the  power  which  some  flours  possess  of  making 
shapely  loaves.  I suggest  therefore  that  the  factor  of  strength  on  which 
the  shape  of  the  loaf  depends  is  the  relation  between  the  concentrations 
of  acid  and  soluble  salts  in  the  flour.'' 

Confirmatory  Tests. — One  possible  method  suggested  is  that  of  determin- 
ing acidity  and  soluble  salt  content  of  a flour,  and  then  modifying  them 
by  the  addition  of  acid,  alkali,  or  salt.  This  would  be  followed  by  baking 
tests  in  order  to  discover  if  the  treatment  had  altered  the  water-absorbing 
capacity  or  the  shape  of  the  loaf.  But  the  author  of  the  paper  foresees 
an  objection,  inasmuch  as  the  small  piece  of  gluten  taken  for  a test  requires 
forty-eight  hours  in  order  to  become  permeated  with  the  solution  in  which  it 
has  been  immersed.  Obviously,  dough  cannot  be  allowed  to  stand  forty-eight 
hours  before  baking.  An  alternative  method  suggested  is  that  determining 
the  acidity  and  soluble  salt  content  of  a number  of  flours  and  comparing 
them  with  the  baking  properties.  But  these  figures  will  require  to  be 
considered  in  relation  to  the  nature  of  the  acids  and  salts,  and  their  degree 
of  concentration  The  degree  of  concentration  of  the  acid  and  salts  must 
be  changing  during  the  whole  period  of  formation  of  the  grain,  and  the 
question  arises  as  to  Avhat  stage  of  growth  it  is  at  which  they  imprint  upon 


THE  STRENGTH  OF  FLOUR. 


319 


the  gluten  those  physical  properties  which  decide  the  character  of  the  flour. 
Wood  regards  this  time  as  being  that  when  the  endosperm  is  being  formed 
and  is  in  a comparatively  milky  stage.  The  author  of  the  paper  realises 
th?  t his  “ results  are  at  present  only  in  what  may  be  called  a suggestive 
state.’'  {Wood,  Jour.  Agric.  Science,  1907,  2,  267.) 

456.  Solubility  of  Gluten  on  Ionisation  Hypothesis,  Wood  and  Hardy. — 

These  chemists  have  contributed  a paper  to  the  Royal  Society  in  which 
they  deal  with  the  solution  of  gluten  in  weak  acids  on  the  hypothesis  of 
ionisation.  They  point  out  that  the  colloidal  solutions  of  characteristically 
insoluble  bodies  are  distinguished  by  the  fact  that  round  each  particle 
of  the  solute  (substance  dissolved)  there  is  an  electric  double  layer,  and  on 
the  potential  difference  between  wiiich  the  stability  of  the  solution  de- 
pends. “ On  this  view  the  formation  of  the  hydrosol  (aqueous  solution) 
of  gluten  is  due  to  the  development  of  electric  charges  round  the  particles 
of  the  protein  owing  to  chemical  interaction  between  the  protein,  the  acid 
or  alkali,  and  the  water  : and  the  tenacity,  ductility,  and  w^ater  content 
of  a solid  mass  of  moist  gluten  depends  upon  the  total  or  partial  disap- 
pearance of  these  electric  double  layers,  and  the  reappearance  of  wLat 
is  otherwise  obscured  by  them,  namely,  the  adhesion  or  ‘ idio  attraction  ’ 
as  Graham  called  it,  of  the  colloid  particles  for  each  other,  wiiich  makes 
them  cohere  when  they  come  together.”  This  form  of  solution  being 
due  to  ionisation,  when  the  concentration  of  acid  rises  above  a certain  value, 
there  is  a decrease  and  finally  a disappearance  of  the  potential  difference, 
due  to  the  suppression  of  the  feeble  ionisation  by  the  excess  of  acid.  (Wood 
and  Hardy,  Proc.  Roy.  Soc.  1909,  B 81,  38.) 

This  is  interesting  as  a step  toward  bringing  the  phenomena  of  the 
solubility  of  gluten  into  harmony  with  the  ionisation  theory. 

457.  An  Analysis  of  the  Factors  contributing  to  Strength  in  Wheaten 
Flour,  Hardy. — Hardy  further  elaborated  and  explained  his  view  s on  the 
relation  of  strength  to  electric  potential  in  a paper  read  by  him  at  the  meet- 
ing of  the  British  Association  for  the  Advancement  of  Science,  1909.  He 
compares  dough  to  rubber  loaded  with  solid  particles,  the  gluten  being  the 
analogue  of  the  rubber,  and  the  starch  contributing  the  solid  particles. 
He  goes  on  to  say  : — There  has,  so  far  as  I know,  been  no  exact  work  upon 
the  influence  of  the  size  and  number  of  the  starch  grains  upon  the  mechanical 
properties  of  dough  ; in  the  absence  of  such  information  it  is  idle  to  pursue 
the  point  further.  This  may,  how^ever,  be  said  : judging  by  what  is  knowm 
of  the  influence  of  embedded  small  particles  in  other  cases,  the  power  of 
the  dough  to  retain  its  shape  may  be  due  in  some  cases  primarily  to  the 
nature  and  number  of  the  starch  grains.  But  the  essential  active  agent  is 
the  protein-complex  gluten. 

Now  gluten,  even  though  it  be  prepared  from  the  best  Fife  flour,  has  of 
itself  neither  ductility  nor  tenacity.  In  presence  of  ordinary  distilled  water 
it  partly  dissolves,  the  residue — the  larger  portion — forming  a semi-fluid 
sediment  destitute  of  tenacity.  Why  ? Because  tenacity  and  ductility 
are  properties  impressed  on  gluten  by  something  else — namely,  by  salts, 
by  electrolytes,  that  is,  which  may  be  organic  and  may  therefore  be  unrepre- 
sented in  an  ash  analysis. 

This  being  the  case,  it  is  obvious  that  any  attempt  to  correlate  strength 
with  the  physical  properties  of  gluten  washed  out  in  the  ordinary  way  must 
end  in  failure,  since  the  properties  of  washed  gluten  depend  upon  the  elec- 
trolytes which  happen  to  be  left  in  after  the  w-ashing  is  concluded. 

Electrolytes — that  is  to  say  salts,  acids  and  alkahs — intervene  in  tw  o 
absolutely  distinct  ways.  They  control  the  physical  properties  of  the  gluten 
in  the  dough,  and  they  must  also  profoundly  modify  the  temperature  rela- 


320 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


tions  and  the  rapidity  of  the  change  undergone  by  the  gluten  and  other  con- 
stituents of  the  dough  in  the  process  of  baking — a change  which,  so  far  as 
the  proteins  are  concerned  is,  broadly  speaking,  a lowering  of  solubility. 
We  know  something  of  the  way  in  which  they  act  on  gluten  in  the  dough, 
but  of  the  more  complicated  action  during  temperature  changes  we  know 
nothing  ; it  is  possible  that  the  same  electrolyte  may  increase  the  mechani- 
cal stability  of  the  loaf  in  the  dough  and  yet  diminish  it  in  the  oven. 

The  writer  next  summarises  the  results  of  Wood’s  experiments  before 
described,  in  which  it  is  shown  that  certain  very  dilute  acids  disperse  gluten 
in  fine  particles,  which  are  so  changed  that  they  actually  repel  one  another, 
such  repulsion  being  overcome  and  cohesion  restored  by  the  neutralisation 
of  the  acid  or  the  addition  of  any  salt  such  as  common  table  salt.  The 
cohesion  of  gluten  is  due  to  the  salts  naturally  present ; and  their  removal, 
as  by  washing  with  distilled  water,  causes  the  breaking  down  of  the  gluten. 
When  gluten  is  thoroughly  extracted  with  distilled  water  it  loses  cohesion 
and  disperses  as  a cloud,  not  owing  to  the  action  of  the  water,  but  because 
of  the  faint  acidity  due  to  the  carbonic  acid  dissolved  from  the  air.  In  the 
absence  of  salts,  this  is  sufficiently  strong  to  destroy  cohesion.  In  cases 
v'here  the  quantity  of  salt  is  insufficient  to  counteract  that  of  the  acid,  the 
gluten  is  in  a state  of  colloidal  solution,  containing  exceedingly  fine  particles 
of  gluten.  With  an  increase  of  salt  the  particles  become  continually  coarser, 
until  finally  they  run  together  into  a coherent  mass  of  gluten.  As  the  salts 
present  still  further  increase,  there  is  still  further  separation  of  water,  and 
as  the  water-holding  power  of  the  protein  diminishes,  so  also  does  its  duc- 
tility, while  at  the  same  time  there  is  an  increase  in  the  tenacity. 

Electrolytes,  therefore,  do  more  than  confer  on  gluten  its  mechanical 
properties  ; they  determine  also  its  power  of  holding  water.  They  also 
determine  the  water-holding  power  of  any  other  colloid  matter  present  in 
the  dough. 

Acids  and  alkalis  destroy  cohesion  and  disperse  the  particles  of  gluten 
just  as  they  produce  and  stabilise  non-settling  suspensions  in  many  types 
of  colloidal  solution — namely,  by  the  development  of  a difference  of  electric 
potential  between  the  particles  and  the  water.  The  curve  which  connects 
the  potential  difference  with  the  concentration  of  acid  has  the  same  form  as 
that  which  represents  the  region  of  gluten  non-cohesion. 

The  foregoing  analysis  of  the  factors  which  control  the  physical  pro- 
perties of  gluten  in  moist  dough  lead  us  to  a brief  analysis  of  the  source  of 
“ strength  ” in  flour.  It  must  be  borne  in  mind  that  loaf -making  includes 
two  distinct  operations,  the  making  and  incubation  of  the  dough  and  the 
fixation  of  the  incubated  dough  by  heat.  Every  factor  which  contributes 
to  the  rising  of  the  dough — that  is,  to  the  size  of  the  loaf — and  to  the  power 
of  the  dough  to  preserve  its  shape  (saving  only  the  vital  activities  of  the 
yeast  plants)  intervenes  also  in  the  fixation  of  the  dough,  where  it  may 
undo  what  it  has  already  done.  Successful  incubation  depends  upon  : (1) 
The  suitability  of  the  dough  for  the  active  growth  and  production  of  car- 
bonic acid  by  the  yeast  plant,  which  again  depends  upon  the  concentration 
of  sugar,  the  intrinsic  diastatic  power  of  the  dough  and  the  concentration 
and  nature  of  the  electrolytes.  (2)  The  physical  character  of  the  dough, 
wliich  depends  upon  the  size,  shape,  and  number  of  starch  grains,  the  nature 
and  concentration  of  the  electrolytes,  since  these  determine  the  physical 
properties  of  colloids  present,  notably  the  gluten.  The  electrolytes  will 
also  direct  tiiose  molecular  rearrangements  which  occur  during  the  baking 
process  and  which  give  fixity  and  stability  to  the  entire  structure.  (Supple- 
ment, June,  4,  1910,  p.  52,  Jour.  Board  of  Agric.) 

Snyder  had  previously  dealt  with  the  effect  of  variations  in  the  quan- 
tity of  starch  on  the  character  of  dough,  and  concluded  that  they  were 


THE  STRENGTH  OF  FLOUR. 


321 


without  any  marked  effect  (paragraph  444).  One  of  the  authors  had  pre- 
viously showTi  that  with  flours  having  different  quality  glutens,  such  glutens 
maintained  their  individual  character  through  a long  range  of  variations 
produced  by  the  addition  of  starch  (paragraph  438).  Hardy  advances 
the  paradox  that  gluten,  even  of  the  strongest  flour,  “ has  of  itself  neither 
ductility  nor  tenacity.'’  The  correctness  of  this  dictum  depends  on  the 
deflnition  of  the  word  “ gluten."  In  the  primary  sense  in  which  that  word 
is  almost  universally  employed,  gluten  is  the  name  of  that  elastic,  ductile, 
and  tenacious  mass,  whatever  may  he  its  composition,  which  is  obtained  by 
washing  dough  in  the  recognised  manner.  Gluten  has  hitherto  been  sup- 
posed to  consist  essentially  of  protein  matter,  but  Wood’s  researches  go 
to  show  that  certain  salts  exercise  a profound  influence  on  its  character. 
The  presence  of  these  may  in  fact  be  regarded  as  a necessity,  and  if  they 
be  removed  the  remaining  body  or  bodies  is  no  longer  gluten  in  the  generally 
accepted  sense  of  the  word.  Putting  it  another  way,  the  proteins  of  gluten, 
in  the  absence  of  electrolytes,  are  collectively  neither  ductile  nor  tenacious. 
But  from  this  it  does  not  folloAV  that  no  relation  exists  between  the  strength 
of  a flour  and  the  physical  properties  of  its  washed-out  gluten.  It  is  gener- 
ally agreed  that  the  physical  strength  of  dough,  i.e.,  its  ductility  and  ten- 
acity, depends  on  the  quantity  and  quality  of  the  gluten  it  contains,  using 
that  word  in  its  evident  sense  as  including  proteins,  electrolytes,  and  all  that 
goes  to  give  that  body  its  essential  characters.  As  a matter  of  fact,  the 
general  rule  is  that  a properly  washed-out  gluten  correctly  reflects  by  its 
quantity  or  quality,  or  both,  the  strength  of  the  flour  from  which  it  was 
obtained.  To  this  the  exceptions  are  remarkably  few,  and  interesting 
evidence  of  the  value  of  this  test  was  given  by  Saunders  in  the  course  of  a 
paper  read  by  him  at  the  same  meeting,  and  quoted  at  the  close  of  this 
chapter.  When  gluten  washing  is  done  with  suitable  water,  sufficient 
electrolytes  remain  in  the  gluten  to  conserve  its  characteristic  properties, 
and  enable  a judgment  to  be  based  thereon. 

The  writer’s  speculations  as  to  the  effect  of  electrolytes  through  the 
v'hole  process  of  baking,  as  well  as  of  fermentation,  are  of  interest,  and  may 
very  probably  indicate  the  direction  in  which  the  future  solution  of  many 
problems  may  be  found.  The  relationship  of  cohesion  of  gluten  to  electric 
potential  is  clearly  indicated,  but  the  question  remains  whether  any  part  of 
the  operations  of  baking  falls  vlthin,  or  even  approaches,  the  region  of  non- 
cohesion of  gluten.  Taking  the  figures  given  in  the  writer’s  paper,  about 
22  grains  of  common  salt  per  1,000  litres  is  sufficient  to  neutralise  the  maxi- 
mum disintegrating  effect  of  sulphuric  acid.  The  word  grain  may  possibly 
be  a misprint  for  gram,  and  if  so  the  figure  is  22  grams  per  1,000  litres.  As- 
suming this  latter  to  be  correct,  then  the  degree  of  concentration  is  22  grams 
per  1,000  litres  = 22  grams  per  1,000,000  grams  of  water.  In  bread-making 
salt  is  always  used,  and  to  an  extent  of  about  3 lbs.  to  the  sack  of  280  lbs.  of 
flour.  To  the  water,  salt  is  taken  in  the  approximate  proportion  of  2 lbs.  of 
salt  per  100  lbs.  of  water,  which  equaU2,000  grams  of  salt  to  1,000,000  grams 
of  water,  or  about  ninety  times  the  concentration  for  the  critical  point  in 
Hardy’s  curve.  The  question  of  the  influence  of  sugar  upon  strength  has  been 
already  discussed,  and  vitli  it  much  of  the  importance  or  otherwise  of  the 
diastase  of  dough  is  closely  connected.  Snyder’s  work  already  referred  to 
goes  to  minimise  the  effect  of  starch  grains. 

458.  Size  of  Starch  Grains,  Armstrong. — The  size  of  wheat  starch  grains 
was  also  referred  to  by  Armstrong  in  a paper  read  at  the  same  meeting. 
He  states  that  microscopic  examination  shows  flour  to  consist  of  starch 
granules  of  three  different  sizes.  The  smallest  granules  which  preponderate 
in  amount  are  from  3 to  5 /x  in  diameter,  the  largest  granules  are  about  30 
to  35  /X,  and  there  are  also  granules  of  intermediate  size.  The  microscopic 

Y 


322 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


examination  of  a large  number  of  flours  of  different  origin  has  shown  that 
the  large  granules  vary  in  number  from  6 to  1 J per  cent,  of  the  total  number 
of  granules.  In  other  words,  in  one  flour  as  much  as  30  to  40  per  cent,  of 
the  total  weight  of  starch  is  in  the  form  of  large  grains,  whilst  in  another 
only  7 to  10  per  cent,  is  in  this  condition. 

Before  a starch  grain  can  be  converted  into  sugar  the  cellular  envelope 
has  first  to  be  destroyed.  Obviously,  when  the  envelope  of  the  large  granule 
is  destroyed  a much  larger  proportion  of  starch  is  rendered  available  than 
when  the  contents  of  a small  granule  are  liberated. 

Whymper  has  recently  made  a microscopic  study  of  the  changes  occur- 
ring during  the  germination  of  wheat.  He  finds  that  the  larger  and  more 
mature  granules  are  the  most  readily  attacked  by  the  enzymes  of  the  planta- 
let.  Though  there  is  no  general  relation  between  the  size  of  starch  granules 
of  different  origin  and  the  ease  with  which  they  are  attacked  by  diastase 
and  other  agents,  it  appears  that  the  larger  granules  of  any  particular  starch 
are  affected  sooner  than  the  smaller  granules.  {Supplement,  June  4,  1910, 
p.  49,  Jour.  Board  of  Agric.) 

Armstrong’s  examination  of  starch  is  evidently  the  result  of  his  con- 
clusions that  flour  does  not  contain  sufficient  sugar  for  bread-fermentation, 
and  that  the  requisite  sugar  is  always  provided  by  the  hydrolysis  of  starch. 

With  the  object  of  further  investigating  the  effect  of  different  sizes  of 
starch  granules,  the  authors  made  the  following  experiments.  A strong 
American  flour  was  taken,  being  No.  6 in  the  Table  of  Flours  and  Wheats, 
described  in  Chapter  XXVIII,.  To  80  parts  of  this  flour  there  were 
added  and  thoroughly  mixed  20  parts  of  potato,  wheat,  and  maize 
starches  respectively.  The  potato  starch  granules  are  considerably  larger 
than  those  of  wheat,  while  those  of  maize  starch  are  very  much  smaller. 
[Compare  with  dimensions  given  in  Plate  I and  accompanying  description 
in  letterpress.]  In  these  three  mixed  flours  the  average  size  of  the  starch 
granules  was  therefore  increased  in  the  first,  unaltered  in  the  second,  and 
diminished  in  the  third.  The  original  flour  yielded  15-02  per  cent,  of  dry 
gluten,  which  gives  the  mixed  flours  an  amount  of  12-01  per  cent,  m each 
case.  Viscometer  determinations  of  water  absorption  gave  the  folloving 
results  in  quarts  per  sack  ; — 


1 

Flour  only.  ; 

Flour  and  Potato  Starch. 

Flour  and  Wheat  Starch. 

Flour  and  Maize  Starch. 

Quarts. 

Seconds,  i 

Quarts. 

1 

Seconds,  j 

Quarts. 

Seconds. 

Quarts. 

Seconds. 

65 

315 

65 

90 



— 



— 

— 

66 

81 

66 

102 





I 66*5 

60 

— 

— 

— 







— 

67-0 

60 

— 

— 

68 

227 

1 68 

42 

68 

i 48 

68 

54 

70 

52 

70 

27 

70 

28 

70 

37 

72 

43 

1 ~ 

j 

The  figures  in  heavier  type  are  those  which  practically  agree  with  the 
sixty  seconds  standard.  The  whole  of  the  starched  flours  have  fallen  off 
in  water-absorbing  power.  Throughout  the  series  of  tests,  this  falling  off 
has  been  greatest  with  the  potato  starch  and  least  with  that  of  maize.  The 
difference  may  probably  be  accounted  for  by  the  greater  surface  offered  by 
the  smaller  starches  in  proportion  to  their  weight. 

Baking  tests  were  next  made  with  the  flours  with  the  special  object  of 


THE  STRENGTH  OF  FLOUR. 


323 


observing  their  strength  behaviour  both  in  the  dough  and  the  loaf.  A stiff 
dough  was  made  from  each  for  crusty  Coburg  loaves.  The  water  taken 
was  in  the  same  proportions  as  in  the  viscometer  tests.  Those  from  the 
three  mixed  flours  fermented  much  more  rapidly  than  did  the  unmixed 
flour,  which  latter  made  a bold  sweet  loaf,  while  the  former  on  falling  in  the 
dough  was  unable  to  rise  again  either  during  fermentation  or  in  the  oven. 
The  starch-mixed  loaves  were  all  distinctly  over-worked  and  sour  to  the 
nose.  A second  test  was  made  in  which  the  three  mixed  flours  were  fer- 
mented for  a shorter  time,  as  nearly  as  possible  three-quarters  of  that 
required  by  the  unmixed  flour  only.  In  this  case  much  better  results  were 
obtained,  but  all  the  doughs  fell  off  in  the  latter  stages  of  fermentation, 
and  had  comparatively  little  “ spring  ""  in  the  oven.  The  differences  in 
behaviour  were  very  slight  ; but  if  anything  the  potato  starch  loaf  was 
least  tough  and  “ springy  ""  (elastic)  in  the  dough,  and  rose  least  in  the  oven. 
The  wheat  starch  loaf  came  next,  and  the  maize  starch  gave  the  best  results 
of  the  three. 

459.  Water-soluble  Phosphates  in  Wheat,  Wood. — Professor  Wood  has 
kindly  forwarded  to  the  authors  in  1910  an  advance  note  of  experiments 
recently  performed  by  him,  of  which  the  following  is  a summary : — Wood 
made  a number  of  analyses  of  the  water  extract  of  different  flours.  The 
method  used  was  to  shake  up  200  grams  of  flour  with  2,000  c.c.  of  water 
containing  a few  drops  of  toluene  to  delay  ferm^entation.  The  shaking 
was  continued  for  one  hour,  and  the  mixture  then  filtered.  Ahquot  portions 
of  the  clear  solution  were  then  evaporated  to  dryness,  and  their  content 
of  phosphoric  acid,  lime,  magnesia,  chloride,  and  sulphate  determined.  He 
finds  that  in  all  the  flours  made  from  Fife  wheat,  the  water  soluble  phos- 
phate is  high — over  OT  percent,  of  the  flour,  and  the  chlorides  and  sulphates 
very  low.  They  also  contain  more  magnesia  than  lime.  Wood  has  ex- 
amined about  half  a dozen  samples  of  Fife,  som.e  grown  in  Canada  and 
some  grown  in  various  parts  of  England,  and  they  all  agree  in  these  respects. 
Weak  wheats  of  the  Square  Head’s  Master  type,  and  in  fact  all  the  wheats 
he  has  examined,  except  the  Fifes,  and  one  which  cam^e  from  Japan,  contain 
from  0*08  per  cent,  to  as  low  as  0’04  per  cent,  of  water-soluble  phosphoric 
acid,  and  correspondingly  higher  amounts  of  sulphate  and  chloride,  and 
as  a general  rule  m.ore  lime  than  magnesia.  Wood  has  little  doubt  that 
the  peculiar  properties  of  the  gluten  of  the  Fife  wheats  is  due  to  their  high 
content  of  water-soluble  phosphate,  and  believes  that  the  determination 
of  the  water-soluble  phosphate  gives  a gi'eat  deal  of  information  as  to  the 
character  of  the  gluten  content  in  a flour.  {Personal  Communication,  May, 
1910.) 

As  Wood’s  papers  form  a connected  series,  it  was  thought  preferable  not 
to  separate  them.  Reverting  now  to  somewhat  earlier  researches,  the 
record  is  resumed  by  the  following  abstracts  : — 

460.  Can  Glutenin  absorb  Gliadin  ? Matthev/son. — In  1908  there  were 
published  the  reults  of  some  experiments  made  by  Matthewson  in  order 
to  investigate  the  point  as  to  whether  or  not  glutenin  possesses  any  absorj)- 
tive  power  for  gliadin  in  an  alcoholic  solution.  A sample  of  flour  was  freed 
from  gliadin  by  cold  extraction  with  alcohol,  washing  with  concentrated 
alcohol  and  drying.  This  flour  was  added  to  a solution  of  pure  gliadin  in 
alcohol,  shaken  repeatedly  for  three  hours,  allowed  to  stand  over  night,  and 
filtered.  The  filtrate  had  suffered  no  change  in  gliadin  content  by  its  con- 
tact vuth  the  gliadin-free  flour.  In  a second  experiment  dry  glutenin  was 
used,  having  been  prepared  in  the  following  manner  : — Thoroughly  washed 
gluten  was  cut  into  small  pieces  and  extracted  with  successive  portions  of 


324 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


dilute  alcohol,  washed  with  strong  alcohol,  dried  at  room  temperature* 
ground  to  a fine  powder,  extracted  with  ether  and  with  absolute  alcohoh 
again  extracted  repeatedly  with  dilute  alcohol,  rinsed  with  strong  alcohol, 
and  dried  at  room  temperature.  The  glutenin  w^as  added  to  the  ghadin 
solution,  in  which  it  sw'elled  up.  On  filtering,  the  ghadin  solution  w^as  found 
to  have  become  more  concentrated,  showing  that  instead  of  the  glutenin 
having  removed  gliadin  from  the  solution,  it  had  evidently  absorbed  either 
w'ater  or  dilute  alcohol.  The  obvious  conclusion  is  that  glutenin  ha«  no 
tendency  to  remove  gliadin  from  its  alcoholic  solution.  {Jour.  Amer.Chem. 
Soc.,  1908,  74.) 

The  above  is  a somewhat  interesting  investigation,  and  should  be  com- 
pared with  the  experiment  of  Osborne  and  Voorhees  described  on  page 
115,  in  which  additional  gluten  is  obtained  by  adding  ghadin  to  flour,  and 
then  washing  out  the  gluten  in  the  usual  manner.  Compare  also  with  the 
experiments  on  adsorption  by  chalk  and  kieselguhr,  given  in  the  descrip- 
tion of  ghadin  determinations  in  Chapter  XXVIII. 

461.  Amylolytic  and  Proteolytic  Ferments  of  Wheat,  Ford  and  Guthrie. — 

This  investigation  was  undertaken  with  the  view  of  examining  the  action 
of  diastase  and  like  bodies  on  the  starchy  and  protein  m-atters  of  wiieat. 
In  measuring  the  amylolytic  powder  of  the  ferments  present  in  wEeaten 
flour,  the  wTiters  employed  soluble  starch  of  R.  1*0  as  the  hydrolyte,  and 
expressed  their  results  in  terms  of  grams  of  maltose  produced  by  the  filtered 
extract  of  I gram  of  the  substance  acting  on  excess  of  soluble  starch  for  one 
hour  at  40°  C. 

Duration  of  Extraction. — In  the  following  experiments  20  gram-S  of 
flour  were  added  to  500  c.c.  of  w^ater  at  18°  C.,and  shaken  up  by  a shaking 
machine  for  the  times  given  in  the  table,  after  wiiich  they  were  filtered  and 
tested  : — 


1 ^ Grams  of  Maltose  per  1 Gram  of  Flou’'. 

Time  of  Extraction. 

Minutes. 

' ! Xo.  1. 

i 

No.  2. 

1 

1 

10  1 8*88 

12*88 

30  ! 8*03 

13*58 

60  , 5*38 

13*65 

90  3*48 

11*41 

120  3*00 

9*31 

It  is  obvious  from  these  results  that  destruction  of  the  enzyme  occurs 
with  varying  rapidity  after  the  addition  of  the  w ater  to  the  flour.  Sample 
No.  1 was  acid  in  reaction,  and  sample  No.  2 very  faintly  alkaline  to  rosolic 
acid,  and  as  it  seemed  probable  that  the  acidity  w'as  the  cause  of  the  loss 
of  ferment  activity,  an  attempt  w^as  made  to  adjust  the  “ neutrality  ” of 
the  aqueous  extraction  by  the  addition  of  2 grams  of  potassium  di-hydrogen 
pliosphate  plus  0*2  gram  of  di-sodium  hydrogen  phosphate  per  500  c.c.  of 
water.  When  flour  No.  1 w'as  thus  extracted  for  thirty  minutes,  it  gave 
14*28  grams  of  maltose  as  against  8*03  in  the  preceding  table.  The  addition 
of  certain  neutral  salts  to  the  w^ater  was  also  found  to  have  a protective 
effect.  Taking  potassium  chloride  as  an  example  of  these,  the  addition  of 
40  grams  per  litre  to  the  extraction  w^ater,  and  then  digestion  of  the  flour 
for  eighteen  hours  at  30°  C.,  resulted  in  a maltose  yield  of  18 '90  grams  as 
against  4*06  grams  with  the  flour  above.  Toluene  w^as  used  as  an  antiseptic 
in  these  experiments. 


THE  STRENGTH  OF  FLOUR. 


325 


Protective  action  of  Proteolysts. — It  is  found  that  flours  contain  large 
amounts  of  amylase  [diastase]  which  may  be  extracted  in  an  active  condition 
by  the  use  of  a suitable  proteolyst.  For  this  purpose  active  papain  was 
found  the  most  suitable,  and  vdth  the  flour  used  in  the  experiment  vdth 
potassium  chloride  (Hungarian)  a figure  of  27*4  grams  of  maltose  was  ob- 
tained from  the  1 gram  of  the  flour,  while  vuth  a high  grade  Canadian  flour 
as  much  as  48  grams  of  maltose  were  produced.  The  amylase  thus  obtained 
is  for  convenience  called  “ total  amylase,''  and  is  determmed  in  the  following 
manner  : 2 grams  of  the  flour  are  digested  with  50  c.c.  oi  a 1 per  cent,  solu- 
tion of  active  papain  for  eighteen  hours  at  30°  C.,  the  solution  is  then  fil- 
tered, and  J c.c.  of  this  is  added  to  70  c.c.  of  starch  solution  (containing  2 
grams  of  starch)  at  40°  C.,  after  thirty  minutes  the  action  is  stopped  by  the 
addition  of  5 c.c.  of  soda  solution  (10  grams  per  litre).  These  conditions 
give  concordant  results,  but  it  is  preferable  to  dilute  25  c.c.  of  the  filtered 
solution  to  100  c.c.,  and  then  to  use  1 c.c.  of  this  and  allow  the  action  to 
proceed  for  one  hour.  The  same  values  are  obtained  by  either  manner  of 
working,  but  departure  from  the  general  conditions  is  not  admissible.  As 
amylolytic  action  requires  for  its  full  development  the  presence  of  neutral 
salts,  it  is  advisable  to  make  an  addition  of  same  as  those  naturally  present 
in  wheat  flour  vary  considerably.  It  is,  therefore,  recommended  to  add 
to  the  papain  0*5  grams,  and  to  the  soluble  starch  0*25  grams  respectively 
per  100  c.c. 

“ Autodigestion  " of  Flours. — An  experiment  was  made  vflth  the  two 
flours  previously  used.  Nos.  1 and  2,  in  which  they  were  digested  with  water 
alone  for  a stated  time  at  30°  C.  As  before,  20  grams  of  flour  were  taken  to 
500  c.c.  of  water : — 


Time. 

Grams  of  Maltose  per  1 Gram,  of  Flour. 

No.  1. 

No.  2. 

After  1 hour 

2*87 

11*83 

,,  3 hours 

2*87 

11*90 

„ 4 „ 

2*80 

11*69 

„ 5 ,, 

2*66 

11*34 

„ 26  „ 

2*52 

12*74 

It  will  be  noticed  that  sample  No.  1 falls  in  value,  whereas  No.  2 shows 
an  increase  at  the  end  of  five  hours.  The  writers  regarded  this  as  an  indi- 
cation that  the  second  flour  contained  a proteolytic  enzyme,  a surmise  which 
subsequent  investigation  proved  to  be  correct.  It  was  thought  that  this 
method  might  prove  of  service  as  a differential  test,  but  as  Avhatever  results 
are  obtained  are  the  product  of  a number  of  factors,  the  authors  discarded 
it  as  not  applicable  for  general  employment.  [It  is  interesting  to  note  here 
that  digestion  for  one  hour  at  30°  reduced  the  amylolytic  power  of  No.  1 
flour  to  a greater  extent  than  two  hours  at  18°  C.  (2*87  and  3°00  respectively). 
On  the  other  hand.  No.  2 flour  has  a greater  capacity  of  resistance  to  heat, 
since  one  hour  at  30°  gives  a maltose  result  of  11*83  as  against  9*31  for  two 
hours  at  18°  C.]. 

Carbon  Dioxide  yield  of  Flour. — Humphries  regards  the  capacity  of  flour 
for  carbon  dioxide  gas  formation  as  one  important  factor  in  its  strength 
{Brit.  Assoc.  Rep.,  1907).  The  writers  point  out  the  greater  part  of  the 
carbon  dioxide  liberated  in  panary  fermentation  must  be  derived  from  the 
starch  of  the  flour  by  the  intervention  of  diastatic  action,  and  therefore  it 


326 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


seemed  likely  that  flours  wdth  the  greatest  amount  of  amylase  would, 
other  things  being  equal,  stand  highest  in  baking  value.  A slight  calculation 
shows  that  the  pre-existent  sugar  in  wheaten  flour  can  only  account  for 
a small  proportion  of  the  carbon  dioxide  formed.  Taking  as  an  example, 
a N.  Manitoba  flour,  which  when  fermented  in  the  usual  way  with  yeast 
yielded  some  350  c.c.  of  gas  per  20  grams  : this  corresponds  roughly  with 
the  fermentation  of  1*3  gram  of  sugar  or  6*5  per  cent,  on  the  flour.  In  this 
flour  the  amylase  was  destroyed  by  first  boiling  the  flour  with  95  per  cent, 
by  volume  alcohol  for  one  hour,  filtering,  and  air  drying.  (In  determining 
the  strength  of  the  alcohol,  allowance  must  be  made  for  the  water  present 
in  the  flour.  Analyst,  1904,  277).  A subsequent  determination  of  sugars 
gave  0*82  per  cent,  of  sucrose  and  0*1  per  cent,  of  a reducing  sugar.  Mani- 
festly then,  amylolytic  action  plays  a prominent  part  in  providing  sugar 
for  the  fermentation.  Total  amylase  was  determined  in  a number  of  flours 
which  had  been  previously  subjected  to  baking  tests  by  Humphries,  by 
whom  “ bakers’  strength  marks  ” had  been  awarded  (maximum  100). 
The  following  table  shows  the  comparative  results  : — 


Sample 

Flour. 

! 

Strength, 

Bakers’  Marks. 

Value, 

Total  Amylase. 

Arrangement  by 

Baking. 

Amylase. 

A 

68 

26-8  1 

c 

F 

B 

70 

29*2  I 

J 

C 

C 

96 

43-2  1 

K 

J 

D 

40 

34-3  1 

F 

E 

E 

76  to  86 

35-8 

i H 

H 

F 

88 

46*8 

I 

I 

G 

68 

25-4 

E 

K 

H 

85 

32-3 

: B 

B 

I 

85 

31-7 

i G 

A 

J 

92 

38-8 

A 

G 

K 

90 

29*6 

D 

D 

L 

35 

221 

L 

L 

1 

Flours  D and  L were  found  to  contain  an  active  proteolytic  enzyme, 
which  enzyme  was  found  to  have  an  extremely  detrimental  influence  on 
the  tenacity  of  the  gluten,  and  hence  on  the  property  of  gas-retention.  The 
results  of  the  examination  of  this  series  of  samples  show,  not  greatly  to 
the  surprise  of  the  writers  of  the  paper,  that  potential  gas-producing  power, 
as  measured  by  the  total  amylase  of  the  flours,  quahfied  by  the  presence  or 
absence  of  an  active  proteolyst,is  not  sufficient  to  assess  their  baking  value. 
It,  however,  indicates  that  in  developing  a method  of  valuation  the  total 
amylase  is  one  important  factor,  also  that  the  presence  of  a proteolytic 
ferment  is  another,  and  possibly  more  valuable,  consideration.  In  con- 
nection \vith  sample  F the  writers  made  a slightly  extended  examination. 
The  baking  test  showed  that  this  flour  “ gives  an  extraordinary  amount 
of  gas,  but  the  dough  does  not  hold  it.”  This  sample  did  not  contain  any 
active  proteolyst,  but  resembled  sample  D in  respect  of  its  soluble  nitro- 
genous constituents.  Its  salts  and  soluble  matters  were  also  high,  and  it  is 
therefore  probable  that  in  the  original  grain  the  metabolism  of  the  endo- 
sperm had  not  attained  such  full  maturity  as  that  from  which  sample  C 
was  milled. 

Detection  of  active  Proteolyst,  Protease. — This  enzyme  may  readily  be 
detected  by  a modification  of  the  usual  gelatin  test.  For  this  purpose,  5 


THE  STRENGTH  OF  FLOUR. 


327 


grams  of  the  flour  are  added  to  50  c.c.  of  1*5  per  cent,  gelatin  (pure)  solution 
saturated  with  nitrobenzene,  and  the  mixture  digested  at  35°  C.  for  at  least 
forty-eight  hours.  By  this  test  samples  such  as  “ D and  “ L show 
obvious  hquefaction.  As  a control,  a check  test  should  be  made  with  a 
flour  known  to  be  free  from  a proteolyst.  In  order  further  to  demonstrate 
the  detrimental  action  of  this  active  proteolyst,  the  authors  supplied  Hum- 
phries with  a preparation  of  protease  equal  in  activity  to  about  five  times 
that  present  in  “ D.'"  On  making  a baking  test  with  this  preparation 
against  a control,  within  a quarter  of  an  hour  of  making  the  dough,  it  was 
seen  that  something  very  abnormal  w^as  taking  place.  The  final  loaf  was 
quite  useless  ; it  had  practically  failed  to  “ rise  ” at  all,  and  the  crumb 
Avas  devoid  of  tenacity.  Humphries  proved  to  his  satisfaction  that  it  was 
gas  retention  and  not  gas  making  w hich  this  proteolytic  enzyme  had  affected. 
The  above  experiments  suggest  a reason  why  certain  preparations  of  malt 
extract  prove  unsuitable  for  use  as  baking  adjuncts,  and  also  provide  one 
explanation  for  the  cause  of  wdiat  is  known  as  “ rotten ""  gluten.  The 
WTiters  suggest  that  the  problem  of  how  far  the  presence  of  a proteolyst 
in  wheaten  flours  is  due  to  racial,  climatic,  or  soil  influences  is  a fit  subject 
for  future  investigation.  [Jour.  Soc.  Chem.  Ind.,  1908,  389.) 

That  there  are  both  amylolytic  and  proteolytic  enzymes  in  flour  was 
w ell  recognised  at  the  time  of  WTiting  this  paper,  the  principal  importance 
of  w hich  hes  in  the  data  obtained  under  certain  conditions  of  exact  measure- 
ment. Dealing  first  wdth  the  starch  converting  body,  it  is  shown  that  the 
activity  of  the  enzyme  extracted  diminishes  wdth  the  length  of  time  of 
extraction,  though  much  more  rapidly  with  one  flour  than  wdth  another. 
It  is  further  found  that  proteolysts  when  present  in  flour  assist  in  the  main- 
tenance of  the  activity  of  its  amylase.  The  extraction  of  amylase  in  the 
presence  of  papain  (a  proteolytic  enzyme)  results  in  obtaining  a very  active 
preparation  of  amylase,  which  the  writers  have  provisionally  termed  “ total 
amylase.'"  The  action  of  this  amylase  on  the  flour  itself  is  shown  in  the 
“ autodigestion " experiments  described,  and  has  an  important  bearing 
on  the  carbon  dioxide  yield  of  flours.  To  both  subjects  a more  extended 
reference  is  subsequently  made.  After  examining  a number  of  samples 
of  flour  for  total  amylase,  the  wHters  arrive  at  the  conclusion  that  this 
factor  is  not  sufficient  to  assess  the  baking  value  of  a flour,  although  it  is  of 
considerable  importance.  Having  regard  to  the  protective  influence  of 
proteolysts,  they  deem  the  presence  of  these  bodies  as  being  valuable.  Con- 
sidering the  sample  F,  it  is  pointed  out  that  although  gas  is  generated  in  its 
dough  in  large  quantity,  yet  the  dough  has  no  gas-retaining  power  ; and 
this  was  found  to  be  associated  wdth  the  absence  of  any  active  proteolyst. 
Evidently  such  absence  Avas  no  obstacle  to  active  amylolytic  action,  and 
if  it  had  any  effect  it  must  have  been  due  to  the  absence  of  proteolytic  action 
proper  and  not  to  any  protection  afforded  to  amylase.  It  is  interesting  to 
note  that  D,  a very  Av^eak  flour,  had  a high  proportion  of  salts,  a result  Avhich 
may  be  compared  Avith  Wood's  experiments  on  the  relation  of  salts  to 
strength.  That  certain  flours  contain  a proteolytic  enzyme  is  proved  by 
the  gelatin  test  described,  but  the  action  of  this  active  proteolyst  is  regarded 
by  the  AVTiters  as  detrimental,  and  possibly  one  of  the  causes  of  rotten  gluten. 

462.  Strength  of  Wheat  Flours,  Baker  and  Hulton. — Simultaneously 
Avith  the  foregoing  research  by  Ford  and  Guthrie,  Baker  and  Hulton  inves- 
tigated the  problem  of  the  strength  of  flour.  The  Avriters  do  not  regard  it 
as  possible  that  the  estimation  of  one  constituent  or  the  determination  of 
one  physical  property  AviU  enable  the  chemist  to  affix  a baking  value  to  a 
flour,  when  this  value  is  the  resultant  of  more  than  one  factor.  They  attach 
considerable  importance  to  Wood's  observations  bearing  on  the  effect  of 


328 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


acids  and  salts  on  the  physical  character  of  glutens.  Although  his  results 
cannot  be  correlated  Avith  Bakers’  marks,  they  feel  sure  it  is  in  this  direction 
that  further  light  will  be  thrown  on  that  gluten-character  which,  in  their 
opinion,  forms  one  of  the  two  or  three  essentials  concerned  in  “ strength.” 

In  view  of  the  negative  results  so  far  obtained  by  many  investigators, 
they  regarded  a study  of  the  enzymic  activities  of  flour  as  likely  to  furnish 
results  of  interest.  Gluten  in  the  grain  of  wheat,  apart  from  its  interest 
to  the  baker,  exists  primarily  as  a reserve  of  nitrogenous  food  material  for 
the  young  embryo,  and  proteolytic  enzymes  are  consequently  secreted  to 
render  this  reserve  available  on  germination.  They  have  pointed  out  that 
the  appearance  of  white  of  egg  when  treated  in  presence  of  toluene  wdth  an 
aqueous  extract  of  flour  was  considerably  altered,  the  albumen  being  dis- 
integrated and  the  solution  becoming  milky,  but  that  there  was  no  increase 
of  soluble  nitrogen  in  aqueous  flour  extract  after  digestion  for  four  hours  at 
30°  C.  in  the  presence  of  white  of  egg.  Wlien  flour  extract  was  allow^ed  to 
act  on  its  separated  gluten  for  eighteen  hours  at  37°  C.,  there  was  practically 
no  evidence  of  solutiona  nd  no  alteration  in  the  appearance  of  the  gluten. 
These  and  other  experiments  demonstrated  the  absence  of  a soluble  proteo- 
lytic enzyme  capable  of  degrading  albumen  or  gluten.  This  led  them  to 
a consideration  of  the  role  played  by  the  enzymes  of  the  yeast  which  is  used 
in  bread-making. 

That  gluten  is  attacked  by  yeast  enzymes  is  shown  by  the  following 
experiments  : A quantity  of  flour  was  made  into  a dough  with  its  own 
w'eight  of  water  containing  5 per  cent,  of  bakers’  yeast.  The  dough  was  left 
for  four  hours  at  37°  C.,  and  the  soluble  nitrogen  expressed  as  protein  was 
found  to  be  2*7  per  cent.,  calculated  on  the  flour  after  corrections  for  pos- 
sible autodigestion  of  the  yeast  had  been  made.  The  same  flour  treated 
as  above  but  without  yeast  w as  found  to  yield  only  I *9  per  cent,  of  soluble 
nitrogen  as  protein.  This  increase  of  nearly  I per  cent,  must  obviously 
be  due  to  an  enzyme  other  than  erepsin  since  the  latter,  although  present 
in  yeast,  is  without  action  on  gluten.  It  is  probable  that  the  physical  char- 
acter of  the  gluten  may  be  much  modifled  during  the  early  stages  of  enzyme 
action  without  the  production  in  large  quantity  of  soluble  decomposition 
products.  In  this  connection  may  be  noted  the  profound  change  in  the 
viscosity  of  a starch  paste  under  the  influence  of  a trace  of  liquefying  dias- 
tase before  any  maltose  is  produced. 

In  common  with  other  observers  they  regard  the  carbon  dioxide  con- 
cerned in  the  rise  of  bread,  especially  in  the  later  stages  of  doughing  and 
the  early  period  of  baking,  as  being  formed  from  the  fermentation  of  the 
maltose  produced  by  the  action  of  the  diastase  on  the  flour  starch.  That 
such  sugar  is  maltose,  they  proved  by  the  osazone  test  and  the  production 
of  maltosazone.  They  have  also  observed  that  the  diastase  of  some  flours 
contains  a liquefying  enzyme;  in  others  this  is  either  absent  or  is  unable 
to  exert  its  influence.  It  might  be  supposed  that  the  flour  having  the  higher 
diastatic  capacity  w'ould  be  able  to  produce  more  maltose  and  therefore 
more  carbon  dioxide  in  a given  time,  and  wwld  be  the  stronger,  but  no 
such  direct  relation  can  be  traced  (see  upper  table,  next  page),  another  proof 
that  gas  retention  rather  than  gas  production  is  the  more  important  factor. 

During  the  fermentation  of  dough  the  wTiters  remark  that  the  total  volume 
of  gas  increases  roughly  as  the  strength,  but  a w'eak  flour  may  have  a diastatic 
power  as-  high  as  or  even  higher  than  a strong  flour.  Thus  it  appears  that  gas 
production  is  not  a function  of  diastase  ; but,  as  the  following  figures  show, 
(second  table,  next  page)  there  is  a connection  betw^een  the  gas  volume  and 
the  additional  matter  rendered  soluble  during  the  process  of  dougliing. 
The  cold  w'ater  soluble  extract  in  a series  of  flours  w^as  estimated  and  also 
tlie  soluble  matter  in  their  doughs,  wLich  had  been  kept  at  40°  C.  for  three 


THE  STRENGTH  OF  FLOUR. 


329 


Flour. 

Amylolytic  Power, 

Degrees  Lintner. 

Bakers’  Marks. 

14 

57-0 

90 

z 

40-0 

90 

X 

34-0 

40 

2 

32-0 

78 

3 

30-0 

80 

V 

27*0 

90 

U 

26-0 

91 

Y 

25-5 

95 

T 

25-5 

80 

W 

25*5 

76 

1 

25-0 

45 

hours.  Both  sets  of  estimations  were  corrected  for  soluble  nitrogenous 
substances  present.  The  increase,  measured  by  subtracting  one  from  the 
other,  can  only  be  due  to  maltose  formed  by  the  action  of  diastase. 


Flour,  j 

Per  cent,  of 
Matter 
soluble  in 
Water  at  15-5°  C. 

1 

Per  cent,  of  [ 
Matter  soluble  1 
in  Dough  when  i 
kept  at  40°  C. 
for  3 hours. 

1 

Difference 
= Maltose 
formed 
during 
Doughing. 

Volume 
of  Gas 
obtained 
from  Dough 
in  3 hours. 

Bakers’ 

Marks. 

1 

212 

3-60 

1-48 

78 

45 

X 

203 

4-41 

1-38 

84 

40 

w 

2-83 

5-38 

2-53 

145 

76 

3 

2-49 

5-53 

3-04 

155 

80 

Y 

2-69 

6.57 

3-88 

164 

95 

2 

3-19 

6-66 

3-45 

175 

78 

4 

4-19 

10-95 

6-75 

193 

90 

V ‘ 

2-83 

8-26 

5-42 

217 

90 

T 

2-84 

7-66 

4-82 

220 

80 

U 

2-65 

7-68 

5-02 

230 

91 

Z 

3-54 

11-65 

8-11 

270 

90 

It  should  not  be  forgotten  that  diastase,  estimated  in  degrees  Lintner, 
is  solely  saccharifying  diastase,  since  soluble  starch  is  the  material  acted 
upon,  and  the  figure  so  obtained  provides  no  measure  of  any  liquefying 
enzyme.  [Compare  with  experiments  by  one  of  the  authors,  given  on  page, 
136.] 

It  is  well  known  that  malt  extract  is  frequently  employed  by  bakers, 
presumably  with  the  object  of  increasing  the  amount  of  sugar  available 
for  gas  production.  This,  in  our  opinion,  it  does  by  providing  a starch 
liquefying  enzyme,  the  flours’  ovui  diastase  being  adequate  for  saccharifica- 
tion. This  view  was  supported  by  certain  recorded  experiments,  and 
accordingly  the  writers  considered  that  they  might  establish  a connection 
between  strength  and  the  relative  amount  of  a starch  liquefying  enzyme 
in  a flour.  If  the  gas  production  from  weak  flours  (which  is  usually  smaller 
than  in  strong  ones)  were  relatively  increased  in  a greater  proportion  by 
the  addition  of  a trace  of  liquefying  diastase,  than  in  the  case  of  flours  vdth 
large  gas  productions,  then  they  would  have  established  the  point  that 

1 The  wheat  of  Flour  4 in  this  series  was  damped  and  dried  before  grinding. 


330 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gas  diastase  ratio,  total  volume  of  gas,  and  incidentally  therefore,  to^ 
some  extent  strength,  were  functions  of  this  Hquefying  enzyme.  The  folio v'- 
ing  results,  in  their  opinion,  justify  this  conclusion  : — 


Flour. 

strength  in 
Bakers’ 
Marks. 

Diastatic 

Power. 

Gas  : 
Diastase 
Ratio. 

Gas  Production 
in  3 hours, 
c.c.  of  Carbon 
Dioxide. 

Gas  Production 
in  3 hours  in 
presence  of  0'25 
per  cent.  Malt, 
c.c.  of  Carbon 
Dioxide. 

Percentage 
increase  due  to 
added  Malt. 

X 

1 40 

34*0  ! 

1 

: 2-4 

84 

158 

88-0 

1 

I 45 

25-0 

1 

: 31 

78 

145 

86-0 

W i 

76 

25-5 

1 

: 5-6 

145 

194 

340 

2 

78 

320  ' 

1 

: 5-4 

175 

207 

18-0 

T ' 

80 

25-5 

1 

: 8-6 

220 

230 

4-5 

Z 

90 

40-0  i 

1 

: 6-7 

270 

250 

nil. 

u 

91 

26-0  1 

1 

: 8-9 

230 

248 

8-0 

Y 

1 

95 

25-5  i 

1 

: 6-4 

164 

235 

490 

This  table  shows  that  the  percentage  increase  in  gas  volume  due  to  the 
presence  of  liquefying  diastase  follows  inversely  the  amount  of  gas  originally 
liberated  by  the  dough  per  se.  The  percentage  increase  is  also  inversely 
proportional  to  the  bakers'  marks,  with  the  exception  of  Y.  This  flour, 
although  highly  marked,  yields  little  gas,  and  it  is  of  especial  interest  to 
note  that,  as  might  have  been  expected,  its  capacity  for  increase  in  presence 
of  malt  is  considerable,  thereby  bringing  it  into  line  wflth  other  flours  yield- 
ing small  volumes  of  gas.  In  the  case  of  Z,  a flour  giving  the  largest  gas 
production  of  all,  there  is  no  increase  in  the  volume  of  gas  obtained  by  the 
addition  of  malt,  and  presumably,  therefore,  there  is  already  present  lique- 
fying enzyme  in  such  quantity  as  not  to  be  capable  of  serious  augmentation 
by  such  a trace  of  malt  as  was  used. 

The  wTiters  regard  it  as  obvious  that  the  strength  of  a flour  must  be 
closely  connected  with  the  gluten,  although,  no  doubt,  the  presence  of 
enzymes,  soluble  carbohydrates,  and  mineral  constituents  all  play  a part. 
They  are  further  of  opinion  that  there  is  strong  presumptive  evidence  that 
the  glutenin  portion  of  the  gluten  molecule  is  that  which  possesses  enzymic 
activity.  (Jour.  Soc.  Chem.  lud.,  1908,  368.) 

Baker  and  Hulton's  paper  is  marked  by  their  recognition  of  the  fact 
that  the  strength  of  flour  depends  on  more  than  one  factor.  In  connection 
with  the  enzymic  activities  of  flour,  they  examined  the  effect  of  the  proteo- 
lytic enzymes  both  of  the  flour  itself  and  of  yeast  on  gluten.  It  is  of  special 
interest  to  note  the  recognition  they  give  to  the  possibilities  of  “ profound 
change  " in  physical  character  of  substances  such  as  gluten  without  any 
corresponding  chemical  changes  in  the  ordinary  use  of  that  term.  They 
also  consider  that  the  gas  concerned  in  the  rise  of  bread,  especially  in  the 
latter  stages  of  doughing  and  the  early  part  of  baking,  is  derived  from  the 
starch  of  the  flour.  Gas  retention  is  recognised  by  the  writers  as  more 
important  than  gas  production.  Careful  attention  was  given  to  the  amylo- 
lytic  enzymes  of  flour,  and  especially  to  the  presence  or  absence  of  a lique- 
fying enzyme.  This  they  regard  as  having  an  important  bearing  on  strength, 
and  produce  results  in  support  of  their  conclusion.  The  difference  in 
activity  of  flour  diastase  to  soluble  starch  and  starch  paste  respectively 
was  made  the  subject  of  experiments  by  one  of  the  authors,  and  recorded 
in  the  1895  edition  of  this  work.  In  summarising  their  conclusions,  the 
writers  emphasise  the  fact  of  its  close  connection  with  gluten. 


THE  STRENGTH  OF  FLOUR. 


331 


463.  Flour  Composition,  Shutt. — In  a bulletin  issued  by  the  Government 
of  Canada,  Shutt  gives  his  conclusions  based  on  the  results  of  analyses  of 
forty-two  samples  of  flour,  as  to  the  bearing  which  the  gliadin  and  other 
constituents  have  upon  the  baking  value  of  flour.  The  results  obtained 
show  that  whilst  there  is  a distinct  relationship  between  the  protein,  gliadin, 
and  wet  and  dry  gluten,  there  is  no  evidence  of  a definite  or  absolute  ratio. 
The  gliadin  value  is  not  definitely  related  either  to  the  nitrogenous  com- 
pounds or  to  the  “ baking  strength.'"  The  determinations  of  the  nitro- 
genous compounds  are  nevertheless  of  great  importance  in  judging  the 
value  of  a flour  for  bread-making  purposes,  especially  when  the  physical 
character  of  the  gluten  is  taken  into  account.  There  is  no  apparent  rela- 
tion between  the  ratio  of  total  ash  to  protein  and  “ baking-strength,"  nor 
between  the  ratio  of  ash  in  gluten  to  protein  and  “ baking-strength." 
[Canadian  Dept.  Agric.  Bull.,  1907  [57]  37.) 

Shutt  is  unable  to  find  any  definite  ratio  between  ghadin  and  other 
nitrogenous  compounds  or  strength.  He  also  emphasises  the  importance 
of  taking  into  account  the  physical  properties  of  the  gluten.  Further,  he 
is  unable  to  discover  any  relation  between  total  ash  and  strength  or  ash 
in  gluten  and  strength. 

464.  Sugar  in  Wheat  Flour,  Liebig— Liebig  states  that  the  sugars  in 
wheat  flour  are  glucose  and  sucrose,  the  respective  quantities  being  0*1- 
0*4  and  1-1*5  per  cent,  calculated  on  the  dry  substance.  By  means  of  a 
diastatic  enzyme,  maltose  is  formed  on  digesting  the  flour  with  water,  and 
also  in  the  dough.  On  maintaining  dough  at  a temperature  of  30-40°  C. 
for  fourteen  hours,  4*6  per  cent,  of  reducing  sugar  (reckoned  as  glucose) 
were  formed.  The  sucrose  content  on  the  other  hand  remains  fairly  con- 
stant. The  diastatic  power  (Lintner)  of  a wheat  flour  was  in  the  case  of 
dark  coarse  flours  about  one-third  of  that  of  an  average  malt,  and 
about  one-seventh  in  the  case  of  fine  flours.  These  are  values  with  soluble 
starch  ; the  starch-liquefying  power  is  insignificant  compared  with  that 
of  malt  diastase  (Lander,  Jahrhh.,  1909,  38,  251.) 

Liebig  also  recognizes  the  lack  of  starch-liquefying  enzyme  in  flour  as 
compared  vdth  malt. 

465.  Present-day  Conclusions.— In  paragraph  436,  in  the  early  part  of 
this  chapter,  it  is  laid  down  that  there  must  be  a sufficiency  of  sugar  or 
other  material  available  for  fermentation  in  the  dough.  In  what  may  be 
referred  to  as  the  summary  of  views  current  in  1895,  it  is  suggested  that 
the  presence  of  much  maltose  is  evidence  of  unsoundness,  and  reference  has 
already  been  made  to  the  fact  that  certain  very  strong  flours  contain  com- 
paratively little  sugar,  while  in  others  which  are  weak  sugar  is  present 
in  comparatively  large  quantity.  Flours  from  sprouted  wheats  are  com- 
paratively weak  and  with  high  maltose  contents  ; in  such  cases  there  is 
probably  practical  agreement  Avith  the  view  that  the  high  sugar  is’asso- 
ciated  Avith  low  strength.  If  wheat  is  gathered  and  milled  in  an  unripe 
condition,  there  is  again  a lack  of  strength,  and  yet  there  is  a relatively 
high  percentage  of  sugar.  Thus  in  the  account  given  in  paragraph  427  of 
Teller’s  researches  on  the  composition  of  wheat  at  different  stages  of  ripe- 
ness, it  is  shown  unripe  wheat  contains  more  sucrose,  2*95  to  1*43  per  cent., 
than  ripe  wheat  at  I *44  per  cent.  (There  is  one  rather  anomalous  figure,  viz. 
1*28  per  cent,  for  the  third  day  immediately  preceding  ripeness). 

Parenti  states  (paragraph  446)  that  the  reducing  sugar  of  flours  is  reduced 
during  fermentation  from  2*31  to  0*13  per  cent.,  that  is  a consumption  of 
2*18  per  cent.  In  Wood’s  paper,  paragraph  453,  he  lays  great  stress  on 
the  importance  of  sugar  as  a factor  of  strength,  and  remarks  of  one  flour,  G 
that  it  cannot  make  large  loaves  because  of  the  low  percentage  of  sugar 


332 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


present.  He  accordingly  tested  the  flours  by  a fermentation  test,  and  20  grams 
of  flour  and  20  grams  of  water  (112  quarts  to  the  sack)  and  0*5  grams  of  yeast 
(7  lbs.  to  the  sack)  were  taken  and  fermented  at  35°  C.  (95°  F.)  for  twenty- 
four  hours,  at  the  end  of  which  time  the  volume  of  gas  was  observed.  In  the 
case  of  the  lowest  flours,  G and  L^,  there  was  a gas  equivalent  of  1*6  per 
cent,  of  sugar,  while  the  highest  amounted  to  2*6  per  cent,  of  sugar.  The 
flour  G is  that  before  referred  to  as  being  deficient  in  sugar.  Armstrong 
states  yet  more  deflnitely  that  the  amount  of  sugar  actually  present  in  flour 
is  not  sufficient  to  give  the  necessary  volume  of  gas  required  in  bread-making. 
Again,  Ford  and  Guthrie  are  of  opinion  that  the  greater  part  of  the 
carbon  dioxide  liberated  in  panary  fermentation  must  be  derived  from  the 
starch  of  the  flour.  They  quote  an  experiment  in  which  on  fermenting  a 
flour  in  the  usual  way  with  yeast  they  obtained  350  c.c.  of  gas  from  20 
grams  of  flour,  which  corresponds  roughly  wuth  the  fermentation  of  1*3 
gram  of  sugar  or  6*5  per  cent,  of  the  flour.  Direct  estimations  gave  respec- 
tively 0*82  per  cent,  of  sucrose  and  0*1  per  cent,  of  reducing  sugar  in  the 
flour,  special  precautions  being  taken  to  eliminate  all  diastase  from  the  flour 
before  the  determination.  Baker  and  Hulton  also  express  the  opinion 
that  the  carbon  dioxide  concerned  in  the  rise  of  bread  during  the  later 
doughing  and  the  early  period  of  baking  has  as  its  source  the  starch  of  the 
flour. 


466.  Fermentation  Experiments  by  Authors. — In  view  of  these  opinions 
it  was  thought  advisable  by  the  authors  to  make  some  fermentation  experi- 
ments which  should  be  as  nearly  as  possible  conducted  under  precisely 
the  same  conditions  as  occur  in  actual  practice.  A baker  was  asked  for 
samples  of  respectively  the  strongest  and  weakest  flours  he  then  had  in 
stock,  and  supplied  the  following  : — 

A.  A strong  Spring  American  Patent  Flour. 

B.  A very  weak  French  Flour. 

Doughs  were  made  from  each  of  these  in  the  follovdng  manner  : — 


A 

Flour,  200  grams  at  17°  C. 

Salt,  2 grams. 

Yeast,  1 gram. 

Water,  100  grams  at  31°  C. 


B 

203  grams  at  17*5°  C. 
2 grams. 

1 gram. 

100  grams  at  31°  C. 


Dough,  303  grams  at  26°  C.  303  grams  at  26*5°  C. 

The  following  are  the  proportions  of  each  ingredient  per  sack — salt, 
2 lbs.  13  oz.  ; yeast,  1 lb.  6f  oz.  ; and  water,  56  quarts. 

After  being  made,  the  doughs  were  transferred  to  enamelled  steel  beakers 


and  weighed  ; after  fermentation  they  were 
ing  results  : — 

again  weighed  with 

the  follow- 

A 

B 

Weight  of  unfermented  dough 

..  301-6 

298-7 

,,  ,,  fermented  dough  . . 

. . 299-8 

296-6 

Loss  in  weight  during  fermentation  . . 

1-8 

2-1 

Immediately  after  being  weighed,  each  beaker  was  placed  in  a contain- 
ing vessel  of  convenient  size,  and  the  lid  fastened  down  so  as  to  make  an 
air-tight  joint.  This  vessel  was  in  turn  submerged  in  a water-bath  main- 
tained at  a constant  temperature  of  25°  C.  (77°  F.)  and  fermentation  was 
allowed  to  proceed  for  six  hours.  To  the  containing  vessel  was  attached 
a leading  tube  through  which  the  generated  gas  passed,  and  was  collected 


THE  STRENGTH  OF  FLOUR. 


333 


over  brine  and  measured  in  the  usual  way.  (The  whole  apparatus  is 
described  in  paragraph  612,  Figure  43.)  The  times  and  temperatures 
vere  practically  copied  from  those  in  actual  use,  and  covered  the  whole 
period  to  the  arrestment  of  fermentation  in  the  oven,  they  were  in  fact 
the  same  as  those  which  the  baker  employed  when  working  with  flours  of 
this  stronger  type.  The  volume  of  gas  was  read  at  the  expiration  of  one  and 
a half-hours  and  every  half-hour  until  the  six  hours  had  elapsed.  The  results 
are  recorded  in  the  following  table.  The  gas  was  collected  at  a temperature 
of  18*0°  C.  and  760  m.m.  of  pressure. 


Time. 

A.  Strong  Flour. 

Gas  Evolved. 

B.  Weak  Flour.  Gas  Evolved. 

Total. 

Per  IlalMiour. 

Total. 

Per  Half-hour. 

Start  . . 

0-0 

0-0 

IJ  hours 

40-0 ') 

35-0, 

1 

23 

I 

36 

■2  „ 

63-0) 

1 

71-o| 

j 

47 

1 

( 

i 54 

2i  „ 

llO-Ot 

125-0 

1 

47 

1 

I 

70 

3 „ 

157-0. 

195-0 

1 

59 

1 

^ ' 82 

3^5, 

216-0 

277-0 1 

1 

r 

80 

^ 100 

4 „ 

i 296-0 

1 377-0 1 

1 

1 1 

1 r 

87 

1 

1 

; ' 105 

,, 

383-0 

482-0 

1 

1 

117 

1 

1 

t ^ 125 

5 „ 

500 -C 

607-0^ 

1 

1 

j 

92 

140 

5i  „ 

592-0 

1 747-0; 

j 

1. 

j 

113 

136 

6 „ 

705-0 ' 

883-0 

1 

From  the  volume  of  gas  evolved,  its  weight,  and  that  of  the  sugar  re- 
quired for  its  production,  are  easily  calculated.  The  results  of  such  calcula- 
tions are  given  in  the  upper  table  on  the  folio wdng  page.  In 
each  pair  of  columns  the  first  contains  the  various  data  as  calculated 
on  the  dough  as  used  ; in  the  second  column  they  are  reckoned  as  percentages 
of  the  dried  or  water-free  solids  of  the  dough.  In  view  of  the  very  small 
loss  of  weight  by  the  dough  during  fermentation,  it  must  be  assumed  that 
very  nearly  all  the  alcohol  remains  in  the  dough  and  is  weighed  therewith. 

A number  of  analytical  determinations  were  also  made  on  the  flours  and 
doughs  at  the  close  of  fermentation  respectively,  the  results  of  which  appear  in 
the  lower  table  on  page  334.  For  soluble  matters  10  per  cent,  solutions  of  the 
flours  were  prepared,  allowed  to  stand  for  half-an-hour  in  the  cold,  and 
filtered  bright.  No  attempt  was  made  to  discriminate  between  previously 
existing  sugars  and  those  produced  from  the  starch  during  this  period  of  stand- 
ing, as  sugars  from  the  both  sources  are  in  practice  equally  available  for 
gas  production  from  the  start  of  the  fermentation.  With  the  fermented 
doughs,  these  were  kneaded  until  as  much  as  possible  of  the  gas  had  been 
forced  out ; 50  grams  were  then  taken,  and  washed  for  gluten  in  successive  smafl 


334 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Doughs. 

Particulars. 

A.  Strong  Flour. 

B.  Weak  Flour. 

1 

1 

As 

Used. 

Dried 

Solids. 

1 

As 

Used. 

Dried 

Solids. 

Total  volume  of  gas  evolved  in  c.c 

705 

883 

Weight  of  gas  evolved  (CO2),  in  grams 
Approximate  weight  of  sugar  required  for 

1-30 

— 

1-63 

— 

the  production  of  the  gas,  in  grams 
Approximate  weight  of  alcohol  produced, 

2-82 

— 

3-53 

in  grams 

Weight  of  sugar  required  per  100  grams  of 

141 

i 

1-76 

dough,  i.e.  per  cent.  . . 

Weight  of  alcohol  produced  per  100  grams 

0-93 

1-58 

M8 

2-05 

of  dough,  i.e.  per  cent. 

Loss  of  weight  during  fermentation,  per 

046 

0*79 

0-59 

1-02 

cent. 

Sum  of  the  two  preceding  quantities, 
which  practically  agrees  with  sugar 

0-59 

1-00 

0-70 

1-22 

1 required 

1-05 

‘ 1-79 

L29 

2-24 

A.  Strong  Flour. 


Constituents.  j 

i 

Flour. 

Fermented  Dough. 

As  Used.  ! 

Diisd  Solids. 

As  Used. 

Dried  Solids. 

Moisture 

11-29 

1 

41-11 

_ 

Total  Solids 

88-71  ’ 

100-00 

58-89 

100-00 

Gluten,  Wet 

j 40-5  * 

45-64 

29-90 

50-77 

„ Dry  

1 13-5 

! 15-21 

9-54 

16-20 

,,  Ratio  of  Wet  to  Dry 

3-0 

3-0 

3-1 

3-1 

„ True  

10-23 

11-53 

7-32 

12-43 

,,  ,,  Percentage  of  Dry  . . 

75-57 

75-57 

76-67 

76-67 

Soluble  extract 

6-12 

6-90 

4-12 

6-99 

Reducing  Sugars  as  Maltose 

1-48 

1-67 

1-00 

1-70 

Non-reducing  Sugars  as  Sucrose  . . 

j 0-93 

1-05 

Nil 

Nil 

Added  Salt 

— 

1 

0-66 

1-12 

B.  Weak  Flour. 

Moisture  . . . . . . . . 

13-50 

1 

42-58 



Total  Solids  . . . . . . 

86-50 

100-00 

57-42 

100-00 

Gluten,  Wet 

30-5 

35-26 

22-22 

38-68 

,,  Rry  

11-1 

12-83 

7-10 

12-36 

,,  Ratio  of  Wet  to  Dry 

2-7 

2-7 

3-1 

3-1 

n . True  

8-74 

10-10 

5-89 

10-25 

,,  ,,  Percentage  of  Dry 

Soluble  Extract 

78-74 

78-74 

83-04 

83-04 

5-76 

: 6-66 

5-44 

9-47 

Reducing  Sugars  as  Maltose 

1-17 

1-35 

1-30 

2-26 

Non-reducing  Sugars  as  Sucrose.  . 

0-21 

0-24 

, 0-10 

0-17 

Added  Salt 

— 

0-66 

1-15 

THE  STRENGTH  OF  FLOUR. 


335 


quantities  of  tap  water  (from  deep  wells  in  the  chalk).  The  washings  were 
added  together  and  made  up  to  500  c. c.,mcluding  the  starch,  for  the  presence 
of  which  no  correction  was  made.  This  solution  was  filtered  bright  and  soluble 
matters  estimated  in  the  filtrate.  It  is  interesting  to  place  on  record  that 
on  washing  the  dough  with  distilled  water,  at  the  end  of  the  second  wash- 
ing the  gluten,  which  at  first  separated  out  very  well,  became  completely 
disintegrated.  There  was  no  tendency  in  this  direction  when  tap  water  was 
employed. 

Baking  tests  were  also  made  on  the  flours  with  the  following  results  : — 
In  each  case  24  oz.  of  flour  were  taken.  With  A,  13 J oz.  of  water  were 
required  to  make  the  dough,  and  with  B,  12  oz.  of  water.  With  these  quan- 
tities the  consistency  of  the  two  doughs  was  the  same.  They  were  worked 
with  the  same  quantities  of  yeast  and  salt,  and  at  the  same  temperature. 
The  dough  from  A was  springy,  tough,  and  wiry  ; that  from  B was  dead 
and  putty-like.  The  A dough  was  ready  for  the  oven  in  five  hours, 
and  B in  four  hours.  They  were  baked  into  crusty  loaves,  and  awarded 
bakers"  marks  for  strength,  on  the  scale  of  maximum  100,  minimum  50. 
The  awards  were  A,  95,  B,  60  marks.  If  there  was  any  error  it  was  in  the 
direction  of  undue  generosity  to  B.  The  difference  in  water-absorbing 
capacity  is  equivalent  to  17*5  lbs.  or  7 quarts  to  the  sack  'of  280  lbs.,  and  this 
figure  agrees  with  the  vendor  baker’s  estimate  of  the  water-absorbing  power 
of  the  two  flours  in  practice. 

467.  Consideration  of  Results. — In  examining  the  results,  the  first  subject 
is  naturally  that  of  the  gas  evolved.  The  quantity  obtained  from  the 
strong  flour  must  be  regarded  as  amply  sufficient  to  ensure  the  production 
of  a bold  well -risen  loaf.  The  evolution  increased  until  the  end  of  the  fifth 
hour,  when  for  one  reading  there  Avas  a diminution.  The  slight  irregu- 
larities were  apparently  due  to  the  sudden  liberation  of  gas  by  the  “ drop- 
ping ” of  the  dough.  The  sugars  obtained  by  direct  extraction  of  the  flour 
by  cold  water,  2*72  per  cent.  Avere  considerably  in  excess  of  the  amount 
required  in  order  to  produce  the  evolved  gas,  viz.  1*58  per  cent.  In  each 
case,  and  throughout  these  comparisons,  the  percentages  on  the  dried  solids 
are  taken.  Turning  next  to  the  Aveak  flour,  there  is  considerably  more 
gas  evolved  over  the  Avhole  process  of  fermentation,  and  even  to  the  end 
the  evolution  is  more  rapid  than  A\Ith  the  strong  flour.  The  gas  Avas  evolved 
much  more  regularly,  because,  no  doubt,  of  the  less  retaining  poAA'er  (greater 
porosity)  of  the  Aveak  dough.  The  total  sugars  of  this  flour  amounted  to 
1*59  per  cent,  and  are  less  than  those  required  for  the  fermentation,  viz. 
2*05  per  cent.,  by  0*46  per  cent.  Against  this  it  must  be  remembered  that 
AAuth  such  a very  weak  flour  a much  shorter  period  of  fermentation  AA’ould 
be  essential  to  the  production  of  a moderately  passable  loaf,  than  AA^ould 
be  employed  Avith  the  stronger  flour.  A baker  Avould  probably  give  it  no 
more  than  from  tAA^o-thirds  to  four-fifths  of  the  amount  of  fermentation 
that  Avould  be  employed  for  the  strong  flour.  If  the  dough  AA^ere  got  into 
the  oven  at  the  end  of  the  fifth  hour,  607  c.c.  of  gas  AA^ould  have  been  evolved, 
as  against  588  c.c.,  which  amount  is  tAvo-thirds  of  the  883  c.c.  produced  in 
six  hours.  This  latter  amount  of  gas  requires  for  its  production  1*37  per 
cent,  of  sugar  as  expressed  on  the  dried  solids  of  the  dough,  leaving  a margin 
of  0*22  per  cent,  surplus  of  sugars  in  the  flour.  Taking  these  as  extreme 
types  of  strong  and  Aveak  flours,  the  pre-existent  sugars  of  flour,  together  with 
those  readily-formed  in  the  cold  on  the  addition  of  water,  are  in  themselves  sufficient 
for  the  production  of  all  gases  necessary  in  the  normal  fermentation  of  dough. 

Comparing  the  above  conclusion  AAuth  those  previously  cited,  Parenti 
notes  a consumption  of  2*18  per  cent,  of  the  flour,  amounting  to  about 
2*45  per  cent,  of  the  dried  solids,  AA'hile  in  the  case  of  the  authors’  very  strong 
flour,  1*58  per  cent,  only  of  sugars  Avere  required.  Judging  by  recognised 


336 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


English  methods,  Parenti's  doughs  were  considerably  over-fermented.  In 
Wood’s  fermentation  tests,  volumes  of  gas  ranging  from  131  to  345  c.c.  were 
obtained  from  20  grams  of  flour.  Multiplying  these  numbers  by  10  in 
order  to  compare  the  results  with  those  obtained  by  the  authors  from  200 
grams  of  flour,  there  is  a minimum  of  1,310  c.c.  as  against  a working  re- 
quirement of  705  c.c.  with  a strong  and  about  600  c.c.  with  a weak  flour. 
Similarly,  when  Ford  and  Guthrie  produced  350  c.c.  from  20  grams  of  flour 
(or  3,500  c.c.  from  200  grams),  they  obtained  about  five  times  as  much 
gas  as  is  evolved  in  the  normal  fermentation  of  dough. 

If  in  flours  of  ordinary  type,  whether  weak  or  strong,  there  are  always 
sufficient  pre-existent  and  readily-formed  sugars  for  the  usual  require- 
ments of  fermentation,  it  is  not  very  apparent  that  any  excess  of  amylolytic 
enzymes  over  those  necessary  for  the  production  of  such  readily  formed 
sugars,  has  any  direct  bearing  on  the  strength  of  the  flour.  (And  the  enzy- 
mic activity  of  all  flours  seems  sufficient  for  this  particular  purpose.)  But 
so  far  as  these  recent  experiments  go,  the  following  calculations  are  of 
interest  : — 


A.  Strong  Flour. 

B.  Weak  Flour. 

Soluble  Extract  in  Fermented  Dough 

6-99 

9-47 

Subtract  added  Salt  . . 

0-66 

0-66 

6-33 

8-81 

Add  Sugar  consumed  in  Fermentation 

1-58 

2-05 

7-91 

1086 

Substract  Soluble  Extract  of  the  Flour  . . 

6-90 

G66 

Soluble  Matters  produced  during  Fermentation  . . 

I-OI 

4.20 

In  these  particular  instances  there  is,  during 

ordinary 

fermentation,. 

over  four  times  as  much  diastatic  action  with  the  weak  than  there  is  with 
the  strong  flour.  This  result  seems  to  be  borne  out  by  general  experience 
for  strong  flours  are  liable  to  produce  dry  flavourless  bread,  while  that 
from  the  weaker  varieties  is  more  usually  moist  and  sweet. 

Humphries  informs  the  authors  that  with  the  flours  of  some  very  hard, 
ricy  wheats,  there  are  insufficient  pre-existent  and  readily -formed  sugars 
to  yield  the  quantity  of  gas  produced  in  even  the  limited  fermen- 
tation here  described.  It  is  suggested  that  such  flours  are,  however, 
scarcely  commercial  varieties  in  their  separate  state. 

468.  Gas-retaining  Power. — Comparatively  recently  the  opinion  has 
been  expressed  that  the  strength  of  flour  depends  not  upon  its  gas-producing 
but  on  its  gas-retaining  power.  This  is  only  another  way  of  formulating 
the  old  view  that  strength  depends  on  the  gluten  of  the  flour. 

469.  Relation  between  Gluten  and  Proteins  of  Flour. — The  foregoing 
researches  serve  to  throw  considerable  light  on  the  actual  composition  of 
gluten  and  its  relation  to  the  total  proteins  of  the  flour.  Norton  made  a 
very  complete  analysis  of  crude  gluten,  which  he  found  to  contain  about 
74  per  cent,  of  gliadin  and  glutenin,  and  about  7 per  cent,  of  a non-gluten 
protein.  • The  remaining  19  per  cent,  was  made  up  of  fat,  carbohydrates, 
fibre,  and  mineral  matter.  These  figures  confirm  the  opinion  in  the  1895- 
edition  that  crude  gluten  contains  about  80  per  cent,  of  proteins  as  deter- 
mined by  nitrogen  estimation.  Norton  points  out  that  the  percentage  of 
crude  gluten  from  flour  roughly  approximates  to  that  of  total  protein 
present,  there  being  a loss  of  non-gluten  proteins,  more  or  less  balanced 


THE  STRENGTH  OF  FLOUR. 


337 


by  the  retention  of  non-protein  matters  ; in  his  view  evidently  the  pro- 
portions of  the  two  are  regarded  as  being  fairly  constant.  In  consequence 
he  regards  crude  gluten  as  but  a very  rough  expression  of  the  protein  con- 
tent, and  the  determination  as  of  but  little  worth  in  the  valuation  of  flours. 
Chamberlain  goes  over  much  the  same  ground,  and  substantially  agrees 
with  Norton.  He  flnds  about  75  per  cent,  of  proteins,  and  25  per  cent, 
of  non-proteins  in  crude  gluten.  Of  all  the  proteins  present  in  wheat  60 
to  65  per  cent,  are  found  in  the  gluten,  and  35  to  40  per  cent,  are  lost  in 
the  washings.  Evidently  all  the  bran  proteins  must  of  necessity  be  thus 
lost.  He  agrees  that  the  balance  of  losses  of  proteins  and  retention  of 
non-proteins  make  the  gluten  estimations  agree  roughly  with  the  total 
proteins  calculated  from  total  nitrogen.  A further  and  more  important 
conclusion  is  that  gluten  contains  less  total  protein  than  the  sum  of  the 
ghadin  and  glutenin  present  in  the  wheat  by  about  15  per  cent.  ; and  con- 
sequently that  the  loss  of  proteins  in  the  determination  of  gluten  is  at  the 
expense  of  gliadin  or  glutenin,  the  true  gluten  proteins  of  wheat.  He 
- therefore  regards  gluten  determinations  as  not  being  able  to  yield  any 
information  that  cannot  be  obtained  from  determinations  of  total  pro- 
teins and  alcohol-soluble  and  insoluble  proteins.  If  Norton's  and  Cham- 
berlain's results  both  be  regarded  as  accurate,  Chamberlain's  15  per  cent, 
loss  would  have  to  be  increased  by  the  7 per  cent,  of  globuhn  contained 
in  the  gluten,  which  is  included  in  the  total  proteins,  but  is  neither  gliadin 
nor  glutenin.  Dealing  however  with  the  15  per  cent,  loss  only,  in  the 
case  of  a flour  yielding  39  per  cent,  of  wet  gluten,  and  13  per  cent,  of  crude 
dry  gluten,  such  weights  ought  to  have  been,  had  there  been  no  loss,  44*85 
per  cent,  of  wet,  and  14*95  per  cent,  of  dry  gluten.  The  question  suggests 
itself,  to  what  is  such  loss  due  ? Is  it  caused  by  an  actual  failure  to  recover 
some  6 per  cent,  of  wet  gluten  that  was  present  in  the  dough  and  necessarily 
lost  in  the  washing ; or  at  the  time  of  washing  was  this  gluten,  or  its  com- 
ponents gliadin  and  glutenin,  in  a non-elastic  and  non-adhesive  condition, 
and  therefore  not  gluten  at  all  in  the  sense  of  possessing  the  physical  pro- 
perties of  wet  gluten  ? To  the  authors,  the  latter  alternative  seems  the 
more  probable,  and  consequently  there  may  be  present  in  dough,  gliadin 
and  glutenin  constituents  Avhich  at  the  time  of  making  the  estimation  are 
not  fulfilling  the  physical  functions  of  gluten  proper  in  the  usually  accepted 
sense  of  the  term.  Some  light  is  thrown  on  this  point  by  the  gluten  deter- 
minations made  on  the  flours  used  for  the  fermentation  experiments  just 
described.  That  of  the  strong  flour.  A,  was  when  washed  at  the  end  of 
an  hour’s  standing,  and  dried,  15*21  per  cent,  of  the  dried  solids.  The 
corresponding  fermented  dough  yielded  16*20  per  cent.  In  the  case  of 
the  weak  flour,  however,  there  was  a » slight  diminution  in  the  dry  gluten 
of  the  fermented  dough.  Nitrogen  determinations  were  accordingly  made 
on  the  whole  four  dry  glutens,  and  the  results  calculated  into  “ true  gluten.” 
These  figures  are  included  in  the  foregoing  table  on  page  334.  The  true 
gluten  obtained  from  the  fermented  dough  of  the  strong  flour  is  12*43  as 
against  11*53  per  cent,  on  the  flour.  There  is  also  an  increase  with  the 
weak  flour,  the  figures  being  10*25  on  the  dough  as  against  10*10  per  cent, 
on  the  flour.  During  fermentation  therefore  the  quantity  of  proteins 
which  possess  the  physical  character  of  gluten  show  an  increase.  Recent 
research  must  therefore  be  regarded  as  confirming  the  veiw  that  crude 
gluten  contains  from  20  to  25  per  cent,  of  non-proteins.  Further,  it  goes 
to  show  that  about  7 per  cent,  of  the  proteins  present  may  be  non-gluten 
protein,  and  that  of  the  gluten  proteins  (gliadin  and  glutenin)  some  15 
per  cent,  of  the  total  in  the  wheat  or  flour  are  not  obtained  in  the  gluten. 
Obviously,  a dry  gluten  determination  must  not  be  regarded  as  an  estimation  of 
the  proteins  of  the  wheat  or  flour. 


338 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  above  limitation  being  accepted,  the  question  naturally  arises 
as  to  what  a gluten  determination  really  is.  The  best  answer  seems  to 
be  that  a gluten  determination  is  an  estimation  of  the  amount  of  those  bodies  which 
are  in  such  a physical  condition  as  to  impart  elasticity  and  gas-retaining  power  to 
the  dough  at  the  time  when  the  determination  is  made.  The  exact  nature  of 
its  constituents  is  of  secondary  importance,  and  whether  gluten  consists 
of  protein  matter  only,  or  of  75  to  80  per  cent,  of  proteins  together  with  a 
complement  of  non-proteins,  does  not  affect  the  value  for  the  purposes  of 
comparison  of  the  results  obtained.  A point  worthy  of  consideration 
about  gluten  estimations  is  wliether  they  might  not  be  advantageously 
made  on  the  dough  at  a stage  of  its  fermentation  when  its  strength  is  of 
the  greatest  importance.  That  stage  by  general  consent  w^ould  be  when 
the  dough  is  ready  to  go  into  the  oven.  This  end  might  be  attained  by 
making  the  flour  to  be  used  for  this  estimation  into  a dough  with  yeast, 
salt,  and  water,  in  the  proportions  and  at  the  temperatures  employed  in 
actual  bread-making.  The  doughs  w^ould  then  be  kept  in  a fermenting 
vessel  at  a constant  temperature,  such  as  that  employed  in  the  recently 
described  experiments,  for  a time  similar  to  that  taken  in  the  bakehouse 
for  the  completion  of  the  fermentation  of  the  dough.  In  order  to  prevent 
drying,  the  atmosphere  of  such  a vessel  should  be  kept  saturated  with  mois- 
ture. If  the  gas  evolution  were  simultaneously  observed  a still  more  com- 
plete record  of  the  behaviour  and  properties  of  the  flour  w^ould  be  obtained. 

470.  Mechanical  Disintegration  of  Gluten. — It  is  a fact  well-known  in 
the  experience  of  bakers  that  mechanical  over-kneading  kills,  or  “ fells,” 
a dough.  The  consequence  is  that  a dough,  which  w^ould  ordinarily  pro- 
duce a bold  w^eU-risen  loaf,  becomes  soft  and  putty-like,  and  yields  small 
sodden  bread,  just  as  through  a very  weak  flour  had  been  used  in  its  pre- 
paration. In  practice,  any  serious  injury  from  this  cause  is  avoided  by 
careful  watching  ; further,  the  dough  has  wLile  standing  the  pow'er  of 
recovery  in  some  degree  of  its  strength.  It  is  not  so  well-known  that  such 
over-kneading  materially  alters  the  physical  character  of  the  gluten.  In 
order  to  investigate  the  point,  the  following  experiments  were  made  w ith 
a very  strong  American  wheat  flour. 

No.  1.  The  flour  was  made  into  a dough  by  hand-kneading,  and  the 
various  determinations  carried  out  on  the  gluten  from  this  dough. 

The  total  soluble  matter  and  proteins  soluble  in  water  w^ere  determined 
direct  on  the  flour. 

The  w^ater  absorption  by  viscometer  was  determined  on  hand-made 
doughs,  and  amounted  to  70  quarts  per  sack. 

Nos.  2 and  3 w'ere  machine-made  in  the  manner  described. 

No.  2.  Water  w'as  taken  in  the  proportion  of  66  quarts  to  the  sack. 
The  machine  w^as  turned  until  the  flour  and  water  w ere  incorporated  : 
30  additional  revolutions  were  then  given.  The  dough  stood  an  hour, 
and  was  then  passed  through  the  viscometer.  The  time  is  given  below. 
For  gluten  and  other  determinations  31*8  grams  of  dough  w^ere  taken 
at  tlie  close  of  the  hour,  being  equivalent  to  20  gram-S  of  flour.  The  water 
used  for  w'ashing  gluten  was  reserved  and  made  up  to  1,000  c.c.  On  this 
solution,  the  soluble  proteins  and  other  soluble  matter  were  determined. 

No.  3.  Water  w^as  again  taken  in  the  proportion  of  66  quarts  to  the 
sack.  After  incorporation,  250  revolutions  were  given  to  the  machine. 
The  dough  stood  one  hour,  and  w'as  then  passed  through  the  viscometer. 
It  W’as  then  returned  to  the  machine,  and  received  another  250  revolutions. 
The  dough  w'as  now"  very  sticky  to  handle,  and  w’as  once  more  tested  by 
the  viscometer.  It  was  again  returned  to  the  machine  and  subjected  to 
another  250  revolutions.  By  this  time  it  w as  much  more  sticky,  presenting 


THE  STRENGTH  OF  FLOUR. 


339 


in  fact  the  appearance  of  bird-lime.  The  dough  could  be  drawn  out  into 
long  threads,  was  very  moist,  and  in  fact  appeared  as  though  it  contained 
much  more  water. 

The  following  are  the  viscometer  results  : — 

No.  2.  No.  3. 


After  one  hour 

After  another  250  revolutions 

After  a further  250  revolutions 


873  seconds. 


520  seconds. 


16 

7 


In  No.  3,  compared  with  No.  2,  there  is  a marked  diminution  in  water- 
absorbing power.  But  with  the  further  kneading,  No.  3 dough  became 
altogether  altered  in  properties,  and  had  in  fact  entirely  lost  the  charac- 
teristics of  a bread-making  dough. 


Effect  of  Mechanical  Treatment  on  Doughs. 


No.  1. 

1 No.  2. 

No.  3. 

Wet  Gluten 

42-30 

37-10 

35-45 

Ratio  of  Wet  to  Dry  Gluten 

2-8 

2-9 

3-1 

Dry  Gluten 

15-02 

12-70 

11-44 

Non-protein  Matter  in  Dry  Gluten.  . 

4-25 

1-40 

0-92 

True  Gluten  . . 

10-77 

11-30 

10-52 

Gliadin  ex  Gluten  . . . . . . 

7-36 

7-19  i 

6-24 

Glutenin  ex  Gluten,  by  difference  . . 

3-41 

4-11 

4-28 

Percentages  on  Dry  Gluten. 

Non-protein  Matter  in  Dry  Gluten 

28-29 

11-02 

8-04 

Gliadin 

49-00 

56-61 

54-54 

Glutenin 

22-71 

32-37 

37-42 

Total  Proteins  . . • . . 

12-95 

12-95 

12-95 

Proteins  soluble  in  Water  . . 

1-49 

1-26 

1-56 

,,  recovered  as  True  Gluten 

10-77 

11-30 

10-52 

,,  lost  in  washing  Gluten 

0-69 

0-39 

0-87 

Gliadin  ex  Flour 

6-43 

6-43 

6-43 

Glutenin  ex  Flour,  by  difference 

5-03 

— 

— - 

Percentages  on  Total  Proteins. 

Proteins  soluble  in  Water.  . 

11-50 

9-73 

12-04 

,,  recovered  as  True  Gluten 

83-16 

87-26 

81-23 

,,  lost  in  washing  Gluten.  . 

5-34 

3-01 

6-73 

Gliadin  ex  Flour  . . 

49-65 

49-65 

49-65 

Glutenin  ex  Flour,  by  difference 

! 38-85 

— 

— 

Non-protein  Matter  soluble  in  Water 

3-35 

5-82 

6-00 

On  making  gluten  tests.  No.  2 yielded  less  wet  and  dry  gluten  than 
No.  1,  but  washed  quite  normally.  The  true  gluten  was  slightly  the  higher, 
showing  that  the  loss  in  washing  was  almost  entirely  non-protein  matter. 
On  proceeding  to  wash  gluten  from  No.  3,  the  whole  dough  broke  down 
into  a flocculent  and  non-coherent  mass.  It  was  only  by  pouring  this  on 
to  a sieve,  and  collecting  by  pressing  the  particles  together,  that  any  gluten 
was  recovered.  When  thus  obtained  the  gluten  was  soft  and  flabby  and 
possessed  scarcely  any  coherence  or  elasticity,  whereas  those  of  Nos.  I 
and  2 were  tough  and  resilient.  Although  so  profoundly  altered  in  physical 
character,  the  chemical  composition  of  the  gluten  does  not  show  corre- 
spondingly great  changes,  the  principal  being  a diminution  in  the  gliadin, 


340 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


which  was  estimated  by  the  “ starch  method.’'  (See  Chapter  XXVIII). 
Determinations  were  made  on  the  collected  washing  water,  but  these  can- 
not be  regarded  as  perfectly  accurate,  since  some  loss  is  inevitable.  They 
may  however  be  taken  as  comparative  between  Nos.  2 and  3.  A decidedly 
greater  amount  of  protein  was  soluble  in  water  in  No.  3 than  No.  2.  The 
total  loss  of  protein  in  washing  was  also  higher,  though  in  none  of  the  experi- 
ments was  the  loss  very  great.  The  whole  of  the  results  are  set  out  in  detail 
in  the  following  table.  They  go  to  show  that  not  only  is  the  gluten  phy- 
sically altered,  but  there  is  some  change  also  in  solubility  in  various  media. 
In  addition  to  the  alteration  in  the  gluten,  there  is  a considerable  increase 
in  the  amount  of  soluble  non-protein  Kiatter. 

The  interesting  point  of  these  experiments  is  that  by  simple  m-echanical 
attrition  of  the  dough,  profound  changes  are  made  in  the  character  of  the 
gluten  and  apparently  in  the  same  direction  as  those  which  result  from 
treatment  mth  dilute  acids  as  carried  out  by  Wood.  The  authors  are 
conducting  a systematic  investigation  of  the  effects  produced  on  dough 
and  gluten  by  mechanical  treatment  and  hope  at  an  early  date  to  make  a 
communication  on  the  subject. 

471.  Relation  of  Gliadin  Ratio  to  Strength  of  Flour. — With  Osborne  and 
Voorhees’  demonstrations  of  the  insoluble  proteins  of  flour  consisting  of 
gliadin  and  glutenin,  a very  natural  development  of  inquiry  was  along 
the  lines  foreshadowed  in  the  1895  edition  of  this  work,  and  consisting  of 
determinations  of  the  total  amount  of  each  of  these  present  in  a flour, 
and  the  ratio  such  amounts  bore  to  each  other.  Guthrie,  Fleurent,  Snyder, 
and  others  have  contributed  to  this  research,  and  each  has  employed  methods 
of  determination  mmre  or  less  original.  A consequence  is  that  different 
proportions  of  the  total  protein  is  returned  as  gliadin  or  glutenin  according 
to  the  process  adopted,  and  as  a result  differing  conclusions  have  been 
formed  as  to  the  m.ost  desirable  ratio  between  these  bodies.  Guthrie  ob- 
tained from  about  59  to  78  per  cent,  of  gluten  as  glutenin  (which  figure  also 
includes  the  non-proteins).  He  concludes  that  a preponderance  of  glutenin 
is  preferable,  and  that  increased  gliadin  produces  a weak,  sticky,  and  in- 
elastic gluten.  With  a totally  different  m_ethod  of  extraction,  Fleurent 
found  his  best  results  with  25  per  cent,  of  glutenin  to  75  per  cent,  of  gliadin, 
and  a deterioration  with  a departure  in  either  direction.  Guess  extracted 
his  gliadin  direct  from  the  flour,  and  without  any  limitation  found  that 
the  more  gliadin  present,  the  more  elastic  and  better  was  the  gluten.  Snyder 
places  on  record  that  the  alcohol-soluble  portion  of  flour  protein  (gliadin) 
may  vary  from  as  high  as  70  to  as  low  as  45  per  cent.  Avith  only  minor  varia- 
tions in  the  size  of  the  loaf  or  the  bread-making  value  of  the  flour.  Further 
lie  regards  gliadin  as  not  being  of  uniform  composition.  In  Chamberlain’s 
opinion,  so-called  gliadin  contains  also  albumin  and  globulin.  Wood 
finds  that  flours  which  are  at  the  extreme  ends  of  the  scale  of  strength 
may  have  substantially  the  sam_e  proportions  of  gliadin  to  total  nitrogen. 
Snyder  in  fact  shows  that  widely  different  gliadin  contents  may  occur  in 
practically  identical  flours  : Wood  supplements  this  by  showing  that 
widely  different  flours  may  be  practically  identical  in  their  gliadin  contents. 
In  other  words,  glutens  containing  the  same  proportions  of  gliadin  and 
glutenin  may  be  either  weak  or  strong.  The  natural  conclusion  is  that 
strength  or  weakness  is  independent  of  the  ratio  of  gliadin  to  glutenin  in  the  gluten. 
As  gluten  is  not  subjected  to  the  solvent  action  of  70  per  cent,  alcohol  in 
the  process  of  bread-making,  it  does  not  seem  that  it  would  necessarily 
follow  that  a connection  must  as  of  course  exist  between  the  degree  of  solu- 
bility in  that  reagent  and  the  strength  of  the  flour. 

Gluten  is  probably  a loose  compound  of  gliadin  and  glutenin  in  varying 


THE  STRENGTH  OF  FLOUR.  341 

proportions,  and  its  qualities  as  a whole,  from  the  bread-making  stand- 
point, are  apparently  not  closely  related  to  its  protein  composition.  For 
its  marked  differences  in  properties,  the  most  likely  explanation  is  that 
they  are  based  on  variations  in  physical  rather  than  chemical  character. 
This  fact  has  been  recognised  by  Baker  and  Hulton,  who  in  discussing 
emzyme  action  on  gluten  remark  that  “ the  physical  character  of  the  gluten 
may  be  much  modified  during  the  early  stages  of  emzyme  action  without 
the  production  in  large  quantity  of  soluble  decomposition  products.  In 
this  connection  may  be  noted  the,  profound  change  in  the  viscosity  of  a 
starch  paste  under  the  influence  of  a trace  of  liquefying  diastase  before  any 
maltose  is  produced.'’  Strength,  then,  must  he  regarded  as  depending  on  the 
quantity  and  physical  character  of  the  gluten  of  the  flour. 

472.  Conditions  affecting  the  Quantity  and  Physical  Character  of  Gluten. — 

These  naturally  constitute  the  subject  of  the  next  line  of  inquiry.  As 
to  quantity,  that  is  largely  a question  of  selection  of  seed  and  circumstances 
of  cultivation,  and  therefore  mostly  lies  outside  the  scope  of  the  p4;esent 
work.  Much  careful  and  successful  research  has,  however,  been  devoted 
to  such  questions  as  the  choice  of  seed,  and  effect  of  soil,  climate,  and  man- 
uring, on  the  development  of  the  gluten  content  of  wheat.  But  the  miller 
and  baker  (in  those  capacities)  have  only  to  manipulate  and  do  their 
best  with  wheats  and  flour  as  they  find  them.  Turning  next  to  the  ques- 
tion of  physical  character  and  how  it  may  be  modified,  that  also  is  a pro- 
blem which  largely  lies  within  the  domain  of  the  agriculturalist  and  his 
advisers  rather  than  the  miller  and  baker.  Again,  the  choice  of  seed  and 
other  factors  previously  mentioned  have  a most  important  bearing  on 
the  subject.  In  particular,  the  researches  of  Wood  have  evidently  been 
conducted  with  the  object  of  assisting  the  farmer  in  gromng  strong  wheats, 
and  with  a full  realisation  of  limits  and  possibilities  which  do  not  so  much 
concern  the  subsequent  handlers  of  wheat  and  flour.  Among  the  factors 
w^hich  have  been  suggested  as  modifying  agents  on  gluten  are  sugar,  pro- 
teolytic enzymes,  acidity,  and  certain  mineral  salts  of  the  wheat  or  flour. 
Sugar  has  already  been  discussed,  and  reference  has  been  made  to  its  power 
of  increasing  the  proportion  of  gluten  which  is  soluble  in  70  per  cent,  alcohol. 
Ford  and  Guthrie  point  out  that  certain  flours  contain  a proteolytic  enzyme 
which  has  an  extremely  detrimental  effect  on  the  tenacity  of  the  gluten, 
and  described  methods  by  which  this  body  can  be  detected.  Baker  and 
Hulton  have  also  investigated  the  matter  of  the  presence  of  proteolysts 
in  flour.  They,  however,  came  to  the  conclusion  as  far  as  concerned  the 
flours  examined  by  them,  that  there  was  no  soluble  proteolytic  enzyme 
in  flour  capable  of  degrading  albumin  or  gluten  with  the  production  of 
soluble  nitrogenous  bodies.  They  And,  on  the  other  hand,  that  the  gluten 
in  dough  is  attacked  by  yeast  enzymes,  with  an  increase  in  the  amount 
of  soluble  proteins.  It  is  in  this  connection  that  they  make  the  remark 
before  quoted  as  to  the  possibility  of  profound  physical  changes  in  gluten, 
with  no  (or  but  little)  chemical  change.  Fermentation,  as  already  shown, 
may  increase  the  quantity  of  protein  recoverable  as  gluten  ; it  also  possesses 
the  property  of  materially,  softening  that  body,  and  at  the  same  time  in- 
creasing the  amount  of  protein  which  while  insoluble  in  water  is  soluble  in 
70  per  cent,  alcohol.  The  following  results  were  obtained  on  a flour  by 
the  authors.  The  percentage  of  constituents  is  calculated  on  the  dried 
sohds  of  the  flour,  and  the  fermented  dough  respectively : — 


Dry  Gluten 

Flour. 

. . 12-14 

Fermented  Dough. 

..  11-08 

True  ,,  (Proteins) 

. . 10-33 

. . 10-14 

Ghadin  ex  Gluten  . . 

2-80 

3-20 

Glutenin 

. . 7-53 

6-94 

Ratio  of  Gluten  to  Gliadin 

. . 2-7 

2-2 

342 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Any  reagent  or  action  by  which  this  change  is  assited  is  therefore 
aiding  in  the  development  of  the  strength  of  the  dough,  provided  such 
changes  are  not  thereby  carried  too  far,  since  the  weakness  of  an  over- 
worked dough  is  probably  due  to  the  same  causes  as  those  which  are  bene- 
ficial in  a lesser  degree.  Although  strength  seems  independent  of  the 
original  proportions  in  which  ghadin  and  glutenin  exist  in  a flour,  yet  those 
changes  during  fermentation  which  result  in  increased  elasticity  of  the 
dough  are  usually  accompanied  by  an  increase  in  the  alcohol-soluble  content 
of  the  gluten.  Both  sugar  and  proteolysts  may  therefore  in  this  manner 
exert  a beneficial  influence  on  the  dough. 

Snyder  finds  that  any  shght  increase  of  acidity  in  the  grain  diminishes 
the  percentage  of  gliadin  (paragraph  448).  On  the  other  hand,  Wood 
(paragraph  455),  finds  acidity  to  have  no  relation  to  strength.  Wood 
states  that  certain  acids  in  small  quantity  have  a marked  disintegrating 
action  on  gluten,  which  effect  increases  with  the  degree  of  acidity,  until 
vith  further  concentration  a reverse  action  occurs,  and  at  a certain  point 
the  effect  of  the  acid  is  to  harden  the  gluten  and  render  it  more  elastic 
and  coherent  than  was  its  original  condition.  Other  acids  show  no  such 
reverse  action,  but  up  to  any  hmit  of  concentration  effect  a disintegration 
which  becomes  more  rapid  as  the  acidity  increases.  These  results  are  de- 
scribed in  detail  in  paragraph  455.  It  is  difficult  to  say  whether  in  actual 
dough  fermentation  the  effect  of  acid  on  gluten  is  in  its  earher  stages  capable 
of  inducing  beneficial  changes  thereon.  At  the  later  and  overworked 
stages,  the  acid  developed  is  probably  one  of  the  factors  in  carrying  the 
changes  in  gluten  to  a condition  of  less  gas-retaining  power. 

473.  Effect  of  Mineral  Salts  on  Gluten. — Wood  has  made  a series  of 
most  important  investigations  as  to  the  effect  of  certain  mineral  salts  on 
gluten.  For  a description  of  these  in  detail,  the  preceding  abstract  of 
his  paper  must  be  referred  to  (paragraph  455).  His  most  recent  conclu- 
sions are  embodied  in  a personal  communication  from  Professor  Wood, 
kindly  made  for  the  purposes  of  this  book,  and  contained  in  paragraph  459. 
One  point  may  be  mentioned  in  connection  with  these  experiments.  As 
Wood  immersed  his  gluten  in  solutions  of  acids  and  salts  in  pieces  about  the 
thickness  of  a pencil,  it  took  forty-eight  hours  for  such  pieces  to  become 
permeated  with  the  solutions.  He  therefore  expresses  the  opinion  that  it 
would  be  impossible  to  check  them  by  experiments  on  dough,  since  the 
latter  could  not  possibly  be  allowed  to  stand  that  length  of  time  before 
baking.  But  this  objection  would  probably  not  be  so  serious  as  Wood  antici- 
pates. The  reason  why  forty-eight  hours  are  required  for  the  gluten  is  the 
extreme  slowness  with  which  solutions  can  diffuse  through  a mass  of  gluten. 
In  making  corresponding  tests  with  flour,  it  is  not  necessary  to  immerse 
the  dough  in  the  solutions,  as  the  salts  can  be  mixed  in  the  finely  powdered 
form  with  the  flour  itself  before  doughing.  Or  still  better,  they  could  be 
dissolved  in  the  requisite  proportions  in  the  water  used  for  doughing  pur- 
poses. Fermentation  could  then  be  allowed  to  proceed  in  the  ordinary 
manner,  and  observations  made  during  the  progress,  and  on  the  baked 
loaf.  In  determining  wLether  a wheat  shall  be  weak  or  strong.  Wood 
is  of  the  opinion  that  the  effective  action  of  beneficial  salts  occurs  during 
the  growth  of  the  grain,  while  the  endosperm  is  being  formed  and  is  in  a 
comparatively  milky  stage.  In  order  to  improve  wheat  at  this  stage, 
the  SE^lts  must  evidently  be  obtained  from  the  soil.  Experiments 
made  by  Chitty  and  one  of  the  authors  go  to  show  that  wheats  may  be 
improved  in  this  direction,  when  in  the  hands  of  the  miller,  by  treat- 
ment of  the  grain  itself  (paragraph  652).  Additions  to  the  flour  as 
flour,  or  at  the  time  of  doughing,  are  also  capable  of  effecting  material 
improvements.  Interesting  examples  of  this  are  the  at  one  time  prevalent 


THE  STRENGTH  OF  FLOUR. 


343 


addition  of  alum  when  flours  were  exceedingly  weak,  and  the  baker’s  well- 
knoAMi  expedient  of  using  an  extra  quantity  of  salt  with  a very  weak  flour. 
Though  the  former  addition  is  condemned  on  other  grounds,  its  undoubtedly 
considerably  improved  the  strength  of  the  flour.  So,  too,  salt  has  a decided 
” binding  ” effect  on  a weak  and  runny  dough.  The  problem  cannot  at 
present  be  regarded  as  completely  worked  out,  but  the  results  already 
obtained,  confirmed  as  they  are  by  practical  experience,  go  to  show  that 
the  presence  or  absence  of  certain  mineral  salts  is  a most  important  factor  in  deter- 
mining the  strength  or  weakness  of  gluten  and  consequently  of  flour.  Bearing 
in  mind  that  flour  of  itself  is  toxic  to  some  varieties  of  yeast,  and  that 
certain  mineral  salts  act  as  an  antidote  to  the  poisonous  action,  it  is  of 
interest  to  note  that  some  mineral  salts  increase  the  strength  of  gluten. 
Indirectly  they  may  further  benefit  the  working  properties  of  a flour  by 
nullifying  its  toxic  action  to  yeast. 

474.  Gluten  Determinations. — ^From  the  foregoing  expressions  of  opinion, 
it  vlll  be  gathered  that  the  authors  continue  to  attach  importance  to  properly 
conducted  gluten  determinations.  The  estimation  of  wet  gluten  is  a mea- 
sure of  the  amount  of  that  constituent  of  flour,  which  by  its  physical  char- 
acter determines  the  quality  and  nature  of  the  resultant  dough  and  bread. 
It  further  determines  this  in  a way  which  is  comparatively  easy  of  per- 
formance and  affords  results  which  are  readily  understood  by  all  concerned. 
In  the  hands  of  an  expert  flour  valuer,  not  only  the  quantity  of  gluten,  but 
its  appearance  and  general  characters  give  most  valuable  indications  as 
to  the  tjrpe  and  quality  of  a flour,  even  though  they  cannot  be  expressed 
in  percentages  or  other  forms  of  figures.  The  following  remark  of  Saunders 
is  an  interesting  confirmation  of  the  practical  value  of  the  gluten  test : — 
“ In  addition  to  the  final  baking  tests  I have  used  for  several  years  a simple 
chewing  test  (taking  only  a few  kernels  of  wheat)  as  a valuable  guide  to 
gluten  strength  and  probable  baking  strength  in  the  earlier  stages  of  selec- 
tion. This  test  was  advocated  as  an  essential  aid  in  the  selection  of  cross- 
bred varieties  of  wheat  in  the  Bulletin  on  Quahty  in  Wheat,  pubhshed  at 
Ottawa,  October,  1907.”  {Supplement  4,  June,  1910,  p.  29,  Jour.  Board  of 
Agriculture.) 


CHAPTER  XVI. 


CHEMICAL  COMPOSITION  OF  FLOUR  AND  OTHER  MILLING  PRODUCTS. 

475.  Properties. — Among  the  general  properties  of  flour,  that  of 
Strength  has  been  deemed  of  suflicient  importance  to  warrant  its  treatment 
in  a separate  chapter.  Flour  also  possesses  certain  other  physical  characters 
of  which  some  explanation  must  be  given.  These  include  Colour  and 
Water- absorbing  power.  For  scientific  purposes  it  is  necessary  to  have 
not  only  means  of  judging  and  comparing  these,  but  also  some  method  of 
registering  for  future  reference,  and  for  the  institution  of  comparisons 
between  the  results  obtained  by  one  observer  and  those  of  another.  In 
order  to  do  this,  these  properties  must  in  some  way  be  expressed  numeri- 
cally. 

The  whole  subject  of  these  various  measurements  is  exhaustively  dis- 
cussed in  a subsequent  chapter  on  Flour-Testing,  but  as  in  this  section 
a number  of  analyses  are  quoted,  in  which  estimations  of  colour,  etc.,  are 
inserted,  a brief  mention  is  here  made  of  the  principle  of  the  method  by 
Avhich  these  have  been  judged. 

476.  Colour. — Every  miller  and  baker  will  be  acquainted  with  the 
ordinary  method,  devised  by  Pekar,  of  determining  the  colour  of  a sample 
of  flour  by  compressing  a small  quantity  into  a thin  cake  or  slab,  which 
is  wetted  and  allowed  to  dry.  The  depth  and  character  of  the  colour  are 
then  observed.  This  test  has  been  in  use  for  some  time,  and  answers  admir- 
ably the  purpose  of  comparing  the  relative  colour  of  two  or  more  samples. 
In  some  of  the  earher  tests  here  quoted,  one  of  the  authors  employed  graduated 
scales  of  colour  prepared  by  himself  ; the  one  of  a yellow  tint,  for  com- 
parison with  high-class  flours  ; the  other  grey,  for  estimations  on  flours 
of  the  lower  grades.  The  nearer  the  colour  approaches  white,  the  less  the 
number  assigned  to  it  on  the  scale.  Thus  the  Grey  Scale  starts  with  a 
very  light  tint,  marked  “ I,"'  and  finishes  with  a dark  tint,  marked  “ 16."" 
The  whole  of  the  tints  have  an  intensity  proportional  to  their  number  ; 
thus  No.  2 is  exactly  twice  as  dark  as  No.  1,  while  No.  8 is  four  times  as 
dark  as  No.  2. 

The  Yellow  Scale,  being  intended  for  patent  flours  only,  is  not  extended 
so  far  as  the  Grey  Scale.  It  is  difficult  to  compare  the  two  scales  with 
each  other,  because  the  colours  are  dissimilar  ; but,  in  intensity.  No.  I 
yellow  is  about  equal  to  IJ  grey  ; No.  10  yellow  is  three  times  as  dark 
as  1 yellow,  and  about  equal  in  intensity  to  4J  grey.  The  colours  deepen 
in  intensity  by  regular  intervals  from  No.  I to  No.  10  yellow. 

In  using  these  scales  for  testing  purposes,  it  was  found  that  in  some 
samples  the  colour  was  intermediate  in  character  between  the  two  scales  ; 
thus,  some  flours  were  grey,  with  just  a tint  of  yellow  ; others  were  very 
nearly  like  the  Yellow  Scale,  but  rather  grey  beside  it  ; these  properties 
were  indicated  by  the  use  of  two  letters,  thus  “7*5  G.y.""  This  means 
that  the  flour  approached  7*5,  on  the  Grey  Scale,  in  depth  of  tint,  but 
that  it  was  rather  yellower  than  the  scale,  but  stiU  nearer  the  grey  than 

344 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  345 


the  yellow  series  of  tints.  On  the  other  hand,  6 Y.g.  means  that  the  colour 
was  matched  and  numbered  on  the  Yellow  Scale,  but  that  it  was  somewhat 
grey  in  character. 

477.  Water-Absorbing  Power. — The  water-absorbing  power  of  a sample 
of  flour  is  one  of  the  most  important  properties  it  possesses,  and  its  deter- 
mination is  of  great  value  to  both  miller  and  baker.  It  not  only  governs 
the  yield  in  bread  of  the  sample,  but  also  affords  evidence  of  its  other 
qualities.  Hence,  water-absorbing  determinations  are  valuable  in  several 
respects.  Although  not  always  applied  in  precisely  the  same  sense,  for 
our  present  purpose.  Water-absorbing  power  may  be  defined  as  the  measure  of 
the  water-absorbing  and  retaining  power  of  the  fiour,or  of  the  water  absorbed  by 
the  fiour  in  order  to  produce  a dough  of  definite  consistency : it  always  being 
understood  that  the  dough  shall  be  eapable  of  yielding  a well-risen  and 
properly  cooked  loaf  without  clamminess.  The  water-absorbing  power 
of  the  flour  from  any  particular  wheat  is  in  practice  governed  by  the  way 

. in  which  it  has  been  treated  during  milling.  Thus  an  excess  of  water 
used  in  the  conditioning  process  will  reveal  itself  in  a deficiency  in  the  water- 
absorbing capacity  of  the  flour. 

When  in  the  following  analyses  the  water-absorbing  power  is-  quoted, 
the  figures  give  the  number  of  quarts  of  water  per  sack  (280  lbs.)  of  flour 
required  to  produce  a dough  of  a standard  stiffness.  The  standard  em- 
ployed is  an  arbitrary  one,  based  on  results  obtained  with  the  author’s 
“ viscometer  ” (see  Flour  Testing,  Chapter  XXVI),  and  practically  cor- 
responds in  stiffness  with  a very  slack  cottage  ” dough. 

478.  Composition  of  Roller  Milling  Products. — As  milling  is  an  art  in 

which  the  wheat  is  ehanged  into  flour  and  offal,  not  by  one  but  by  many 
operations,  it  is  a matter,  not  only  of  interest,  but  of  importance,  that  it 
should  be  known  where  the  constituents  of  the  wheat  go  as  eaeh  successive 
step  in  gradual  reduction  is  taken,  and  as  the  resulting  products  are  gradually 
purified  and  separated  into  flours  of  different  qualities  and  offals. 

One  of  the  authors,  some  time  ago,  personally  collected  thirty-four 
samples  of  such  products  from  a large  roller  mill,  of  which  he  made  fairly 
complete  analyses.  The  subjoined  table  gives  the  moisture,  soluble  extract, 
soluble  proteins,  wet  and  dry  gluten,  fat,  cellulose,  ash,  and  phosphoric 
acid  of  each  sample,  and  also  the  colour  of  the  flours,  according  to  the 
scale,  already  described. 

The  wheat  mixture  in  use  was  composed  of  three  parts  Winter  Ameri- 
can, one  part  Spring  American,  and  two  parts  of  Californian  ; it  weighed 
64  lbs.  per  bushel. 

Each  “ break  ” or  step  in  the  reduetion  of  the  grain  results  in  the  pro- 
duction of  “ tailings,”  which  are  the  largest  particles  remaining  ; semolina, 
consisting  of  smaller  partieles  ; and  flour.  The  tailings  of  the  one  break 
constitute  the  feed  of  the  next. 

479.  Tailings. — Studying  first  the  tailings  from  each  break,  the  moisture 
contained  is  somewhat  less  than  that  of  the  wheat  ; this  is  doubtless  the 
result  of  the  heat  evolved  during  the  milling.  The  soluble  extraet,  soluble 
proteins,  ash,  phosphoric  acid,  fat,  and  cellulose  gradually  increase  ; this 
follows  from  the  fact  that  more  and  more  of  the  endosperm  is  being  removed 
at  each  break,  the  tailings  being  gradually  reduced  to  simple  bran.  The 
gluten  at  first  somewhat  increases  ; this  is  due  to  the  semolina  and  flour 
of  the  earlier  breaks  being  made  chiefly  from  the  heart  of  the  grain.  The 
portion  of  endosperm  nearest  the  bran  contains  the  most  gluten,  and  so 
that  eonstituent  rises,  until  at  the  fifth  break  there  is  a slight  fall  ; but 
from  the  tailings  of  the  sixth  and  seventh  break  no  gluten  is  recoverable. 


COMPOSITION  OF  ROLLER  MILLING  PRODUCTS. 


346 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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COMPOSITION  OF  ROLLER  MILLING  PRODUCTS— Cora/tnitcrf. 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  347 


Cellulose. 

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t The  two  t,  t>  refer  the  one  to  the  other. 


348 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


That,  in  the  sixth  break  tailings,  gluten  is  nevertheless  present  is  shown 
by  the  quantity  which  is  obtained  from  the  bran  flour. 

480.  Break  Flours. — Glancing  at  the  break  flours,  that  from  the  first 
break  contains  very  little  gluten,  but  high  quantities  of  cellulose  and  ash. 
The  first  break  is  really  a splitting  break,  having  as  its  object  the  removal 
of  the  so-called  “ crease-dirt.^’  The  second  and  third  break  flour  is  richer 
in  gluten,  but  is  very  low  in  colour.  The  fourth  and  fifth  break  flour  is 
low  in  gluten,  but  much  better  in  colour.  The  sixth  break  flour  falls  off 
in  colour,  but  is  higher  in  gluten.  The  seventh  break  or  bran  flour  is  high 
in  gluten  and  fat,  low  in  soluble  extract,  and  specially  so  in  colour. 

481.  Middlings  and  Semolinas. — The  middlings  from  the  first  break 
contain  a fair  amount  of  gluten,  but  the  fat  and  cellulose  are  very  high.  The 
first  break  middlings  and  flour  are  treated  as  offal,  and  are  at  this  stage 
finally  separated  from  the  other  products  of  reduction.  The  granular 
products  of  the  second  and  third  breaks  are  separated  into  “ coarse  semo- 
lina ” and  coarse  middlings,  the  latter  being  the  finer  of  the  two.  These 
consist  of  fragments  of  the  endosperm  mixed  with  small  pieces  of  offal, 
composed  principally  of  broken  bran.  The  products  of  the  fourth  and 
fifth  breaks  are  also  similarly  divided.  The  coarse  semolinas  from  the 
whole  four  breaks  then  go  together  to  a set  of  wind  or  gravity  purifiers, 
and  are  separated  into  three  products  according  to  their  density.  The 
densest  of  these  three  is  the  nearly  pure  broken  endosperm  ; the  middle 
is  a mixture  of  endosperm  and  branny  matter  ; while  the  back  spouts  yield- 
only  very  fine  branny  offal.  The  coarse  middlings  from  the  whole  four 
breaks  are  likewise  similarly  treated  over  another  set  of  purifiers. 

Considering  first  the  coarse  semolinas,  that  from  the  second  and  third 
breaks  is  lower  in  gluten  than  that  from  the  fourth  and  fifth.  It  is  also 
lower  in  fat,  but  higher  in  cellulose.  The  bran  fragments  are  found  more 
plentifully  in  the  second  and  third  break  semolina,  while  the  germ  finds 
its  way  into  that  of  the  fourth  and  fifth  breaks.  The  coarse  middlings, 
in  each  case,  are  richer  in  Hour-forming  constituents,  consisting  of  more 
nearly  pure  fragments  of  endosperm  ; those  from  the  latter  pair  of  breaks 
being  the  richer  of  the  two.  The  next  point  is  the  nature  of  the  respective 
products  of  the  separation  effected  by  the  gravity  purifiers  on  the  coarse 
semolinas.  Passing  reference  has  already  been  made  to  those  bodies. 
The  densest  bodies,  which  consequently  find  their  way  into  the  front  spouts, 
contain  a good  proportion  of  gluten,  the  fat  and  cellulose  being  high.  The 
material  of  the  middle  spouts  also  contains  a considerable  quantity  of  flour 
forming  compounds,  but  no  gluten  was  recoverable  from  the  yield  of  the 
back  spouts.  The  series  of  purifiers  treating  coarse  middlings  yields  from 
the  front  spouts  purified  middlings,  containing  very  little  matter  foreign 
to  flour — the  gluten  is  high,  while  ash  and  fat  are  low — the  cellulose  is  some- 
what high.  The  arrangements  of  the  mill  permitted  of  the  taking  of  a 
sample  of  flour  that  was  being  made  from  these  purified  middlings  only  ; 
its  analysis  is  given  in  the  table.  This  flour  is  lower  in  gluten  than  the 
straight  grade,  but  is  better  coloured  than  even  the  patent.  The  middle 
spouts  give  a material  low  in  ash,  but  higher  in  cellulose,  than  the  corre- 
sponding yield  of  the  purifiers  treating  coarse  semolinas.  The  back  spouts 
product  yields  no  gluten,  but  a high  proportion  of  fat,  and  particularly  of 
cellulose! 

482.  Flours. — The  whole  of  the  flour  from  the  various  breaks,  and  the 
reductions  of  the  semolinas  (excepting  those  of  the  first  break),  go  to  form 
the  straight  grade  flour  : this  constitutes  the  whole  of  the  marketable 
flour  produced  by  the  grain.  The  water  of  the  straight  grade  flour  is  almost 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  349 


identical  with  that  of  the  clean  wheat  : the  soluble  extract  is  lower,  but  the 
soluble  proteins  run  slightly  higher.  The  gluten  is  much  higher,  amount- 
ing to  8*54  against  6*04  per  cent.  The  ash  and  phosphoric  acid,  have 
decreased  considerably  ; falling  from  L53  and  0*78  to  0*22  and  0*12.  The 

(3  06 

0,^0  (duplicates) 

to  0 *252  and  0 *34.  The  colour  is  4*5  G.,  being  exceedingly  good  for  a straight 
grade  flour.  This  straight  grade  was  divided  into  a small  percentage  of 
“ Patent,''  and  a “ Households  " or  “ Bakers’  " flour.  The  patent  flour 
contains  rather  less  water  than  the  straight  grade  ; also  less  gluten  and 
fat.  The  cellulose  of  the  patent  flour  is  slightly  higher  than  that  of  the 
straight  grade.  The  households  flour  is  considerably  richer  in  gluten, 
but  in  other  chemical  constituents  closely  resembles  the  patent.  The 
quantities  of  fat,  ash,  phosphoric  acid,  and  cellulose,  are  in  each  exceedingly 
small,  so  that  but  little  difference  is , observed  between  any  of  the  three 
flours.  The  cellulose  of  flour  is  in  so  finely  divided  a condition  that  the 
difference  in  texture  of  two  Alter  papers  might  make  a perceptible  difference 
in  two  cellulose  estimations  in  the  same  sample.  There  is  not  the  marked 
difference  in  quality  between  the  patent  and  households  flours  observable 
sometimes  : the  households  has,  in  fact,  not  been  impoverished  in  order 
to  produce  a quantity  of  a very  high-class  patent  flour.  In  colour  the 
patent  stands  at  3*6  G.,  the  straight  grade  at  4*5  G.,  and  the  households 
at  5-9  G. 

483.  Offals  : Fine  Sharps. — This  material,  also  sometimes  termed 
“ seconds,"  looks  as  good  as  what  one  sometimes  sees  sold  as  flour.  It 
contains  a considerable  quantity  of  gluten,  7*0,  more  in  fact  than  some 
of  the  flours  : but  as  might  be  expected,  the  fat,  ash,  and  cellulose  are  high. 
The  soluble  extract  is  also  very  high. 

484.  Coarse  Sharps,  or  Thirds. — These  also  contain  gluten,  but  only  a 
very  small  amount,  2*64.  The  soluble  extract  and  proteins  are  very  high, 
so  also  are  the  fat  and  cellulose. 

485.  Rolled  Sharps. — The  soluble  extract  and  proteins  are  even  higher 
than  in  the  preceding  ; ash,  phosphoric  acid,  and  fat  are  also  high. 

486.  Bran. — The  bran  presents  several  very  interesting  matters  for 
observation  : as  might  be  expected,  gluten  is  absent,  and  cellulose  is  very 
high,  amounting  to  over  18*30  of  the  whole  substance.  The  bran  also 
yields  more  ash  and  phosphoric  acid  than  any  other  portion  of  the  grain. 
With  regard  to  bran,  it  was  thought  worth  while  to  make  an  additional 
estimation  of  the  amount  of  ash  actually  present  in  the  soluble  extract  ; 
the  result  of  this  analysis  gave  2*61  per  cent.  It  does  not  follow  that  if 
the  burned  ash  were  treated  with  water  that  a larger  percentage  would 
not  be  dissolved.  The  explanation  is  that  the  physical  condition  of  the 
bran,  in  broad  flakes,  is  such  that,  whatever  soluble  matter  are  locked  up 
within  it,  they  do  not  yield  themselves  to  treatment  with  water.  This 
is  exemplified  in  the  case  of  the  soluble  extract  and  proteins  : compared 
with  the  rolled  sharps  the  bran  yields  but  9 *33  and  1 *20  respectively,  against 
14*95  and  3*92  in  the  sharps.  Another  sample  of  the  bran  was  treated 
with  water  for  24  hours,  and  then  the  soluble  extract  and  proteins  deter- 
mined— the  results  were  13*1  and  2*2  per  cent.,  still  being  less  than  in  the 
sharps.  These  figures  afford  additional  proof  of  the  fact  that  whatever 
soluble  constituents  the  bran  may  possess,  they  do  not  readily  yield  them- 
selves to  water  as  a solvent  : that  this  is  due  to  the  physical  condition  is 
shown  by  the  sharps,  which  also  consist  of  the  integument  of  the  grain, 
yielding  so  much  more  soluble  matter,  the  principal  difference  simply 


350 


THE  TECHNOLOGY  OF  BHEAD-MAKING. 


being  that  the  latter  is  much  more  finely  broken.  The  protein  matter  of 
the  bran  consists  largely  of  cerealin,  with  which  the  large  cuboidal  cells 
of  the  inner  bran  are  filled.  This  body  is  actively  diastatic,  but  is  altogether 
devoid  of  gluten-like  properties. 

487.  Fluff. — A sample  of  this  was  collected  from  the  pockets  in  Smith’s 
purifiers  ; the  cellulose  is  higher  than  that  of  flour,  to  which  the  fluff  is 
somewhat  smilar  in  appearance.  It  contains  a fair  amount  of  gluten, 
and  also  of  fat.  In  appearance  this  substance  looks  as  though  it  contained 
a good  deal  of  the  parenchymatous  cellulose  of  the  endosperm  of  the  grain. 
On  consulting  figure  32,  page  258,  it  will  be  seen  that  the  starch  granules 
are  held  together  in  larger  cells  by  walls  of  cellulose  ; these  walls  most 
probably  find  their  way  into  the  fluff  and  stive  dust. 

488.  The  Germ. — This  most  interesting  body  differs  remarkably  in 
composition  from  the  other  parts  of  the  grain.  The  percentage  of  con- 
tained water  is  somewhat  low,  but  the  soluble  extract  is  remarkably  high, 
amounting  to  just  one  third  of  the  whole  of  the  body  as  removed  in  the 
modern  processes  of  roller  milling.  Of  the  soluble  extract,  15*51  per  cent, 
consists  of  proteins.  There  is  no  gluten  recoverable.  The  ash  and  phos- 
phoric acid  are  high  ; the  fat  also  is  much  higher  than  in  any  other  part 
of  the  grain,'amounting  to  from  12  to  15’6  per  cent.  The  cellulose  is  moder- 
ately liigh. 

Detailed  analyses  of  germ  have  been  made  from  time  to  time  ; there 
follow  results  of  such  analyses  made  respectively  by  Richardson,  Teller, 
and  one  of  the  authors  : — 


Analysis 

Richardson. 

OF  Germ. 

Teller. 

Jago. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Water  . . . . . , — 

8*75 

6*80 

. . 13*23 

Ash — 

5*45 

4*65 

4*94 

Oil — 

15*61 

14*38 

. . 12*03 

Soluble  in  80  per  cent,  alcohol  26*45 

— 

— 

— 

Insoluble  in  water  . . — 

1*98 

— 

. . Dextrin  124 

Soluble  in  water  25*47 

— 

— 

. . Maltose,  5*54 

Sugar  or  Dextrin  . . — 

18*85 

— 

— 

Non-reducing  substance  — 

2*94 

— 

— 

Proteins  . . . . — 

3*65 

— 

— 

Soluble  in  water  . . 4*44 

— 

— 

— 

Dextrin  . . . . . . — 

1*44 

— 

— 

Proteins  . . . . . . — 

3*00 

— 

— 

Starch,  etc.,  undetermined  — 

9*95 

1*60 

33*78 

Cellulose  . . . . , . — 

1*75 

. , Proteins  39’ 62 

Sol.  proteins  15*51 

Insoluble  Proteins  . . — 

26*60 

Carbo-hydrates  32*95 

Insol.  proteins  13*73 

100*00 

100*00 

100*00 

Osborne  and  Campbell  find  that  germ  contains  a nucleic  acid  in  con- 
siderable quantity,  and  having  the  following  composition 


Carbon  . . 
Hydrogen 
Nitrogen 
Pliosphorus 
Oxygen  . . 


36*48 

4*48 

16*17 

8*96 

33*91 


100-00 

Tliere  are  also  present  the  following  proteins — leucosin,  a globulin, 
(contains  only  two  kinds  of  the  sulphur  of  edestin)  and  a proteose.  {Jour. 
Amer.  Chem.  Soc.,  1900,  379.) 

As  one  of  the  objects  of  modern  milling  is  to  thoroughly  remove  tlie 


COMPOSITION  OF  FLOUR  AND^.MILLING  PRODUCTS.  351 

germ  from  flour,  the  actual  effect  produced  by  germ,  when  present,  is  a 
subject  of  great  importance.  An  account  of  some  experiments  on  mixtures 
of  germ  and  flour  is  given  later  in  this  chapter. 

489.  Analyses  of  Products  of  Roller  Milling,  Richardson. — Clifford 
Richardson,  Chemist  to  the  Department  of  Agriculture  of  the  United  States 
Government,  has  made  a most  important  and  exhaustive  series  of  analyses 
of  products  of  roller  milling.  Richardson  selected  samples  from  three 
mills  ; the  first  being  from  Messrs.  Pillsbury’s  mill  at  Minneapolis,  where 
a straight  run  of  spring  American  wheat  is  used  ; the  second,  Messrs.  Herr 
and  Cissehs  mill,  who  employ  soft  winter  wheat  ; and  the  third  from  the 
mill  of  Messrs.  Warder  and  Barnett,  of  Ohio,  who  use  all  red  winter  wheat. 
These  analyses,  the  results  of  which  are  tabulated  on  pages  354,  355,  356,  357, 
are  of  such  great  value  as  to  warrant  their  quotation,  together  with  the 
remarks  thereon,  in  full.  So  far  as  the  authors  are  aware,  these  are  still 
the  most  exhaustive  authentic  series  of  analyses  of  wheat  products  which 
have  been  made. 

490.  “ Interpretation  of  the  Analyses. — The  wheat  as  it  enters  the  mill 
is  subjected  to  a series  of  operations  which  removes  dirt,  foreign  seed,  the 
fuzz  (beard)  at  end  of  the  berry,  and  a certain  portion  of  the  outer  coats, 
through  the  agency  of  a run  of  stones  and  brushes.  The  result  of  this 
operation  is  to  lower  the  amount  of  inorganic  matter  or  ash,  and  to  increase 
or  decrease  the  other  constituents  but  slightly,  the  proteins  being  a few 
tenths  of  a per  cent,  greater  in  amount.  The  point  from  which  a con- 
venient start  may  be  made  is  at  the  first  break. 

“ The  chop  from  the  first  rolls  is  very  marked  in  its  difference  in  com- 
jDosition  from  the  original  wheat.  It,  of  course,  has  less  fibre  (cellulose), 
and  also  it  is  seen,  less  ash,  oil,  and  proteins  ; in  fact,  it  is  starchy.  It 
contains  more  water,  owing  to  the  fact  that  its  comminution  has  allowed 
it  to  absorb  the  moisture  from  the  air,  and  in  general  it  will  be  observed  that 
the  coarser  or  more  fibrous  a specimen  is,  the  less  water  it  contains, 
while  the  finer  material  holds  more.  For  example,  the  percentage  of  water 


in  several  portions  of  grain  are  as  follows  : — 

Per  cent. 

Original  grain  . . . . . . . . . . , . . . 9*66 

Ready  for  the  break  . . . . . . . . . . 8*23 

Chop  from  first  break.  . . . . . , . . . . . 12*52 

Fifth  break  . . . . . . . , . . . . . . 7*62 

Bran  10*91 


“ The  heat  caused  by  the  friction  of  the  process,  of  course,  is  an  active 
agent  ; as  may  be  seen  on  comparing  the  original  grain  and  that  ready 
for  the  break.  The  question  of  the  relation  of  the  various  products  to 
humidity  is,  however,  considered  in  greater  detail  in  another  portion  of 
these  remarks. 

The  “ starchy  chop  from  the  first  break  is  carried  off  to  the  various  puri- 
fying and  grading  machines,  but  for  the  present  it  will  be  left,  as  it  is  desirable 
to  follow  the  breaks  to  the  end. 

“ The  tailings  from  the  first  scalper,  consisting  of  the  wheat  grain  split 
open  along  the  crease,  which  serve  to  feed  the  second  break  after  the  cleaning 
which  they  undergo,  vary  but  little  from  the  wheat  which  goes  to  the  first 
break.  There  are  slight  differences  which  must  be  attributed  to  the  diffi- 
culty of  selecting  and  preparing  for  analyses  samples  of  the  product  of 
the  different  breaks,  the  finer  chop  having  a tendency  to  sift  out  from  the 
lighter  bran  ; but  they  are  not  great  enough  to  vitiate  the  conclusions. 
In  the  first  break  so  little  is  done,  except -to  crack  open  the  wheat  and  clean 
it  for  the  following  rolls,  that  only  a small  change  should  be  expected. 


352 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

“ Tlie  chop  from  the  second  break  is  more  from  the  centre  of  the  wheat 
gram.  It  contains  less  ash,  fat,  and  proteins  than  any  of  the  break  pro- 
ducts, and  includes  as  was  shown  by  our  preliminary  investigation,  the 
greater  portion  of  the  endosperm. 

“ The  tailings  supplying  the  third  break  already  show,  owing  to  the 
greater  amount  of  chop  produced  on  the  second  break,  a marked  increase 
in  those  constituents  which  are  peculiar  to  the  outer  portions  of  the  grain 
mat  IS  to  say,  there  has  been  a marked  increase  in  ash,  fibre  and  proteins! 
I his  increase  becomes  still  more  apparent  from  break  to  break,  until  the 
bran  alone  is  left,  which  contains  more  ash  and  fibre  than  any  other  pro- 
duct of  the  wheat.  The  several  chops  increase  in  a like  manner,  the  last 
or  sixth  break  chop  holding  more  proteins  than  the  bran,  and  even  anv 
^ resulting  material.  This  is  probably  due  to  the  comminution 
ot  the  bran  m the  last  break,  and  consequently,  as  will  be  seen,  the  middlings 
from  this  chop  are  richer  in  nitrogen  than  any  other,  although  not  the 
richest  m gluten,  ovdng  to  the  proportion  of  bran  and  germ  which  thev 
contain. 

f followed  the  grain  through  the  breaks  to  the  bran,  the  products 

01  the  purification  of  the  chop  remain  to  be  studied. 

®l^orts  or  branny  particles  removed  from  the  chop,  or  from  the 
middmgs,  by  aspirators,  contain  'much  less  fibre  and  ash  than  the  bran 
although  they  are  of  similar  origin,  that  is  to  say,  from  the  outer  coats 
ot  the  gram.  The  analyses  point  to  their  origin  from  those  portions  of 
the  coat  which  contain  less  ash  and  fibre. 

The  middlings  are  graded  into  five  classes,  and  in  their  original 
cleaned  state  they  differ  chemically  in  the  fact  that  from  No.  1 to  No.  5 
there  IS  a regular  decrease  in  ash,  fibre,  and  fat,  while  No.  5 is  richer  in 
proteins  than  any  other.  This  would  be  expected  from  our  preliminary 
examination,  which  showed  a decrease  in  bran  from  beginning  to  end, 
and  that  No.  5 was  the  purest  endosperm. 

After  cleaning,  the  same  relations  hold  good,  but  owing  to  the  removal 
of  the  branny  particles  there  is  in  all  cases  a loss  of  ash  constituents  and  fibre. 
Ihe  effect  of  cleaning  is  more  apparent  in"  Nos.  1 and  2 where  more  bran 
IS  removed. 

The  reduction  of  the  middlings  on  smooth  rolls  changes  the  com- 
pdsition  but  slightly,  and  the  flours  which  originate  from  this  process  are 
very  similar  to  the  middlings  from  which  they  were  produced.  That  from 
the  fourth  reduction  is  richer  in  nitrogen,  as  would  also  be  the  case  with 
the  fifth,  although  want  of  a specimen  prevented  analysis. 

‘ Tlie  tailings  from  the  middlings  purifiers  present  the  usual  char- 
acteristics of  bye  products,  which  owe  their  existence  to  the  outer  part  of 
the  grain,  with  its  high  percentages  of  ash  and  fibre,  and,  in  this  case,  also 
ot  nitrogen.  It  is  remarkable,  however,  that  the  tailings  marked  No.  6 
contain  only  one-third  as  much  ash  as  the  others  ; but  this  is  explained 
by  the  fact  that  they  are  largely  composed  of  endosperm. 

‘ Tlie  tailings  from  the  different  reductions  are  nearly  alike  in  com- 
position, with  two  exceptions.  Those  from  the  fourth  contain  little  of 
ash,  fibre,  and  nitrogen.  Like  No.  6 of  the  purifier  tailings  they  consist 
largely  of  endosperm.  Those  from  the  second  reduction  contain  much 
germ,  and  are,  therefore,  richer  in  nitrogen  than  the  rest. 

Tlie  repurified  middlings,  as  might  be  expected,  contain  much  more 
ash,  oil,  and  fibre,  than  the  original,  and  there  is  also  an  increase  in  nitrogen 
but^  not  in  gluten,  owing  to  the  large  amount  of  bran  they  contain. 

Analyses  of  three  grades  of  flour  as  furnished  to  the  market  follow. 
Irom  a cursory  glance  it  might  be  said  that  the  low-grade  flour  was  the 
best,  as  it  contains  the  most  proteins,  but  its  weakness  is  discovered  in 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  353 


the  fact  that  it  has  only  4 per  cent,  of  gluten.  The  bakers’  flour  contains 
more  ash,  oil,  fibre,  proteins,  and  gluten,  than  the  patent  ; but  owing  to 
the  increased  amount  of  the  first  three  constituents  mentioned,  it  is  pro- 
portionately lacking  in  whiteness  and  lightness.  The  two  flours  each 
have  their  advantageous  points. 

“ Several  other  grades  of  flour,  break  flour,  stone  flour,  and  flours  from 
the  first,  second,  and  third  tailings,  are  all  very  similar,  and  as  far  as  chemical 
analyse?  is  concerned,  good.  The  preliminary  examination  has,  however, 
shovTi  certain  defects  in  each.  The  break  flour  is  richer  in  proteins  and 
gluten  than  any  other,  and  if  it  were  pure  and  its  physical  condition  were 
good,  it  would  be  of  value. 

“ The  roller  process  is  distinguished  for  the  completeness  with  which 
it  removes  the  germ  of  the  grain  during  the  manufacture  of  flour  by  flattening 
and  sifting  it  out.  This  furnishes  the  three  bye-products  which  are  known 
as  first,  second,  and  third  germ.  They  consist  of  the  germ  of  the  wheat, 
mixed  with  varying  proportions  of  branny  and  starchy  matter,  the  second 
being  the  purest.  They  all  contain  much  ash,  oil,  and  nitrogen  ; and  if 
allowed  to  be  ground  with  the  flour,  blacken  it  by  the  presence  of  the  oil, 
and  render  it  very  liable  to  fermentation,  owing  to  the  peculiar  nitrogenous 
bodies  which  it  carries. 

“ The  flour  from  the  bran  dusters  is  much  like  that  from  the  tailings, 
and  like  the  stone  stock,  from  a chemical  point  of  view.  This  merely 
shows  that  chemical  evidence  should  not  alone  be  taken  into  considera- 
tion, for  the  bran-duster  flour  is  a dirty,  lumpy  bye-product,  while  the 
stone  stocks  are  valuable  middlings.  Analyses  of  various  tailings  are 
next  in  the  series,  and  need  no  comment.  Those  of  the  dust  from  middlings 
and  dust-catchers  are  rather  surprising,  in  that  they  both  contain  much 
gluten,  and  the  first  one  much  fibre  ; but  this  is  due  to  their  containing 
both  bran  and  endosperm. 

“ To  follow  the  gluten  through  the  process  it  is  necessary  to  go  back 
to  the  breaks.  The  amount  in  the  various  chops  does  not  vary  greatly. 
There  is  an  apparent  anomaly,  however,  in  the  fifth  and  sixth  breaks,  where 
no  gluten  was  found  in  the  feed,  but  much  in  the  chop.  This  is  owing 
to  the  fact  that  the  feed  has  become  at  this  point  in  the  process  so  branny 
that  by  the  usual  method  of  washing  to  obtain  the  gluten  it  does  not  allow 
of  its  uniting  in  a coherent  mass,  and  separating  from  the  bran. 

“ Among  the  middlings,  both  uncleaned  and  clean,  the  fourth  is  the 
richest  in  gluten,  and  the  result  of  the  process  of  cleaning  is  to  increase 
the  amount,  although  slightly  diminishing  the  nitrogen,  which  is  due  to 
the  removal  of  the  branny  matter,  which,  though  rich  in  nitrogen,  is  poor 
in  gluten. 

“ In  the  products  of  the  reduction  on  smooth  rolls,  the  chops  from  the 
higher  middlings  are  the  richest,  and  if  the  analyses  of  the  flours  were 
complete.  No.  4 would  probably  contain  more  than  the  lower  numbers. 

“ The  tailings  are,  as  has  been  already  said,  remarkable,  not  so  much 
that  No.  1 has  no  gluten,  but  that  Nos.  2,  3,  4,  have  7*62  per  cent.,  and 
No.  6 as  much  as  14*37  per  cent.  The  regular  increase  shows  that  the 
highest  number  must  contain  a large  portion  of  endosperm. 

“ That  this  is  the  case  the  microscopic  examination  of  the  different 
tailings  has  shown.  No.  I is  found  to  consist  almost  entirely  of  the  outer 
coating  of  the  grain;  Nos.  2,  3,  and  4,  of  the  same,  mixed  with  a large 
proportion  of  endosperm,  which  is  attached  thereto,  while  in  No.  6 it  is 
difficult  to  discover  any  large  amount  of  anything  but  flouring  material, 
and  the  small  percentage  of  ash  shows  also  that  it  can  not  contain  much  bran. 

“ In  a like  manner  No.  4 tailings  from  the  reductions  has  13*34  per 
cent,  of  gluten,  which  is  owing  to  the  large  proportion  of  endosperm  which 


Analyses  of  the  Products  of  Roller  Milling,  by  Richardson. 


354 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Analyses  of  the  Peodtjcts  op  Roller  Milling,  by  B^icrktudsot^— Continued. 


COMPOSITION  OP  FLOUR  AND  MILLING  PRODUCTS.  355 


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Analyses  of  the  Products  of  Roller  Milling,  by  Richardson — Continued. 


356 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Analyses  of  the  Products  of  Roller  Milling,  by  Richardson — Continued. 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  357 


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358 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


it'^cohtains,  and  in  this  case,  too,  the  fact  of  the  presence  of  so  much  of 
the  interior  of  the  berry  is  presaged  by  the  low  percentage  of  ash.  The 
remaining  tailings  of  this  class  have  little  or  no  gluten,  with  the  exception 
of  No.  1,  as  they  contain  very  little  endosperm. 

“ In  connection  with  the  remaining  specimens,  the  gluten  has  been 
already  mentioned,  and  the  results  as  a whole  warrant  the  conclusion 
that  less  of  it  is  wasted  in  the  bye-products  than  would  be  imagined.  For  a 
complete  discussion  of  this  point,  data,  which  are  not  at  hand  in  regard  to 
the  per  cent,  of  each  material  produced,  are  necessary. 

“ The  products  from  Virginia  wheat,  similar  to  those  which  have  just 
been  described,  present  the  same  but  not  as  wide  variations  in  the  breaks 
and  in  the  flours  ; the  low  grade,  instead  of  containing  less  gluten,  has 
more  than  the  bakers’  or  patent.  This  may  be  due  to  the  greater  softness 
of  the  wheat  in  consequence  of  which  it  is  less  suited  to  the  process,  a fact 
which  is  confirmed  to  a certain  degree  by  the  specimens  of  flour  from  Ohio 
wheat,  among  which  the  low  grade,  although  not  exceeding  the  other  brands 
in  the  amount  of  gluten,  approaches  very  nearly  to  them,  and  it  is  there- 
fore only  reasonable  to  conclude  that  the  spring  wheats  are  particularly 
suited  for  roller  milling. 

“ One  of  the  characteristic  features  of  the  roller  milling  process,  as 
has  been  mentioned,  is  the  removal  of  the  germ  of  the  grain,  thus  pre- 
venting its  injuring  the  quality  of  the  flour.  Among  the  bye-products 
of  the  Pillsbury  mill  are  included  three  separations  of  germs,  known  as 
first,  second,  and  third.  They  are  all  rich  in  oil  and  proteins,  which  to- 
gether form  one  half  of  the  substance.  The  second  germ  seems  to  be  freer 
from  contamination,  and  was  selected  for  a more  detailed  examination 
[of  which  the  results  are  given,  together  with  those  of  other  analyses,  in  a 
preceding  paragraph]. 

“ It  has  been  found  that  the  water  extract,  if  left  in  contact  with  the 
residue  of  the  germ,  would  soon  be  the  cause  of  a pecuhar  fermentation. 
This  shows  the  bad  effect  the  presence  of  this  soluble  protein  would  have 
in  flour,  causing  a fermentation  or  putrefaction  which  would  injure  and 
discolour  it.  The  oil  in  the  germ  is  also  an  additional  source  of  trouble, 
in  that  it  is  readily  oxidized  under  certain  circumstances  and  tends  to 
blacken  the  flour.” 

491.  Further  Examination  of  Flours  Produced  during  Gradual  Reductions. 

— The  great  importance  which  attaches  to  these  led  the  authors  to  make 
a further  series  of  examinations  of  the  flours  produced  at  the  various  breaks 
and  during  the  reductions  of  the  middlings,  together  with  the  finished  flours, 
straight  grade,  bakers’,  and  patent.  For  the  series  of  samples  in  illustra- 
tion of  this  point,  the  authors  have  to  thank  an  important  firm  of  Liver- 
pool millers,  whose  mill  is  arranged  on  Simon’s  system.  As  being  of  more 
immediate  importance  to  the  miller  and  baker,  the  tests  have  been  confined 
to  estimations  of  moisture,  gluten,  water-absorbing  power,  and  colour. 
The  wheat  mixture  consisted  of — 

2 Parts  Australian. 

2 ,,  Californian. 

1 ,,  White  Kurrachee. 

2 ,,  Canadian  White. 

2 ,,  Chicago  Spring. 

2 ,,  Saxonska. 

1 ,,  Hard  Duluth. 

1 ,,  Polish  Red. 

4 ,,  Oregon. 

1 ,,  English. 


18 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  359 


In  addition  to  these,  samples  of  flour  from  American  Spring  and  Winter 
Wheats  respectively  are  also  included. 


Flours  Yielded  by  Gradual  Reduction. 


Xo. 

De-criptiox. 

Mois- 

Crude  Gluten. 

Colour. 

Water- Absorb- 
ing Power. 

ture. 

Wet. 

Dry. 

j Ratio. 

Quarts 

per 

Sack. 

Lbs.  per- 
100  lbs. 
Flour. 

Wheat 

! 13*50 

25*0 

9*15 

2*7 

1 

I.Break  Flour 

13*18 

21*0 

8*57 

2*4 

20.  G 

60 

53*58 

2 

( II- ) 

; III.  r Breaks  Flour 

13*40 

27*0 

9*80 

‘ 2*7 

2.G 

61 

54*47 

3 

liv.  j 

V.  Break  Flour 

12*80 

43*0 

14*6 

1 

i 2*9 

16G.Y. 

77 

68*76 

4 

1 I.  Reduction 

13*24 

22*0 

7*7 

2*8 

3 G. 

60 

53*58 

5 

j II.  Reduction 

12*45 

25*0 

9*2 

2*6 

7 Y. 

71 

63*40 

6 

[ 1 ly  ■ 1 Reduction 

13*52 

26*0 

9*3 

2*7 

2 Y. 

66 

58*94 

7 

1 1 y 1 Reduction 

13*04 

29*0 

10*1 

2*8 

10  Y. 

70 

62*51 

8 

VI.  Reduction 

13*40 

27*0 

9*5 

2*8 

9 Y. 

71 

63*40 

9 

VII.  Reduction 

12*30 

32*0 

10*5 

3*0 

12  Y. 

75 

66*97 

10 

Straight  Grade  Flour 

12*94 

25*0 

9*5 

2*6 

6G. 

67 

59*83 

11 

Patent  Flour 

12*94 

22*0 

8*1 

2.7 

5 Y. 

65*5 

58*49 

12 

Bakers’  Flour 

13*30 

26*0 

9*7 

2*6 

6G.y. 

67 

59*83 

13 

III.  Flour 

12*94 

32*0 

12*1 

2*6 

20  G. 

81*5 

72*78 

14 

Spring  American: 
Weakest  Break  Flour 

13*50 

34*0 

j 

12*0 

2*8 

8G. 

71*0 

63*40 

15 

Strongest  Break  Flour 

13*40 

40*0 

13*9 

2*8 

16G.Y. 

72*0 

64*29 

16 

Strong  Flour  from  last  Re- 
duction of  Middlings 

11*61 

33*0 

11*3 

2*9 

18G.Y. 

98*0 

87*51 

17 

Winter  American  : 
Weakest  Break  Flour 

12*75 

15*0 

i 

5*3 

2*8 

1*5  G. 

64*0 

57*15 

18 

Strongest  Break  Wheat  . . 

12*51 

30*0 

10*4 

2*8 

10*0  Y. 

67*5 

60*27 

19 

Strong  Flour  from  last  Re- 
duction of  Middlings 

11-30 

29-0 

10:2 

2-8 

15-0  Y. 

91-0 

81-26 

On  examining  the  results  of  these  analyses,  it  will  be  seen  that  No.  1, 
the  first  break  flour,  is  low  in  water-absorbing  power  ; 60  quarts:,  contains 
about  the  average  gluten  of  the  series,  and  is  low  in  colour.  No  2 consists 
of  the  flour  from  the  second,  third,  and  fourth  breaks  ; this  shows  but  little 
improvement  in  water-absorbing  power,  rather  more  in  gluten,  but  a decided 
improvement  in  colour.  No.  3,  the  fifth  break  flour,  absorbs  much  more 
water,  while  the  gluten  is  the  highest  of  the  series  : this  is  accompanied 
by  a considerable  falling  off  in  colour.  There  are  next  the  flours  produced 
by  the'  reduction  of  the  semolinas  ; that  of  the  first  reduction  is  low  in 
water-absorbing  power  and  gluten,  but  of  good  colour.  The  second  reduc- 
tion produces  a flour  of  improved  water-absorbing  powder  and  gluten,  with 
but  little  variation  in  colour.  The  joint  product  of  the  third,  and  part  of 
the  fourth  reduction,  yields  a flour  which  shows  a falling  off  in  water-absorb- 
ing power,  with  a slight  increase  in  gluten.  The  remainder  of  the  flour  from 
the  fourth  reduction,  together  with  that  of  the  fifth,  shows  an  increase  in 
both  water-absorbing  powder  and  gluten,  while  the  colour  somewhat  falls 
off.  The  sixth  reduction  flour  absorbs  rather  more  water,  while  the  gluten 
is  once  more  rather  less  in  quantity.  The  flour  from  the  seventh  reduction, 
No.  9,  shows  an  increase  in  both  water-absorbing  power  and  gluten,  while 


360 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  colour  becomes  slightly  darker.  Following  these  is  the  straight  grade 
flour,  No.  10  ; comparing  this  with  the  patent,  No.  11,  and  bakers’  flour, 
No.  12,  the  straight  grade  runs  intermediate  between  the  other  two  in  water- 
absorbing powder,  gluten,  and  colour.  No.  13,  termed  “ thirds  flour,”  is 
obtained  by  again  rolling  the  tailings  from  the  last  reduction  of  middlings  ; 
this  flour,  it  will  be  noticed,  is  highest  in  water-absorbing  power,  and  next 
to  the  highest  in  gluten,  while  the  colour  is  very  Ioav. 

Turning  next  to  the  series  of  flours  obtained  from  American  winter 
wheats,  the  gluten  in  the  weakest  break  flour  is  only  5*3  per  cent.,  while 
the  colour  is  very  good,  and  the  Avater-absorbing  poAA  er  low.  The  strongest 
break  flour  shows  a slight  increase  in  water-absorbing  power,  and  a con- 
siderable increase  in  gluten  : as  might  be  expected  the  colour  is  slightly 
loAver.  Taking  next  the  flour  from  the  last  reduction  of  middlings,  the 
Avater-absorbing  poAver  in  this  reaches  the  remarkably  high  figure  of  91 
quarts  per  sack  ; the  gluten,  hoAvever,  is  absolutely  less  than  that  in  the 
preceding  ; the  colour  has  slightly  fallen  off.  In  these  three  flours  the 
moisture  diminishes  slightly  AA'ith  the  increase  in  quantity  of  water  absorbed. 
SomeAvhat  similar  lessons  may  be  learned  from  the  series  of  flours  from 
American  spring  wheats.  Again,  the  Aveakest  break  flour  absorbs 
comparatively  little  water,  71  quarts,  AA’hile  the  gluten  amounts  to  12*0 
per  cent.  ; the  colour  is  high.  The  strongest  break  flour  shoAAS  an  increase 
in  gluten,  and  a very  slight  increase  in  aa  ater  absorbed  ; the  colour  has 
fallen  off.  The  flour  from  the  last  reduction  of  middlings  registers  the 
enormous  Avater-absorbing  poAver  of  98  quarts  per  sack.  A dough  test, 
AA'ith  88  quarts  per  sack,  Avas  mixed  Avith  the  greatest  difficulty,  and  took 
257  seconds  to  run  through  the  viscometer  ; the  98  quarts  test  ran  through 
in  64  seconds.  The  gluten  of  this  flour  was  only  11*3  per  cent.,  being  less 
than  in  the  Aveakest  break  flour  ; the  colour  again  descends.  In  this  series, 
as  in  those  from  AA'inter  AA'heats,  the  moisture  diminishes  Avith  the  increase 
of  strength. 

492.  Damping  Wheats. — It  is  the  custom  of  millers  to  add  to  some  of 
the  harder  and  more  flinty  AA'heats,  particularly  those  of  India,  more  or 
less  Avater  as  a preliminary  to  milling.  The  addition  of  such  water  is  gener- 
ally supposed  to  have  tAA'o  effects,  the  first  being  a softening  of  the  bran, 
and  the  second  an  increased  yield  of  flour.  The  softening  of  the  bran 
renders  it  less  brittle,  and  so  less  gets  broken  up,  and  thus  into  the  flour. 

It  is  essentially  a question  for  the  miller,  rather  than  the  chemist, 
to  decide  Avhether  the  damping  of  Indian  AALeats  renders  them  more 
AA'orkable  and  amenable  to  milling  processes  generally.  It  is  quite 
conceivable  that  a “ melloAv  ” AA'heat  is  more  easily  converted  into  flour 
than  one  AALich  is  hard  and  brittle  ; but,  against  any  consideration  of  ease 
in  milling  must  be  set  the  effect,  if  any,  of  damping  on  the  after  quality  of 
the  flour  produced. 

In  connection  AA'ith  this  subject  the  authors  have  analysed  a number 
of  samples  of  Indian  and  other  hard  AA'heats,  dry  and  damped,  and  also  the 
flours  produced  therefrom.  The  folloAAung  are  the  general  conclusions 
derived  from  an  extended  and  exhaustive  series  of  experiments  : — 

In  artificially  damping  wheats,  but  a small  proportion  of  the  water  finds  its  way 
into  the  flour.  The  actual  amount  varied  from  3*8  to  17*1  per  cent,  of  the  total 
quantity  added.  This  depends  on  the  length  of  time  allowed  to  elapse  before  grind- 
ing. The  water  penetrates  evenly  through  hard  Indian  wheats  in  about  forty-eight 
hours. 

The  addition  of  water  to  wheats  already  containing  an  average  quantity  of  water 
(in  experiment  cited,  13-2  per  cent.)  is  decidedly  deleterious  ; strength  and  colour 
are  both  injuriously  affected.  But  this  will  depend  somewhat  on  the  nature  of  the 


COMPOSITION  OF  FLOUR  AND  .MILLING  PRODUCTS.  361 


wheats.  Thus  some  Indians  may  be  damped  to  contain  15  per  cent,  of  moisture, 
while  Russian  wheats  should  be  restricted  to  a limit  of  13  per  cent. 

With  wheats  in  a dry  state  (11-0  to  11*5  per  cent,  of  water)  damping  in  a slight 
degree  does  not  seriously  affect  the  colour  or  strength  of  the  flour. 

On  making  baking  tests  with  the  flours  from  such  slightly  damped  wheats  com- 
pared with  those  of  the  wheats  milled  dry  ; the  damped  wheat  flours  fall  off  less 
during  fermentation,  yield  bread  of  better  colour  and  flavour,  and  in  practically 
the  same  quantity. 

The  slight  damping  of  the  very  dry  wheats  enables  the  miller  to  produce  a better 
quality  of  flour. 

493.  Washing  Wheats. — In  view  of  the  growing  importance  attached 
by  millers  to  rigidly  clean  flours,  and  the  consequent  necessity  for  the  re- 
moval of  the  dirt  and  other  impurities  often  associated  with  wheat ; the  grain, 
and  especially  the  more  dirty  varieties,  is  now  thoroughly  washed  before 
being  milled.  Although  Indian  and  the  more  flinty  types  of  wheat  bear 
a prolonged  submergence  in  water,  the  softer  kinds  of  grain  are  injured 
by  any  but  the  shortest  washing  process.  The  modern  washing  machines 
are  therefore  not  intended  to  soak  wheat,  but  to  wash  it  clean  from  extrane- 
ous dirt  as  rapidly  as  possible.  The  grain  is  then  dried  by  treatment  in 
a centrifugal  machine,  or  “ whizzer.’^  This  operation  not  only  frees  the 
wheat  from  ordinary  dirt,  but  also  largely  removes  bacteriological  impurities 
which  may  be  of  an  objectionable  nature. 

The  question  frequently  arises,  what  kind  of  water  is  fit  for  wheat  wash- 
ing purposes  ? The  quantity  used  is  large,  amounting  sometimes  to  as 
much  as  20  gallons  per  bushel  of  grain  washed  per  hour.  Thus  to  wash 
100  bushels  of  wheat  hourly,  in  extreme  cases,  2,000  gallons  of  water  per 
hour  may  be  required.  The  purchase  of  water  of  drinking  quality  for  this 
purpose  is  very  expensive,  and  may  even  in  some  places  be  prohibitive. 
Millers^are  consequently  compelled  to  seek  some  other  source  of  washing 
water  if  possible.  Among  these,  sea-water,  if  free  from  contamination,  is 
employed,  or  river  water  is  frequently  used.  The  latter  may  of  course  be 
of  almost  any  degree  of  purity.  There  is  little  doubt  that  the  standard 
of  purity  for  this  purpose  need  not  necessarily  be  so  high  as  that  required 
in  water  for  drinking  purposes.  But  taking  a filtered  river  water  which 
yields  on  analysis — 

Nitrogen  as  Free  Ammonia  . . . . . . 14  parts  per  100,000 

Nitrogen  as  Albuminoid  Ammonia  . . . . 5 ,,  ,,  ,, 

may  it  be  used  or  not  for  wheat  washing  ? 

It  need  scarcely  be  pointed  out  that  these  data  entirely  condemn  the 
water  for  drinking  purposes.  But  in  rapid  washing  as  distinct  from  soaking, 
the  exposure  to  the  water  is  only  for  a very  short  period  of  time.  In  some 
experiments  made,  in  which  wheat  was  subjected  to  more  prolonged  treat- 
ment with  water  than  occurs  in  the  mill,  it  was  found  that  the  resultant 
flour  had  its  moisture  raised  from  13*2  to  13*7  per  cent.,  being  an  absorption 
of  0*5  per  cent,  of  the  weight  of  the  flour.  In  washing,  therefore,  but  very 
little  water  is  absorbed  by  the  grain,  and  of  that  little  by  far  the  greater 
part  does  not  penetrate  beyond  the  bran  and  into  the  flour.  Corroboration 
of  this  is  afforded  by  washing  with  sea-water  ; the  flour  is  not  perceptibly 
rendered  salt,  and  the  br  an  is  eaten  and  keenly  relished  by  animals.  In 
event  of  the  washing  water  containing  bacteria,  there  may  be  some  appre- 
hension of  these  finding  their  way  into  the  flour.  But  although  they  may 
possibly  find  a lodgment  on  the  outer  skin  of  the  bran,  in  practice  there  is 
no  contamination  of  any  of  the  flour,  except  possibly  the  very  last  reduc- 
tions from  the  bran.  Unwashed  wheats  will  usually  contain  more  bacteria 
than  any  water  used  for  washing,  and  consequently  are  rendered  bacterio- 


362 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


logically  cleaner  by  washing  with  any  ordinary  water.  Further,  washing 
with  an  abundance  of  a slightly  impure  water  will  produce  a cleaner  wheat 
than  is  obtained  by  the  use  of  a purer  water  in  stinted  quantity.  Natur- 
ally the  washing  water  should  be  as  clean  as  practicable,  and  of  a good 
quality  ; but  it  is  not  necessary  that  it  be  judged  by  the  same  standard 
of  purity  as  is  required  of  a drinking  water.  Where  the  washing  water  is 
of  the  ordinary  river  type,  a good  plan  is  to  use  an  abundance  of  this  to 
remove  the  bulk  of  the  dirt  and  then  to  give  a final  rinsing  with  a small 
quantity  of  clean  water. 

494.  Artificial  Drying  of  Wheats  and  Flours. — By  means  of  a series  of 
experiments  on  flour,  Graham  very  clearly  showed  the  advantages  derived 
from  gently  kiln-drying  excessively  damp  wheats.  An  inferior  flour  was 
taken,  and  one  portion  heated  for  some  six  hours  to  a temperature  of 
140°  F.  The  dried  and  undried  flours  were  then  shaken  up  with  water  in 
the  manner  previously  described  for  the  purpose  of  obtaining  the  soluble 
extract,  except  that  separate  portions  of  the  flour  and  water  were  allowed 
to  stand  for  four  and  eight  hours  respectively  before  filtration.  At  the  end 
of  four  hours  the  percentage  of  soluble  extract,  yielded  by  the  undried  flour, 
amounted  to  10*49  per  cent.,  while  the  dried  sample  gave  only  8*7.  The 
difference  between  the  two  at  the  end  of  eight  hours  was  still  greater  ; the 
undried  flour  gave  16*11  per  cent,  of  extract,  while  the  dried  sample  yielded 
only  10*64  per  cent.  Evidently,  then,  this  treatment,  by  partly  destroying 
the  diastatic  power  of  the  proteins  degraded  by  moisture,  prevents  exces- 
sive diastasis  of  the  starch,  on  the  flour  being  treated  with  water.  The 
soluble  proteins,  maltose,  and  dextrin  all  show  a decrease,  as  may  readily 
be  seen  on  consulting  the  following  table  : — 


Artificial  Drying 

OF  Flour  (Graham). 

Undried  Flour,  on  Standing.  1 

1 

Dried  Flour,  on  Standing. 

Maltose  . . 

Dextrin  . . 
i Soluble  Proteins 

4 hours. 
6-82 
0-43 
3-19 

8 hours. 

11-14 

1-23 

3-74 

4 hours. 

4-44 

1- 78 

2- 48 

8 hours. 

4-44 

2- 91 

3- 29 

Total  Soluble  Extract  . . 

10-44 

16-11 

8-70 

10-64 

As  a result  of  these  experiments,  Graham  recommended  the  kiln-drying 
of  damp  wheat,  suggesting  that  the  initial  temperature  might  be  100°  F., 
increasing  slowly  to  140°  F.,  at  the  same  time  submitting  it  to  a current  of 
air,  and  taking  care  that  the  thickness  on  the  kiln  floor  is  not  too  great. 
{Cantor  Lectures,  Jour.  Soc.  Arts,  pp.  116-7,  Jan.  9,  1880.)  Unfortunately, 
Graham  seems  not  to  have  'made  any  gluten  determinations  in  these  flours. 
The  temperature  he  recommends  (140°  F.  = 60°  C.),  is  identical  with  that 
at  which  flour,  on  being  heated  for  several  hours,  according  to  Weyl  and 
Bischoff,  appears  to  lose  the  faculty  of  forming  gluten.  {Jour.  Chem.  Soc., 
1882,  p.  537.)  The  authors  can  confirm  this  statement,  having  repeated 
their  experiment  with  the  same  results.  If  the  kiln-drying  should  destroy, 
or  even  materially  impair,  the  gluten-forming  powers  of  the  flour,  this  would 
tend  to  seriously  counterbalance  the  great  benefit  derived  from  the  retarda- 
tion of  diastasis  as  the  result  of  the  application  of  heat. 

The  following  are  the  results  of  a series  of  experiments  on  a sample  of 
seconds  flour  of  low  quality,  stone-milled  from  English  wheats.  Imme- 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  363 


diately  on  receiving  the  sample,  its  strength,  moisture,  and  colour  were 
estimated  in  the  usual  manner.  A strength  determination  was  also  made 
on  the  dough  after  standing  24  hours  (stability  test).  The  weather  was 
intensely  cold  at  the  time  of  making  these  experiments  ; the  doughs  were 
probably  very  little  above  the  freezing  point  during  the  time  they  were 
standing.  This  is  mentioned,  because  the  amount  of  falling  off  in  strength 
was  so  much  less  than  that  in  some  other  samples,  the  results  of  which  are 
recorded  in  the  paragraph  on  Stability  Tests  in  Chapter  XXVI,  and  which 
were  tested  during  a hot  July.  The  flour  was  next  placed  above  a heating 
furnace,  and  allowed  to  remain  there  for  some  days  ; the  temperature  was 
taken  from  time  to  time,  by  plunging  a thermometer  in  the  flour,  and  was 
found  to  range  between  27°  and  30°  C.  (80*6°-86°  F.).  After  two  days’ 
drying  a fresh  series  of  determinations  were  made  in  the  flour,  and  again 
after  sixteen  days.  The  results  of  the  various  tests  are  given  in  the  follow- 
ing table  : — 

Artificial  Drying  of  Flour. 


Descriptio>'. 

Mois- 

ture, 

Crude  Gluten. 

Colour. 

! 

W ater-Absorbing  Power. 

Wet. 

i 

Dry.  1 

Ratio. 

1 

1 

i 

Quarts 

per 

Sack. 

Lbs. 

per 

100 

lbs. 

Flour. 

Same  after 

24  hours. 

'Quarts 

per 

Sack. 

Lbs. 
per  100 
lbs. 
Flour. 

Undried  Flour  . , 

1.3-4 

29-0 

10-3 

2-8 

12-0  G. 

67-0 

59-8 

65-0 

58-0 

Flour  after  2 days  drying 

10-3 

31-0 

10-7 

2-9 

12-0  G. 

74-5 

66-5 

— 

— 

Flour  after  16  days  drying 

6-5 

32-0 

11-6 

2-8 

12-0  G. 

86-0 

76-7 

82-0 

73-2 

As  might  be  expected,  the  natural  result  of  drying  is  to  lessen  the  mois- 
ture ; this  falls  in  two  days  from  134  to  10*3  per  cent.  ; simultaneously 
the  water-absorbing  power  rises  7*5  quarts.  A diminution  of  moisture  of 
2*1  per  cent,  corresponds  to  an  evaporation  of  2*3  quarts  per  sack  ; but 
the  flour  shows,  as  the  result  of  actual  trial,  that  its  water-absorbing  power 
had  increased  to  a far  greater  extent.  During  the  sixteen  days  the  furnace 
was  not  kept  continually  alight,  so  that  proportionately  the  moisture  has 
not  so  much  diminished  as  during  the  first  two 'days.  With  a total  diminu- 
tion of  moisture  of  from  134  to  6*5  per  cent.,  which  equals  6*9,  the  water- 
absorbing power  had  increased  by  19  quarts.  A diminution  in  moisture 
of  6*9  per  cent,  is  equivalent  to  loss  by  evaporation  of  7*6  quarts  per  sack, 
but,  as  before,  the  water-absorbing  power  of  the  flour  has  increased  by  a 
much  greater  quantity.  The  next  point  for  consideration  was  whether 
this  increase  in  power  of  absorbing  water  might  not  be  apparent  rather  than 
real  ; and  that  while  the  flour  would  require  more  water  to  first  convert 
it  into  dough,  it  would  fall  off  to  a correspondingly  greater  extent  during 
fermentation.  In  order  to  obtain  information  on  this  point  the  24  hours 
absorption  tests  were  made  ; they  show  that  the  original  flour  fell  off 
during  that  time  2 quarts,  while  the  dried  flour  lost  4 quarts  in  water- 
absorbing power.  Compared  with  the  undried  flour,  that  which  had  been 
dried  until  6*9  per  cent.,  or  7 *6  quarts  per  sack  of  water  had  been  evaporated, 
maintained,  after  being  24  hours  in  dough,  the  advantage  in  water-absorbing 
power  to  the  extent  of  17  quarts.  In  gluten  the  flours  show  a slight  increase 
as  the  result  of  being  dried.  The  three  samples  were  exactly  ahke  in  colour. 
These  experiments  confirm  the  baker’s  view  that,  as  a result  of  storing  flour, 
its  water-absorbing  power  materially  increases  -without  any  corre- 
sponding diminution  in  weight.  It  may  therefore  be  concluded  that  gentle 
artificial  drying  of  flour  increases  its  water-absorbing  capacity  to  a considerably 


364 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


greater  extent  than  that  of  the  water  lost  ly  evaporation.  In  all  prolahility,  similar 
drying  of  damp  wheats  would  have  a like  effect. 

495.  Tabulated  Results  of  Flour  Analyses. — The  following  tables  contain 
analyses  of  flour  selected  from  among  those  made  by  one  of  the  authors 
during  1885-6.  Flours  were  selected  which  are  of  interest  for  one  of  the 
following  reasons — 1st,  their  having  been  produced  from  single  wheats  ; 
2nd,  their  being  well-known  brands.  The  results  may  also  possess  some 
additional  value  as  placing  on  record  the  composition  of  flours  at  the  time 
of  transition  from  stone  to  roller  milling. 

Nos.  1-11  are  the  results  of  examination  of  a number  of  flours  used  in 
some  viscometer  experiments  described  in  Chapter  XXVI. 

The  wheats  in  Nos.  1-4  were  specially  ground  on  stones,  and  the  flour 
produced  dressed  through  No.  9 silks. 

The  upper  gluten  figures  in  No.  1 Avere  obtained  by  allowing  the  flour 
to  remain  in  dough  for  two  hours  before  washing  out  the  gluten. 

The  flours  2,  3,  4 and  28  are  marked  by  their  very  high  percentage 
of  gluten  ; notwithstanding  this,  their  absorptive  capacity  does  not  rank- 
so  high  as  that  of  other  flours  whose  percentage  of  gluten  is  less  ; they  are 
respectively  flours  from  Odessa,  Saxonska,  Australian  and  Taganrog  wheats. 
Nos.  8 and  9 are  high  in  gluten,  but  still  not  quite  so  high  as  the  group 
just  referred  to  ; their  water-absorbing  power  is,  however,  somewhat 
more.  Like  most  of  the  Hungarian  flours.  No.  10  is  high  in  water-absorb- 
ing capacity,  but  with  only  a medium  quantity  of  gluten.  The  English 
Avheat,  No.  11,  flour  has  a high  moisture  content,  with  low  gluten  and 
water-absorbing  capacity. 

On  page  366  are  given  the  results  of  analysis  of  a number  of  single  wheat 
flours.  Flours  Nos.  12-16  were  milled  purely  for  the  ordinary  purposes  of 
sale,  as  were  also  Nos.  19-27,  and  35-36.  The  others  were  specially  ground 
on  stones  as  experimental  tests  on  the  respective  wheats.  Nos.  19-22  were 
milled  in  Glasgow,  and  Nos.  23-27  in  Liverpool.  Nos.  28-33  were  all  pre- 
pared in  precisely  the  same  manner  as  No.  28,  hence  the  comparison  be- 
tween them  is  very  instructive.  Nos.  29  and  30  show  strikingly  the  ill 
effects  on  a flour  of  “ heating  ’’  in  the  wheat  ; the  moisture  increases,  while 
the  water-absorbing  power  rapidly  falls  off.  In  Nos.  14^16,  and  19-22, 
the  glutens  were  estimated  immediately  on  doughing  the  flours  : in  the 
other  analyses,  unless  specially  stated  otherwise,  the  doughs  were  first 
allowed  to  stand  one  hour.  Among  the  whole  of  the  flours  examined. 
No.  35,  from  Canadian  Hard  Fyfe  wheat,  stands  pre-eminent  in  the  matter 
of  water-absorbing  power.  The  wheat  from  which  this  sample  was  made 
grew  in  Manitoba,  to  the  north-west  of  Winnipeg,  and  was  forwarded  by 
the  Canadian  Pacific  Railway  Company.  One  of  the  authors  personally  visited 
this  district  in  1893,  and  collected  samples  of  flour  which  are  among  those 
included  in  Chapter  XXVI  on  Flour  Testing. 

The  results  of  examination  of  a number  of  well-known  brands  and 
varieties  of  flour  are  given  on  pages  367  and  368.  The  Hungarian  flour. 
No.  37,  is  of  the  same  brand  as  is  No.  10.  In  the  first  five  flours  the  glutens 
were  estimated  immediately,  while  in  those  following,  the  doughs  were  first 
allowed  to  stand  an  hour.  The  flours  Nos.  42-44  were  made  from  Hard  Fyfe 
wheat.  No.  79  in  the  preceding  chapter.  Nos.  39-50  are  a number  of  well- 
known  brands  of  American  flour.  Nos.  52-62  are  various  Hungarian 
samples  ; Nos.  52-56  are  different  grades  of  flour  supplied  by  the  one  mer- 
chant ; so  are  Nos.  57-59  ; and  again.  Nos.  60-62.  No.  64  is  registered  as 
a weak  flour  ; it  is,  however,  scarcely  a bread  flour,  being  used  chiefly  as  a 
high-class  biscuit  flour. 

Nos.  65-67  are  flours  supplied  by  one  of  the  largest  and  best  known 
London  millers. 


Flours  used  in  Viscometer  Experiments,  Chapter  XXVI. 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  365 


CO  O .S 
^ O Eej 


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Flours  from  Single  Wheats, 


366 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


is 

° « 

42  ^ 

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Well-known  Brands  and  V’arieties  of  Flour. 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  367 


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Well-known  Brands  and  Varieties  of  Flour — Continued. 


868 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


p . 

0 Sj 

cc  S 
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Lbs.  per 

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Flour. 

67-87 

66-97 

66-53 

65-19 

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65-19 

54-47 

56- 70 

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t-*  Ir-  t-  Ir- 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  369 


Nos.  68-70  were  milled  at  the  same  time  as  Nos.  28-33. 

Nos.  71-73  were  obtained  from  Glasgow,  and  are  representative  samples 
of  home-milled  flours  from  American  wheats. 

No.  74  is  a sample  of  Pillsbury's  well-known  flour,  imported  into  London 
by  Messrs.  Klein  & Sons. 

The  results  of  some  more  recent  tests  on  flours  is  given  in  Chapter  XXVI 
on  The  Commercial  Testing  of  Wheats  and  Flours. 

496.  General  Relationship  existing  between  Water-Absorbing  Power, 
Gluten,  Moisture,  and  Colour  of  Flours. — Reviewing  the  whole  series,  the 
highest  water-absorbing  powers  are  not  associated  with  highest  glutens, 
neither  are  they  with  lowest  moistures  ; while  the  low  strengths  are  in 
some  instances  found  with  low,  and  in  others  with  high  glutens.  Compar- 
ing water  absorption  with  moisture,  the  dryness  of  a flour  does  not  necessarily 
correspond  with  its  water-absorbing  power,  although  in  many  instances 
a connection  may  be  observed  between  them.  With  one  and  the  same  flour, 
increase  or  decrease  of  moisture  influences  the  water-absorbing  capacity 
to  a very  marked  degree.  The  colour  does  not  bear  a very  close  relation- 
ship to  the  other  properties  referred  to,  because  it  is  so  largely  governed  by 
the  methods  employed  in  milling.  With  flours  produced  at  different  stages 
of  the  same  milling  process  from  one  wheat  or  wheat  mixture,  the  colour 
almost  always  falls  off  with  increase  in  water-absorbing  power  and  gluten. 

In  judging  the  value  of  a flour  from  the  analytic  data  given,  the 
water-absorbing  capacity  may  in  the  first  place  be  taken  as  the  measure 
of  the  water  required  by  the  flour  to  produce  dough  ; it  also  is  the 
principal  factor  in  determining  the  bread-yielding  capacity  of  the  flour. 
Water-absorption  tests  after  standing,  or  their  equivalents,  as  briefly 
referred  to  in  another  part  of  this  work,  indicate  the  degree  which  the  dough 
will  fall  off  during  fermentation.  The  gluten  is  in  the  first  place  an  approxi- 
mate measure  of  the  flesh-forming  constituents  of  the  flour,  and  thus  partly 
of  its  nutritive  value.  The  quantity  and  quality  of  gluten  will  determine 
the  capacity  of  the  flour  for  retaining  the  water  used  in  doughing  ; and 
also,  whether  or  not  the  loaf  will  be  well  risen  and  of  good  pile.  For  in- 
stance, although  flour  No.  16,  Gradual  Reduction  Table,  will  greedily  absorb 
water,  yet  it  would  not  produce  so  well  risen  a loaf  as  No.  15  : this  is  partly 
due  to  its  containing  less  gluten,  but  also  to  its  gluten  being  of  inferior 
quality.  The  dryness  of  the  flour  shows  the  actual  percentage  of  solid  food- 
stuffs which  it  contains  ; and  also,  as  has  previously  been  explained,  affords 
indications  of  its  soundness.  The  colour  of  the  flour,  when  wetted,  is 
an  approximate  measure  of  the  colour  of  the  bread  made  therefrom  ; but 
discrepancies  between  the  colours  of  the  flour  and  that  of  the  bread  are 
frequently  observed,  which  in  some  instances  are  probably  due  to  irregular- 
ities in  the  bread-making  process.  The  same  flour  will  produce  bread  of 
many  shades  of  difference  in  colour,  according  to  whether  it  be  properly 
or  improperly  manipulated. 

497.  Effect  of  the  Germ  on  Flour. — One  of  the  questions  which  for  a 
considerable  time  has  occupied  the  attention  of  the  milling  world,  is  whether 
or  not  the  removal  of  the  germ  affects  the  flour  injuriously  or  otherwise. 
Among  the  various  authorities  on  this  point,  Graham,  Richardson,  and 
others,  are  unanimous  in  expressing  a strong  opinion  in  favour  of  its  removal. 
Briefly  stated,  the  reasons  that  render  this  course  advisable  are  that  the 
presence  of  the  germ  discolours  the  flour,  and  also,  as  a result  of  its  high 
percentage  of  fat,  gives  it  a decided  tendency  to  become  rancid.  In  ad- 
dition, the  germ  exerts  a marked  diastatic  action  on  the  imperfectly  matured 
starch  of  slightly  unsound  flours.  On  the  other  hand,  the  advocates  for 
the  retention  of  the  germ  assert  that  it  renders  the  flour  sweeter,  and  also 

B B 


370 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


causes  the  bread  to  have  a pleasant  moistness  on  the  palate.  Under  any 
circumstances  these  results  are  not  likely  to  be  attained  except  by  using 
the  flour  immediately  it  is  milled  ; this  is  frequently  impossible,  and  even 
then  the  baker  must  be  prepared  to  face  all  those  difficulties  caused  by  the 
presence  of  an  undue  quantity  of  active  diastatic  agents  in  the  sponge  and 
dough.  Milling  experiments  on  a large  scale  have  been  made  on  the  germy 
semolina  produced  during  gradual  reduction.  Such  semolina,  on  being 
reduced  on  stones,  yields  a dark  coloured  unsatisfactory  flour,  which  pro- 
duces a low  quality  bread.  On  rolling  and  repurifying  these  semolinas, 
the  resulting  flour  is  of  good  colour,  and  yields  bread  of  high  quality.  So 
far,  these  experiments  afford  evidence  directly  in  favour  of  the  removal 
of  the  germ.  An  extensive  series  of  experiments  made  by  one  of  the 
authors,  and  previously  published,  prove  most  conclusively  the  ill  effects 
resulting  from  the  admixture  of  germ  with  flour. 

498.  Fatty  Matters  and  Acidity  of  Flours. — Balland  has  made  a series 
of  determinations  of  these  with  the  following  results  : — ■ 

Wheat  germs  mixed  with  bran  from  a recent  milling. — .The  fatty  matter 
extracted;  by  ether  contained  about  83*34  per  cent,  of  a fluid  oil,  and  16*66 
per  cent,  of  solid  fatty  acids.  The  original  substance  also  contained  other 
acids  insoluble  in  ether. 

Flour  from  soft  wheat,  for  army  rations,  from  an  old  milling. — ^The  fatty 
matters  contained  about  18  per  cent,  of  a very  fluid  oil,  and  82  per  cent,  of 
mixed  fatty  acids.  The  acidity  of  the  flour  was  due  to  several  acids,  some 
soluble  in  water,  alcohol,  and  ether,  and  others  insoluble  in  water  and  in 
ether. 

Flour  from  hard  wheat,  for  army  rations,  from  an  old  milling. — .The  fatty 
matters  were  composed  entirely  of  free  fatty  acids,  which  hindered  the 
hydration  and  extraction  of  the  gluten.  Balland  deduces  the  following 
general  conclusions  : — The  fatty  matters  of  freshly  milled  flour  consist  of  a 
very  fluid  oil  and  solid  fatty  acids  of  different  melting  points.  In  course 
of  time  the  oil,  which  is  very  abundant  at  first,  gradually  diminishes  and 
disappears,  with  a corresponding  increase  of  the  fatty  acids,  so  that  the 
ratio  of  oil  to  fatty  acids  is  a measure  of  the  age  of  the  flour.  The  fatty 
acids  themselves  disappear  in  time  and  are  not  found  in  very  old  flours. 
The  conversion  of  the  oil  into  fatty  acids  is  not  limited  to  the  flour  only,  it 
takes  place  also  in  the  products  isolated  by  ether.  The  acidity,  which  is 
the  first  indication  of  alteration  of  the  flour,  is  not  connected  with  the  bac- 
terial decomposition  of  the  gluten,  but  is  derived  directly  from  the  fat.  The 
gluten  is  not  attacked  until  the  fatty  acids  produced  from  the  oil  begin  to 
disappear.  The  richer  the  flour  is  in  oil,  the  more  liable  it  is  to  alteration — 
as,  for  instance,  flour  from  hard  wheat.  In  order  to  have  a flour  which  will 
keep  well,  it  is  advisable  to  select  a soft  wheat  with  a low  percentage  of  fat. 
{Comptes  rend.,  1903,  137,  724). 

499.  Distribution  of  Gluten  in  Wheat. — Considerable  interest  attaches 
to  the  relative  ^proportions  of  gluten  in  the  flours  produced  during  the  dif- 
ferent operations  of  gradual  reduction.  Closely  connected  with  this  ques- 
tion is  that  of  the  distribution  of  gluten  in  the  wheat  grain.  A number  of 
writers  on  wheat  make  the  statement  that  gluten  is  found  almost,  if  not 
quite,*  exclusively  in  the  inner  layer  of  the  bran  ; and  that  it  constitutes 
the  contents  of  those  cuboidal  cells  seen  so  prominently  in  the  inner  layer 
of  bran  when  microscopically  examined.  These  cells  are  even  now  fre- 
quently termed  “ gluten  cells  ” from  this  supposed  property.  The  bran 
of  wheat  contains,  however,  no  gluten  whatever,  the  whole  of  that  body 
being  derived  from  the  contents  of  the  endosperm.  Hence  it  follows  that 
flour  contains  more  gluten  than  does  whole  wheat  meal.  The  following 


COMPOSITION  OF  FLOUR  AND  MILLING  PRODUCTS.  371 


methods,  suggested  by  Randolph  of  Philadelphia,  may  be  adopted  in  order 
to  j^rove  the  presence  of  gluten  in  the  endosperm  of  wheat. 

If  whole  wheat  grains  be  allowed  to  soak  in  water,  to  which  a few  drops 
of  ether  have  been  added  to  prevent  germination,  they  will  in  a few  days 
become  thoroughly  softened,  and  the  contents  of  such  a grain  may  then 
be  squeezed  out  as  a white  tenacious  mass.  Examination  of  the  remaining 
bran  shows  the  “ gluten  cells  ” undisturbed,  closely  adhering  to  the  cortical 
protective  layers.  By  now  carefully  washing  the  white  extruded  mass,  the 
major  part  of  its  starch  may  be  removed  ; and  upon  the  addition  of  a drop 
of  iodine  solution  microscopic  examination  shows  numerous  networks  of 
fine  yellow  fibrils,  still  holding  entangled  in  their  meshes  many  starch  gran- 
ules, coloured  blue  by  the  iodine.  In  carefully  washed  specimens  these 
sj^ongelike  networks  are  seen  to  retain  the  outline  of  the  central  starch- filled 
cells,  and  evidently  constitute  the  protoplasmic  matrix  in  which  the  starch 
granules  lay.  Upon  gently  tearing  such  a specimen  under  a moderate 
amplification,  the  fibrils  will  be  seen  to  become  longer  and  thinner,  in  a 
manner  possible  only  to  viscid  and  tenacious  substances — a class  repre- 
sented in  wheat  by  gluten  alone. 

An  eminently  satisfactory  proof  of  the  protein  nature  of  these  central 
networks  may  be  obtained  by  heating  the  specimen  in  the  solution  of  acid 
nitrate  of  mercury  (Millon’s  reagent),  when  the  fibrils  will  assume  the  bright 
pink  tint  characteristic  of  proteins  under  this  treatment. 

Another  most  satisfactory  method  of  studying  the  distribution  of  gluten 
in  sections  of  wheat,  is  that  of  removing  the  starch  by  diastasis  effected  by 
malt  infusion.  If  a thin  section  of  a wheat  grain  be  momentarily  placed 
in  water  at  100°  C.,  so  as  to  gelatinise  the  starch,  then  transferred  when 
cool  to  filtered  malt  infusion,  and  maintained  from  half-an-hour  to  an  hour 
at  a temperature  of  about  60°  C.,  all  the  starch  will  be  digested  away,  while 
the  insoluble  protein  and  other  constituents  will  remain  entirely  unaltered. 
A section  of  wheat  grain  thus  treated  will  exhibit  throughout  its  entire 
central  portion  close-meshed  gluten  networks,  which  become  slightly  denser 
towards  the  cortex  of  the  grain.  The  protein  character  of  these  reticuli 
is  here,  as  in  the  first  method,  susceptible  of  micro -chemical  demonstration 
by  Millon’s  reagent.  A relatively  very  faint  colouration,  indicating  the 
presence  of  proteins,  is  noticeable  in  the  “ gluten  cells,”  while  the  gradual 
condensation  of  the  gluten  of  the  endosperm  as  the  cortex  is  approached 
is  evidenced  by  a vivid  colouration  of  the  fibrils. 

500.  Baking  Characteristics  of  Typical  Flours. — The  tables  on  pages 
372  and  373  record  not  only  the  gluten  and  other  determinations  in 
certain  typical  flours,  but  also  contain  a statement  of  their  general  baking 
characteristics . 

501.  Seasonal  Variations  in  Flours. — Balland  arrived  at  the  following 
conclusions  from  the  analysis  of  2,500  samples  of  flour  analysed  in  the 
Laboratory  of  the  French  War  Department  between  September,  1891, 
and  June,  1894.  He  finds  the  water  to  vary  from  9*40  to  16*20,  being  at 
a maximum  in  February  and  a minimum  in  August.  The  lowest  percentage 
of  acid  found  by  him  was  0*013  per  cent,  in  January,  while  samples  ex- 
amined in  August  contained  as  much  as  0*037.  From  this  he  draws  the 
conclusion  that  flours  for  long  storage  should  be  made  and  packed  in  dry 
cold  weather.  The  moisture  present  in  wet  glutens  is  found  to  vary  from 
52  to  71*3  per  cent.  ; that  in  the  best  flours  for  bread-making  being 
about  70  as  against  62  to  65  in  those  of  medium  quality.  As  the  acidity 
of  the  flour  increases  the  percentage  of  water  in  the  wet  gluten  diminishes. 
None  of  these  flours  contained  either  foreign  mineral  matter  or  farinaceous 
substances  as  adulterants.  {Comptes  Rend.,  119,  565.) 


Typical  Flours  and  their  Characters. 


372 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


* 


Typical  Flours  and  their  Characters — Continued. 


COMPOSITION  OP  FLOUR  AND  MILLING  PRODUCTS.  373 


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374 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


502.  Preservation  of  Flour  by  Cold. — Balland  finds  that  flour  stored 
for  three  years  in  a vessel  maintained  at  a temperature  ranging  between 
— 2 and  + 2°  C.  underwent  very  little  change.  The  sample  was  somewhat 
tasteless,  a result  probably  of  moisture  in  the  apparatus.  The  amount  of 
gluten  had  slightly  increased,  as  compared  with  a test  on  the  new  flour  ; 
it  was  homogeneous,  sweet,  and  contained  71  per  cent,  of  water.  The 
fatty  matters  and  acids  were  present  in  the  same  quantities  as  in  the  original 
flour.  {Comptes  Rend.,  1904,  139,  473.) 

503  “ Strengthening  ” Flours. — Balland  states  that  certain  forms  of 
flour  have  been  introduced  into  France  from  Russia  for  the  purpose  of 
improving  and  increasing  the  yield  of  bread  from  flours  poor  in  gluten. 
Three  such  brands  of  flour  yielded  the  following  figures  on  analysis  : — 


“ Champion.” 

“ Hercules.” 

“ Samson.” 

Water 

9-90 

10-70 

11-00 

Nitrogenous  matters 

29-48 

22-11 

16-43 

Fatty  matters 

1-60 

1-45 

1-20 

Starchy  matters 

58-22 

64-94 

70-65 

Cellulose 

0-20 

0-25 

0-27 

Ash 

0-60 

0-55 

0-45 

Gluten,  moist 

82-80 

64-50 

46-40 

,,  dried 

29-10 

22-00 

16-00 

Total  Nitrogen 

4-717 

3-537 

2-628 

Acidity 

0-073 

0-065 

0-065 

These  flours  were  apparently  mixtures  of  wheat  flour  with  gluten  flour 
(made  by  the  careful  desiccation  and  grinding  of  gluten).  The  addition 
of  such  flours  to  an  over-bolted  flour  will  make  good  its  deficiency  in  nitro- 
genous matters.  {Comptes  Rend.,  131  [13],  545). 

It  may  be  doubted  whether  any  milling  operation  in  the  way  of  bolting 
can  really  remove  the  gluten  from  a sample  of  flour.  There  is  less  gluten 
in  the  flour  derived  from  the  centre  of  the  grain  than  from  the  outer  parts 
of  the  endosperm,  but  the  difference  is  not  very  great.  The  central  flour 
from  a very  strong  wheat  may  contain  more  gluten  than  the  outer  flour 
from  a very  weak  wheat.  Starting  with  a fine  flour,  it  seems  scarcely 
probable  that  any  milling  process  of  bolting  will  effect  a marked  separa- 
tion of  the  starch  from  the  gluten.  In  all  probability  the  very  weak  French 
flours  are  manufactured  from  correspondingly  weak  wheats.  The 
simplest  remedy  would  be  to  add  strong  Russian  or  other  wheats  to  the 
weaker  wheat  ; or  naturally  strong  flour  to  the  weaker  variety.  Very  pos- 
sibly these  “ strengthening  flours  have  their  raison  d'etre  in  an  import 
duty  which  renders  it  more  economical  to  use  these  artificially  prepared  flours, 
rather  than  the  untreated  product  of  the  wheat. 


CHAPTER  XVIL 

THE  BLEACHING  OF  FLOUR. 


504.  Early  Investigations. — The  subject  of  flour  bleaching  came  first 
before  one  of  the  authors  in  a practical  form  in  the  shape  of  an  inquiry 
from  one  of  the  most  widely  known  flour  merchants  of  Liverpool.  That 
gentleman  submitted  samples  of  Californian  and  Oregon  flours  and  pointed 
out  that  in  most  properties  the  two  were  identical,  and  yet  that  as  a result 
of  the  Californian  being  a white,  and  the  Oregon  a very  yellow  flour,  the 
former  commanded  a considerably  higher  price.  The  question  asked  was 
can  the  colour  of  the  Oregon  flour  be  removed  so  as  to  make  it  similar  in 
colour  as  well  as  in  other  properties  to  Californian  flour  ? In  consequence 
a number  of  experiments  were  made  in  order  to  remove  the  colour  if  pos- 
sible, ozone  being  employed  for  that  purpose.  The  experiments  were  re- 
linquished because,  although  the  flour  was  bleached,  it  also  acquired  an 
unpleasant  flavour  or  taint,  rendering  it  unfit  for  use.  This  occurred  a 
number  of  years  ago,  and  subsequently  Frichot  in  1898  recommended  and 
patented  the  employment  of  electrically  produced  ozone  for  the  purpose 
of  bleaching  flour,  but  for  the  same  reason,  the  production  of  this  taint, 
the  process  was  not  commercially  successful. 

Attention  was,  however,  thus  directed  to  the  possibility  of  removing 
more  or  less  of  its  natural  colour  from  flour,  and  this  problem  became  the 
subject  of  much  attention. 

505.  Sources  of  Colour  in  Flour. — The  following  may  be  taken  as  a 
classification  of  the  nature  and  sources  of  the  colouring  matter  present  in 
flour. 

1.  Bran. — The  outer  envelope  of  the  wheat  grain  is  from  a pale  yellow 
to  a reddish-brown  tint,  and  contains  large  quantities  of  colouring  matter. 
If  finely  ground  bran  finds  its  way  into  flour,  the  particles  impart  their  own 
tint  to  the  flour,  and  when  made  into  bread  this  colour  is  intensified  by 
being  dissolved  and  permeating  the  whole  of  the  substance  of  the  bread. 

2.  Crmse  and  other  Dirt. — ^Outside  dirt,  especially  that  of  the  crease 
of  the  grain,  may  be  ground  up  into  the  flour,  and  will  thus  give  it  a sad, 
bluish-grey  tint. 

3.  Colouring  Matter  of  Endosperm. — ^In  some  wheats  the  whole  endo- 
sperm is  more  or  less  coloured  yellow.  A notable  instance  of  these  is  Walla 
Walla  wheat  of  Oregon  (before  referred  to),  which  yields  a flour  sometimes 
as  yellow  as  a primrose. 

Removal  of  Colour. 

1.  Bran. — This  is  now  removed  by  careful  milling  and  purification 
from  all  small  bran  particles. 

2.  Crease  Dirt. — -To  get  rid  of  this  and  other  outside  dirt,  the  grain  is 
thoroughly  scoured  and  pohshed  in  the  dry  state,  or  washed  and  dried. 
Further,  the  grains  are  in  the  first  operations  of  milling  carefully  spht  longi- 
tudinally along  the  crease,  and  the  dust  lodged  therein  got  rid  of  before 
any  further  reduction  of  the  broken  grain  into  flour. 

Note. — Regarding  the  flour  as  consisting  only  of  the  endosperm  of  the 
grain  (or,  as  it  is  sometimes  called,  the  kernel  or  the  berry),  ground  into  a 
fine  powder,  the  removal  of  bran  and  crease  dirt  is  only  a removal  of  foreign 
substances,  and  a consequent  purification  of  the  flour. 

375 


376 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


3.  Colouring  Matter  of  Endosperm. — ^This  evidently  stands  in  a different 
category,  because  it  is  the  colour  of  the  flour  itself,  and  not  that  of  any  foreign 
matter,  even  from  other  parts  of  the  grain. 

This  colouring  matter  is  somewhat  unstable  in  character,  as  it  dimin- 
ishes very  noticeably  on  keeping  flour  some  two  or  three  months,  and  also 
varies  considerably  in  different  flours. 

506.  Nature  of  Bleaching  Agents. — Since  the  suggestion  of  ozone  other 
bleaching  agents  have  been  proposed  and  commercially  used  ; among  those 
which  are  practicable  being  nitrogen  peroxide,  NO2,  and  chlorine.  It  will 
be  noticed  that  these  together  with  ozone,  are  all  of  them  direct  or  indirect 
oxidising  agents. 

The  bleaching  action  is  not  necessarily  one  of  oxidation,  because  flour 
may  also  be  bleached  by  sulphur  dioxide,  a powerful  reducing  agent. 

I;  - But  among  all  the  various  bleaching  agents  that  are  now  used  to  the 
practical  exclusion  of  the  others,  is  nitrogen  peroxide,  which  may  be  evolved 
either  by  chemical  means,  as  the  action  of  ferrous  sulphate  on  nitric  acid, 
or  by  the  passage  of  an  electric  discharge  through  air.  While  a silent 
electric  discharge  produces  ozone  in  proportionately  large  quantities,  a dis- 
ruptive or  flaming  discharge  causes  the  production  of  nitrogen  peroxide. 
With  intermediate  forms  of  discharge,  the  resultant  gas  will  contain  a mix- 
ture of  ozone  and  nitrogen  peroxide,  one  or  other  predominating  according 
to  the  nature  of  the  discharge.  But  so  arranging  the  spark  discharge  as 
to  get  an  effective  bleach  and  no  taint,  the  active,  or  at  any  rate,  predomin- 
ating agent,  is  nitrogen  peroxide. 

507.  Andrew’s  Patent. — In  January,  ISOl,  Letters  Patent  (No.  1,661 

of  1901)  were  granted  to  John  and  Sydney  Andrews  for  certain  improve- 
ments in  the  conditioning  of  flour,  which  in  effect  consisted  in  treatment 
with  nitrogen  peroxide  gas.  The  specification  states  that  : — “ The  inven- 
tion consists  essentially  in  subjecting  the  flour  to  the  action  of  a suitable 
gaseous  oxidising  agent,  whereby  nascent  oxygen  or  its  equivalent  is  pro- 
duced or  comes  in  contact  with  the  flour.  A very  small  quantity  of  the 
oxidising  agent  suffices,  so  little  indeed  that  the  actual  composition  of 
the  flour  as  shown  by  analysis  is  hardly  perceptibly  altered.  The  plan  we 
prefer  is  to  pass  the  flour  through  various  conveyors  whereby  it  is  brought 
in  contact  with  the  gaseous  oxidising  agent,  and  the  drawings  we  herewith 
append  show  the  apparatus  which  from  long  experiments  we  have  found 
to  act  best  with  air  carrying  a small  quantity  of  gaseous  nitric  acid  or  per- 
oxide of  nitrogen.  We  do  not,  however,  limit  ourselves  to  the  use  of  nitric 
acid  or  nitrogen  peroxide,  as  we  have  found  that  chlorine,  bromine,  and 
other  gaseous  compounds  capable  of  liberating  oxygen  will  act  with  more 
or  less  efficiency.  . . . The  difficulty,  too,  of  generating  it  [ozone]  in  a 
mill  where  electric  sparking  is  especially  dangerous,  puts  it  beyond  the 
range  of  ordinary  practice,  and,  therefore,  in  speaking  of  suitable  oxidising 
agents  we  do  not  recommend  it  but  exclude  its  use.  . . . By  the  above- 
mentioned  treatment  the  colour  of  the  flour  is  made  whiter,  its  baking 
qualities  are  improved,  and  it  is  attacked  by  mites  and  other  organisms 
to  a far  smaller  extent.  No  deleterious  action  on  the  flour  is  caused  by  the 
above-mentioned  treatment.”  The  Patentees  claimed  : — “ (1)  In  the  process 
of  conditioning  flour  and  the  like,  passing  the  same  with  full  exposure 
through  an  atmosphere  containing  a gaseous  oxide  of  nitrogen  or  chlorine 
or  bromine  oxidising  agent  in  the  gaseous  or  vapourised  state.  (2)  The 
apparatus  for  the  purposes  described  consisting  of  a device  for  impregnat- 
ing air  with  a gaseous  oxidising  agent,  a rotating  conveyor  receiving  the 
oxidising  atmosphere  and  through  which  the  material  to  be  treated  is 
passed  in  a regulated  stream.”  ... 


THE  BLEACHING  OF  FLOUR. 


377 


508.  Alsop’s  Patent. — In  June,  1S03,  Letters  Patent  (No.  14,006  of 
1903)  were  granted  to  J.  N.  Alsop  for  an  improved  process  of  treating  flour 
to  purify  the  same  and  increase  the  nutritive  qualities  thereof.  The  speci- 
fication states  that  : — “ This  invention  relates  to  a novel  process  of  treating 
flour  to  purify  the  same  and  increase  the  nutritive  qualities  thereof,  and 
to  this  end  resides  broadly  in  subjecting  the  flour  to  the  action  of  a gaseous 
medium  which  will  operate  to  bleach  or  purify  the  flour  and  cause  a reduc- 
tion of  the  quantity  of  the  carbohydrate  contents,  and  an  increase  in  the 
quantity  of  the  protein  contents  thereof.  The  gaseous  medium  which  I 
employ  is  atmospheric  air  which  has  been  subjected  to  the  action  of  an  arc, 
or  flaming  discharge,  of  electricity.  . . . I am  at  this  time  unable  to  explain 
the  reason  for  the  change,  which  is  produced  in  the  flour  by  treating  it 
according  to  my  process,  but  in  lieu  of  such  explanation,  I will  give  the 
result  of  the  chemical  analysis  before  and  after  its  treatment  by  my  process. 
. . . Two  samples  of  flour  were  submitted  for  analysis  to  a professor  of 
chemistry  in  Columbian  College,  Washington,  D.C.  : — 


Water 

Before  treatment. 

9*84 

After  treatment. 

10*13 

Starch,  etc. 

74*11 

62*24 

Proteins,  etc. 

14*99 

26*71 

Ash 

0*44 

0*30 

Fat 

0*62 

0*62 

“ It  will  thus  be  seen 

that  the  flour  which  had  been  treated  showed  an 

increase  of  11*72  parts  of  proteins,  and  a decrease  of  0*14  parts  of  ash,  and 
of  11*87  parts  of  starch.  ...  As  an  incidental  result  of  treating  the  flour 
by  my  process  it  is  as  above  stated,  highly  purifled  and  whitened."’  Based 
on  this  description  were  claims  for  : — “ (1)  The  process  of  treating  flour 
which  consists  in  subjecting  the  same  to  the  action  of  air  which  has  previ- 
ously been  subjected  to  the  action  of  an  arc  or  flame  of  electricity,  sub- 
stantially as  described.  ...  (6)  The  process  of  treating  flour,  which  con- 

sists in  subjecting  it  to  the  action  of  a gaseous  medium  capable  of  bleaching 
the  flour  and  of  simultaneously  producing  a decrease  in  the  quantity  of  the 
carbohydrate  contents,  and  an  increase  in  the  quantity  of  the  protein  con- 
tents thereof,  substantially  as  described.” 

Subsequent  investigation  showed  that  the  patentee  was  mistaken  in 
supposing  that  his  treatment  increased  the  protein  content  of  the  flour,  and 
accordingly  in  December,  1906,  the  Comptroller  General  of  the  Patent  Offlce 
allowed  the  specification  to  be  amended  by  cancelling  those  claims  which 
claimed  the  increase  of  proteins  as  a part  of  the  invention  (of  which 
No.  6 above  is  an  example).  The  patent  then  became  one  for  the  subjec- 
tion of  flour  to  air  treated  electrically  in  the  manner  described,  and  without 
any  specific  claim  to  bleaching  action. 


509.  Author’s  Investigation. — The  treatment  of  flour  by  Andrew’s 
Patent  was  investigated  by  one  of  the  authors  and  the  results  published 
in  1903.  Altogether  seventeen  samples  of  flour  were  taken  personally,  of 
which  the  following  is  a description : — 


No.  Description. 

I.  Patent  from  Walla  Wheat.  Untreated. 

II-  5,  ,,  ,,  ,,  ^ Once  treated  in  model  machine. 

5,  ,,  „ ^ Thrice  „ ,,  ,,  ,, 

^ This  was  treatment  in  a small  model  machine  to  the  extent  considered  by  the 
patentees  as  representing  a full  commercial  bleach. 

^ This  was  treatment  to  fully  three  times  the  extent  of  that  in  the  preceding  test, 
and  is  far  in  excess  of  any  possible  commercial  treatment. 


378 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  Description,  continued.  ' 

IV.  Spring  American  Patent.  Untreated. 

V.  „ „ ,,  Once  treated  in  model  machine. 

VI.  „ „ „ Thrice  „ 

VII.  Winter  American  Patent.  Untreated. 

VIII.  ,,  ,,  ,,  'Once  treated  in  model  machine. 

IX.  ,,  ,,  ,,  Thrice  ,,  ,,  ,,  ,, 

X.  Kansas  Patent.  Untreated. 

XI.  ,,  ,,  Once  treated  in  model  machine. 

XII.  Low  Grade  from  Walla  Wheat.  Untreated. 

XIII.  ,,  ,,  ,,  ,,  ,,  Once  treated  in  model  ma^chine. 

XIV.  Patent  from  Walla  Wheat.  Untreated. 

XV.  ,,  ,,  ,,  ^ Treated  in  mill. 

XVI.  Low  Grade  from  Walla  Wheat.  Untreated. 

XVII.  ,,  „ ,,  ,,  ^ Treated  in  mill. 

The  following  are  the  results  of  analysis  : — 


I. 

II. 

III. 

IV. 

V. 

VI. 

Proteins  soluble  in  Water  . . 

1-82 

2-07 

2-55 

Gliadin  ex  Gluten  . . 

— . 

— 

— 

715 

9-35 

10-25 

Glutenin  ,,  ,, 

— 

— 

— 

5-66 

3-18 

1-95 

Total  Proteins 

— 

— 

— 

14-63 

14-60 

14-75 

Gluten,  Wet 

331 

33-3 

30-1 

44-0 

44-6 

45-0 

„ Dry 

10-2 

9-3 

8-64  ! 

14-84 

15-11 

15-58 

,,  True 

— 

— 

— 

12-81 

12-53 

12-20 

Water  Absorption  . . 

640 

63-5 

61-0 

75-5 

75-0 

73-5 

i VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

Proteins  soluble  in  Water  . . 

1-61 

1-59 

Gliadin  ex  Gluten  . . 

6-52 

6-07 

— 

— 

— 

— 

Glutenin  ,,  ,, 

3-12 

3-50 

— 

— 

— 

— 

Total  Proteins 

11-25 

11-16 

— 

— 

— 

— 

Gluten,  Wet  . . . . 

37-3 

37-0 

35-9 

52-2 

52-3 

37-1 

„ Dry  ..  .. 

11-15 

10-66 

11-26  i 

16-45 

16-45 

12-59 

„ True 

9-64 

9-57 

— 

— 

— 

— 

Water  Absorption  . . . . 

61-0 

60-5 

62-0 

65-0 

65-5 

XIII. 

XIV. 

XV. 

XVI. 

XVII. 

1 

Proteins  soluble  in  Water  . . 

1-20 

1-20 

i 

Gliadin  ex  Gluten  . . 

— 

5-59 

5-44 

— 

— 

Glutenin  ,,  ,, 

— 

2-60 

2-66 

— 

— 

Total  Proteins 

— 

9-39 

9-30 

— 

— 

Gluten,-  Wet 

35-5 

32-6 

35-0 

34-8 

33.8 

„ Dry 

11-65 

10-0 

11-23 

11-55 

11-70 

,,  True 

— 

8-19 

8-10 

— 

— 

Water  Absorption  . . 

61-0 

63-0 

56-0 

58-5 

* These  were  samples  treated  on  the  large  scale  in  the  ordinary  way  of  manufacture.. 


THE  BLEACHING  OF  FLOUR. 


379 


The  whole  of  the  above  results  are  expressed  in  per  centages,  except 
those  of  water  absorption,  which  were  determined  by  the  viscometer  and 
the  results  expressed  in  quarts  per  sack. 

Pekar  Colour  Tests,  Results  of : — 

No.  I. — Characteristic  Full  Yellow  Tint. 

No.  II. — Colour  almost  entirely  discharged. 

No.  III. — Practically  identical  with  No.  II. 

No.  IV. — Greyish  Tint  of  Spring  American  Flours. 

No.  V. — Colour  very  much  lighter. 

No.  VI. — Very  slightly  lighter  than  No.  V. 

No.  VII. — Usual  tint  of  winter  patents. 

No.  VIII. — Colour  almost  entirely  discharged. 

No.  IX. — Practically  identical  with  No.  VIII.  . 

No.  X. — Good  colour  Kansas  Flour. 

No.  XI. — Colour  very  much  lighter. 

No.  XII. — Very  dark  and  sad  grey  tint. 

No.  XIII. — Colour  improved,  but  still  very  dark. 

No.  XIV. — Characteristic  Full  Yellow  Tint. 

No.  XV. — Colour  almost  entirely  discharged. 

No.  XVI. — Very  dark  colour. 

No.  XVII. — Colour  improved,  but  still  dark. 

Baking  Tests  were  made  on  small  quantities  of  flour  with  the  follovung 
results  : — 

Nos.  I.,  II.  and  III. — ^Very  little  difference  in  quantity  of  water 
taken  or  general  behaviour  during  fermentation.  Crumb  of  No.  I.  loaf 
full  yellow  colour.  No.  II.  much  whiter,  difference  very  striking.  No.  III. 
very  slightly  whiter  than  No.  II.  No  perceptible  difference  in  odour  or 
taste  of  Nos.  I.  and  II.  No.  III.  possessed  the  unpleasant  odour  of  over- 
treatment. (See  subsequent  reference.)  This  flour  was  too  weak  to  bake 
properly  by  itself  by  the  method  of  testing  that  was  employed. 

Nos.  IV.,  V.  and  VI. — The  same  quantity  of  water  was  used  with  all 
three  samples.  No.  VI.  worked  the  best.  No.  V.  the  next,  and  No.  IV. 
the  last.  Being  a very  strong  flour.  No.  IV.  was  “ gluten-bound,""  but 
Nos.  V.  and  VI.  worked  much  freer,  yielding  a bolder  and  better  shaped 
loaf.  In  colour.  No.  V.  was  a marked  improvement  on  No.  IV.,  and  No. 
VI.  was  again  slightly  lighter.  Nos.  IV.  and  V.  showed  no  differences  in 
flavour  or  odour,  but  No.  VI.  had  the  same  unpleasant  smell  of  over- 
treatment. 

Nos.  VII.,  VIII.  and  IX. — In  these  flours  No.  IX.  took  rather  less  water 
than  the  other  two  at  the  start,  but  worked  better  and  held  up  better. 
Same  improvement  in  colour,  again  slight  improvement  in  thrice  treated 
sample.  In  this  case  No.  IX.  was  devoid  of  smell  of  over-treatment. 

Nos.  X.  and  XI. — The  latter  worked  slightly  the  better  ; the  improve- 
ment in  colour  was  very  marked,  but  not  quite  so  striking  as  with  the  very 
yellow  flours.  No  difference  in  odour  or  flavour. 

Nos.  XII.  and  XIII. — The  very  low  grades  show  an  improvement  in 
colour,  but  as  would  be  expected,  the  bleaching  cannot  confer  a bloom 
which  is  not  present  in  the  original  flour  itself.  So  far  as  the  colour  of  the 
low  grade  is  due  to  crease  dirt,  and  other  external  dirty  matter,  such  matter  is 
of  a description  which  is  only  slightly  if  at  all  amenable  to  bleaching  processes. 

Nos.  XIV.  and  XV. — These  flours  are  practically  the  same  as  Nos.  I. 
and  II.,  except  that  the  bleaching  treatment  has  been  carried  out  on  the 
manufacturing  scale  in  the  mill,  instead  of  in  the  small  model  machine. 
The  results  are  practically  identical  ; and,  if  anything.  No.  XV.  showed  a 
greater  improvement  over  No.  XIV.  than  No.  II.  did  over  No.  I.  There 


380 


THE  TECHNOLOGY  OF  BREAD-MAKINGo 


was  not  the  slightest  sign  of  any  deterioration  in  odour  or  flavour  of  No. 
XV.  compared  with  XIV. 

Nos.  XVI.  and  XVII.  are  practically  repetitions  of  Nos.  XII.  and  XIII., 
except  that  the  treatment  was  carried  out  on  the  manufacturing  scale. 

Presence  of  Foreign  Matters  in  the  treated  flour.  It  must  first  be 
remembered  that  nothing  is  added  to  the  flour  but  minute  quantities  of  the 
oxides  of  nitrogen,  produced  from  nitric  acid  in  the  cold,  and  therefore 
under  conditions  in  which  the  vapours  of  nitric  acid  are  not  likely  to  be 
formed.  The  following  is  a brief  explanation  of  the  probable  theory  of  the 
process.  The  nitrogen  of  nitric  acid  exists  in  the  form  of  an  oxide  consisting 
of  two  atoms  of  nitrogen  and  five  atoms  of  oxygen,  which  may  be  rendered 
by  the  chemical  formula,  N2O5.  By  the  action  of  the  ferrous  sulphate 
this  body  is  reduced  to  N2O4  by  the  abstraction  of  an  atom  of  oxygen. 
N2O4  is  a ruddy  coloured  gas,  which  immediately  escapes.  This  gas  on 
coming  in  contact  with  flour  imparts  oxygen  to  its  colouring  matter,  which 
it  so  oxidises  to  colourless  products.  In  effecting  this  change  the  N2O4 
is  changed  into  a colourless  gas,  N2O2.  This  latter  possesses  the  remark- 
able property  of  at  once  combining  with  the  oxygen  of  the  air,  and 
again  becoming  N2O4,  which  in  its  turn  oxidises  more  flour  and  is  again 
reduced  to  N2O2.  In  theory  this  series  of  changes  may  go  on  indefinitely 
and  thus  a very  small  quantity  of  the  nitrous  fumes  may  act  many  times 
over  as  a carrier  of  oxygen  from  the  air  to  the  colouring  matter  of  the  flour, 
and  so  may  be  sufficient  to  bleach  large  quantities  of  flour.  (It  is  some- 
times asserted  that  this  bleaching  action  is  one  of  nitration,  but  flour  is 
also  bleached  when  dipped  into  hydrogen  peroxide,  and  no  question  in  that 
case  arises  as  to  the  action  being  anything  but  that  of  oxidation.) 

The  question  arises  whether  any  nitric  acid,  as  such,  is  conveyed  into 
the  flour.  From  d 'priori  reasoning,  the  answer  must  be  in  the  negative. 
The  chemical  reaction  by  which  the  gas  is  first  liberated  is  one  in  which 
the  nitrogen  oxide  of  nitric  acid  (N2O5)  is  reduced  to  N2O4,  and  therefore 
it  is  not  nitric  acid  which  passes  over  at  all.  In  the  next  place,  as  the  action 
on  the  flour  is  one  of  oxidation,  that  on  the  N2O4  must  be  one  of  reduction 
of  the  N2O4  to  N2O2,  which  is  still  further  away  from  nitric  acid.  Conse- 
quently one  would  expect  to  find  no  nitric  acid  in  the  flour.  What  most 
probably  occurs  is  that  the  main  part  of  the  action  is  the  conveyance  of 
oxygen  only  to  the  flour,  and  that  most  of  the  nitrogen  oxides  pass  away 
with  the  air  at  the  close  of  the  bleaching  operation. 

The  following  experiments  have  been  made  in  order  to  investigate  this 
particular  point.  A sample  of  No.  VI.  flour  (three  times  treated  Spring 
American  Patent)  was  placed  in  a vessel  and  air  forced  continuously  through 
the  mass  of  flour  for  an  hour.  This  air  was  next  passed  into  a solution  of 
potassium  iodide  and  starch,  in  order  to  determine  whether  any  oxides 
of  nitrogen  were  thus  taken  out  of  the  flour  by  the  continuous  current  of 
air.  The  potassium  iodide  and  starch  solution  remained  absolutely  colour- 
less, whereas  the  merest  trace  of  nitrogen  oxides  will  thus  develop  a deep 
blue  colour.  The  conclusion  arrived  at  is  therefore  that  no  free  nitrous 
fumes  are  prese7it  in  the  flour. 

Estimation  of  Oxides  of  Nitrogen. — The  next  step  in  the  inquiry  was 
to  determine  whether  any,  and  if  so,  what  quantity  of  lower  oxides  of  nitro- 
gen were  present  in  the  flour  in  a fixed  condition.  For  this  purpose  a modi- 
fication of  the  meta-phenylene-diamine  test  was  devised.  On  the  proper 
application  of  this  test,  the  absence  of  these  oxides  of  nitrogen  is  shown 
by  the  absence  of  any  colouration,  while  their  presence  develops  a brown  tint 
in  the  liquid  under  examination  (which  in  this  case  consisted  of  mixtures 
of  flour  and  water).  This  test  was  applied  to  the  following  flours,  with 
the  results  appended  : — 


THE  BLEACHING  OF  FLOUR. 


381 


IV. — No  colouration. 

V. — Very  slight  colouration. 

VI. — Decided  colouration. 

XI\^. — No  colouration. 

XV. — Slight  colouration. 

Similar  mixtures  of  flour  and  water  were  next  prepared,  to  which  were 
added  known  quantities  of  a standard  solution  of  lower  oxides  of  nitrogen. 
These  tests  were  continued  until  the  colours  of  the  solutions  of  the  flours 
under  examination  had  been  matched. 

In  this  way  it  is  possible  to  make  an  approximate  estimation  of  the 
quantity  of  oxides  of  nitrogen  present  in  the  flour.  The  following  were  the 
results  : — 

No.  IV. — Untreated  Spring  American  Patent.  Free  from  lower  oxides 
of  nitrogen. 

No.  V. — Contained  about  0*0003  per  cent.,  or  3*0  parts  per  million,  and 
certainly  less  than  0*0004  per  cent.,  or  4 parts  per  million. 

No.  VI. — Contained  about  0*0046  per  cent.,  or  46  parts  per  million,  and 
certainly  less  than  0*005  per  cent.,  or  50  parts  per  million. 

No.  XIV. — Untreated  Walla  Patent.  Free. 

No.  XV. — Ditto,  mill  treated,  contained  about  0*00085  per  cent.,  or  8*5 
parts  per  million,  and  certainly  less  than  0*001  per  cent.,  or  10 
parts  per  million. 

It  will  be  seen  that  minute,  but  measurable  traces  of  lower  oxides  of 
nitrogen  are  present  in  the  treated  flours.  Having  regard  to  the  exceed- 
ingly small  quantity  present,  and  the  harmless  nature  of  these  fixed  nitrogen 
bodies  generally,  it  is  probable  that  the  minute  traces  thus  introduced  into 
the  flour  are  absolutely  harmless.  These  fixed  nitrogen  bodies  are  probably 
nitrites,  which  substances  are  closely  akin  to  nitrates,  of  which  bodies  salt- 
petre or  nitre  is  a familiar  example. 

Ageing  Effect  on  Flour. — A study  of  the  general  changes  induced  in 
flour  by  this  oxidising  process  leads  one  to  the  conclusion  that  in  many  ways 
the  changes  are  very  similar  to  those  caused  by  ageing.  The  general  improve- 
ments caused  by  proper  treatment  are  very  similar  to  those  resulting  from 
age  ; while  excessive  treatment  causes  results  not  unlike  those  caused  by 
excess  of  age  on  a flour.  The  authors  are  informed  that  flour  treated  by  this 
oxidising  process  continues  to  improve  for  some  time  during  storage. 
It  is  possible  that  the  minute  trace  of  oxides  of  nitrogen  retained  in  the 
flour  may  continue  to  exert  a beneficial  influence. 

General  Effect  on  Flour  Constituents. — Neither  starch  nor  other  carbo- 
hydrate matter  is  probably  altered  by  this  treatment,  but  certain  changes 
are  induced  in  the  gluten.  In  the  soft  flours.  Nos.  I.,  II.  and  III.,  and  VII., 
VIII.  and  IX.,  the  amount  of  gluten  is  diminished.  In  the  harder  flours 
there  is  not  so  great  a difference,  thus  in  Nos.  IV.,  V.  and  VI.  there  is  a 
slight  increase,  while  Nos.  X.  and  XI,  are  practically  alike.  The  soft  low 
grades,  XII.  and  XIII.,  show  a slight  diminution.  Rather  curiously,  in 
the  mill  treated  samples  there  is  a slight  increase  as  the  result  of  treatment. 
In  order  to  investigate  this  point  somewhat  more  closely,  chemical  deter- 
minations of  albumin,  gliadin,  and  glutenin  were  made  on  some  of  the  more 
typical  flours.  In  Nos.  IV.,  V.  and  VI.  the  albumin  shows  an  increase, 
so  also  does  the  gliadin,  with  necessarily  a corresponding  decrease  in  the 
glutenin.  The  amount  of  change  observed  is  more  than  was  expected, 
but  the  direction  in  which  it  goes  is  that  corresponding  with  an  improvement 
in  the  quality  of  the  gluten  for  baking  purposes  in  a very  strong  flour.  The 
test  as  made  is  based  on  the  well-known  estimation  of  the  amount  of  protein 
soluble  in  alcohol,  but  at  present  it  cannot  be  said  with  certainty  whether 


382 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  substance  thus  dissolved  from  the  treated  flour  is  identical  with  that 
named  gliadin.  In  the  case  of  the  very  soft  flours  there  is  not  the  same 
production  of  gliadin.  It  is  not  safe  to  generalise  on  so  few  experiments, 
but  so  far  as  they  have  gone  they  point  to  a possible  softening  and  mellowing 
of  very  hard  flours,  without  a coresponding  softening  of  flours  which  are 
already  sufficiently  soft. 

Effect  on  the  Working  Properties  of  the  Flours. — Turning  again  to  the 
table  of  results,  there  is  in  Nos.  I.,  II.  and  III.  a slight  diminution  in  water- 
absorbing power  ; the  same  also  holds  with  Nos.  IV.,  V.  and  VI.  There 
is  very  little  difference  in  Nos.  VII.,  VIII.  and  IX.,  nor  in  Nos.-X.  and  XI. 
In  the  mill-treated  samples,  there  is  an  increase  in  water- absorbing  power 
as  the  result  of  oxidation. 

In  making  baking  tests,  the  water-absorbing  power  of  most  flours  seems 
to  be  slightly  increased.  With  the  very  soft  flours  there  is  no  very  great 
difference  observable  in  their  behaviour  during  fermentation,  which  rather 
bears  out  the  view  that  their  gluten  is  not  further  softened  by  the  process. 
But  in  the  case  of  the  hard  flours,  they  are  found  to  work  more  freely  and 
to  make  a larger  and  bolder,  and  at  the  same  time  better  shaped  loaf.  They 
do  not  show  the  same  evidences  of  being  “ gluten  bound.'' 

While  the  resultant  bread  is  improved  in  colour,  there  is,  in  the  case  of 
the  normally  treated  flour,  no  perceptible  alteration  in  either  odour  or 
flavour.  The  harder  flours  when  treated  make  a rather  moister  and  less 
harsh  loaf. 

The  following  is  a description  of  other  flour-bleaching  investigations  in 
their  chronological  order. 

510.  Flour  Bleiching  by  Electricity,  Balland. — On  comparison  of  samples 
of  the  same  flour,  unbleached  and  bleached  by  treatment  with  electrified 
air,  Balland  finds  the  latter  to  be  distinctly  whiter,  but  with  a less  agreeable 
odour  and  flavour.  The  only  alterations  that  could  be  detected  by  analysis 
were  those  of  the  fatty  matters  and  acidity.  The  fats  became  slightly 
rancid,  less  fluid  and  paler  in  colour.  The  yellow  oil  of  the  wheat  had  been 
oxidised  and  partially  converted  into  white  fatty  acids,  soluble  in  absolute 
alcohol.  The  acidity  of  the  flour  had  increased  from  0*0147  per  cent,  before 
treatment  to  0*0196  per  cent,  after  treatment.  The  examination  of  the 
gluten  and  experiments  on  the  bread-making  properties  of  the  flour 
showed  that  the  electrical  treatment  had  not  only  bleached  the  flour  but 
had  also  “ aged  " it,  with  loss  of  flavour.  {Comptes  Rend.,  1904,  139,  822.) 

No  particulars  are  given  as  to  the  amount  of  bleaching  employed  by 
Balland,  but  it  is  suggested  that  an  excess  of  the  bleaching  agent  had  been 
used. 

511.  Bleaching  Flour,  Shaw. — In  view  of  the  fact  that  oxides  of  nitrogen 
are  the  active  agents  in  most  bleaching  processes,  Shaw  recommends  the 
following  method  of  examination — About  1 kilo  of  flour  is  boiled  for  four 
hours  with  95  per  cent,  alcohol  under  a reflux  condenser.  The  mixture 
is  cooled  and  Altered,  and  the  flour  washed  once  with  alcohol.  The  filtrate 
is  evaporated  nearly  to  dryness,  and  the  residue  extracted  with  a mixture 
of  equal  parts  of  alcohol  and  ether.  This  extract  is  filtered  and  evaporated 
to  a syrup  in  a 4-inch  porcelain  dish.  The  sirupy  mass  is  then  caused  to 
spread  in  a film  over  the  inside  of  the  dish,  and  a drop  of  a solution  of  diphenyl- 
amine  in  sulphuric  acid  is  allowed  to  trail  over  the  film.  With  artificially 
bleached  flours,  the  drop  of  reagent  used  in  this  manner  left  a blue  path, 
whereas  no  colour  was  perceptible  in  cases  of  unbleached  flour.  {Jour.  Arner. 
Chem.  Soc.,  1906,  28,  687.) 

512.  Bleaching,  Fleurent. — ^Fleurent  calculates  that  from  15  to  40  c.c. 


THE  BLEACHING  OF  FLOUR. 


383 


of  nitrogen  peroxide  are  required  to  bleach  1 kilogram  of  flour.  No  differ- 
ence in  chemical  composition  can  be  detected  between  the  bleached  and  the 
original  flour.  In  his  view  the  action  is  confined  to  the  oil  of  the  wheat,  but 
this  action  is  not  a destruction  of  the  colour  by  oxidation.  The  bleaching 
action  coincides  with  a decrease  in  the  iodine  value  of  the  oil,  e.g.  iodine 
values — 

Before  bleaching  of  ..  ..  ..  ..  86*44,  81*70,  86*10 

Became  after  bleaching  . . . . . . . . 80*79,  65*20,  56*70 

By  combination  with  the  nitrogen  peroxide  the  film  of  oil  covering  each 
granule  of  starch  becomes  transparent,  and  enables  the  whiteness  of  the 
starch  to  show  through.  Bleaching  by  age  alone,  on  the  other  hand,  in- 
volves an  oxidation  of  the  oil  and  the  precipitation  of  white,  fixed,  fatty 
acids.  The  action  of  ozone  results  in  an  increase  in  the  iodine  value,  the 
formation  of  volatile  acids,  and  the  constancy  of  the  total  acidity  on  keeping. 
The  following  is  a test  for  bleached  flours,  based  on  the  fixation  of  the  nitro- 
gen peroxide  by  the  oil  : 50  grams  of  flour  are  extracted  by  petroleum 
spirit,  the  extract  is  evaporated  at  a low  temperature,  and  the  oil  is  re- 
dissolved in  3 c.c.  of  amyl  alcohol.  The  solution  is  treated  in  a test-tube 
wdth  1 c.c.  of  alcohol  containing  10  grams  of  caustic  potash  per  litre.  With 
normal  flours  there  is  no  change  in  colouration,  but  with  bleached  flours 
the  colour  changes  to  orange-red,  proportioned  in  intensity  to  the  quantity 
of  nitrogen  fixed.  The  test  will  reveal  the  presence  of  5 per  cent,  of  bleached 
flour  in  a sample.  Bleaching  has  no  action  on  the  enzymes  of  the  flour,  but 
the  oil  shows  less  tendency  to  become  rancid  on  keeping  in  proportion  to 
the  quantity  of  nitrogen  peroxide  fixed.  In  this  sense  the  keeping  properties 
of  the  flour  are  enchanced  by  bleaching.  {Comptes  Rend.,  1906,  142,  180.) 

It  will  be  seen  that  Fleurent  is  of  oj^inion  that  bleaching  is  an  act  of 
nitration  rather  than  of  oxidation. 

513.  Injurious  Effects  of  the  Bleaching  of  Flour,  Ladd. — In  Bulletin 
No.  72  issued  by  the  Experiment  Station  of  North  Dakota,  U.S.A.,  and 
published  by  the  U.S.  Government,  and  also  in  a paper  read  by  Ladd  before 
the  Convention  of  Food  Commissioners  at  Jamestown,  a very  positive  stand 
is  taken  against  the  practice  of  bleaching,  which  is  denounced  as  unessen- 
tial, undesirable,  dangerous,  and  a fraud.  Ladd  enunciates  the  principle 
that  “ the  addition  of  any  unnecessary  chemicals  to  a food  or  beverage 
shall  not  be  deemed  as  justifiable  or  law'ful  in  any  product  until  it  has  been 
clearly  and  satisfactorily  proven  that  the  chemical  or  drug  as  found  in  the 
food,  should  it  there  remain,  is  entirely  harmless,  that  it  does  not  injure 
or  in  any  w’ay  lessen  the  food  value,  and  that  fraud  in  its  use  is  not  thereby 
abetted.  Thus  the  burden  of  proof  falls  as  it  should  upon  those  w4io  w'ould 
add  foreign  and  unessential  chemicals  of  whatsoever  kind  to  any  article 
of  food  or  beverage  intended  for  the  general  consumption  of  the  people  at 
large,  and  not  upon  those  whose  duty  it  is  to  see  that  the  law's  are  enforced.” 
Ladd  contends  that  an  injurious  substance  in  the  form  of  nitrites  is  left 
in  the  flour.  He  further  finds  that  oil  from  w'ell-bleached  flours,  on  being 
stored  for  several  months,  had  a peculiar  pungent  rancid  odour,  and  w'as 
stringy  and  glue-like,  whereas  oil  from  a similar  unbleached  flour  w^as  whole- 
some and  not  rancid.  Ladd  also  expresses  the  opinion  that  the  bleaching 
of  the  flour  has  a marked  injurious  effect  upon  the  gluten,  and  quotes  some 
experiments  to  show  that  from  flour  over-bleached  to  a marked  degree, 
he  w^as  unable  to  obtain  as  much  gluten  as  from  the  same  flour  unbleached. 
On  testing  the  water-absorbing  capacity  of  flours,  Ladd  finds  that  the  same 
flour  when  unbleached  absorbed  69*5  per  cent.,  when  bleached  64  per  cent., 
and  w4ien  over-bleached  60  per  cent.  The  following  is  a summary  of  the 
more  important  of  his  general  conclusions  : — 


384 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


1.  No  one  lias  a right  to  treat  a product  like  flour,  which  forms  the  basis- 
of  our  food  products,  by  a chemical  process  unknown  to  the  consuming 
public. 

2.  Bleaching  is  not  an  improved  milling  process,  but  is  the  introduction 
of  chemical  agents  for  the  purpose  of  treating  the  flour,  which  is  analogous 
to  bleaching  of  fruit  and  other  food  products. 

3.  There  is  employed  in  this  process  of  bleaching  a chemical  agent 
physiologically  very  active. 

6.  Nitrous  anydride,  or  the  salts  resulting  therefrom,  remains  in  the 
flour  after  bleaching. 

7.  The  quality  of  gluten  is  injured  by  bleaching. 

9.  Bleaching  permits  of  using  low  grade  flours.  [Bulletin  No.  72,  Experi- 
mental Station  of  N.  Dakota,  U.S.A.) 

514.  Bleaching  of  Flour,  Wesener  and  Teller. — This  article  is  a reply 
to  the  Bulletin  No.  72  by  Ladd,  abstracted  in  the  previous  paragraph.  The 
writers  first  examined  a number  of  flours  and  other  food-stuffs  for  nitrogen 
trioxide.  The  following  are  a few  of  their  results  : — « 


Per  cent. 

Unbleached  Spring  Patent  Flour  . . . . . . . . 0*00001 

Bleached  ,,  ,,  ,,  . . . . . . . . 0*00005 

Unbleached  Durum  Flour  . . . . . . . . . . 0*000017 

Bleached  ,,  ,,  . . . . . . . . . . 0*00002 

Bread  from  Bleached  Spring  Patent  . . . . . . None 

„ „ „ „ „ 0*0000025 

Corned  Beef  bought  in  the  open  market  . . . . . . 0*00054 

Ham  ,,  ,,  ,,  . . . . . 0*0013 

Rain  Water  . . . . . . . . . . . . . . 0*000171 


The  highest  quantity  in  bread  from  bleached  flour  is  that  given  above, 
which  amounts  to  0*025  part  per  million,  while  ham  contains  about  five 
hundred  times  as  much.  The  U.S.  Dispensatory  (pharmacopoeia)  gives 
the  maximum  safe  dose  of  sodium  nitrite  as  3 grains,  equal  0*19  gram,  which 
is  equivalent  to  0*1  gram  of  nitrogen  trioxide.  In  order  to  consume  this 
quantity  of  nitrogen  trioxide  by  eating  the  bread  from  bleached  flour,  10,000 
one  pound  loaves  would  have  to  be  eaten.  At  the  average  rate  of  bread 
consumption,  an  individual  who  commenced  the  day  he  was  born,  would 
be  55  years  old  before  he  would  thus  have  taken  a single  medicinal  dose  of 
nitrogen  trioxide.  The  writers  do  not  find  the  oil  or  the  gluten  of  flour  to 
be  injured  by  bleaching,  nor  is  there  even  the  slightest  change  in  any  of 
the  other  proximate  principles  of  flour.  Neither  they  nor  any  of  the  bakers 
of  whom  they  have  asked  an  opinion  w'ere  able  to  detect  by  the  senses  of 
taste  or  smell  any  difference  between  bread  baked  from  bleached  and  un- 
bleached flour.  The  writers  recognise  that  the  public  demand  a very  white 
loaf.  Tiiey  point  out  that  dark  flours  have  a higher  food  value,  and  yet  sell 
for  less  in  the  market  because  of  their  dark  colour.  Among  such  flours  they 
cite  that  of  durum  wheat,  the  colour  of  which  is  a strong  yellow.  By  bleach- 
ing sucli  flours,  they  are  made  more  acceptable  to  the  public,  and  thus  the 
food-producing  area  and  capacity  of  the  country  is  enlarged.  Flour  bleach- 
ing does  not  permit  the  substitution  of  an  inferior  article  for  a superior  one, 
but  on  the  contrary,  makes  more  suitable  for  use  articles  which  otherwise 
are  in  a measure  objectionable.  They  disagree  entirely  with  Ladd's  general 
conclusions.  [American  Food  J ournal,  Sept.,  1907.) 

515.  Chemistry  of  the  Bleaching  of  Flour,  Avery. — In  touching  on  the 
history  of  flour  bleaching,  Avery  instances  Bean’s  patent,  2502,  1879,  as 
the  first  to  mention  chlorine  as  a bleaching  agent.  Frichot’s  patent  21971, 
1898,  discloses  the  use  of  nascent  oxygen,  and  recommends  ozone.  Andrews’ 


THE  BLEACHING  OF  FLOUR. 


385 


patent  1661,  1901,  recommends  the  use  of  nitrogen  peroxide.  Alsop’sU.S. 
patent,  759651,  1904,  discloses  the  use  of  air  treated  by  electricity.  The 
general  use  of  bleaching  in  America  dates  from  the  last  named  patent.  A 
commercially  bleached  flour  gave  on  comparison  with  the  untreated  the 
following  results  on  analysis  : — • 

Treated.  Untreated. 

Water  10-88  ..  10-76 

Mineral  Matter  . . . . . . . . . . 0-42  . . 0-42 

Ether  Extract  . . . . . . . . . . 1-03  . . 1 -04 

Nitrogen  . . . . . . . . . . . . 1-82  . . 1-82 

Crude  Fibre  0-32  . . 0-31 

The  treated  flour  contained  0-78  part  per  million  of  nitrite,  calculated 
as  sodium  nitrite. 

Reducing  Efficiency  of  Various  Agents  : — 

Carefully  'purified  oxygen. — ^No  bleaching  effect.  The  bleaching  effect 
ascribed  to  oxygen  is  to  be  attributed  to  traces  of  chlorine,  usually  present 
if  not  most  carefully  purified. 

Ozone  does  not  bleach  flour.  Electrically  prepared  ozone  contains 
nitrogen  peroxide,  by  which  the  bleaching  is  effected. 

Carbon  dioxide  is  without  effect  on  the  colour  of  flour. 

Bromine  bleaches  effectively  ; 4 c.c.  of  bromine  vapour  mixed  with  3 
litres  of  air  will  bleach  a kilo  of  flour.  Excess  causes  the  flour  to  darken. 

Chlorine  behaves  similarly  to  bromine. 

Sulphur  dioxide  bleaches  very  slowly  "and  requires  a large  excess.  Its 
odour  is  very  pronounced  in  flour  bleached  by  its  use. 

Nitrogen  peroxide  bleaches  in  proportion  to  weight  used  a far  greater 
quantity  of  flour  than  any  of  the  other  reagents.  If  3 c.c.  of  nitric  oxide 
gas  be  taken  to  3 litres  of  air,  it  will  efficiently  bleach  a kilo  of  flour.  The 
maximum  bleaching  effect  is  obtained  by  40  c.c.  Excess  injures  the  colour 
of  the  flour.  {Jour.  Amer.  Chem.  Soc.,  1907,  571.) 

This  paper  is  interesting  as  giving  particulars  of  the  bleaching  effect  of 
a number  of  bodies  the  use  of  which  has  been  proposed  for  the  treatment 
of  flour. 

516.  Detection  of  Bleached  Flour,  Alway  and  Gortner. — Ahvay  and 
Gortner  have  devoted  considerable  attention  to  this  problem,  and  And 
that  the  changes  produced  in  flour  by  bleaching  with  nitrogen  peroxide 
are  three  in  number,  viz.  : — • 

1.  The  addition  of  a small  amount  of  nitrates. 

2.  The  addition  of  a small  amount  of  nitrites. 

3.  The  change  of  the  colouring  matter  of  the  fat  or  the  change  in  the  fat 
itself. 

Fleurent  proposes  a test  based  on  the  change  in  the  fat,  but  the  writers 
were  unable  to  distinguish  bleached  from  unbleached  flours  by  this  test. 

Shaw’s  test,  described  in  paragraph  511,  was  found  to  be  tedious  and 
unreliable. 

Griess-Ilosvay  Test. — ^This  was  a test  for  nitrites,  devised  originally 
by  Griess,  and  improved  by  Ilosvay.  The  test  is  so  delicate  that  one  part 
of  nitrous  anhydride,  N2O3,  in  a thousand  millions  parts  of  water  may  be 
detected  by  its  means. 

The  Griess-Ilosvay  Reagent  is  prepared  in  the  following  manner  : For 
solution  No.  I.,  0-5  gram  of  sulphanilic  acid  is  dissolved  by  heat  in  150  c.c. 
of  dilute  (20  per  cent.)  acetic  acid.  Solution  No.  II.,  0-1  gram  of  a-naphthyl- 
amine  is  heated  with  20  c.c.  of  strong  acetic  acid,  the  colourless  solution 
is  poured  off  and  mixed  with  130  c.c.  of  dilute  acetic  acid.  The  two  solu- 
tions are  kept  separate,  and  when  required  for  use  are  mixed  in  equal  pro- 


386 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


portions.  The  mixture  is  not  affected  by  light,  but  should  be  protected 
from  the  air.  This  reagent  produces  a more  or  less  intense  pink  colouration 
in  the  presence  of  nitrous  acid  and  nitrites. 

Mode  of  Testing. — 'The  writers  found  no  unbleached  flour  to  respond 
to  this  test  when  made  with  the  necessary  safeguards  ; but  they  regard 
the  precautions  necessary  as  being  extraordinary.  The  nitrous  acid  present 
in  the  air  of  laboratories  is  sufficient  to  give  a pink  colouration  with  un- 
bleached flours.  The  following  method  of  working  is  therefore  recom- 
mended. A laboratory  table  should  be  fitted  up  in  the  open  air.  The  water 
to  be  used  must  be  tested  by  the  Griess-Ilosvay  reagent  in  order  to  ensure 
the  absence  of  nitrites.  All  apparatus,  and  especially  the  filter  papers 
placed  in  funnels,  are  to  be  washed  with  nitrite-free  water,  and  in  the  case 
of  the  latter  until  the  washings  give  no  reaction  when  tested  for  nitrites. 
Twenty  grams  of  the  flour  to  be  tested,  and  200  c.c.  of  water,  are  to  be  placed 
in  a stoppered  bottle  and  shaken  at  intervals  for  half-an-hour.  The  mixture 
is  allowed  to  settle,  and  a portion  of  the  supernatant  liquid  filtered  through 
a washed  filter.  Ten  c.c.  of  this  filtrate  are  diluted  with  50  c.c.  of  water, 
2 c.c.  of  the  Griess-Ilosvay  reagent  added,  and  heated  in  a water-bath  to 
80°  C.  for  15  minutes.  In  the  absence  of  a pink  colouration,  there  are 
no  nitrites  in  the  flour.  In  the  presence  of  a pink  colour,  a comparison 
is  made  in  Nessler  glasses  with  a solution  of  a known  quantity  of  nitrite 
tested  in  the  same  way.  Tested  in  this  manner,  twenty-one  samples  of 
flour  from  mills  without  bleaching  plant  gave  no  reaction  for  nitrites.  Of 
samples  sent  as  bleached  flours  fifty-six  reacted,  while  two  gave  no  reaction. 
These  two  were  probably  sent  by  mistake,  as  their  colour  gave  no  signs  of 
bleaching. 

From  experiments  made  the  writers  satisfied  themselves  that  bleached 
samples  of  flour  lying  side  by  side  with  unbleached  ones  do  not  impart  any 
nitrous  fumes  or  nitrites  to  the  latter. 

The  average  amount  of  nitrite,  expressed  as  sodium  nitrite,  in  all  the 
bleached  samples  was  6*3  parts  per  million. 

In  a graduated  series  of  tests,  nitric  oxide  with  excess  of  air  was  added 
to  flour  in  measured  quantity.  There  was  a gradual  increase  in  whiteness 
up  to  the  addition  of  125  c.c.  of  gas  to  a kilogram  of  flour  (37*5  of  nitrites  per 
million)  after  which  larger  quantities  of  gas  produced  a less  white  flour. 
With  even  the  maximum  bleaching  effect,  the  odour  of  the  flour  remained 
perfectly  agreeable. 

Action  of  Chlorine  and  Bromine. — ^The  maximum  bleaching  effect  on 
flour  is  produced  by  0*7  gram  of  chlorine  and  1 *6  gram  of  bromine  respectively. 
The  following  test  serves  to  detect  bleaching  by  these  reagents,  with  quan- 
tities not  exceeding  0*035  gram  of  chlorine,  and  0*08  gram  of  bromine  re- 
spectively. Thirty  grams  of  the  flour  are  extracted  with  benzene  and  the 
latter  evaporated.  A small  quantity  of  oil  remains.  A piece  of  copper 
wire  is  heated  in  a bunsen  flame  until  it  no  longer  colours  the  flame  green. 
The  hot  end  of  the  wire  is  dipped  into  the  oil  and  again  brought  into  the 
flame.  If  chlorine  or  bromine  has  been  used  as  a bleaching  agent,  a green 
or  blue  colouration  will  be  produced.  It  is  evident  from  the  above  test 
that  chlorine  and  bromine  are  largely  absorbed  by  the  oil  of  the  flour.  {Jour. 
Amer.  Chem.  Soc.,  1907,  1503.) 

The  present  recognised  tests  for  the  detection  of  bleaching  agents  in 
flour  are  very  fully  described  in  this  paper. 

517.  Bleaching  and  Acidity,  Allway  and  Pinckney. — ^These  chemists 
find,  as  the  result  of  a number  of  tests,  that  commercial  bleaching  does  not 
increase  the  acidity  of  flours.  The  injurious  effects  attributed  to  the  use  of 
nitrogen  peroxide  are  the  result  not  of  ordinary  but  of  over-treatment.  As 


THE  BLEACHING  OF  FLOUR.  387 

such  over-treatment  at  the  same  time  unfavourably  affects  the  colour 
it  is  not  met  with  commercially.  {Jour.  Amer.  Chem.  Soc.,  1908,  81.) 

518.  Flour  Bleaching,  Snyder. — very  systematic  exposition  of  the 
whole  subject  of  flour  bleaching  is  contained  in  a bulletin  issued  by  the 
University  of  Minnesota  in  1908.  The  writer,  Snyder,  regards  the  bleaching 
of  flour  as  a natural  process,  and  introduces  his  subject  by  a reference  to — 

The  Colouring  Material  of  Flour. — ^The  composition  of  the  colouring 
matter  of  wheat  has  never  been  determined,  because  it  cannot  be  separated 
in  a pure  state  from  the  fat  and  gluten  with  which  it  is  mechanically  associ- 
ated. It  is  soluble  in  ether,  and  in  flour  analyses  it  forms  one  of  the  well 
known  impurities  of  the  “ ether  extract or  “ crude  fat.'"  When  the  gluten 
is  obtained  mechanically,  by  washing  the  dough,  it  is  tinged  yellow  with 
the  natural  colouring  matter  of  the  flour. 

Avery  has  suggested  that  the  colouring  matter  of  flour  is  a nitrogenous 
compound  containing  an  amhno  radical.  In  Bulletin  No.  85  of  this  station 
it  was  suggested  that  the  colouring  matter  was  a nitrogenous  compound. 
Other  investigators  believe  it  is  a non-nitrogenous  body  akin  to  xanthophyll 
and  carotin,  the  natural  yellow  pigments  of  plants.  It  has  certain  char- 
acteristics of  carotin  as  capability  of  being  decolourised  by  heat,  light  and 
chemical  reagents.  Whatever  the  composition  of  the  colouring  matter 
of  wheat  may  prove  to  be,  it  is  not  a stable  compound.  After  flour  has 
undergone  natural  bleaching  various  tints  and  shades  of  colour  are 
developed,  particularly  of  grey  and  light  yellow.  These  various  shades 
and  tints  may  serve  as  an  index  of  bread-making  value,  but  it  is  not  possible 
from  the  colour  alone  of  either  freshly  milled  or  cured  flour  to  determine 
bread-making  value.  Flours  that  are  pure  white,  or  tinged  slightly  yellow, 
have  the  highest  bread-making  value.  A dark  grey  or  slaty  colour  is  usually 
an  index  of  poor  bread-making  qualities.  Flours  of  poor  colour  when 
milled,  often  develop  even  more  undesirable  tints  by  storage.  If  the 
flours  are  not  well  milled  the  branny  particles  become  discoloured 
through  oxidation  of  the  cellulose  and  the  flours  then  show  black  specks. 
Hence  it  is  that  only  well-milled  flours  from  sound  wheat  are  capable  of 
being  improved  by  storage. 

Bleaching  Agents. — Of  the  various  methods  proposed  for  the  bleaching 
of  flour  practically  the  only  one  that  has  survived  the  experimental  stage 
is  the  nitrogen  peroxide  process,  in  which  the  bleaching  reagent  is  produced 
directly  from  the  union  of  the  nitrogen  and  oxygen  of  the  air  by  electrical 
action. 

In  the  bleaching  of  flour  the  unstable  yellow  colouring  matter  is  acted 
upon  by  the  nitrogen  peroxide,  and  from  a study  of  the  properties  of 
nitrogen  peroxide  it  would  appear  to  be  an  oxidation  change.  As  will  be 
shown  later,  this  change,  if  it  be  oxidation,  does  not  extend  to  the  other 
constituents  of  the  flour  as  fat  and  gluten,  inasmuch  as  flour  bleaching 
as  now  practised  leaves  these  and  other  constituents  unaltered  as  far  as 
chemical  tests  are  capable  of  determining.  As  a result  of  the  nitrogen 
peroxide  treatment,  some  nitrogen  trioxide  reacting  material  is  left  in  the 
flour.  For  convenience  it  is  assumed  to  be  a nitrite,  but  cannot  be  a 
mineral  nitrite  like  that  of  potassium  or  sodium,  as  it  has  entirely  different 
properties.  That  the  material  is  present  largely  in  physical  form  can 
be  shown  by  heating  bleached  flour  to  a temperature  of  95®  C.  The  flour 
will  then  be  found  free  from  nitrite  reacting  material  provided  it  has 
been  heated  out  of  contact  with  a gas  flame  or  combustion  products  that 
yield  nitrites,  or  the  flour  was  made  from  wheat  free  from  mineral 
nitrates  or  nitrites. 

Fat  of  Bleached  and  Unbleached  Flour. — ^When  the  fat  of  flour  is  obtained 


388 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


by  the  official  method  of  analysis,  the  colouring  matter,  lecithin,  chlorophyll 
residue  products  and  other  substances  are  recovered  as  mechanical  im- 
purities mixed  with  the  fat.  The  chemist  uses  the  term  ‘‘  crude  fat ""  or 
“ ether  extract because  of  these  known  impurities.  Some  of  the  impurities 
are  nitrogenous  and  some  are  non-nitrogenous  compounds.  Hence  any 
change  produced  by  bleaching,  in  the  colour  of  the  fat  cannot  be  said 
to  denote  change  in  the  composition,  when  it  is  known  that  the  colour 
is  one  of  the  impurities  of  the  fat. 

In  the  bleaching  of  flour  it  has  been  suggested  that  a slight  oxidation 
of  the  fat  is  one  of  the  possible  chemical  changes  which  may  occur,  since 
nitrogen  peroxide,  a carrier  of  atmospheric  oxygen,  is  employed.  Should 
any  appreciable  oxidation  of  the  fat  take  place  during  bleaching,  the  fat 
of  the  bleached  flour  would  have  different  properties  from  that  of  the  un- 
bleached flour.  Any  such  change  in  the  fat  would  necessarily  affect  such 
determinations  as  those  of  the  iodine  absorption  number  and  the  heat  of 
combustion.  Four  typical  samples  of  flour  (two  bleached  and  two  un- 
bleached) were  selected  for  the  purpose  of  extracting  the  fat  in  quantity. 
The  flours  were  dried  in  such  a way  as  to  prevent  oxidation,  and  the  iodine 
number  was  determined.  The  following  results  were  obtained  : — 

Iodine 

Absorption 

Number 

Patent  flour,  unbleached.  No.  1 . . . . . . . . . . 102*9 

Same  flour,  bleached,  No.  2 . . . . . . . . . . 103*7 

Patent  flour,  unbleached  . . . . . . . . . . . . 101*1 

Same  flour,  bleached  . . . . . . . . . . . . 102*6 

Practically  no  greater  differences  were  observed  between  the  fat  of  the 
bleached  and  unbleached  flours  than  between  duplicate  analyses  of  the  same 
sample.  As  far  as  the  iodine  number  of  the  fat  is  concerned  no  appreciable 
difference  was  observed  between’thosebf  the  bleached  and  unbleached  flours. 

It  has  been  suggested  that  the  nitrogen  peroxide  chemically  unites 
with  the  fat,  resulting  in  the  production  of  nitrogenous  compounds.  Should 
any  such  change  occur  it  would  affect  the  nitrogen  content  of  the  product, 
and  the  fat  from  the  bleached  flour  should  show  a higher  nitrogen  content. 
A number  of  investigators  have  shown  that  lecithin,  a nitrogenous  com- 
pound soluble  in  ether,  is  present  as  an  impurity  in  the  ether  extract  or 
crude  fat  obtained  in  the  analysis  of  flour.  Hence  it  is,  wheat  fat  as  ordin- 
arily obtained  contains  nitrogenous  compounds,  rendering  it  exceedingly 
difficult  if  not  impossible  to  separate  from  that  naturally  present  any  new 
nitrogenous  compound  that  may  possibly  be  formed  during  the  process- 
of  bleaching.  The  ether  extract  or  crude  fat  of  three  samples  of  unbleached 
flour  was  obtained  in  quantity  by  extraction  with  one  of  the  best  grades- 
of  commercial  ether.  Also  the  ether  was  purified  as  directed  in  the  official 
method  of  analysis  and  the  nitrogen  content  of  the  crude  fat  extracted 
with  tlie  purified  ether  by  the  official  method  was  determined. 


Nitrogen  Content  of  Fat  of  Unbleached  Flours. 


Commercial 

Purified 

Saini)le. 

Ether. 

Ether. 

1 

0*887 

0*873 

2 

0*919 

0*901 

3 .' 

. . 0*931 

0*942 

It  is  to  be  noted  that  approximately  0*9  per  cent,  of  nitrogen  was  found 
present  as  a natural  constituent  of  wheat  fat.  There  was  no  difference 
in  the  results  wliether  the  ordinary  or  the  modified  Kjeldahl  method  was 
used  for  determining  tlie  nitrogen  content  of  tlie  fat.  In  determinations 
(qualitative  or  quantitative)  of  the  nitrogen  content  of  the  fat  of  bleached 


THE  BLEACHING  OF  FLOUR. 


389 


flour,  the  nitrogen  that  is  naturally  present  must  be  recognised,  and  the 
presence  of  nitrogenous  compounds  in  the  fat  cannot  be  ascribed  to  bleach- 
ing. The  nitrogen  content  of  the  fat  of  three  samples  of  flour  before  and 
after  bleaching  was  determined  with  the  following  results  : — • 

Nitrogen  of  Fat. 

Bleached.  Unbleached. 

Flour  A 0-866  0-887 

Flour  B 0-930  0-919 

Flour  C 0-927  0-931 

Duplicate  determinations  w^ere  made  and  no  greater  differences  in  the 
nitrogen  content  of  the  fats  from  bleached  and  unbleached  flours  were  found 
than  between  duplicate  analyses  of  the  same  sample.  The  quantitative 
determinations  of  nitrogen  showed  the  bleaching  of  the  flour  did  not  increase 
the  nitrogen  content  of  the  fat. 

The  heat  of  combustion  of  the  fats  was  also  determined  in  a Berthelot 
calorimeter  and  practically  the  same  caloric  value  was  obtained  for  the  fat 
from  the  bleached  as  from  the  unbleached  flour.  The  differences  in  the 
heats  of  combustion  were  no  greater  than  in  the  case  of  duplicate  determina- 
tions on  the  same  sample.  If  any  oxidation  or  nitration  had  taken  place 
during  the  process  of  electrical  bleaching,  it  would  have  manifested  itself 
in  lowering  the  heat  of  combustion.  Neither  the  iodine  number,  nitrogen 
content,  nor  heat  of  combustion  shows  any  change  to  have  occurred,  or  that 
the  fats  from  bleached  and  unbleached  flours  differ. 

The  Qlutens  of  Bleached  and  Unbleached  Flours. — Snyder  finds  the  gluten 
of  flour  to  be  unchanged  by  the  act  of  bleaching,  except  in  the  direction  of 
colour.  He  further  finds  that  the  quantity  and  composition  of  the  gliadin 
is  unaffected  by  the  bleaching  process. 

It  would  not  be  possible  for  nitro-  or  nitrosyl-compounds  to  be  formed 
during  bleaching,  because  not  enough  nitrite  or  nitrate  reacting  materials 
are  present  to  permit  such  reactions  taking  place.  Furthermore  nitrous 
and  nitric  acids,  if  present  in  sufficient  amounts  to  cause  a reaction,  would 
produce  yellow  coloured  products  in  accord  with  the  well  known  xantho- 
protein  reaction  of  Fourcroy  and  Vanquelin,  and  consequently  the  flour 
would  have  a yellow  tint.  Such  a procedure  would  be  directly  opposite 
to  bleaching,  and  in  that  event  the  nitrogen  peroxide  would  act  as  a stain 
and  not  as  a decolourising  reagent.  The  trace  of  nitrogen  peroxide  em- 
ployed in  the  bleaching  of  flour  cannot  be  regarded  in  any  way  as  a dye 
or  stain,  as  it  does  not  unite  chemically  with  either  the  fat  or  the  gluten,  or 
form  a coating  over  the  surface  of  the  flour  particles.  Its  action  upon 
the  colouring  matter  of  flour  is  similar  to  the  change  that  takes  place  natur- 
ally when  flour  is  cured  and  bleached  by  storage. 

Physical  Absorption  of  Gas  by  Flour. — Since  analyses  of  the  fat  and 
gluten  of  bleached  flour  indicated  that  no  chemical  combination  had  taken 
place  with  the  trace  of  nitrogen  peroxide  used  in  the  bleaching  mixture, 
experiments  were  undertaken  to  determine  whether  the  nitrite  reacting 
material  in  the  bleaching  gas  could  all  be  accounted  for  as  absorbed  in  the 
flour.  From  these  experiments  Snyder  arrived  at  the  following  con- 
clusion. The  nitrite  reacting  material  in  flour  appears  to  be  in  physical 
rather  than  chemical  combination.  When  the  flour  is  heated,  the  nitrite 
reacting  material  imparted  by  bleaching  is  expelled.  All  of  the  nitrite 
reacting  material  in  the  gas  employed  for  bleaching  can  be  accounted  for 
as  soluble  and  volatile  nitrites  in  the  flour  and  in  the  air  surrounding  the 
flour,  leaving  no  nitrite  reacting  material  to  chemically  combine  with  the 
fat  or  gluten.  When  the  bleaching  gas  w^as  brought  in  contact  with  pure 
sand,  with  which  it  cannot  unite  chemically,  the  same  amounts  of  nitrites 
were  absorbed  as  in  the  case  of  flour. 


390 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Loss  of  Nitrites  in  Bread-Making. — Bread  made  from  bleached  flours 
containing  0*00004  per  cent,  nitrogen  as  nitrites  and  baked  out  of  contact 
with  combustion  of  gases  gives  no  reaction  for  nitrites.  Bread  made  from 
unbleached  flour  and  baked  in  a gas  oven  in  which  there  is  direct  connection 
between  the  combustion  chamber  and  the  oven  shows  appreciable  amounts 
of  nitrites  formed  from  combustion  of  the  gas.  When  the  bread  was  pro- 
perly made  and  baked  in  an  electric  oven  there  was  no  reaction  for  nitrites 
from  either  the  bleached  or  unbleached  flours,  that  is  provided  the  flour 
itself  was  free  from  nitrite  and  nitrate  reacting  material  except  that  imparted 
by  the  bleaching  gas.  Snyder  regards  the  nitrite  of  bleached  flour  as  being 
more  probably  ammonium  nitrite  than  that  of  either  sodium  or  potassium. 

Influence  of  Bleaching  of  Flour  upon  the  Digestibility  of  Bread. — In  order 
to  determine  the  influence  which  commercially  bleached  flour  may  exert 
upon  the  digestibility  of  bread  a series  of  digestion  experiments  was  under- 
taken to  determine  the  digestibility  of  bread  made  from  bleached  and  un- 
bleached flour  milled  from  the  same  wheat.  In  all,  fifteen  digestion  experi- 
ments with  men  were  made.  The  ration  consisted  of  bread  and  milk  and  the 
general  plan  of  the  experiments  was  as  follows.  Samples  of  bleached  and  un- 
bleached flours  and  of  the  wheat  from  which  the  flours  were  made  were 
drawn  from  a large  commercial  mill.  Digestion  experiments  were  made 
with  bread  baked  from  the  bleached  and  the  unbleached  flours.  Some 
of  the  wheat  was  then  milled  in  the  experimental  mill  of  the  Minnesota 
Experiment  Station.  One-half  of  the  flour  was  bleached,  and  digestion 
experiments  were  made  with  bread  from  this  bleached  and  unbleached 
flour  prepared  under  chemical  control.  The  results  of  these  five  series  of 
digestion  experiments  are  given  in  the  table  on  page  391. 

In  one  of  the  trials  or  series,  the  nutrients  of  the  bread  made  from  the 
unbleached  flour  was  found  to  have  a slightly  higher  digestibility  than  the 
bread  made  from  the  same  flour  that  had  been  bleached,  while  in  another 
series  the  bread  from  the  bleached  flour  was  somewhat  more  completely 
digested.  The  difference  in  digestibility  of  the  nutrients  of  the  bread 
made  from  the  bleached  and  unbleached  flours  was  too  small  to  be  attributed 
to  the  treatment  the  flour  had  received.  The  average  of  the  two  series 
shows  the  bread  made  from  both  the  bleached  and  the  unbleached  flours 
to  have  the  same  degree  of  digestibility,  and  that  the  process  of  bleaching 
had  no  influence  upon  the  digestibility  or  nutritive  quality  of  the  flour. 
The  bread  for  these  experiments  was  baked  in  an  ordinary  cook  stove  heated 
by  coal,  and  all  the  products  of  combustion  of  the  fuel  were  excluded  from 
the  baking  chamber.  The  bread  both  from  the  bleached  and  unbleached 
flour  gave  no  reaction  for  nitrites,  the  nitrous  acid  products  formed  during 
the  bleaching  of  the  flour,  and  present  to  the  extent  of  0 *00004  gram  of 
nitrogen  determined  as  nitrites  per  100  grams  of  flour,  being  entirely  dis- 
pelled during  the  process  of  baking. 

Digestion  Experiments  with  Pepsin  Solution. — Digestion  trials  were  made 
with  bleached  and  unbleached  flours  in  acid  pepsin  solution.  The  flours- 
used  contained  2*04  per  cent,  nitrogen.  The  insoluble  nitrogen  obtained 
after  digestion  with  pepsin  was  found  to  be  as  follows  : — 


Trial  No. 

Bleached  Flour. 
Per  cent. 

Unbleached  Flour., 
Per  cent. 

1 . . 

0*392 

0*378 

2 .t 



0*343 

0*356 

Average 

• • 

0*367 

0*367 

It  is  to  be  noted  that  the  differences  between  the  duplicate  trials  of  the; 
same  sample  are  as  great  as  between  the  two  samples  of  flour  tested. 


THE  BLEACHING  OF  FLOUR.  391 


Digestibility  of  Nutrients. 


Protein 
per  cent. 

Carbo- 
hydrates 
per  cent. 

Available 

I Calories. 

Trial  I.  Bread  from  Bleached  Flour. 

Man  1 

85-74 

96-96 

91-67 

Man  2 

84-53 

97-52 

90-62 

i\Ian  3 

84-96 

97-28 

90-35 

Average 

85-08 

97-25 

90-88 

Trial  11.  Bread  from  Unbleached  Flour. 

Man  1 

86-97 

98-47 

91-46 

Man  2 

87-93 

98-14 

90-89 

.Alan  3 . . 

87-63 

98-28 

91-35 

Average 

87-51 

98-29 

91-23 

Trial  III.  Bread  from  Unbleached  Flour. 

Alan  1 

91-76 

99-02 

93-87 

Alan  2 

92-14 

98-08 

94-97 

Alan  3 

91-67 

99-08 

95-09 

Average 

91-86 

98-73 

94-64 

Trial  IV.  Bread  made  from  Bleached  Flour. 

Alan  1 

92-04 

99-07 

94-41 

Man  2 

93-24 

98-89 

95-49 

Alan  3 

93-00 

98-88 

95-66 

Average  . . 

92-76 

98-95 

95-19 

Trial  V.  Bread  from  Unbleached  Flour 

with  Nitrites. 

Alan  1 

93-56 

99-14 

95-21 

Man  2 

93-98 

99-19 

95-76 

Alan  3 

95-96 

99.18 

— 

Average 

94-50 

99-17 

95*43 

As  far  as  digestibility  in  the  acid  pepsin  solution  was  concerned  no 
difference  whatever  was  found  in  the  digestibility  of  the  bleached  and 
the  unbleached  flours. 

Are  Flours  Bleached  with  Minute  Amounts  of  Nitrogen  Peroxide  Injurious 
to  Health  ? — This  is  a question  that  can  well  be  raised,  because  if  the  bleach- 
ing leaves  any  material  in  the  bread  that  is  injurious  to  health  the  practice 
should  be  discontinued  and  condemned.  The  form  in  which  the  flour  is 
consumed  as  food,  or  the  flnished  food  product,  is  what  should  be  considered 
in  answering  this  question.  Flour  is  never  eaten  in  the  raw  state,  but  in 
the  process  of  bread-making,  cake-making,  and  indeed  in  aU  the  various 
ways  it  is  prepared  for  food  it  is  always  subjected  to  the  action  of  heat.  As 
previously  stated,  when  flour  is  warmed  out  of  contact  with  combustion 
gases  the  nitrite  reacting  material  imparted  during  bleaching  is  removed, 
and  the  bread  and  other  articles  made  from  the  flour  give  no  reaction  for 
nitritciS  imparted  by  the  bleaching  gas.  Since  the  material  used  in  the 
bleaching  of  flour  is  expelled  in  the  preparation  of  the  food,  there  remains 
no  question  for  physiological  consideration.  But  since  breads  made  from 


392 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


bleached  and  unbleached  flour  give  practically  like  amounts  of  nitrite  react- 
ing material  when  baked  in  gas,  gasoline  or  kerosene  ovens,  it  would  seem 
that  the  broader  question  could  well  be  raised  : is  the  use  of  gas  and  liquid 
fuels  for  the  preparation  of  foods,  where  the  food  comes  in  direct  contact 
with  the  products  of  combustion,  injurious  to  health  1 This  broader  ques- 
tion lies  outside  the  province  of  the  chemist,  and  also  the  scope  of  the  present 
work.  Snyder,  however,  points  out  that  when  breathing  the  air  of  a room 
it  not  infrequently  happens  that  a person  inhales  during  a day  more  nitrogen 
trioxide  than  is  present  in  a pound  of  bleached  flour  in  the  raw  state.  He 
further  points  out  that  various  other  articles  of  food  contain  nitrites  in 
considerably  greater  quantity  than  does  bleached  flour.  If  the  presence  of 
nitrites  generally  in  these  minute  traces  is  to  be  regarded  as  injurious  to 
health,  then  the  national  food  menu  must  be  materially  curtailed. 

Use  of  Chemicals  in  Preparation  of  Foods. — The  principle  of  the  use  of 
chemical  reagents  in  the  manufacture  and  refining  of  foods  is  recognised 
in  the  rules  and  regulations  for  the  enforcement  of  the  National  Food  and 
Drugs  Act.  Circular  No.  21,  U.S.  Department  of  Agriculture,  Office  of  the 
Secretary,  Regulation  No.  II,  states  : “ Substances  properly  used  in  the 
preparation  of  food  products  for  clarifying  or  refining  and  eliminated  in 
further  process  of  manufacture  are  exempt.  There  is  no  substance  or 
material  used  in  the  manufacture  of  food  products  that  is  as  completely 
eliminated  from  the  finished  product  (bread)  as  is  the  nitrogen  peroxide 
and  its  products,  used  in  the  bleaching  or  refining  of  flour.  In  the  manu- 
facture of  sugar,  sulphur  in  the  form  of  sulphur  dioxide  gas  is  used  for  bleach- 
ing purposes.  Lime  is  employed  later  in  the  process  for  neutralising  the 
sulphurous  and  sulphuric  acids  formed  and  for  producing  insoluble  pro- 
ducts which  are  later  removed  by  filtration.  The  last  traces  of  the  sulphur, 
however,  are  not  entirely  removed,  and  careful  analysis  of  commercial 
samples  of  granulated  sugar  after  combustion  in  a calorimeter  have  shown 
•0098  per  cent,  of  total  sulphur.  On  a percentage  basis  this  is  nearly  fifty 
times  more  than  the  total  nitrate  and  nitrite  products  retained  in  flour, 
bleached  by  the  use  of  nitrogen  peroxide.  Furthermore  sugar  is  used 
directly  as  food  without  any  of  the  sulphur  being  volatilised.  Notwith- 
standing the  presence  of  this  trace  of  sulphur,  granulated  sugar  is  practi- 
cally pure,  as  it  is  unacted  upon  by  the  sulphur.  The  sulphur  acts  only 
upon  the  colouring  matter  and  not  upon  the  sugar.  However,  a much 
larger  amount  of  it  is  used  than  of  nitrogen  peroxide  in  the  bleaching  of 
flour.  With  large  amounts  of  sulphurous  and  sulphuric  acid,  chemical 
reaction  takes  place  with  sugar,  but  the  little  used  as  a bleaching  reagent 
fails  to  produce  such  a change.  In  the  same  way  the  small  amount  of 
nitrogen  peroxide  used  in  flour  bleaching  acts  upon  the  colouring  matter 
of  the  flour  without  uniting  with  any  of  its  constituents.  A large  amount 
of  gas,  however,  would  produce  chemical  changes,  as  would  a large  amount 
of  sulphur  dioxide  acting  upon  granulated  sugar.  Sugar  is  a food  consist- 
ing of  only  one  nutrient.  In  order  to  refine  and  improve  it  the  colouring 
matter  is  removed  by  bleaching.  This  bleaching  is  done  Avithout 
affecting  the  composition.  Flour  is  a food  consisting  of  several  nutrients, 
and  the  colouring  material  is  bleached  by  a trace  of  nitrogen  peroxide, 
without  otherwise  affecting  the  composition.  Snyder  concludes  his  paper 
by  the  statement  that  in  bread-making  tests  of  commercially  bleached 
flours  no  difference  whatever  was  observed  between  the  breads  produced 
from  the  bleached  and  tlie  unbleached  flours  milled  from  the  same  wheats, 
except  that  the  bleached  flours  produced  a whiter  bread  and  also  shoAved  a 
tendency  to  produce  larger  sized  loaves.  Bleaching  of  the  flour  did  not 
impart  any  odour  or  taste  to  tlie  bread  or  leave  in  it  any  residue. 

The  bleaching  of  flour  enables  the  miller  to  manufacture  a more  uniform 


THE  BLEACHING  OF  FLOUR. 


393 


product  and  to  place  his  flour  directly  on  the  market  without  necessitating 
its  undergoing  bleaching  and  curing  in  storage.  No  difference  whatever 
was  observed  between  the  naturally  bleached  flours  and  those  bleached  by 
the  electrical  process  except  that  the  latter  contained  traces  of  nitrite  react- 
ing materials  which  were  expelled  during  bread-making.  (University  of 
Minnesota  Agric.  Expt.  Station.  Bull.,  No.  111). 

519.  Bleached  Flour,  U.S.  Board  of  Food  Inspection  Decision. — By  their 
decision,  No.  100,  the  United  States  Board  of  Food  Inspection  has  given 
it  as  their  unanimous  opinion  that  flour  bleached  with  nitrogen  peroxide 
is  an  adulterated  product  under  the  Food  and  Drugs  Act,  1906  ; and  also 
that  no  statement  on  the  label  can  bring  such  bleached  flour  within  the 
law,  and  that  such  flour  cannot  legally  be  made  or  sold  in  the  District  of 
Columbia  or  in  the  Territories,  or  be  transported  or  sold  in  interstate  com- 
merce. (Jour.  Soc.  Chem.  Ind.,  1909,  157). 

This  decision  has  since  been  upheld  in  American  law-courts  of  first 
instance.  At  the  moment  of  writing,  the  matter  is  being  carried  to  the  higher 
courts  by  way  of  appeal. 

520.  Bleached  Flour,  Additional  Test  for,  Weil. — Weil  finds  that  on 
subjecting  flours  to  the  action  of  the  Griess-Ilosvay  reagent,  there  are 
certain  unbleached  flours  which  give  a colouration  with  the  reagent.  For 
instance,  flour  from  some  Russian  wheat  gave  a colouration  at  once  ; La 
Plata  and  Kansas  flours  reacted  after  standing  for  5 minutes,  Swedish 
flour  after  9 minutes,  and  German  flour  after  20  minutes.  These  flours, 
therefore,  contain  normally  a small  quantity  of  nitrous  acid  or  some 
other  substance  which  gives  rise  to  the  action.  Weil  recommends  the 
following  test  for  ascertaining  whether  a flour  has  been  bleached.  A quan- 
tity of  the  flour  is  placed  in  a closed  vessel  through  which  a current  of  hydro- 
gen sulphide  is  passed  for  an  hour  ; the  colour  of  the  flour  thus  treated  is 
then  compared  with  that  of  the  original  sample.  Unbleached  flour  exhibits 
no  difference  in  colour  after  treatment  with  hydrogen  sulphide,  but  bleached 
flour  becomes  darker,  acquiring  the  original  colour  it  possessed  before  bleach- 
ing. (Chew,.  Zeit.,  1909,  33,  29.) 

521.  Action  at  Law  by  Flour  Oxidising  Co.,  Ltd.  v,  J.  and  R.  Hutchinson. — 

This  was  an  action  brought  in  March,  1909,  in  the  Chancery  Division  of 
the  High  Court  of  Justice,  England,  before  Mr.  Justice  Warrington.  The 
plaintiffs  are  the  owners  of  Andrews’  Patent,  1661  of  1901,  before  referred  to, 
paragraph  507,  and  the  action  was  one  for  infringement  of  the  Patent 
by  the  defendants.  It  was  alleged  by  the  defendants  that  the  Patent  was 
not  useful  for  the  purpose  specified,  in  that  the  baking  qualities  of  bread 
made  from  bleached  flour  were  not  improved,  that  such  bread  was  less 
digestible,  and  that  the  treated  flour  was  deteriorated  by  the  introduction 
or  formation  therein  of  a toxic  poisonous  substance. 

In  support  of  this  allegation,  evidence  was  given  by  Ladd,  who  stated 
that  he  was  Professor  of  Chemistry  in  the  N.  Dakota  Agricultural  College, 
and  Food  and  Drug  Commissioner  of  the  State  of  N.  Dakota,  U.S.A.,  and 
deposed  as  follows  : The  sodium  nitrite  in  commercial  samples  of  bleached 
flour  varied  from  1 to  15  parts  per  million.  Deterioration  in  gluten  was 
found  in  the  majority  of  such  samples.  Germ  oil  contained  nitrogenous 
ingredients.  There  were  small  amounts  of  other  oils  in  the  flour.  The 
oil  extracted  from  well-made  patent  flour  was  free  from  nitrogen.  After 
treatment  the  oil  was  less  absorptive  of  iodine,  and  its  refractive  index  was 
changed — ^the  oil  when  tested  for  nitrogen  showed  it  had  been  nitrated. 
The  nitration  of  the  oil  injured  the  quality  of  the  flour.  It  became  less 
digestible  and  contained  an  ingredient  foreign  to  flour.  The  witness  then 


394 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gave  details  of  experiments  which  were  described  in  the  Chemical  News 
of  March  5,  12  and  19,  1909,  from  which  the  following  are  extracts:  there 
were  several  kinds  of  experiments  made,  first  experiments  with  bleached 
flour  to  determine  the  amount  of  nitrous  acid  or  nitrites  present  therein  ; 
second,  experiments  to  determine  the  amount  of  nitrites  calculated  as  sodium 
nitrite,  present  in  bread  produced  from  commercially  bleached  flour  ; third, 
experiments  as  to  the  effect  of  bleaching  on  digestion  ; fourth,  experiments 
as  to  the  effect  of  bleaching  on  digestion  of  gluten  and  bread.  From  these 
experiments  the  following  conclusions  were  derived  : I.  That  nitrous  and 
nitric  acid  are  two  of  the  constituents  formed  from  the  bleaching  of  flour 
with  nitrogen  peroxide.  II.  The  nitrites  and  nitrates,  or  nitrite  and  nitrate 
reacting  material,  are  among  the  products  formed  in  the  flour.  III.  That 
bread  as  baked  in  the  home  by  the  domestic  method  will  contain  from  one- 
third  to  one-half  of  the  nitrite  reacting  material  found  in  the  flour.  IV. 
Oil  properly  extracted  and  purified  from  unbleached  patent  flour  contains 
no  nitrogen.  V.  Oil  extracted  from  bleached  flour  and  purified  by  the 
same  methods  gives  a strong  reaction  for  nitrogen,  thus  confirming  the 
statement  made  by  Lewkowitsch.  VI.  Oils  from  unbleached  flours  have 
an  iodine  absorption  number  of  101  or  more,  while  the  iodine  absorption 
number  for  oils  from  bleached  flours,  when  properly  purified,  will  have  a 
lower  iodine  number  in  proportion  to  the  amount  of  bleaching.  Vll.  The 
difference  in  the  iodine  number  and  the  difference  in  the  nitrogen  contents 
of  the  oils  show  that  the  bleaching  agent  has  acted  upon  the  fat  of  the 
flour.  VIII.  Flours  aged  for  nine  months  showed  no  reduction  in  iodine 
number,  while  the  same  flour  bleached  and  aged  for  the  same  length  of 
time  showed  a reduction  of  17*1  points,  indicating  that  the  artificial  bleach- 
ing is  not  the  same  as  the  natural  ageing  of  flours.  IX.  The  proportion 
of  nitrates  in  the  bread  increases  as  the  nitrites  decrease.  X.  The  method 
of  baking  will  determine  to  what  extent  the  nitrates  are  changed  or  elimin- 
ated in  the  bread.  XI.  Artificial  digestion  experiments  with  pepsin  solu- 
tions show  that  the  gluten  from  unbleached  flour  was  digested  in  4 hours 
and  57  minutes  ; while,  under  the  same  conditions,  the  gluten  from 
the  bleached  flour  was  digested  in  8 hours  and  40  minutes.  XII.  The 
baked  gluten  from  the  bleached  and  unbleached  flours  showed  similar 
variations  but  not  so  wide,  the  time  of  digestion  being  much  less  ; the 
same  is  true  for  the  bread  made  from  such  flours.  XIH.  In  pancreatic 
digestion  the  gluten  digested  in  3*19  hours  from  bleached  flour,  and  in  2*31 
hours  from  unbleached  flour.  The  time  of  digestion  in  pancreatic  solutions 
of  the  baked  gluten  and  of  the  bread  was  in  favour  of  the  unbleached  pro- 
duct. XIV.  The  experiments  made  with  the  keeping  quality  of  bread 
made  from  bleached  and  unbleached  flour  demonstrated  the  antiseptic 
effect  of  the  bleaching  agent.  XV.  It  has  been  demonstrated  that  when 
the  diazo  or  like  action  took  place,  the  acid  acted  upon  the  gluten  of  the 
flour,  changing  its  composition  so  that  nitrogen  gas  was  given  off  when  the 
flour  was  treated  with  an  acid.  XVI.  The  fact  that  the  xanthoproteic 
reaction  takes  place  demonstrates  further  that  the  bleaching  agent  has 
acted  upon  the  gluten  or  the  protein  of  the  flour. 

There  were  further  experiments  as  to  the  effect  of  bleached  flour  on 
rabbits.  Alcoholic  extracts  of  unbleached  and  commercially  bleached 
flours  were  prepared  and  administered  to  rabbits  ; and  as  a check,  physio 
logical  salt  solutions  containing  alcohol,  ranging  from  7 to  16  per  cent., 
were  administered  to  other  rabbits.  The  following  is  a summary  of  the 
results  obtained.  I.  There  is  produced  in  flour,  as  the  result  of  artificial 
bleaching,  toxic  bodies.  H.  Experiments  previously  reported  indicate 
the  possibility  of  a diazo  reaction  where  flour  has  been  subjected  to  bleach- 
ing, especially  when  the  bleaching  has  been  carried  to  a considerable  extent. 


THE  BLEACHING  OF  FLOUR. 


395 


III.  The  fact  that  the  xanthoprotein  reaction  takes  place  demonstrates 
that  the  bleaching  agent  has  acted  upon  the  gluten  or  the  protein  of  the 
flour.  IV.  Alcoholic  extracts  prepared  from  unbleached  flour  and  fed  to 
rabbits  did  not  affect  them.  V.  Alcoholic  extracts  prepared  in  the  same 
manner  from  commercially  bleached  flour  and  fed  to  rabbits  in  the  same 
way  caused  their  death  within  a few  hours.  VI.  Alcoholic  extracts  pre- 
pared from  over-bleached  flour  in  the  same  manner  and  fed  in  the  same  way 
to  rabbits  caused  their  immediate  collapse  and  death.  VII.  Aqueous 
extracts  prepared  from  over-bleached  flours  when  fed  to  rabbits  caused  their 
immediate  collapse  and  death.  VIII.  Alcohol  and  aqueous  extracts  from 
over-bleached  flour,  when  neutralized  with  sodium  bicarbonate  and  fed  to 
rabbits,  cause  the  death  of  the  rabbits  in  a short  time,  demonstrating  that 
it  was  not  the  acidity  that  produced  the  death  of  the  rabbits.  IX.  In 
preparing  aqueous  extracts,  all  nitrite  reacting  material  disappeared  ; 
hence  the  death  of  the  rabbits  in  this  case  must  have  been  due  to  the 
presence  of  other  toxic  material  than  that  of  nitrites. 

Shepard  agreed  with  Ladd’s  evidence. 

Halliburton  generally  confirmed  Ladd’s  evidence.  The  ordinary  white 
bread  of  to-day  was  more  indigestible  than  the  old-fashioned  home-made 
bread  ; the  fact  that  nitrous  acid  was  used  seemed  a probable  explanation. 
The  gluten  was  rendered  less  digestible  by  the  treatment.  The  formation 
of  diazo  compounds  was  a possible  result  of  the  action  of  nitrous  acid  on 
proteins  generally.  That  possibly  accounted  for  the  effect  on  rabbits 
observed  by  Ladd. 

Hehner  had  tested  a number  of  samples  that  had  been  sent  him.  By 
treatment  with  nitrogen  peroxide  diazo  bodies  might  be  formed.  The 
nitrite  present  in  flour  was  no  measure  of  the  damage  that  had  been  done 
by  treatment  with  nitrogen  peroxide.  The  xanthoproteic  reaction  showed 
the  presence  of  a body  resulting  from  the  action  of  nitric  acid  upon  pro- 
teins. Proteins  had  an  enormous  molecular  weight  and  a most  complicated 
structure.  Nitrous  acid,  which  had  a very  small  molecular  weight,  might 
have  a tremendous  effect  on  the  large  protein  molecule.  In  digestion  ex- 
periments on  bread,  he  found  in  every  case  that  the  balance  was  in  favour 
of  unbleached  flour.  He  had  no  knowledge  of  any  diazo  body  having  been 
discovered  or  searched  for  in  bleached  flour. 

As  against  the  allegation  of  injury  to  flour  by  treatment  with  nitrogen 
peroxide,  the  following  evidence  was  given. 

Ballantyne  said  that  the  baking  qualities  and  colour  of  the  flour  were 
in  all  cases  improved  by  the  treatment.  There  was  not  the  same  tendency 
for  the  production  of  rancidity,  and  the  action  of  the  rope-producing  organ- 
isms, B.  mesentericus  fuscus  and  vulgatus,  was  retarded.  Flour  was  not 
tainted  or  harmed  by  reasonable  treatment.  As  a result  of  experiments 
on  the  digestion  of  bread  from  bleached  and  unbleached  flour  he  had  found 
no  difference  between  the  two. 

Dewar  deposed  that  he  agreed  with  Ballantyne’ s evidence.  He  had  made 
pepsin  digestion  experiments  on  washed  gluten  from  bleached  and  un- 
bleached flour,  and  had  observed  no  essential  difference  between  the  two. 
He  had  never  heard  of  any  case  in  which  ill  effects  could  be  attributed  to 
the  use  of  treated  flours.  In  the  commercial  use  of  Andrews’  process  there 
was  proof  of  the  formation  of  nitrates  and  nitrites,  and  undoubtedly  there 
was  some  distribution  of  nitrogen  in  other  ways.  The  amount  was  so  small 
that  it  was  ludicrous  to  think  there  was  any  danger  in  the  use  of  it. 

Willcox  and  Lu^  had  repeated  Ladd’s  experiments  on  rabbits.  Alcoholic 
extracts  from  bread  and  flour  had  been  administered  to  rabbits.  Both 
witnesses  agreed  that  neither  extracts  from  bleached  nor  unbleached  flour 
had  injured  the  rabbits  in  any  way. 


396 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


522.  Judgment. — In  giving  judgment,  Mr.  Justice  Warrington  upheld 
the  Patent,  and  decided  that  the  allegation  of  injury  had  not  been  proved. 
The  following  remarks  were  made  by  the  judge  in  the  course  of  his  review 
of  the  foregoing  evidence  : “I  think  ...  on  the  whole  of  the  evidence 
before  me,  that  as  far  as  baking  qualities  are  concerned — ^that  is  to  say,  the 
size  of  the  loaf,  the  texture  of  the  loaf,  the  colour  of  the  loaf,  and  the  water 
absorption — •!  am  bound  to  hold  on  the  whole  that  the  Plaintiffs  have  estab- 
lished that  by  this  process  the  baking  qualities  of  the  newly-ground  flour  are 
improved.  . . . The  Defendants  have  sought  to  establish  that  [in  addi- 
tion to  the  introduction  of  sodium  nitrite  or  its  equivalent]  the  effect  of 
exposing  the  flour  to  the  peroxide  of  nitrogen  is  to  bring  about  certain  other 
deleterious  chemical  changes  in  some  of  the  very  large  number  of  the  con- 
stituent parts  of  the  flour,  flour  being  an  extremely  complex  body.  In  sup- 
port of  that  theory  the  Defendants  have  called  as  their  principal  witness. 
Dr.  L%dd,  a chemist  of  eminence  and  experience  in  the  United  States,  and 
they  called  him  because  he,  as  a Public  Officer  in  the  State  of  North  Dakota, 
has  devoted  considerable  attention  to  this  question  of  bleaching  flour,  in 
reference  to  the  adulteration  laws  of  that  State  and  of  the  United  States. 
His  experiments,  I think,  must  be  looked  at  with  this  qualification  ; in 
one  sense  of  course  it  renders  them  perhaps  more  valuable  for  this  purpose  ; 
in  another  sense  its  consideration  may  affect  them  the  other  way  ; but  I 
think  one  must  bear  in  mind  in  considering  these  experiments,  that  his  object 
was  to  ascertain  whether  the  result  of  this  treatment  of  the  flour  was  or 
was  not  to  render  the  flour  an  adulterated  product  in  reference  to  the  laws 
of  North  Dakota  and  of  the  United  States,  because  it  arose  under  United 
States  law  as  well  as  under  that  of  North  Dakota.  Under  that  law,  as  I 
understand  it,  a minute  change  in  the  chemical  constituents  of  the  body, 
and  the  most  minute  amount  of  antiseptic  introduced  into  the  constitution 
of  the  body,  would  render  the  product  an  adulterated  food  product  within 
the  meaning  of  that  law.  That  is  a consideration  which  one  must  not  forget 
in  considering  these  experiments.  Dr.  Ladd's  experiments  were  of  two 
kinds.  They  were  first  directed  to  the  comparative  digestibility  of  the 
flour,  and  of  the  bread  made  from  the  flour,  and  in  his  view  the  flour,  as  the 
result  of  these  experiments,  after  treatment  was  digested  more  slowly  than 
the  corresponding  flour  before  treatment.  ...  So  far  as  even  Dr.  Ladd’s 
experiments  were  concerned,  the  difference  in  the  time  of  digestion  in  the 
case  of  the  bread  made  from  the  treated  flour  and  the  bread  made  from  the 
untreated  flour  is  so  small  that  I think  it  is  impossible  for  me  to  say  that 
it  establishes  that,  so  far  as  digestibility  is  concerned,  the  process  has  a 
deleterions  effect  upon  the  flour.  But  fortunately  I have  not  only  the 
experiments  made  by  Dr.  Ladd,  but  I have  experiments  made  by  Mr.  Bal- 
laniyne  and  others  on  the  Plaintiffs’  part — I mean  as  to  digestibility — and 
I have  experiments  made  by  Dr.  Halliburton  in  England  on  the  Defendants’ 
part.  The  result,  in  my  opinion,  of  those  experiments,  taking  them  as  a 
whole,  is  that,  so  far  as  the  bread  made  from  the  flour  is  concerned,  which 
is  the  important  part,  there  is  no  substantial  difference  in  point  of  digesti- 
bility between  the  bread  made  from  the  untreated  flour  and  the  bread  made 
from  the  treated  flour.  . . . But  the  Defendants  Avent  further,  and  at- 
tempted to  establish,  not  only  that  the  digestibility  of  the  flour  was  not 
improved,  but  that  the  flour  had  imparted  to  it  certain  toxic  qualities  Avhich 
made  it  positively  injurious,  and,  in  support  of  that,  they  relied  upon  the 
evidence  of  Dr.  Ladd,  who  spoke  to  certain  experiments  performed  in 
America  on  rabbits  with  fatal  results.  Those  experiments  were  of  this 
nature.  Certain  highly  concentrated  extracts  of,  first,  what  they  called 
over-bleached  flour,  which  had  been  purposely  over-bleached  for  the  purpose 
of  magnifying  the  results — over-bleached  in  the  sense  that  it  was  saturated 


THE  BLEACHING  OF  FLOUR. 


397 


with  oxide  of  nitrogen — and  certain  concentrated  extracts  of  what  was 
called  commercially  bleached  flour,  although  it  is  difficult  to  say  exactly 
what  that  meant,  were  administered  to  rabbits.  I think  each  dose  of  those 
concentrated  extracts  administered  to  a rabbit  contained  about  as  much  of 
the  substance,  which  it  was  desired  to  administer,  as  would  be  found  in  200 
grams  of  flour,  but  at  any  rate  it  was  very  highly  concentrated.  The  result 
of  the  administration  of  the  extract  from  the  over-bleached  flour  was  that 
the  unfortunate  animals  died  of  strong  corrosive  poisoning.  . . . Those 
to  which  the  commercially  bleached  flour  was  administered  also  died  . . . 
and  it  would  appear  that  they  had  died  from  some  irritant  poison.  What 
it  was  does  not  appear.  Those  experiments,  taken  by  themselves,  were 
somewhat  striking,  but  the  Plaintiffs  have  performed  experiments  in  Eng- 
land, which  they  were  led  to  by  the  experiments  spoken  to  by  Hr.  Laddy 
with  very  different  results.  Hr.  Willcox  and  Hr.  Luff,  who  are  two  of  the 
most  eminent  men  in  their  branch  of  the  medical  profession,  have  made 
experiments  on  rabbits  with  concentrated  extracts  of  flour  bleached  under 
the  Plaintiffs'  process,  and  they  have  made  these  extracts,  following  minutely 
the  directions  given  by  Hr.  Ladd,  and  they  have  administered  them  to  a 
large  number  of  rabbits,  have  kept  those  rabbits  under  observation  for 
many  days  after  the  administration,  and  have  observed  no  effect  on  the 
rabbits  beyond  a temporary  intoxication  caused  by  the  fact  that  the  extract 
was  alcoholic.  Now  in  that  state  of  things  how  is  it  possible  for  me  to  come 
judicially  to  the  conclusion — ^the  onus  of  proof  being  on  the  Hefendants — 
that  the  bread  baked  from  this  bleached  flour  contains  some  toxic  qualities 
which  would  not  be  contained  in  the  bread  made  from  the  untreated  flour  ? 
It  seems  to  me  quite  impossible.  But  I do  not  like  to  let  it  rest  there.  I 
think  it  would  be  extremely  dangerous,  from  the  results  of  the  experiments 
made  in  America  with  the  American  bleached  flour,  bleached  according 
to  the  American  processes,  to  infer  the  result,  which  the  Hefendants  would 
ask  one  to  infer,  in  reference  to  flour  bleached  by  the  Andrews’  process. 
I think  that  I must  come  to  the  conclusion,  on  the  balance  of  the  evidence, 
that  the  Plaintiffs  have  established  that,  so  far  as  that  part  of  the  attack 
is  concerned,  no  deleterious  action  on  the  flour  is  caused.  I have  not  quite 
done  with  that,  because  I must  not  leave  it  without  referring  to  another 
matter  also  referred  to  by  Hr.  Ladd.  He  said  that  the  effect  of  the  treat- 
ment, in  his  opinion,  is  that  the  nutritive  qualities  of  the  flour  are  deleteriously 
affected.  So  far  as  that  is  concerned  I think  that  is  pure  theory,  and  I do 
not  And  any  positive  fact  or  anything  which  1 can  take  hold  of  to  support 
hat.  It  seems  to  me,  therefore,  that,  whether  you  regard  it  from  the  point 
of  view  of  digestion,  whether  you  regard  it  from  the  point  of  view  of  nutri- 
tion, or  w^iether  you  regard  it  from  the  point  of  view  of  positive  harm,  I 
must  come  to  the  conclusion  that  the  Plaintiffs  have  established  the  truth 
of  the  statement  in  Andrews’  specification  that  no  deleterious  action  on  the 
flour  is  caused  by  the  above-mentioned  treatment."  {Reports  of  Patent 
Cases,  XXVI,  1909,  597.) 

The  only  point  occurring  in  the  judgment  quoted  on  which  perhaps 
comment  should  be  made  is  the  distinction  drawn  by  the  learned  judge 
between  American  and  English  bleached  flours.  Both  are  bleached  by 
nitrogen  peroxide,  produced  in  the  former  case  under  Alsop's  Patent  by  a 
flaming  discharge  of  electricity  through  air,  and  in  the  latter  by  the  action 
of  ferrous  sulphate  on  nitric  acid.  Chemists  in  general  will  agree  that  the 
Alsop  process  is  no  more  likely  to  be  injurious  to  flour  than  that  of  Andrews. 

523.  Flour  Bleaching,  its  Relation  to  Bread  Production  and  Nutrition, 
Wesener  and  Teller. — This  paper  is  very  largely  of  the  nature  of  a reply 
to  Ladd,  and  necessarily  to  a great  extent  deals  with  matters  already  re- 


398 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


f erred  to.  In  opposition  to  the  view  that  bleaching  introduces  an  anti- 
septic into  the  flour,  experiments  are  quoted  1)0  show  that  the  presence  of 
even  considerable  amounts  of  nitrite-reacting  nitrogen  in  flour  acts 
favourably  to  the  development  of  yeast  in  dough,  and  therefore  such  nitro- 
gen oxide  is  not  a preservative.  The  writers  fed  rats  on  biscuits  and  bread 
made  from  bleached  flour  for  some  months,  and  found  that  they  suffered 
no  injury.  They  also  repeated  Ladd’s  experiments  with  rabbits  and  found 
no  injury  was  done  to  the  animals  by  the  extract  from  bleached  flour. 

The  vTiters  regard  it  as  impossible  that  the  acid  in  Ladd’s  flour  could 
have  done  any  injury  to  the  rabbits,  because  of  its  infinitesimal  amount. 
They  calculate  that  the  total  amount  of  nitrous  and  nitric  acid  which  might 
be  present  in  one  of  the  hours  which  was  used  by  Ladd  for  his  test,  based 
upon  double  the  amount  of  nitrite-reacting  nitrogen  found  (3  parts  per 
million)  and  all  calculated  to  nitric  acid,  would  be  equivalent  to  only  5*4 
milligrams  (xV  drop)  of  nitric  acid.  This  amount  of  nitric  acid  is  prac- 
tically (x^Vo  medicinal  dose  of  nitric  acid  as  given  in  the  U.S.  Dispen- 
satory, and  according  to  Ladd’s  testimony  the  liquid  administered  to  the 
rabbits  was  much  greater  in  amount  than  necessary  to  produce  the  dilution 
specified  in  that  work  for  internal  doses  of  nitric  acid.  Under  the  circum- 
stances we  could  not  expect  any  corrosive  action  from  this  amount  of  acid, 
even  assuming  that  it  could  have  been  separated  out  of  the  hour  as  free 
acid  without  in  any  manner  combining  with  the  organic  matter  of  the  hour 
and  alcohol. 

Diazo  Test. — In  view  of  the  fact  that  poisonous  diazo  compounds  are 
alleged  to  be  formed  by  the  nitrogen  peroxide  bleaching  of  flour,  the  vHters 
made  the  following  experiment.  One  hundred  grams  of  unbleached  flour 
were  introduced  into  a flask  of  about  one  litre  capacity,  and  carbon  dioxide 
passed  into  it  for  IJ  hours  with  frequent  vigorous  agitation.  Dilute  hydro- 
chloric acid  which  had  been  recently  boiled  was  added  warm  and  the  mix- 
ture agitated.  The  evolved  gas  was  then  swept  by  a stream  of  carbon 
dioxide  into  a Schiff  azotometer  containing  the  usual  solution  of  caustic  soda. 
A small  amount  of  gas  passed  to  the  top  which  could  not  be  absorbed  by 
repeated  agitation.  The  volume  of  this  gas  was  1*4  c.c.  It  was  tested 
w’ith  a lighted  paper.  It  did  not  burn,  nor  did  it  support  combustion  when 
tested  as  indicated  by  Prof.  Ladd.  The  above  experiment,  carried  on  in 
co-operation  with  Prof.  Haines,  was  carried  out  as  detailed  by  Ladd  and 
used  by  him  as  testimony  in  North  Dakota  to  show  the  presence  of  diazo 
compounds  of  the  nature  of  tyrotoxicon  resulting  in  bleached  flour  from  the 
action  of  the  bleaching  gases  upon  the  constituents  of  the  same.  The 
amount  of  gas  which  he  obtained  from  the  bleached  flour  is  substantially 
the  same  as  we  obtained  in  the  above  experiment  from  unbleached  flour, 
and  is  undoubtedly  air  which  adheres  to  the  particles  of  flour  and  which 
cannot  be  removed  even  by  the  most  careful  and  persistent  treatment  with 
carbon  dioxide.  That  the  experiments  tend  to  show  the  presence  of  tyro- 
toxicon, or  that  such  tyrotoxicon  would  be  formed  by  the  action  of  bleaching 
gases  on  flour  is  not  probable  when  we  remember  that  this  material,  as 
found  in  cheese  and  other  milk  products,  is  wholly  the  result  of  bacterial 
growth,  and  that  it  is  of  an  exceedingly  unstable  nature. 

In  conclusion,  Wesener  and  Teller  emphasise  their  view  that  any  improve- 
ment in  quality  brought  about  by  removing  an  unusually  large  amount  of 
colour  present  in  a flour  which  was  inferior  because  of  the  presence  of  such 
excess  of  colour  certainly  cannot  be  looked  upon  as  in  any  way  injuring  or 
deceiving  the  consumer,  as  has  been  contended  by  some,  for  the  cause 
which  produced  the  inferiority  now  no  longer  exists.  The  purpose  of  the 
bleaching  is  to  remove  and  not  to  conceal  the  inferiority.  The  prohibition 
of  the  bleaching  of  flour  will  curtail  the  use  and  cut  down  the  price  of  durum 


THE  BLEACHING  OF  FLOUR. 


399 


wheat  and  all  wheats  \\'hich  have  an  intense  yellow  colour  in  spite  of  the 
fact  that  aside  from  this  some  of  these  wheats  produce  flour  of  the  very 
highest  quality.  The  effect  of  this  is  naturally  felt  more  by  the  producer 
of  wheat  and  the  consumer  of  flour  than  by  the  miller  whose  prices  are 
regulated  by  market  values  and  competition.  {Journal  of  Industrial  and 
Engineering  Chemistry,  I.,  Oct.,  1909.) 

524.  Bleaching  and  Flavour  and  Texture. — Although  bleaching  may 
materially  improve  the  colour  of  a flour,  it  does  not  thereby  change  a lower 
grade  flour  into  a higher  grade  one.  There  may  be  some  conditioning,  but 
the  essentials  of  the  lower  grade  flour  still  remain  unchanged.  Flour  of  the 
highest  grade  possesses  a delicacy  of  flavour,  and  in  the  resultant  bread  or 
biscuits,  a silkiness  of  texture,  which  are  not  present  in  inferior  grades. 
Even  if  bleaching  causes  the  lower  grade  to  simulate  the  highest  in  colour, 
it  is  not  simultaneously  converted  into  flour  of  the  flavour  and  texture  of 
the  highest  grade. 

This  line  of  argument  must  not,  however,  be  pushed  too  far.  During 
the  whole  development  of  milling  processes,  there  has  been  a steady  increase 
in  the  amount  of  patent  flour  obtainable  from  the  wheat.  At  first,  only  a 
very  small  quantity  of  patent  flour  of  the  very  best  colour  was  produced. 
The  remainder  contained  the  rest  of  the  flour,  darkened  by  the  presence  of 
milling  impurities.  The  patent  flour  was  not  only  of  good  colour,  but  it 
vas  also  distinguished  from  the  residual  flour  by  the  greater  delicacy  of 
flavour  and  fine  texture  before  referred  to.  With  improvements  in  milling, 
more  of  this  residual  flour  was  freed  from  its  impurities,  and  obtained  of 
equal  colour  to  the  so-called  patent  flour.  The  yield  of  patent  flour  of  the 
standard  colour  was  thereby  increased  ; but  save  in  colour,  the  better  puri- 
fication of  the  former  residual  flour  did  not  alter  the  inherent  qualities  of 
the  flour  itself.  Yet  no  one  has  regarded  this  transference  of  such  flour  to 
the  patent  portion  as  being  in  any  way  illegitimate.  By  parity  of  reasoning, 
an  increase  of  the  amount  of  flour  of  patent  colour  standard,  by  harmless 
bleaching  processes,  cannot  be  regarded  as  an  adulteration,  nor  is  such  flour 
misbranded  when  called  “ patent  flour.” 

525.  Nutritive  Value  of  Bleached  Flours. — There  are  certain  advocates 
of  the  general  use  of  flour  of  lower  grades,  who  have  recently  condemned 
the  use  of  bleaching.  It  is  difficult,  however,  to  follow  their  argument. 
The  very  foundation  of  their  position  is  that  the  darker  flours  are  more 
nutritious  and  wholesome  than  those  which  are  lighter  in  colour.  Only, 
unfortunately,  say  they,  the  public  is  so  blind  to  its  own  interests,  that  in  the 
pursuit  of  mere  whiteness  it  overlooks  all  the  other  solid  and  real  advantages 
possessed  by  darker  flours.  But  if  the  darker  flour  is  unchanged  in  any 
other  particular,  and  loses  none  of  its  food  value  by  bleaching,  then  surely 
any  process  by  which  it  is  rendered  more  attractive  to  the  eye  should  find 
favour  with  those  who  wish  to  see  the  naturally  darker  flours  more  widely 
and  extensively  used. 

Note  ; Local  Government  Board  Reports. — Two  reports  on  the  joint  sub- 
jects of  Flour  Bleaching  and  Flour  “ Improvers,”  by  Drs.  Hamill  and 
Monier-Williams,  have  just  been  published  by  the  Local  Government  Board . 
A summary  of  their  experimental  results  and  conclusions  are  given  in 
Chapter  XX,  paragraphs  629  and  630. 


CHAPTER  XVIII. 

BREAD-MAKING. 


526.  Salt,  Sodium  Chloride,  NaCl. — Havingfully^dealt  with  flour  and  yeasty 
there  now  remain  only  salt  and  water  as  es  sential  constituents  of  bread ; some 
brief  reference  must  be  made  to  these  compounds.  Salt  is  a white  crystalline 
body,  about  equally  soluble  in  either  hot  or  cold  water,  and  having  a charac- 
teristic saline  taste.  Salt  is  used  in  the  making  of  bread  for  two  reasons — 
first,  to  give  the  necessary  flavour,  without  which  bread  would  be  tasteless 
and  insipid.  In  addition  to  its  owm  saline  flavour,  experiments  have  shown 
that  the  presence  of  salt  stimulates  the  capacity  of  the  palate  for  recognis- 
ing flavours  of  other  substances.  Thus,  minute  quantities  of  sugar  are 
recognised  in  the  presence  of  salt  which  in  its  absence  would  be  unnoticed. 
This  doubtless  is  one  of  the  reasons  for  the  importance  of  salt  as  a flavouring 
agent. 

In  the  second  place,  salt  actively  controls  some  of  the  chemical  changes 
which  proceed  during  fermentation  ; thus,  salt,  in  the  quantities  employed 
in  bread-making,  produces  a decidedly  binding  effect  on  the  gluten  of  the 
dough.  It  further  checks  diastasis,  and  so  retards  the  conversion  of  the 
starch  of  the  flour  into  dextrin  and  maltose.  Salt  also  checks  alcoholic 
fermentation  ; the  results  of  careful  measurement  of  this  action  are  given 
in  Chapter  XI.,  paragraph  371.  The  retarding  influence  of  salt  also  extends 
to  the  other  ferments,  as  lactic,  viscous  or  ropy  ferments,  and  so  tends  to 
prevent  injurious  fermentation  going  on  in  the  dough. 

527.  Water. — In  considering  the  quality  of  water  for  dietetic  purposes,, 
the  chemist,  first  and  foremost,  addresses  himself  to  the  task  of  determining 
whether  or  not  the  water  shows  evidences  of  previous  sewage  contamination. 
He  next  ascertains  the  hardness  and  also  the  amount  of  saline  matters 
present.  The  methods  he  adopts  for  this  purpose  vary,  but  the  conclusion 
at  which  he  seeks  to  arrive  is  practically  the  same.  It  may  be  safely  laid 
down  as  a rule  for  the  baker  that  a water  which  would  be  rejected,  on  analysis, 
as  unfit  for  drinking  purposes,  should  also  without  hesitation  be  rejected 
by  him.  Water  containing  living  organisms  should  in  particular  be  carefully 
avoided,  as  these  might  very  possibly  set  up  putrefactive  fermentation 
during  panification. 

Among  the  waters  which  would  be  passed  by  the  chemist  for  drinking 
purposes,  there  exist,  however,  considerable  differences.  Thus,  some  are 
hard,  others  are  extremely  soft  ; salt  may  be  present  in  certain  waters, 
while  in  others  it  may  be  almost  absent.  The  difference  between  hard  and 
soft  waters  is  that  the  former  contain  carbonates  and  sulphates  of  lime  or 
magnesia  in  solution  ; the  act  of  boiling  precipitates  the  carbonates  as  a fur 
on  the  vessel  used,  and  so  hardness  due  to  the  carbonates  is  termed  tem- 
porary hardness,  in  distinction  from  that  of  the  sulphates  which,  not^being 
removed  by  boiling,  constitutes  permanent  hardness.  / 

]\Iuch  speculation  exists  as  to  whether  or  not  the  hardness  or  otherwise 
of  a water  exerts  any  practical  influence  on  bread-making.  In  brewing 
it  is  recognised  that  a soft  water  obtains  more  extract  from  the  malt  than 
a hard  one,  but  the  comparison  with  the  case  of  bread  is  scarcely  fair,  because 


400 


BREAD-MAKING. 


401 


in  the  wort  the  liquid  is  filtered  off  from  the  “ grains/"  while  in  bread  the 
whole  mass,  whether  soluble  or  insoluble,  goes  into  the  oven  together. 
The  general  tendencies  of  hard  water  would  be  to  dissolve  less  of  the  pro- 
teins than  would  a soft  water,  and  consequently  the  dough  in  the  former  case 
would  be,  to  the  extent  of  the  action  of  the  hard  water,  tighter  and  tougher 
than  that  produced  when  the  water  is  soft.  (It  will  be  remembered  that 
gliadin  is  soluble  in  distilled  water,  but  that  the  salts  of  the  flour  itself  are 
sufficient  to  prevent  its  going  into  solution.)  The  use  of  very  soft  water 
is  very  nearly  equivalent  to  the  result  produced  by  using  softer  flours. 
Thus,  hard  water  will  tend  to  make  whiter  bread,  because,  not  only  is  the 
quantity  of  proteins  dissolved  smaller,  but  with  the  same  quantity  in  solu- 
tion their  action  would  be  checked  by  the  presence  of  the  soluble  lime  salts. 
At  the  same  time  the  bread  would  eat  somewhat  harsher  and  drier  than 
that  made  with  soft  water.  Speaking  generally  the  changes  which  go  on 
during  panification  proceed  more  rapidly  with  soft  than  with  hard  water. 
Working  in  a similar  manner,  ^.c.,  with  the  same  times  and  temperatures, 
hard  water  is  not  likely  to  produce  as  good  results  as  soft  water  at  its  best. 
In  order  to  obtain  the  same  results,  the  various  steps  in  the  process  of  fer- 
mentation should  be  somewhat  modified  ; thus,  the  bread  would  probably 
require  to  lie  somewhat  longer  in  the  sponge  and  dough  stages,  or  the  tem- 
perature employed  might  be  somewhat  higher.  Both  colour  and  flavour 
of  bread  depend  on  fermentation  being  allowed  to  proceed  to  exactly  the 
right  point  and  no  further — hence  hard  water,  by  altering  the  length  of  the 
fermenting  process,  will  affect  both  these  when  fermentation  is  carried  out 
under  precisely  the  same  conditions  with  hard  water  as  with  soft.  Further, 
as  the  keeping  moist  of  bread  depends  largely  on  the  degree  of  change  pro- 
duced in  the  gluten  and  other  constituents,  it  is  quite  possible  that  the  rate 
of  drying  may  be  affected  by  the  use  of  hard  water.  Some  years  ago  one 
of  the  authors  made  a series  of  experiments  on  the  manufacturing  scale 
on  the  comparative  advantages  of  hard  and  soft  water  for  bread-making 
purposes.  The  use  of  a water- softening  plant  was  afforded  him  by  the 
inventors,  and  over  some  weeks  the  character  of  bread  made  with  the  very 
hard  water  of  the  district  compared  with  that  made  from  the  softened  water. 
The  general  conclusion  was  that  no  very  great  difference  was  caused, 
or  at  least  no  difference  that  could  not  be  produced  by  other  modifications 
under  the  control  of  the  baker,  such  as  slight  alterations  of  the  blend  of 
the  flour,  or  mode  of  fermentation.  So  far  as  it  went  the  action  of  soft 
water  was  considered,  everything  else  being  equal,  an  improvement  on  the 
hard. 

528.  Objects  of  Bread-making. — The  miller’s  art  is  directed  to  the  task 
of  separating  that  part  of  wheat  most  suitable  for  human  food  from  the 
bran  and  other  substances  whose  presence  is  deemed  undesirable.  The 
flour  thus  produced  requires  to  be  submitted  to  some  cooking  operation 
before  it  is  fitted  for  ordinary  consumption.  Given  the  flour,  it  is  the  baker’s 
object  to  cook  it  so  that  the  result  may  be  an  article  pleasing  to  the  sight, 
agreeable  to  the  taste,  nutritious,  and  easy  of  digestion.  It  is  universally 
admitted  that  these  ends  are  best  accomplished  by  mixing  the  flour  with 
water,  so  as  to  form  a dough  ; which  dough  is  charged,  in  some  way,  with 
gas,  so  as  to  distend  it,  and  then  baked.  The  result  is  a loaf  whose  interior 
has  a delicate,  spongy  structure,  which  causes  good  bread  to  be,  of  all  wheat 
foods,  the  one  most  readily  and  easily  digested  when  eaten.  This  charging 
with  gas  is  most  commonly  effected  by  fermentation,  but  other  methods 
are  also  to  a limited  extent  adopted  : these  will  be  described  in  turn.  Fer- 
mentation has  one  great  advantage  over  other  bread-making  processes,  ]n 
that  it  not  only  produces  gas,  but  also  effects  other  important  changes  in 
certain  of  the  constituents  of  flour. 


D D 


402 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


529.  Definitions  of  various  Stages  of  Bread-making.— The  methods 
employed  in  the  manufacture  of  bread  differ  in  various  parts  of  the  country  : 
it  will  be  well  to  first  give  a few  definitions,  and  then  proceed  to  describe 
and  discuss  the  principal  methods  and  their  underlying  principles. 


530.  The  Ferment. — ^Among  the  older  bakers  the  first  step  in  bread- 
making was  the  preparation  of  a “ ferment.''  This  most  commonly  con- 
sisted of  potatoes,  boiled  and  mashed  with  water  into  a moderately  thin 
liquor,  to  which  a little  raw  fiour  was  generally  added.  The  yeast  was  next 
introduced,  and  fermentation  allowed  to  proceed  until  the  whole  of  the 
fermentable  matter  was  exhausted,  and  a quiescent  stage  reached.  The 
essential  point  about  a ferment  is  that  it  shall  contain  saccharine  matters 
and  yeast  stimulants  in  such  a form  as  to  favour  growth  and  reproduction 
of  yeast,  and  growth  and  reproduction  in  a particularly  vigorous  condition. 
For  this  purpose  it  is  necessary  that  the  ferment  be  not  too  concentrated, 
because  no  yeast  reproduction  occurs  with  too  great  a degree  of  concentra- 
tion. On  Briant's  authority  the  following  table  is  given  in  the  Quarterly 
Trade  Review  {Bakers’  Q.T.R.)  : — 


6 

10 

14 

19 

25 

36 


Concentration  of  the  Medium 
in  which  Yeast  was  grown. 

per  cent,  of  solid  matter 


Extent  of  Yeast 
Reproduction. 

6*60  times. 

7-37  „ 

14-20 
10-10  „ 

12-50  „ 

No  reproduction, 
of  solid  matter  is  here  indicated 
Independently  of  this,  too,  the 


A medium  containing  about  14  per  cent 
as  being  most  favourable  for  reproduction, 
actual  quantity  of  ferment,  as  compared  with  quantity  of  yeast,  is  of  im- 
portance ; for  on  referring  to  Adrian  Brown  on  fermentation  (Chapter  IX.), 
it  is  seen  that  too  great  a crowding  of  yeast  cells,  independently  of  the  com- 
position of  the  liquid,  may  permit  fermentation,  while  absolutely  inhibiting 
reproduction. 

The  introduction  of  raw  flour  possesses  some  interest  in  view  of  the  light 
thrown  on  the  toxic  nature  of  flour  toward  yeast  in  paragraph  378.  Such  raw 
flour  cannot  act  as  a stimulant  to  the  yeast  in  the  ferment,  but  may  possibl;^ 
serve  to  inure  the  yeast  to  the  effects  produced  thereon  by  flour. 

Various  substitutes  for  potatoes  may  be  used  in  the  ferment  ; among 
these  are  raw  and  scalded  flour,  malt,  malt  extracts,  and  other  preparations. 


531.  The  Sponge. — This  consists  of  a portion  only  of  the  flour  that  it 
is  intended  to  convert  into  bread,  taken  and  made  into  a comparatively 
slack  dough,  with  a portion  or  the  whole  of  the  water  to  be  used  in  making 
all  the  flour  into  bread.  The  yeast  or  the  “ ferment  " (together  with  usually 
a small  proportion  of  salt)  is  incorporated  into  the  sponge.  Sponges  con- 
taining the  whole  of  the  water  are  termed  “ batter  " or  “ flying  " sponges. 
Because  of  its  greater  slackness,  compared  with  dough,  fermentative  changes 
proceed  more  rapidly  in  the  sponge.  One  of  the  authors  made  a series  of 
observations  on  small  fermenting  sponges  made  in  the  laboratory  with 
distillers'  yeast  ; these  were  very  slack,  and  the  number  of  yeast  cells  was 
counted  by  means  of  the  haematimeter  immediately  on  mixing,  and  again 
subsequently  at  intervals  of  about  two  hours.  Not  only  was  there  no  repro- 
duction, but  the  cells  present  gradually  lessened  in  number,  doubtless  as  a 
result  of  disintegration  of  those  deficient  in  life  and  vigour.  From  this, 
and  the  reproduction  table  given  under  the  heading  of  Ferment,  the  con- 
clusion is  drawn  that  no  reproduction  whatever  of  yeast  {Saccharomyces  cere- 
visice)  occurs  in  the  sponge. 


BREAD-MAKING. 


403 


532.  The  Dough. — This  consists  of  the  whole  of  the  flour  to  be  used, 
together  with  the  whole  of  the  water  and  other  constituents  of  the  bread, 
whether  mixed  straight  off  or  with  intermediate  stages  of  ferment  and  sponge. 

533.  Various  Methods  of  Bread-Making. — Among  these  may  be  included 
the  following  : — 

Dough  made  right  off — Off-hand  or  Straight  Doughs. 

Ferment  and  Dough. 

Sponge  and  Dough. 

Ferment,  Sponge,  and  Dough. 

Flour  Barm,  Sponge,  and  Dough — Scotch  System. 

A useful  classification  of  bread-making  processes  on  this  principle  is 
given  in  an  article  on  “ The  Best  System  of  Bread-Making,""  contributed 
to  the  National  Association  Review  (late  Q.T.R.),  by  W.  T.  Callard.  The 
following  arrangement  has  been  suggested  by  Callard"s  paper  : — 


534.  Off-hand  Doughs. — In  this  system  the  dough  is  made  direct,  with- 
any  preceding  stages  of  ferment  or  sponge. 

Types  of  Bread  made  hy  Method. — Sometimes  employed  in  making  tin 
bread  (^.e.,  bread  baked  in  tins),  but  also  at  times  for  making  crusty  bread. 

, Flours  Used. — Strong  patent  flours,  mixed  very  slack  for  tin  bread. 
Strong  London  households  for  crusty  cottage  bread. 

Dough- Making. — Generally  from  IJ  lbs.  to  2 lbs.  of  distillers"  yeast  taken 
to  the  sack  (280  lbs.),  with  sometimes  a little  brew^ers"  yeast  in  addition. 
Formerly  from  10  to  14  lbs.  of  boiled  potatoes  were  also  added,  but  this 
'appears  to  be  no  longer  the  rule.  Salt  from  3 to  3J  lbs.  per  sack.  The  slack 
tin-bread  doughs,  containing  70  quarts  w'ater  per  sack,  are  frequently  made 
by  hand,  and  fermented  at  a temperature  of  about  76-80°  F.  wdien  mixed  : 
they  lie  for  about  ten  hours,  and  yield  about  104  loaves  per  sack. 

For  cottage  bread  the  dough  is  made  much  stiff er,  about  60  quarts 
of  w^ater  per  sack,  and  usually  allowed  to  ferment  at  a higher  temperature, 
so  as  to  be  ready  in  about  six  hours.  These  tight  doughs  are  generally 
made  by  machinery,  or  else  the  dough  is  made  at  first  somewhat  slack,  and 
then  “ cut  back  ""  and  dusted  up  at  intervals. 

Economic  Advantages  and  Disadvantages. — All  labour  of  sponging  and 
extra  manipulation  saved,  bread  produced  in  less  time,  only  one  blend  of 
flour  and  one  doughing  operation.  An  increased  cost  results  from  the  large 
quantity  of  yeast  required  ; also  number  of  troughs  and  consequent  space 
necessary  is  considerable. 


Character  of  Bread — Appearance. — Very  red  and  fiery  in  crust,  not  clear 
in  the  partings  of  the  crust,  volume  fair.  When  used  for  cottage  bread,  a 
small  and  rough-looking  loaf  is  the  result. 

Yield. — Large,  the  high  proportion  of  yeast  enabling  the  Hour  to  carry 
considerable  quantities  of  water. 

Flavour. — Sw^eet,  but  somewLat  neutral  at  times,  and  even  harsh,  when 
fermentation  has  been  pressed  to  the  utmost  extent.  In  cottage  bread 
when  forced,  to  get  a big  loaf,  there  is  often  a tendency  to  sourness. 

Texture. — Poor,  loaf  devoid  of  silkiness  or  pile,  holes  of  aeration  unequal, 
and  cottages  small  and  close. 

Colour. — Dull,  and  devoid  of  sheen. 

Moisture. — High,  even  to  clamminess  in  some  loaves. 

Summary. — A system  in  which  colour  and  appearance  are  sacrificed 
to  moisture  and  convenience  of  w^orking. 


535.  Ferment  and  Dough. — ^As  the  term  implies,  this  bread-making 
system  is  one  in  wfiiich  a ferment  and  dough  are  employed. 

Types  of  Bread  made  hy  Method. — Used  very  largely  in  London  and 


404 


THE  TECHNOLOGY  OF  BREAD-MAKING 


the  South  of  England  in  the  manufacture,  of  crusty  bread,  and  also  well 
adapted  for  tin  bread. 

Flours  Used. — These  should  be  fairly  soft,  and  spring  Americans  should 
not  exceed  40  per  cent,  of  the  whole  mixture.  Of  hard  wheat  flours,  Rus- 
sians seem  to  suit  this  method  of  bread-making  better  than  the  spring 
American,  owing  to  their  glutens  mellowing  down  more  rapidly.  Some 
bakers  who  work  by  this  method  claim  to  use  English  wheat  flours  to  the 
exclusion  of  all  other  varieties.  Winter  American  patents  and  also  Hun- 
garian flours  answer  well  in  this  type  of  bread. 

The  Ferment. — This  most  frequently  consists  of  from  10  to  14  lbs.  of 
potatoes  to  the  sack,  boiled  or  steamed,  and  then  mashed  with  water  so  as 
to  yield  about  3 gallons  of  liquor.  Brewers’  yeast  is  frequently  used  in 
ferments,  although  recently  distillers’  yeasts  have  been  similarly  worked. 
The  ferment  is  “ ready  ” in  about  six  hours.  Various  substances  are  em- 
ployed as  substitutes  for  potatoes  in  ferments. 

Dough-Making. — The  ferment  is  taken,  together  with  about  to  3 lbs. 
salt  to  the  sack,  w^ater  over  all  to  the  extent  of  about  56  quarts  to  the  sack, 
and  allow^ed  to  wwk  fairly  warm,  say  80-84°  F.  The  dough  is  allow'ed  to 
lie  for  various  times,  from  two  to  about  five  hours.  This  will  depend  on 
the  w^orking  temperature,  character  of  flour,  and  strength  or  quantity  of 
ferment  used. 

Economic  Advantages  and  Disadvantages. — After  the  labour  of  preparing 
the  ferment,  all  that  of  making  and  breaking  down  the  sponge  is  avoided  ; 
there  is  but  one  blend  of  flour  required  ; and  altogether  the  cost  of  manipula- 
tion is  very  little  more  than  that  of  off-hand  doughs  subsequent  to  the 
ferment.  It  has  the  advantage  that  comparatively  few  troughs  are  neces- 
sary, because  in  most  cases  each  can  be  used  several  times  over  during  the 
day’s  wwk.  The  yeast  required  is  not  high  in  amount,  but  the  potatoes 
used  sensibly  increase  the  cost  of  production,  and  from  their  dirty  character 
are  a nuisance  in  the  bakery. 

Character  of  Bread — Appearance. — Loaf  is  usually  well  risen,  bearing 
in  mind  the  class  of  flours  employed.  The  crust  is  rough,  inclined  to  break, 
and  usually  “ short  ” and  crisp  in  texture.  Is  bright  and  clear,  except 
when  too  strong  dark  flours  are  used. 

Yield. — Small,  because  soft  flours  are  generally  employed,  say  about  90 
loaves  to  the  sack. 

Flavour. — Good,  and  particularly  suited  to  the  London  palate,  there 
being  considerable  sw^eetness.  As  in  all  cases  where  ferments  are  used, 
there  is  danger  of  “ yeastiness,”  unless  care  is  taken  that  the  ferment  is 
not  allowed  to  stand  sufficiently  long  for  lactic  or  other  foreign  fermenta- 
tion to  proceed  unduly  at  the  close  of  the  alcoholic  fermentation. 

Texture. — Close  and  even  {i.e.,  holes  of  aeration  regular),  but  not  silky. 

Colour. — Good,  with  nice  bloom  ; crust  tendency  to  browmness,  but 
should  be  free  from  any  foxy  tint,  the  result  of  absence  of  very  hard  flours. 
Crumbs  clear  and  bright,  but  comparatively  devoid  of  sheen. 

Moisture. — Fair,  w hen  bread  is  first  made  ; but  all  bread  of  this  kind  has 
seen  its  best  twelve  hours  after  leaving  the  oven 

Summary. — A very  useful  system  of  bread-making,  w^ell  adapted  to 
districts  where  bread  is  eaten  very  fresh. 

536.  Sponge  and  Dough. — This  is  probably  the  most  wddely  used  of  all 
l)read-making  methods,  and  evidently  therefore  adapts  itself  w^ell  to  diversi- 
fied requirements. 

Types  of  Bread  made  hy  Method. — Almost  every  kind  of  bread,  from 
the  tightest  crusty  bread  dough  to  that  for  the  slackest  tin  bread,  may  be 
made  in  this  manner. 


BREAD-MAKING. 


405 


Flours  Used. — Practically  every  variety  of  bread-flour  offered  to  the 
baker  can  be  utilised  in  this  method  ; the  great  advantage  is  that  hard 
flours  can  be  used  in  the  sponge,  thus  giving  them  the  advantage  of  long 
fermentation,  while  softer  flours  are  appropriately  worked  in  at  the  dough 
stage. 

Sponge- Making  or  “ Setting.” — A blend  of  hard  flour  is  used  for  this 
purpose,  and  a quantity  taken  equal  to  from  a quarter  to  a half  the  whole 
of  the  flour  to  be  used.  A frequent  plan  is  to  take  a bag  (140  lbs.)  of  spring 
American  patents  for  the  sponge,  and  a sack  of  home-milled  softer  flour  for 
the  dough.  Sufflcient  water  must  be  taken  to  make  the  sponge-dough  very 
slack,  say  from  to  8 gallons  of  water  to  the  100  lbs.  of  flour.  Distillers" 
yeast  is  now  most  frequently  employed,  and  a quantity  may  be  taken  of 
from  6 to  10  ounces  to  the  sack  of  flour  (over  sponge  and  dough)  ; if  wished 
brewers"  yeast  may  be  employed  instead,  but  the  quantity  must  considerably 
vary  according  to  the  strength  of  the  yeast.  A little  salt  is  usually  added 
to  the  sponge,  say  about  J lb.  to  the  sack.  Formerly  potatoes  were  occa- 
sionally added  direct  to  the  sponge  : this  custom  seems  now,  however, 
almost  obsolete.  On  being  set,  the  sponge  is  allowed  to  ferment  for  from 
six  to  ten  hours,  according  to  the  temperature,  quantity  of  yeast,  character 
of  flour,  and  other  considerations.  In  machine-bakeries  sponges  are  usually 
set  somewhat  stiffer  than  where  sponges  and  doughs  are  made  by  hand. 

The  Dough. — The  sponge,  when  ready,  is  taken,  mixed  with  the  remainder 
of  the  flour,  the  water,  and  the  salt.  Soft,  flavoury  flours  are  introduced 
at  this  stage,  and  the  dough  allowed  to  lie  about  two  hours.  The  tempera- 
ture both  of  sponges  and  doughs  is  governed  by  how  soon  either  may  be 
wanted,  the  atmospheric  temperature,  and  other  considerations. 

Economic  Advantages  and  Disadavntages — The  adaptability  of  this 
method  is  one  of  its  great  advantages,  and  also  the  readiness  with  which 
it  lends  itself  to  the  selection  and  use  of  any  variety  of  flour.  There  is 
somewhat  greater  expense  in  working,  because  of  the  double  handling  in- 
volved in  working  the  sponge  as  well  as  the  dough.  It  is  doubtful,  how- 
ever, whether  this  is  appreciable  in  the  hand-made  bread  bakery,  as  it 
amounts  simply  to  making  the  dough  in  two  instalments  in  the  same  trough 
— there  is,  in  fact,  an  advantage,  as  the  sponge  flour  will  have  had  time  to 
soften,  and  get  to  work  more  kindly  before  the  full  quantity  is  worked  in 
in  the  dough. 

Character  of  Bread — Appearance — Almost  any  shape  of  loaf  is  well 
made  in  this  manner,  the  bread  is  bold,  and,  generally  speaking,  of  good 
appearance. 

Yield. — With  the  great  elasticity  of  the  system,  as  a whole,  the  yield 
varies  considerably  according  to  the  character  of  flours  used.  Taking  a 
general  average,  93  to  96  loaves  per  sack  is  a good  proportion.  If  an  excess 
of  hard,  strong  flour  is  used  in  order  to  get  more  bread  than  this,  the  flavour 
is  likely  to  suffer. 

Flavour. — One  of  the  essential  characters  of  this  type  of  bread  is  that, 
if  well  made,  it  embodies  to  perfection  the  natural  flavour  of  the  flours, 
without  any  adventitious  characters  introduced  with  foreign  flavouring 
ingredients.  If  the  flours  are  well  selected,  both  for  sponge  and  dough,  there 
should  be,  on  the  one  hand,  an  absence  of  that  “ rawness  ""  characteristic  of 
under  fermentation,  and  of  any  harshness  resulting  from  destruction  of  all 
moisture  and  sweetness-conferring  constituents  by  over  fermentation. 

Texture. — The  bread  should  have  a good  pile,  crumb  even,  white  and 
silky,  with  full  sheen  on  the  fibre  of  the  bread. 

Colour. — The  crust  should  be  golden  brown,  without  foxiness  or  abnormal 
paleness.  In  the  crumb  the  colour  advantage  of  the  class  of  flour  used 
should  be  fully  developed. 


406 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Moisture. — Bread  made  in  this  manner  is  free  from  any  clamminess, 
and  may  easily  pass  over  the  line  into  harsh  dryness — this,  however,  is  a 
fault  that  should  not  occur,  rather  than  a necessity  of  the  method.  From 
the  very  even  sponginess  of  the  bread,  although  when  fresh  cut  it  may  be 
very  moist,  yet  it  tends  to  rapidly  dry  out  when  cut  slices  are  allowed  to  lie 
about.  But  when  properly  made,  this  bread  retains  its  moisture  in  the  uncut 
loaf  remarkably  well. 

Summary. — An  interesting  point  about  the  sponge  and  dough  method 
is  its  comparison  with  that  of  ferment  and  dough  ; both  have  their  advan- 
tages, but  that  just  described  for  most  purposes  has  the  preference.  Com- 
paring breads  made  by  the  two  methods,  ferment  and  dough  made  bread 
is  at  its  best  when  quite  fresh  ; wLile  suitably  made  sponge  and  dough  bread 
retains  its  eating  properties  considerably  longer. 

537.  Ferment,  Sponge,  and  Dough. — This  is  essentially  a combination 
of  the  tw^o  immediately  preceding  methods,  and  is  frequently  chosen  where 
brewers’  yeast  is  used,  as  the  ferment  exerts  a specific  and  valuable  action 
on  yeast  of  that  description.  A ferment  being  employed,  instead  of  adding 
yeast  to  the  sponge  direct,  a description  of  the  sponge  and  dough  method 
applies  also  to  this  process.  One  of  its  advantages  is  that  it  permits  more 
individuality  in  character  of  the  bread  than  where  a compressed  yeast  is 
used,  which  can  be  freely  purchased  by  any  baker.  When  by  means  of  a 
“ ferment  ” the  baker  practically  makes  his  own  yeast,  he  becomes  liable 
to  the  risks  as  well  as  the  advantages  accruing  from  being  his  own  yeast 
manufacturer.  This  method  is  frequently  associated  with  the  manufacture 
of  patent  yeast  by  the  baker  himself.  The  whole  of  the  various  methods 
previously  described  are  susceptible  of  the  same  modifications,  except 
perhaps  tight,  off-hand,  crusty  bread  doughs  which  would  rise  with  diffi- 
culty under  the  action  of  this  usually  comparatively  weak  yeast. 

538.  Present  Review  of  Bread-making  Methods,  Callard. — ^Mr  Callard 
has  kindly  furnished  the  authors  with  the  following  note  on  his  paper  herein 
quoted  : — 

“ In  the  intervening  sixteen  years  since  writing  the  paper  referred  to,, 
considerable  changes  have  taken  place  in  the  general  practice  of  bread- 
making. In  the  main  these  changes  are  due  to  two  causes  : (1)  the  great 
improvement  in  the  preparation  of  compressed  yeasts,  and  (2)  the  advance 
of  English  milling. 

(1)  Compressed  yeasts  to-day  are  of  a much  higher  quality  and  lower 
price  than  when  that  paper  was  written.  They  are  much  less  susceptible 
to  atmospheric  changes,  and  consequently  are  less  damaged  in  transit. 
They  are  stronger,  or  ,to  be  more  correct,  they  mature  quicker  in  the  dough 
than  did  yeasts  of  years  ago.  This  has  enabled  bakers  to  dispense  with 
ferments  or  sponges,  and  the  system  of  straight  doughs  has  become  almost 
universal.  Where  the  sponge  and  dough  system  survives  to-day,  it  is  on 
account  of  attachment  to  old  methods  and  not  because  of  the  necessity  of 
so  treating  the  yeast. 

(2)  The  English  miller  has  for  many  years  aimed  at  producing  a flour 
of  an  all-round  quality,  avoiding  harshness  on  the  one  extreme  and  soft- 
ness on  the  other.  He  has  tried  to  produce  a flour  capable  of  being  used 
alone.  ‘ In  this  he  has  succeeded,  with  the  result  that  the  flours  of  to-day 
are  more  mellow  than  in  the  past  and  require  less  softening  during  the  process 
of  fermentation. 

The  straight  dough  system  (off-hand)  with  IJ  lbs.  to  IJ  lbs.  of  yeast, 
taking  about  5 hours  to  the  oven,  is  general.  This  occupies  the  same  rela- 
tive place  at  present  as  the  sponge  and  dough  did  when  the  paper  was 
published.  Here  and  there  a modified  ferment  is  used  in  conjunction  with 


BREAD-MAKING. 


407 


it  to  give  the  yeast  a start.  When  the  desire  is  to  shorten  the  time  the  yeast 
is  increased,  in  fact  with  automatic  plants  6 lbs.  of  yeast  is  used  to  the  sack, 
and  the  dough  passes  from  the  mixer  to  the  divider  without  delay.''  {Personal 
Communication,  October,  1910.) 

539.  Flour  Barm,  Sponge,  and  Dough — Scotch  System. — The  flour  barm 
is  practically  a combination  of  the  making  a baker's  malt  and  hop  yeast 
with  a slow,  scalded  flour  ferment.  The  preparation  of  the  flour  barm 
has  been  fully  described  in  the  earlier  part  of  this  work,  page  249. 

Type  of  Bread  made  hy  Method. — This  is  the  well-known  close-packed 
Scotch  brick,"  being  a high  and  comparatively  narrow  loaf,  prepared 
from  tough,  hard  flour  of  the  highest  class. 

Flours  Used. — In  sponges,  strong  patents  or  straight  grades  from  Duluth 
or  Russian  wheats.  In  doughs,  winter  Americans  and  softer,  but  still 
tough,  home-milled  flours. 

Sponges. — These  are  known  as  “ half  " or  “ quarter  " sponges,  and 
consist  of  either  the  half  or  quarter  of  the  w4iole  liquor  employed  to  the 
sack  of  flour.  The  requisite  quantity  of  flour  barm  is  taken,  for  which,  how- 
ever, distillers'  yeast  may  be  substituted  without  materially  altering  the 
character  of  the  bread.  About  6 lbs.  of  salt  are  used  to  the  sack,  one-sixth 
of  which  goes  into  the  sponge. 

Doughs. — These  are  made  in  the  usual  way,  but  it  is  customary  to  give 
the  dough  a very  thorough  working  after  it  has  laid  some  time.  One  of 
the  most  suitable  ways  of  doing  this  is  by  passing  the  dough  repeatedly 
through  a dough-brake. 

Economic  Advantages  and  Disadvantages. — The  cost  of  production  is, 
according  to  the  views  of  the  Scotch  baker,  very  low,  as  he  views  the  yeast 
as  costing  him  very  little,  the  flour  used  coming  back  into  the  bread.  This 
is  not  quite  correct,  because  a certain  portion  must  have  been  changed 
into  alcohol  and  carbon  dioxide  during  fermentation  ; and,  again,  the  labour 
of  preparation  must  cost  something. 

Character  of  Bread — Appearance. — The  appearance  is  attractive,  the 
loaves  are  high,  and  the  sides,  where  they  have  been  separated  from  each 
other,  have  a very  smooth,  silky  appearance. 

Yield. — Large,  the  character  of  the  flours  used  permitting  this,  and 
also  the  fact  of  most  of  the  bread  being  close  packed.  An  average  yield 
in  a large  factory  has  for  some  months  been  as  much  as  10 1 quarterns  per 
sack. 

Flavour. — Characteristic,  and  marked  by  the  presence  of  a decided 
acidity  of  pure  and  pleasant  taste,  due  largely,  if  not  entirely,  to  the  pre- 
sence of  lactic  acid.  The  large  quantity  of  salt  used  gives  a saline  char- 
acter to  the  taste,  immediately  recognised  by  the  English  palate,  which 
also  usually  misses  the  sweetness  generally  found  in  the  best  qualities  of 
bread  made  in  the  south. 

Texture. — Scotch  bread  has  the  perfection  of  texture,  being  silky  with 
large  bulk  and  pile,  and  small  regular  holes  of  aeration. 

Colour. — The  long  system  of  baking  employed  gives  the  crust  a dark 
brown  colour,  and  hence  the  bloom  of  crust  is  not  such  an  important  char- 
acteristic as  in  south  country  crusty  bread.  The  crumb  is  exceedingly  white, 
but  has  comparatively  rarely  the  creamy,  yellow  bloom  seen  in  some  of  the 
bread  made  in  other  localities.  The  sheen  of  the  bread  is  remarkably 
distinct,  the  holes  having  a rich,  full  glaze. 

Moisture. — Good,  and  the  bread  keeps  remarkably  well. 

540.  Modern  Bread-making  Practice. — It  has  been  the  wish  of  the  authors 
to  give  as  representative  an  account  as  practicable  of  the  modes  of  bread- 
making at  present  generally  adopted.  With  this  object  in  view  they  wrote 


408 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


personally  to  a large  number  of  representatives  of  the  baking  trade,  and 
have  been  favoured  with  the  following  replies.  Their  best  thanks  are  due, 
and  are  here  tendered,  to  those  gentlemen  who  have  so  kindly  assisted  them. 
The  following  printed  list  of  particulars  required  was  forwarded  and  answers 
requested  ; which  should  as  well  as  possible  give  the  general  practice  of  the 
district  rather  than  the  methods  of  individuals.  It  was  also  pointed  out 
that  no  information  was  wished  that  would  be  in  the  nature  of  trade 
secrets  : — 

General  Bread-making  Processes. 

Employed  in  (town  or  district)  : — 

I.  Flours  used,  how  selected  and  blended,  and  in  what  proportions. 
(Varieties  or  types  of  flour,  and  not  names  of  millers,  are  desired.) 

II.  Nature  and  type  of  yeast  used. 

III.  Bread  improvers  (if  any),  including  malt  extract,  sugars,  fat,  milk, 
mineral  salts. 

IV.  Bread-making  processes,  including  quantities  of  ingredients,  flour, 
yeast,  salt,  bread  improvers,  milk,  water,  etc.  Length  of  time  of  fermenta- 
tion, system,  and  temperatures.  How  doughs,  etc.,  are  handled. 

V.  Nature  and  type  of  bread  produced. 

VI.  Remarks. 

Replies. 

541.  Birmingham,  hy  Mr.  Thomas  Fletcher. — 

I.  Comparatively  little  foreign  flour  is  now  used,  but  almost  exclusively 
English  milled  flour,  and  mostly  from  Birmingham  and  surrounding  dis- 
trict. The  large  port  millers  have  a good  share  of  business  here,  however. 
The  varieties  of  flour  used  are  first  and  second  patents  and  seconds  flour. 
Not  much  blending  is  necessary. 

II.  Most  of  the  prominent  types  of  yeast  are  used  here. 

III.  Bread  improvers  (chiefly  malt  flour)  are  extensively  used.  Fat 
of  some  kind  is  being  added  by  some  bakers  to  the  best  quality  bread,  malt 
extract,  milk,  etc.,  being  now  limited  to  varieties  of  brown  or  whole-meal 
bread. 

IV.  The  system  of  straight  doughs  is  almost  exclusively  adopted  now. 
The  average  time  occupied  from  start  to  finish  extends  from  four  to  seven 
or  eight  hours,  and  the  quantity  of  yeast  used  is  varied  accordingly. 

V.  Crusty  cottages,  and  split  batch,  form  the  major  proportion  of 
bread  sold.  Pan  loaves,  round  and  oblong  in  shape,  are  produced  in  lesser 
quantity. 

542.  Brighton,  by  Clark’s  Bread  Co.,  Ltd. — 

I.  Mostly  English  milled  flour,  comparatively  little  foreign  compared 
with  twenty  years  ago,  during  which  time  there  has  been  a marked  general 
improvement  in  the  standard  of  quality.  Information  as  to  other  Arms’ 
exact  mixtures  and  methods  of  blending  not  readily  obtainable.  The 
principle  adopted  by  the  writers  lias  been  the  careful  selection  of  flours  for 
absolute  purity  and  maximum  nutritive  value.  In  pursuance  of  this 
policy  they  select  flours  which  are  unbleached  and  free  from  all  mineral 
additions. 

II.  Distillers’  compressed  yeast. 

III.  Improvers  not  very  largely  used,  the  principal  ones  being  malt 
extract,  and  to  a lesser  degree  malt  flour. 

IV.  Straight  and  fairly  tight  doughs  are  now  almost  universal  in  this 
district.  Salt  about  3J  lbs.  to  the  sack.  Short  system  of  fermentation, 
from  4 to  6 hours  ; yeast  from  2 lbs.  to  I lb.  The  writers  make  it  their 
endeavour  to  arrange  the  fermentation  so  as  to  get  thorough  ripening  of 


BREAD-MAKING. 


409 


the  gluten  of  the  flour  and  consequent  digestibility  without  any  approach 
to  acidit}^  or  overworking.  The  doughs  are  hand-made  in  the  smaller 
bakeries,  while  in  the  larger  more  or  less  complete  machinery  installations 
have  been  made.  These  include  kneading,  dough-dividing,  and  automatic 
moulding  machinery.  Ovens  used  are  of  various  types,  principally  side- 
flue,  and  steam  drawplate  ovens. 

V.  Mostly  crusty  cottage  and  coburg  2-lb.  loaves.  Usually  well  baked. 

543.  Crewe  and  District,  by  Mr.  W.  J.  Wilding. — 

I.  Practically  all  flours  used  are  made  from  blended  w4ieats,  chiefly  Plate 
and  Russian  (various  types),  English,  Canadian,  Australian  and  American, 
winter  wheats.  But  it  largely  depends  on  the  world’s  harvest.  We  are 
fortunately  situated  near  to  Liverpool,  which  gives  to  the  miller  a better 
advantage  than  one  situated  farther  inland,  and  then  we  have  the  large 
Liverpool  mills  turning  out  first-class  blended  flours  ready  to  use  without 
further  mixtures. 

II.  All  bread  produced  in  the  district  is  made  with  distillers’  yeast. 

III.  I do  not  think  there  are  much  “ improvers  ” used  besides  sugar 
and,  in  some  cases,  a little  malt  extract,  except  milk  and  lard  to  fancy  breads. 

IV.  We  have  several  systems  in  use,  each  firm  using  the  one  best  adapted 
to  his  class  of  business  and  convenience  of  working.  For  instance,  one  large 
firm  works  on  the  sponge  principle,  both  long  and  short  ones,  the  former 
being  set  in  the  afternoon  ready  for  night  w^ork,  and  the  latter  later  to 
follow  on.  Others  make  all  straight  doughs,  including  the  writer,  who  uses 
from  1|  lbs.  to  2 lbs.  yeast. 

Tin  Bread. — 1 lb.  sugar  (beet  preferred),  SJ  lbs.  salt,  16  gallons  water  or 
more,  280  lbs.  (flour  first  patents). 

Dough  when  made  to  be  80-84°  F.,  according  to  the  weather.  Let 
stand  1 J hours  w'ell  handed  up,  and  should  be  ready  to  tin  up  2J  to  3 hours 
after  making  into  dough,  baked  in  oven  at  400°  F.  after  well  proving. 

Cottage. — 2 lbs.  yeast,  SJ  lbs.  salt,  1 lb.  sugar  (beet),  280  lbs.  flour  (best 
patents). 

Dough  when  made  to  be  80-82°  F.  Cut  back  twice  and  should  be  ready 
to  scale  off  in  hours  after  mixing.  Scaled  and  handed  up  in  boxes,  proved 
and  moulded,  proved  again  and  set  in  oven  at  480°  F.  or  near. 

V.  Varies  from  the  well  proved  tin  to  the  close-set  crumby  loaf.  About 
equal  quantities  of  tin  and  cottage  are  made,  but  the  majority  of  the  bread 
produced  is  seconds  quality. 

544.  Eastbourne,  by  Mr.  G.  B.  Soddy. — 

I.  Principally  town-milled  flour,  average  quality,  “ whites,”  though  in 
some  cases,  a higher  grade  is  used. 

II.  Distillers’  compressed  yeast. 

III.  Malt  and  sugar. 

IV.  Straight  doughs,  usually  fairly  tight  (about  14  gallons  of  water  per 
sack).  Salt,  about  3 lbs.  to  the  sack.  Short  process  of  fermentation  gener- 
ally in  use.  Doughs  are  invariably  well-finished,  i.e.,  carefully  handed  up 
and  moulded.  Dough  is  well  baked. 

V.  Crusty  bread,  well  finished,  of  good  appearance,  and  quality  generally 
very  good. 

VI.  The  above  generally  represents  the  methods  and  results  achieved 
in  this  towm.  There  are  a few  cases  where  a low  grade  flour  is  used  and 
where  the  workmanship  is  not  good,  but  these  are  the  exception,  not  the 
rule. 

545.  Leeds  and  District,  by  Mr.  C.  H.  Slack. — 

I.  The  flours  used  are  principally  those  supplied  by  the  port  millers, 


410 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


both  on  the  east  and  west  coasts,  the  baker  buying  the  particular  grade 
that  happens  to  suit  his  requirements. 

In  some  cases  more  than  one  grade  of  a particular  miller’s  flour  may  be 
used  and  the  two  blended,  or  the  flours  from  two  or  more  mills  may  be 
treated  in  the  same  manner,  more  often  than  not  without  any  regard  to 
definite  proportions,  the  flour  being  bought  more  through  some  monetary 
consideration  than  for  any  specific  purpose. 

The  varieties  of  flours  are  both  of  the  medium  strength  and  soft.  Home 
baking  being  largely  carried  on,  and  flour  for  this  purpose  being  almost 
entirely  retailed  by  the  grocer  to  the  housewife,  the  bulk  of  the  flour  used 
is  supplied  with  that  particular  object  in  view,  viz.,  to  satisfy  the  demand 
for  whiteness  which  the  housewife  usually  considers  to  be  the  criterion  of 
quality  ; consequently,  the  baker,  more  to  meet  this  demand  of  the  home 
baker  than  from  any  other  reason,  deals  principally  with  the  miller  who  may 
supply  this  type  of  flour. 

Since  many  of  the  millers  have  migrated  coastwards,  and  with  increased 
areas  to  distribute  their  products  over,^  there  has  been  more  uniformity  in 
the  supply,  and  the  general  quality  has  improved.  A few  years  ago  parcels 
of  American  spring  and  winter  flour  were  to  be  bought,  and  were  used  prin- 
cipally by  wholesale  bakers,  who  blended  with  the  products  of  local  mills, 
in  varying  proportions,  with  the  idea  of  strengthening  the  mixture,  but 
to-day  one  rarely  meets  with  any  samples  being  offered.  Parcels  of  Aus- 
tralian, Russian,  Argentine,  and  French  are  sometimes  to  be  met  with,  which 
are  offered  by  importers  or  agents  ; bakers,  however,  usually  do  not  care 
to  touch  them  unless  there  happens  to  be  some  special  advantage  in  price. 
The  J ewish  bakers  as  a rule  use  lower  grades  than  the  average  baker,  quality 
not  being  of  as  much  matter  as  price. 

II.  The  yeast  used  is  principally  distillers’,  both  pure  and  mixed  ; though 
pure  is  mostly  in  use,  and  is  both  of  the  quick  and  slow  working  type. 

III.  With  regard  to  bread  improvers  those  in  most  general  use  are  some 
kind  of  malt  extract,  sugars,  glucose,  fats,  cooking  oils,  milk,  fresh  and  in 
the  form  of  powder  ; and  though  not  extensively  used,  there  are  cases  on 
record  of  the  use  of  calcium  phosphate,  calcium  sulphate,  cream  of  tartar, 
and  bi-carbonate  of  soda. 

IV.  The  methods  employed  are  much  the  same  as  in  other  parts  of  the 
country. 

Among  most  bakers  in  anything  like  a large  way  of  business,  the  doughs, 
whether  made  by  hand  or  machine,  are  in  sack  batches  or  multiples  of  the 
same,  and  extends  over  periods  varying  from  1 to  12  hours  with 
quantities  of  yeast  varying  from  lb.  to  7 lbs.  per  sack. 

Yeast  at  the  rate  of  5 lbs.  per  sack  is  quite  in  common  use  among  smaller 
bakers,  while  in  small  breads  the  rate  per  sack  is  much  higher. 

The  off-hand  process  is  the  one  most  generally  followed,  sponge  and 
dough,  and  ferment  and  dough  processes  are  rarely  heard  of  except  in  the 
case  of  small  bread  and  rolls. 

The  use  of  the  thermometer  in  bread-making  operations  is  not  so  fre- 
quent as  is  commonly  supposed.  The  average  journeyman  baker  is  not 
sufficiently  versed  in  the  line  he  should  take  in  the  event  of  his  doughs 
being  warmer  or  colder  than  he  may  have  calculated,  and  therefore  the 
use  of  the  thermometer  is  more  or  less  ignored.  But  it  is  invariably  found 
that  where  the  baker  has  had  the  advantage  of  technical  instruction,  the 
thermometer  is  much  more  appreciated,  and  the  resultant  bread  is  of  a more 
regular  and  uniform  character. 

While  machinery  is  being  more  generally  adopted,  there  are  few  bakeries 
where  anything  like  an  automatic  bread-making  plant  is  in  use ; all  types 
of  mixers  are  employed,  but  the  rotary  type  preponderates.  Gas  engines. 


BREAD-MAKING.  411 

have  given  place  to  the  more  convenient  electric  motor,  especially  where 
room  is  of  the  first  consideration. 

The  following  are  actual  processes  in  general  use  : — 

1.  280  lbs.  flour,  lbs.  yeast,  3Jlbs.  salt,  8 to  16  oz.  malt  extract,  56  to 
60  quarts  of  water.  Dough  80°  to  84°  F. ; 4 hours  from  making  to  oven  ; 
cut  back  at  1 hour,  tabled  at  2 to  2J  hours. 

2.  280  lbs.  flour,  4 lbs.  yeast,  2J  lbs.  salt,  8 oz.  malt  extract,  60  quarts 
water.  Dought  90°  F.  ; 2 hours  from  making  to  oven,  including  one  good 
kneading. 

3.  280  lbs.  flour,  60  quarts  water,  1 J lbs.  yeast,  1 lb.  malt  extract,  3J  lbs. 
salt.  Dough  90°  F. ; 5 hours  to  oven  ; cut  back  at  2i  hours. 

4.  280  lbs.  flour,  64  quarts  water,  2J  lbs.  yeast,  3|  lbs.  salt,  | lb.  malt 
extract.  Dough  86°  F. ; 4J  hours  to  oven,  including  one  cut  back  at  2 hours. 

5.  280  lbs.  flour,  56  quarts  water,  2J  lbs.  yeast,  2J  lbs.  salt,  | lbs.  malt 
extract.  Dough  80-82°  F. ; 4 hours  to  oven,  including  two  cuts  back. 

All  the  above  were  made  both  by  hand  and  machine  and  produced  fine 
flavoured  commercial  bread.  The  types  of  flour  used  were  first  and  second 
patents.  Among  small  bakers  the  following  are  fair  samples  : — 

1.  14  lbs.  flour,  3 quarts  water,  2 oz.  yeast,  2 oz.  salt,  J oz.  malt.  Dough 
80-86°  F. ; 4 hours  from  finished  making  to  oven.  Hand  made,  and  pro- 
duced bread  of  beautiful  texture  and  flavour. 

2.  14  lbs.  flour,  3 quarts  water,  3 oz.  salt,  1 oz.  malt,  3 oz.  yeast.  Dough 
82°  F. ; 3 hours  50  minutes  from  making  to  oven,  including  two  cuts  back. 

3.  28  lbs.  flour,  6 quarts  water,  8 oz.  yeast,  6 oz.  salt,  2 oz.  malt.  Dough 
80°  F. ; 3 hours  to  oven.  Samples  of  bread  made  by  this  method  have 
often  been  in  my  hands,  and  from  the  appearance  of  the  bread  only  it  was 
perfect  in  texture  and  extraordinary  in  colour.  Investigation  by  means  of 
carefully  made  comparative  tests  showed  the  use  of  milk  powder,  both 
skim  and  full  cream. 

V.  The  type  of  bread  made  is  mostly  of  the  tin  variety,  but  cottages, 
coburgs,  cakes,  whole-meal,  wheatmeal,  malt  and  the  bulk  of  the  proprietary 
breads  are  also  made  in  varying  quantities,  and  in  an  extraordinary  number 
of  weights  and  sizes,  from  12  oz.  to  8 lbs. 

546.  Leicester,  by  Mr.  W.  T.  Callard. — 

I.  A very  small  proportion  of  foreign  made  flour  is  used.  Supplies 
are  principally  from  the  port  millers  ; midland  millers  supply  about  one- 
tiiird  of  flour  used  in  good  seasons. 

II.  Compressed  yeast  entireh^ 

III.  Sugar,  general ; malt  extract  to  a limited  extent. 

IV.  Almost  entirely  straight  dough  ; IJ  to  1 J lbs.  yeast  to  sack  ; 3 Jibs 
salt.  ]\Iilk  not  at  all  except  for  bona-fide  milk  bread. 

Water  14  gallons  to  sack  of  English  local  milled  flour 
,,15  ,,  ,,  port  milled  flour 

„ 16  ,,  ,,  ,,  ,,  ,,  for  tin  bread. 

Doughs  are  usually  machine  made.  The  drum  type  is  very  general  for 
hand  and  power.  Dividers  are  not  in  general  use,  moulding  machinery  is 
employed  by  one  firm  only. 

V.  Mainly  cottage  and  tin  bread. 

VI.  Three  qualities  are  usual  with  the  larger  bakers.  The  quality  has 
much  improved  in  recent  years. 

547.  Liverpool,  by  Messrs.  Geo.  Lunt,  Sons  & Co.,  Ltd. — 

I.  English,  American,  Continental,  and  also  Colonial  flours  used.  Se- 
lection, according  to  requirements  and  prices  ruling.  Should  foreign  flour 
be  relatively  cheap  then  special  efforts  are  made  to  use  same,  blending 
strong  Americans  with  weaker  English  or  Colonial. 


412  THE  TECHNOLOGY  OF  BREAD-MAKING. 

II.  Distillers’  yeast. 

III.  Bread  improvers  not  generally  used. 

IV.  Straight  doughs,  4 to  6 hours.  Salt  generally  3 lbs.  per  sack, 
varying  quantities  of  yeast  and  water  according  to  variety  of  bread,  tem- 
perature various,  doughs  cut  back  either  by  hand  or  aerating  machine. 

V.  Tin  and  oven  bottom  (upset),  two  or  three  grades. 

Report  by  another  Liverpool  firm. — 

I.  Principally  Liverpool  milled  flour,  which  as  a rule  requires  no  bleaching. 

II.  Practically  all  distillers’  yeast,  with  the  exception  of  a few  small 
bakers  who  still  use  brewers’  barm. 

III.  Malt  extract  and  dry  malt  flour.  Sugar,  fat,  and  milk  are  rarely  used 
in  ordinary  household  quality  bread  but  are  largely  used  in  best  or  milk 
bread.  Mineral  salts  are  coming  into  use  under  various  names  as  bread 
improvers. 

IV.  Bread  is  principally  made  on  a straight  dough  process  allowing  from 

5 to  6 hours  in  dough. 

Quantities  taken  are  : — 

280  lbs.  flour. 

150  lbs.  water  for  tin  or  pan  bread. 

130  lbs.  water  for  oven-bottom  or  crumby  bread 

IJ  lbs.  yeast. 

3J  lbs.  salt. 

1 lb.  malt  extract. 

The  resultant  dough  to  be  of  a temperature  of  78-80°  F.  The  dough 
is  left  to  prove  for  3 hours,  then  cut  back,  let  prove  for  another  hour, 
turned  over  and  scaled  in  another  hour.  It  is  scaled  by  machinery,  allowed 
to  prove  for  20  minutes,  then  moulded  in  its  required  shapes,  allowed 
to  stand  15  minutes,  and  then  put  into  the  oven  and  baked  at  a tem- 
perature of  500°  F.  for  tin  heat,  and  450°  F.  for  crumby. 

V.  Liverpool  bread  has  for  many  years  been  divided  into  two  main 
types  of  tin  bread  and  oven-bottom  bread.  The  proportion  of  tin  bread 
gradually  increases.  There  has  been  a decided  tendency  during  recent  years 
on  the  part  of  the  public  to  buy  smaller  loaves  than  formerly.  At  one  time 

6 and  8-lb.  loaves  were  greatly  in  demand  ; now  there  are  very  few  made. 
Latterly,  also,  a light  crumby  loaf  seems  to  be  coming  into  favour. 

548.  London,  West  End,  by  Messrs.  Bouthron  & Co. — 

I.  Flours,  2 parts  town  whites,  1 part  London  top-price  patents,  I part 
country  supers. 

II.  Compressed  distillers’  yeast. 

III.  Malt  flour. 

IV.  Ferment  and  dough.  Ferment  set  at  85°  F.,  adding  1 lb.  (per  sack) 
of  scalded  malt  flour.  Yeast,  I lb.  per  sack.  Dough — 1 sack  flour,  water 
making  total  liquor  up  to  14  gallons,  temperature  110°,  salt,  3 lbs.  Tem- 
perature of  dough,  84°.  Dough  cut  back  at  4 hours,  scaled  at  5J  hours, 
in  oven  at  6J  hours.  Start  to  finish,  9 hours. 

V.  Crumby  bread  and  crusty  cottage. 

VI.  With  the  large  variety  of  breads  made,  the  various  doughs  neces- 
sarily differ  in  detail.  The  above  must  be  taken  as  an  outline  of  the  general 
system  followed. 

549.  Macclesfield,  by  Mr.  G.  B.  Gee. — 

I.  English  milled  flours. 

II.  Almost  universally  compressed  Continental  and  British  yeasts. 

IV.  Ferment  and  dough  ; water  about  17  gallons  per  sack  for  tin  bread, 
and  about  13  gallons  per  sack  for  oven-bottom  bread. 


BREAD-MAKING.  413 

V.  Largely  tin  bread  of  light  consistency.  A small  proportion  of  cottage 
and  other  shapes. 

550.  Malvern,  by  Mr.  T.  Percy  Lewis. — 

I.  Good  grade  millers’  blend,  very  little  imported  flour. 

II.  Distillers’  compressed  yeast,  Dutch  and  British. 

III.  Malt  extracts  and  malt  flour  only. 

IV.  All  small  bakers  use  half  sponge  ; larger  bakers,  off-hand.  to 
4 lbs.  of  salt  per  sack,  and  usually  1 lb.  malt  extract.  Most  ovens  are 
still  side-flue,  but  steam  patents  are  coming  into  favour. 

V.  Mostly  2-lb.  coburgs  (locally  termed  “ gullies  ”). 

VI.  The  class  of  bread  is  much  above  the  average  households  of  larger 
towns,  very  little  plain  tie  or  households  flour  being  used. 

551.  Manchester  and  Salford,  by^Mr.  A.  Worsley. — 

I.  Flour  milled  in  England  from  foreign  wheat  (Australia,  Manitoba, 
Karachi,  Russia,  River  Plate),  selected  for  their  strength  and  bloom.  Most 
bakers  would  use  about  three  parts  of  this  with  one  part  of  English  milled 
flour  made  from  half  foreign  and  half  best  English  wheat,  and  used  for  the 
purpose  of  giving  sweetness,  flavour,  and  moisture  to  the  bread. 

II.  Distillers’  yeast. 

III.  Any  bread  improver,  but  mostly  malt  extracts,  used  for  the 
purpose  of  assisting  fermentation  and  making  the  dough  work  more  quickly 
and  regularly. 

IV.  Nearly  all  the  Manchester  and  Salford  ^bakers  use  a dough  mixer 
1 J or  2 sack  capacity.  They  make  a straight  dough  as  follows  : — 

280  lbs.  flour. 

IJ  lbs.  yeast  (IJ  or  If  lbs.  for  first  round) 
lbs.  salt. 

J to  1 lb.  bread  improver 

16 J to  18  gallons  of  water. 

Usually  the  dough  making  is  done  first  thing  for  the  day,  say  four,  six,, 
or  eight  batches  of  bread.  Temperature  of  water  for  first  round  about 
95°  and  reduced  to  85°  for  the  later  batches.  The  quantity  of  yeast  used 
is  also  reduced.  Length  of  time  about  4 hours.  Dough  knocked  down 
once. 

V.  Probably  85  per  cent.,  or  even  more,  of  the  bread  made  in  Manchester 
and  Salford  is  tin  bread,  the  remaining  10  or  15  per  cent,  being  cottages, 
cobs  and  brunswicks.  The  bread  is  of  good  quality  and  volume. 

552.  Nottingham,  by  Mr.  L.  E.  Turner. — 

I.  Eighty  per  cent,  of  the  flour  used  here  is  port  milled,  and  comes  from 
Hull,  York,  Grimsby  on  east  coast,  and  Liverpool  and  Bristol  on  the  west. 
The  remaining  20  per  cent,  is  divided  between  the  smaller  country  mills 
and  the  larger  inland  ditto. 

II.  Dutch  yeast  is  used  principally  and  has  by  far  the  largest  sale.  No 
brewers’  or  patent  yeast  is  now  used. 

III.  Only  knows  of  malt  extract  being  used,  and  that  not  in  large  quan- 
tities. Milk  and  fats  are  used  in  fancy  breads. 

IV.  The  great  bulk  of  bread  is  now  made  on  the  short  process — straight 
doughs,  etc.  280  lbs.  flour,  IJ  lbs.  yeast,  3J  to  4 lbs.  salt,  16 J gallons  of 
water  at  95°  F.  Dough  is  made  and  after  2J  hours  is  cut  over,  left 
another  hour,  and  is  then  scaled  off  into  tins  and  proved  about  20 
minutes  and  is  then  baked.  For  cottage  bread  only  134  gallons  of  water 
are  used,  and  after  the  dough  is  scaled,  the  pieces  lie  for  20  minutes  in 
boxes  to  prove  before  being  moulded  up  for  the  oven. 

V.  Two- thirds  of  the  bread  made  here  is  tin  bread  in  2-lb.  loaves,  one. 


414 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


third  oven-bottom,  also  2 lbs.,  in  cottage  and  coburg  shapes,  three-quarters 
of  them  the  latter. 

VI.  All  the  larger  bakeries  use  machinery,  and  most  of  the  smaller 
ones  have  small  plants  also,  hence  the  popularity  of  the  straight  dough 
system.  The  great  competition  among  bakers  causes  them  to  use  more  water 
than  is  good  for  obtaining  the  best  results  from  a quality  standpoint. 

553.  Plymouth,  by  Mr.  Henry  J.  R.  Matthews. — 

I.  One-fourth  American  spring  wheat  patent,  three-fourths  English 
milled  patent. 

II.  Dutch  compressed  yeast. 

III.  Malt  extract.  Dried  milk  powder. 

IV.  Four  hours'  sponge,  2 lbs.  yeast,  3 lbs.  salt,  J lb.  malt  to  the  sack  of 
flour.  Dough  made  and  allowed  to  lie  IJ  hours.  Temperature  for 
sponge,  90°  ; for  dough,  from  80  to  90°  F.  ; the  usual  temperature  of 
flour  being  from  75  to  80°  F. 

V.  Superflne  bread,  principally  2-lb.  loaves  of  various  shapes. 

VI.  Steam  drawplate  ovens  are  principally  used.  Bread  in  oven  50 
minutes,  temperature  480°  F. 

554.  Belfast,  by  Mr.  Geo.  Inglis. — 

I.  American  springs  and  winters,  and  United  Kingdom  blends,  mostly 
top  patents.  Bought  from  samples,  or  mill’s  brands,  and  blended  by  mixers, 
sifters,  and  conveyers  according  to  requirements. 

II.  Distillers’  compressed  yeast  (local  manufacture). 

III.  Great  diversity  of  practice,  many  Arms  only  using  these  in  fancy 
bread. 

IV.  Principally  sponge  and  dough,  but  straight  doughs  increasing.  Six 
to  ten  hour  sponges.  Mixers,  dividers,  moulding  machines,  provers,  and 
several  automatic  plants  in  use. 

V.  Mainly  2-lb.  square  batch  loaves,  also  cottage  and  pan  loaves,  and  a 
large  variety  of  small  kinds. 

' ' 555.  The  West  of  Scotland,  by  Messrs.  Montgomerie  & Co.,  Ltd.,  Glasgow. — 

•'  The  Quarter  Sponge  System. — The  first  part  of  the  process  is  the  doughing 
of  the  quarter.  Portions  of  flour,  water  and  salt  are  doughed  up  with  the 
total  quantity  of  barm.  The  usual  time  for  fermentation  is  from  10  to  1 5 
hours  at  this  stage.  The  temperature  of  the  water  is  regulated  to  suit 
the  time  the  quarter  has  to  be  on  the  road.  The  following  is  an  example  : — 

If  the  temperature  of  the  flour  is  64°,  the  bakery  74°,  the  barm  60°,  to 
lift  the  quarter  in  15  hours  the  water  should  be  80°. 

For  every  hour  less  than  15  hours  that  the  quarter  has  to  be  on  the  road, 
it  is  usual  to  raise  the  temperature  of  the  water  by  4°.  The  temperature 
of  the  quarter  when  lifted  should  be  about  84°. 

The  next  part  of  the  process  is  the  stirring.  In  the  stirring  more  flour, 
water  and  salt  are  stirred  into  the  quarter.  The  temperature  of  the  water 
varies  according  to  the  time  in  which  the  sponge  has  to  be  lifted.  If  in 
tlie  stirring  the  flour  is  66°  and  the  quarter  84°,  the  temperature  of  the  water, 
if  the  sponge  has  to  be  lifted  in  1 hour,  would  be  90°.  The  temperature  of 
the  water  should  be  decreased  by  10°  for  every  \ hour  longer  in  the  sponge. 
It  is  usual  to  raise  tlie  temperature  of  the  water  by  2°  for  every  degree  the 
quarter  is  below  84°,  and  vice  versa. 

When  it  has  turned  about  one  inch,  the  sponge  is  doughed  with  the  rest 
of  the  flour,  salt  and  water.  The  temperature  of  the  dough  should  be  about 
80°.  Tlie  water  used  in  the  dough  will  be  about  74°  if  the  flour  is  66®  and 
the  sponge  84°.  The  dough  is  allowed  to  lie  for  about  1 J to  1|  hours.  It 


BREAD-MAKING. 


415 


is  then  weighed  off  and  laid  into  cases,  where  it  is  allowed  to  lie  for  about 
15  minutes.  The  loaves  are  then  moulded  and  placed  in  cases  or  setting 
racks,  according  to  the  style  of  the  oven  in  use  ; in  cases  for  Scotch  ovens 
and  setting  racks  for  drawplate  ovens. 

The  loaves  are  baked  at  a temperature  of  from  400°  to  450°  Fahrenheit. 
The  time  occupied  in  baking  varies  from  IJ  to  2 hours,  according  to  the 
heat  of  the  oven  and  the  condition  of  the  dough. 

(Further  reference  is  made  to  Scotch  bread-making  methods  in  a sub- 
sequent part  of  this  chapter. 

556.  Cardiff  and  District,  by  Mr.  W.  J.  Travers. — 

I.  Mostly  English  milled.  Demand  for  American  Patents  greatly 
decreasing.  English  flour  is  now  blended  in  the  process  of  milling  to  suit 
local  requirements. 

II.  Distillers’  yeast. 

III.  Malt  extract  and  malt  flour  generally  used,  some  using  sugars  and 

fat. 

IV.  Dough  generally  consists  of  280  lbs.  of  flour,  14  gallons  water,  1 J 
lbs.  yeast ; according  to  time  and  general  conditions,  3J  to  4 lbs.  salt ; 
about  1 lb.  malt  extract  or  malt  flour.  Fermentation,  generally  short 
process,  from  3 to  6 hours.  Dough  generally  made  by  machinery. 

V.  All  shapes  of  bread  manufactured,  mostly  2 lbs.  in  weight  ; not  too 
much  proof,  as  the  public  like  a fairly  firm  and  close  loaf. 

557.  Toronto,  Ont.,  Canada,  by  The  Nasmyth  Co.,  Ltd. — 

I.  Hard  flour  milled  from  Manitoba  and  North-West  wheats.  Soft  flour 
chiefly  from  Ontario  fall  wheat.  Used  in  proportion  of  two  parts  hard  to 
one  part  soft,  and  four  strong  to  one  soft. 

II.  Vegetable  compressed  yeasts  used  almost  entirely,  though  there 
are  instances  of  malt  and  hops  yeasts  being  used  also. 

III.  The  first  four  are  largely  used  ; the  fifth  not  to  any  extent. 

IV.  Straight  doughs  taking  from  6 to  8 hours  to  the  table  ; 12  to  14  hour 
sponges  are  also  used.  The  following  are  quantities  for  two  types  of  bread — 

Real  Home  Made. — Flour,  784  lbs.  ; water,  420  lbs.  ; salt,  14  lbs.  ; 
cottolene,  17J  lbs.  ; yeast,  6 lbs.  ; malt  extract,  5J  lbs.  Temperatures  : 
Flour,  70°  ; bakehouse,  80°  ; water,  84°  ; dough,  82°  F. 

G.  Crust. — Flour,  972  lbs.  ; water,  520  lbs.  ; salt,  18  lbs.  ; cottolene, 
131  lbs.  ; yeast,  7J  lbs.  ; condensed  milk,  13  lbs.;  malt  extract,  5 lbs. 
Temperatures  : Flour,  70°  ; bakehouse,  80°  ; water,  86°  ; dough,  83  °F. 

Machinery  is  extensively  used.  Mixers,  dividers,  moulding  machines 
and  rounding-up  machines  are  used  in  the  larger  shops,  and  automatic 
provers  are  being  introduced.  The  quantity  of  hand-made  bread  is  small 
and  decreasing. 

V.  Tin  bread  almost  entirely.  Our  output  of  hearth  baked  bread  is 
less  than  three  per  cent,  of  the  total,  and  would  probably  represent  the 
average. 

558.  Cincinnati,  Ohio,  U.S.A.,  by  The  Banner  Grocers’  Baking  Co. — 

I.  Three  parts  Minnesota  patent  to  one  part  Kansas  hard  wheat. 

II.  Compressed  yeast. 

III.  Malt  extract,  sugar,  lard,  milk,  cornflour. 

IV.  Quantities  : 850  lbs.  flour,  525  lbs.  w^ater,  6J  lbs.  yeast,  I2|-  salt, 
20  lbs.  sugar,  17  lbs.  lard,  5 lbs.  milk  powder,  5 lbs.  malt  extract  and  25  lbs. 
cornflour. 

A short  time  ferment  is  made  with  the  yeast,  malt  extract,  part  of  the 
water,  and  the  cornflour.  This  is  added  to  the  dough  after  the  flour  is  in. 


416  THE  TECHNOLOGY  OF  BREAD-MAKING. 

The  temperature  of  the  dough  is  84°  F.,  and  the  time  from  mixer  to  bench  is 
5J  hours. 

V.  “ Buster  Brown  Bread.'' 

559.  Nappanee,  Indiana,  U.S.A.,  hy  Mr.  A.  F.  Hartman. — 

I.  Minnesota  spring  wheat  flour. 

II.  Compressed  yeast 

III.  Sugar  and  cotton-seed  oil. 

IV.  Straight  dough  from  the  following  quantities : 100  lbs.  flour. 
60  lbs.  water,  2 of  sugar,  1 J of  oil,  and  1 J of  salt.  Allowed  to  ferment  until 
the  dough  drops  in  centre,  is  then  cut  over,  stands  one  hour,  again  cut 
over,  and  after  1 J hours,  to  bench  and  baked  in  pans.  Dough  is  made  at 
80°,  being  240°,  less  the  heat  of  the  bakehouse  and  that  of  the  flour,  ta 
get  the  temperature  of  the  water.  The  fermented  dough  when  it  comes 
to  the  bench  is  at  80-82°  F. 

V.  String  or  pan  bread. 

VI.  This  system  makes  a very  fine  bread,  but  the  sponge  system  is. 
more  used  in  Indiana  than  is  that  of  straight  doughs. 

560.  Further  American  Recipes. — The  following  are  additional  American 
bread-making  recipes  kindly  furnished  by  the  Malt-Diastase  Company 
of  New  York. 


New  England  Bread,  Straight  Dough. 

Eight  lbs.  corn  flour  or  cereline  (flakes)  placed  in  mixer  with  4 gallons 
warm  water  ; run  it  for  a few  minutes,  adding  5 lbs.  (2  quarts)  malt 
extract.  Then  add — 

34  gallons  water  (90°  to  98°). 

2 gallons  milk. 

3J  to  4 lbs.  compressed  yeast. 

4 lbs.  sugar. 

6 to  8 lbs.  lard. 

9J  lbs.  salt. 

540  to  550  lbs.  flour  (3  parts  Minnesota  spring  patent,  1 part  winter 
wheat  or  Kansas). 

Dough  should  have  temperature  of  about  82°  to  84°.  Make  soft  dough. 
Push  down  when  well  raised  (3  to  3J  hours)  ; after  another  half-hour  before 
going  to  bench  cut  dough  over  and  let  rest  a half-hour  more,  if  time  allows  it. 

If  mush  is  preferred  to  meal  or  flakes,  take  40  to  50  lbs.  Treat  dough 
same  as  above.  In  place  of  milk  you  can  use  dry  milk  powder  and  suffi- 
cient extra  water. 

Don't  let  the  dough  get  too  ripe  the  first  time,  so  that  it  falls  by  simply 
pushing  your  hand  into  it.  It  must  still  have  sufficient  resistance,  that  is, 
lias  to  be  cut  down.  Never  use  water  too  hot  ; it  would  be  better  to  warm 
tlie  flour  in  winter,  and  chill  the  liquid  used,  by  running  through  a colander 
with  broken  ice  in  hot  weather.  A little  more  yeast  is  better  than  setting 
dougli  too  warm. 

With  Sponge. 

Same  as  above.  Use  17  gallons  of  the  water  for  the  sponge,  the 
remainder  for  the  dough.  Be  sure  and  mix  mush  or  flakes  in  mixer  first 
before  mixing  dough,  and  use  only  3 lbs.  of  compressed  yeast. 

Note. — The  substance  spoken  of  as  cereline  consists  of  cereal  matter, 
gelatinised,  rolled  into  flakes,  and  dried.  Analogous  substances  are  known 
in  this  country  as  flaked  rice,  flaked  tapioca,  etc.  Mush  consists  of  corn 
flour,  gelatinised  into  a paste  by  hot  water  (3  lbs.  of  the  flour  to  a gallon  of 
water. ) 


BREAD-MAKING. 


417 


Home-Made  Bread,  for  Sponge. 

5 gallons  water. 

14  ozs.  yeast  (in  summer  12  ozs.  are  sufficient), 

70  lbs.  flour. 

Water  can  have  98°  to  100°  according  to  flour.  Sponge  mixed  should  be 
at  least  84°. 


For  Dough. 

22  quarts  water. 

J quart  malt  extract. 

J lb.  sugar. 

20  lbs.  mush  (or  equivalent  in  water  and  flakes). 

1 to  IJ  lbs.  lard. 

70  lbs.  flour. 

3 lbs.  salt. 

When  mixed,  add  about  J lb.  oil,  so  dough  will  come  out  of  mixer  smooth. 


Domestic  Bread,  with  Ferment. 

Make  sponge  with  5 gallons  ferment,  J lb.  salt  and  sufficient  flour. 

When  it  falls  the  first  time  add — 

10  quarts  water. 

IJ  lbs.  salt. 

1 lb.  malt  extract. 

IJ  lbs.  lard. 

Take  ferment  for  sponge  at  85°  ; water  for  the  dough  at  82°  to  84°. 
Let  dough  come  twice. 

This  dough  can  stand  a strong  flour,  but  use  some  winter  patent  with 
it.  If  you  wish  bread  to  be  a little  sweeter,  add  1 J to  2 lbs.  brown  sugar. 

Ferment, — To  one  peck  washed  potatoes  (with  skin)  add  sufficient  water 
to  cover  them  well.  When  boiled  soft  put  in  tub,  and  mash  with  3 lbs. 
flour  ; add  gradually  the  potato  water  and  more  plain  water  to  make  5 
gallons.  When  cooled  to  80°  add  f pint  stock  yeast  or  3 ozs.  of  com- 
pressed yeast.  Set  away  and  let  rest  undisturbed  for  about  10  hours  until 
it  falls. 

Cottage  Bread,  for  Fine  Retail  Trade. 

Set  soft  sponge  with  J lb.  compressed  yeast,  2J  gallons  water  (82°  to  84^^ 
when  mixed)  and  sufficient  flour.  When  raised  the  second  time  (about  3 
hours)  add — 

2 gallons  milk. 

6 quarts  water  at  the  same  temperature. 

21  to  24  ozs.  salt. 

1 lb.  lard. 

4 ozs.  butter. 

I lb.  malt  extract. 

J lb.  sugar. 

Sufficient  flour. 

A mixture  of  two  barrels  strong  Minnesota  patent  and  half  barrel  rich 
winter  patent  gives  best  results. 

Milk  Bread. 

9 gallons  water. 

1 gallon  milk. 

1 lb.  yeast. 

16  lbs.  mush  (or  2 gallons  extra  water  and  10  lbs.  maize  flakes). 

2 lbs.  lard. 


' EE 


418 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


1 lb.  malt  extract. 

2 lbs.  sugar  (or  more  malt  extract  and  no  sugar). 

3 lbs.  salt. 

140  to  145  lbs.  flour  (same  quality  as  for  New  England). 

Quaker  Bread. 

10  gallons  water  (75°  to  80°). 

12  to  14  ozs.  compressed  yeast. 

2J  to  2J  lbs.  salt. 

1 lb.  lard. 

12  ozs.  malt  "extract  (or  J lb.  malt  extract  and  2 lbs.  sugar). 

10  -12  lbs.  of  mush,  corn  flour  or  cereline  flakes  (with  extra  water) 
can  be  added  to  reduce  cost  wdthout  affecting  quahty. 

Mix  into  slack  dough  ; use  rather  strong  mixture  of  flour,  say  three 
parts  spring  patent,  one  part  winter  patent ; part  Kansas  wheat  may  be 
added.  Let  dough  rest  first  for  3 J to  4 hours.  Push  down  once,  let  come 
up  again.  Don't  give  too  much  proof  after  moulded  up.  Bake  in  double 
loaves  in  tins — square  tins. 

In  winter  this  dough  must  be  set  from  5°  to  10°  warmer,  and  a little  more 
yeast  may  be  taken.  In  many  bakeries  the  Quaker  Bread  dough  is  forced 
to  be  ready  in  3 to  3J  hours. 

The  preceding  includes  not  only  English,  Irish,  and  Welsh  methods,  but 
also  a few  examples  from  Canada  and  the  United  States,  sent  by  various 
firms  on  the  American  side. 

561.  Scotch  Practice. — This  in  'its  turn  differs  considerably  from  English 
modes  of  making  bread.  For  the  earlier  portion  of  the  following  descrip- 
tion the  authors  are  indebted  to  an  article  on  Scotch  Sponging  in  the  Ameri- 
can Miller,  by  the  late  Mr.  Thoms,  of  Alyth. 

In  Scotland,  flour  barms  are  largely  used  : the  preparation  of  these 
barms  has  already  been  described.  The  barm  constitutes  the  ferment, 
and  is  mixed  direct  into  the  sponge.  Scotch  bakers  work  on  either  the 
half  or  quarter  sponge  system.  The  following  directions  for  sponging 
are  quoted  from  Thoms’  article. 

562.  “ Half  Sponge. — ^Sponging  with  either  Virgin  or  Parisian  barms 
is  identical,  whether  the  sponges  are  half  or  quarter.  A 280  lbs.  sack  of 
flour  requires  over  all  stages  of  fermentation  from  16  to  18  gallons  of  liquor. 
I assume  here  that  the  reader  knows  all  about  stirring  a sponge.  Half 
sponge  means  half  of  the  total  liquor  in  sponge.  For  every  five  or  six 
parts,  whether  pints  or  gallons  of  liquor  in  half  sponge,  we  give  one  ]3art 
of  either  of  these  barms.  The  temperature  of  the  sponge  liquor,  of  course, 
varies  with  the  seasons,  ranging  from,  in  summer,  76°  F.  to  84°  F.  ; in 
winter,  from  90°  F.  to  98°  F.  ; the  sponge  to  rise  twice,  and  be  on  the  second 
turn  within  12  hours.  Also,  to  every  gallon  of  liquor  in  sponge,  when 
using  water  of  ordinary  softness,  2 oz.  of  salt,  and  the  rest  of  the  salt 
considered  necessary  at  doughing  stage.  The  best  flour  we  find  for  sponging 
with  these  barms  is  American  North-West  ‘ Spring  ’ and  Russian  ‘ Straight  ’ 
grades.  Observe,  not  ‘ Bakers,’  which  means  ‘ straight,’  or  one-run  flour, 
with  the  cream,  in  the  shape  of  patent,  taken  out.  The  less  winter  wheat 
flour  used  in  these  sponges  the  better  ; it  should  be  used  at  the  dough 
stage.  Few  varieties  of  winter  wheat  flour  will  rise  twice  in  the  sponge 
and  produce  good  bread.  Many  of  them,  when  sponged  without  admix- 
ture, particularly  ‘ patents,’  will  not  rise  twice  with  the  purest  barm  or 
pressed  yeast.  Limited  to  winter  wheat  flour  and  half -sponging  with 
tliese  barms,  I would  sponge  stiff  almost  half  the  total  flour,  and  take  the 
sponge  on  the  first  turn.  Sponging  with  strong  glutinous  flours,  such  as 


BREAD-MAKING. 


419 


Hard  Spring  and  Russian,  I would  use  only  about  one-third  of  the  total 
flour  required  in  all  stages  ; that  is,  the  half  sponge  here  referred  to  is 
only  a fair  working  stiffness/" 

563.  “ Quarter  Sponge. — This  system  is  found  most  convenient  where 
machinery  is  used  (the  half  sponging  where  hand  labour  is  employed  for 
sponging  and  doughing),  and  means  J of  the  total  liquor  for  a known  quan- 
tity of  flour  in  the  first  stage,  instead  of  J as  in  half-sponging.  Quarter- 
sponging  is  done  in  tubs.  Sponge  for  one  sack  of  flour  requires  a tub  of 
50  gallons  capacity.  Say  we  wish  quarter- sponge  ready  for  doughing 
at  4 a.m.  to-morrow,  then  at  2 p.m.  to-day  we  take — for  making  about  one 
sack  of  flour  into  bread — 3 gallons  water,  IJ  or  IJ  gallons  barm,  and  6 
oz.  salt,  and  mix  these  with  the  necessary  flour  into  a sponge  as  stiff  as 
batch  dough.  In  12  hours,  or  2 a.m.  to-morrow,  the  sponge  will  be  turned, 
the  flrst  time  J-inch,  then  we  break  in  or  up  with  machine  or  hands, 
the  quarter  with  12  gallons  more  water,  IJ  lbs.  or  IJ  lbs.  more  salt,  and 
add  enough  flour  to  form  a very  weak  sponge.  This  will  rise  again  in 
the  tub  and  be  on  the  turn  in  about  2 hours,  or  4 a.m.,  when  the  remainder 
of  the  salt  necessary  is  dissolved  in  J gallon  water,  and  dough  made.  Many, 
and  especially  in  cold  weather,  do  not  dissolve  the  salt  in  water,  but  simply 
sprinkle  the  salt  over  the  sponge  in  the  machine  or  trough.  It  will  be 
observed  that  in  neither  the  half  nor  quarter  sponges  is  there  ferment  or 
potatoes  used.  The  barm  is  the  ferment,  and  is  added  direct  to  the  sponge. 
For  regulating  fermentation  in  warm  weather,  in  addition  to  colder  water, 
it  is  advisable  to  reduce  the  quantity  of  barm  or  yeast,  and  in  cold  weather 
to  increase  it."" 

564.  Doughing  and  Baking. — In  a personal  communication  to  one  of 
the  authors,  Mr.  Thoms  states  : “ My  article  in  the  American  Miller  on 
‘ Flour  Barms  and  Sponging  " leaves  off  with  the  sponges  ready  at  4 a.m. 
Let  us  suppose  the  sponges  ‘ broken  in  " — the  technical  term — with  the  neces- 
sary salt  and  water,  we  then  mix  in  the  flour.  Yes  ; but  what  flour  ? Spring 
American  is  supposed  to  be  used  in  sponges,  and  what  we  will  use  in  dough 
will  depend  on  the  price  for  the  flour,  the  price  for  bread,  and  whether 
our  bread  is  to  be  crusty  as  in  England,  or  close  packed,  high  volumed, 
and  silky  skinned  as  in  Scotland.  In  England  I might  use  all  Winter 
American  flour  in  dough,  here  not  more  than  half  Winter — sound  red. 
What  home  grist  we  have  goes  into  the  dough,  together  with  part  Spring 
flour.  Indian  wheat  is  going  largely  into  English  grist,  but  I would  pre- 
fer the  Indian  in  sponge.  I doubt  the  dough  stage  being  long  enough 
to  allow  the  hard  gluten  of  Indian  wheat  time  to  sufflciently  hydrate  and 
soften  (peptonise)  ; without  which  the  bread  would  be  harsh,  low,  dry 
soon,  etc.,  etc. 

“ The  doughs,  of  whatever  flours  composed,  will  be  made  by  4.30  or 
4.40  a.m.,  and  are  allowed  to  lie  for  | hour,  then  turned,  dry  dusted,  and 
kneaded  from  one  end  of  the  trough  to  the  other  and  back  again  ; and 
in  another  | hour  or  so,  or  about  6 a.m.,  they  are  thrown  out  and  scaled 
off.  Wliere  kneading  machines  are  employed,  the  dough  should  have 
more  mixing,  in  order  to  knock  out  proof  before  throwing  or  turning  out. 
How  do  you  know  when  it  is  ready  to  throw  out  and  scale  off  ? We  judge 
only  by  feel  and  smell.  The  dough  should  feel  tight,  lively,  and  resistant, 
tear  easily  ; and  the  rent,  on  the  head  being  held  down  and  a deep  inspira- 
tion taken  through  the  nose,  should  show  carbon  dioxide  in  volume  nearly 
suffocating,  accompanied  by  a slightly  vinous  odour. 

“ If  scaling  off  begins  at  6.0  a.m.,  moulding  the  loaves  may  begin  at 
about  6.30  or  6.45.  This  refers  to  medium  slack  doughs  for  close  packed 
bread  x stiff  doughs  require  longer.  After  moulding,  the  medium  slack 


420 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


loaves  are  allowed  from  15  to  30  minutes  to  prove  in  the  boxes,  and  then 
run  into  the  oven.  Stiff  dough,  again,  requires  longer  proof  ; and,  except 
in  summer,  the  boxes  holding  the  moulded  loaves  are  slightly  heated. 

“ The  time  in  oven  for  4 lb.  close-packed,  square  loaves  is  2 hours,  and 
the  best  baking  temperature  400°  F.,  while  the  bread  is  baking.  For  2 lb. 
square  loaves,  the  same  temperature,  time,  IJ  hours  ; these  data  refer 
to  both  steam  and  Glasgow  ovens  coke  heated  inside.  A higher  tem- 
perature and  shorter  time  we  find  carbonises  the  top  and  bottom  crusts,, 
while  the  crumb  in  the  heart  of  the  loaf  is  more  or  less  raw.  Crusty  loaves, 

4 lbs.,  slightly  packed,  temperature  about  the  same  or  a little  less,  380° 
to  400°  F.,  and  time,  IJ  hours  ; 2 lb.  crusty  loaves,  same  temperature, 
time,  1 hour.  These  are  not  the  shortest  times  in  which  the  various  breads 
can  be  baked,  only  what  experience  has  shown  me  to  be  the  best.  Tho 
baking  heats  refer  to  the  time  while  the  breads  are  in  the  oven.  If  the 
fires  are  lighted  at  4.0  a.m.,  it  will,  of  course,  be  necessary  to  heat  the  ovens 
higher  than  that  ; how  much  higher  will  depend  on  the  heat  of  the  ovens 
before  lighting  the  fires.  On  Mondays  we  go  higher  than  on  other  days  ; 
the  steam  ovens  we  heat  up  to  480°  F.  ; the  ovens  heated  with  coke  or  coal 
inside  we  heat  up  to  550°  F.  By  the  time  the  batches  are  ready  to  go  in 
they  will  have  cooled  down  to  420-30°  F.,  and  by  the  time  the  batches 
are  actually  in  they  will  show  a temperature  of  410-15°  F.’' 

565.  Scotch  Bread-making  Processes,  Meikle. — ^Mr.  J.  Meikle,  of  Belfast, 
has  favoured  the  author  with  the  following  specially  obtained  information. 
The  various  data  have  been  submitted  to  several  experienced  Scottish 
bakers,  and  therefore  may  be  regarded  as  perfectly  trustworthy. 

Scottish  systems  of  bread-making  differ  a good  deal  from  the  pro- 
cesses that  obtain  in  England.  Sponging  is  almost  as  popular  to-day  as 
it  was  two  decades  ago  ; all  serious  operations  indeed  being  carried  through 
under  some  kind  of  sponging  system.  The  two  leading  processes,  however, 
are  the  “ quarter  ’’  and  the  “ half  ''  sponge. 

Quarter  Sponge,  for  IJ  Sacks  of  Bread. 

28  lbs.  Water.  10  lbs.  Barm. 

70  lbs.  Flour.  10  oz.  Salt. 

80°  F.  Temperature.  Time — 13  hours. 

Sponge. 

160  lbs.  Water.  2J  lbs.  Salt. 

126  lbs.  Flour. 

78°  F.  Temperature.  Time — 1^  hours. 

Dough. 

£0  lbs.  Water.  lbs.  Salt. 

224  lbs.  Flour.  78°  F.  Temperature. 

Scale  in  1 J hours  : the  temperatures  given  are  those  of  sponge,  etc.,  when 
made. 

The  quarter  system  is  a three  process  system.  The  quarter  is  made 
up  at  nigiit  generally  and  lies  about  13  hours  ; it  should  then  be  up  and 
dropped  an  inch,  and  is  turned  into  a “ sponge  tub — a tub  of  a capacity 
of  48  gallons — then  water  is  added,  the  quarter  is  well  broken,  then  salt 
and  Hour  are  put  in  to  make  a thin  sponge.  The  sponge  lies  about  75 
minutes  and  is  doughed  as  soon  as  it  shows  signs  of  setthng  down  : this 
is  of  course  for  square  batched  bread,  and  nothing  can  touch  this  system 
for  appearance  : nearly  all  the  bread  of  Glasgow  and  the  West  is  made  in 
this  way. 


BREAD-MAKING. 

Half  Sponge,  IJ  Sacks. 


421 


100  lbs.  Water.  20  lbs.  Barm. 

185  lbs.  Flour.  IJ  lbs.  Salt. 

80°  Temperature.  Ready  13  hours  time. 

Dough. 

105  lbs.  Water.  6J  lbs.  Salt. 

235  lbs.  Flour.  78°  F.  Temperature. 

Scale  in  If  hours.  Both  this  and  the  previous  system  dough  want  at 
least  one  turn  or  cut  back  while  lying  in  dough.  This  system  does  not 
make  such  picture  bread  as  the  quarter,  but  it  eats  better,  particularly 
so  wFen  distiller's  yeast  is  used.  This  is  the  kind  of  system  worked  in 
the  North  of  Ireland  ; but  the  length  of  time  the  sponge  lies  is  being  consider- 
ably curtailed  in  these  days. 

Short  System. 

Short  systems  of  fermentation  are  making  some  little  headway  in  Scot- 
land, but  probably  as  a novelty  ; the  following  turns  out  a passable  loaf  when 
suitable  flours  are  used. 


Short  Process  Sponge. 

70  lbs.  Water. 

1 lb.  Salt. 

74  lbs.  Flour. 

3 lbs.  Yeast. 

86°  F.  Temperature. 

Time — 1 hour. 

Dough. 

145  lbs.  Water. 

7 lbs.  Salt. 

346  lbs.  Flour. 

82°  F.  Temperature. 

Lie  3 hours  before  scaling.  This  process  does  not  give  the  “ pile  " of 
sponge  bread,  but  it  makes  a much  better  square  loaf  than  a short  straight 
dough  system  does. 


Flour  used  in  Scotland. 

The  flour  trade  in  Scotland  has  undergone  great  changes  during  the  last 
fifteen  years,  for  whereas  at  that  time  American  flour  was  the  only  flour 
that  mattered,  the  imports  from  the  United  States  are  now  almost  a neghgible 
quantity.  But  Scotch  bakers  need  strong  flours,  or  what  is  the  same 
thing  practically,  they  think  they  need  them,  and  the  home  millers  supply 
them.  Minnesota  spring  wheat  of  good  quality  is  of  course  as  scarce  as  Min- 
nesota flour,  and  millers  use  strong  Russians  and  Manitoban  wheats  instead. 
Flours  from  those  wheats  are  used  for  sponging.  For  doughing  a propor- 
tion of  American  Winters  was  at  one  time  a favourite,  and  even  now  American 
Winters,  or  home-milled  flours  from  Australian  and  Argentine  wheats, 
blended  to  work  like  Winters,  are  much  used,  with  say  a proportion  of  Kansas 
flour,  and  some  flours  of  the  “ Millennium  ” and  ‘‘As  You  Like  It  ” type  of 
English  milled  flours.  There  is  a wider  range  of  doughing  flours,  for  the 
kind  of  flour  wanted  for  this  purpose  depends  upon  what  has  been  used 
in  the  sponge.  The  wheats  of  Manitoba,  Kansas,  Australia,  Argentine, 
and  so  on,  all  come  in  useful. 

For  barm  flour  fine  Russian  and  Manitoban  wheats  are  favourites. 
This  flour  is  very  often  a straight  run  flour  ; straights  suit  barm-making 
best.  By  the  way,  about  the  best  virgin  barm  the  writer  ever  saw  made 
for  a length  of  time  was  made  from  Scotch  kiln-dried  wheat  milled  on 
stones.  Hungarian  flour,  once  a prime  favourite  for  good  class  bread,  is 
now  almost  unknown  in  Scotland.  (Personal  Communication,  October, 
1910.) 


422 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Review  of  Pan  ary  Fermentation. 

566.  It  is  proposed  in  the  succeeding  paragraphs  to  consider  the  nature 
of  the  chemical  changes  which  occur  during  bread  or  panary  (from  panis^ 
bread)  fermentation.  Suggestions  will  also  be  made  as  to  possible  improve- 
ments in  methods  of  carrying  out  the  various  processes,  with  the  hope  that 
they  may  lead  to  the  avoidance  of  those  causes  which  result  in  the  pro- 
duction of  bad  or  inferior  bread 

567.  The  Ferment.— Potatoes,  termed  by  the  baker  “ fruit,”  constitute 
the  principal  ingredient  of  the  ferment ; their  composition  is  indicated  in 
the  following  analyses.  No.  1 was  grown  with  mineral  manure.  No.  2 with 
a rich  nitrogenous  manure  : — 

No.  1.  No.  2. 

7640  75-20 

14-91  15-58 

2-17  3-60 

2-34  1-29 

0-15  1-11 

0- 29  0-31 

1- 70  1-99 

0- 99  1-03 

1- 00  0-90 


Water 

Starch 

Proteins  . . 

Dextrin 

Sugar 

Fat 

Extractive  Matter 
Cellulose  . . 

Ash 


Roughly  speaking,  a potato  contains  three  quarters  of  its  weight  of 
water  and  about  15  per  cent,  of  starch  ; the  remainder  being  made  up 
of  small  percentages  of  proteins,  dextrin,  • sugar,  and  other  substances. 
On  being  boiled,  the  starch  is  gelatinised,  and  on  mashing  the  potatoes, 
together  with  the  liquor  in  which  they  have  been  boiled,  a starch  paste 
is  formed,  containing  also  considerable  quantities  of  dextrin  and  sugar, 
and  what  is  of  great  importance,  soluble  nitrogenous  compounds.  Yeast 
on  being  sown  in  this  medium  sets  up  an  active  fermentation,  ^largely 
due  to  the  sugar  already  present,  together  with  the  strong  nitrogenous 
stimulant.  In  Chapter  XI  it  has  been  demonstrated  that  the  fermen- 
tation is  almost  as  active  in  the  filtered  potato  water  as  in  the  mash.  It 
must  also  not  be  forgotten  that  yeast  alone  is  incapable  of  inducing  dias- 
tasis in  starch  paste.  Consequently  any  unaltered  starch  suffers  little 
change  in  a ferment  containing  only  boiled  potatoes  and  yeast.  But 
raw  flour  being  also  commonly  added,  the  yeast  induces  a change  in  the 
flour  proteins,  in  virtue  of  which  they  become  somewhat  active  hydrolysing 
agents,  and  so  the  potato  starch  is  indirectly  converted  in  part  into  sugar. 
The  yeast,  when  sown  in  a ferment,  multiplies  by  growth,  and  thus  a rela- 
tively smaller  quantity  of  yeast  is  enabled  to  do  the  after  work.  A large 
proportion  of  the  starch  of  the  potato  still  remains  unchanged  at  the  close 
of  the  fermentation  of  the  ferment  ; so  also,  the  nitrogenous  matter  of  the 
potato  in  great  part  remains.  When  the  ferment  is  added  to  the  sponge, 
the  smaller  quantity  of  yeast  not  only  does  more  work  because  of  its  having 
liad  the  opportunity  of  growth  and  reproduction  in  the  ferment,  but  also 
because  the  nitrogenous  matter  of  the  potato  still  acts  as  a yeast  stimulant 
in  the  sponge.  The  active  effect  of  potato  water  alone  shows  that  this 
stimulating  action  of  the  ferment  on  yeast  must  not  be  entirely  ascribed 
to  the  starch  present.  From  the  active  stimulating  nature  of  the  nitro- 
genous matter  of  potatoes  on  yeast,  it  seems  probable  that  that  matter 
consists  of  nitrogen  in  some  other  form  than  albuminous  compounds.  Sum- 
ming up  these  changes  into  one  sentence,  in  the  ferment  the  yeast  acts  on  the 
soluble  proteins  of  the  flour  and  enables  them  to  effect,  to  a limited  extent,  diastasis 
of  the  starch  ; this  results  in  the  production  of  a saccharine  medium  in  which  the 


BREAD-MAKING.  423 

yeast  grows  anil  reproduces  ; further,  the  soluble  nitrogenous  matter  of  the  potato 
acts  as  an  energetic  yeast  stimulant. 

It  is  essential  that  the  potatoes  used  in  the  ferment  be  sound  : they 
should  first  of  all  be  washed  absolutely  clean.  A common  practice  is 
to  place  them  in  a pail  or  tub,  with  water,  and  scrub  them  with  an  ordinary 
bass  broom  ; this  treatment  is  inefficient,  as  potatoes  served  in  this  way 
still  retain  a considerable  amount  of  dirt.  The  potatoes  are  then  boiled 
in  their  jackets,  and  afterwards  rubbed  through  a sieve  in  order  to  separate 
the  skins.  By  far  the  best  plan  to  clean  potatoes  is  by  means  of  a machine, 
of  which  the  following  type  answers  well  for  all  practical  purposes.  The 
machine  consists  essentially  of  an  outer  tub,  in  which  is  fixed  a vertical 
revolving  brush  : the  potatoes  are  put  in,  and  about  two  minutes  turning 
the  brush  cleans  them  most  effectually.  The  dirt  is  removed  and  also  a 
good  deal  of  the  outer  skin,  while  the  interior  of  the  potato  remains  intact. 
Treated  in  this  manner  the  potatoes  have  only  just  the  slightest  film  of 
skin  to  be  removed,  after  boiling,  by  means  of  the  sieve.  In  the  next  place, 
the  pan,  or  other  vessel  used  for  boiling  the  potatoes,  should  be  kept  clean  ; 
this  is  only  done  by  its  being  washed,  drained,  and  wiped  dry  every  day. 
Not  only  the  potatoes,  but  the  water  in  which  they  are  boiled,  should 
be  quite  clean  enough,  if  need  be,  to  go  into  the  bread.  At  present,  many 
bakers  steam  their  potatoes  in  preference  to  boiling  : this  modification 
is  cleanly  and  convenient.  The  potatoes  are  placed  in  a metal  work  cage, 
which  in  its  turn  is  placed  in  a box  arrangement,  through  which  steam 
is  conducted  from  a boiler  : when  sufficiently  cooked,  the  cage,  together 
with  the  potatoes,  is  lifted  out,  and  its  contents  poured  on  to  a sieve.  The 
ferment  should  be  rapidly  cooled  to  the  pitching  temperature  of  about 
80°  F.  in  summer,  and  85°  in  winter  : in  summer  it  is  very  important 
that  the  baker  should  throughout  conduct  his  fermentation  at  as  low  a 
temperature  as  possible.  During  the  time  that  a ferment  is  working  the 
temperature  should  be  kept  even  : for  this  purpose  select  a place  in  the 
bake-house  free  from  draughts  or  excessive  heats. 

At  present,  flour,  together  with  malt  extract  and  a number  of  other 
materials,  are  being  used  as  substitutes  for  potatoes  in  ferments,  the  use  of 
which  is  now  the  exception  rather  than  the  rule. 

568.  Panary  Fermentation. — The  consideration  of  the  division  of  this 
process  into  sponging  and  doughing  may  be  postponed  until  after  a study 
of  the  nature  of  the  changes  occurring  during  panification  as  a whole.  Yeast 
flour,  and  water,  at  a suitable  temperature,  on  being  mixed  so  as  to  form 
a dough,  immediately  begin  to  react  on  each  other.  The  flour,  it  must 
be  remembered,  contains  sugar,  starch,  and  both  soluble  and  insoluble 
proteins.  The  yeast  consists  essentially  of  saccharomyces  ; but  bacterial 
life  is  also  present  in  greater  or  less  quantity,  not  only  in  the  yeast  but 
also  in  the  flour.  The  yeast  rapidly  sets  up  alcoholic  fermentation,  thus 
causing  the  decomposition  of  the  sugar  into  alcohol  and  carbon  dioxide 
gas  ; the  latter  is  retained  within  the  dough  and  causes  its  distension. 
Functioning  in  dough,  no  reproduction  of  the  yeast  occurs  ; after  a time 
the  yeast  cells  disappear  through  the  degradation  and  rupture  of  their 
walls.  In  addition,  the  yeast  attacks  the  proteins  present,  effecting  changes 
in  them  which  are  similar  to,  if  not  identical  with,  the  earlier  processes  of 
digestion.  Albumin  and  its  congeners  are,  in  fact,  more  or  less  peptonised. 
The  gluten,  from  being  hard  and  india-rubber  like,  becomes  softer,  and 
within  certain  limits  more  elastic  ; but  if  fermentation  be  allowed  to  pro- 
ceed too  far,  the  gluten  softens  still  further,  and  its  peculiar  elasticity 
in  great  part  disappears.  It  is  uncertain  to  what  extent  these  changes 
in  the  gluten  are  due  to  the  specific  action  of  yeast,  as  they  also  occur, 


424 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


although  more  slowly,  in  flour  which  has  simply  been  mixed  with  water. 
It  has  been  already  explained  that  under  the  action  of  yeast  the  albu- 
minous bodies  of  flour  acquire  the  power  of  effecting  the  diastasis  of  starch  ; 
this  compound  is  consequently  to  some  extent  converted  into  dextrin 
and  maltose  during  panification.  The  amount  of  starch  so  hydrolysed 
depends  largely  on  the  soundness  of  the  flour.  In  addition,  the  diastase 
of  the  flour  itself  will  probably  have  some  action  in  inducing  starch  con- 
version. The  lower  the  grade  of  the  flour,  the  more  raw  grain  diastase  it 
usually  contains.  When  potatoes  are  used,  whether  as  a ferment  or  as  a 
direct  addition  to  the  flour,  they  furnish  soluble  starch,  and  also  act  as  a 
nitrogenous  yeast  stimulant.  While  the  yeast  effects  important  changes 
in  the  albuminous  compounds  of  flour,  experiments  made  and  described 
in  Chapter  XI  show  that  little  or  no  gas  is  evolved  as  a consequence  of 
such  changes.  The  gas  produced  in  dough  during  bread-making  is  the 
result  of  normal  alcoholic  fermentation  of  sugar  by  the  yeast.  Summing 
up  the  changes  produced  in  panification — they  are  alcoholic  fermentation  of  the 
sugar,  softening  and  proteolytic  action  on  the  proteins,  and  a limited  diastasis 
of  the  starch  by  the  proteins  so  changed. 

So  much  for  the  action  of  yeast  on  dough.  The  next  point  of  import- 
ance is  the  effect  produced  by  such  other  organisms  as  may  be  present. 
The  principal  one  of  these  is  the  lactic  haciUus  ; under  its  influence  the 
sugar  of  the  dough  is  converted  into  lactic  acid.  Either  the  organism 
itself,  or  the  acid  produced  by  its  action  on  sugar,  has  a softening  and 
dissolving  effect  upon  gluten.  Opinions  differ  as  to  the  desirability,  or 
otherwise,  of  the  presence  of  lactic  ferments  in  yeasts  used  for  bread-making. 
It  has  already  been  explained  that  their  being  found  in  any  but  the  smallest 
quantity  in  brewers’  or  compressed  yeasts  is  an  unfavourable  sign,  as  they 
show  that  due  care  has  not  been  taken  in  the  manufacture  of  the  yeast  ; 
for  that  reason  their  presence  is  deemed  unfavourable.  In  Scotch  flour 
barms  th^  presence  of  lactic  ferments  in  not  too  great  amount  is  deliberately 
encouraged  ; experience  having  shown  that  if  the  barms  be  brewed  so  as 
to  exclude  these  organisms  such  good  bread  is  not  produced.  In  Scotch 
bread-making  very  hard  and  stable  flours  are  used  ; the  lactic  ferment 
does  good  service  in  softening  the  gluten.  It  is  possible  also  that  during 
the  long  period  of  sponging  and  doughing,  the  changes  induced  by  the  lactic 
ferment  may  cause  slight  evolution  of  gas  ; but  so  far  as  actual  aeration 
of  the  dough  is  concerned  this  may  be  viewed  as  a negligible  quantity. 
It  must  be  remembered  that  the  soupQon  of  slight  buttermilk  flavour  of 
a valued  characteristic  of  Scotch  bread.  In  bread-making,  as  conducted 
by  most  English  processes,  particularly  with  soft  flours  having  but  little 
stability,  there  seems  no  useful  function  which  the  lactic  ferment  can  per- 
form ; its  absence  is  therefore  rather  to  be  desired  than  its  presence.  A 
yeast  may  contain  other  organisms  in  addition  to  those  just  mentioned  ; 
these  are  capable  of  inducing  changes  of  a far  more  serious  nature  than 
does  the  lactic  ferment.  Among  these  there  are  the  organisms  which  cause 
butyric  and  putrefactive  fermentation.  That  bane  of  the  baker,  sour 
bread,  is  commonly  ascribed  to  the  action  of  either  lactic  or  acetic  fermen- 
tation ; it  is,  however,  far  more  probable  that  this  unwelcome  change  is 
due  to  incipient  putrefactive  and  butyric  fermentation  ; since  the  odour 
of  a sour  loaf  is  very  different  from  that  of  either  the  vinegar-like  smell 
of  acetic  acid  or  the  buttermilk  odour  accompanying  lactic  acid  in  altered 
milk.  The  souring  takes  place  more  usually  in  the  bread  rather  than  in 
the  dough. 

In  order  to  produce  a healthy  fermentation  in  dough,  healthy  yeast  is 
of  vital  importance  : purity  from  foreign  organisms  is  desirable  (saving, 
perhaps,  a small  proportion  of  lactic  ferment  in  flour  barms),  but  above 


BREAD-MAKING. 


425 


all  the  yeast  itself  must  be  active  and  in  good  condition.  Given  a yeast, 
which  contains  a certain  percentage  of  foreign  ferments,  those  ferments 
Avill  be  held  in  abeyance  while  the  yeast  itself  is  energetic  and  healthy. 
Bakers  are  often  puzzled  by  microscopic  observations  of  yeast  ; they  find 
that,  of  two  yeasts,  one  produces  sour  and  the  other  a good  bread,  and 
yet  that  the  two  contain  about  the  same  quantities  of  disease  ferments. 
They  are  consequently  very  apt  to  despise  any  conclusions  they  may  have 
drawn  from  microscopic  observations ; but  the  difference  in  such  cases 
lies  in  the  yeast  itself  : the  one  will  be  healthy  the  other  weak  and  languid. 
Quoting  again  from  previously  described  experiments,  in  the  same  sample 
of  wort,  divided  into  two  portions,  the  one  only  of  which  was  sown  with 
yeast,  and  both  equally  exposed  to  the  air,  it  was  found  that  in  the  presence 
of  yeast  life,  bacteria  refused  to  develop,  while  in  its  absence  they  repro- 
duced with  enormous  rapidity.  In  the  same  way  the  healthy  yeast  sus- 
pends the  developments  of  bacteria  in  dough,  while  the  yeast  being  weak 
and  almost  inactive,  bacterial  life  flourishes  apace.  Examination  would 
reveal  that  in  most  cases  of  unhealthy  panary  fermentation  the  fault  is  as 
much  due  to  the  yeast  itself  as  to  the  abnormal  presence  of  foreign  ferments. 

569.  Sponging  and  Doughing. — This  division  of  the  process  of  panary 
fermentation  into  two  distinct  steps  is  of  extreme  interest.  The  origin, 
and  reasons  which  led  to  the  adoption,  of  this  mode  of  procedure  are  prob- 
ably due  to  the  exigencies  of  dough-kneading  by  hand.  For  even  when 
using  flour  from  the  lot  which  has  been  placed  in  his  trough,  the  baker 
usually  elects  to  work  a part  of  it  into  a sponge  first.  The  reason,  or  at 
least  one  reason,  is  that  the  dough  softens  on  standing,  and  therefore  there 
is  less  work  involved  in  mixing  in  the  flour  in  two  instalments  than  in  one, 
as  the  first  lot  will  have  got  considerably  softer.  Further,  very  little  experi- 
mental work  in  this  direction  will  have  shown  the  baker  that  he  required 
to  use  less  yeast,  and  got  better  results  when  working  in  this  way.  Hence, 
doubtless,  for  original  reasons  such  as  these,  the  division  of  bread-making 
into  sponge  and  dough.  Independently  of  this,  they  have  for  other  reasons 
a most  important  scientific  justification.  The  reader  will  by  this  time  be 
familiar  with  the  division  of  flours  into  strong  and  weak  varieties.  The 
various  tests  given  in  a preceding  chapter  show  not  merely  that  one  flour 
absorbs  more  water  than  another  to  form  a dough  of  standard  stiffness, 
but  also  that  some  flours  fall  off  far  more  rapidly  in  stiffness  than  do  others 
when  kept  in  the  condition  of  dough.  There  are  therefore  two  distinct 
properties  here  to  be  considered  in  relation  to  flour,  the  absolute  quantity 
of  water  it  absorbs,  and  also  the  rate  at  which  slackening  goes  on  during 
panification.  Remembering  the  previous  definition  of  water-absorbing 
power,  the  relative  capacity  of  resistance  of  flours,  to  a falling  off  in  water-retaining 
power  during  fermentation,  may  appropriately  be  termed  their  “ Stability.”  As 
a rule,  the  strong  flours  are  also  the  more  stable,  but  this  does  not  necessarily 
hold  good  in  all  cases.  It  has  been  already  explained  that,  for  the  pro- 
duction of  the  best  bread,  fermentation  should  be  allowed  to  proceed  suffi- 
ciently far  to  soften  and  mellow  the  gluten,  but  no  further.  At  stages 
either  earlier  or  later  than  this,  the  bread  will  lack  both  in  appearance 
and  flavour.  It  is  therefore  necessary  to  so  regulate  fermentation  as  to 
stop  at  precisely  this  point  ; unfortunately  no  exact  means  are  at  present 
known  whereby  it  can  be  determined  with  precision.  The  more  stable  a 
flour  is,  the  longer  it  requires  to  be  fermented  before  this  point  is  reached, 
hence  where  flours  of  different  qualities  are  being  used,  the  more  stable 
should  be  set  fermenting  earlier  than  the  others.  In  this  lies  the  reason  for 
using  some  flours  at  the  sponge  and  others  at  the  dough  stage.  Flours 
from  hard  wheats,  such  as  Spring  American  or  Russian,  should  be  used 


426 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


in  the  sponge  ; and  American  Winter  or  English  wheaten  flours  in  the 
dough.  Working  with  stable  flours  in  the  sponge,  experience  has  shown 
according  at  least  to  the  London  practice,  that  the  best  results  are  ob- 
tained by  allowing  the  sponge  to  rise  and  fall  once,  and  then  to  rise  again. 
The  time  taken  for  this  rising  and  falling  is  found  to  agree  with  that  neces- 
sary for  the  sufficient  mellowing  of  the  gluten.  This  empirical  test,  which 
is  the  result  of  careful  watching  and  experience,  is  at  present  the  baker’s 
principal  guide  in  determining  the  progress  of  fermentation.  It  affords 
evidence  of  the  degree  of  rapidity  with  which  gas  is  being  evolved,  and 
indirectly  of  the  extent  to  which  the  other  chemical  changes  have  proceeded. 

Reference  has  already  been  made  to  the  great  change  which  has  during 
the  past  few  years  come  on  baker’s  practice.  For  various  reasons,  among 
which  those  cited  by  Callard  are  some  of  the  leading  ones,  the  sponge  and 
dough  methods  have  largely  given  place  to  straight  or  off-hand  doughs. 
Possibly  the  exigencies  of  hand  kneading,  referred  to  at  the  commence- 
ment of  this  paragraph,  have  so  completely  disappeared,  with  the  greater 
adoption  of  machinery,  by  which  a stiff  straight  dough  is  readily  made, 
that  any  division  of  the  dough-making  process  is  no  longer  found  or 
deemed  necessary. 

570.  Variety  and  Quantity  of  Yeast  used. — The  variety  of  yeast  employed 
produces  a marked  effect  on  the  charaeter  of  the  resultant  bread.  Good 
brewers’  yeast  is  almost  universally  admitted  to  induce  a characteristic- 
sweet  or  “ nutty  ” flavour,  hence  it  has  been  largely  used  in  the  manufacture 
of  so-called  farmhouse  bread.  Colour  in  this  variety  of  bread  is  seeondary 
to  sweetness  of  flavour.  While  brewers’  yeast  has  a somewhat  energetic 
diastatic  action  on  the  proteins  and  starch  of  dough,  its  fermentative  power 
is  comparatively  low  in  that  medium.  Undoubtedly,  one  of  the  reasons 
which  has  led  to  the  comparatively  extensive  use  of  potatoes  in  bread- 
making is  their  stimulant  action  on  the  gas-producing  power  of  brewers’ 
yeast  in  dough. 

Continental  compressed  yeasts,  on  the  other  hand,  are  marked  by  their 
rapid  power  of  inducing  alcoholic  fermentation  in  dough  : experience 
indicates  that  neither  potato  nor  flour  ferments  are  necessary,  at  least  as 
stimulants,  when  working  with  these  yeasts. 

Motives  of  economy  on  the  part  of  the  bakers,  and  competition  on  the 
side  of  the  yeast  merchants,  both  lead  to  a certain  rivalry  among  the  latter 
as  to  whose  yeast  is  able,  weight  for  weight,  to  adequately  ferment  the 
greatest  quantity  of  flour.  Now,  while  it  is  important  that  the  baker  should 
know  with  accuracy  the  relative  strengths  of  different  brands  of  yeast,  it 
is  nevertheless  not  wise  to  be  too  sparing  in  the  quantity  employed  to  a 
sack  of  flour.  First,  select  the  strongest  and  purest  yeast  you  can  get  for 
the  money,  and  then  don’t  be  afraid  to  use  sufficient  of  it.  This  advice 
should  have  especial  weight  where  soft,  weak  flours,  having  comparatively 
little  stability,  are  so  largely  employed.  Flours  of  this  kind  will  not  bear 
being  kept  so  long  in  the  sponge  and  dough  stage  as  is  necessary  to  ferment 
them  with  a very  small  quantity  of  yeast  ; they,  if  so  treated,  produce 
sodden,  heavy,  and  sometimes  sour  loaves  ; when  any  saving  in  yeast  is 
more  than  compensated  by  a less  yield  of  bread. 

571.  Management  of  Sponging  and  Doughing. — In  order  to  insure  success 
in  the  manufacture  of  bread,  sound  materials  are  the  first  requisite  : after 
that  the  most  important  in  this,  like  all  other  operations  in  which  fermenta- 
tion employs  an  important  part,  is  the  proper  regulation  of  temperature. 
Tiie  yeast  should  always  be  stored  where  it  will  get  neither  too  hot  nor  too 
cold  ; for  extremes  of  temperature  in  either  direction  weaken  the  action  of 
yeast.  Brewers’  yeast  in  particular  suffers  from  this  in  summer  weather  ; 


BREAD-MAKING. 


427 


and  so,  many  bakers  who  use  it  in  the  winter  change  over  to  compressed 
yeast  in  the  summer.  In  summer  time  the  compressed  yeasts  are  when 
fresh  more  active  than  in  winter  : in  the  latter  season,  the  strength  of  the 
yeast  may  be  increased  by  allowing  it  to  stand  for  a time  in  water  at  85°  F. 
before  being  used.  A still  better  plan  is  to  stir  a small  quantity  of  sugar 
or  malt  extract  into  a bowl  of  water  and  then  add  the  yeast  ; let  this  stand 
for  about  an  hour,  gently  stirring  now  and  then  in  order  to  aerate  the  liquor. 
Such  treatment  refreshes  and  invigorates  the  yeast,  and  so  enables  it  to 
afterwards  work  more  actively.  Both  sponge  and  dough,  or  straight  dough, 
should  be  so  managed  as  to  keep  the  temperature  as  nearly  constant  as 
possible  during  the  whole  of  the  fermentation.  Good  yeast  works  well  at 
from  80°  to  85°  F.,  and  at  that  temperature  lactic  and  butyric  fermentation 
proceed  but  slowly,  even  in  the  presence  of  the  special  organisms  which 
induce  these  types  of  fermentation.  Sudden  cold  should  also  be  avoided, 
as  a chill  to  working  yeast  is  most  detrimental,  causing  fermentation  to 
entirely  cease,  or  at  the  best  to  proceed  most  sluggishly.  Such  a sudden 
lowering  of  temperature  may  indirectly  be  the  means  of  producing  a sour 
loaf. 

572.  Use  of  Salt. — ^A  great  deal  has  been  written  as  to  the  use  of  salt 
as  a guiding  agent  in  fermentation  ; so  far  as  the  yeast  is  concerned,  salt 
is  generally  viewed  as  having  a retarding  influence  ; although  the  opinion 
has  been  expressed  that  quantities  of  salt  under  3 per  cent,  of  the  water 
used  stimulates  the  action  of  yeast.  This  opinion  is  based  on  certain  obser- 
vations of  Liebig.  The  author's  own  experiments  {vide  Chapter  XI.,  para- 
graph 371)  lead  him  to  conclude  that  salt,  in  all  proportions  from  1*4  per 
cent,  upwards,  retards  alcoholic  fermentation,  and  diminishes  the  speed  of 
gas  evolution.  Salt  acts  still  more  powerfully  as  a retarding  agent  on  lactic 
and  other  foreign  ferments,  and  so  aids  in  the  prevention  of  unhealthy  fer- 
mentation. In  addition,  salt  also  checks  diastasis,  and  thereby  prevents 
undue  hydrolysis  of  the  starch  of  the  flour.  In  summer  time,  or  when  any 
suspicion  of  instability  attaches  to  the  flour,  it  is  well  to  add  some  portion 
of  the  salt  to  the  sponge  ; but  when  the  flour  is  good,  and  the  yeast  pure 
and  healthy,  the  whole  of  the  salt  may  be  deferred  to  the  dough  stage. 

In  the  Scotch  methods  of  bread-making,  flours  of  a very  strong  and 
stable  character  are  used  in  the  sponge,  which  altogether  is  allowed  to  stand 
about  12  hours.  A slight  amount  of  lactic  acidity  is  developed  in  this, 
and  is  viewed  as  normal  ; it  has  an  important  function  in  softening  and 
mellowing  the  gluten.  It  will  be  noticed  that  a small  proportion  of  salt 
is,  in  the  Scotch  process,  added  to  the  sponge. 

573.  Loss  during  Fermentation. — This  has  been  variously  estimated, 
among  the  highest  figures  being  that  of  Dauglish,  who  expressed  the  opinion 
that  this  loss  amounted  to  from  3 to  6 per  cent.  In  order  to  determine 
the  maximum  amount  of  loss  possible,  the  authors  made  a direct  experi- 
ment— 100  parts  by  weight  of  soft  flour  from  English  wheats  were  made 
into  a dough  with  distilled  water,  two  parts  of  pressed  yeast  being  added  ; 
no  salt  being  used.  This  dough  was  allowed  to  stand  for  from  8 to  9 hours 
at  a temperature  of  about  85°  to  90°  F.  ; fermentation  proceeded  violently, 
but  towards  the  end  of  the  time  had  apparently  ceased.  The  dough  was 
then  placed  in  a hot-water  oven,  and  maintained  at  a constant  temperature 
of  212°  F.  for  10  days  ; the  same  weight  of  flour  and  yeast,  but  no  water, 
was  also  placed  in  the  oven.  At  the  end  of  that  time  the  fermented  dough 
was  found  to  have  lost  2*5  per  cent,  compared  with  the  flour.  Now  in  this 
extreme  case  a soft  flour  was  used  with  distilled  water  and  no  salt,  and 
about  six  times  the  normal  amount  of  yeast  ; the  temperature  was  pur- 


428 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


posely  maintained  at  a high  point,  and  the  fermentation  carried  on  so  long 
as  any  decided  evolution  of  gas  occurred.  Yet,  under  these  conditions, 
which  far  and  away  exceed  in  severity  any  such  as  are  met  with  in  practice, 
the  loss  was  less  than  Dauglish’s  minimum  estimate.  In  the  fermentation 
experiments  described  in  Chapter  XV.,  paragraph  466,  the  total  loss  in 
weight  of  the  dough  during  fermentation  was  only  0*59  per  cent  with  a 
strong  flour,  and  0 *70  per  cent,  with  a weak  flour.  In  both  cases  the  extent 
of  fermentation  was  as  nearly  as  possible  that  normally  employed  in  modern 
bread-making  processes. 

574.  Baking. — For  baking,  the  oven  should  be  at  a temperature  of  450- 
500°  F.  Most  modern  ovens  are  now  fitted  wath  a pyrometer,  by  means 
of  which  the  temperature  may  be  read  off.  If  depending  on  this  instru- 
ment, care  must  be  taken  that  it  is  in  efficient  working  order.  In  the  oven 
the  dough  rapidly  swells  from  the  expansion  of  the  gases  within  the  loaf 
by  the  heat.  Its  outside  is  converted  into  a crust  ; the  starch  being  changed 
into  gum  and  sugar  : these  are  at  the  high  temperature  slightly  caramel- 
ised, and  so  give  the  crust  its  characteristic  colour.  The  effect  of  the  heat 
on  the  interior  of  each  loaf  is  to  evaporate  a portion  of  the  water  present 
in  the  dough  : the  carbon  dioxide,  and  a portion  of  the  alcohol  produced 
by  fermentation,  escape  with  the  steam^  and  may  be  recovered  from  the 
gases  within  the  oven.  While  any  water  is  present  in  the  bread,  the  tem- 
perature of  its  interior  can  never  rise  above  the  boiling  point  of  that  liquid. 
Owing  to  the  pressure  caused  by  the  confining  action  of  the  crust,  that 
boiling  point  may,  however,  be  somew'hat  higher  than  under  normal  atmos- 
pheric pressure.  The  increase  due  from  this  cause  is  probably  not  more 
than  some  two  or  three  degrees.  As  baked  bread  still  contains  some  35  to 
40  per  cent,  of  moisture,  it  may  be  safely  stated  that  the  inside  of  the  loaf 
never  rises  to  a higher  temperature  than  215°  F.  It  is  commonly  stated 
that,  in  the  act  of  baking,  the  starch  of  flour  is  gelatinised.  This,  however, 
is  only  partly  the  case.  The  temperature  of  a baked  loaf  rises  considerably 
above  that  requisite  for  gelatinisation,  but  there  is  also  another  condition 
necessary.  Gelatinisation  is  essentially  an  act  of  union  with  w^ater,  and  a 
loaf  does  not  contain  sufficient  moisture  to  anything  like  gelatinise  the 
whole  of  the  starch.  At  the  moment  of  writing,  a fragment  of  bread  has 
just  been  examined  microscopically,  and  field  after  field  is  seen  of  unbroken 
and  apparently  unaltered  starch  corpuscles.  One  of  the  largest  present 
w^as  measured  and  found  to  be  0*057  m.m.  in  diameter,  showing  that  the 
starch  had  not  even  materially  swollen.  Doubtless  under  the  influence 
of  heat  the  starch  has  become  softened,  but  the  larger  proportion  of  the 
granules  still  remain  intact.  (Compare  paragraph  171,  page  81.)  At  the 
temperature  of  I the  interior  of  the  loaf,  the  coagulable  proteins  Avill  have 
been  coagulated,  and  their  diastatic  power  entirely  destroyed.  The  com- 
position of  bread,  compared  with  that  of  flour,  is  dealt  with  subsequently. 

575.  Time  necessary  for  Baking. — ^The  time  during  wLich  bread  is  kept 
in  the  oven  varies  considerably  in  different  parts  of  the  country  ; much 
must  depend  on  the  temperature — whether  the  oven  be  quick  or  slack. 
For  4 lb.  crusty  loaves  an  hour  to  an  hour  and  a quarter  seems  to  be  an 
average  time.  The  half-quartern  or  2 lb.  loaf  is  a much  commoner  size 
in  England,  and  loaves  of  this  description  can  readily  be  baked  in  from  40 
to  50  minutes  in  any  w-ell  constructed  oven. 

576.  Glazing. — ^The  admission  of  steam  to  an  oven,  w hen  properly  man- 
aged, has  the  effect  of  producing  a glazed  surface  on  the  outside  of  the  crust  : 
this  operation  is  familiar  to  bakers  as  that  by  which  Vienna  rolls  are  glazed. 
In  order  that  the  operation  shall  be  effective,  the  bread  or  rolls  should  be 


BREAD-MAKING. 


429 


as  cool  as  possible.  The  steam  should  be  simply  at  atmospheric  pressure, 
and  saturated  with  moisture.  At  the  instant  of  the  cool  loaf  entering  the 
steam  atmosphere  of  the  oven,  a momentary  condensation  of  steam  occurs 
over  the  whole  surface,  which  is  thus  covered  with  a film  of  water  at  the 
boiling  point.  This  renders  the  starch  of  the  outside  surface  soluble,  and 
as  the  w ater  dries  off  leaves  a glaze  of  soluble  starch,  part  of  w hich  possibly 
has  been  converted  into  dextrin.  The  injection  of  steam  into  the  oven 
not  only  helps  to  dextrinise  and  glaze  the  crust,  but  also  serves  the  purpose 
of  keeping  the  interior  of  the  loaf  moist  by  preventing  too  rapid  evapora- 
tion. 

577.  “ Solid  ” and  “ Flash  ” Heats. — These  terms  are  frequently  used 
fey  the  baker  in  speaking  of  the  character  of  the  heat  of  different  ovens. 
The  former  is  applied  to  heat  which  is  continuous,  the  latter  to  heat  which 
is  very  temporary,  but  frequently  for  the  moment  intense.  It  wull  be  found 
that  the  so-called  “ solid  ""  heat  is  usually  evolved  from  the  walls  of  a w^ell 
heated  oven.  A good  oven  should  have  plenty  of  material  about  it  ; this 
gets  hot  through,  and  afterw^ards  radiates  heat  slowdy  but  continuously. 
If  the  oven  walls  be  too  thin  they  cool  too  quickly  ; in  consequence  they 
have  to  be  heated  very  intensely  at  the  start  ; the  result  is  that  the  oven 
at  first  burns  the  bread,  and  towards  the  end  has  not  heat  enough  to  com- 
plete the  baking  of  the  batch.  With  thicker  walls  the  initial  temperature 
of  the  oven  need  not  be  so  high  ; the  fall  in  temperature  taking  place  more 
slowdy,  the  oven  still  retains  a good  heat  at  the  close  of  the  baking.  The 
heat  which  reaches  the  bread  from  the  w^alls  of  the  oven  is  largely  in  the 
form  knowm  as  “ radiant  heat  ; it  is  continuous,  and  need  not  be  of 
abnormally  high  temperature  in  order  to  thoroughly  and  efficiently  bake 
bread.  The  consequence  is  that  the  interior  of  the  bread  is  w ell  baked,  while 
the  crust  is  not  burned. 

A “ flash  ""  heat,  on  the  other  hand,  is  produced  by  the  contact  of  highly 
heated  gases  with  the  bread.  Certain  varieties  of  ovens  are  fired  by  the 
introduction  of  flame  into  the  oven  itself.  Such  introduction  of  flame 
should  be  employed  to  previously  raise  the  temperature  of  the  oven,  not, 
if  used  at  all,  to  bake  the  bread  itself.  The  reason  is  obvious  ; it  is  exceed- 
ingly difficult  to  regulate  the  temperature  of  a current  of  hot  air  from  a flame 
with  great  exactitude.  The  temperature  is  sufficiently  high  at  one  time 
to  burn  the  crust  ; at  another  so  low  as  to  prevent,  during  the  time  the 
bread  is  in  the  oven,  its  inside  being  sufficiently  cooked.  Further,  if  the  bread 
is  to  be  heated  by  the  hot  air  resulting  from  the  direct  admission  of  flame 
into  the  oven,  there  must  necessarily  be  also  some  means  of  exit  for  the 
gases  from  the  flame.  The  hot  air  from  a furnace  cannot,  in  fact,  be  drawn 
into  the  oven  without  some  means  for  their  after  escape.  The  result  is  that 
these  gases  carry  with  them  the  steam  evolved  from  the  baking  loaves,  and 
so  subject  the  bread  to  a dry,  instead  of  a steam  saturated,  atmosphere. 

578.  Cooling  of  Bread. — The  loaves  on  being  taken  from  the  oven  should 
be  cooled  as  rapidly  as  possible  in  a pure  atmosphere  ; for  this  purpose, 
wiiere  practicable,  open-air  cooling  sheds  should  be  provided.  Failing 
these,  the  cooling-room  must  be  w'ell  ventilated.  It  goes  without  saying 
that  the  cooling  loaves  must  be  adequately  protected  from  rain. 

579.  Summary  of  Conditions  affecting  Speed  of  Fermentation. — Where 
fermentation  starts  with  the  first  addition  of  yeast  to  the  other  materials, 
it  does  not  conclude  till  the  bread  has  been  for  some  time  in  the  oven,  and 
possibly  not  even  then.  At  this  stage  of  w^ork,  with  both  principles  and 
details  of  methods  of  working  explained,  a bird's-eye  view  of  the  whole 
course  of  fermentation  should  be  of  service. 


430 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


A ferment,  when  used,  is  a means  of  making  yeast  by  a process  of  repro- 
duction from  that  originally  added.  Steps  are  taken  at  the  same  time 
to  ensure  vigour  in  the  new  yeast  formed.  The  speed  of  fermentation  of 
the  ferment  is  hastened  by  increase  of  temperature,  but  beyond  a certain 
point  that  of  acid-producing  organisms  is  also  more  than  proportionately 
stimulated.  Aeration  during  fermentation  tends  to  increase  the  vigour  of 
the  produced  yeast.  (Compare  Adrian  Brown  on  the  action  of  oxygen 
on  fermentation,  page  162). 

Assuming  a start  has  been  made  with  either  sponge  or  off-hand  dough, 
the  same  laws  govern  fermentation. 

First,  let  us  see  what  conditions  accelerate  fermentation. 

With  regard  to  yeast,  the  greater  the  quantity,  the  more  quickly  it  pro- 
ceeds : with  sound  yeast  there  is  no  fear  of  imparting  a yeasty  taste  to  bread 
with  many  times  more  than  necessary  for  ordinary  bread- making.  The 
strength  of  the  yeast  will  also  directly  tend  to  increase  the  rate  at  which  fer- 
mentation proceeds. 

Flour. — Soft  flours  tend  to  hasten  fermentation  ; they  contain  more 
sugar  and  more  starch  in  a condition  susceptible  to  diastasis.  Their  pro- 
tein matter  is  more  likely  to  act  as  a yeast  stimulant,  while  the  softness  of 
the  gluten  lessens  a physical  obstacle  to  rapid  action  of  yeast. 

Potatoes,  Saccharine  Extracts. — These  act  as  stimulants,  and  tend  to 
increase  the  speed  of  fermentation. 

Water. — The  principal  way  in  which  this  acts  is  in  virtue  of  the  propor- 
tionate quantity  used.  When  doughs  are  slack,  fermentation  proceeds 
much  more  rapidly. 

Aeration. — Flour  well  aerated  is  likely  to  work  more  rapidly,  especially 
in  slack  sponges.  Notice  how  in  Vienna  bread  and  batter  sponge  is  beaten 
and  worked,  and  how  much  more  vigorous  and  “ lively  ” it  is  in  consequence. 

Temperature. — This  governs  all  ; with  low  temperatures  yeast  works 
very  slowly,  if  at  all,  and  with  higher  temperatures  fermentation  is 
accelerated. 

Next,  as  to  conditions  retarding  fermentation  : these  may  be  summed  up 
as  the  opposite  of  the  accelerating  agents — yeast,  weak  or  in  small  quan- 
tities ; hard,  dry  flours  ; stiff,  unaerated  doughs  ; low  temperature  ; and 
finally,  the  addition  of  salt,  which  has  a very  marked  retarding  effect. 

By  modifying  one  or  more  of  these  conditions,  the  baker  is  able  to  regu- 
late the  speed  of  his  fermentation  ; and,  where  certain  of  them  are  altered 
by  causes  beyond  his  control,  is  able  to  more  or  less  compensate  the  disturb- 
ance by  introducing  changes  in  one  or  more  of  the  others.  Suppose,  for 
example,  the  working  of  a sponge  is  unduly  hastened  by  having  to  use  a 
softer  flour  than  usual,  this  may  be  modified  by  making  it  tighter,  or  working 
with  less  yeast,  or  at  a lower  temperature.  A good  deal  of  the  art  of  the 
baker  consists  in  properly  adjusting  these  variable  factors  so  that  they  shall 
properly  balance  each  other,  and  all  conduce  to  the  production  of  a good 
loaf  of  bread. 

580.  Quick  versus  Slow  Fermentation. — This  is  probably  a convenient 
place  to  make  some  reference  to  the  relative  merits  of  quick  as  against  slow 
fermentation  processes.  One  fact  revealed  by  the  record  of  modern  methods 
given  in  paragraph  539  is  that  as  a whole  the  various  operations  of  baking 
have  been  materially  shortened  during  the  past  few  years.  Reference  is 
made  in  a subsequent  paragraph,  No.  584,  to  some  experiments  on  the  com- 
parative effect  on  acidity  production  of  working  at  comparatively  high  and 
low  temperatures.  The  lesson  taught  by  these  experiments  is  that  for  the 
same  amount  of  alcoholic  fermentation  a comparatively  high  temperature 
is  at  least  not  more  productive  of  acidity  than  a much  lower  one.  These 


BREAD-MAKING. 


431 


tests  were  taken  as  the  starting  point  of  an  investigation  by  one  of  the  authors 
into  the  broader  question  of  the  effect  of  speed  on  bread-making  processes 
generally.  The  results,  of  which  the  following  is  a resume,  were  published 
in  1897.  The  various  baking  tests  were  made  by  Mr.  Ellis,  an  experienced 
baker,  who  was  then  a student  in  the  authors’  laboratory. 

A London  “ whites  ” flour  was  taken  and  worked  throughout  by  means 
of  ferment  and  dough  method.  All  the  water  and  sufflcient  of  the  flour 
were  taken  to  form  a batter  ferment,  the  remainder  of  the  flour  being  used 
in  the  dough. 


Quantities  in  Grams. 

1.  2.  3.  4 


Flour 

. 560 

. . 560  . 

, . 560 

560 

Water 

. 320 

. . 320  . 

. 320 

. . 320 

Yeast 

5 

5 . 

5 

15 

Salt 

6 

6 . 

6 

6 

Temperature  of  water  . 

.70°  F. 

00 

o 

o 

.85°  F. 

. .115°  F. 

Time  taken  to  oven 

.13  hrs. 

. .lOJ  hrs.. 

. 10  hrs. 

. . 3 hrs, 

(Note,  560  grams  are  about  equal  to  20  ounces.  If  these  quantities 
throughout  be  halved  they  give  in  every  case  lbs.  to  the  sack  of  280  lbs.) 

Remarks  on  Working. 

No.  1.  Ferment  started  at  8.0  a.m.,  well  risen  by  12.35,  dropped  4.20 
p.m.,  dough  made  4.35,  ripest  at  7.10,  handed  up  8.5,  least  spring.  When 
baked  was  closer  in  pile,  good  colour  crumb,  few  small  holes,  not  quite  equal 
in  sheen  to  No.  4 ; crust  thin,  rather  dull  in  colour. 

No.  2.  Ferment  started  at  10.20  a.m.,  dropped  5.0  p.m.,  doughed  5.5, 
handed  up  8.20,  fairly  springy.  When  baked,  was  best  loaf  of  those  slow 
worked.  Good  pile  and  colour,  crumb  better  texture  than  others.  Nice 
coloured  crust,  good  appearance,  and  best  shaped. 

No.  3.  Ferment  started  10.35,  dropped  4.15,  doughed  4.30,  handed  up 
8.10,  moulded  well,  fairly  springy,  good  colour  crumb,  fair  sheen,  very  sweet 
to  smell  and  taste,  not  quite  so  good  a texture  or  appearance  in  crust  as 
others. 

No.  4.  Ferment  started  at  10.0  a.m.,  dropped  at  11.30,  made  up  11.37, 
skin  just  cracking  12.32  when  handed  up,  moulded  12.50.  Much  the  boldest 
and  best  when  baked,  good  pile,  good  crumb,  few  small  holes,  rather  best 
sheen,  not  quite  so  sweet  to  smell,  but  nicer  flavour  to  palate  than  No.  1. 
Crust  thin  and  good  colour,  although  well  baked. 

In  the  table  on  page  432  the  working  character  and  keeping  qualities  are 
summarised.  Percentages  are  also  given  of  acid  reckoned  as  lactic  acid, 
sugar  reckoned  as  maltose,  and  soluble  matter  in  the  breads. 

The  general  conclusions  to  be  drawn  from  this  series  of  experiments  is 
in  favour  of  the  quick  fermentation  method.  It  is  somewhat  curious  to 
And  that  the  long  fermentation  loaf  dried  off  the  quicker,  especially  as  there 
is  a somewhat  widespread  opinion  that  short  fermentation  bread  loses  its 
moisture  the  more  rapidly. 

In  the  next  place  experiments  were  made  with  larger  quantities  ; straight 
doughs  being  employed,  in  order  to  determine  the  minimum  of  time  in 
which  they  could  be  satisfactorily  fermented.  The  following  are  particulars 
of  quantities  and  temperatures  : — 


1. 

2. 

3. 

4. 

280  lbs.  of  flour  at 

72°  F. 

70°  F. 

68°  F. 

70°  F 

Water  at 

85°  F. 

95°  F. 

112°  F 

105  F. 

Yeast 

20  oz. 

19  oz. 

18  oz. 

22  oz. 

Salt 

3 lbs. 

3 lbs. 

3 lbs. 

3 lbs, 

Temperature  of  dough 

when  made 

91°  F. 

432 


THE  TECHNOLOGY  OF  BHEAD-MAKING. 


No. 

Character  in 
Working. 

Keeping  Quality  and  Flavour. 

I Sweetness. 

Acidity. 

Maltose 

Soluble 

Matter. 

1 

Very  little  spring, 
dead  to  handle 
all  the  way 
through. 

1st.  day — Slightly  drier 
than  No.  4.  Not  so 
good  flavour. 

4th.  day — Considerably 
the  driest  when  cut. 

6th.  day — Much  the 

driest. 

! " 

! Smells 
sweet. 

0-18 

0-32 

6-04 

2 

1 

1 

i 

F airly  springy, 
moulded  well. 

1 

1st.  day — Rather  moister 
than  1 or  4,  and  better 
flavour. 

4th. day — Keeps  its  moist- 
ness. 

6th,  day — Has  not  kept 
its  moistness  as  well  as 
No.  4 for  the  longer 
time. 

Sweetest 
to  smell 
and  taste. 

0-20 

0-35 

4-28 

3 

Rather  more 

springy  than 
No.  2,  but  not 
so  good  as  No. 
4,  handled 

well. 

1st.  day — The  moistest. 

4th.  day — Kept  much 
moister. 

6th.  day — About  as  moist 
as  No.  4.  Sweeter  in 
flavour. 

Very 

sweet, 

0-18 

0-28 

5-68 

4 

Handled  well  ; 
full  of  spring. 

1st.  day — Rather  moister 
than  No.  1. 

4th.  day — Much  the 

moistest. 

6th.  day — Moistest  and 
good  flavour.  The 

'pleasantest  flavour  of 
all. 

Does  not 
smell  so 
sweet. 

019 

OdO 

5-28 

Remarks  on  Working. 

No.  1 was  taken  5 hours  after  being  made,  and  set  in  oven  in  another 
50  minutes.  Loaf  of  good  appearance  and  very  sweet.  Dough  might  have 
been  taken  half-an-hour  sooner  without  injury. 

No.  2.  Taken  3J  hours  after  making,  and  set  in  oven  in  another  50 
minutes.  Good  bold  loaf,  no  foxiness,  very  sweet. 

No.  3.  Made  2 quarts  of  water  slacker  than  No.  2.  Fifteen  pounds 
of  flour  were  reserved  and  dusted  in  when  the  dough  was  cut  back  at  the 
end  of  2 hours.  Taken  3 hours  after  making.  Loaf  small  and  runny,  pro- 
bably rather  more  time  required. 

No.  4.  Taken  at  end  of  3 hours,  in  oven  in  3|  hours.  Bread  small  and 
rather  flat. 

A repeat  was  next  made  of  No.  2,  with  the  result  that  the  loaf  was  in 
every  way  satisfactory  and  compared  favourably  with  bread  made  from 
tlie  same  flour  by  a long  system  of  fermentation. 

The  whole  of  these  were  fairly  stiff  doughs  for  crusty  cottage  bread, 
probably  the  same  degree  of  stiffness  as  is  employed  in  London  for  bread  of 
this  kind.  It  was  found  that  a working  time  of  3J  to  3|  hours  was  the  best 
to  employ,  as  when  an  effort  was  made  to  get  down  to  3 hours  the  bread  fell 
off  in  quality.  Endeavours  were  made  to  shorten  the  time,  both  by  raising 
the  temperature  and  increasing  the  yeast,  but  the  results  in  neither  case 
could  be  considered  encouraging.  No  doubt  with  slacker  doughs  such  as 
are  made  for  tinned  bread,  the  time  might  still  further  be  shortened.  The 


BREAD-MAKING. 


433 


flour  used  was  a bard  mixture  and  required  to  be  fermented  sufficiently  to 
be  free  working,  and  not  yield  a pinched  loaf.  Softer  flour  again  would 
work  through  in  less  time.  The  conclusions  drawn  were  that  in  appearance 
and  general  character  at  least  as  good  a loaf  can  be  obtained  by  quick  as 
by  slow  fermentation  processes.  The  subsequent  adoption  of  quick  processes 
by  so  large  a proportion  of  bakers  is  an  ample  justification  of  the  forecast  of 
1887. 

581.  Summary  of  Course  of  Fermentation. — A very  useful  lesson  may  be 
learned  by  making  a batch,  say  of  20  lbs.  of  flour,  into  a slack  dough,  with 
a full  allowance  of  distillers'  yeast,  say  3 ounces  ; salt  and  water  in  pro- 
portion, and  working  the  batch  fairly  warm.  Let  a piece  be  cut  off  and 
moulded  into  a loaf  immediately  the  dough  is  made,  and  at  once  baked — 
the  result  vill  be  a close,  small,  very  moist  loaf,  not  much  bigger  than  the 
piece  of  dough  cut  off.  Next  bake  a similar  loaf  from  the  same  piece  of  dough 
at  the  end  of  every  hour  from  the  time  of  starting,  keeping  the  main  mass 
covered,  and  in  a warm  place.  An  instructive  series  of  changes  will  be  ob- 
served in  the  successive  loaves.  In  boldness  the  bread  improves  for  some 
hours,  then  remains  stationary,  and  finally  becomes  “ runny  " and  flat. 
The  colour  of  the  crust  is  at  first  “ foxy,”  then  of  a golden  yellow  or  brown 
tint,  and  finally  abnormally  pale.  The  crumb  during  the  first  three  or 
four  loaves  of  the  series  gradually  improves,  and  becomes  more  bloomy, 
then  changes  to  a greyish  white,  losing  the  bloom,  and  then  “ saddens  ” 
and  darkens,  becoming  a dull,  cold  grey,  merging  ultimately  into  a brown. 
At  the  same  time  it  becomes  ragged  on  the  outside  edges,  and  dark  where 
a soft  crust  has  been  produced  by  two  loaves  being  in  contact  with  each 
other  in  the  oven.  In  flavour,  the  first  loaf  will  be  sweet,  but  “ raw  ” and 
“ wheaty,”  characters  which  will  be  lost  as  fermentation  proceeds  ; at  its 
best  the  raw  taste  mil  have  gone,  leaving  only  a sweet  clean-palate  flavour. 
This  will  be  succeeded  by  a gradual  disappearance  of  the  sweetness,  the 
bread  being  neutral  and  tasteless  : at  the  same  time  the  loaf  will  have  lost 
its  moisture,  and  will  be  harsh  and  crumbly.  As  fermentation  is  pushed  still 
further,  the  bread  commences  to  be  “ yeasty  ” (to  taste  of  the  yeast)  ; but 
this  depends  somewhat  on  the  original  soundness  or  otherwise  of  the  yeast. 
This  condition  merges  into  one  of  slight  sourness,  first  of  pure  lactic  acid 
flavour,  accompanied  by  buttermilk  odour  ; but  gradually  becoming  worse, 
until,  finally,  not  only  is  the  taste  offensive,  but  so  also  is  the  smell,  partaking 
not  only  of  sourness  in  character,  but  also  of  incipient  putrefaction  and 
decomposition.  During  these  latter  stages  the  bread  again  becomes  soft 
and  clammy.  The  first  drying  off,  until  the  bread  reaches  the  harsh  stage, 
is  due  to  the  disappearance  of  soluble  starch  and  dextrin  by  diastasis  into 
sugar,  and  then  fermentation  : the  subsequent  clamminess  is  the  result 
of  degradation,  not  only  of  a portion  of  the  starch,  but  also  the  insoluble 
proteins  of  the  dough. 

Such  are,  in  brief,  the  changes  observable  in  dough  under  ordinary 
conditions  of  working,  from  the  first  start  of  fermentation  to  the  com- 
mencement actually  of  putrefaction.  These  may  be  slightly  modified  by 
character  of  the  flour  and  other  constituents  of  the  dough  ; but  if  the  con- 
ditions of  fermentation  be  healthy  and  normal,  the  whole  series  of  changes 
substantially  follows  the  order  given  here.  Changes  in  temperature,  degree 
of  stiffness  of  doughs,  etc.,  within  recognised  and  approved  limits,  may  accelerate 
or  retard  fermentation  as  a whole,  but  they  do  not  alter  its  character  and  general 
course. 


Sour  Bread. 

582.  Souring  of  Bread. — ^When  dough  has  been  allowed  to  overwork  a 


434 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


frequent  consequence  is  that  the  resultant  bread  is  sour.  Among  the  earlier 
views  of  the  causes  of  such  sourness  was  that  which  regarded  it  as  being 
due  to  the  oxidation  of  alcohol.  A fully  worked  sponge  or  dough  contains 
considerable  quantities  of  that  substance,  and  it  was  argued  that  the  well- 
known  change  of  alcohol  into  acetic  acid  by  oxidation, 

C2H5HO  + 02=:  HC2H3O2  + H2O, 

Alcohol.  Oxygen.  Acetic  Acid.  Water. 

was  the  cause  of  the  acidity  of  sour  bread,  especially  from  overwrought 
sponges  or  doughs. 

It  will  be  convenient  at  this  early  stage  to  differentiate  between  ‘‘  acid- 
ity ""  and  “ sour  bread,""  using  each  of  these  terms  in  their  generally  accepted 
sense.  “ Acidity  ""  is  a chemists"  term  and  is  caused  by  the  presence  of 
free  acid  ; the  measure  of  acidity  is  the  amount  of  alkali  of  definite  strength 
required  to  produce  neutrality.  “ Sour  bread  "’  is  a baker "s  term,  and  is 
applied  to  bread  which  has  a sour  odour  and  flavour  to  the  organs  of  smell 
and  taste  respectively.  Experiments  show  that  acidity,  as  measured  by 
chemical  means,  and  sourness,  as  judged  in  bread  by  the  nose  and  palate, 
are  not  necessarily  alike  in  intensity  or  entirely  dependent  on  each  other : 
for  this  reason  the  limitation  of  the  sense  in  which  the  authors  personally  use 
each  term  is  here  indicated. 

As  opposed  to  what  may  be  called  the  acetic  acid  hypothesis,  it  must 
be  remembered  that  yeast  has  a great  avidity  for  oxygen,  and  according 
to  Pasteur"s  view  alcoholic  fermentation  was  a starvation  phenomenon 
in  the  absence  of  oxygen.  This  theory  is  no  longer  tenable,  but  in  any 
case  the  fact  remains  that  yeast  readily  absorbs  oxygen  from  any  fluid 
in  which  it  is  actively  at  work.  As  the  acidity  of  a sponge  or  dough  is  the 
effect  of  acid  fermentation  following  the  normal  alcoholic,  there  cannot  be 
within  the  mass  of  dough  any  oxygen  by  which  the  alcohol  disseminated 
through  it  can  be  oxidised  to  acetic  acid.  For  this  reason,  therefore,  it  is 
only  on  the  surface  of  the  dough  exposed  to  air  that  such  action  is  possible. 
And  even  here  it  must  be  exceedingly  superficial,  for  in  the  presence  of  the 
possibly  slow,  but  continuous,  exhalation  of  gas  from  the  sponge,  it  is  very 
improbable  that  any  perceptible  absorption  of  oxygen  is  occurring.  Even 
when  quiescent,  it  must  be  remembered  that  a sponge  contains  an  abun- 
dance of  yeast  ready  to  start  again  in  active  fermentation  as  soon  as  supplied 
with  food.  There  will  therefore  be  on  the  surface  of  such  a sponge  yeast  in 
far  greater  plenty  than  acetic  acid  germs,  and  with  the  greater  vigour  of 
the  former  organism,  it  is  a fair  assumption  that  of  the  very  limited  amount 
of  surface  assimilation  of  oxygen,  the  lion"s  share  will  be  taken  by  the  yeast 
and  converted  into  carbon  dioxide.  As  both  lactic  and  butyric  acids  are 
products  of  anaerobic  ferments,  and  are  the  result  of  chemical  changes 
which  are  absolutely  independent  of  external  free  oxygen,  the  same  objec- 
tions do  not  apply  to  these  as  sources  of  acidity.  For  these  very  cogent 
a 'priori  reasons,  the  authors  have  viewed  the  presence  of  acetic  acid  as  being 
(under  any  normal  conditions  such  as  are  commonly  found  in  a bakery) 
an  exceedingly  limited  and  practically  negligible  cause  of  acidity. 

583.  Sour  Bread,  Briant.— Briant  has  contributed  a number  of  impor- 
tant papers  to  this  subject  and  gives  the  following  results  of  analysis  of 
samples  of  dough  by  Duclaux"s  method  of  fractional  distillation  : — 

“ I should  mention  that  the  yeast  used  w^as  in  each  that  of  the  Delft  Com- 
pany, a brand  which  may  be  regarded  as  practically  free  from  bacteria.  This 
point  is  one  of  much  importance,  as  will  be  seen  when  in  the  second  section 
of  this  paper  w^e  consider  the  causes  of  the  production  of  these  acids. 

“It  is  well  also  to  bear  in  mind  that  lactic  acid  does  not,  weight  for 
weight,  correspond  to  the  same  acidity  as  acetic  acid.  Three  parts  by 


BREAD-MAKING. 


435 


weight  of 
acid. 

‘A.’ 


lactic  acid  have  the  same  acidity  as  two  parts  by  weight  of  acetic 


(Fresh  dough  )- 
Lactic  Acid 
Acetic  Acid 
Butyric  Acid 


B.^— 


C.’ 

‘D.' 

‘F.^- 

G.^ 


Lactic  Acid 
Acetic  Acid 
Butyric  Acid 
(Very  acid  dough)- 
Lactic  Acid 
Acetic  Acid 
Butyric  Acid 
(Same  dough  kept 
Lactic  Acid 
Acetic  Acid 
Butyric  Acid 

Lactic  Acid 
Acetic  Acid 
Butyric  Acid 

Lactic  Acid 
Acetic  Acid 
(The  same  dough 
Lactic  Acid 
Acetic  Acid 
Butyric  Acid 


(about) 


another  day)- 


•024  per  cent. 
•038 
None. 

•405  per  cent. 
•150 
•06 

•622  per  cent. 

•245 

Trace. 

•742  per  cent. 
•249  „ 

Distinct  trace. 

•493  per  cent. 
•175  „ 

Trace. 


•460  per  cent. 

. . -197 

kept  three  days  longer,  then  extremely  acid)- 
D08  per  cent. 

. . -231  „ 

Heavy  trace. 


“ The  above  results  clearly  show  that  the  bulk  of  the  acidity  in  acid 
bread  is  due  to  lactic  acid,  but  that  a certain  proportion,  varying  from  one- 
third  to  one-fifth,  consists  of  acetic  acid,  and  that  in  most  of  the  samples 
the  amount  of  butyric  acid  is  very  small.  The  samples  in  which  I have 
found  butyric  acid  have  been  made  in  most  cases  from  inferio  flour  and 
bad  yeast,  and  the  connection  between  these  and  butyric  acid  is  very  close, 
as  I shall  be  able  to  show  in  my  next  article  on  the  subject.  I believe,  on 
the  strength  of  the  above  figures,  that  I may  claim  to  have  proved  what 
are  the  acids  present  in  flour,  for  I have  separated  the  acids  by  recognised 
methods  in  a fair  number  of  samples.  It  is  the  acetic  acid  which,  together 
with  butyric  acid  (if  present),  gives  the  smell  to  sour  dough — lactic  itself 
being  non-volatile  has  no  smell — therefore,  were  dough  acid  with  lactic 
acid  alone,  it  would  have  no  sour  smell,  although,  of  course,  it  would  taste 
acid.’" 

Briant  then  remarks  that  “ practical  experience  has  shown  that  sour 
bread  is  obtained  most  readily  with  bad  yeast,  common^  flour,  and  when 
high  temperatures  are  employed,  whilst  the  same  result  is  favoured  by 
over-fermentation,  a slack  dough,  dirty  yeast  troughs,  and  over-exposure 
to  the  air  during  the  doughing  stages.  Any  satisfactory  solution  should  be 
able  to  explain  why  it  is  in  practice  that  the  conditions  which  I have  named 
favour  the  production  of  sour  bread.” 

By  systematic  bacteriological  investigation,  Briant  found  micro-organ- 
isms ; and  in  sour  dough  identified  lactic  and  acetic  ferments,  and  in  some 
cases,  also  the  butyric  ferment.  Oh  inhibiting  bacterial  action  by  the 
addition  of  chloroform,  dough  is  absolutely  prevented  going  acid.  The 
conclusion  is  therefore  drawn  that  acidity  is  due  to  bacterial  action.  The 


436 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


next  point  for  consideration  was  the  source  of  these  bacteria,  which  were 
searched  for  among  the  following — water,  air,  yeast,  dirty  vessels,  and  flour. 

Practically,  the  results  were  negative  with  w^ater  and  air.  It  was  found 
just  as  easy  to  get  sour  bread  with  sterilised  water  as  with  an  ordinary 
town  supply.  So,  too,  exposure  to  ordinary  air  containing  micro-organisms 
did  not  produce  any  appreciable  difference  in  the  acidity  of  dough  from 
that  produced  by  sterihsed  air. 

Many  modern  yeasts  are  practically  bacteria-free,  and  while  an  impure 
yeast  may  cause  sour  bread,  yet  Briant  produced  sour  dough  with  a pure 
yeast-culture  from  a single  cell.  Whilst  yeast  therefore  may  cause  sour 
bread,  it  is  at  any  rate  not  the  only  cause  for  it.  Dirty  vessels,  it  almost 
goes  without  saying,  are  a most  fruitful  source  of  acidity. 

Briant  found  flour  itself  to  be  a most  potent  factor  in  producing  acidity. 
Thus,  he  remarks  that  “ until  I had  examined  a considerable  number  of 
flours,  I did  not  realise  fully  how  important  an  influence  they  must  have 
upon  the  soundness  of  bread.  But  having  made  bacteriological  examina- 
tions of  a large  number  of  samples,  I am  led  to  the  conclusion  that  it  is  here 
that  we  meet  with  a very  decided  cause  of  sourness  in  bread.  The  differ- 
ences between  flours  in  this  respect  are  very  great,  indeed  some  are  com- 
paratively— although  none  are  absolutely — free  from  bacteria,  but  others 
contain  very  large  quantities,  and  amongst  them  it  is  possible  to  very 
readily  separate  the  lactic  and  the  acetic  ferment.  In  every  case  of  sour 
dough,  I have  found  the  flour  to  contain  acid-producing  ferments.  In  a 
low-class  flour,  which  in  practice  was  found  to  very  readily  yield  sour 
bread,  unless  worked  with  much  care,  we  And  in  the  flour  itself  precisely 
those  ferments  which  are  afterwards  found  in  the  dough  and  act  as  acid 
producers,  and  here  we  have  the  real  cause  of  the  acidity.  Where  the 
flour  used  by  a baker  contains  any  but  a very  small  proportion  of  bacteria, 
there  will  always  be  a certain  risk  of  acidity.  By  careful  working  the 
baker  may  reduce  this  risk,  and  particularly  if  he  uses  a commercially  pure 
yeast  and  observes  scrupulous  cleanliness.  He  may  find  it  perfectly  pos- 
sible to  produce  bread  which  is  quite  sound,  despite  the  fact  that  the  flour 
contains  many  bacteria.  For  several  considerations  bear  upon  the  growth 
of  these  bacteria.  First  is  that  of  temperature.  The  activity  of  the  lactic 
ferment,  according  to  De  Bary,  increases  as  the  temperature  rises,  up  to 
a certain  point.  It  grows  and  produces  acidity  comparatively  slowly  at  a 
temperature  of  60°,  but  at  temperatures  exceeding  70°  it  becomes  extremely 
active.  It  reaches  its  maximum  of  activity  at  about  108°,  above  which 
temperature  it  rapidly  declines  in  power.  The  acetic  ferment  reaches 
its  maximum  at  a temperature  between  85°  and  93°,  at  which  latter  tem- 
perature its  power  of  reproduction  and  acidification  is  enormously  rapid. 
From  these  considerations  it  is  therefore  at  once  apparent  that  whilst 
high  temperatures  for  panary  fermentation  are  in  all  cases  undesirable^ 
yet  in  cases  where  low-class  flours  are  used,  they  are  almost  fatal.  In  low- 
class  flours  also  there  is  almost  invariably  present  a large  excess  of  objec- 
tionable nitrogenous  bodies.  These  bodies  are  particularly  suitable  as  a 
nidus  upon  which  the  bacteria  caja^eed,  so  that  in  low-class  flour  we  have 
^hese  additional  causes  of  risk,  regain,  another  very  important  circum- 
stance which  contributes  to  sour  oread  is  over-fermentation,  and  the  cause 
of  this  is  very  simple.  So  long  as  the  yeast  is  vigorously  working,,  so  long 
are  the  bacteria  kept  in  check,  and  just  as  in  the  fermentation  of  wort  in 
a brewery,  we  find  that  though  bacteria  are  present,  yet  the  wort  itself 
remains  free  from  acid  until  the  yeast  has  ceased  its  work,  so  in  baking 
the  bacteria  are  held  in  check  whilst  the  fermentation  is  vigorous.  Imme- 
diately, however,  the  fermentation  flags,  the  bacteria  commence  to  act, 
and  this  is  particularly  the  case  with  the  acetiC'  ferment,  which  at  this 


BREAD-MAKING. 


437 


stage  is  supplied  with  the  alcohol  which  it  converts  through  aldehyde 
into  acetic  acid.  , In  fact,  whilst  it  is  possible  for  some  small  quantity  of 
"lactic  acid  to  be  produced  concurrently  with  the  procedure  of  fermentation 
by  the  yeast,  this  is  practically  impossible  in  the  case  of  the  acetic  ferment, 
which  will  only  commence  to  act  after  the  yeast  has  finished  its  work.  But 
in  order  that  the  acetic  ferment  may  convert  the  alcohol  into  acetic  acid, 
it  requires  the  presence  of  some  oxygen.  Therefore  it  is,  that  the  more 
a dough  is  kept  free  from  exposure  to  air,  the  less  chance  of  production 
of  acetic  acid  there  is,  and  the  practical  experience  of  the  baker  has  led 
him  to  adopt  what  is  ^practically  accurate  from  a scientific  point  of  view, 
viz.,  the  exclusion  of  air  so  far  as  is  possible  during  the  fermentation  pro- 
cess. Again,  the  production  of  acidity  is  far  more  rapid  if  the  dough  is 
slack.  When  this  is  the  case,  the  bacteria  are  able  to  thrive  far  more  rapidly 
and  vigorously  than  is  the  case  with  a stiff  dough,  and  in  some  experiments 
which  I have  made  as  to  the  speed  of  souring  of  a stiff  versus  slack  dough, 
I have  found  a remarkably  increased  rapidity  of  souring  with  the  latter, 
and  there  can  be  no  question  but  that,  from  the  point  of  view  of  soundness 
of  bread,  the  dough  should  be  kept  as  stiff  as  is  practicable. 

“ Finally,  therefore,  I may  summarise  my  conclusions  as  follows  : — 

“I.  The  acids  of  sour  bread  are  acetic  and  lactic  acids,  with  occasional 
small  quantities  of  butyric  acid.  Lactic  acid  in  most  cases  is  present  to  the 
extent  of  two  or  three  times  that  of  the  acetic  acid. 

“ 2.  The  acid  is  produced  by  bacteria  to  be  found  in  the  dough. 

3.  These  bacteria  may  be  introduced  by  the  yeast,  by  the  use  of  dirty 
vessels,  and  by  the  flour,  but  their  presence  in  the  flour  is  the  most  general 
cause  of  acidity.  Some  high-class  flours  contain  very  few  bacteria  ; low- 
class  flours  are  often  simply  teeming  Avith  them. 

“ 4.  The  use  of  high  temperatures  facilitates  the  activity  of  the  bacteria 
which  may  be  present,  and  is  therefore  objectionable. 

“ 5.  The  bacteria  are  present,  but  do  not  to  any  large  extent  become 
active  until  the  alcoholic  fermentation  commences  to  flag.  Hence,  over- 
proved dough  is  specially  liable  to  acidity. 

“ 6.  Slackness  of  dough  contributes  to  the  activity  of  bacteria,  and 
therefore  is  undesirable. 

7..  Exposure  to  air,  by  supplying  the  acetic  ferment  with  oxygen, 
favours  its  activity,  and  therefore  fermenting  dough  should  be  kept  as  much 
out  of  contact  with  air  as  is  possible.” 

Briant’s  papers  represented  a most  important  piece  of  work  on  the 
Subject  of  sour  bread,  and  embodied  some  most  valuable  conclusions,  the 
principal  among  these  being  the  establishment  of  the  connection  between 
bacteria  present  in  dough  and  its  acidity,  and  the  further  emphasising  of 
the  fact  that  a most  fruitful  source  of  acidity  is  the  presence  of  bactleria  in 
flour.  (Compare  with  the  paragraph  on  the  comparative  bacterioogical ; 
purity  of  flours  in  Chapter  XXI.)  It  had  long  been  known  to  bakers  that, 
Avorking  under  precisely  the  same  conditions,  sourness  is  far  more  likely 
to  occur  in  “ seconds  ” than  in  “ best  ” bread,  but  this  particular  reason — 
the  greater  prevalence  of  bacteria  in  low-grade  flours — had  here  for  the 
first  time  its  due  importance  ascribed  to  it. 

584.  Personal  Researches. — The  authors  have  devoted  much  attention, 
both  in  the  bakery  and  also  the  laboratory,  to  this  problem  of  sour  bread. 
As  a result,  they  find  themselves  unable  to  agree  Avith  some  of  the  foregoing 
opinions,  and  in  the  folloAving  paragraphs  endeavour  to  explain  the  reasons 
for  their  inability  to  agree  Avith  the  same. 

The  first  point  is  the  promulgation  of  the  vieAV  that  acetic  acid  is  so 
largely  found  in  sour  dough.  As  already  explained,  there  are  very  cogent 


438 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


a priori  reasons  for  the  improbability  of  any  great  amount  of  acetic  acid 
being  found  in  panary  fermentation  ; and  Briant  recognises  that  acetous 
fermentation  must  be  an  after  fermentation,  “ which  will  only  commence 
to  act  after  the  yeast  has  finished  its  work.'’  On  examination  of  Briant's 
analytic  results,  one  is  at  once  confronted  with  the  fact  that  in  fresh  dough, 
sample  A,  there  is  a higher  proportion  of  acetic  acid  than  in  any  of  the  others. 
Analyses  C and  D are  of  the  same  sample,  made  at  an  interval  of  a day  : 
during  this  time  the  lactic  acid  has  materially  increased,  while  the  acetic 
acid  remains  stationary.'  Analyses  F and  G are  also  made  on  the  same 
dough,  but  with  a three  days"  interval  ; the  lactic  acid  has  increased  from 
0*464  to  1*08,  or  to  2*35  times  its  original  quantity.  The  acetic  acid  has 
similarly  risen  from  0*197  to  0*231,  and  is  1*17  times  its  original  quantity. 
Although  acetic  acid  is  undoubtedly  the  result  of  an  after  fermentation, 
yet  a relatively  higher  proportion  is  found  in  fresh  than  in  stale  doughs  ; 
in  these  experiments  almost  the  whole  of  the  after  developed  acidity  is  due 
to  lactic,  and  not  acetic,  acid. 

Following  is  an  account  of  an  independent  series  of  experiments,  made 
with  the  view  of  investigating  the  causes  of  souring  of  bread.  Some  of  this 
w^ork  was  done  prior  to  the  publication  of  Briant’s  researches,  and  a portion 
of  the  remainder  was  suggested  by  the  results  of  his  researches. 

The  determinations  of  the  different  acids  were  made  by  various  processes 
described  in  Chapter  XXVIII.,  including  the  application  of  the  method  of 
Duclaux. 

As  a preliminary  to  the  analyses,  various  tests  were  made  on  the  methods 
themselves.  It  is  obvious  that  the  separation  of  lactic  from  acetic  and 
butyric  acids  by  the  process  of  distillation  is  only  trustwwthy  on  the  assump- 
tion that,  under  the  conditions  of  the  estimation,  lactic  acid  is  non-volatile. 
But  in  Miller’s  Elements  of  Chemistry  [Armstrong  A;  Groves),  it  is  stated  that 
“ on  distilling  an  aqueous  solution  of  lactic  acid,  a certain  amount  of  acid 
volatilises  with  the  steam."  In  order  to  investigate  this  point,  the  following 
experiments  were  made  : — A sample  of  lactic  acid  w^as  taken,  which  had 
been  sold  as  chemically  pure  ; this  was  tested  for  acetic  and  butyric  acids, 
but  gave  no  indication  whatever  of  a trace  of  them  being  present.  This 
was  diluted  with  pure  distilled  w^ater,  free  from  carbon  dioxide,  and  abso- 
lutely neutral  to  phenolphthalein,  until  of  a strength  equivalent  to'y^o  of 
that  of  centinormal  acid.  In  a distilling  apparatus,  consisting  of  a Wurtz 
flask  and  glass  (Liebig’s)  condenser,  110  c.c.  of  this  dilute  acid  w^as  sub- 
jected to  distillation  until  100  c.c.  had  come  over  : the  distillate  on  titra- 
tion possessed  an  acidity  equal  to  2*1  c.c.  of  centinormal  acid.  The  residuum 
in  the  flask  when  titrated  was  found  to  require  63*3  c.c.  of  centinormal 
soda.  In  another  experiment  the  original  acidity  was  equivalent  to  45 
C.C.,  that  of  the  100  c.c.  of  distillate  to  3*7,  and  that  of  the  residual  10  c.c. 
to  35*1  c.c.  of  centinormal  acid.  In  the  one  case  about  a thirty-seventh,  and 
in  the  other  a tw'elfth,  of  the  total  lactic  acid  had  come  over  with  the  distil- 
late. It  may  be  taken  as  a general  result  that,  working  with  very  dilute 
acids,  the  quantity  of  lactic  acid  found  in  the  distillate  is  not  very  large, 
but  it  is  to  be  feared  that  it  is  liable  to  obscure  conclusions  based  on  Du- 
claux’s  system  of  fractionation.  It  Avill  be  noticed  that  in  these  experi- 
ments there  is  a considerable  loss  of  acid,  as  the  sum  of  the  acidity  of  the 
distillate  and  the  residuum  does  not  agree  with  that  of  the  quantity  of  acid 
originally  taken.  In  order  to  determine  whether  there  was  any  loss  by  a 
portion  of  the  acid  escaping  condensation,  the  apparatus  was  fitted  with 
nitrogen  bulbs  containing  centinormal  soda,  as  shown  in  Fig.  116.  In  a 
number  of  experiments  higher  and  more  regular  results' were  thus  obtained, 
showing  that  some  of  the  acid  escaped  as  steam.  This  was  particularly 
noticeable  when  the  distillation  was  accompanied  by  “ bumping.”  Still 


BREAD-MAKING. 


439 


the  amount  of  loss  thus  accounted  for  was  nothing  like  sufficient  to  cover 
the  whole  of  the  deficiency. 

A further  investigation  was  made  as  to  the  reaction  to  acids  of  the 
flasks  themselves,  and  it  was  found  that  the  alkalinity  of  a number  of  flasks 
was  more  than  sufficient  to  entirely  vitiate  the  result  of  experiments  made 
with  them.  Thus,  for  the  purpose  of  testing,  110  c.c.  of  distilled  water, 
free  from  carbon  dioxide  and  neutral  to  phenolphthalein,  were  distilled  in  a 
Wurtz  flask  until  reduced  to  10  c.c.  This  residuum  was  titrated,  and  re- 
quired 13*6  c.c.  of  centinormal  acid.  Another  110  c.c.  of  the  same  water 
was  boiled  down  in  a platinum  basin,  and  the  remaining  10  c.c.  titrated  : 
0*1  c.c.  of  N/lOO  acid  produced  distinct  acid  reaction.  New  flasks  are 
found  to  yield  a much  larger  quantity  of  alkali  to  water  than  old,  and  no 
doubt  the  glass  of  some  flasks  is  far  more  soluble  than  that  of  others.  Thus 
affiew  400  c.c.  Wurtz  flask  was  washed  thoroughly,  rinsed  in  dilute  sulphuric 
acid,  then  washed  with  distilled  water,  and  attached  to  a “ return  condenser 
(see  fat  determination.  Fig.  113,  Chapter  xxvii.).  In  the  flask  were  placed 
250  c.c.  of  distilled  water,  3 drops  phenolphthalein,  and  1 c.c.  of  decinormal 
acid.  The  leading  tube  of  the  flask  was  closed,  and  the  water  caused  to 
boil  until  a pink  colouration  appeared.  Another  c.c.  of  decinormal  acid 
was  then  added  and  the  boiling  continued,  this  operation  being  several 
times  repeated.  The  following  are  the  results  : — 


1st.  c.c.  of  acid  was  neutralised  by  alkali  dissolved 

from  flask  in  . . . . . . . . . . 35  minutes. 

2nd.  c.c.  of  acid  ,,  ,,  ,,  28  ,, 

3rd.  c.c.  of  acid  ,,  ,,  ,,  37  ,, 

4th.  c.c.  of  acid  ,,  ,,  ,,  45  ,, 

5th.  c.c.  of  acid  ,,  ,,  ,,  40 


In  the  next  place  a flask  of  “ Jena  Utensil  Glass  was  similarly  tested. 
One  c.c.  of  decinormal  acid  was  added  to  water,  as  before,  and  the  boiling 
continued  for  2 J hours  ; at  the  end  of  which  the  contents  of  the  flask  w^ere 
titrated,  and  found  to  possess  an  acidity  of  0*5  c.c.,  showing  that  only  0*5 
c.c.  of  decinormal  acid  had  been  neutralised  in  that  time. 

The  following  experiment  may  now  be  described  : — A mixture  of  one 
part  “ Red  Dog  ''  flour  with  four  of  baker's  grade  spring  American  flour 
was  made.  There  were  taken  3 lbs.  of  this  mixture,  | oz.  distillers'  yeast, 
J oz.  salt,  and  very  warm  water.  A sponge  was  first  made,  which  had  a 
temperature  of  109°  F.,  afterwards  a dough  which  stood  at  84°  F.  The 
sponge  and  dough  stood  altogether  24  hours  in  a warm  place,  and  then  smelt 
sour  and  incipiently  putrescent.  During  the  time  of  standing  it  was  freely 
exposed  to  the  air,  and  several  times  was  “ handed  up  " so  as  to  work 
the  outer  skin  into  the  mass  of  the  dough. 

At  the  end  of  this  time  a portion  of  the  dough  was  reserved  for  direct 
tests,  and  the  remainder  baked  slowly  in  a slack  oven.  (The  object  of  the 
whole  of  the  treatment  was,  of  course,  to  get  as  sour  a sample  as  was  well 
possible.) 

Dough. — To  determine  total  acidity  10  grams  of  the  dough  were  taken, 
broken  down  with  neutral  distilled  water  and  titrated  with  N/IO  soda 
and  phenolphthalein  (this  indicator  was  used  throughout)  : — required, 
10*9  c.c.  = 0*981  per  cent,  of  total  acidity,  reckoned  as  lactic  acid. 

For  the  subsequent  tests  50  grams  of  dough  were  taken  and  made  up 
to  400  c.c.  with  distilled  water,  1 c.c.  of  chloroform  having  been  added. 
This  was  thoroughly  mixed  by  repeated  shakings,  and  allowed  to  stand 
over  night  : of  the  clear  supernatant  liquid,  230  c.c.  were  pipetted  off  the 
next  morning.  In  10  c.c.  of  this  the  acidity  was  determined,  being  equiva- 
lent to  11*8  c.c.  of  centinormal  acid.  Of  this  liquid,  110  c.c.  were  taken 


440  THE  TECHNOLOGY  OF  BREAD-MAKING. 

and  subjected  to  distillation  by  Duclaux's  method  in  a “ Jena  ” flask  : 
the  liquid  frothed  so  that  distillation  could  only  be  conducted  with  extreme 
slowness,  occupying  altogether  about  2 hours.  The  following  are  the 
results  : — 


1st.  10 

c.c.  distillate,  0*35  c.c.  Y/lOO  acid 

= 3-6% 

of  total  distillate. 

2ud. 

045 

= 4-7 

5 ? 5 j 

3rd. 

„ 0-55 

= 5-7 

5 J 5 5 

4th. 

„ 0-55 

= 5-7 

? ? ? ? 

5 th. 

,,  0*60 

= 6-2 

??  ? J 

6 th. 

„ 0-60 

= 6-2 

? ? ? J 

7th. 

. „ 1-05 

= 10-9 

8th. 

„ 1-70 

= 17-7 

’ > ? ? 

9th. 

55  L7o  ,, 

= 18-2 

55  53 

10th. 

55  2 -00 

=29-8 

5 5 5 3 

1 1th.  in 

flask  115  4 

Total  acidity  of  110  c.c.  = 129-8  ; total  acidity  of  distillate  = 9 -6  ; acidity 
of  residuum  = 115 -4  ; loss,  129 ‘8— 125-0  = 4*8  c.c.  (The  same  flask  evolved,  in 
the  blank  experiment,  alkali  equivalent  to  5*0  c.c.  of  Y/lOO  acid  in  2J  hours.) 

These  results  not  only  afford  no  evidence  of  the  presence  of  butyric 
acid,  but  are  even  lower  in  the  early  stages  than  those  of  pure  acetic  acid.  It 
seems  probable  that  with  the  very  slow  rate  of  distillation  absolutely  neces- 
sary, the  acid  in  the  earlier  stages  recondenses  in  the  upper  parts  of  the 
flask,  and  so  the  proportion  distilled  over  does  not  conform  to  Duclaux's 
table.  Another  110  c.c.  of  the  same  230  c.c.  of  liquid  was  evaporated  to 
dryness  in  a platinum  basin  over  a water  bath,  re-diluted  with  50  c.c.  of 
water,  and  again  evaporated  to  dryness  : the  residual  acidity  was  equi- 
valent to  113*5  Y/lOO  acid.  The  division  of  acid  in  this  liquid  into  fixed 
and  volatile  agrees  closely  in  both  tests.  Taking  that  in  the  platinum  basin 
as  being  the  more  correct,  we  have  out  of  129*8  of  total  acidity,  113*5  of 
fixed,  and  16*3  c.c.  of  volatile  acidity.  Reckoning  these  as  percentages 
on  the  whole  dough,  we  have  in  solution  0*74  of  fixed  acid  (lactic)  and  0*07 
per  cent,  of  volatile  (acetic)  acid.  In  strictness,  it  must  also  be  remembered 
that  any  carbon  dioxide  present  in  the  dough  is  also  estimated  as  acetic 
acid,  making  this  result  too  high  rather  than  too  low.  Bearing  in  mind 
Balland’s  investigations.  Chapter  XXVIII.,  in  which  he  shows  that  a con- 
siderable quantity  of  the  acid  of  flour  is  retained  by  the  solid  matter,  and 
not  given  up  to  a filtered  solution,  the  acidity  of  the  remaining  170  c.c.  of 
mixed  liquid  and  residual  flour  solids  was  also  determined.  This  was  found 
to  contain  acid  equivalent  to  275  c.c.  Y/lOO  acid.  As  dough  contains 
approximately  42  to  45  per  cent,  of  water,  the  50  grams  taken  will  contain 
about  50  — 22  = 28  grams  of  solid  matter.  Therefore  the  residual  170 
c.c.  will  consist  of  about 

170  — 28  =:  142  c.c.  of  liquid  and  28  grams  of  sohd  residue  : and  the 
total  400  C.C.,  of  372  c.c.  of  liquid  and  28  grams  of  solid.  But  as  the  residual 
170  c.c.  contains  142  c.c.  of  liquid,  the  acidity  of  which  is  1*18  per  c.c.  (by 
direct  determination),  then 

142  X 1*18  = 167*5  c.c.  acidity  due  to  the  liquid  portions. 

Its  total  acidity,  275—167*5  = 107*5  acidity  remaining  in  the  solid 
matter.  Calculating  this  as  lactic  acid, 

107*5  X 0*0009  X 2 =0*193  per  cent,  of  acid  remaining  in  solid  matter. 

The  372  c.c.  of  solution  must  contain,  as  by  estimations  on  110  c.c.,  the 
following  quantities  of  fixed  and  volatile  acid  : — 

1 13  5 X 0009  X 2 _ 0.^02  per  cent,  fixed  acid  reckoned  as  lactic. 

16  3 X 372  X 0 0006  x 2 _ 0.000  00nt.  volatile  acid  reckoned  as  acetic 

110  ^ 


BREAD-MAKING. 


441 


Summing  up  these  results  we  have — 
Dissolved  fixed  acid  (lactic) 

. . 0-792 

,,  volatile  (acetic) 

. . 0-066 

Undissolved  acid,  remaining  in  solids  . . 

. . 0-193 

Total  acidity  by  c irect  determination  . . 

1-051 
. . 0-981 

Difference 

..  0-070 

Bread. — In  common  with  the  dough,  the  bread  smelt  not  only  sour, 
hut  of  putrefactive  products.  The  first  estimation  made  was  of  mois- 
ture, of  which  there  was  40*4  per  cent.,  leaving  59*6  per  cent,  of  dry  bread 
solids.  The  percentages  of  acid  are  given  on  both  the  moist  and  dry  bread. 
The  total  acidity  was  determined  on  10  grams,  and  amounted  to  10*1  c.c. 
of  N/IO  acid  = 0*912  per  cent,  of  acid  reckoned  as  lactic  acid  on  the  moist 
bread.  It  may  be  of  interest  here  to  point  out  that  10  grams  of  dough  = 
10*9  c.c.  of  N/10  acid,  and  that  approximately  10*6  grams  of  dough  are 
required  to  make  10  grams  of  bread. 

10-6  grams  of  dough  have  an  acidity  = 11-55  c.c.  N/IO  acid. 

10-0  ,,  bread  ,,  = 10-10  ,, 

Acidity  lost  during  baking  = 1-45  ,, 

1-45  X 0-006  = 0-0087  grams  acetic  acid. 

By  this  estimation,  therefore,  the  bread  has  lost  of  acidity,  reckoned 
as  acetic,  0*08  per  cent.  As  the  bread  still  contains  volatile  acidity,  and 
this  amount  is  slightly  less  than  the  volatile  acidity  of  the  dough,  the  assump- 
tion is  that  a slight  amount  of  lactic  acid  has  been  volatilised  in  the  oven. 

An  aqueous  extract  of  the  bread  was  made  in  precisely  the  same  manner 
as  with  the  dough,  50  grams  being  taken  and  made  up  to  400  c.c.  with  the 
addition  of  1 c.c.  of  chloroform.  The  following  data  were  obtained  on  the 
elear  supernatant  liquid,  of  which  220  c.c.  were  removed  : — 

Total  acidity  of  10  c.c.  = 9*3  N/lOO  acid. 

110  c.c.  were  subjected  to  distillation  by  Duclaux’s  method,  and  boiled 
regularly  and  speedily.  The  following  are  the  results : — 


1st.  10  c.c.  distillate,  0-80  c.c.  N/lOO  acid  6-5%  of  total  distillate. 


2ad. 

0-85 

= 6-9 

5>  5> 

3rd. 

0-85 

? ? 

= 6-9 

5 5 

4th. 

0-95 

?? 

= 7-7 

5 5 5 5 

5th.  ,, 

1-10 

?? 

= 9-0 

5 5 55  ' 

6th.  ,, 

1-10 

?? 

= 9-0 

5 5 55 

7th. 

1-25 

5) 

= 10-2 

5 5 5 5 

8th. 

1-45 

?? 

= 11-7 

5 5 5 5 

9 th. 

1-65 

? ? 

= 13-5 

5 5 5 5 

10th. 

2-20 

?? 

= 17-2 

5 5 5 5 

11th.  in  flask 

Total  acidity  of 

90-7 

110  c.c.  = 

102*3  ; 

total  acidity 

of  distillate  = 12*2  ; 

acidity  of  residuum  = 90*7  ; gain,  102-9  — 102*3  = 0*6  c.c.  of  N/lOO  acid. 

These  results  are  not  very  far  apart  from  acetic  acid,  but  are  slightly 
on  the  formic  rather  than  the  butyric  acid  side. 

100  c.c.  were  evaporated  in  a platinum  basin,  and  gave  79*0  c.c.  A'/lOO 
acidity,  equal  to  86*9  on  110  c.c.  102*3  — 86*9  = 15*4  c.c.  of  volatile 
acid.  Working  these  out  as  percentages  of  lactic  and  acetic  acids,  we  have 
0*626  of  lactic  and  0*075  of  acetic  acid  on  the  whole  bread. 


442 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  residual  liquid  together  with  bread  solids  was  next  examined  : 
the  total  volume  was  400  — 220  = 180  c.c.  As  50  grams  of  bread  were 
taken,  the  bread  solids  were  30  grams.  Therefore  the  residual  180  c.c. 
consisted  of 

180  — 30  = 150  c.c.  of  liquid  and  30  grams  of  solids,  and  the  total  400' 
consisted  of  370  c.c.  of  liquid  and  30  grams  of  solid. 

The  total  acidity  of  the  residual  liquid  and  solids  together  is  306-0  c.c. 
Y/lOO  acid.  But  as  this  contained  150  c.c.  of  liquid,  the  acidity  of  which 
is  0*93  per  c.c.,  then 

150  X 0-93  = 139-5  c.c.  acidity  due  to  the  liquid  portion. 

The  total  acidity,  306-0  — 139-5  = 166-5  acidity  remaining  in  the  solid 
matter.  Calculating  this  as  lactic  acid, 

166-5  X 0-0009  X 2 = 0-299  per  cent,  of  acid  remaining  in  solid  matter. 

The  370  c.c.  of  solution  must  contain,  as  by  estimation  on  110  c.c.,  the 
following  quantities  of  fixed  and  volatile  acid : — 


86-9  X 370  X 0-0009  x 2 

no  r~ 

15-4  X 370  X 0-0006  x 2 

no 


— 0-526  per  cent,  fixed  acid  reckoned  as  lactic. 

= 0-062  per  cent,  volatile  acid  reckoned  as  acetic. 


Summing  up  these  results,  we  have — 

Dissolved  fixed  acid  (lactic)  . . . . . . 0-526  per  cent. 

,,  volatile  acid  (acetic)  . . . . . . 0-062  ,, 

Undissolved  acid  remaining  in  solids  . . . . 0-299  ,, 


0-887 

Total  acidity  by  direct  determination . . ..  0-912 

Difference  . . . . . . . . . . 0-025 

Distillation  in  Vacuo. — In  the  next  place,  500  grams  of  the  bread  were 
taken  and  distilled  in  vacuo  by  the  method  described  in  Chapter  XXVIII.  ; 
the  bread  being  raised  to  a temperature  of  120-125°  C.  The  amount  of 
distillate  was  220  c.c.,  of  which  10  c.c.  were  taken  for  determination  of  total 
acidity,  and  were  found  to  possess  acidity  equal  to  11*4  c.c.  Y/lOO  acid. 
Ten  grams  of  the  residual  dry  bread  had  an  acidity  equal  to  16-0  Y/IO  acid. 
Calculated  as  percentages  on  the  whole  bread,  these  are  equivalent  to  0-30 
per  cent,  of  volatile  (acetic)  acid,  and  0*864  per  cent,  of  fixed  (lactic)  acid. 

Of  the  distillate,  100  c.c.  were  evaporated  to  dryness  in  a platinum  basin 
and  taken  up  with  distilled  water  ; the  addition  of  one  drop  of  Y/lOO  soda 
gave  an  alkaline  reaction  with  phenolphthalein,  showing  that  the  distillate 
was  to  this  extent  free  from  fixed  acid.  The  remaining  110  c.c.  were 
distilled  by  Duclaux’s  method  in  a “ Jena  flask,  with  the  following 
results  : — 


1st. 

10  c.c  distillate  . . 

X/lOO  acid  = 

5-80  c.c. 

A. 

Per  cent,  of  = 
total  distillate. 

6-4 

B. 

Per  cent, 
total  acid  in  1 

4*6 

2nd. 

? 5 

6-60  „ 

7-3 

5-3 

3rd. 

? 9 

7-70  „ 

8-5 

6-2 

4th. 

99 

8-30  „ 

9-2 

6-6 

5 th. 

9 9 

8-40  „ 

9-3 

6-7 

6 th. 

8-80  „ 

9-8 

7-1 

7th. 

9 9 

9-65  „ 

10-7 

7-7 

8th. 

9 9 

9-80  „ 

10-9 

7-9 

9th. 

9 9 

11-35  „ 

12-6 

9-1 

10th. 

9 9 

13-50  „ 

15-0 

11-0 

11th. 

in  flask 

34-35  „ 

— 

27-9 

BREAD-MAKING. 


443 


Total  acidity  of  110  c.c.  = 125*4;  total  acidity  of  distillate  = 89*9; 
acidity  of  residual  10  c.c.  = 34*35  ; loss,  125*4  — 124*25  = 1*15  c.c.  of 
iV/lOO  acid. 

On  referring  to  the  table  of  distillation  of  mixtures  of  acetic  and  butyric 
acids,  Chapter  XXVIII.,  and  comparing  column  A with  that  for  a mixture 
of  20  parts  acetic  to  1 part  of  but5rric  acid,  the  figures  closely  agree,  being 
distinctly  on  the  butyric  acid  side  of  pure  acetic  acid.  It  may  be  con- 
sidered proved  that  a trace  of  butyric  acid  is  present,  equal  to  approximately 
of  the  amount  of  acetic  acid.i  Calculating  into  percentages,  we  have 
of  the  total  acidity, 


125-4  x20 


= 119-4  c.c  A/lOO  acid  due  to  acetic  acid  ; 
6-0  c.c.  ,,  butyric  acid. 


21 
125-4 

Then  as  110  c.c.  of  distillate  were  obtained  from  250  grams  of  bread, 

119-4  X 0-0006  X 2 a aoo  4.  f ^ 1 • 1,11,  i 

— = 0-028  per  cent,  of  butjrric  acid  m whole  bread, 

5 

and  ^ ^ ^ 0-00088  x 2 ^ 0-002  per  cent,  of  butyric  acid  in  whole  bread. 
5 

Summing  up,  we  have  the  following  as  the  general  results  of  the  different 
analyses,  expressed  in  percentages,  those  on  bread  being  calculated  on 
both  the  whole  bread  and  dry  residue  : — 


Bread. 


Dough. 

Whole. 

Dried. 

Total  acidity  by  direct  determination 

0-981 

0-912 

1-521 

Dissolved  fixed  acid  (lactic) 

0-792 

0-526 

0-876 

,,  volatile  acid  (acetic) 

0-066 

0-C68 

0-103 

Undissolved  acid,  remaining  in  solids. . 
Distillation  in  Vacuo — 

0-193 

0-299 

0-498 

Fixed  acid  (lactic)  . . 

0-864 

1-440 

Volatile  acid  (acetic) 

Fractional  Redistillation  of  Vacuum  Distillate, — 

0-030 

0-050 

Acetic  acid  . . 

0-028 

0-047 

Butyric  acid 

0-002 

0-003 

Comparing  the  results  of  the  two  different  methods  of  analysis  employed, 
we  find  that  with  aqueous  distillation  about  yh  of  the  total  acid  in  both 
dough  and  bread  was  found  to  be  volatile.  Employing  the  dry  distillation 
method  on  bread,  yy  of  the  total  acid  was  volatile  at  120°  C.  in  vacuo.  As 
to  the  relative  accuracy  of  the  two  processes,  the  former  presents  the  initial 
difficulty  that  the  whole  of  the  acid  is  not  obtained  in  the  aqueous  extract  ; 
and,  further,  that  a portion  at  least  of  the  lactic  acid  distils  over  with  the 
steam.  It  may,  on  the  other  hand,  be  objected  that  the  whole  of  the  acetic 
acid  is  not  volatilised  by  the  treatment  in  vacuo.  Weigert,  however,  has 
shown  that  by  distilling  wines  in  a vacuum,  the  whole  of  the  acetic  'acid 
can  be  obtained  {Zeitsch,  filr  Analyt.  Chemie.,  1879,  207).  A number  of 
other  comparative  determinations  were  made,  but  in  all  cases  the  aqueous 
extract  method  gave  considerably  higher  volatile  acids  than  distillation 
in  vacuo. 


^ Duclaux  points  out  that  with  the  use  of  a larger  distilling  flask  a higher  proportion 
of  acid  remains  in  the  residual  10  c.c.,  that  is,  that  with  a greater  proportion  of  return 
condensation,  more  acid  escapes  distillation.  As  slow  distillation  also  means  more 
return  condensation,  the  same  result  follows.  The  use  of  charged  trap-bulbs,  E,  F, 
Fig.  116,  with  the  distilling  apparatus,  necessitated  slow  working  ; hence  the  general 
error  of  experiment  is  in  the  direction  of  lessening  the  apparent  quantity  of  butyric  acid. 


444 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  following  experiments  were  conducted  with  the  view  of  studying 
the  progress  of  sourness  with  the  prolongation  of  fermentation  : — 

A.  Series. — Quantities  taken — 15  lbs.  spring  American  1st  patent  flour, 
9 lbs.  water  at  40°  C.  (104°  F.),  4 oz.  compressed  distillers’  yeast,  and  2 oz. 
salt. 

A ferment  was  first  set  with  all  the  water  and  a portion  of  the  flour  : 
in  40  minutes  the  dough  was  made,  and  had  a temperature  of  27°  C.  (80°  F.). 
It  was  maintained  at  this  temperature  for  20  hours,  and  then  allowed  to 
stand  at  the  temperature  of  the  room  for  another  24  hours.  At  intervals, 
as  given  in  the  following  table,  the  dough  was  “ knocked  down,”  re-kneaded, 
and  a portion  of  2 lbs.  3 oz.  taken  and  baked  into  a loaf. 

B.  Series. — Quantities  taken — 12  lbs.  spring  American  bakers’  grade 
and  3 lbs.  low  grade  (red  dog)  flour,  other  ingredients  as  in  A.  Treatment 
precisely  as  in  A. 

The  following  are  the  times  at  which  loaves  from  both  series  were  baked  : — 
No.  1.  Put  in  oven  3J  hours  after  setting  ferment. 

„ 2.  „ 6 

„ 3.  „ 9 

„ 4.  „ 12 

,,  5.  „ 15 

,,  6.  ,,  20 

„ 7.  „ 44  _ 

The  following  were  the-  characteristics  of  the  respective  loaves  : — 

A.  Series. 

No.  1.  Sweet  in  smell  and  taste. 

,,  2.  If  anything,  slightly  darker  in  colour  ; slightly  maAvkish  smell 
and  taste,  not  sour  or  yeasty,  crust  paler. 

,,  3.  Colour  darker,  mawkish  flavour  disappeared,  incipient  sour  smell, 
but  no  sour  taste. 

,,  4.  Colour  darker,  loaf  heavy  and  close,  somewhat  yeasty  smell,  but 
no  decided  sour  flavour. 

,,  5.  Small  and  close,  colour  about  same  as  4,  sour  smell ; taste,  acid  and 
disagreeable. 

” I Sour  and  putrescent. 

B.  Series. 

No.  1.  Characteristic  odour  of  bread  from  low  grade  flours,  but  perfectly 
sweet  in  taste  and  smell . 

,,  2.  Colour  very  dark,  sour  smell,  taste  slightly  sour. 

,,  3.  Colour  changed  from  yellowish  to  dark  reddish  brovn.  Less  sour 
smell  than  2.  Unpleasant  taste,  rather  of  decomposition  than 
acidity. 

,,  4.  Reddish  brown  colour  much  intensified.  Slightly  sour  smell. 

Taste  similar  to  3,  but  more  marked. 

,,  5.  Colour  as  4.  Smell  and  taste  intensified. 

,,  6.  Sour  and  putrescent 

,,  7.  Sour  and  putrid. 

None  of  these  had  the  characteristic  sour  smell  of  hakers*  sour  bread^ 

The  following  are  the  results  of  determinations  of  acidity,  the  total  being 
determined  on  the  whole  bread  ; the  volatile  by  distillation  in  vacuo  ; 
and  the  fixed  or  non-volatile,  in  the  dried  residue  from  this  distillation.^ 

1 The  whole  of  these  distillates  were  subjected  to  fractional  distillation  by  Duclaux’s 
method.  Owing,  however,  to  subsequently  finding  that  the  flasks  used  gave  a strong 
alkaline  reaction,  the  authors  do  not  feel  justified  in  quoting  the  results  as  trustworthy, 
and  therefore  have  not  inserted  them.  The  same  remark  applies  to  a large  number 
of  other  Duclaux  estimations. 


BREAD-MAKING. 


445 


As  the  moisture  in  the  different  samples  varied,  the  results  are  throughout 
calculated  on  the  dry  solids.  These  can  be  approximately  converted  into 
tliose  on  the  whole  bread  by  multiplying  by  0*6. 

Percentages  of  Acidity  in  Sour  Bread. 


No. 

A.  Series. 

B.  Series. 

Total. 

Volatile. 

Fixed,  i 

Ratio  of 
Volatile  to 
Total. 

Total. 

Volatile. 

Fixed,  i 

Ratio  of 
Volatile  to 
Total. 

1 

0-477 

0-003 

1 

1 ()  O' 

1-140 

1-125 

2 

0-407 

0-015 

0-4C5 

1 

2 7 

1-041 

0-042 

0-972 

1 

2 o 

3 

0-491 

0-030 

0-441 

1 

T(T 

1-3C0 

0-102 

1-143 

12 

4 

0-671 

0-090 

0-549 

_] 

1-647 

0-252 

1-269 

1 

5 

1 1-108 

0-123 

0-720 

i 

2-289 

0-123 

1-314 

1 

1 7 

6 

1-110 

0-087 

0-747 

i 

2-6C0 

0-113 

1-746 

1 

2 3 

7 

1-457 

0-059 

0-9C0 

1 

2 4 

2-823 

0-131 

1-980 

I 

2 1 

Curiously  in  both  series  the  total  acidity  is  less  in  the  second  than  in 
the  first  loaf  : with  this  exception  the  total  acidity  steadily  rises  throughout 
the  two  series.  The  volatile  acidity  (reckoned  as  acetic)  attains  its  maxi- 
mum in  Series  A.  in  12  hours,  and  in  series  B.  in  15  hours,  after  which  it 
diminishes.  The  ratio  of  volatile  to  total  acidity  is  in  both  cases  highest 
with  the  No.  4 loaf.  Apparently  after  that  time  the  production  of  volatileacid 
does  not  keep  pace  with  its  evaporation  from  the  dough.  (It  should  also  be 
mentioned  that,  as  the  loaves  were  analysed  in  the  order  made,  the  latter 
ones  had  become  somewhat  drier  when  subjected  to  analysis.)  In  conse- 
quence of  the  dark  colour  of  the  dried  bread,  the  determination  of  fixed  acid 
was  difficult  owing  to  uncertainty  as  to  the  exact  point  of  neutrality  as  shown 
by  the  indicator.  In  these  breads  No.  2’s  are  worked  more  than  the  baker 
would  work  them  in  actual  practice  ; while  No.  3 of  each  series  is  far  sourer 
than  even  a 'baker’s  very  sour  loaf.  The  others,  of  course,  represent  extreme 
results  altogether  outside  those  of  actual  practice.  Note  that  in  No.  3 A. 
the  volatile  acidity  is  only  yV  of  the  total,  and  in  No.  3 B.  yV  of  total 
acidity. 

In  the  next  place  are  given  the  results  of  an  experiment  with  a potato 
ferment,  purposely  allowed  to  proceed  to  extreme  sourness.  A potato  fer- 
ment was  made  from  30  grams  of  potato,  ICO  grams  of  water  in  which  the 
potato  was  boiled,  5 grams  raw  flour,  and  10  gTams  of  yeast.  This  was  fer- 
mented at  95°  E.,  and  maintained  at  that  temperature  over  night  in  an 
uncovered  shallow  basin.  The  next  morning  the  ferment  was  made  up  to 
300  C.C.,  with  water  at  120°  F.,  and  sufficient  flour  added  to  make  a slack 

sponge,  which  had  a temperature  of  95°  F.  The  total  acid  reckoned  as 

lactic  was  determined  in  10  grams  of  the  whole  sponge,  and  the  volatile 
and  fixed  acids  in  the  filtered  chloroformed  aqueous  extract  in  the  manner 
previously  described.  The  following  were  the  results  : — 

Total  acidity  as  lactic  acid  ..  ..  1*197  per  cent. 

Dissolved  fixed  acid  (lactic)  . . . . 0*248  ,, 

,,  volatile  acid  (acetic)  . . . . 0*053  ,, 

Ratio  of  volatile  to  total  acid  . . . . 

The  sponge  was  allowed  to  work  for  6 hours  and  then  doughed  up 
with  more  flour,  allowed  to  work  I J hours  and  baked.  The  following  are 


446 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  results  of  determinations  on  the  bread.  The  total  acidity  was  deter- 
mined on  the  whole  bread,  and  volatile  and  fixed  acids  by  distillation  in 
vacuo. 


Total  acidity  as  lactic  acid 

Whole  Bread. 

1-158 

Dried. 

1-935 

Fixed  acid  by  distillation  in  vacuo 

(lactic) 

1-015 

1-692 

Volatile  ,,  ,, 

(acetic) 

0-038 

0-064 

Ratio  of  volatile  to  total  acid 

1 

3 0 

1 

30 

The  principal  feature  is  that  again  neither  in  sponge  nor  in  dough  is  there 
more  than  a very  small  proportion  of  volatile  acid. 

Following  on  these  were  some  experiments  made  on  bakers’  breads. 
One  firm  in  the  south  of  England,  and  another  in  Glasgow,  were  kind  enough 
to  reserve  a loaf  of  one  batch  baked  in  the  usual  manner  (No.  1),  and  also 
to  set  aside  dough  for  two  other  loaves,  one  of  which  (No.  2)  was  baked  in 
each  case  when  at  the  utmost  limit  of  sourness  ever  found  in  practice,  and 
the  other  (No.  3)  several  hours  after.  The  following  are  the  results  of 
analysis  made  as  before  by  vacuum  distillations,  and  in  filtered,  chloro- 
formed, acqueous  extract : — 


English. 


Scotch. 


Whole 

Bread. 

Dried. 

Whole 

Bread. 

Dried. 

No.  1.  Total  acidity  as  lactic  acid 

0-362 

0-604 

0-258 

0-431 

Fixed  acid  by  distillation  in 
vacuo  (lactic) . . 

Volatile  acid  by  distillation  in 

0-351 

0-585 

0-243 

0-406 

vacuo  (acetic) 

0-0006 

0-001 

0-005 

0-008 

Ratio  of  volatile  to  total  acid 
Dissolved  fixed  acid  (lactic)  by 

— 

1 

6 04 

• — ■ 

aqueous  distillation 

0-184 

0-307 

— ■ 

— 

Dissolved  volatile  acid  (acetic) 

0-009 

0-016 

— 

— 

Ratio  of  volatile  to  total  acid . . 

1 

19 

1 

1 9 

— 

— 

No.  2.  Total  acidity  of  lactic  acid 

0-535 

0-891 

0-342 

0-570 

Fixed  acid  by  distillation  in 

vacuo  (lactic) 

0-491 

0-819 

0-324 

0-540 

Volatile  acid  by  distillation  in 

vacuo  (acetic) 

0-025 

0-042 

0-008 

0-013 

Ratio  of  volatile  to  total  acid  . . 

1 

91' 

1 

2\ 

1 

4 4 

1 

44 

No.  3.  Total  acidity  as  lactic  acid 

0-759 

1-265 

0-342 

0-570 

Fixed  acid  by  distillation  in 
vacuo  (lactic) 

Volatile  acid  by  distillation  in 

0-696 

1-161 

0-318 

0-531 

vacuo  (acetic) 

0-036 

0-060 

0-017 

0-028 

Ratio  of  volatile  to  total  acid 

1 

2 1 

1 

2 0 

1 

2 0 

Throughout  this  series  also  the  proportion  of  volatile  acid  is  very  low. 

Excluding  those  examples  in  which  acidity  was  pushed  far  beyond 
any  instance  ever  occurring  in  practice,  the  volatile  acids  found  by  distilla- 
tion amounted  to  from  to  jjV  the  total  acid  of  the  dough.  In  the  instance 
quoted  of  a loaf  in  the  last  stage  of  sourness,  an  amount  of  butyric  acid  was 
found  approximately  equal  to  about  vV  the  total  volatile  acid.  The  acidity 
of  bread  may  be  divided  among  the  following  acids  in  approximately  the 
following  proportions  : — 

Lactic  acid  . . . . . . . . about  95  per  cent. 

Acetie  ,,  . . . . . . . . ,,  5 ,, 

Butyric  ,,  . . . . from  0*0  to  about  0*5  ,, 


BREAD-MAKING. 


447 


The  question  has  been  already  raised  as  to  how  far  the  bakers*  sourness 
is  dependent  on  the  chemists*  acidity  of  bread  : this  problem  merits  further 
examination.  The  particulars  of  the  progressive  series  of  tests  given  on 
page  444  should  be  studied  in  this  connection.  Taking  first  the  A.  series 
on  patent  flour,  No.  4 loaf  had  no  decided  sour  flavour,  while  No.  5 tasted 
acid.  No.  4 had  a total  acidity  of  0*671,  while  that  of  No.  5 was  1*108  per 
cent.,  so  that  a marked  increase  flad  occurred.  Comparing  the  B.  series, 
No.  2 was  slightly  sour  with  an  acidity  of  1 *041,  although  No.  1 with  a slightly 
higher  acidity  was  sweet  to  the  taste.  It  must  be  remembered  that  in  the 
B.  series  the  naturally  strong  coarse  flavour  of  the  flour  used  made  it  difficult 
to  detect  shades  of  acidity  with  the  palate.  Dealing  with  the  smell.  No.  3 A. 
Avas  found  to  have  incipient  sour  smell,  with  volatile  acidity  of  0*030  : turn- 
ing to  the  B.  series.  No.  2 has  a sour  smell  with  a volatile  acidity  of  0*042. 
On  studying  the  higher  number  of  each  series  there  is  a steady  increase  of 
total  acid,  but  in  both  A.  and  B.  the  volatile  acid  is  lower  in  these  higher 
numbers.  So  that  7 A.,  with  an  exceedingly  sour  smell,  has  less  volatile 
acid  than  No.  4,  which  it  far  transcends  in  odour.  The  same  applies  to  the 
B.  series  where  No.  6 contains  practically  the  same  amount  of  volatile  acid 
as  does  No.  3,  although  No.  3 smells  less  sour  than  2,  while  No.  6 smelt  sour 
and  putrescent.  Speaking  in  a general  way,  sourness  and  acidity  go  together, 
and  bread  with  a total  acidity  of  about  0*5  per  cent,  and  a volatile  acidity 
of  about  0*025  begins,  especially  in  the  highest  class  breads,  to  both  taste 
and  smell  sour.  But  lower  grade  breads  can  carry  a much  higher  propor- 
tion of  total  acidity,  and  have  its  taste  masked  with  the  natural  strong  flavour 
of  the  flour.  But  although  sourness  and  acidity  are  closely  associated, 
yet  the  bakers’  sourness  comprehends  more  than  is  expressed  by  acidity,  as 
is  shown  by  the  increasing  “ sourness  ” to  the  nose  of  Nos.  5,  6,  and  7 of 
both  series,  and  the  simultaneously  decreasing  volatile  acidity.  As  indi- 
eated  in  the  description  of  the  various  breads,  bakers’  sourness  also  includes 
and  takes  cognisance  of  incipient  putrefactive  changes.  If  this  be  the  case, 
sourness  ” should  be  accompanied  by  evidence  of  other  chemical  changes  : 
as  proteins  break  down  in  putrefaction  into  compound  and  simple  ammonias, 
the  following  determinations  were  made  on  bread.  Five  grams  of  the  bread 
were  taken,  broken  down  in  water,  and  large  excess  of  caustic  soda  added  : 
the  mixture  was  then  distilled  in  a current  of  steam  and  the  distillate  col- 
lected in  50  c.c.  of  A/10  acid.  Determinations  were  made  on  the  three 
samples  of  English  bread,  particulars  of  which  are  given  on  page  446.  The 
following  are  the  percentages  of  ammonia  (reckoned  as  NH3),  calculated  on 
the  AAhole  bread  : — 

English  Bread,  No.  1 . . . . . . . . 0*39  per  cent. 

„ „ No.  2 0*40 

„ „ No.  3 0*42 

The  amount  of  increase  is  not  very  great,  but  as  a similar  increase  of 
ammonia  has  been  noted  in  other  breads  tested,  evidence  is  afforded  that 
bakers’  sourness  is  accompanied  by  other  changes  in  the  constituents  of  the  bread 
in  addition  to  the  development  of  acidity. 

This  question  of  sourness  is  of  vast  importance  to  the  baker,  and  is  also 
the  baking  problem  on  which  chemistry  has  the  most  direct  bearing  ; it 
therefore  merits  most  careful  attention  in  all  its  details.  Among  Briant’s 
observations  is  that  lactic  and  acetic  ferments  flourish  best  at  a high  tem- 
perature, and  therefore  that  “ high  temperatures  for  panary  fermentation 
are  in  all  cases  undesirable.”  The  assumption  that  high  temperatures  are 
more  usually  accompanied  by  the  production  of  sour  bread  than  lower 
ones  is  so  directly  the  opposite  of  many  bakers’  practical  experience  that 
it  requires  most  careful  examination.  Among  breads  which  are  normally 


448 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


worked  at  a high  temperature,  the  following  are  well-kno^vn  examples  : — 
Nevilhs  bread,  made  in  London  from  straight  grades  of  comparatively  weak 
flour  ; and  Hovis  bread,  made  from  a meal  containing  25  per  cent,  of  germ. 
The  temperature  of  the  dough  for  the  latter  is  about  90°-95°  F.,  and  yet 
these  two  varieties  of  bread  are  remarkably  free  from  sourness.  In  preced- 
ing paragraphs  a summary  of  the  course  of  fermentation  has  been  given, 
while  high  temperatures  have  been  mentioned  as  accelerating  the  whole  of 
that  course  ; consequently,  at  a high  temperature,  everything  else  being 
equal,  the  sour  stage  is  reached  in  less  time  from  the  commencement  of 
setting  a ferment,  sponge,  or  dough,  than  if  a lower  temperature  be  adopted. 
But  if  fermentation  be  arrested  at  the  same  stage  of  its  progress,  there  is  no 
more  danger  of  bread  worked  warm  becoming  sour  than  that  which  is 
worked  cold.  The  crucial  point  as  to  temperature  is  whether,  for  the  same 
amount  of  carbon  dioxide  gas  evolved  during  alcoholic  fermentation,  more 
acid  is  produced  at  a high  temperature  than  a low  one.  In  order  to  eluci- 
date this  point  the  following  experiments  were  made  : — Mixtures  were  pre- 
pared of  50  grams  flour,  200  c.c.  water,  and  2*5  grams  distillers’  yeast,  and 
10  grams  brewers’  yeast  respectively.  These  were  placed  in  the  yeast- 
testing apparatus.  Fig.  21,  and  fermented  at  the  respective  temperatures 
of  75°  and  95°  F.,  which  m each  case  were  maintained  constant  until  350 
c.c.  of  gas  had  been  evolved.  The  original  acidity  of  the  mixtures  was  deter- 
mined in  duplicates  made  up  for  the  purpose.  As  soon  as  the  350  c.c.  of  gas 
had  been  obtained,  2 c.c.  of  chloroform  were  added  to  the  contents  of  the 
bottle,  which  was  shaken  up  and  allowed  to  stand  until  all  were  ready  for 
titration,  when  the  acidity  was  once  more  determined.  Two  complete 
series  of  estimations  were  made  on  successive  days.  In  another  similar 
experiment  with  distillers’  yeast  the  fermenting  mixture  was  first  main- 
tained at  95°  F.  until  175  c.c.  of  gas  had  been  evolved  : it  was  then  cooled 
to  75°  F.,  and  kept  at  that  temperature  until  90  c.c.  more  had  come  over. 
The  temperature  was  then  again  raised,  and  maintained  at  95°  until  the 
vhole  350  c.c.  of  gas  had  been  evolved.  The  following  table  gives  the  time 
required  for  the  evolution  of  350  c.c.  of  gas,  the  original  acidity,  the  final 
acidity,  and  the  amount  produced  during  fermentation,  reckoned  in  each 


case  as  lactic  acid 

Time 

taken. 

Hours. 

Original 

Acidity. 

Final 

Acidity. 

Produced 

during 

Fermentation. 

Distillers’  yeast  at 

75°  F 

104 

0175 

0-394 

0-219 

95°  F 

31 

0175 

0-290 

0.115 

Brewers’  ,, 

75°  F 

11 

0-228 

0-424 

0-196 

? ? ? 5 

95°  F 

6 

0-228 

0-442 

0-214 

Repeats  — 
Distillers’  yeast  at 

75°  F 

lU 

0-315 

0-540 

0-225 

95°  F 

4i 

0-315 

0-495 

0-180 

Brewers’  ,, 

75°  F 

11 

0-157 

0-679 

0-522 

5 5*  95 

95°  F 

5i 

0-157 

0-670 

0-513 

Distillers’  veast,  partly  at  75°  F.  and 

partly  at  95°  F. 

7i 

0-315 

0-495 

0-180 

With  the  distillers’  yeast,  in  both  instances  there  is  for  the  same  amount 
of  alcoholic  fermentation  a greater  development  of  acidity  at  the  lower 
temperature  ; while  with  the  brewers’  yeast  there  is  in  the  one  case  slightly 
more  acid  at  75°  F.,  and  in  the  other  a slightly  greater  quantity  at  the  higher 
temperature.  In  passing,  attention  is  directed  to  the  much  higher  acid- 
producing  power  of  the  brewers’  yeast  on  the  second  day  (with  a different 
sample)  than  the  first.  Both  the  practical  experience  of  the  bakery  and 
tliese  tests  go  to  show  that  for  the  same  amount  of  alcoholic  fermentation  a 


BREAD-MAKING. 


449 


comparatively  high  temperature  is  at  least  not  more  productive  of  acidity  than  a 
much  lower  one.  Further  confirmation  of  this  is  afforded  by  the  advent  of 
short  systems  of  fermentation  in  which  the  dough  is  worked  at  high  tem- 
peratures, and  with  great  freedom  from  sourness.  The  last  experiment 
was  made  with  the  object  of  determining  whether  a sudden  lowering  of 
temperature  during  fermentation  had  a tendency  to  increase  acidity.  The 
results  show  that  no  such  increase  was  caused  in  this  instance. 

Slackness  of  dough  is  only  a cause  of  acidity  in  the  same  sense  as  high 
temperature,  in  that  it  accelerates  the  whole  course  of  fermentation.  Among 
breads  made  from  very  slack  doughs  are  Manchester  tin  bread  and  Vienna 
bread,  but  neither  of  these  are  specially  liable  to  sourness. 

Holding  the  view  that  much  of  the  acidity  of  bread  is  due  to  acetic  acid, 
and  that  the  production  of  this  acid  is  stimulated  by  the  presence  of  oxygen, 
Briant  advises  that  “ therefore  fermenting  dough  should  be  kept  as  much 
out  of  contact  with  air  as  is  possible.’"  If  the  quantity  of  acetic  acid  present 
in  doughs  which  are  most  intensely  sour  in  character  is  but  trifling,  then  this 
reason  for  exclusion  of  air  no  longer  exists.  To  refer  again  to  Vienna  bread, 
the  ferments  and  dough  for  this  are  beaten  and  exposed  to  air  almost  as 
much  as  an  egg  in  the  act  of  whisking,  and  these  are  rarely,  if  ever,  sour. 
If  a baker  finds  a sponge  working  too  rapidly,  and  in  such  a condition  as  his 
experience  tells  him  means  that  fermentation  is  likely  to  have  overshot  the 
mark  by  the  time  he  wishes  to  take  it,  then,  in  order  to  lessen  risk  of  sourness, 
he  very  commonly  throws  off  the  trough  lid  and  freely  exposes  it  to  air. 
He  finds  practically  that  this  treatment,  instead  of  causing  sourness  by 
oxidation  of  alcohol,  obviates  it  by  lowering  the  temperature,  and  so  retard- 
ing the  whole  course  of  fermentation. 

The  following  may  be  taken  as  a summary  of  the  authors’  viev  s on  sour 
bread.  (It  will  be  noticed  that  it  endorses  several  of  Bri ant’s  conclusions) : — 

1.  “ Sour  bread,”  as  understood  by  the  baker,  is  the  result  of  a combination  of 
bacterial  fermentations.  Principal  among  these  is  that  producing  lactic  acid,  which 
constitutes  about  95  per  cent,  of  the  total  acidity.  The  remainder  is  due  to  acetic 
acid,  with,  in  very  bad  cases,  traces  of  butyric  acid.  In  addition  to  the  development 
of  acidity,  sour,  as  distinct  from  acid  bread,  shows  signs  of  putrefactive  decomposition. 

2.  The  acid  and  putrefactive  fermentations  are  produced  by  bacteria  to  be  found 
in  the  dough. 

3.  These  bacteria  may  be  introduced  by  the  yeast,  by  the  use  of  dirty  vessels,  and 
by  the  flour  ; but  their  presence  in  the  flour  is  the  most  general  cause  of  “ sourness,” 
and  the  lower  the  grade  of  the  flour,  the  greater  is  the  risk  of  sour  bread. 

4.  The  activity  of  these  bacteria  is  dependent  on  that  of  the  yeast : while  the 
latter  is  active,  the  bacteria  are  comparatively  quiescent.  With  the  exhaustion  of 
the  yeast,  or  cessation  of  active  fermentation  through  the  assimilation  of  all  ferment- 
able material,  a stage  is  attained  in  bread  fermentation  when  bacteria  are  excessively 
active,  and  sourness  rapidly  develops. 

5.  Temperature  and  slackness  of  dough  have  but  little  effect  on  sourness,  except 
in  that  indirectly  they  affect  the  speed  of  the  whole  course  of  fermentation,  and  so 
hasten  or  retard  the  arrival  of  the  bacterial  fermentation  stage.  This  stage  being 
reached,  the  production  of  sourness  is  accelerated  both  by  high  temperature  and 
slackness  of  dough. 

6.  Exposure  to  air  has  no  appreciable  effect  on  sourness,  and  may  even  through 
its  cooling  action  be  beneflcial. 

7.  The  two  principal  causes  of  sourness  are — Allowing  , the  fermentation  to 

proceed  beyond  the  normal  into  the  souring  stage  ; and  the  use  of  materials  or  vessels 
containing  abnornially  high  proportions  of  bacteria,  especially  when  employed  with 
weak  and  inactive  yeasts.  i ...  - 

585.  Effect  of  Baking  on  Bacterial  Life. — Differences  of  opinion  exist 

G G 


450 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


as  to  whether  the  act  of  baking  destroys  the  life  of  all  organisms  that  may 
be  present  in  the  dough.  Unless  the  baking  is  most  inefficiently  conducted 
the  temperature  within  the  loaf  should  be  sufficiently  high  to  kill  the  yeast. 
The  doubt  is  whether  or  not  the  germs  or  spores  of  other  organisms  are  also 
destroyed — thus,  the  spores  of  some  of  the  bacilli  can  withstand  a quarter 
of  an  hour’s  boiling,  while  a sensible  proportion  outlive  an  hour’s  subjection 
to  a boiling  heat.  These  experiments  afford  grounds  for  supposing  that 
such  germs  might  continue  to  exist  even  during  an  hour’s  baking.  The 
observed  facts  of  the  souring  of  bread  also  point  in  the  same  direction.  Two 
loaves  may  be  taken,  each  of  which  is  sweet  when  removed  from  the  oven, 
and  kept  under  precisely  the  same  conditions  ; the  one  after  a few  hours 
becomes  sour,  the  other  retains  its  sweetness.  Here  there  is  a difference 
in  behaviour  which  is  not  due  to  external  conditions,  but  to  some  inherent 
quality  of  the  two  loaves.  The  undestroyed  germs  of  acid  fermentation 
have,  in  the  bread  in  which  they  are  present,  induced  sourness.  The  only 
other  explanation  of  souring  is  that  the  germs  of  the  specific  bacilli  have 
found  their  way  from  the  atmosphere  into  the  baked  loaf. 

Walsh  and  Waldo  subjected  this  matter  to  exhaustive  investigation. 
Using  the  accustomed  precautions  in  bacteriological  work,  they  procured 
a number  of  loaves  of  bread,  and  sowed  portions  of  the  interior  crumb  in 
sterilised  gelatin  and  glucose  mixture,  and  made  plate  cultivations.  A 
few  of  the  loaves  were  found  to  be  practically  sterile,  while  others  contained 
a large  number  of  organisms,  including  bacillus  subtilis  and  other  bacilli, 
also  sarciua  and  micrococcus.  Many  of  these  organisms  were  unidentified 
by  Walsh  and  Waldo,  but  it  may  fairly  be  assumed  that,  with  lactic  and 
butyric  ferments  present  in  the  dough,  they  may  be  among  those  organisms 
which  have  lived  through  the  baking.  Hence  they  may  set  up  their  char- 
acteristic fermentations  in  the  baked  bread. 

It  should  be  mentioned  in  passing  that  Walsh  and  Waldo  base  a very 
powerful  argument  for  sanitation  in  bakehouses  on  this  fact,  that  baking 
does  not  necessarily  sterilise  bread.  Their  view  is  that  if  non-pathogenic 
organisms  may  thus  survive,  so  may  also  the  pathogenic  forms  ; and  so 
bread,  if  contaminated  during  manufacture,  may  afterwards  become  a 
source  of  infection.  Goodfellow  finds  that,  provided  the  bread  be  allowed 
to  stand  for  three  hours  in  a germ-free  atmosphere  after  being  baked,  the  loaf 
is  absolutely  sterile.  That  is,  the  act  of  baking,  coupled  with  the  continua- 
ance  of  the  baking  heat  on  the  loaf,  for  the  period  of  time  mentioned,  is 
sufficient  to  destroy  the  life  of  all  micro-organisms.  If  Goodfellow’s  view 
be  correct,  then  the  position  assumed  by  Walsh  and  Waldo  is  no  longer 
tenable. 

The  conditions  of  keeping  make  a considerable  difference  in  the  after- 
sweetness of  baked  bread.  Where  bread  is  kept  in  a close,  warm,  moist 
atmosphere,  from  the  time  of  baking  or  when  new,  it  is  far  more  likely  to 
develop  sourness  and  mould  than  if  stored  where  it  may  rapidly  cool  and 
lose  an}'-  excess  of  moisture. 

586.  Remedies  for  Sour  Bread. — These  are  to  a large  extent  indicated 
in  the  preceding  paragraphs,  but  as  one  possible  cause  of  sour  bread  is  a 
want  of  absolute  cleanliness,  it  should  be  seen  that  all  the  precautions  to 
insure  the  same  are  rigidly  adopted.  Supposing,  as  is  sometimes  the  case, 
that  batch  after  batch  of  bread  is  sour,  or  rapidly  becomes  so  ; then  see 
that  the  flour  is  sound  and  discard  any  very  low  grades  ; next  examine  the 
yeast  ; see  more  especially  whether  disease  ferments  are  plentiful,  and 
whether  the  yeast-cells  themselves  look  healthy  and  vigorous.  The  baker 
who  is  not  able  to  do  this  for  himself  should  place  himself  in  the  hands  of 
an  analyst  to  do  it  for  him.  If  any  suspicion  whatever  attaches  to  the 


BREAD-MAKING. 


451 


yeast  or  the  flour,  change  to  some  other  variety  which  is  known  to  be  doing 
good  work.  In  the  next  place,  thoroughly  clean  the  bakehouse  from  floor 
to  ceihng.  Procure  some  solution  of  bisulphite  of  lime,  and  with  a brush 
wash  floor,  walls,  and  ceiling  with  it.  Clean  out  all  troughs  and  boards, 
and  also  wash  them  with  the  bisulphite,  letting  it  remain  in  the  troughs  for 
some  time.  Then  either  scald  or  steam  them  out,  and  dry  as  rapidly  as 
possible.  These  steps  should  succeed  in  freeing  the  bakehouse  from  any 
•disease  ferments  which  may  be  present. 

In  conducting  fermentation,  use  a sufficient  quantity  of  good  yeast, 
and  work  at  such  a temperature  as  to  get  sponging  and  doughing  over 
quickly. 

As  souring  is  largely  produced  by  some  cause  unduly  accelerating  fer- 
mentation, investigate  the  whole  of  these,  and  modify  one  or  more,  accord- 
ing to  which  seems  faulty,  so  as  to  retard  to  the  normal  rate.  Or,  if  deemed 
preferable,  set  later  or  take  sooner  so  as  to  use  sponges  or  doughs  at  the 
right  stage  of  fermentation.  Use  regular  brands  of  yeast  and  flour,  watch- 
ing and  adjusting  these  as  may  be  necessary.  Souring,  if  due  to  sudden 
atmospheric  changes,  is  to  a certain  extent  beyond  control  ; but  it  may 
be  checked  somewhat  by  cooling,  if  the  too  quickly  working  material  can 
be  caught  in  time.  The  addition  of  salt  to  a too  rapidly  working  sponge 
retards  the  whole  rate  of  fermentation,  and  particularly  that  of  bacteria. 
In  exceptional  cases,  through  the  presence  in  undue  quantities  of  bacteria, 
and  the  use  of  weak  yeasts,  the  fermentation  may  become  abnormal,  and 
sour  fermentation  accompany,  or  even  precede,  the  full  development 
of  normal  alcoholic  fermentation.  Give  the  bread  a good  baking,  as  bread 
which  leaves  the  oven  in  a damp  sodden  condition  is  specially  liable  to 
become  sour.  When  baked,  cool  rapidly  in  a pure  atmosphere.  Weak, 
unstable  flours  used  with  excess  of  water  very  frequently  turn  sour  ; the 
reason  is  that  the  gluten  breaks  down,  and  much  of  the  starchy  interior  of 
the  loaf  is  dextrinised  : the  damp,  clammy  mass  resulting  constitutes  a 
favourable  nidus,  or  home,  for  after-fermentation. 

587.  Ropiness,  Watkins. — One  of  the  most  valuable  contributions  to 
the  bibliography  of  this  subject  is  a paper  on  “ Ropiness  in  Flour  and  Bread, 
and  its  Detection  and  Prevention,’’  read  by  E.  J.  Watkins  before  the  Society 
of  Chemical  Industry,  on  April  2,  1906,  and  published  in  the  Journal  of  the 
Society  for  1906,  p.  350.  The  following  is  an  abstract  of  this  important 
paper  : — 

Occurrence. — During  hot  weather  bread  is  liable  to  an  outbreak  of  the 
disease  called  “ rope.”  Its  first  manifestations  usually  occur  in  from  12 
to  48  hours  after  the  bread  leaves  the  oven. 

Nature  and  Symptoms. — The  bread  acquires  a faint  sickly  odour,  and 
the  crumb  is  infected  with  brovmish  spots,  which  are  larger  the  nearer 
the  centre  of  the  loaf.  With  the  progress  of  the  disease,  the  spots  spread 
and  the  interior  of  the  loaf  becomes  moist  and  sticky.  The  infected 
portions  may  be  drawn  out  into  long  threads,  and  hence  the  name  of  rope. 
With  the  continuation  of  the  disease,  the  crumb  of  the  bread  breaks  down 
into  a molasses-like  mass,  and  emits  an  exceedingly  disagreeable  valerian- 
like odour. 

Susceptibility. — Breads  containing  bran  and  germ,  such  as  whole-meal, 
certain  patent  breads,  and  rye  bread,  are  all  particularly  susceptible.  Of 
those  made  from  white  flour,  the  grades  composed  of  the  heart  of  the  endo- 
sperm, i.e.,  the  best  patent  flours,  are  less  likely  to  produce  rope  than  the 
lower  grade  flours,  which  are  more  or  less  contaminated  with  dust  and  bran 
fragments. 

Origin. — All  modern  vTiters  agree  in  ascribing  rope  to  bacterial  activity. 


452 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


In  the  case  of  liquids,  such  as  beer,  the  condition  of  ropiness  has  been  ex- 
haustively examined,  and  various  organisms  identified  as  the  active  agents. 
Morris  and  Moritz  have  traced  ropiness  in  beer  to  Pediococcus  Cerevisice, 
while  Pasteur  has  associated  it  with  a small  globular  organism  0*0012  to 
0*0014  mm.  in  size.  Ropy  bread  has  been  comprehensively  investigated 
in  Germany  by  Vogel,  who  isolated  two  species  of  bacteria  which  he  identi- 
fied as  belonging  to  the  potato  bacilli  group,  and  which  he  named  B.  Panis 
Viscosus  I.  and  B.  Panis  Viscosus  II.  respectively.  Other  workers  also 
agree  in  finding  potato  bacilli  in  bread. 

Watkins’  Personal  Researches. 

Cultivation  of  Organism. — The  sticky  material  from  the  centre  of  a ropy 
brown  loaf  w^as  removed  with  a sterile  platinum  needle  and  mixed  with 
sterilised  water.  Nutrient  gelatin,  agar-agar,  sterilised  bread,  and  pep- 
tonised  wort  respectively  were  inoculated  with  this  solution,  and  cultivated 
at  26°  C.  in  the  incubator.  Growth  occurred  in  all  cases,  and  microscopic 
examination  showed  the  organism  to  be  a short  motile  bacillus.  This  was 
regrowTi  several  times  in  peptone  wort,  until  a practically  pure  culture  was 
obtained. 

Experiments  on  Sound  Bread. — Sound  loaves,  two  days  old,  were  taken 
and  cut  in  two  with  a sterilised  knife.  On  one  half  .three  loopsful  of  the 
wort  culture  of  the  organism  were  sown,  and  the  bfead  placed  in  a moist 
incubator  at  a temperature  of  28°  C.  The  companion  was  as  a check  placed 
by  its  side.  In  four  such  tests  at  various  temperatures  ropiness  was  found 
to  have  developed  in  the  inoculated  bread  within  12  hours.  The  tempera- 
tures ranged  from  28°  to  35°  C.  and  the  growth  of  rope  was  much  accelerated 
by  the  higher  temperatures.  In  no  case  did  the  uninfected  portion  develop 
ropiness,  though  the  test  was  continued  until  moulds  had  made  their  appear- 
ance. 

Baking  Tests. — These  were  made  with  a sound  patent  flour,  the  materials 
being  mixed  in  a porcelain  trough,  and  the  proportions  similar  to  those  in 
daily  use  for  “ straight  doughs,”  viz.,  280  grams  of  flour,  150  grams  of  dis- 
tilled water,  5 grams  of  yeast,  1 gram  of  sugar,  3*5  grams  of  salt,  thus  mak- 
ing a miniature  sack  batch  with  a yield  of  one  loaf  of  about  400  grams.  [In 
passing,  it  may  be  pointed  out  that  the  yeast  is  in  higher  proportion  than  is 
used  in  a sack  batch,  but  no  higher  than  is  customary  and  advisable  in 
making  small  trial  loaves.]  The  temperature  of  the  dough  was  about  31°  C.  ; 
fermentation  was  allowed  to  proceed  for  2 hours  ; the  dough  was  then 
moulded,  proved,  and  baked  for  40  minutes  at  an  oven  temperature  of 
204°  C.  (400°  F.).  A series  of  seven  such  tests  was  made.  In  five  tests  a 
quantity  of  water,  increasing  from  1 to  5 c.c.,  was  taken  from  the  150  c.c. 
of  doughing  water,  and  replaced  by  a corresponding  quantity  of  the  peptone 
wort  culture  of  the  organism.  The  fermentation  and  baking  of  these  loaves 
proceeded  normally,  and  the  resultant  bread  was  light,  with  a sweet  normal 
odour,  flavour  and  appearance  on  leaving  the  oven.  The  loaves  were  cut 
in  two  with  a sterilised  knife,  and  one  half  of  each  was  placed  in  the  incu- 
bator at  a constant  temperature  and  in  moist  air.  The  check  halves  were 
kept  at  room  temperature  (14°-18°  C.)  in  a dry  atmosphere  for  seven  days, 
and  then  for  another  four  days  at  the  same  temperature  in  a damp  atmos- 
pliere.  In  every  case  where  the  temperature  of  the  loaf  was  kept  below 
18°  G.,  and  whether  in  the  presence  or  absence  of  excessive  moisture,  there 
was  no  development  of  ropiness.  On  the  other  hand,  every  portion  to 
which  any  quantity  of  the  culture  had  been  added  became  ropy  at  tem- 
peratures between  25°  and  30°  C.  in  a moist  atmosphere.  The  presence 
of  the  disease  could  be  detected  by  the  characteristic  smell  long  before  any 
other  obvious  changes  in  the  bread  had  made  the.’r  appearance. 


BREAD-MAKING. 


453 


Further  Temperature  Test. — A sound^loaf  was  cut  in  two  and  each  por- 
tion inoculated  with  1 c.c.  of  a wort  culture.  One  portion  was  placed  in  the 
moist  chamber  at  28°  C.  and  the  other  in  a dry  cupboard  at  16°  C.,  the 
crumb  being  kept  moist  by  the  addition  of  sterilised  water.  The  portion 
at  the  higher  temperature  became  ropy  in  24  hours,  while  that  at  16°  C. 
showed  no  signs  of  the  disease  at  the  end  of  28  days  though  still  quite  moist. 

Conclusions. — Elevated  temperature  appears  to  be  absolutely  necessary 
to  the  development  of  ropiness  in  bread.  Even  when  the  bacillus  is  present 
in  large  numbers,  moisture  alone,  when  the  temperature]  is  low,  is  incap- 
able of  causing  its  appearance. 

Effects  of  Acidity. — In  making  wort  cultures,  it  was  found  that  the 
presence  of  0*1  per  cent,  of  acetic  acid  prevented  the  growth  of  the  organism. 
Lactic  acid  has  a similar  effect.  The  author  of  the  paper  was  therefore 
led  to  try  the  effect  of  the  presence  of  small  quantities  of  acid  in  the  dough. 
A number  of  tests  were  made  and  the  results  recorded  in  which  acetic  acid 
in  quantities  varying  from  0*3  to  1*06  lbs.  to  the  sack  were  used,  and  large 
amounts  of  wort  culture  added.  The  general  result  was  that  acetic  acid 
in  quantities  of  from  0*3  to  0*7  lbs.  to  the  sack  inhibited  the  development  of 
rope.  The  minimum  quantity  would  appear  to  be  0 *3  lbs. , while  any  excess 
over  0*7  lbs.  injuriously  affected  the  gluten.  The  smaller  quantity  of  acetic 
acid  is  not  prejudicial  to  the  general  qualities  of  the  bread.  Lactic 
acid  may  be  employed  instead  of  acetic  acid,  but  the  action  is  somewhat 
uncertain  with  quantities  below  0 *6  lbs.  per  sack. 

Resistance  of  Organism  to  Heat. — The  bacillus  of  rope  or  its  spores  is 
exceedingly  resistant  to  heat.  Thus  an  active  wort  culture  was  immersed 
in  a boiling  water  bath  for  30  minutes  on  three  successive  days.  Cultures 
were  made  from  the  wort  after  each  boiling,  and  yielded  vigorous  growths. 
The  repeatedly  boiled  culture  was  then  used  in  the  dough  of  a trial  loaf, 
and  baked  for  40  minutes.  Notwithstanding  the  severity  of  this  treat- 
ment, the  organism  was  still  extremely  active  and  rapidly  developed  ropi- 
ness in  the  bread.  The  author  of  the  paper  draws  the  conclusion  that  it  is 
hopeless  to  recommend  the  baker  to  give  bread  liable  to  rope  an  extra  long 
baking  in  order  to  prevent  the  appearance  of  the  disease. 

Morphology  and  Identity  of  Organism. — The  following  are  the  character- 
istic details  of  this  organism : A short  rod  with  rounded  ends,  frequently 
united  in  pairs,  seldom  in  chains  of  more  than  three.  It  readily  forms 
ovoid  spores  which  almost  entirely  fill  the  cell.  In  length,  it  is  from  1-1  *25 
P ; in  breadth,  0*75  y. 

When  cultivated  in  hanging  drop,  the  organism  is  sluggishly  motile,  and 
is  surrounded  by  a translucent  capsule. 

It  stains  well  by  Gram,  fuchsin  and  methylene  blue.  Spore  staining 
very  difficult,  usually  only  successful  by  Muller’s  method. 

The  growth  is  best  at  temperatures  between  25-40°  C.,  stagnates  at  15°  C. 

On  agar-agar,  smeary  white  growth,  brownish  on  looking  through  the 
medium,  edges  of  growth  irregular. 

On  gelatin,  shining,  barely  visible,  filmy  growth,  very  slowly  liquefying 
the  medium. 

On  wort  gelatin,  white  crinkled  growth,  slowly  liquefying  medium. 

On  peptonised  wort,  rapid  growth,  rendering  liquid  turbid,  and  forming 
a slimy  gelatinous  film  on  the  sides  of  flask  and  surface  of  liquid.  The  wort 
acquires  a faintly  urinous  odour. 

On  sterilised  bread  the  bread  becomes  brownish  as  if  saturated  with 
syrup,  and  is  gradually  converted  into  a moist  viscous  mass,  emitting  a 
strong  valerian-like  odour. 

In  milk,  causes  coagulation,  and  subsequent  partial  re-solution  of  clot. 

On  potato,  rapid  white  crinkling  growth  ensues,  which  turns  brown 
with  age.  A peculiar  burnt  musty  odour  is  observed. 


454 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  foregoing  characteristics  point  to  the  organism  as  being  identical’ 
with  Bacillus  mesentericus  fuscus  (Fliigge,  Lehmann  and  Neumann^ 
Atlas  of  Bacteriology,  p.  326,  Plate  43). 

Habitat. — The  bacillus  is  a frequent  inhabitant  of  soils,  vegetables, 
including  potato,  and  doubtless  also  the  cereals. 

Infection  of  Doughs. — The  most  important  question  to  the  practical 
baker  is  how  his  doughs  become  infected.  Methods  generally  advocated 
for  prevention  and  cure  of  rope  hold  bakers  almost  entirely  to  blame  for 
its  appearance  in  the  bakery.  For  example,  it  has  been  ascribed  to  damp- 
ness, accumulation  of  dirt  in  false  bottoms  and  crevices  of  troughs,  etc.  The 
suggested  remedies  have  consisted  of  directions  for  purification  and  sterilisa- 
tion of  the  bakehouse  and  all  its  appliances.  These  have  frequently  proved 
totally  inadequate. 

Flour. — A complete  change  of  fiour  has  in  more  than  one  case  resulted 
in  the  complete  disappearance  of  the  disease.  The  experience  was  cited 
of  one  large  firm  of  bakers  who  found  that  this  discarding  of  their  old  flours 
and  their  replacement  by  flours  from  another  source  resulted  in  an  imme- 
diate disappearance  of  the  trouble.  Baking  tests  were  then  made  on  each 
brand  of  flour  in  the  old  stock,  taken  separately,  and  all  but  one  were  found 
to  be  perfectly  sound.  Every  blend  used  into  which  this  flour  had  entered 
was  found  to  yield  ropy  bread.  The  evidence  was  conclusive  that  this  flour 
had  been  the  means  of  introducing  rope  into  the  bakery. 

The  author  of  the  paper  made  a series  of  bacteriological  tests  with  this 
flour.  One  gram  of  the  flour  was  mixed  with  100  c.c.  of  sterile  distilled 
water,  and  1 loopful  of  the  mixture  added  to  various  culture  media.  The 
growths  obtained  were  identical  with  those  previously  isolated  from  ropy 
bread.  Sterilised  bread  was  successfully  inoculated  by  the  addition  of  1 
loopful  of  the  flour  mixture,  blank  check  tests  remaining  unchanged.  Repeat 
cultures  of  the  organism  were  made  in  peptone  wort,  and  these  in  turn, 
when  added  to  the  dough,  induced  rope  in  loaves  made  from  sound  flour. 
On  making  loaves  from  the  suspected  flour  alone,  portions  maintained  at 
26°-30°  C.  in  a moist  atmosphere  developed  rope,  while  the  check  portions, 
preserved  at  a temperature  of  14°-16°  C.  remained  sound  for  as  long  as  14 
days.  These  tests  show  that  the  bacillus  was  undoubtedly  present  in  this 
sample  of  flour. 

Effect  of  Yeast. — In  order  to  determine  whether  the  yeast  played  any 
active  part  in  the  development  of  rope,  some  loaves  were  made  with  this 
flour  and  a commercial  baking  powder.  On  being  tested,  rope  developed  in 
the  same  way  and  at  the  same  rate  as  in  the  yeast-made  bread,  showing  that 
ropiness  is  independent  of  the  presence  of  yeast. 

Modern  Practice. — In  modern  practice,  the  author  of  the  paper  regards 
the  flour  as  the  only  material  responsible  for  the  appearance  of  this  disease. 
Occasionally  in  the  past,  the  bacillus  may  have  been  introduced  by  the  use 
of  potato  ferments  ; but  the  employment  of  potatoes  is  now  almost  obsolete, 
and  the  fact  that  the  rope  bacillus  is  known  to  commonly  exist  in  potatoes 
should  furnish  a strong  additional  reason  for  their  abandonment  in  bread- 
making. 

Practical  Test  for  Rope  in  Flour. — The  following  test  is  intended  for  the 
use  of  practical  bakers  and  millers.  It  is  so  delicate  that  a positive  result  is 
obtained  from  0*02  gram  of  a ropy  flour,  while  there  is  no  fear  that  a genu- 
inely sound  flour  will  be  condemned  by  its  employment.  Ten  test  tubes 
(6  in.  by  I in.)  are  washed,  thoroughly  boiled  in  water  for  I hour,  rinsed* 
and  drained.  When  drained,  they  are  baked  at  232°  C.  (450°  F.)  for  3 
liours  in  order  to  completely  sterilise  them.  [A  baker’s  oven  at  full  bread- 
making heat  sufficiently  answers  the  purpose.]  When  cool,  place  in  each 
tube  a finger  of  bread  3 inches  by  \ inch  by  J inch,  cut  from  the  centre  of  the 


BREAD-MAKING. 


455 


same  2-day  old  loaf.  (The  average  weight  of  each  piece  is  5 grams.)  Moisten 
each  piece  with  5 c.c.  of  recently  boiled  distilled  water,  then  plug  all  tubes 
^vith  cotton-wool  [previously  sterihsed  by  baking  to  a very  light  brown 
tint].  Sterilise  the  tubes  and  their  contents  by  immersion  in  boihng  water 
for  1 hour  on  three  successive  days.  These  tubes  are  conveniently  pre- 
pared in  batches  a few  days  previous  to  being  required. 

In  order  to  test  a flour,  2 grams  are  taken  from  the  sample  and  well 
mixed  with  100  c.c.  of  distilled  water.  The  beaker  containing  the  mixture 
is  placed  in  a boiling  water  bath  for  30  niinutes,  in  order  to  destroy  all  organ- 
isms except  spore  formers  like  the  rope  bacillus,  etc. 

To  seven  of  the  series  of  ten  prepared  tubes  add  successively  1 to  7 c.c. 
of  the  boiled  flour  mixture,  leaving  the  three  remaining  tubes  to  serve  as 
checks.  Immediately  the  tubes  have  been  inoculated,  the  wool  plugs  are 
replaced  and  the  whole  ten  tubes  put  into  an  incubator  of  28°  C.  In  the 
bakery,  they  may  be  put  in  a prover,  or  in  a position  near  the  oven  where 
that  temperature  is  attained  and  where  they  will  be  free  from  dust.  The 
tubes  must  be  examined  at  the  end  of  24  hours,  both  for  the  appearance  of 
the  bread,  and  for  the  smell  of  ropiness.  If  the  rope  bacillus  is  present, 
the  whole  of  the  inoculated  tubes  will  usually  show  signs  of  it.  Should  only 
a portion  of  them,  it  is  well  before  condemning  the  flour  to  repeat  the  test. 
In  any  case  the  check  tubes  must  remain  perfectly  sound,  or  the  experiment 
must  be  rejected.  The  experiment  should  be  continued  for  another  24 
hours,  and  the  tubes  again  examined  at  intervals.  If  there  is  no  indication 
of  ropiness  in  48  hours,  the  flour  may  be  passed  as  sound.  Beyond  that 
time  the  development  of  moulds  and  other  organisms  interferes  with  the 
success  of  the  test. 

Summary. — Ropiness  in  bread  is  produced  by  varieties  of  B.  Mesen- 
tericus  (Fliigge),  introduced  into  the  dough  through  the  flour,  in  which  it 
sometimes  occurs  in  large  numbers,  possibly  coming  from  the  bran  coatings. 
Breads  containing  bran  and  low  grade  white  flours  are  most  prone  to 
develop  ropiness. 

The  bacillus  is  a proliflc  spore  former,  the  spores  being  capable  of  resisting 
high  temperatures  for  prolonged  periods. 

Once  present  in  the  dough,  development  of  the  bacillus,  after  bread 
has  been  made,  depends  partly  upon  the  reaction  of  the  bread  and  partly 
upon  atmospheric  conditions. 

Bread  is  only  faintly  acid  in  reaction  and  always  insufficiently  so  to 
naturally  prevent  the  development  and  spread  of  ropiness,  but  if  the  acidity 
be  increased  by  addition  of  small  quantities  of  acetic  acid  to  the  dough,, 
development  can  be  prevented. 

Low  temperature  and  dryness  of  the  bread  store  tend  to  suppress  develop- 
ment, but  the  maximum  temperature  of  18°  C.  (65°  E.)  cannot  be  exceeded 
without  great  risk. 

When  a batch  of  bread  is  found  to  be  ropy,  all  flour  in  stock  should  be  at 
once  tested,  so  as  to  locate  the  infected  stock,  and  in  the  meantime  fresh 
supplies  of  flour  from  a different  source  should  be  laid  in. 

When  the  infected  batch  of  flour  has  been  discovered,  it  should  be  iso- 
lated, so  that  it  can  be  worked  up  under  those  conditions  which  are  most 
unfavourable  to  the  development  of  the  bacillus,  Le.,  the  doughs  being 
made  slightly  acid  and  the  bread  being  quickly  cooled  and  kept  at  low 
temperature  during  storage.  Such  flour  might  advantageously  be  kept 
’ until  the  colder  months,  when  the  prospects  of  development  are  at  a mini- 
mum. 

During  the  summer  months,  the  danger  of  purchasing  ropy  flour  may 
be  entirely  obviated  by  the  apphcation  of  the  bread  tube  test  before  buying. 
(Jour.  Soc.  Chem.  Ind.,  1906,  350.) 


456 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Watkins’  experiments  would  have  been  more  complete  had  they  included 
investigations  as  to  how  far  the  development  of  ropiness  was  affected  by 
the  comparative  moisture  of  bread  at  temperatures  slightly  higher  than  the 
lower  limit  of  activity  of  the  rope  bacillus.  He  has  made  it  perfectly  clear 
that  with  a temperature  below  18°  C.  the  presence  of  moisture  does  not 
cause  the  development  of  ropiness.  At  20°  C.,  there  would  probably  be  a 
much  more  rapid  development  in  a moist  loaf  than  in  a very  dry  one.  Some 
measurements  of  this  stimulating  effect  of  moisture  would  have  added  to  the 
value  of  a very  valuable  paper.  Previously  published  recommendations 
to  the  baker  to  give  his  bread  an  extra  long  baking,  in  case  of  his  being 
troubled  with  rope,  were  not  probably  based  on  any  hope  thus  to  kill  the 
rope  organism,  but  rather  to  make  the  bread  drier,  and  thus  a less  favour- 
able medium  for  the  spread  of  this  disease. 

There  can  be  little  doubt  that  Watkins  has  traced  the  source  of  many 
if  not  most  of  the  cases  of  ropiness  which  trouble  the  baker.  But  granted 
that  the  flour  is  the  channel  of  introduction  ; when  once  the  rope  bacillus 
has  permeated  the  troughs  and  other  utensils,  the  whole  of  the  advocated 
precautions  for  cleaning  and  sterilising  these  have  all  the  force  and  neces- 
sity which  has  been  attributed  to  them. 

The  rope  bacillus  is  a very  ready  spore-forming  bacillus,  and  a bakery 
is  from  its  nature  and  character  a place  where  spores  are  readily  liberated 
and  disseminated  through  the  atmosphere.  There  are  frequently  cases  of 
rope  which  it  is  almost  impossible  to  explain  otherwise  than  by  aerial  infec- 
tion. Such  cases  are  those  in  which  a complete  ehange  of  flour  has  not 
cured  the  disease,  and  where  one  miller’s  flour  is  producing  ropy  bread  in 
one  bakery,  while  the  same  flour  is  yielding  perfectly  sound  bread  in  another. 
The  cleansing  and  sterilising  of  a whole  bakery  is  not  necessarily  therefore 
a useless  proceeding,  but  may  be  an  absolute  necessity,  should  the  entire 
building  become  infected  with  the  rope  bacillus.  These  references  are  made 
not  with  the  view  of  discounting  the  conclusions  arrived  at  by  Watkins,  but 
rather  with  the  object  of  indicating  some  possible  additional  sources  of 
infection  and  the  precautions  to  be  in  those  cases  taken. 

The  reading  of  the  paper  was  followed  by  an  interesting  discussion, 
the  more  important  points  of  which  are  here  given.  The  chairman,  Sala- 
mon,  drew  attention  to  the  strong  smell  of  acetic  acid  exhibited  by  a speci- 
men loaf,  and  inquired  as  to  what  would  be  the  effect  of  traces  of  nitrogen 
peroxide  on  this  bacillus  in  flour,  in  the  manner  used  for  bleaching  purposes. 
Jago  asked  whether  the  author  had  tried  using  the  odourless  mineral  acids 
as  sulphuric  or  phosphoric  acid,  and  expressed  a doubt  as  to  whether  the 
baker  would  regard  the  substitution  of  sourness  for  ropiness  as  an  advan- 
tage. He  pointed  out  that  the  presence  of  dextrinous  or  gummy  bodies 
in  bread,  caused  it  to  become  ropy  much  more  readily  than  did  the  drier 
types  of  bread.  Hooper  insisted  on  the  necessity  of  flour  being  kept  dry 
and  not  allowed  to  get  damp,  remarking  that  many  possibly  mischievous 
organisms  were  more  widely  spread  than  was  commonly  supposed,  and 
were  held  in  check  by  avoiding  the  conditions  necessary  for  their  develop- 
ment. Humphries  found  that  the  addition  of  0*25  per  cent,  of  lactic  acid 
was  quite  sufficient  absolutely  to  spoil  bread  for  commercial  purposes. 
Briant  found  ropiness  to  be  generally  associated  with  excessive  moisture 
in  bread,  and  also  regarded  the  addition  of  acid  as  causing  bread  to  become 
chaffy  in  character.  Rideal  recommended  the  use  of  bisulphite  of  soda  in 
the  place  of  free  acids  for  the  inhibition  of  ropiness.  Several  other  speakers 
dealt  with  the  question  of  the  identity  of  the  organism.  Watkins  briefly 
replied  on  the  whole  discussion.  He  did  not  regard  bleaching  as  having  a 
sterilising  effect  on  flour,  since  one  of  the  flours  which  yielded  ropy  bread  had 
as  a matter  of  fact  been  bleached.  Mineral  acids  should  not,  he  thought, 


BREAD-MAKING. 


457 


be  used  in  an  article  of  diet.  Calculation  showed  that  0*3  lbs.  of  acetic 
acid  to  the  sack  only  increased  the  percentage  of  acid  by  0*0708  per  cent., 
and  that  quantity  did  not  interfere  with  the  production  of  a good  sweet 
loaf.  {Jour.  Soc.  Chem.  Ind.,  1906,  350.) 

588.  Chalk  Disease  in  Bread. — Lindner  describes  a new  fermentation 
fungus,  Endomyces  fibuliger,  which  produces  the  so-called  chalk  disease  of 
bread.  The  result  of  the  action  of  this  organism  is  to  form  white  chalky 
spots  on  bread.  It  closely  resembles  Monilia  verhialis,  from  which  it  differs 
however  by  its  ability  to  liquefy  wort  gelatin.  The  organism  ferments 
sucrose  vigorously,  and  also  glucose,  though  somewhat  more  slowly.  The 
original  article  contains  a large  number  of  illustrations  of  the  organism. 
{Z.  Spiritusind,  1908,  31,  162.) 

Faults  in  Bread. 

589.  Holes  in  Bread. — Instead  of  the  even  sponginess  which  should 
characterise  the  crumb  of  good  bread,  one  is  occasionally  confronted  with 
loaves  in  which  large  holes  occupy  considerable  spaces  in  the  interior  of  the 
loaf.  For  their  occurrence  various  explanations  have  been  offered,  many 
of  which  are  ingenious,  while  others  are  impossible.  An  interesting  object 
lesson  in  their  production  may  be  gained  by  taking  a basin  of  strong  solution 
of  soap  in  water,  and  blowing  into  it  through  a glass  tube.  A mass  of 
bubbles  is  formed  on  the  surface  of  the  solution,  which  fills  the  whole  vessel. 
Let  it  rest,  and  watch  the  gradual  disappearance  of  the  bubbles- — careful 
inspection  will  show  in  the  interior  of  the  mass  some  of  the  bubble  walls 
getting  thinner  and  thinner,  until  at  last  they  collapse,  and  several  small 
bubbles  coalesce  to  form  one  of  large  size.  Practical^  the  same  thing 
occurs  in  dough  ; if  allowed  to  get  over-proved,  it  will  be  seen,  on  being 
cut,  to  contain  a number  of  large  holes.  Good  firm  moulding  will  remove 
the  gas  from  these,  and  make  a piece  of  homogeneous  dough  for  the  loaf,  thus 
remedying  one  cause  of  holeyness  ; for  if  a loaf  containing  these  large  holes 
be  placed  in  the  oven,  they  will  expand  there,  and  thus  give  still  more 
irregular  aeration.  The  same  process  of  a number  of  small  holes  breaking 
down  into  one  big  one  may  occur  during  baking  in  a piece  of  dough,  which, 
if  cut  prior  to  its  going  into  the  oven,  would  show  no  signs  of  large  holes. 
Here  the  cause  must  be  lack  of  tenacity  in  the  dough  which  forms  the  hole- 
walls,  and  the  cause  of  such  holes  must  be  found  in  the  constituents  of  the 
dough.  The  elasticity  of  dough  at  this  stage  is  principally  due  to  the  gluten 
present,  and  when  fermentation  has  been  carried  sufficiently  far  to  destroy 
the  tenacity  of  the  gluten,  breaking  down  into  holes  is  a normal  result  : 
holeyness,  therefore,  for  this  reason  may  be  an  accompaniment  of  over- 
worked dough.  If  a series  of  loaves  be  made  as  suggested  in  paragraph 
581,  it  is  very  rarely  that  holes  are  found  in  the  earlier  and  under-fermented 
loaves.  Another  cause  of  this  irregularity  is  the  insufficient  breaking  down 
and  mixing  of  the  sponge  with  the  water  and  flour  of  the  dough.  The  latter 
is  frequently  made  from  a comparatively  soft,  weak  flour,  and  if  not  thor- 
oughly incorporated  wdth  the  sponge,  leaves  portions  of  inferior  tenacity 
which  may  readily  break  into  holes.  The  production  of  holes  by  dusting 
flour  being  folded  up  in  the  interior  of  the  loaf  during  moulding,  and  then 
not  thoroughly  worked  in,  thus  leaving  blebs,  which  expand  into  holes  on 
baking,  is  so  absolutely  a result  of  carelessness  as  to  need  no  further  refer- 
ence. 

A curious  problem  about  holes  is  the  liability  of  cottage  loaves  to  this 
fault.  If  some  of  the  same  dough  be  made  into  “ cakes  ” or  “ Coburg 
loaves,  while  the  remainder  is  made  into  cottages,  the  latter  are  far  more 


458 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


likely  to  contain  holes  than  the  former.  One  cause  of  this  is  possibly  the 
inefficient  “ bashing  down  of  the  tops  of  the  cottages.  A more  likely 
reason  is,  however,  the  actual  shape  of  the  loaf  itself.  The  top,  being 
smaller,  acquires  a rigid  crust  before  the  lower  part  of  the  loaf,  and  therefore 
forms  a sort  of  protecting  cap  over  the  centre.  As  expansion  goes  on  in  the 
interior  during  baking,  there  is  a line  of  comparatively  little  resistance 
immediately  underneath  the  top,  and  greater  expansion  takes  place  in  this 
direction.  Evidence  of  this  is  afforded  by  the  species  of  risen  waist  one 
sometimes  sees  in  a cottage  loaf,  consisting  of  what  looks  like  a third  or 
middle  piece  in  the  loaf.  This  development  occurs  after  the  rest  of  the  loaf 
has  set  ; and,  as  probably  the  interior  dough  has  also  lost  much  of  its  elas- 
ticity, there  is  the  formation  of  a large  hole  rather  than  even  expansion. 
Of  course  the  occurrence  of  such  holes  means  a predisposition  of  the  dough 
to  breaking  down  into  irregular  aeration. 

The  causes  of  holes  in  bread  may  be  summed  up  as  being — careless 
moulding,  especially  of  over-proved  dough  ; lack  of  tenacity  and  elasticity 
of  the  dough  itself,  due  to  soft  and  irregular  flours  ; insufficient  mixing  of 
sponge  and  dough.  Cottage  loaves  are  prone  to  holes  because  of  the  physical 
effect  of  their  shape  on  expansion  during  baking. 

590.  Protruding  Crusts. — On  crusty  bread  being  packed  a little  too  close 
in  the  oven,  the  loaves,  on  expanding,  touch  their  neighbours,  and  a soft 
crust  is  formed  when  they  are  in  contact.  Occasionally,  when  the  dough 
is  weak  and  inclined  to  “ run,""  it  may  be  observed  that  the  loaves  definitely 
grow  toward  one  another,  forming  a distinct  protuberance  on  the  side  of 
each,  as  though  an  endeavour  was  being  made  on  the  part  of  the  loaves  to 
effect  actual  contact.  This  apparent  attraction  is  due  to  the  mutual  cooling 
effect  of  the  loaves  retarding  the  formation  of  a rigid  crust  on  the  contiguous 
parts  : expansion  continues  there  after  the  other  parts  of  the  loaves  are  set, 
and  hence  the  “ kissing  ""  growth  toward  each  other. 

591.  Crumbliness. — ^The  crumbling  away,  instead  of  cutting  cleanly, 
exhibited  by  some  bread,  may  be  due  to  the  use  of  harsh,  dry  flours,  not 
sufficiently  fermented  ; or  may  also  be  caused  by  over-working  and  proof, 
making  the  loaf  bigger  than  the  gluten  of  the  dough,  at  the  stage  of  fermen- 
tation when  baked,  is  able  to  stand  and  still  hold  the  bread  well  together. 
A deficiency  of  dextrin  and  soluble  starch  in  the  bread  also  contributes  to 
crumbliness. 

592.  Dark  Line  in  Cottages. — At  times,  on  cutting  a cottage  loaf,  a dark 
line  is  seen  across  the  contact  surface  between  the  top  and  bottom  of  the 
loaf.  Generally  when  this  is  the  case,  if  the  loaf  has  any  soft  crust,  that 
too  is  seen  to  be  discoloured.  The  bread  is  under  these  circumstances  fre- 
quently either  sour,  or  approaching  it.  The  primary  cause  of  this  dark 
line  is  the  darkening  by  oxidation  of  some  of  the  constituents  of  the  flour  ; 
this  darkening  goes  on  more  rapidly  in  doughs  made  from  low  grade  flour  or 
which  have  been  over  worked.  Proof  of  this  darkening  of  dough  is  afforded 
by  pressing  a piece  of  dough  down  into  contact  with  colourless  glass,  and 
letting  it  stand  a time.  The  air- exposed  surface  rapidly  becomes  the  darker 
of  the  two.  This  darkening  has  been  found  to  be  the  result  of  the 
action  of  an  enzyme  to  which  the  name  of  oxydase  has  been  given. 
In  making  sample  loaves,  especially  from  dark  flours,  a streakiness  is 
often  observed.  The  proportionately  large  external  surface  darkens,  and 
each  time  the  dough  is  moulded,  the  dark  portion  is  worked  into  the 
interior,  and  hence  the  streaky-baked  bread.  In  any  loaf  which  has  been 
allowed  to  stand  there  is  more  or  less  darkening  of  the  exterior  by  oxidation 
— on  baking,  this  colouration  is  altogether  masked  by  the  caramelisation  of 


BREAD-MAKING. 


459' 


the  crust.  But  where  the  two  exteriors  have  been  placed  together,  as  in 
the  surface  of  contact  of  the  two  parts  of  a cottage,  the  darkening  effect  of 
oxidation  is  preserved,  and  may  be  noticed  in  the  baked  loaf. 

593.  Working  with  Unsound  or  very  Low  Grade  Flours. — In  the  older 
literature  of  bread-making  it  is  interesting  to  read  the  directions  given 
under  this  head  ; when,  through  a bad  harvest,  wheat  has  either  not  ripened 
properly,  or  has  after  the  reaping  been  badly  wetted,  great  care  is  necessary 
in  order  to  make  a passable  loaf  of  bread  from  the  flour  produced.  But 
the  United  Kingdom  can  now  command  the  markets  of  the  world,  and 
without  any  difficulty  secure  sound  wholesome  wheats  at  a fair  price.  In 
the  present  day  there  is  practically  no  excuse  for  a baker  having  a sack  of 
unsound  flour  in  his  flour  room. 

In  composition  the  unsound  flours  have  a low  percentage  of  gluten, 
and  that  badly  matured  ; while  the  soluble  proteins  are  high,  and  in  a com- 
paratively active  diastatic  condition.  The  starch  granules  have  their  walls 
softened  dovm  and  often  fissured.  The  moisture  is  high,  so  also,  owing  to 
the  degradation  of  starch  and  proteins,  is  the  soluble  extract.  These  flours 
are  found  on  testing  to  be  weak  and  unstable.  So  far  as  their  treatment 
is  concerned,  that  commences  with  the  wheats  rather  than  with  the  Hours. 
A wheat  harvested  damp  is  not  necessarily  unsound ; these  chemical  changes 
are  to  a great  extent  an  after-consequence  of  the  dampness.  Such  wheats 
should  immediately  on  being  harvested  be  kiln  dried  at  a gentle  heat  of 
about  38°  C.  (100°  F.),  until  the  moisture  present  is  reduced  to  10  per  cent, 
of  the  whole  grain.  While  the  flour  produced  from  the  wheat  thus  treated 
may  be  weak,  it  will  be  fairly  stable  and  not  unsound.  The  gluten  will  be 
higher,  and  the  soluble  extract  and  proteins  comparatively  low.  The 
experiments  described  in  paragraph  494  show  that  even  weak,  damp 
flours  may  be  considerably  improved  by  gentle  kiln-drying  of  the  flour 
itself.  Such  treatment  is  also  by  far  the  best  that  can  be  adopted  with 
unsound  flours  ; those  flours  which  are  not  amenable  to  it  should  be 
entirely  rejected  for  bread-making  purposes. 

Having  by  preliminary  treatment  made  the  best  of  an  unsound  flour, 
it  should  be  used  in  the  dough,  which  should  be  got  into  the  oven  as  speedily 
as  possible.  Or,  the  whole  of  the  flour  may  be  worked  with  a straight 
dough  on  a very  short  system,  using  yeast  in  good  quantity.  A little  com- 
pressed yeast  added  at  the  dough  stage  will  often  be  found  of  service  by 
hastening  the  fermentation.  As  unsound  flours  are  particularly  liable  to 
produce  sour  bread,  special  attention  should  be  paid  to  the  suggestions 
made  in  paragraph  584  on  Sour  Bread.  Further  reference  to  unsound  flours 
will  be  found  in  the  paragraphs  describing  other  methods  of  aerating  bread. 

The  low  grade  flours  of  gradual  reduction  processes  are,  if  from  a sound 
wheat,  perfectly  sound  in  themselves  ; yet  they  require  some  care  in  mani- 
pulation, because  they  contain  the  active  diastatic  constituent  of  the  bran, 
cerealin,  in  considerable  quantity.  Where  these  flours  are  employed,  a 
sponge  should  be  prepared  from  a strong  flour  and  the  low  grade  used  in  the 
dough,  or  the  low  grade  flour  worked  by  a short  straight  dough  system. 

594.  Use  of  Alum,  Copper  Sulphate,  and  Lime. — ^Alum,  the  double  sul- 
phate of  aluminium  and  potassium,  Al2K2(S04)424H20,  was  formerly 
largely  used  as  an  adulterant  of  bread.  This,  and  the  other  substances 
mentioned,  behave  as  retarding  agents  to  diastasis  ; with  unsound  flours 
they  prevent  or  lessen  the  degradation  of  the  gluten  and  starch  during 
fermentation,  and  so  cause  a loaf  made  from  a bad  flour  to  be  larger,  less 
sodden,  and  whiter,  giving  it  the  appearance  of  bread  made  from  far  better 
flour.  So  far,  and  considered  from  this  aspect  alone,  the  action  of  alum 


460 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


is  remedial ; it  prevents  undesirable  changes  occurring  in  the  flour  during 
fermentation.  There  is  no  doubt  that  by  the  use  of  alum,  flour,  so  bad  as 
to  render  bread-making  in  the  ordinary  manner  impossible  with  it,  can  be 
converted  into  eatable  loaves  ; but  if  necessity  arises  for  recourse  to  such 
flours  for  bread-making,  other  processes  are  now  known  which  achieve  the 
same  object  by  methods  that  are  absolutely  unobjectionable.  The  con- 
tinued use  of  alum,  even  in  small  quantity,  is,  according  to  medical  evidence, 
injurious  to  health  : in  particular,  the  alum  remaining,  as  it  does,  unchanged 
in  the  bread,  retards  the  digestive  action  of  the  secretions  of  the  mouth 
and  stomach.  As  alum  is  injurious,  and  as  it  is  used  with  the  object  of  enabling 
inferior  flour  to  be  substituted  for  that  of  good  quality,  to  the  prejudice  of  the  con- 
sumer, it  is  rightly  considered  as  an  adulterant,  and  its  use  made  penal. 

Minute  quantities  of  copper  sulphate,  CuSOi,  have  also  been  employed  : 
its  action  is  very  similar  to  that  of  alum  ; but  as  all  copper  salts  are  very 
poisonous,  its  use  is  even  more  reprehensible  than  that  of  the  former  adulterant. 

Liebig  suggested  the  employment  of  lime  in  solution,  lime-water, 
CaH202,  as  a means  of  preventing  excessive  diastasis  during  panary  fermen- 
tation. This  substance  is  quite  as  effective  as  alum  so  far  as  the  effect  on 
diastasis  is  concerned,  but  unlike  alum  it  exerts  very  little  retardation  on 
the  alcoholic  fermentation  caused  by  the  yeast.  Lime  is  soluble  in  about 
780  parts  of  cold  water  : its  solution,  or  what  is  commonly  called  lime- 
water,  may  be  prepared  by  adding  about  2 ozs.  of  recently  burned 
quicklime  to  10  gallons  of  water,  and  stirring  up.  A better  plan  is  to  add 
the  lime  in  considerable  excess,  stir  thoroughly,  and  then  allow  the  super- 
fluous lime  to  settle.  In  a few  hours  the  upper  liquid  becomes  clear,  and 
may  be  dipped  off  without  disturbing  the  sediment.  Some  more  water 
may  then  be  added  and  the  mixture  again  stirred  ; another  quantity  of 
lime-water  is  thus  made.  This  operation  may  be  repeated  several  times  if 
sufficient  lime  has  been  taken  in  the  first  place.  Any  vessels  containing 
lime-water  have  to  be  kept  covered,  as  carbon  dioxide  is  rapidly  absorbed 
from  the  air,  with  the  formation  of  calcium  carbonate.  Richardson  states 
that  Liebig’s  directions  were  that  the  flour  and  lime-water  should  be  used 
in  the  ratio  of  19  of  flour  to  5 of  lime-water,  and  then  goes  on  to  say  that 
that  quantity  of  liquid  not  being  sufficient  to  convert  the  flour  into  dough, 
the  requisite  quantity  of  ordinary  water  was  added.  He  then  proceeds 
to  quote  an  experiment  in  which  19  lbs.  of  flour  were  made  into  bread  with 
ordinary  water,  and  yielded  24  lbs.  8 oz.  of  bread.  A like  quantity  of  the 
same  flour,  kneaded  with  5 quarts  of  lime-’water,  produced  26  lbs.  6 oz. 
of  bread.  There  is  evidently  a mistake  here  somewhere  : 5 quarts  of  water 
to  19  lbs.  of  flour  means  73  quarts  of  water  to  the  sack  ; this  quantity,  so 
far  from  not  being  sufficient  to  convert  the  flour  into  dough,  is  something 
like  10  quarts  more  w^ater  than  is  ordinarily  used  by  the  London  baker.  As 
on  the  continent  the  metric  system  of  weights  and  nieasures  is  that  commonly 
used,  Liebig’s  ratio  was  in  all  probability  19  kilograms  of  flour  to  5 litres  of 
water,  the  exact  equivalent  of  which  would  be  19  lbs.  of  flour  to  5 lbs.  or 
2 quarts  of  water  ; this  equals  29  quarts  of  lime-water  to  the  sack.  The 
deficiency  is  then  made  up  by  the  addition  of  ordinary  water.  The  baker 
desiring  to  use  lime-water  may  make  it  and  employ  it  in  the  proportion 
just  stated,  or  he  may  add  not  more  than  1 J ounces  of  lime  to  the  water  per 
sack  of  flour.  In  this  latter  case  he  must  stir  the  water  thoroughly  so  as 
to  ensure  the  complete  solution  of  the  lime  : a milkiness  throughout  the 
whole  of  the  water  would  not  hurt,  but  any  lumps  must  be  avoided.  The 
safest  method  is  to  prepare  the  lime-water  as  a previous  operation.  Lime- 
water  is  used  by  some  of  the  Glasgow  bakers,  who  advertise  bread  contain- 
ing it  as  a speciality.  The  bread  made  with  lime-water  is  more  spongy  in 
texture,  pleasant  to  taste,  and  quite  free  from  sourness.  In  the  finished 


BREAD-MAKING. 


461 


bread  the  lime  no  longer  exists  as  free  alkali,  because  the  carbon  dioxide 
gas  generated  during  fermentation  will  have  completely  changed  it  intn 
calcium  carbonate — 

CaHsO^  + COo  = CaCOa  -f  H^O. 

Lime.  Carbon  Dioxide.  Calcium  Water. 

Carbonate. 

Calcium  carbonate,  which  is  identical  in  composition  with  chalk,  has  in 
small  quantities  no  deleterious  action  when  taken  into  the  system,  and  may 
very  possibly  add  to  the  nutritive  value  by  remedying  the  natural  deficiency 
of  wheat  in  lime  salts.  See  paragraphs,  648-651. 

So  far  as  Richardson's  quotation  of  experiment  may  be  depended  on, 
it  indicates  an  increased  yield  of  bread  by  the  use  of  lime-water  : he  ascribes 
this  increase  to  the  loss  caused  by  fermentation  when  working  in  the  ordinary 
manner  ; but  his  views  on  this  subject  have  already  been  shown  to  be  fal- 
lacious. Tlie  true  explanation  is  a very  simple  one  : the  lime-water,  by 
preventing  the  degradation  of  the  gluten  and  the  diastasis  of  the  starch, 
increases  the  water-retaining  power  of  the  flour,  and  so  enables  the  same 
weight  to  yield  a greater  quantity  of  bread. 

595.  Special  Methods  of  Bread-making. — There  are  certain  special  pro- 
cesses employed  for  bread-making  which  must  next  be  described. 

596.  “ Vienna  Bread.” — This  is  the  name  applied  to  rolls  and  other  light 
fancy  bread.  Vienna  bread  is  made  with  patent  flour  and  compressed 
yeast.  No  potatoes  or  ferment  is  used.  Instead  of  water,  the  bread  is 
sometimes  made  with  milk  or  a mixture  of  milk  and  water.  The  following 
recipe  is  quoted  from  The  Miller  : — 

Proportions. — 8 lbs.  of  flour,  3 quarts  of  milk  and  water  in  equal  pro- 
portions, 3J  ounces  of  compressed  yeast,  and  I ounce  of  salt.  The  warm 
water  is  first  mixed  with  the  milk,  so  as  to  give  a temperature  of  from  80 
to  85°  F.  Sufficient  flour  is  then  added  to  make  a weak  sponge,  not  much 
thicker  than  a batter.  The  yeast  is  crumbled,  mixed  well  in,  and  the  sponge 
allowed  to  stand  for  about  45  minutes.  The  rest  of  the  flour  is  next 
added  slowly,  together  with  the  salt  ; the  dough  is  then  thoroughly  kneaded 
and  set  to  ferment  for  2 J hours.  All  Hungarian  flour  may  be  used  through- 
out, or  the  finest  English  milled  flour  may  be  substituted  therefor.  The 
bread  is  glazed  during  baking  by  the  introduction  of  a jet  of  steam  into  the 
oven. 

597.  Leavened  Bread. — In  France  and  other  parts  of  the  continent  bread 
is  made  from  leaven,  which  consists  of  a portion  of  dough  held  over  from 
the  previous  baking.  The  following  description  is  given  on  the  authority 
of  Watt's  Dictionary  of  Chemistry.  A lump  of  dough  from  the  preceding 
batch  of  bread  is  preserved  ; this  weighs  about  12  lbs.,  made  up  of 
8 lbs.  of  flour  to  4 lbs.  of  water,  and  is  the  fresh  leaven  {levain  de 
chef).  This  fresh  leaven,  after  remaining  for  about  10  hours,  is  kneaded 
in  with  an  equal  quantity  of  fresh  flour  and  water,  and  thus  produces  the 
levain  de  premiere  ; again,  this  is  allowed  to  stand  for  some  hours  (about 
eight),  and  is  kneaded  in  with  more  flour  and  water.  After  another  interval 
of  3 hours,  100  lbs.  of  flour,  52  of  water,  and  about  lb.  of  beer  yeast 
are  added  ; this  produces  the  finished  leaven  {levain  de  tout  point).  The 
finished  leaven  weighs  about  200  lbs.,  and  is  mixed,  after  standing  2 hours, 
with  132  lbs.  of  flour,  68  lbs.  of  water,  J lb.  yeast,  and  2 lbs.  of  salt.  The 
dough  thus  formed  is  divided  into  two  moieties  ; the  one  is  cut  into  loaves, 
which  are  kept  for  a time  at  a moderate  temperature  (77°  F.  and  then  baked). 
The  bread  thus  produced  is  sour  in  taste  and  dark  in  colour.  The  remain- 
ing half  of  the  dough  is  kneaded  with  more  flour,  water,  yeast,  and  salt 


462 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  divided  into  halves  ; the  one  quantity  is  made  into  loaves,  which  are 
•allowed  to  ferment  and  then  baked  ; the  other  is  subjected  again  to  opera- 
tion of  mixing  with  more  flour,  etc.,  and  working  as  before.  The  sub- 
division is  repeated  three  times  ; the  bread  improving  at  each  stage,  and 
the  finest  and  whitest  loaves  being  produced  in  the  last  batch.  In  the  more 
important  towns  this  mode  of  bread- making  is  now  largely  supplanted  by 
the  use  of  distillers’  yeast,  and  seems  now  to  have  largely  given  place  to 
methods  more  nearly  allied  to  Viennese  and  English  processes. 

598.  Theory  of  Leaven  Fermentation. — In  May,  1883,  Chicandard  com- 
municated to  the  Academy  of  Sciences,  Paris,  a theory  of  panification 
adopted  by  him  as  the  result  of  recent  researches.  He  first  expressly  states 
that  his  conclusions  do  not  apply  to  fermentation  as  conducted  in  England, 
but  to  bread  made  on  the  leaven  system.  English  bread  is  excepted  be- 
cause of  its  being  customary  to  add  potatoes  to  the  ferment,  the  gelatinised 
starch  of  which  he  admits  may  be  susceptible  of  alcoholic  fermentation. 
But  as  many  English  bakers  make  their  bread  from  flour,  yeast,  salt,  and 
water  only,  any  alcoholic  fermentation  which  occurs  cannot  be  explained 
by  the  general  statement  that  English  bakers  use  fruit.  Briefly  summing  up 
Chicandard’s  conclusions,  they  are — “ The  fermentation  of  bread  does  not 
consist  in  the  hydrolysis  of  starch,  followed  by  alcoholic  fermentation,  and 
is  not  determined  by  Saccharomyces,  but  is  a result  of  the  solution  and  after 
peptonisation  of  the  gluten,  this  effect  being  caused  by  a bacterium  which 
develops  itself  normally  in  the  dough,  yeast  merely  accelerating  such  de- 
velopment.” 

In  proof  that  the  gas  evolved  during  panification  is  not  the  result  of 
alcoholic  fermentation,  Chicandard  states  that  the  presence  of  alcohol  has 
never  been  proved  : in  this  he  is  contradicted  by  Moussette,  who  detected 
alcohol  in  the  gases  of  an  oven  in  use  in  France  so  early  as  1854,  and  at  a 
time  when  the  bread  was  undoubtedly  being  made  by  the  leaven  process. 
In  a further  communication  Chicandard  states  that  he  made  a dough  with 
flour,  glucose,  yeast  and  water,  testing  it  immediately  on  being  made, 
and  again  after  standing  three  and  seven  days  respectively  ; he  found  in 
each  case  that  10  grams  of  the  dough  contained  0 *55  grams  of  glucose. 

Girard  has  since  pointed  out  in  the  Comptes  Rendus,  that  he  has  exam- 
ined the  gas  contained  in  dough  at  various  stages  of  preparation,  and  finds 
it  to  consist  mainly  of  carbon  dioxide,  mixed  with  the  air  originally  con- 
tained in  the  flour.  In  some  cases  part  of  the  oxygen  had  been  absorbed, 
most  probably,  Girard  thinks,  as  a consequence  of  the  secondary  formation 
of  acetic  acid.  [The  authors’  opinion  is  that  this  absorption  is  due  to  the 
direct  action  of  the  yeast ; which  organism,  as  has  been  already  demonstrated, 
exhibits  a remarkable  avidity  for  oxygen.]  On  mixing  the  dough  vdth 
water  and  distilling,  the  distillate  was  found  to  contain  alcohol  in  quantity 
amounting  to  3*15  c.c.  or  2*5  grams  per  kilogram  of  dough.  The  same 
results  were  obtained  whether  the  dough  was  mixed  with  leaven  or  with. 
yeast,  thus  affording  additional  evidence  that  the  rising  of  dough  is  due  to 
alcoholic  fermentation 

Boutroux,  also  in  Comptes  Rendus  (113,  203-206),  states  the  results  of 
investigations  on  this  point.  He  states,  in  leavens  to  which  no  yeast  had 
ever  been  added  since  time  immemorial,  that  he  always  found  yeasts,  and 
isolated  five  distinct  species,  two  of  which  are  very  active  in  producing 
alcoholic  fermentation.  From  the  flour  he  isolated  three  distinct  species 
of  bacteria  : a,  which  secretes  a diastase  that  dissolves  cooked  gluten  and 
saccharifies  stareh  paste,  but  does  not  attack  sugar  ; 6,  which  produces 
fermentation  with  evolution  of  gas,  in  a mixture  of  flour  and  water  sterilised 
by  heat  ; and  c,  obtained  from  the  bran,  which  produces  a fermentation, 


BREAD-MAKING. 


463 


with  evolution  of  gas  in  a mixture  of  bran  and  water.  Bacillus  a,  followed 
by  yeast,  produces  alcoholic  fermentation.  Direct  experiment  showed 
that  the  yeasts  active  in  producing  alcoholic  fermentation  can  readily  be 
cultivated  in  paste,  but  this  is  not  the  case  with  yeasts  little  active  in  alco- 
holic fermentation,  nor  with  the  bacteria,  a,  b,  c.  The  yeasts  can  be  culti- 
vated in  paste  containing  0*3  per  cent,  of  tartaric  acid,  but  this  quantity 
of  acid  completely  prevents  the  rising  of  paste  to  which  no  leaven  has  been 
added,  a result  which  shows  that  the  yeast  is  the  essential  agent  in  bread 
fermentation,  and  if  the  bacteria  play  any  useful  part,  it  is  only  in  the  pro- 
duction of  the  sugar.  Flour  charged  with  its  natural  microbes,  mixed 
with  salt  and  water  and  pure  yeast,  and  allowed  to  rise,  contains  practically 
the  same  proportions  of  gluten  as  the  original  flour,  and  hence  the  fermenta- 
tion of  the  gluten  is  not  essential,  but  is  a perturbation.  Starch  also  is  not 
affected  to  any  great  fextent  during  the  process.  An  aqueous  extract  of 
bran,  freed  from  bacteria,  saccharifies  starch  paste,  but  not  crude  starch, 
and  this  is  true  also  of  the  amylose  secreted  by  the  bacillus  a.  No  other 
fermentable  material  remains  but  the  soluble  part  of  the  flour  containing 
the  preformed  sugar,  dextrin,  and  salts.  Boutroux  concludes  that  bread 
fermentation  consists  essentially  of  the  alcoholic  fermentation  of  the  sugar 
pre-existing  in  the  flour.  The  yeast  not  only  produces  the  gas  which 
aerates  the  bread,  but  it  also  prevents  the  development  of  bacteria.  The 
difficulty  of  detecting  the  yeast  in  the  paste  arises  from  the  intimate  manner 
in  which  it  is  mixed  up  with  the  dough,  but  the  presence  of  the  yeast  cells 
is  more  readily  recognised  than  the  presence  of  bacteria. 

Laurent  regarded  leaven  fermentation  as  being  due  to  the  so-called 
Bacillus  panificans.  Peters  found  a number  of  yeasts  in  leaven,  and  several 
species  of  bacteria,  none  however  of  which  agreed  with  Laurent’s  Baccilus 
panificans,  but  rather  shared  the  properties  of  this  so-called  organism 
between  them.  Laurent  most  probably  was  dealing  with  an  impure  culti- 
vation. Peters  found  that  these  bacteria  gave  no  alcoholic  fermentation, 
and  no  appreciable  evolution  of  gas  in  sterilised  dough. 

599.  Alcohol  in  Bread,  Proof  of  Presence  of. — Pohl  determined  the  quan- 
tity of  alcohol  in  bread  in  the  following  manner  : — A Papin’s  digester  of 
about  8 litres  capacity  was  fitted  to  a Liebig  condenser.  Into  this  was 
placed  a charge  of  2 litres  of  water  and  990  grams  of  bread  cut  up  into  small 
cubes.  On  distillation  there  was  obtained  about  500  c.c.  of  distillate, 
having  a strong  odour  of  new  bread.  The  liquid  had  an  acid  reaction  and 
required  1*15  c.c.  of  normal  potassium  hydroxide  solution  for  neutralisa- 
tion. The  united  distillates  from  four  charges  of  the  apparatus  amounted 
to  about  2 litres,  and  represented  4,419  grams  of  bread.  The  distillate 
was  saturated  with  sodium  chloride  and  re-distilled  in  a flask  fitted  with  a 
fractionating  (Hempel)  still-head,  until  half  the  volume  had  come  over. 
The  re-distillate  was  again  saturated  with  sodium  chloride  and  re-distilled 
until  again  half  its  volume  had  come  over.  This  operation  was  repeated 
until  a distillate  having  a volume  of  120  c.c.  was  obtained.  This  was  then 
saturated  with  calcium  chloride  and  distilled  until  50  c.c.  had  come  over. 
The  specific  gravity  of  this  final  distillate  was  0 *9885,  and  corresponded  to 
6*66  grams  of  alcohol  in  100  c.c.,  so  that  100  grams  of  bread  contained  0 0753 
gram  of  alcohol.  (Z.  angew,  Chem,,  1906, 19,  668.) 

600.  Methods  of  Aerating  Bread  other  than  by  Yeast. — Carbon  dioxide 
is  not  only  produced  by  alcoholic  fermentation,  but  may  also  be  generated 
within  dough  by  purely  chemical  means,  or  may  be  mechanically  intro- 
duced by  first  effecting  its  solution  in  water.  The  following  description 
applies  to  aerating  agents  used  for  confectionery  as  well  as  bread-making 
purposes. 


464 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


601.  Aerating  Agents.— These  essentially  con«iist  of  (1)  substances  con- 
taining carbon  dioxide  in  a loosely  combined  condition,  as  in  certain  car- 
bonates, and  (2)  of  acids  or  acid-containing  bodies  which  liberate  the  carbon 
dioxide  from  the  members  of  the  first  group.  The  following  is  a description 
of  the  more  important  of  these  bodies. 

Sodium  bicarbonate,  NaHCOa.— This  body  evolves  carbon  dioxide  gas 
on  the  application  of  heat  alone,  thus  : — 

2NaHC03  = CO2  + Na^COs  -f-  H2O. 

Sodium  Bicarbonate.  Carbon  Dioxide.  Sodium  Carbonate.  Water. 

The  reaction  leaves  a residue  of  normal  sodium  carbonate,  which  has  a 
very  marked  and  disagreeable  alkaline  taste.  A very  slight  excess  causes  a 
yellowness  in  fiour  and  an  objectionable  smell.  These  qualities  are  em- 
phasised where  there  are  lumps  of  the  bicarbonate  not  properly  broken 
down,  or  when  there  is  imperfect  mixing. 

On  treatment  with  acids,  the  bicarbonate  evolves  double  the  quantity 
of  carbon  dioxide  gas  : — 

NaHCOs  + HCl  = CO2  + NaCl  + H2O. 

Sodium  Hydrochloric  Carbon  Sodium  Water. 

Bicarbonate.  Acid.  Dioxide.  Chloride. 

With  the  use  of  hj^drochloric  acid  as  in  this  case  the  residual  body  is 
sodium  chloride  or  common  salt.  These  bodies  are  at  times  used  in  the 
aeration  of  whole-meal  bread.  The  salt  produced  takes  the  place  in  whole 
or  in  part  of  that  always  added  for  flavouring  purposes. 

Ammonium  carbonate  (“  Volatile  ”). — Under  the  name  of  “ Volatile,'’ 
the  commercial  ammonium  carbonate  is  also  sometimes  used  as  a source  of 
carbon  dioxide  gas.  This  body  is  really  a mixture  of  ammonium  carbonate 
and  carbamate,  and  may  be  represented  by  the  formula  2(NH4)2C03.C02, 
and  contains  in  100  parts,  NH3,  28*81  ; CO2,  55*93  ; and  H2O,  15*26.  On 
being  dissolved  in  water  and  heated,  the  normal  carbonate  is  first  formed 
with  the  liberation  of  carbon  dioxide,  after  which  the  whole  of  the  carbonate 
completely  volatilises,  being  converted  into  gaseous  ammonia  and  carbon 
dioxide  : — 


2(NH4)2C03.C02 
Commercial  Ammonium 
Carbonate. 


2(NH4)2C03  + COj. 

Xormal  Ammonium.  Carbon  Dioxide. 

Carbonate. 


2(NH4)2C03  = 4NH3  + 2H2O  + 2CO2. 

Ammonium  Carbonate.  Ammonia.  Water.  Carbon  Dioxide. 

On  being  heated,  therefore,  the  whole  of  the  carbonate  is  converted 
into  gaseous  products. 

This  residue  is  therefore  entirely  gaseous,  and  consists  of  carbon  dioxide 
and  ammonia.  Until  the  latter  gas  leaves  the  goods  in  which  “ volatile  " 
has  been  used,  they  have  the  disagreeable  odour  and  flavour  of  ammonia. 
This  substance  is  mostly  used  for  aerating  small  porous  articles  which 
readily  permit  its  escape.  It  is  obviously  not  suited  for  the  aeration  of 
bread. 

Tartaric  Acid,  H2C4H4O6. — This  acid,  of  which  a description  has  already 
been  given,  is  very  soluble  in  water,  hot  or  cold,  and  acts  immediately  on 
sodium  bicarbonate  in  the  cold,  liberating  carbon  dioxide  : — 

H2C4H4O6  + 2NaHC03  - 2CO2  + Na2C4H406'  + 2H2O. 

Tartaric  Sodium  Carbon  Sodium  Water. 

Acid.  Bicarbonate.  Dioxide.  Tartrate. 

The  residual  body  is  sodium  tartrate  ; it  is  soluble  and  has  a bland  and 
faintly  saline  taste,  which  is  practically  imperceptible  in  the  baked  goods. 
Commercial  tartaric  acid  may  now  be  obtained  almost  chemically  pure. 

Cream  of  Tartar,  KHC4H4O6. — This  body,  known  also  as  hydrogen 


BREAD-MAKING. 


465 


potassium  tartrate,  is  tartaric  acid  with  half  its  acid  properties  neutralised 
by  combination  with  potassium  Consequently  it  has  only  half  the  strength 
of  tartaric  acid.  Cream  of  tartar  differs  remarkably  from  tartaric  acid  in 
that  it  is  only  very  slightly  soluble  in  cold  water,  whereas  it  is  readily  soluble 
in  hot  water.  The  result  of  this  is  that  when  cream  of  tartar  is  used  vlth 
sodium  bicarbonate  very  little  action  goes  on  in  the  cold.  But  when  the 
goods  get  hot  in  the  oven  a very  rapid  and  energetic  evolution  of  gas  occurs 
just  at  the  time  when  it  is  wanted.  For  this  reason  cream  of  tartar  is  an 
exceedingly  useful  bndy  to  the  baker  and  confectioner.  Its  chemical  action 
is  shoAvn  by  the  following  equation  : — 

KHC4H4O6  + NaHCOs  = CO2  -1-  KNaC4H406  + H2O. 

Cream  of  Sodium  Carbon  Potassium  Water. 

Tartar.  Bicarbonate.  Dioxide.  Sodium  Tartrate. 

The  residual  body  is  potassium  sodium  tartrate,  known  commercially 
as  “ Rochelle  Salts,’"  which  like  sodium  tartrate  is  possessed  of  very  little 
taste.  Both  sodium  tartrate  and  Rochelle  salts  are  aperient  bodies,  the 
latter  being  the  active  ingredient  in  the  well-knowm  Seidlitz  powders. 
For  the  same  amount  of  gas  evolved,  cream  of  tartar  leaves  double  the  resi- 
due in  the  goods  that  is  left  with  tartaric  acid.  Commercial  cream  of  tartar 
differs  very  much  in  its  degree  of  purity.  It  can,  however,  be  bought 
with  a guarantee  of  containing  98  per  cent,  of  the  pure  substance  ; and 
this  no  doubt  is  the  best  form  in  which  to  buy  the  salt  for  aerating  purposes. 

Acid  Calcium  Phosphate,  CaH4(P04)2. — This  salt  is  used  to  a consider- 
able extent  for  aerating  purposes.  It  is  soluble  in  cold  water,  and  therefore 
behaves  somewhat  similarly  to  tartaric  acid.  In  view  of  the  fact  that 
there  is  a number  of  possible  phosphates,  several  reactions  may  occur  be- 
tween this  body  and  sodium  bicarbonate.  The  following  are  among  the 
most  important: — 

CaH4(P04)2  + 2NaHC03  - 2CO2  + CaNa2H2(P04)2  + 2H2O. 

Acid  Calcuim  Sodium  Carbon  Calcuim  Di-sodium  Water. 

Phosphate.  Bicarbonate.  Dioxide.  Di-hydrogen  Phosphate. 

CaH4(P04)2  + NaHCOs  = CO2  + CaNaHsiPO.ia  + HjO. 

Acid  Calcium  Sodium  Carbon  Calcium  Sodium  Water. 

Phosphate.  Bicarbonate.  Dioxide.  Trihydrogen  Phosphate. 

In  the  former  of  the  above  equations,  one  molecule  of  acid  calcium 

phosphate  has  reacted  with  two  molecules  of  bicarbonate,  and  has  liberated 

two  molecules  of  carbon  dioxide.  Mixed  in  these  proportions  the  resultant 
phosphate,  though  still  containing  acid  hydrogen,  is  neutral  to  litmus. 
Notwithstanding  this,  the  alkali  is  still  in  excess  so  far  as  the  taste  is  con- 
cerned, and  if  the  acid  salt  and  the  bicarbonate  be  used  in  these  propor- 
tionate quantities,  the  bread  or  other  goods  will  have  an  objectionable  soda 
taste.  One  molecule  of  the  acid  salt  to  two  molecules  of  bicarbonate  is 
equivalent  to  a proportion  by  weight  of  13*9  parts  of  acid  salt  to  10  parts  of 
bicarbonate.  If  used  according  to  the  second  equation,  that  is,  one  mole- 
cule each  of  acid  salt  and  bicarbonate,  there  is  one  molecule  only  of  carbon- 
dioxide  evolved,  and  the  residual  phosphate  is  acid  both  to  litmus  and  the 
taste.  They  are  then  in  the  proportions  by  weight  of  27  *8  parts  of  acid 
salt  to  10  parts  of  bicarbonate,  and  the  acid  salt  is  in  considerable  excess. 
On  making  a series  of  tests  with  the  acid  phosphate  and  bicarbonate  in 
varying  proportions  in  bread  doughs,  it  was  found  necessary  to  use  22*5 
parts  of  the  acid  phosphate  to  10  parts  of  the  bicarbonate  in  order  to  obtain 
bread  which  was  free  from  the  objectionable  taste  of  soda.  To  the  10  parts 
of  bicarbonate,  13*9  parts  of  acid  calcium  phosphate  suffice  to  liberate 
all  the  carbon  dioxide  present  : it  is  necessary  to  use  the  excess  up  to  about 
22*5  parts  in  order  to  neutralise  the  soda  taste.  These  proportions  do  not 
agree  with  any  simple  number  of  molecules  of  the  two  bodies.  Much  of 

H H 


466 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


the  acid  calcium  phosphate  on  the  market  is  exceedingly  impure,  some 
samples  containing  as  much  as  50  per  cent,  of  calcium  sulphate.  It  can, 
however,  be  bought  from  the  best  makers  with  a guarantee  of  98  per  cent, 
pure  phosphate. 

Acid  Potassium  Phosphate,  KH2PO4. — The  potassium  salt  has  been, 
and  still  is  at  times,  employed  instead  of  that  of  calcium.  The  reaction 
between  it  and  sodium  bicarbonate  is  as  follows  : — 

KH2PO4  + NaHCOa  =-  CO2  + KNaHP04  + H2O. 

Acid  Potassium  Sodium  Carbon  Potassium  Sodium  Water. 

Phosphate.  Bicarbonate.  Dioxide.  Hydrogen  Phosphate. 

The  resultant  potassium  sodium  hydrogen  phosphate  is  neutral  to  lit- 
mus but  alkaline  to  taste,  and  in  practice  about  three  molecules  of  acid 
potassium  phosphate  to  two  molecules  of  sodium  bicarbonate  are  found 
necessary.  There  seems  to  be  no  advantage  in  having  a residue  of  potassium 
phosphate  rather  than  calcium  phosphate  in  the  goods,  provided  that  the, 
calcium  phosphate  used  is  commercially  pure. 

Acid  Potassium  Sulphate,  KHSO4. — This  salt  is  soluble  in  cold  water 
and  acts  similarly  to  tartaric  acid  when  used  as  an  aerating  agent.  It  is 
much  the  cheaper  of  the  two  and  produces  the  following  change  with  sodium 
bicarbonate  : — 

KHSO4  + NaHCOs  = CO2  + KNaS04  + H2O. 

, Acid  Potassium  Sodium  Carbon  Potassium  Sodium  Water. 

Sulphate.  Bicarbonate.  Dioxide.  Sulphate. 

The  residual  potassium  sodium  sulphate  is  a comparatively  tasteless 
body  Avith  aperient  properties. 

“ Cream  Substitutes.”' — These  substances  are  lower  in  price  than  cream 
of  tartar,  and  mostly  consist  of  acid  phosphates  or  sulphates,  or  mixtures 
of  the  two.  The  acid  strength  is  let  down  to  that  of  cream  of  tartar  by 
the  addition  of  starch,  usually  in  the  form  of  rice  or  cornflour.  Strictly, 
these  bodies  are  not  substitutes  for  cream  of  tartar  as  they  do  not  possess 
the  same  property  of  insolubility  in  cold  water,  and  ready  solubility  in  hot 
water.  By  careful  selection  and  admixture,  their  rate  of  cold  Avater  solu- 
bility is  considerably  sloAA^ed  doAvn,  and  AAuthin  limits  they  can  be  used 
instead  of  cream  of  tartar.  Their  true  analogue  is  not,  however,  cream  of 
tartar,  but  rather  tartaric  acid. 

Alum,  Al2K2(S04)4,  24H2O. — The  alums  liberate  carbon  dioxide  from 
sodium  bicarbonate  according  to  the  folloAA'ing  equation  : — 

AI2K2  (804)4, 24HO2  + ANaHCOa  = 6CO2  + Al2(HO)6  + 

Potash  Alum.  Sodium  Bicarbonate.  Carbon  Dioxide.  Aluminium  Hydroxide. 

K2SO4  + SNa^SOi  + 24H2O. 

Potassium  Sodium  AA’’ater. 

Sulphate.  Sulphate. 

The  employment  of  alum  in  the  preparation  of  food  is  regarded  as  an 
adulteration. 

Equivalent  Weights. — The  folloAving  table  gives  the  AA^eight  of  each  sub- 
stance required  by  10  parts  by  AA  eight  of  sodium  bicarbonate  : — 


Name. 

Tartaric  j Acid 

Weight. 

8-93 

Cream  of  Tartar  . . 

. . 22-38 

Acid  Calcium  Phosphate,  about 

. . 22*50 

Acid  Potassium  Sulpliate 

. . 16*19 

Comparative  Evolution  of  Gas. — The  comparative  volume  of  gas,  mea- 
sured at  100°  C.,  evolved  by  one  part  by  AA^eight  (1  gram)  of  various  aerating 
mixtures,  is  given  in  cubic  centimetres  in  the  folio AAing  table  : — 


BREAD-MAKING. 


467 


NAME  OF  AERATING  AGENT.  VOLUME. 

Ammonium  carbonate  (volatile),  on  being  heated  yields — ammonia  gas, 

516;  carbon  dioxide  gas,  387  ..  ..  ..  ..  ..  903 

Sodium  bicarbonate  by  action  of  heat  alone  . . . . . . . . 181 

Mixture  in  proportion  of  10  parts  sodium  bicarbonate  to  8-93  parts 

tartaric  acid  . . . . . . . . . . . . . . . . 191 

Mixture  in  proportion  of  10  parts  sodium  bicarbonate  to  22  *38  parts 

cream  of  tartar  . . . . . . . . . . . . . . 112 

Mixture  in  proportion  of  10  parts  sodium  bicarbonate  to  22*5  parts  acid 

calcipm  phosphate  . . . . . . . . . . . . . . 112 

Mixture  in  proportion  of  10  parts  sodium  bicarbonate  to  16*19  parts  acid 

potassium  sulphate  . . . . . . . . . . . . . . 138 

In  summing  up  the  general  behaviour  of  these,  and  deciding  as  to  their 
suitability  for  aerating  purposes,  the  first  consideration  is  whether  rapidity 
of  action  is  objectionable  or  otherwise.  If  the  goods  can  be  baked  at  once 
before  the  action  of  the  acid  and  soda  on  each  other  is  over,  then  tartaric 
acid  and  soda  answer  well.  But  it  must  be  remembered  that  this  action 
commences  immediately  the  ingredients  are  wetted.  On  the  other  hand, 
if  it  be  desired  that  no  action  shall  occur  before  the  goods  are  heated  in  the 
oven,  then  cream  of  tartar  and  soda  are  preferable,  as  this  mixture  remains 
quiescent  until  the  temperature  is  raised.  Where  immediate  action  is  no 
detriment,  acid  and  soda  are  indicated,  and  this  mixture  possesses  the 
advantage  of  leaving  only  about  half  the  residue  left  by  cream  of  tartar  and 
soda.  Ammonium  carbonate  has  also  a deferred  action,  but  there  is  the 
unpleasant  ammoniacal  odour  left  in  the  hot  baked  goods.  Provided  this 
is  allowed  to  escape,  and  the  goods  are  odourless,  then  no  residue  whatever 
remains  in  them. 


602.  Baking  Powders. — These  consist  of  bicarbonate  of  soda  put  up 
with  one  or  more  of  the  acid  bodies  previously  described.  Baking  powders 
are  used  more  extensively  in  America  than  this  country  for  bread-making^ 
purposes,  and  their  composition  has  been  made  the  subject  of  investigation 
by  one  of  the  State  departments.  They  are  classified  according  to  the 
nature  of  the  acid  constituent  they  contain  into  three  groups.  Tartrate. 
Phosphate,  and  Alum  powders. 

In  the  manufacture  of  baking  powders,  the  acid  ingredient,  together 
with  the  proportionate  quantity  of  bicarbonate  of  soda,  is  mixed  with  air- 
dried  starch.  This  latter  component  increases  the  weight  of  the  baking 
powder  ; it  also,  owing  to  the  hygroscopic  nature  of  starch,  helps  to  keep 
the  active  ingredients  free  from  moisture. 


603.  Effect  of  Alum  on  Bread. — The  action  of  alum  in  bread  on  its 
artificial  digestion  was  demonstrated  by  a number  of  experiments  made  by 
Knights,  and  communicated  to  the  Society  of  Public  Analysts  in  1880. 
Hehner  has  since  (in  November,  1892)  published  the  results  of  researches 
on  the  effect  on  artificial  digestion  of  alumed  baking  powders.  The  baking 
powMer  used  had  the  composition  : — 

Crystallised  Alum  . . . . . . . . ..  45*80 

Sodium  Bicarbonate  . . . . . . . . . . 18*71 

Starch  33*40 

Moisture,  and  not  determined..  ..  ..  ..  2*06 


100*00 

Using  the  directions  given  with  the  wrapper,  this  powder,  if  employed  for 
bread-making,  would  yield  a 4-lb.  loaf  containing  210  grains  of  alum.  On 
treating  hard-boiled  white  of  egg  with  pepsin  solution,  the  addition  of  the 


468 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


alum  baking  powder,  and  also  pure  alum  to  the  same  extent  as  the  baking 
powder  contained,  both  equally  retarded  digestion. 

There  were  next  some  experiments  made  on  flour  ; and  with  this,  while 
alum  has  a most  injurious  influence  upon  the  digestion,  that  of  alumed 
baking  powder  is  but  slight.  With  bread  a series  of  experiments  was  made, 
in  which  pure  bread  was  digested  with  pepsin  solution  and  alumed  baking 
powder  and  alum  respectively  ; with  amounts  of  baking  powder  recom- 
mended to  be  taken  by  the  manufacturer,  the  influence  of  alum  and  of 
alumed  baking  powder  is  about  equal,  both  producing  very  marked  retard- 
ing action.  A physiological  experiment,  in  which  four  persons  took  each 
a dose  of  baking  powder  dissolved  in  water  and  then  sweetened,  was  made. 
The  amount  so  taken  was  2 grams,  equal  to  that  contained  in  4 ounces  of 
bread  made  according  to  manufacturers"  directions — the  resultant  symp- 
toms were  those  resembling  an  attack  of  indigestion,  being  slight  difficulty 
in  breathing,  headache,  and  ultimately  slight  diarrhoea,  which  symptoms 
lasted  for  several  days. 

Subsequently  to  this,  in  1893,  a case  of  prosecution  for  the  sale  of  alumed 
baking  powder  came  before  the  Glamorganshire  Quarter  Sessions.  Among 
other  evidence  given  there  was  that  of  the  scientific  witnesses,  of  wLich 
the  following  is  a summary  : — 

Morgan,  Public  Analyst,  stated  that  a 4-lb.  loaf  made  according  to  direc- 
tions given  would  contain  360  grains  of  baking  powMer,  of  which  144  grains 
w'ere  alum.  On  addition  of  water  to  the  baking  powder  a reaction  occurs, 
in  wiiich  potash-alum  and  sodium-bicarbonate  produce  aluminium  hydroxide 
sodium  sulphate,  potassium  sulphate,  carbon  dioxide  gas,  and  water.  The 
quantity  of  aluminium  hydroxide  might  be  taken  as  one-sixth  of  the  alum, 
or  24  grains  to  the  4-lb.  loaf.  On  being  eaten,  the  hydrochloric  acid  and 
pepsin  of  the  gastric  juice  dissolved  the  aluminium  hydroxide  with  formation 
of  soluble  aluminium  chloride,  which  latter  body  was  noxious  to  the  stomach. 
Aluminium  hydroxide  was  prepared  from  this  baking  powMer,  mixed  with 
w^ater,  and  taken  with  a mid-day  meal.  At  the  same  meal  another  person 
drank  nothing.  Artificial  vomiting  was  shortly  afterwards  in  both  cases 
induced,  and  hydroxide  of  alumina  added  to  the  contents  of  the  stomach 
in  the  case  of  the  subject  wflio  had  drunk  nothing.  Both  vomits  w^ere  then 
dialysed,  and  aluminium  chloride  found  in  each,  thus  showing  that  the 
hydroxide  of  alumina  had  been  converted  to  the  soluble  form. 

Dunstan  stated  that  aluminium  hydroxide  dried  at  212°  F.  w^as  soluble 
in  the  diluted  gastric  juice  of  a dog  ; and,  further,  that  such  gastric  juice 
dissolved  aluminium  hydroxide  from  bread  baked  with  the  powder.  Fur- 
ther, aluminium  hydroxide  dried  at  212°F.  was  soluble  in  a dilute  solution 
of  sodium  carbonate  of  0*3  per  cent,  strength,  the  strength  of  the  alkali  in 
intestinal  juice.  He  consequently  found  that  this  alumed  baking  powder 
interfered  with  the  digestion  of  starch  by  ptyalin,  and  also  with  peptic  and 
pancreatic  digestion.  Hehner,  Lauder  Brunton,  and  others  gave  corrobora- 
tive evidence. 

The  line  of  defence  w^as  that  the  preceding  evidence  had  not  shown  that 
the  baking  powMer  w'as  injurious  to  health,  but  only  that  it  might  be.  Among 
witnesses  called  for  the  defence  was  Sutton,  wiio  described  an  experiment 
lie  had  made,  in  which  a coachman  ate  a pound  of  bread  made  with  the- 
baking  powder,  and  about  two  hours  after  had  the  contents  of  his  stomach 
removed  ; these  w^ere  subjected  to  dialysis,  and  found  to  contain  no  alu- 
minium chloride.  Luff  and  Wynter  Blyth,  wiio  were  also  present  at  this 
experiment,  concurred  with  Sutton  ; they  all  considered  aluminium  hydroxide 
to  be  insoluble  under  the  conditions  of  bread  digestion  in  the  human  stom- 
ach, and  viewed  Morgan"s  experiments  as  valueless,  because  feebly  precipita- 
ted aluminium  hydroxide  w'as  much  more  soluble  than  alumin.'um  hydroxide 


BREAD-MAKING. 


469 


baked  in  a state  of  actual  dissemination  through  a loaf  of  bread.  B,  Ward 
Richardson  followed  on  the  same  side,  and  was  of  opinion  that  the  use  of 
alumed  baking  powder  was  not  injurious  to  health.  Wynter  Blyth  con- 
sidered that  Morgan’s  aluminium  hydroxide  was  not  in  the  same  condition  as 
that  of  aluminium  hydroxide  baked  in  bread  ; and,  further,  that  alumed 
baking  powder  was  not  injurious  to  health. 

The  decision  of  the  Court  was  that  the  baking  powder  was  mixed  with 
a certain  ingredient,  to  wit,  alum,  which  is  injurious  to  health,  and  therefore 
file  conviction  of  the  person  selling  the  same  was  upheld. 

Very  considerable  difference  of  opinion  was  expressed  during  the  giving 
of  the  above  cited  evidence  as  to  the  condition  of  the  aluminium  hydroxide 
and  its  behaviour  in  the  stomach.  Of  all  experiments  that  of  Sutton  was  far 
the  most  conclusive,  because  of  being  made  on  bread  manufactured  with  the 
powder.  The  separate  addition  of  alum  or  alumed  baking  powder  to  pure 
bread  undergoing  artificial  digestion,  or  to  the  contents  of  the  stomach, 
involves  conditions  so  distinct  from  those  which  hold  in  the  actual  use  of 
alumed  baking  powder  that  comparatively  little  importance  can  be  attached 
to  the  results,  whatever  they  may  be. , The  obvious  course  would  be  to  arti- 
ficially digest  bread  prepared  from  alumed  baking  powder  against  breads 
prepared  with  and  without  admixture  of  alum  ; and  in  case  of  human 
digestion,  to  also  experiment  in  the  same  manner  as  Sutton  with  the  pre- 
pared bread. 

To  throw  additional  light  on  this  matter,  the  authors  made  the  following 
series  of  experiments  : — Three  loaves  of  bread  were  prepared  from,  in  each 
case  2 lbs.  3 oz.  of  flour,  1 lb.  8 oz.  of  water,  1 oz.  of  yeast,  and  | oz.  of  salt. 
At  the  time  of  mixing  there  was  also  added  to  No.  1,  9*35  grams  of  alum  ; 
and  to  No.  2,  9*35  grams  of  alum  and  4*80  grams  of  sodium  bicarbonate  ; 
No.  3 was  left  plain.  The  total  proteins  in  each  were  determined,  and  a 
portion  of  the  bread  subjected  to  artificial  digestion  mth  pepsin,  the  follow- 
ing being  the  method  adopted  : — 5 grams  of  the  bread  were  taken  and  rubbed 
down  in  a mortar  with  25  c.c.  of  0*01  per  cent,  solution  of  pepsin  in  0*2  per 
cent,  hydrochloric  acid,  then  made  up  to  100  c.c.  with  water,  and  digested 
1 J hours  at  43*5°  C.  The  solution  was  filtered,  and  the  amount  of  digested 
protein  determined  in  the  filtrate.  The  comparative  starch  digestion  was 
estimated  by  rubbing  do^vn  5 grams  of  bread  in  a solution  of  malt  diastase, 
making  up  to  100  c.c.,  and  digesting  at  21°  C.  for  one  hour.  Maltose  was 
then  determined  in  the  filtrate  from  each.  The  following  are  the  results 
of  analysis  in  percentages : — 


1. 

Alum. 

2. 

Alum  and 
Bicarbonate. 

3. 

Plain. 

Total  Proteins  before  digestion 

8T5 

7*95 

8*20 

Proteins  digested . . 

Maltose  found,  being  evidence  of  diges- 

1*99 

1*95 

3*83 

tion  of  starch  . . 

36*36 

41*34 

43*6 

Other  series  of  experiments  were  made,  in  which  the  same  general  results 
were  obtained.  The  quantity  of  alum  present,  under  the  conditions  of  the 
experiment,  retarded  protein  digestion  to  about  half  the  rate  in  its  absence. 
Practically  no  difference  was  made  in  this  retarding  action  by  the  presence 
of  sodium  bicarbonate  : in  other  words,  the  alumed  baking  powder  was 
equally  injurious  with  alum  used  alone.  The  difference  in  amount  of  starch 
digestion  was  not  so  marked  as  probably  it  would  have  been  had  a diastase 
solution  of  less  strength  been  used.  There  is  a marked  difference  between 
the  alumed  and  the  plain  loaf,  but  in  this  case  the  retarding  action  of  alum 
is  largely  overcome  by  the  presence  of  bicarbonate  in  No.  2,  a result,  doubt- 
less, of  the  neutralising  effect  of  the  alkaline  salt  on  the  alum. 


470 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


604.  Self-Raising  Flour. — The  articles  sold  under  this  name  consist  of 
flour,  mixed  with  acid  tartrates  or  phosphates,  and  the  bicarbonate  of  soda  : 
as  with  baking  powder,  the  addition  of  water  causes  the  evolution  of  gas. 
Self-raising  flours  may  be  viewed  as  being  flours  sold  with  baking  powder 
already  mixed  with  them.  It  is  claimed  for  the  use  of  phosphates  in  this 
manner  that  it  replaces  these  important  salts  which  are  removed  from  the 
wheat  in  the  bran. 

605.  Use  of  Hydrochloric  Acid. — In  the  manufacture  of  wholemeal  bread 
the  method  is  sometimes  adopted  of  employing  hydrochloric  acid  and  so- 
dium carbonate  in  the  exact  proportions  in  which  they  neutralise  each  other  : 
they  then  not  only  evolve  carbon  dioxide  gas,  but  also  yield  sodium  chloride, 
or  common  salt,  thus  ; — 

NaHCOa  + HCl  = NaCl  + H2O  + CO^. 

Sodium  Hydrochloric  Sodium  Water.  Carbon 

Bicarbonate.  Acid.  Chloride.  Dioxide. 

The  salt  thus  formed  lessens  the  quantity  which  otherwise  would  have 
to  be  added  to  the  bread.  Great  care  is  requisite  in  the  proper  mixing 
of  the  acid  and  the  carbonate  with  the  meal  : it  is  also  important  that  ex- 
actly the  right  proportions  should  be  taken.  A rough  measurement  of  the 
strength  of  the  acid  may  be  made  by  taking  a weighed  quantity,  say  an 
ounce,  of  the  bicarbonate  of  soda,  dissolving  it  in  boiling  water  in  a beaker, 
and  then  adding  a few  drops  of  methyl  orange  solution.  The  hydrochloric 
acid  should  be  measured,  or  else  a quantity  placed  in  a beaker,  and  weighed 
in  it  : then  add  the  acid  little  by  little  until  one  drop  changes  the  colour  of 
the  bicarbonate  of  soda  solution  from  yellow  to  red.  Then  again  weigh 
the  acid  containing  beaker  ; the  loss  in  weight  gives  the  quantity  of  the 
hydrochloric  acid,  equivalent  to  an  ounce  of  the  bicarbonate.  Commerial 
hydrochloric  acid  is  usually  sold  with  a guaranteed  density  of  1*15  ; this 
is  equivalent  to  about  30  per  cent,  of  the  anhydrous  acid.  As  84  parts  of 
sodium  bicarbonate  are  exactly  neutralised  by  36*5  of  anhydrous  hydro- 
chloric acid,  and  as  this  amount  is  contained  in  122  parts  of  the  commercial 
acid,  the  bicarbonate  of  soda  and  hydrochloric  acid  of  this  density  should 
be  used  in  the  proportions  of  84  of  the  bicarbonate  to  122  of  the  acid,  or 
practically  in  the  proportions  of  2 to  3 by  weight.  It  has  been  recommended 
that  3 lbs.  each  of  the  acid  and  bicarbonate  be  used  to  the  sack  of  flour  : 
these  proportions  leave,  however,  a considerable  excess  of  the  carbonate 
in  the  bread.  The  great  objection  to  the  hydrochloric  acid  method  is  that 
the  commerical  acid  frequently  contains  traces  of  arsenic,  and  thus  a minute 
quantity  finds  its  way  into  the  loaf. 

606.  Whole-Meal  Bread. — It  is  principally  in  making  whole-meal  bread 
that  the  hydrochloric  .acid  and  bicarbonate  method  is  employed.  The  rea- 
son is  that,  with  the  presence  of  the  bran,  cerealin  is  introduced  into  the 
dough  in  such  quantity  that,  if  ordinary  fermentation  processes  be  em- 
ployed, diastasis  proceeds  to  a very  serious  extent.  The  excess  of  dextrin 
thus  produced  causes  the  dough  to  become  soft  and  clammy,  and  so  to 
offer  a matrix  in  which  sour  and  other  unhealthy  fermentations  are  apt  to 
proceed  rapidly.  The  brown  colour  is  due  to  the  excess  of  dextrinous 
matter  contained  in  the  bread.  The  rapidity  of  the  acid  treatment  en- 
ables the  bread  to  be  got  into  the  oven  before  diastatic  action  can  have 
proceeded  to  any  extent.  When  the  fermentation  method  is  employed 
for  making  whole-meal  bread,  it  is  customary  to  make  a sponge  with  a 
small  quantity  of  very  strong  flour,  and  only  add  the  whole  meal  at  the 
dough  stage.  How^ever  made,  wLole-meal  bread  has  a great  tendency 
to  become  sodden  ; in  order  to  drive  off  excess  of  moisture  it  has  to  be 
baked  for  a considerable  time,  consequently  the  loaf  has  often  a very  thick 


BREAD-MAKING. 


471 


crust,  wliile  the  interior  is  still  unduly  moist.  In  summer  time  particularly 
the  making  of  whole-meal  bread  is  an  unsatisfactory  operation,  as  great 
difficulty  is  often  experienced  in  producing  a sound  and  well-risen  loaf. 

In  all  the  operations  just  described,  carbon  dioxide  is  formed  in  dough, 
and  thus  raises  it.  The  chemical  action  which  under  these  circumstances 
takes  place  is  not,  however,  a complete  representative  of  that  which  occurs 
with  yeast.  One  of  the  functions  of  this  body  during  the  fermentation  of 
bread  is  to  act  on  the  protein,  and  also  to  a certain  extent  on  the  starch  ; 
the  result  of  such  action,  when  normal,  is  to  impart  to  the  bread  a charac- 
teristic flavour  that  can  be  obtained  by  no  other  means  at  present  known. 

607.  The  Aeration  Process. — One  other  method  of  aerating  bread  remains 
for  consideration,  and  that  is  the  system  associated  with  the  name  of  Dr. 
Dauglish.  The  carbon  dioxide  is  in  this  method  prepared  apart  from  the 
bread  and  forced  into  water  under  pressure  ; this  water,  which  is  akin  to  the 
aerated  water  sold  as  a beverage,  is  then  used  for  converting  the  flour  into 
dough,  the  whole  operation  of  kneading  being  performed  in  a specially 
prepared  vessel  in  which  the  pressure  is  maintained.  The  kneading 
being  completed,  the  dough  is  allowed  to  emerge  from  the  kneading  vessel, 
and  immediately  rises,  from  the  expansion  within  it  of  the  dissolved  carbon 
dioxide.  Such. was  the  nature  of  the  method  originally  employed  by  Daug- 
lish ; but  now  the  following  modification  is  used  : — A weak  wort  is  made  by 
mashing  malt  and  flour  ; this  is  allowed  to  ferment  until  through  the  agency 
of  bacteria  it  has  become  sour,  in  all  likelihood  through  the  presence  of  lactic 
acid.  The  w ater  to  be  aerated  is  first  mixed  with  a portion  of  this  w-eak 
acid  liquid  : it  is  then  found  to  absorb  the  carbon  dioxide  gas  much  more 
readily.  The  acid  also  softens  the  gluten.  So  far  as  the  actual  aeration 
process  is  concerned,  this  method  is  mechanical  rather  than  chemical.  The 
great  objection  is  that  those  more  subtle  changes  by  which  flavour  is  pro- 
duced do  not  occur  here  more  than  in  the  other  purely  chemical  methods  of 
bread- making  before  described.  A common  experience  in  eating  aerated 
bread  for  some  time  is  that  it  after  a wliile  gives  the  impression  of  rawmess. 
This  is  doubtless  due  to  there  being  no  such  enzymic  action  on  the  proteins 
as  results  from  fermentation.  It  is  partly  to  meet  this  want  that  the  fer- 
mented w ort  is  now  added  as  a part  of  the  process.  On  the  other  hand,  as 
a compensation  for  this  lack  of  flavour-producing  changes,  the  operation* 
is  one  in  which  there  is  no  danger  of  those  injurious  actions  occurring  of 
wliich  much  has  already  been  said.  .^Working  with  flours  that  are  w^eak 
and  damp,  or  even  bordering  on  the  verge  of  unsoundness,  it  is  still  possible 
to  produce  a loaf  that  should  be  wholesome  and  palatable,  certainly  superior 
to  many  sodden  and  sour  loaves  made  from  low  quality  flours  fermented  in 
the  ordinary  manner.  In  thus  stating  that  it  is  possible  to  treat  flours 
of  inferior  quality  by  this  aerating  method,  the  authors  wish  specially  to 
carefully  avoid  giving  the  impression  that  it  is  the  habit  of  those  companies 
wliich  w ork  Dauglish's  method  to  make  use  of  only  the  lower  qualities  of 
flour  ; they  have  never  had  any  reason  wliatever  for  supposing  such  to  be 
the  case.  Their  object  in  the  present  remarks  is  simply  to  point  out  the 
advantages  possessed  by  this  method,  should  circumstances  unfortunately 
arise  rendering  it  necessary  to  have  recourse  to  inferior  flours  for  bread- 
making purposes. 

Richardson  claims  for  the  aeration  process  that  it  is  eminently  suited 
for  the  manufacture  of  whole-meal  bread.  Of  this  there  is  not  the  slighest 
doubt  : wffiole-meal  is  not  w^ell  fitted  for  fermentation  methods,  and  the* 
aeration  process  distends  the  dough  with  gas,  without  the  addition  of  any 
foreign  substance  whatever. 

It  is  also  claimed  for  the  aeration  process  that  it  enables  the  cerealin 


472 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


to  be  retained  within  the  bread  ; and  that  this  is  “ a most  powerful  agent 
in  promoting  the  easy  and  healthy  digestion  of  food.’'  It  is  stated  that 
this  agent  is  retained  uninjured  by  the  aerated  bread  process.  The  author 
of  this  statement  apparently  overlooks  the  fact  that  diastatic  action  is 
destroyed  by  the  subjection  of  proteins  to  a temperature  approaching  212°  F. 
However  active,  therefore,  cerealin  may  be  in  effecting  diastasis  of  starch 
during  panary  fermentation,  its  power  is  destroyed  by  efficient  baking, 
and  the  bread  contains  no  active  disatatic  principle.  This  remark  applies 
with  equal  force  to  bread  containing  malt  ; it  is  so  well  known  that  malt 
infusion  converts  starch  into  dextrin  and  maltose,  that  from  time  to  time  it 
has  been  introduced  into  bread.  It  must  here,  too,  be  remembered  that  the 
baking  entirely  destroys  its  diastatic  action,  and  so  causes  the  malt  to  be 
inert  as  a digestive  substance. 


608.  Gluten  Bread. — It  is  important  that  the  diet  of  diabetic  patients 
should  contain  no  sugar,  starch,  or  other  compounds  capable  of  being  con- 
verted into  sugar.  For  their  use  bread  is  prepared  containing  the  gluten 
only  of  the  flour.  A strong  flour  should  be  selected  and  made  into  a stiff 
dough  with  water  only  ; this  is  allowed  to  stand  for  almost  "an  hour,  and 
then  carefully  kneaded  in  small  pieces  at  a time  in  a vessel  of  water  ; the 
starch  escapes  and  the  gluten  remains  behind.  Care  is  necessary  in  per- 
forming this  operation,  as  otherwise  the  lump  of  dough  does  not  hold  to- 
gether. Should  there  be  any  difficulty,  the  dough  may  be  enclosed  in  muslin 
prior  to  being  kneaded.  The  gluten  must  be  washed  in  successive  waters 
until  it  no  longer  contains  starch  ; at  this  point  the  gluten  ceases  to  render 
the  washing  water  milky.  When  properly  washed  the  gluten  is  ready  for  the 
oven,  and  is  usually  baked  in  small  rolls  or  buns.  As  it  swells  enormously 
during  baking,  a very  small  piece  is  sufficient  for  each  roll. 

609.  Rye  Bread. — On  the  Continent,  bread  is  made  to  a considerable 
extent  from  rye.  The  following  are  the  results  of  analyses  of  samples  of 
two  such  breads  : — 


Proteins 
Starch,  etc. 
Sugar 
Fat  . . 

Cellulose 
Mineral  matters 
Water 


Pumpernickel. 
Black  Bread. 

8-90 

39-74 

3-28 

2-09 

1-79 

1*29 

42-90 


Vienna 
Bye  Bread. 

8-30 

55-14 

1-46 

0-33 

0- 97 

1- 90 
31-91 


Pumpernickel  is  the  well-known  black  bread  of  Northern  Germany, 
and  is  regarded  rather  as  a delicacy,  being  almost  invariably  served  wdth 
cheese  in  the  hotels  of  Berlin  and  other  German  cities.  The  Vienna  sample 
is  of  a whiter  type,  containing  considerably  less  of  the  bran. 

610.  Unsuitability  of  Barley  Meal,  etc.,  for  Bread-making. — Questions 
often  arise  as  to  why  barley  and  other  cereals  do  not  make  such  good  bread 
as  does  wheaten  flour.  One  reason  has  already  been  given  : wffieat  is  dis- 
tinguished from  the  other  somewhat  similar  food  stuffs  by  its  containing 
gluten  ; it  is  the  presence  of  this  peculiar  albuminous  body  that  confers 
on  'wheat  flour  its  characteristic  bread-making  qualities.  The  proteins  of 
the  other  cereals,  and  also  of  peas  and  the  other  leguminous  seeds,  possess 
more  active  diastatic  properties — consequently  during  fermentation  they 
yield  much  dextrin,  and  produce  dark  coloured,  sodden,  and  often  sour 
breads.  The  diastase  of  rye  is  particularly  active.  In  addition  to  the 
colour  produced  by  diastasis,  peas  have  naturally  a dark  colour  of  their 


BREAD-MAKING. 


473 


■own,  so  that  their  introduction  into  bread  would  very  materially  affect  the 
■colour.  In  comparing  barley  and  rye  flours  against  that  of  wheat,  the 
differences  in  the  respective  milling  processes  must  not  be  ignored.  The 
bran  and  germ  of  wheat  are  separated  from  the  flour  by  most  refined  methods, 
while  barley  and  rye  are  ground,  and  the  meal  purified,  by  the  crudest 
appliances.  This  must  of  necessity  make  a difference  in  the  character  of 
the  flour. 

611’.  Wheat  and  Flour  Blending. — The  consideration  of  the  whole  pro- 
blem of  blending  flours  and  wheats  has  been  purposely  postponed  until 
this  stage,  in  order  that  the  reader  may  have  before  him  an  account  of  the 
various  changes  which  flour  undergoes  during  the  operations  of  panary 
fermentation.  These  changes,  in  short,  consist  in  more  or  less  conversion 
of  starch  into  dextrin  and  maltose,  and  in  the  gradual  softening  and  other- 
wise altering  the  gluten  of  the  flour.  As  has  been  previously  insisted  on, 
the  gluten  must  have  had  during  fermentation  sufficient  opportunity  to 
hydrate  and  soften  sufficiently  ; but  must  not  have  been  allowed  to  further 
change,  as  if  so  it  will  have  lost  its  tenacity,  and  vill  produce  an  inferior 
loaf.  A great  deal  of  the  success  of  a skilled  baker  depends  on  his  having 
acquired  the  experience  which  enables  him  to  take  his  dough  and  place 
it  in  the  oven  just  at  this  right  point  when  fermentation  has  proceeded 
sufficiently  far  to  get  the  gluten  of  the  flour  in  its  best  possible  condition. 

The  problem  is  further  complicated  by  the  fact  that  different  flours 
require,  in  order  to  arrive  at  this  stage  of  maturity,  different  lengths  of 
time  in  fermentation  ; hence,  as  already  explained,  flours  from  hard  wheats 
are  commonly  used  in  the  sponge,  while  those  from  soft  wheats  are  employed 
in  the  dough.  There  can  be  no  doubt  whatever  that  by  this  arrangement 
far  better  bread  is  produced  than  if  the  flours  be  used  in  the  reverse  order. 
It  is,  then,  perfectly  safe  to  state  that  the  length  of  time  flours  require  to  stand 
in  fermentation  is  in  proportion  to  their  hardness  or  stability.  This  being  the 
case,  the  question  arises  as  to  how  this  end  may  best  be  secured. 

Probably  the  most  keenly  contested  question  on  this  whole  problem 
of  blending  is  whether  it  shall  be  done  by  the  miller  or  the  baker.  Of  prior 
importance,  however,  to  this  matter  oi  by  whom  the  blending  shall  be  per- 
formed is  that  of  the  baker’s  actual  requirements  in  flour.  Evidently  the 
baker  who  works  either  with  a ferment  and  dough,  or  an  off-ljand  dough, 
needs  but  one  flour  for  each  quality  of  bread,  and  may  therefore  either  buy 
a flour  which  suits  his  requirements,  ready  mixed  by  the  miller,  or  may 
purchase  individual  flours  and  mix  them  together.  With  the  increased 
adoption  of  straight  dough  systems,  there  is  naturally  a larger  demand  for 
ready  blended  flours.  But  even  those  who  employ  tliis  method  may  often 
find  a blend  of  their  own  more  suited  to  their  particular  requirements  than 
a single  miller’s  flour.  On  the  other  hand,  the  baker  who  employs  the 
sponge  and  dough  system  yvill,  in  the  great  majority  of  cases,  find  it  advan- 
tageous to  use  flours  of  a different  class  for  his  sponges  and  doughs  respec- 
tively. As  already  explained,  for  the  former  he  almost  invariably  selects 
a hard,  strong  flour,  which  is  best  made  from  either  Spring  American  or 
the  harder  Russian  wheats.  For  some  methods  of  working,  an  admixture 
of  a small  proportion  of  softer  flour  is  an  improvement,  as  the  proteins  of 
the  latter  exercise  a distinct  mellowing  and  ripening  effect  on  the  glutens 
of  the  hard  flours. 

For  doughing  purposes  the  wheat  or  flour  mixture  is  more  varied ; 
thus  the  soft,  sweet,  “ coloury  ” flours  are  used  at  this  stage  ; so  also 
is  usually  a certain  proportion  of  hard  flour,  which,  if  not  too  much,  is 
sufficiently  softened  by  the  diastatic  action  of  the  softer  flours  by  which 
it  is  accompanied. 


474 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

A very  interesting  paper  on  Flour  Blending  was  read  before  the  Bakers’ 
National  Association,  at  Belfast,  by  W.  T.  Hibbard,  of  Gloucester,  who 
discussed  the  question  of  whether  millers  or  bakers  should  do  the  blending, 
arguing  that  this  should  be  the  duty  of  the  miller.  This  view  was  princi- 
pally based  on  the  assumption  that  the  miller’s  education  and  training 
best  fitted  him  for  making  accurately  the  necessary  selections  of  wheat 
and  then  blending  them.  So  long  as  the  miller  possesses  this  knowledge, 
and  the  baker  does  not,  the  argument  is  unanswerable  ; but  there  is  no 
real  reason  why  the  baker  should  not  himself  acquire  this  information  and 
experience,  and  then  the  argument  no  longer  applies.  Dealing  with  the 
question  of  blending,  apart  from  by  whom  performed,  Mr.  Hibbard’s  paper 
contained  some  most  useful  information  conveyed  on  somewhat  the  same 
lines  as  laid  down  in  the  wheat  and  flour  dictionaries  given  earlier  in  this 
work.  The  ideal  mixture  recommended  for'making  a loaf  that  shall  be 
sweet  and  nutty  flavoured,  of  good  size  and  appearance,  of  fine  bloom, 
and  which  shall  keep  nice  and  moist  for  days,  in  fact  perfection,  is  the  follow- 
ing 


For  Sponging — 

Per  cent. 

High-grade  Spring  American  Patent 

. . 20 

High-grade  firm  white  Dantzic 

. . 10 

For  Doughing — 

High-grade  Cones  flour 

. . 25 

Talavera  straight -grade 

. . 25 

Fine  Winter  American  or  Polish  Patent.  . 

. . 10 

Fine  Hungarian 

. . 10 

100 

There  is  always  a demand  by  the  more  advanced  Bakers  for  flours  milled 
from  single  wheats,  a demand  evidently  based  on  the  greater  individuality 
which  such  flours  naturally  possess.  Among  these  are  hard  Spring  Ameri- 
cans, which  can  be  differentiated  into  Manitoban  wheat  flours,  Northern 
Minnesota  flours,  and  Southern  Minnesota  flours,  all  of  which  have  their 
special  characteristics.  Prime  hard  Russian  wheat  flours  would  also  find 
a market  were  they  obtainable.  Winter  American  flours,  both  from  soft 
wheats  and  also  the  hard  Kansas  wheats,  may  also  be  included  in  this  group. 
So,  too,  may  best  English  wheat  flours,  and  also  those  from  Hungarian 
wheats. 

The  following  are  among  the  advantages  which  accrue  to  the  baker  by 
working  on  the  principle  of  blending  flours  : — 

(1)  There  are  frequently  offering  parcels  of  flour  which  possess -in  a 
marked  degree  some  one  quality,  but  are  deficient  in  others.  Because 
they  cannot  well  be  used  alone,  they  may  be  purchased  at  a lower  figure, 
and  the  blender,  by  mixing,  can  utilise  such  flour  to  advantage.  In  other 
words,  given  the  requisite  knowledge,  it  is  often  cheaper  to  prepare  the 
quality  and  character  of  flour  required  for  use  from  a mixture  of  different 
qualities  obtainable  on  the  market,  than  to  buy  the  actually  wanted  quality 
mixed  ready  for  use. 

(2)  The  baker  who  blends  flours  has  a greater  control  over  the  quality 
and  character  of  the  flour  he  uses  in  his  work.  Thus,  he  can  readily  either 
improve  or  diminish  the  value  of  his  sponging  flours  by  the  addition  of  a 
bag  or  a sack  of  a better  or  worse  flour  : so,  too,  colour,  flavour,  and  other 
characteristics  of  his  flours  can  be  readily  modified  at  will,  and  much  more 
effectively  than  if  he  simply  obtains  one  ready-made  flour  from  the  miller. 
He  can  similarly  modify  a flour  used  for  straight  doughs.  ' 


BREAD-MAKING. 


475 


(3)  The  baker  can  introduce  each  particular  variety  of  flour  at  that 
stage  of  fermentation  which  best  suits  its  particular  characteristics. 

Blending  affords  greater  chances  of  successful  work  with  flour,  but  at 
the  same  time  entails  greater  risks,  because  accurate  knowledge  of  the  pro- 
perties and  the  characters  of  the  various  flours  blended  is  requisite,  and  also 
of  their  effect  on  each  other  when  blended. 

The  baker  who  blends  should  lay  himself  out  to  select  flours  for  their 
predominant  quality  ; for  example,  one  brand  for  strength,  another  for 
colour,  another  for  flavour,  and  so  on.  By  appropriate  means  he  will  judge 
the  exact  character  of  each  of  these  flours  in  the  separate  state,  and  then 
can  readily,  with  a little  care,  prepare  whatever  blends  best  suit  his  work. 
The  modern  baker  will  have  no  difflculty  in  finding  his  requirements  in 
this  direction  met  by  the  modern  miller. 

Millers,  in  blending,  usually  first  mix  their  wheats,  and  let  them  lie  a 
time  before  sending  to  the  rolls — if  hard  and  soft  wheats  are  thus  blended, 
each  exerts  a favourable  influence  on  the  other  in  the  way  of  rendering  it 
more  amenable  to  milling.  Thus,  a very  hard  wheat,  and  also  a very  soft 
one,  are  each  more  difficult  to  mill  successfully  than  a mixture  of  inter- 
mediate character  ; and  consequently  a miller’s  argument  is  this — if  the 
two  flours  are  to  be  mixed  after  being  milled,  why  not  have  the  wheats  first 
mixed,  as  the  resultant  flour  is  of  better  quality,  everything  else  being  equal, 
than  if  the  two  separate  flours  are  mixed  after  milling  ? On  the  other 
hand,  certain  millers  have  distinct  and  separate  plants,  the  one  for  hard 
wheats  and  the  other  for  soft,  and  mill  and  treat  each  separately,  after- 
wards mixing  the  flours.  The  evidence,  therefore,  of  even  millers  themselves 
is  undecided  on  this  point  of  blending  before  or  after  milling. 

Whether  blending  be  done  by  the  miller  or  the  baker,  an  undoubted 
advantage  arises  from  the  latter  having  a clear  idea  of  his  exact  require- 
ments in  flour,  and  how  they  may  best  be  met.  With  clear  and  full  know- 
ledge on  these  points,  whether  the  baker  blends  himself  or  gets  that  service 
performed  for  him  by  the  miller,  the  result  is  the  more  economic  production 
of  a better  and  higher  class  loaf. 

612.  Changes  in  Flour  resulting  from -Fermentation. — A series  of  experi- 
ments has  been  made  by  the  authors  with  the  following  objects  : — 

I.  Determination  of  the  amount  of  gas  evolved  during  fermentation 
under  the  described  conditions. 

II.  Investigation  of  the  changes  produced  by  fermentation  in  the  com- 
position of  the  flour. 

III.  Eflect  produced  by  the  addition  of  various  substances  to  the  flour 
on  the  quantity  of  gas  evolved,  and  on  the  changes  therein  resulting  from 
fermentation. 

Outline  of  Experimental  Method. — In  each  test,  200  grams  of  flour  were 
taken,  and  100  grams  of  water  at  30°  C.  ; these  with  2 grams  of  salt,  and  4 
grams  of  fresh  distillers’  compressed  yeast  formed  the  basis  of  the  dough. 
Various  additions  were  made  as  subsequently  described.  The  doughs  were 
carefully  mixed  with  a spatula  in  a basin,  and  finally  made  by  hand,  but 
with  as  little  handling  as  possible.  They  were  then  transferred  to  a weighed 
enamelled  steel  beaker  and  the  weight  ascertained.  Waste  and  loss  in 
making  were  thus  determined.  A small  portion  of  the  dough  was  then  taken 
for  estimation  of  water  and  solids.  The  remainder  was  carefully  weighed, 
and  the  beaker,  a,  at  once  inserted  in  the  fermenting  apparatus.  This 
consisted  of  a gun-metal  vessel,  h,  Fig.  43,  fitted  with  a glass  lid,  c,  and 
an  outlet  tubulure,  d.  The  vessel,  h,  was  fixed  in  a water  bath,  e,  maintained 
at  a constant  temperature  by  means  of  an  automatic  gas  regulator,  /.  The 
tubulure,  d,  was  connected  with  a gas  measuring  apparatus,  g,  similar  to  that 


476 


THE  TECHNOLOGY  OF  BREAH-MAKING. 


described  on  page  199.  The  joint  between  h and  c was  made  with  rubber 
solution,  and  the  two  fastened  together  by  means  of  four  screw  clamps,  h, 
applied  round  the  edges.  The  doughs  when  made  had  a temperature  of 
26°  C.,  and  the  water  bath  was  kept  at  that  temperature  throughout  the 


whole  series  of  experiments.  The  volume  of  gas  evolved  was  read  off  at 
intervals,  usually  of  one  hour,  and  the  readings  continued  for  6 hours, 
with  the  exception  of  No.  IV.,  in  which  they  were  taken  for  20  hours. 
The  beaker  of  fermented  dough  was  then  removed  from  the  apparatus 
and  weighed.  An  analysis  was  subsequently  made  on  the  fermented 
dough. 

The  following  table  gives  the  numbers  of  the  experiments,  and  the  sub- 
stances used  in  each.  As  already  mentioned,  the  four  principal  ingredients 
were  always  taken  in  the  same  proportions,  viz.,  flour,  200  grams ; water, 
100  grams  ; salt,  2 grams ; and  yeast,  4 grams.  The  yeast  throughout  was 
the  same  brand,  and  that  employed  was  selected  each  day  from  the  centre 
of  a fresh  and  previously  unopened  bag. 

No.  I.  Flour,  water,  salt,  no  yeast. 

,,  II.  Flour,  water,  salt,  malt  flour  1 gram,  no  yeast. 

,,  III.  Flour,  water,  salt,  yeast. 

,,  IV.  Flour,  water,  salt,  yeast  (2nd  experiment). 

,,  V.  Flour,  water,  salt,  yeast,  sugar  2 grams. 

„ VI.  Flour,  water,  salt,  yeast,  starch  2 grams,  gelatinised  in  portion 
of  the  water. 

,,  VII.  Flour,  water,  salt,  yeast,  malt  flour  1 gram. 

„ VIII.  Flour,  water,  salt,  yeast,  starch  2 grams,  gelatinised  in  portion 
of  the  water,  malt  flour  1 gram. 


BREAD-MAKING.  - 477 

Gas  Evolved. 


No  evolution  of  gas  occurred  in  Nos.  I.  and  II . 


Time. 

Xo.  III. 

Xo.  IV. 

Xo. 

V. 

Xo.  VI. 

Xo.  VII. 

Xo.  VIII. 

0 

245 

245 

0. 

[350 

350 

'170: 

t250 

1 

^343 

1 

Il87 

1 hour 

170 1 

1 

1 

'240 

256  { 

1 

1 

[316 

343 1 

1 

^440 

187 1 

1 

1 

l293 

365 

610 

384 

734 

2 hours 

410 

1 

572 

1490 

783 

480 

1 

440 

1,050 

[416 

1 

l360 

1 

1 

^536 

1 

l342 

3 „ 

1,150 

209 

1,359 

770 1 

1 

l380 

1,062 1 

1 

[400 

1,319| 

1 

k75 

822 1 

1 

[360 

330 

1,380 

165 

4 „ 

1,150| 

1 

1,462 1 

1,794| 

1 

1,182| 

[l98 

1 

^340 

[l85 

1 

t258 

1 

[344 

5 

1,545 

1,557 

1,490  ^ 

1 

1,647; 

2,052 1 

1 

1,526 1 

125 

104 

1,661 

[330 

[l80 

1 

[268 

1 

[310 

6 ,, 

1,670^ 

1,820^ 

1 

1,827' 

) 

2,320^ 

1 

1,836^ 

1 

[ 96 

7 „ 

1,757 

92 

8 „ 

1,849 

176 

10  „ 

2,025 

[l56 

12  „ 

2,181 

109 

2,290 

14  „ 

1 

109 

16  „ 

2,399 

106 

2,505 

! 104 

1 

18  „ 

i 

20  „ 

2,609^ 

! 

Numbers  I.  and  II.  were  made  up  in  order  to  make  subsequent  tests  on 
the  doughs  after  standing.  As  would  be  expected,  there  was  no  evolution 
of  gas  in  either  case.  No.  III.  may  be  compared  with  a somewhat  similar 
experiment  described  in  paragraph  466.  There  the  conditions  were  as  nearly 
as  possible  those  of  actual  practice  : it  may  be  taken  therefore  that  the 
fermentation  in  this  latter  case  was  more  than  double  that  which  occurs  in 
normal  bread-making,  being  represented  by  1,670  c.c.  as  against  705  c.c.  of 
gas.  Nos.  III.  and  IV.  are  duplicates  for  the  first  6 hours,  but  in  IV.,  gas 
was  evolved  much  more  vigorously  at  the  start,  a result  which  must  be 
regarded  as  due  to  greater  initial  fermentative  power  in  fresh  yeast  of 
another  day’s  supply.  At  the  end  of  6 hours  the  quantity  evolved  was 
practically  alike  in  both  cases,  1,670  as  against  1,661  c.c.  But  right  up  to 
the  close  of  No.  IV.  there  was  a considerable  and  steady  evolution  of  gas. 
Nos.  V.  and  VI.,  respectively  containing  added  sugar  and  gelatinised  starch, 
gave  about  the  same  amount  of  gas,  1,820  and  1,827  c.c.,  the  maximum 
production  of  gas  being  greater,  however,  in  No.  VI.  In  No.  VII.,  to  which 
malt  flour  had  been  added,  there  was  considerably  more  gas  than  in  any 
of  the  other  tests,  2,320  c.c.  This  amount  is  equivalent  to  that  evolved  in 
No.  IV.  in  about  14 J hours.  In  No.  VIII.,  which  contained  both  malt 


478 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


flour  and  gelatinised  starch,  the  gas  evolved  was  only  about  the  same  as 
gelatinised  starch  only,  1,836  as  against  1,827  c.c. 

Analyses  of  Flour  and  Dough. — In  the  flour,  the  gluten  was  determined 
in  the  usual  manner,  and  dried.  The  true  gluten  was  estimated  by  the 
Kjeldahl  process  on  the  dry  gluten.  The  gliadin  is  that  yielded  by  direct 
extraction  of  the  w^et  gluten  from  10  grams  of  flour,  being  2*8  grams.  A 
measured  quantity  of  100  c.c.  of  70  per  cent,  alcohol  was  employed.  The 
w’et  gluten  and  20  grams  of  w'ashed  and  dried  precipitated  chalk  w ere  placed 
in  a mortar  and  triturated  with  a sufficiency  of  the  alcohol  to  produce  a 
slack  dough.  The  trituration  was  continued  until  the  whole  of  the  gluten 
was  disintegrated,  no  visible  particles  being  present.  This  dough,  together 
w ith  the  remainder  of  the  alcohol,  w as  transferred  to  a flask  and  vigorously 
shaken.  In  every  case  the  sediment  w'as  carefully  examined  in  order  to 
see  that  all  the  gluten  had  been  thoroughly  comminuted.  The  contents  of 
the  flask  w^ere  then  raised  to  the  boiling  point,  and  again  thoroughly  shaken. 
The  flask  was  then  allow'ed  to  stand  over  night,  shaken  up  once  more  in 
the  morning,  allow'ed  to  settle  for  a few  minutes,  and  filtered.  A direct 
estimation  by  weight  w^as  then  made  by  evaporating  50  c.c.  of  the  filtrate 
and  drying  off  in  a tared  glass  dish.  True  gluten,  less  gliadin,  w^as  then 
reckoned  as  glutenin.  The  soluble  extract  was  obtained  by  the  addition 
of  500  c.c.  of  distilled  w^ater  to  50  grams  of  the  flour,  shaking  vigorously  at 
intervals  during  30  minutes  in  the  cold  and  then  filtering  after  5 minutes" 
subsidence.  A sufficient  quantity  of  a turbid  filtrate  was  almost  immedi- 
ately obtained,  and  this  w^as  filtered  bright  on  a separate  filter.  Aliquot 
parts  of  this  solution  w ere  taken  for  the  estimation  of  reducing  and  non- 
reducing sugars  and  soluble  proteins. 

The  doughs  w^ere  first  thoroughly  mixed  and  re-kneaded  ; 50  grams 
w'ere  then  taken,  and  washed  in  successive  small  quantities  of  tap  water 
(deep  w^ell  from  the  chalk),  wdth  separation  of  gluten.  As  50  grams  of 
dough  contain  about  21  grams  of  starch,  having  a specific  gravity  of  1*5, 
the  starch  present  w^as  assumed  to  occupy  14  c.c.  The  w^ashing  w^ater 
w'as  therefore  made  up  to  514  c.c.,  allowing  500  c.c.  of  liquid.  To  this  solu- 
tion, 10  grams  of  thoroughly  washed  and  dried  kieselguhr  w'ere  then  added, 
and  the  solution  filtered  bright.  Total  soluble  matters,  sugars,  and  pro- 
tein, w ere  then  determined  in  the  filtrate.  The  gluten  w as  weighed  in  the 
w et  and  dry  states,  and  true  gluten  and  gliadin  and  glutenin  estimated  as 
before.  The  moisture  w^as  determined  direct  on  a portion  of  the  dough,  and 
the  acidity  on  another  portion  direct.  The  dough  w^as  triturated  with 
distilled  w^ater  in  a mortar  and  titrated  Avith  phenolphthalein  and  A/10 
soda,  the  acidity  being  calculated  as  lactic  acid. 

The  results  of  the  analyses  are  given  in  the  following  table,  both  on  the 
flour  and  dough  as  examined  and  as  calculated  on  the  w^ater-free  solids. 
The  numbers  attached  to  the  doughs  are  the  same  as  before  ; the  flour  is 
designated  No.  0. 

The  moisture  in  the  doughs  cannot  be  regarded  as  absolutely  exact, 
since  there  is  a difficulty  in  obtaining  a perfectly  fair  sample  : there  must 
also  be  a slight  loss  through  continued  fermentation  in  the  hot-water  oven. 
An  examination  of  these  results  show^s  that  a greater  quantity  of  wet  gluten 
was  obtained  from  all  the  doughs,  except  No.  IV.,  than  was  obtained  from 
the  flour.  In  No.  IV.  there  is  a very  marked  diminution.  Speaking  gener- 
ally the  dry  glutens  are  slightly  low^er  than  in  the  flour,  thus  showing  that 
as  a result  of  fermentation  the  w^ater-retaining  powder  of  the  gluten  is  in- 
creased. As  might  be  expected,  the  dry  gluten  also  of  No.  IV.  is  much  less. 
The  ratios  of  wet  to  dry  gluten  of  Nos.  0.,  I.,  III.,  and  IV.,  are  as  follow’s  : 
2-70,  3*22,  3*24,  2*85.  It  will  be  seen  that  the  w’ater-retaining  pOAver  of  the 
gluten  has  receded  under  the  long  fermentation  of  No.  IV.  to  practically 


BREAD-MAKING. 


479 


the  same  as  that  of  the  flour.  In  all  the  doughs  there  is  a diminution  of 
true  gluten.  The  proportion  of  protein  dissolved  from  the  wet  gluten  by 
treatment  with  70  per  cent,  alcohol  in  the  manner  described  is  much  less 
than  that  obtained  by  extraction  of  the  flour  direct  by  the  methods  usually 

Composition  of  Flour  and  Doughs. 


Constituents. 

Xo.  0. 

No.  I. 

No. 

II. 

As 

Exd. 

Water 

Free. 

As 

Exd. 

1 

Water 

Free. 

As 

Exd. 

Water 

Free. 

Moisture 

14-27 

42-11 

i 

41-99 

Gluten,  Wet.. 

28-05 

32  72 

20-40 

35-29 

20-70 

35-40 

„ Dry 

10-50 

12-14 

6-34 

10-97 

6-50 

IMl 

„ True 

8-87 

10-33 

5-31 

9-19 

5-84 

9-99 

Gliadin  ex  gluten  . . 

2-20 

2:80 

2-28 

3-91 

2-07 

3-54 

,,  per  cent,  of  True 

Gluten  . . 

— 

27-04 

— 

42-54 

— 

35-43 

Glutenin  ex  gluten  . . 

6-67 

7-53 

3-05 

5-28 

3-77 

6-45 

Soluble  Extract 

4-04 

4-71 

4-07 

7-04 

5-91 

10-11 

,,  Protein 

1-24 

1-45 

0-34 

0-59 

0-40 

0-69 

Reducing  Sugars 

1-09 

1-27 

0-63 

1-15 

0-47 

0-80 

Non-reducing  Sugars 

0-16 

0-19 

1-54 

2-67 

2-56 

4-38 

Acidity  as  Lactic  Acid 

— 

— 

— 

— 

0-084 

0-144 

- No. 

III. 

No. 

IV. 

No. 

V. 

Moisture 

'43-65 



44-49 

1 

44-55 



Gluten,  Wet.. 

20-3 

35-93 

13-78 

24-80 

19-92 

35-86 

,,  Dry 

' 6-28 

11-08 

4-84 

8-71 

6-10 

10-98 

,,  True 

5-73 

10-14 

4-29 

7-72 

5-25 

9-45 

Gliadin  ex  gluten  . . 

1-81 

3-20 

M7 

2-10 

1-74 

3-13 

,,  per  cent,  of  True 

Gluten  . . 

— 

31-55 

— 

27-21 

— 

33-12 

Glutenin  ex  gluten  . . . . 

3-92 

6-94 

3-11 

5-60 

3-51 

6-32 

Soluble  Extract  . . . . i 

3-81 

6-73 

3-97 

7-14 

3-50 

6-30 

,,  Protein 

0-50 

0-88 

0-55 

0-98 

0-40 

0-72 

Reducing  Sugars 

0-04 

0-07 

0-40 

0-72 

0-20 

0-36 

Non-reducing  Sugars 

0-58 

1-02 

0-33 

0-60 

0-35 

0-63 

Acidity  as  Lactic  Acid 

0-09 

0-159 

0-09 

0-162 

0-09 

0-162 

No. 

VI. 

No. 

VII. 

No. 

VIII. 

Moisture 

43-68 

— 

44-35 

— 

43-28 



Gluten,  Wet..  ..  ' 

19-16 

33-91 

19-20 

34-56 

19-88 

34-99 

,,  I)ry 

6-02 

10-97 

5-91 

10-64 

6-01 

10-58 

,,  True  . . . . 

5-40 

9-56 

5-34 

9-61 

5-41 

9-52 

Gliadin  ex  gluten  . . 

1-94 

3-43 

1-96 

3-53 

2-14 

3-77 

,,  per  cent,  of  True  ; 

Gluten  . . . . 

— 

35-87 

— 

36-73 

. — . 

39-60 

Glutenin  ex  gluten  . . . . 

3-46 

6-12 

3-38 

6-08 

3-27 

5-75 

Soluble  Extract  . . . . 

4-28 

7-57 

4-63 

8-33 

4-94 

8-69 

,,  Protein  . . . . 

0-40 

0-71 

0-34 

0-61 

0-40 

0-70 

Reducing  Sugars  . . 

0-35 

0-62 

0-86 

1-55 

0-51 

0-90 

Non-reducing  Sugars 

0-54 

0-95 

0-74 

1-33 

0-67 

1-18 

Acidity  as  Lactic  Aci  \ 

0-09 

0-159 

0-09 

0-162 

0-09 

0-158 

1 

4e0 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


r.dopted.  These  results  are  therefore  not  comparable  with  those  of  ghadin\ 
ex  flour,  but  may  be  compared  among  themselves.  The  most  instructive 
comparison  is  probably  that  of  the  various  percentages  of  gliadin  in  true 
gluten  with  each  other.  Of  the  flour  true  gluten,  27*04  per  cent,  was  thus 
dissolved.  In  the  dough  treated  with  salt.  No.  II.,  this  figure  had  increased 
to  42*54,  while  in  No.  III.  it  was  also  high.  In  No.  III.  there  is  an  increase 
of  the  soluble  gluten  over  that  in  the  flour,  while  with  the  over-fermentation 
of  No.  IV.  the  soluble  portion  of  the  gluten  has  diminished.  A possible 
explanation  of  this  is  that  in  washing  this  long-acted-on  gluten  some  of  the 
gliadin  is  lost  by  washing  away.  In  all  the  glutens  from  the  more  normally 
fermented  doughs,  there  is  an  increase  in  the  proportion  which  is  soluble. 
(It  is  shown  in  paragraph  851,  that  chalk  removes  some  of  the  gliadin 
from  solution  by  adsorption.  These  gliadin  results  are  therefore  too- 
low,  but  are  nevertheless  comparable  among  themselves.)  In  the  soluble 
extracts,  that  of  the  flour  is  4*71,  a figure  materially  increased  in  the- 
salt  made  dough  : it  is  very  probable  this  would  have  been  more  in  a 
dough  made  from  flour  and  water  only.  The  addition  of  malt  flour,  as 
might  be  expected,  caused  a still  further  increase  in  the  amount  of  soluble 
matter  present.  The  malt  flour  used  had  a diastatic  capacity  of  48*6° 
Lintner,  and  31*93°  when  tested  with  ordinary  starch  solution  instead  of 
that  of  soluble  starch.  Although  in  all  the  fermentation  tests  there  was  a 
destruction  of  some  of  the  soluble  matter  by  the  yeast,  yet  that  remaining 
is  more  than  the  soluble  matter  of  the  flour  itself.  In  every  case  there  is 
much  less  soluble  protein  obtained  from  the  doughs  than  from  the  original 
flour.  The  reducing  sugars  are  calculated  as  maltose  from  the  cupric 
reducing  power  of  the  solutions  in  each  case.  It  is  difficult  to  see  why  this 
should  have  been  less  in  Nos.  II.  and  III.,  but  still  the  fact  remains. 

In  the  fermented  doughs,  hydrolysis  of  starch  and  fermentation  of  sugar 
are  proceeding  together,  and  except  in  No.  VII.,  the  combined  causes  have 
caused  a diminution  in  the  reducing  sugars.  The  solutions  were  in  eAl 
cases  inverted  in  the  ordinary  manner  by  the  addition  of  hydrochloric 
acid  and  heating  to  68°  C.  The  consequent  increased  cupric  reducing 
power  was  ascribed  to  the  presence  of  cane  sugar  and  calculated  as  such. 
Here  again  there  are  some  anomalies,  as  the  flour  yielded  only  0*19  per 
cent,  of  non-reducing  sugar.  Under  the  influence  of  salt,  No.  I.,  and  salt 
and  malt.  No.  II.,  this  figure  increased  in  these  doughs  to  2*67  and  4*38- 
respectively.  This  treatment  can  scarcely  be  expected  to  have  actually 
resulted  in  the  production  of  cane  sugar.  It  is  suggested  as  a possible- 
explanation  that  the  soluble  extract  may  have  consisted  in  part  of  soluble 
starch  or  some  of  the  higher  and  unstable  dextrins,  and  that  these  were 
converted  into  maltose  by  the  hydrochloric  acid,  and  hence  the  considerable- 
increase  in  cupric  reducing  power.  In  the  case  of  all  the  fermented  doughs, 
there  is  an  increase  in  the  non-reducing  sugars,  determined  in  the  same  man- 
ner. The  acidity  results  are  rather  surprising,  as  in  all,  including  the  very 
long  fermentation.  No.  IV.,  the  quantity  obtained  is  practically  the  same. 

Further  Data  on  Doughs. — With  the  aid  of  the  preceding  tables  some 
further  data  may  now  be  given  of  these  doughs.  These  follow  and  are 
mostly  self-explanatory.  The  weighs  of  raw  materials  are  given,  and  also 
that  of  the  dough,  showing  the  loss  incurred  in  making.  The  loss  in  fer- 
mentation is  that  obtained  by  direct  weighing  before  and  after.  The  vol- 
ume of  gas  was  that  read  off  in  c.c.  in  each  experiment.  This  was  converted 
into  grams  by  multiplying  by  the  factor,  0*00185.  As  100  grams  of  sugar 
are  required  for  the  production  of  46*4  grams  of  carbon  dioxide,  the  number 
of  c.c.  of  gas,  multiplied  by  the  factor  0*004,  gives  the  weight  of  sugar  re- 
quired for  its  production.  The  alcohol  produced  may  be  taken  as  about 
one-half  the  sugar  required.  The  figures  obtained  in  this  manner  must  be 


Various  Data  of  Doughs. 


BREAD-MAKING. 


481 


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482 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


regarded  as  only  approximate,  but  represent  with  a reasonable  degree  of 
accuracy  the  results  in  the  particular  experiments.  The  soluble  extract 
of  the  unfermented  dough  is  calculated  from  that  of  its  constituents,  while 
that  of  the  unfermented  dough  was  directly  determined. 

There  was  a certain  amount  of  loss  in  weight  during  the  time  of  remain- 
ing in  the  fermenting  apparatus  even  with  the  doughs  which  contained  no 
yeast.  In  the  fermented  doughs,  the  loss  in  weight  varied  from  3*20  to 
5*60  grams,  or  1*07  to  1*87  per  cent.  The  weight  of  carbon  dioxide  evolved 
varied  from  3'09  to  4*71  grams,  and  in  most  cases  very  nearly  agreed  with  the 
loss  in  weight  of  the  dough.  Apparently  therefore  very  little  escapes  from 
the  dough  during  fermentation  except  the  gas  produced,  the  alcohol  remain- 
ing in  the  dough.  The  determined  loss  of  weight  and  calculated  amount 
of  alcohol  produced  together  are  in  close  agreement  with  the  sugar  which 
has  disappeared.  From  the  foregoing  data  it  was  possible  to  arrive  at 
approximately  the  amount  of  matter  rendered  soluble  during  fermentation. 
On  substracting  the  soluble  matter  of  the  unfermented  dough  from  that 
found  after  fermentation,  and  then  adding  on  the  sugar  which  has  been 
decomposed  into  gas  and  alcohol,  the  resultant  figure  is  that  required. 
Except  in  the  case  of  No.  V.,  where  sugar  was  added  to  the  dough,  the  solu- 
ble matter  of  the  fermented  is  greater  than  that  of  the  unfermented  dough, 
notwithstanding  the  continuous  diminution  of  same  by  gas  production.  It 
vill  be  first  of  all  interesting  to  observe  the  respective  amounts  of  hydrolysis 
in  each  case.  With  the  flour  itself  there  is  a noticeable  increase,  1*35  per 
cent,  of  its  water-free  solids  having  been  rendered  soluble.  As  'might  be 
expected,  the  malt  flour  in  No.  II.  greatly  increased  this  figure.  Fermen- 
tation for  6 hours  resulted  in  rather  more  soluble  extract,  vhile  the  figure 
was  much  more  with  the  longer  fermentation.  The  addition  of  sugar  to 
the  dough  lessened  the  amount  of  soluble  matter  produced  by  fermentation. 
That  vdth  gelatinised  starch.  No.  VI.,  is  very  nearly  the  same  as  the  plain 
dough.  No.  III.  In  No.  VI.,  where  malt  flour  has  been  added,  the  produc- 
tion of  soluble  matter  has  been  very  high  ; in  the  case  of  No.  VIII.,  contain- 
ing both  malt  flour  and  gelatinised  starch,  there  is  less  conversion  during 
fermentation,  but  still  considerably  more  than  in  the  dough  with  gelatinised 
starch  alone.  The  amount  of  residual  soluble  matter  after  fermentation 
affords  some  guide  as  to  the  factors  governing  the  probable  moisture 
and  flavour  character  of  the  resultant  bread.  Comparing  Nos.  III.  and 
IV.,  the  much  prolonged  fermentation  of  the  latter  has  not  diminished 
the  amount  of  soluble  matter  remaining  in  the  fermented  dough,  the  figures 
being  3*81  and  3’97  per  cent.  In  other  words,  the  production  of  soluble 
matter  by  hydrolysis  has  more  than  kept  pace  with  its  removal  by  fermen- 
tation in  the  longer  time.  The  addition  of  sugar  in  No.  V.  has  not  resulted 
in  an  increase  of  residual  soluble  matter.  With  gelatinised  starch  there  is 
a slight  increase.  Malt  flour  shows  a high  figure  of  soluble  matter,  which 
is  still  higher  when  gelatinised  starch  has  also  been  added.  Summarising 
the  results  under  three  heads  : — 

I.  Stimulvs  to  Fermentation. — Both  sugar  and  gelatinised  starch  cause 
a slight  increase,  malt  flour  alone  a very  large  increase. 

II.  Stimulus  to  Hydrolysis  (production  of  soluble  matter). — Rather  less 
when  sugar  has  been  added.  Much  increased  by  malt  flour,  and  also  in- 
creased by  same,  though  to  less  extent  when  gelatinised  starch  is  also  added. 

III.  E1]ect  on  Residual  Soluble  Matter. — Not  increased  by  this  amount 
of  sugar,  increased  by  gelatinised  starch,  still  more  by  malt  flour,  and  yet 
more  by  malt  flour  and  gelatinised  starch  conjointly. 


CHAPTER  XIX. 

SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES. 


613.  These  are  now  so  numerous  that  a description  of  some  few  of  the 
leading  and  characteristic  types  may  well  be  here  included  as  a special 
chapter. 

614.  Systeme-Schweitzer. — Prom  time  to  time  efforts  are  made  to  sim- 
plify the  whole  process  of  the  conversion  of  wheat  into  bread,  and  thus 
cheapen  its  production.  An  interesting  and  ingenious  example  of  such 
an  attempt  is  furnished  by  the  system  designed  by  M.  Schweitzer  and 
worked  by  him  in  Paris  about  1900.  The  whole  essence  of  the  method 
was  the  carrying  on  of  both  milling  and  baking  as  a part  of  one  business 
in  the  same  factory,  so  that  the  firm  purchased  wheat  and  delivered  bread 
to  the  consumer.  All  the  intermediate  expenses  of  packing,  handling  and 
selling  flour  were  thus  to  be  eliminated  ; and  these  in  themselves  were 
regarded  as  sufficient  to  yield  a working  profit.  The  milling,  kneading, 
and  other  machinery  were  more  or  less  inventions  of  the  originator,  and 
were  ingeniously  designed  to  meet  the  special  requirements  of  the  system. 
The  mills  were  of  steel,  and  produced  a flour  of  a type  somewhat  resembling 
an  old-fashioned  stone-milled  flour.  The  resultant  bread  was  comparatively 
dark  in  colour,  and  possessed  the  defects  and  qualities  of  bread  made  from 
flour  of  this  kind.  As  in  all  other  cases  where  the  endeavour  is  made  to 
cut  out  parts  of  the  scheme  of  gradual  reduction  of  flour,  and  lengthen  the 
yield,  the  flour  suffers  in  quality. 

615.  Apostoloff  System  of  Bread-making. — In  this  case  the  object  aimed 
at  by  the  inventor  was  the  direct  utilisation  of  the  floury  constituent  of 
“ middlings  ""  (^.e.,  the  mixed  floury  and  branny  granules  of  the  miller) 
by  a process  of  aqueous  extraction  of  the  middlings  themselves  in  lieu  of 
the  customary  grinding  operations,  and  subsequent  separation  of  the  flour. 
It  was  claimed  for  this  moist  process  of  extraction  that  the  entire  floury 
constituents,  as  well  as  the  valuable  food  ingredients  which  are  usually 
rejected  with  the  waste,  are  thus  separated  from  the  bran  in  a form  in  which 
they  can  be  used  in  bread-making.  The  middlings  were  first  treated  with 
water  in  order  to  dissolve  out  the  floury  constituent  ; yeast  was  then  added 
to  the  liquid  which  was  thus  caused  to  ferment,  after  which  it  was  strained 
in  order  to  remove  the  bran  or  other  insoluble  matter.  This  strained  liquid, 
which  for  convenience  was  termed  “ lactus,”  was  then  passed  into  the  knead- 
ing trough  for  admixture  with  ordinary  flour.  In  working  the  invention 
with  the  greatest  degree  of  economy,  the  whole  of  the  middlings  produced 
in  grinding  a given  quantity  of  grain  would  be  treated  as  described  and  the 
resulting  liquor  employed  in  the  production  of  bread  by  admixture  mth 
the  flour  obtained  in  grinding  the  same  quantity  of  grain.  The  proportion 
of  water  used  must  vary,  but  in  the  proper  conduct  of  the  process  all  the 
liquid  and  yeast  required  for  admixture  with  the  flour  to  form  the  dough 
would  be  provided  by  the  fermented  liquor,  or  lactus.  In  working  the  in- 
vention, the  middlings  taken  will  be  those  actually  obtained  in  milling  the 

4S3 


484 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


sack  or  other  unit  weight  of  flour  required  for  the  batch,  or  an  equivalent  of 
middlings  from  any  other  source.  With  materials  of  good  average  quality, 
and  under  ordinary  conditions  of  working,  the  proportion  of  middlings  to 
water  in  the  mixing  vessel  should  be  about  9 to  100,  and  the  temperature 
should  be  about  86°  F.  The  mixture  is  allowed  to  stand  for  from  4 to  12  hours 
and  until  the  floury  constituent  of  the  middlings  has  become  thoroughly  soaked 
and  separated  from  the  branny  particles.  Yeast  is  added  to  the  mixture  from 
2 to  4 hours  before  the  liquor  is  to  be  run  off,  in  the  proportion  of  from  about 
three-quarters  to  one  pound  of  yeast  per  sack  of  flour.  As  fermentation 
proceeds  the  liquid  is  stirred  if  necessary  in  order  to  permit  the  escape  of 
the  accumulated  gases.  When  ready  to  be  run  off,  the  liquor  is  discharged 
into  a strainer,  and  the  lactus  separated  from  the  bran.  The  lactus  may 
be  regarded  as  the  “ ferment ""  used  in  this  method  of  bread-making.  A 
patent.  No.  12,106,  a.d.  1904,  was  obtained  by  Apostoloff  for  the  invention. 

The  following  is  the  result  of  an  experimental  investigation  of  the  process 
by  the  authors.  The  process  of  preparing  the  lactus  was  carried  out  in  the 
manner  described,  the  fermented  solution  of  middlings  being  strained 
through  a fine  horsehair  sieve.  Two  separate  lots  of  lactus  were  prepared 
from  a good  sample  of  middlings  from  white  wheats,  the  following  propor- 
tions being  used  : — 

a h 

Water  . . . . . . . . . . 100  parts.  100  parts. 

Middlings  . . . . . . . . . . 10  ,,  20  ,, 

The  following  figures  show  what  became  of  the  different  constituents 
of  the  middlings  : — 


a 

h 

Insoluble  branny  matter,  etc.,  strained  out 

In  the  lactus — 

22-5 

31*0 

Starch  and  Cellulose . . 

57*2 

44*8 

Insoluble  Proteins 

6-0 

10*1 

Soluble  Proteins 

5-1 

2*8 

Other  soluble  matters,  principally  Carbohydrates  . . 

9*2 

11*3 

In  the  more  dilute  preparation,  a higher  proportion  of  the  middlings 

passed  through  the  sieve,  also  much  more  of  the  proteins 

form. 

were  in 

the  soluble 

The  lactics  itself  gain  the  following  figures  on  analysis 

: — 

T 

Starch  and  Cellulose . . 

a 

5*6 

0 

8*7 

Insoluble  Proteins 

0-6 

2*0 

Soluble  Proteins 

0-5 

0*5 

Other  soluble  matters,  principally  Carbohydrates  . . 

0-9 

2*2 

Total  solids  . . 

7*6 

134 

Water  . . 

924 

86*0 

100*0 

100*0 

It  will  be  seen  from  the  above  that  the  a solution,  prepared  according 
to  the  directions  of  the  inventor,  contains  a larger  proportion  of  the  whole 
of  the  middlings  in  the  lactus.  Loaves  of  bread  were  made  of  which  particu- 
lars follow.  One  and  a half  litres  (1,500  c.c.  = 52*8  fluid  oz.)  of  liquid  w^ere 
taken  and  sufficient  flour  in  each  case  to  make  a dough  of  standard  con- 
sistency. The  weights  were  all  taken  in  grams,  but  for  the  more  general 
convenience  are  here  given  in  lbs.  From  these  are  calculated  the  respective 
quantities  to  the  sack  of  flour.  The  comparative  cost  per  loaf  may  then  be 
easily  deduced. 


SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES.  485 


Particulars  of  Bread. 


1. 

1 2.  3. 

Water  . . . . . . fluid  ozs. 

52-8 

Ferment  or  lactus,  a ,, 

— 

52-8 

— 

}}  3J  ^ 5? 

— 

— 

52-8 

Flour  . . . . . . . . lbs. 

5-625 

4-700 

4-031 

Fermented  dough,  weight  of  ,, 

8-781 

7-916 

7-343 

Calculated  to  per  sack  of  flour  (280  lbs.) 

Water  . . . . . . . . quarts 

65-7 

— 

— 

Ferment  or  lactus,  a . . ,, 

— 

77-8 

— 

* 33  33  ^ • • 33 

— 

— 

91-6 

Flour  . . . . . . . . lbs. 

280 

280 

280 

Fermented  dough,  weight  of  ,, 

437 

466 

510 

Half-quartern  loaves  at  2 lb.  3 ozs. 

of  dough  . . 

199-7 

213 

233 

Flour  used  per  loaf  . . . . lbs. 

1-402 

— 

— 

Flour  and  middlings  used  per  loaf  ,, 

— 

1-403 

1-392 

Middlings  used  per  sack  of  flour  ,, 

— 

19-0 

44-4 

Cost  in  flour  per  loaf  (235.  6d.  per 

sack)  . . . . . . pence 

1-412 

— 

— 

Cost  in  flour  and  middlings  per  loaf 

pence 

— 

1-376 

1-322 

Cost  in  flour  per  197-7  loaves 

235.  6d. 

— 

— 

Cost  in  flour  and  middlings  J per 

197-7  loaves 

— 

225.  lOfd. 

225.  Od. 

Composition  of  loaves  . . 

■ Water  . . . . per  cent. 

43-43 

44-11 

44-76 

Total  Proteins  . . ,,  | 

8-24 

1 

8-16 

7-80 

, With  a constant  quantity  of  flour,  280  lbs.,  the  amount  of  hquor  taken 
shows  a marked  increase  with  the  lactus  over  and  above  the  water.  This 
is  borne  out  by  the  weight  of  the  fermented  dough  and  the  calculated  num- 
ber of  half-quartern  loaves.  Apparently  therefore  there  is  a greatly  aug- 
mented yield.  This,  however,  is  apparent  rather  than  real,  for  when  flour, 
and  flour  and  middlings  respectively,  required  per  loaf  are  calculated,  the 
figures  are  practically  identical.  This  is  confirmed  by  the  close  agreement 
between  the  percentages  of  water  in  the  baked  bread.  The  cost  in  flour  per 
loaf,  and  also  that  in  flour  and  middlings,  show  very  little  difference,  but 
naturally  what  there  is,  is  in  favour  of  the  middlings  treated  loaves.  A 
direct  comparison  is  obtained*' by  determining  the  cost  per  197*7  loaves. 
With  flour  only,  this  was  235.  6d.,  that  is  the  cost  of  a sack  of  flour.  With 
the  lower  proportion  of  middlings  the  cost  was  225.  10|d.  per  197*7  loaves. 
The  comparison  with  the  higher  proportion,  h,  is  scarcely  fair,  because  double 
the  quantity  of  middlings  is  used  that  is  recommended  by  the  patentee, 
and  the  bread  was  unmarketable.  The  problem  in  the  No.  2 bread,  with  a 
lactus  is,  would  flour  purchased  at  225.  lOfd.  per  sack  make  a better  or  worse 
loaf  than  this  particular  sample  ? The  No.  2 bread  was  far  more  than  7id. 
per  sack  lower  in  quality  than  that  made  entirely  from  the  flour.  It  follows 
that  commercially  it  is  more  economical  to  buy  and  use  a cheaper  flour 
rather  than  use  middlings  in  this  manner. 

616.  Hovis  Meal  and  Bread. — In  Chapter  XVI,  paragraph  497,  an  account 
is  given  of  the  effect  of  germ  on  flour,  in  which  it  is  shown  that,  notAvith- 


486 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


standing  the  high  nutritive  value  of  this  body,  it  has  a most  injurious  effect 
on  flour.  This  effect  is  partly  due  to  the  tendency  of  its  high  percentage 
of  fat  to  become  rancid,  and  also  to  the  active  diastatic  character  of  its 
protein  constituents.  For  these  reasons  every  effort  was  made  to  obtain 
flour  as  perfectly  freed  as  possible  from  germ,  which,  as  a waste  product, 
found  its  way  into  the  offal  bin.  The  problem  of  utilising  germ  as  a bread 
food  for  many  years  engaged  the  attention  of  R.  Smith  of  Macclesfield,  who 
finally  invented  and  patented  a process  by  which  the  pure  wheat  germ,  as 
extracted  by  modern  milling  processes,  is  subjected  to  the  action  of  super- 
heated steam.  The  result  of  this  is  to  partly  cook  the  germ,  absolutely 
destroying  all  diastatic  properties,  and  converting  a highly  unstable  body 
into  one  with  good  keeping  qualities.  At  the  same  time,  this  heating  de- 
velops in  the  germ  a flavour  akin  to  that  so  highly  valued  in  malt,  and  also 
produced  by  the  action  of  heat.  One  part  of  this  prepared  germ,  together 
with  salt  in  about  the  quantity  used  in  bread,  is  then  mixed  in  with  three 
parts  of  white  flour  of  the  finest  quality,  and  constitutes  Hovis  flour  or  meal. 
The  Lancet  states,  as  a result  of  analysis  of  Hovis  bread,  that  its 
food  value,  both  as  regards  nitrogen  and  phosphates,  is,  broadly  speak- 
ing, double  that  of  bread  made  with  ordinary  wheaten  flour.  The  coarse, 
woody  fibre  of  the  grain  is  entirely  absent,  and  the  cellulose  is  in  a very 
finely  divided  state.  The  bread  is  not  only  highly  nutritious,  but  also  very 
digestible,  while  it  is  distinctly  laxative  without  being  in  the  slightest 
degree  irritating. 

Subjoined  are  analyses  by  the  authors  of  various  Hovis  preparations, 
with  average  white  flour  and  bread  results  for  purposes  of  comparison. 

Analyses  of  Hovis  Preparations. 


Moisture 

Proteins,  Insoluble  . 

,,  Soluble 
Cellulose,  finely  divided 
Starch,  etc.,  undissolved 
Maltose 

Soluble  Matter  other 
than  Protein  and 
Maltose 

Phosphoric  Acid,  P2O5 
Other  Mineral  Matter 
Fat 


Hovis. 

White. 

Meal. 

Bread. 

Biscuits. 

Flour. 

Bread. 

Whole, 

j Dried. 

Whole. 

Dried. 

12-20 

42-93 

4-56 

14-21 

1-38 

0-54 

57-66 

8-80 

1-27 

15-12 

2-22 

1 11-25  { 

9-5 

1-5 

} 7-51 

1 

12-52 

32-85 

57-86 









f 

4-44 

1 

7-77 

— 

— 

— 

— 

- 8-34  1 

6-15 

10-79 

20 -8P 

4-52^ 

4.741 

7-9C1  : 

0-87 

0-56 

0-96 

0-91 

0-25 

0-17 

0-28  , 

1-55 

0-92 

1-63 

1-93 

— 

— 

— 

3-25 

2-08 

3-65 



1-00 

0-68 

1-14 

These  particular  figures  represent  the  total  soluble  matter,  including  proteins. 


617.  Daren  Bread. — This  bread  is  prepared  from  a special  meal  made  by. 
Keyes’ Daren  Mills,  Ltd.,  Dartford,  Kent.  The  manufacturers  aim  at  secur- 
ing the  nutritive  advantages  of  germ  without  the  injurious  effects  of  that 
body,  and  accordingly  subject  separated  germ  to  a careful  cooking  process 
in  which  it  is  gently  roasted  while  in  constant  motion.  As  a result,  the 
germ  acquires  a very  pleasant  taste,  and  without  any  symptoms  of  burn- 


SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES.  487 


ing.  The  product  is  next  finely  ground,  and  then  mixed  with  flour  and 
a small  proportion  of  rye  meal.  Daren  meal  has  a high  nutritive  value, 
and  yields  a bread  of  agreeable  and  characteristic  flavour.  The  following 
is  the  result  of  an  analysis  of  this  meal  : — 


Analysis  of  Daren  Meal. 

Moisture 

..  11-60 

Proteins 

. . 15-57 

Carbohydrates,  Starch,  etc. 

. . 67-97 

Phosphoric  Acid  . . 

..  0-72 

Other  Mineral  Matter 

1-28 

Fat  . . 

2-86 

100-00 

Soluble  in  water,  per  cent. 

..  10-92 

618.  Turog  Bread. — Among  the  various  meals  now  offered  for  the 
manufacture  of  brown  bread,  that  sold  under  the  name  of  Turog  has  certain 
distinctive  characteristics.  The  flour  contains  a high  percentage  of  germ 
which  has  been  specially  treated  so  as  to  render  it  readily  assimilable. 
There  is  also  present  a normal  proportion  of  bran,  which  has  been  extremely 
finely  subdivided  and  freed  from  the  too  active  diastatic  constituents.  The 
object  of  the  manufacturers  has  been  to  retain  those  bodies  and  principles 
which  are  desired  in  whole  meal  bread  ; but  by  special  cooking  processes 
to  remove  the  irritating  influence  of  rough  bran  particles,  and  also  the 
extreme  diastatic  effects  of  the  cerealin  of  bran.  On  panification,  this 
flour  yields  a well  risen  and  good  texture  loaf,  similar  in  character  to  white 
bread,  instead  of  the  sodden  loaf  resulting  from  the  presence  of  enzymes 
in  excess.  The  following  is  the  mean  of  analyses  of  different  samples 


of  Turog  flour  : — 

Analysis  of  Turog  Flour. 

Moisture 

, . 12-71 

Proteins 

. . 15-38 

Carbohydrates 

..  68-91 

Phosphoric  Acid 

..  0-51 

Other  Mineral  Matter 

..  0-57 

Fat  . . 

1-92 

100  00 

Soluble  in  water,  per  cent. 

..  11-80 

619.  Malt  Extract  Breads. — ^These  may  be  divided  into  two  classes, 
those  in  which  the  malt  extract  is  used  as  an  “ improver  ” in  white  breads, 
and  those  in  which  a definite  and  more  extensive  diastatic  action  on  the 
starch  of  the  flour  is  required.  The  forerunner  of  breads  of  this  latter  de- 
scription was  that  originally  manufactured  under  Montgomerie’s  patent, 
and  noAv  made  and  sold  under  the  name  of  Bermaline  bread.  The  essence 
of  this  patent  is  the  preliminary  mashing  together  of  a portion  of  the  flour 
to  be  used,  with  the  malt  extract,  at  a temperature  of  I40°-150°  F.  for  some 
hours,  so  as  to  convert  a sufficiency  of  the  starch  into  dextrin  and  maltose. 
This  special  mixture  is  then  added  to  the  remainder  of  the  flour  and  other 
ingredients  employed  in  making  bread,  biscuits,  or  other  articles.  In  the 
working  of  the  patent  for  commercial  purposes,  other  substances  are  also 
employed  which  greatly  increase  the  palatability  of  the  articles  produced. 


488 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  following  experiments  made  by  one  of  the  authors  show  the  results 
of  various  methods  of  using  malt  extract  in  bread-making.  With  the  same 
extract,  and  under  the  same  comparative  conditions,  bread  was  made 
according  to  the  following  processes  ; — 

I.  Plain  Bread. — Tliis  was  bread  made  simply  with  flour,  water,  salt, 

and  yeast. 

II.  Malted  Bread. — This  was  similar  to  the  plain,  except  that  malt  extract, 

was  added,  at  the  doughing  stage,  in  the  same  proportion  as  in 
Nos.  III.  and  IV. 

III.  Montgomerie’ s Patent  Bread. — This  w^as  made  according  to  Mont- 

gomerie's patent. 

IV.  Alternative  Mashing  Process  Bread. — In  this  method,  the  flour  for  the 

“ mash  " was  mixed  with  water  and  gelatinised  by  raising  its  tem- 
perature to  190°  F.  It  was  then  cooled,  malt  extract  added, 
and  the  mixture  maintained  at  about  1 65°  F.  for  about  30  to  45 
minutes.  The  mash  prepared  in  this  manner  was  then  added  to  the 
other  ingredients  precisely  as  in  No.  III. 

The  following  are  the  results  of  experiment  on  the  ‘‘  mash  " in  Nos.  III. 
and  IV.  •— 


Quantities  Taken. 


No.  III.  Flour  2 lbs.  = 907 ‘2  grams. 
„ Water  3 lbs.  = 1360‘8  ,, 

„ Malt  Extract  1 lb  = 453  6 ,, 


No.  IV.  Flour  2 lbs.  = 907’2  grams. 
,,  Water  6 lbs. 

8i  oz.  = 2955-5  „ 

„ Malt  Extract  1 lb.  = 453-6  „ 


These  were  mashed  as  described.  The  larger  quantity  of  water  was 
necessary  in  the  second  case  because  of  the  starch  being  gelatinised.  It 
will  be  noticed  that  the  essential  point  of  distinction  between  Nos.  III.  and 
IV.  is  that  in  the  former  the  mashing  temperature  is  below  that  of  starch 
gelatinisation,  and  at  the  optimum  for  diastatic  action ; while  in  the  latter 
the  starch  is  gelatinised,  and  mashing  conducted  at  a temperature  at  which 
diastase  is  much  weakened,  being  near  that  at  which  it  is  absolutely  de- 
stroyed. The  composition  of  the  solid  in  the  mash,  at  the  end  of  the  treat- 
ment, was  in  each  case  ascertained  by  analysis.  A mash  prepared  by  Mont- 
gomerie, on  the  manufacturing  scale,  from  similar  proportions,  was  also 
subjected  to  analysis.  The  following  are  the  results  in  percentages  : — 


Composition  of  Solids  of  Malt  Extract  and  Flour  Mashes. 


No. 

III.  i 

No.  IV. 

Constituents. 

Laboratory 

Quantities. 

Manufacturing 

Quantities. 

Laboratory 

Quantities. 

Undissolved  Matter  . . 

38-45 

6-70 

7-07 

Total  Maltose . . 

48-70 

66-00 

56-88 

Net  Maltose  . . 

28-70 

46-00 

36-88 

Total  Dextrin 

11-88 

21-58 

29-42 

Net  Dextrin  . . 

8-55 

18-25 

26-09 

Total  predigested  Starch,  being  net 
Maltose,  plus  net  Dextrin 

37-25 

64-25 

62-97 

Other  dissolved  Solids 

0-97 

5-71 

6-62 

The  net  maltose  and  dextrin  are  simply  the  total  quantities,  less  a 
deduction  made  for  maltose  and  dextrin  introduced  in  the  extract,  from 


SPECIAL  BREADS  ANB  BREAD-MAKING  PROCESSES.  489 


the  general  composition  of  which  the  amount  to  be  deducted  was  calculated- 
It  uhll  be  noticed  that  in  No.  III.  when  manufacturing  quantities  were 
employed,  and  probably  a longer  mashing,  a much  higher  proportion  of 
the  flour  was  predigested.  In  No.  III.,  the  filtered  soluble  portion  of  the 
mash  contained  neither  starch  nor  amylo-dextrins,  the  proportions  of  dex- 
trin and  maltose  being  as  nearly  as  possible  1 to  4.  In  No.  IV.,  the  filtered 
soluble  portion  contained  traces  of  starch  and  large  quantities  of  unstable 
amylo-dextrins  : the  proportions  of  dextrin  and  maltose  were  approxi- 
mately 1 to  2. 

Bearing  in  mind  the  rapidity  with  which  diastase  acts  on  gelatinised 
starch,  a modification  of  No.  IV.  mash  was  made  in  the  following  manner. 
The  gelatinised  flour  solution  w^as  cooled  to  150°  F.,  and  then  the  cold  malt 
extract  added  and  thoroughly  stirred  in — the  temperature  fell  to  140°  F. 
The  mixture  was  then  heated  as  rapidly  as  possible  by  means  of  a boiling 
water  bath,  and  reached  150°  F.  in  between  two  and  three  minutes.  Half 
the  mixture  was  then  removed,  and  dextrin  and  maltose  at  once  deter- 
mined : the  remainder  was  then  raised  to  165°  F.  and  maintained  at  that 
temperature  for  30  minutes,  after  which  dextrin  and  maltose  were  deter- 
mined, wdth  the  following  results,  which  are  expressed  in  each  case  on  the 
filtered  solution  : — 


First  half  taken  at  150°  F.  Second  half  after  mashing  at  165°  F. 

Dextrin,  9 *120  grams  per  100  c.c.  ..  11*198  grams  per  100  c.c. 

Maltose,  9*309  „ „ ..  9*568 


Practically,  therefore,  almost  the  whole  of  the  conversion  occurs  below 
150°  F.,  and  within  the  first  2 or  3 minutes  after  the  addition  of  the 
extract. 

In  the  next  place,  bread  was  prepared  from  the  mashes  made  by  the 
two*  processes. 

Quantities  Taken. 


Xo.  III.  Mash  prepared  as 
described,  weight  6 lbs.  151-  oz. 

Solids  of  Mash  . . 2 lbs.  7^  oz. 

Water  of  Mash  . . 4 ,,  8 ,, 
Fermented  Sponge  7 „ 0 ,, 

Flour  . . . . 7 ,,  0 ,, 

Salt  . . . . 3 ,, 


No.  IV.  Mash  prepared  as 
described,  w'eight  9 lbs.  1 J oz. 

2 lbs.  7 1 oz. 

6 „ 9i  „ 

7 „ 0 „ 

10  „ 0 „ 

3 „ 


Dough  . . . . 21  lbs.  2J  oz.  . . 26  lbs.  4^  oz. 

Baked  Bread,  about  19*35  lbs.  . . 24*01  lbs. 


The  following  determinations  were  then  made  on  the  bread  : — moisture, 
matter  dissolved  by  treatment  with  water  at  212°  F.  for  2 hours  (mixture 
being  repeatedly  shaken  during  that  time)  ; also  starch,  dextrin,  and  mal- 
tose, each  by  direct  estimation  in  the  filtered  soluble  extract  prepared  as 
previously  described.  The  results  are  given  in  the  first  table  on  the  next  page. 

In  each  case  there  was  an  absence  of  amylo-dextrins.  In  No.  III.  the 
proportions  of  dextrin  and  maltose  were  approximately  as  I to  1,  the  dex- 
trin being  in  slight  excess  ; in  No.  IV.,  as  I to  1*14,  the  maltose  being  in 
slight  excess.  In  both  cases  the  sum  of  the  three  direct  estimations  of 
starch,  dextrin,  and  maltose  exceeds  that  of  the  total  dissolved  matter  by 
direct  weighing  by  1 *63  and  1 *61  respectively  : this  is  doubtless  due  to  the 
fact  that  the  sugar  is  not  wholly  maltose,  but  is  partly  glucose,  produced 
by  the  inverting  action  of  the  yeast  and  the  malt  extract.  Although 
No.  IV.  process  yields  more  dextrin  and  amylo-dextrins  in  the  mash,  yet 
there  is  less  in  the  finished  bread,  as  these  latter  bodies  are  converted  into 


490 


THE  TECHNOLOGY  OF  BREAD-MAKING. 
Percentage  Composition  of  Breads. 


Constituents. 

No.  III. 

No.  IV. 

Moisture 

38-98 

39-19 

Undissolved  Solid  Matter 

40-57 

46-29  1 

1 Dissolved  Matter  by  direct  weighing 

20-45 

14-52 

In  filtered  soluble  extract — 

Starch,  by  direct  estimation  . . 

8-05 

6-08  1 

Maltose  ,, 

6-92 

5-35 

Dextrin  ,, 

7-11 

4-70 

22-08 

16-13  ' 

Net  Maltose  . . 

3-40 

; 1-83 

maltose  and  dextrin  by  the  subsequent  diastatic  action  which  proceeds  in 
the  fermenting  dough.  The  figure  in  the  above  table  called  net  maltose  is 
the  total  maltose,  less  that  calculated  as  due  to  that  naturally  present  in 
bread,  and  introduced  with  the  extract. 

In  the  next  place  a series  of  experiments  was  made,  in  which  bread  was 
prepared  by  processes  Nos.  I.,  II.,  and  III.  The  quantities  and  methods 
of  manipulation  adopted  were  the  same  as  in  the  preceding  experiments, 
except  that  in  Nos.  II.  and  III.  double  the  amount  of  malt  extract  was  taken. 
Some  biscuits  were  also  made,  in  which  the  same  quantity  of  malt  extract 
was  introduced  in  each  case  ; in  one,  simply  as  a condiment,  as  in  No.  II. 
process  ; and  in  the  other,  after  mashing  with  a portion  of  the  flour,  as 
was  done  in  No.  III.  The  following  are  the  results  of  analysis  : — ] 

Analyses  of  Breads  and  Biscuits. 


Constituents. 

Breads. 

1 Biscdits. 

No.  I. 
Plain. 

No.  II. 
Malt. 

No.  III. 
Mont- 
gomerie. 

No.  II. 
Malt. 

No.  III. 
Mont- 
gomerie. 

Maltose 

1-02 

9-11 

14-23 

8-61 

18-46 

Net  Maltose  . . 

— 

2-06 

7-18 

0-00 

8-46 

Total  Soluble  Matter 

3-35 

18-50 

36-24 

18-70 

31-60 

Soluble  Matter,  not  Maltose 

2-33 

9-39 

22-01 

10-09 

13-14 

Net  Soluble  Matter,  not  Maltose  . . 

— 

7-03 

19-68 

— 

— 

Net  maltose  is  in  each  case  that  estimated  to  be  produced  by  diastatic 
action,  after  allowance  for  that  normally  present  in  plain  bread,  and  intro- 
duced in  the  extract. 

There  is  abundant  evidence,  throughout  the  whole  of  these  experiments, 
of  malt  extract  thus  used  producing  a considerable  quantity  of  maltose  over 
and  above  that  introduced  by  the  extract  itself.  It  was  principally  for  the 
purpose  of  measuring  this  effect  that  the  preceding  experiments  were  made. 

Subjoined  are  analyses  of  bread,  biscuits,  and  rusks  made  according  to 
Montgomerie’s  patent. 


SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES.  491 
Analyses  of  Montgomerie’s  Bread,  Biscuits  and  Rusks. 


Constituents. 

Bread. 

Biscuits. 

Rusks. 

Whole. 

Dried. 

Moisture 

38-60 

4-20 

6-90 

Proteins,  Insoluble 

7-85 

12-79 

10-19 

10-54 

,,  Soluble 

0-74 

1-20 

1-24 

1-06 

Starch,  etc.,  undissolved 

39-48 

64-28 

67-03 

60-42 

Maltose  . . 

Soluble  Matter  other  than  Protein  and 

6-22 

10-13 

6-86 

14-22 

Maltose 

5-56 

9-06 

8-96 

6-06 

Phosphoric  Acid,  P2O5.  . 

0-44 

0-73 

0-82 

0-38 

Other  Mineral  Matter  . . 

1-11 

1-81 

0-70 

0-42 

620.  Further  Experiments  on  Diastatic  Action. — In  order  to  study  more 
closely  the  exact  effects  produced  in  bread-making  by  the  action  of  diastase, 
the  following  experiments  were  made  : — Diastase  was  first  extracted  from 
malt  by  Lintner’s  process  of  treating  the  ground  malt  in  the  cold 
for  12  hours  with  20  per  cent,  alcohol  : this  was  filtered  off  and  precipi- 
tated with  concentrated  alcohol.  The  precipitate  was  collected  on  a 
filter,  washed  first  with  absolute  alcohol,  then  with  ether,  and  dried  over 
sulphuric  acid  in  vacuo.  This  preparation  is  termed  malt  diastase.  From 
a sample  of  low-grade  spring  American  flour,  flour  diastase  w'as  prepared 
in  a precisely  similar  manner.  From  malt  a fresh  10  per  cent,  cold-water 
infusion  was  prepared  and  filtered  ; this  is  termed  malt  infusion.  No.  4 
preparation  is  a commercial  product  sold  as  “ diastase,’’  and  obtained  by 
evaporating  a cold-water  infusion  of  malt  to  the  consistency  of  a syrup 
in  vacuo.  The  fifth  was  a high-class  sample  of  guaranteed  pure  malt  extract. 

Their  diastatic  value  was  first  determined  by  Lintner’s  process  on  soluble 
starch,  with  the  following  results  ; — 


Diastatic  Value. 


No.  1. 

Malt  Diastase  . . 

266-6°  Lintner. 

, 2. 

Flour  Diastase  . . 

. . 228-5° 

„ 3. 

Malt  Infusion 

15-6° 

„ 4. 

“ Diastase  ” 

. . 222-2° 

„ 5. 

Malt  Extract 

3-1° 

It  was  decided  to  make  a series  of  baking  tests  with  these  substances, 
taking  such  quantities  as  would  contain  throughout  the  same  number 
of  units  of  diastatic  activity  : knowing  the  diastatic  value  of  each,  it  be- 
comes a matter  of  simple  calculation  to  determine  what  quantities  must 
be  taken  in  order  to  attain  this  object.  Taking  the  malt  diastase  as  a 
standard,  the  amount  of  0T25  gram  was  fixed  on  : the  equivalent  quan- 
tities of  the  others  were  as  follows  ) — 


No.  I.  Malt  Diastase 
,,  2.  Flour  Diastase 
,,  3.  Malt  Infusion 
,,  4.  “ Diastase  ” 

,,  5.  Malt  Extract 


0*125  gram. 
0*145  „ 

21*36  c.c. 
0*153  gram. 
10*75  grams. 


For  baking  tests  the  following  quantities  were  taken  : — 

Flour,  equal  quantities  of  Spring  American  and  English 

wheat  patents  . . . . . . . . . . . . 140  grams. 


492  THE  TECHNOLOGY  OF  BREAD-MAKING. 

Water,  in  which  was  included  solutions  of  the  equivalent 

quantity  of  each  diastatic  body  . . . . . . 80  grams. 

Compressed  yeast  . . . . . . . . . . . . . . 10  ,, 

In  one  series  of  tests,  a,  the  diastatic  ingredient  was  in  its  normally 
active  state  ; in  a second  series,  h,  precisely  similar  in  every  other  respect, 
the  diastase  solution  was  first  placed  in  a boiling  w^ater  bath  for  5 minutes 
with  the  object  of  destroying  the  diastase,  and  subsequently  cooled  prior 
to  mixing  it  in  with  the  flour  and  yeast.  A plain  loaf.  No.  6,  was  also  made 
from  flour,  water,  and  yeast  only. 

The  doughs  were  allowed  to  ferment  at  a moderate  temperature,  and 
the  following  observations  made  on  their  being  ready  to  go  into  the  oven. 
No.  1.  Difference  between  a and  6 very  marked  ; a slacker  and  more  sticky. 
,,  2.  Very  slight  difference,  if  any. 

,,  3.  a,  slightly  sticky,  difference  between  it  and  h not  very  marked. 

,,  4.  Clearly  marked  difference  between  a and  h. 

,,  5.  a,  fairly  stiff,  not  sticky  ; h,  tougher  than  a ; both  brown  in  colour 
as  a result  of  presence  of  extract. 

,,  6.  Plain  loaf.  Compared  with  all  others,  stiff. 

The  loaves  were  baked  in  a moderate  oven  for  45  minutes,  and  were  of 
Coburg  shape,  giving  as  much  facility  foi  expansion  and  formation  of  crust 
as  possible. 

The  following  was  the  character  of  the  crust  : — 

No.  I.  a browner  than  h. 

,,  2.  No  difference  between  a and  h : both  much  like  No.  6. 

,,  3.  d slightly  browner  than  h. 

,,  4.  a slightly  browner  than  h. 

,,  5.  Both  full  brown  in  colour  of  surface,  and  dark  in  breaks  : a browner 
than  h. 

,,  6.  Plain  loaf. 

As  a rule  the  crusts  of  series  a seemed  more  pliable  than  those  of  h. 
Throughout  the  whole  series,  with  the  exception  of  the  No.  2’s,  there  was  a 
distinct  difference  of  flavour  distinguishable  before  the  loaves  were  cut.^ 

The  crumb  of  each  had  the  following  characters  : — 

No.  I.  Good  volume  : a in  centre  sticky  and  gummy  ; h,  better  colour. 
Flavour  in  both  decidedly  swnet,  but  far  more  so  in  a. 

,,  2.  a,  only  slightly  sweeter  than  h ; h,  better  colour,  both  slightly 
darker  than  No.  6. 

,,  3.  u,  sweet  and  malty  ; h,  ditto  in  less  degree,  and  slightly  better  in 
colour. 

,,  4.  a has  more  flavour  than  6,  and  is  also  very  slightly  better  in  colour 
than  h.  Duplicate  loaves  were  baked  with  No.  4 to  see  if  the 
colours  were  relatively  the  same.  Found  h again  to  be  darker 
than  a,  and  of  considerably  less  volume. 

,,  5.  Both  a and  6 were  brown,  with  very  slight  difference  in  colour. 

Flavour  of  h distinctly  that  of  malt  extract.  Flavour  of  a 
different,  being  that  of  malt  extract  wdth  an  additional  flavour 
of  a more  purely  saccharine  character  (doubtless  the  result  of  the 
presence  of  sugars  of  conversion). 

„ 6.  Plain  loaf,  slightly  yeasty  in  flavour. 

A portion  of  each  sample  of  bread  was  taken,  dried  to  a constant  weight 

^ This  is  a somewhat  curious  instance  of  the  baker’s  use  of  the  term  “ flavour  ” : 
baker?  habitually  examine  bread  in  the  first  instance  by  the  smell  of  a loaf,  and  judge 
flavour  through  its  subtle  association  with  smell.  Such  flavour  judgment  may  be 
described  as  “how  the  bread  tastes  to  the  nose.” 


SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES.  493 


in  the  hot-water  oven,  finely  powdered,  and  stored  in  stoppered  bottles. 
A soluble  extract  was  prepared  from  each  in  the  following  manner  : — 10 
grams  of  the  powdered  solids  were  taken  during  the  afternoon,  mixed  with 
100  c.c.  of  cold  water,  and  vigorously  shaken  several  times  during  the  after- 
noon and  evening.  They  were  then  allowed  to  stand  overnight,  and  the 
supernatant -liquid  decanted  in  the  morning,  without  disturbing  the  residue, 
and  filtered.  A portion  of  this  was  evaporated  to  dryness  for  soluble  ex- 
tract, and  the  maltose  determined  in  another  portion.  The  following  are 
the  results  of  analysis  expressed  in  percentages  on  the  dried  solids  : — 


Analyses  of  Diastase  Breads. 


No. 

Variety. 

Soluble  Extracts. 

Maltose. 

a 

b 

a 

b 

a-b 

1 

Malt  Diastase  . . 

27-24 

8-04 

7-83 

2-90 

4-93 

2 

Elour  Diastase  . . 

10-40 

9-65 

1-61 

1-61 

0-00 

3 

Malt  Infusion 

17-75 

10-55 

4-44 

3-63 

0-81 

4 

“ Diastase  ” 

9-20 

6-12 

2-5 

1-13 

1-37 

5 

Malt  Extract 

16-04 

8-76 

5-60 

3-23 

2-37 

6 

Plain  Loaf 

7-60 

— 

1-61 

— 

— 

In  examining  these  results,  the  first  noticeable  point  is  that  in  No.  1, 
5,  there  is  a considerable  quantity  of  maltose  over  that  in  No.  6.  The 
same  is  particularly  observed  also  in  No.  3 : it  would  seem  therefore  that 
the  means  employed  in  order  to  destroy  saccharifying  action  were  not  suffi- 
cient. As  No.  3 was  by  far  the  largest  amount  of  liquid  solution  of  dias- 
tatic  ingredient  acted  on,  its  temperature  was  taken  at  the  end  of  the  five 
minutes  in  the  water-bath,  and  found  to  be  198°  E.  ; at  the  same  time 
there  was  an  abundant  fiocculent  precipitate  of  coagulated  proteins.  That 
the  maltose  in  No.  3,  6,  is  the  highest  of  that  series  also  points  to  insufficient 
heating,  for  the  other  solutions,  which  were  considerably  less  in  volume, 
had  apparently  much  more  of  their  diastatic  action  destroyed. 

The  following  are  the  approximate  percentages  of  maltose  in  each 
bread,  due  to  that  actually  added  in  the  extract  preparation  : — 


No.  1.  Malt  Diastase 
,,  2.  Flour 
,,  3.  Malt  Infusion 
,,  4.  Diastase  . . 

,,  5.  Malt  Extract 


Diastase. 

0-00 

0-00 

0-38 

0*08 

5-10 


In  the  last  case  the  maltose  thus  added  is  very  nearly  the  whole  of  that 
found  in  No.  5,  a,  and  more  than  in  No.  5,  h.  The  mode  of  extraction  em- 
ployed, although  giving  strictly  comparative  results,  does  not  however 
remove  the  whole  of  the  maltose  in  solution  from  the  solids.  The  vesicular 
nature  of  bread,  in  which  the  various  constituents  are  locked  up  within 
films  of  coagulated  protein  matter,  makes  the  entire  extraction  of  the  soluble 
ingredients  a task  of  considerable  difficulty  and  uncertainty.^ 


^ The  plan  of  determining  soluble  extract  in  dried  solids  is  no  doubt  responsible  for 
generally  low  figures.  The  great  advantage  of  the  method  is  that  the  solids  can  be  kept 
in  an  unaltered  form  until  a convenient  time  for  their  analysis  arrives.  This  is  obviously 
impossible  with  moist  breads.  Recently  the  author  has,  in  the  absence  of  enzymes 
(as  in  bread  analysis),  used  the  modification  of  direct  extraction  from  moist  bread. 
He  then  simply  places  the  bread  and  water  together  in  a fiask,  adds  a few  drops  of 
chloroform,  corks  and  shakes,  and  sets  aside  without  fear  of  change  occurring  during 
an  interval  of  waiting.  This  is  particularly  applicable  to  determinations  of  maltose. 


494 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  column  headed  a-b,  gives  the  maltose  due  to  conversion  of  starch 
though  not  necessarily  the  whole  of  such  maltose. 

621.  Highly  Diastatic  Malt  Extracts. — The  preceding  experiments  throw 
a light  on  the  effects  produced  by  highly  diastatic  extracts  during  bread- 
making. Taking  the  column,  a-h,  malt  diastase  prepared  by  extraction 
and  precipitation  from  the  malt  as  described,  effected  the  production  of 
4*93  per  cent,  of  maltose.  Flour  diastase,  the  quantity  of  which  taken  had 
an  equal  diastatic  value  by  Lintner’s  method  on  soluble  starch,  effects 
no  conversion  whatever.  So  also  the  malt  infusion  effects  comparatively 
little  change.  It  will  be  remembered  that  certain  forms  of  diastase  are  able 
to  convert  starch  paste,  while  others  can  only  act  on  soluble  starch  (see 
paragraph  266)  ; raw  grain  diastase  belongs  to  the  latter  group,  and  hence, 
doubtless,  its  inability  to  convert  the  starch  of  flour.  The  diastatic  value 
of  any  preparation  for  bread-making  depends  not  simply  on  its  activity 
as  measured  on  soluble  starch  by  Lintner’s  method,  but  on  its  power  of 
converting  starch  paste,  and  even  the  imperfectly  gelatinised  starch 
occurring  in  bread. 

The  commercial  “ diastase,""  preparation  No.  4,  is  a compound  consist- 
ing essentially  of  the  concentrated  cold-water  extract  of  malt,  so  prepared 
as  to  retain  the  diastatic  activity  of  malt  in  the  highest  possible  degree. 
Various  samples  have  given  a diastatic  capacity  on  Lintner"s  scale  varying 
from  about  220°  in  the  lowest  to  considerably  over  300°  in  the  highest. 
The  following  is  the  result  of  its  analysis  : — 

Analysis  of  “ Diastase.” 


Constituents. 

Whole 

Extract. 

Dried 

Solids. 

Water 

27-90 

_ 

Mineral  Matter  (Phosphates) 

3-32 

4-60 

Proteins 

13-41 

18-60 

Dextrin 

0-40 

8-88 

Sucrose 

2-20 

3-05 

Maltose 

1509 

20-93 

Dextrose  and  Laevulose  . . 

31-68 

43-94 

1 

100-00 

1 

100-00 

1 

Cuprous  Oxide,  CU2O,  from  100  grams 

Reducing  Sugars,  calculated  as  Dextrose  and 

81-75 

113-4 

Lsevulose 

41-09 

56-99 

The  effect  of  this  body  on  bread,  when  taken  in  a quantity  having  the 
same  diastatic  value  as  the  other  substances  tested,  is  much  less  than  that 
of  chemically  prepared  malt  diastase,  though  much  more  than  the  raw 
flour  diastase.  This  concentrated  cold-water  extract  is  therefore  to  be 
differentiated  from  both  pure  malt  diastase  and  raw  grain  diastase  in  its 
effects.  Its  behaviour  indicates  the  presence  of  a considerable  proportion 
of  the  non-liquefying  form  of  diastase.  At  the  same  time  the  true  liquefy- 
ing malt  diastase  is  also  present,  though  not  to  the  same  extent  as  in  the 
ordinary  malt  extract.  No.  5,  which  with  the  same  Lintner  value  on  the 
quantities  taken  gave  a much  higher  production  of  maltose.  But  against 


SPECIAL  BREADS  AND  BREAD-MAKING  PROCESSES.  495 


this  must  be  remembered  the  quantities  actually  used  : of  the  “ diastase  ” 
there  was  only  0'153  gram  as  compared  with  10‘75  grams  of  malt  extract. 
In  giving  a value  to  degrees  Lintner  as  a measure  of  utility  of  a malt  extract 
to  bakers,  it  may  generally  be  concluded  that  an  extract  of  say  120°  Lint- 
ner will  produce  more  maltose  in  bread-making  than  one  of  60°  Lintner, 
but  not  so  much  as  double  the  quantity.  The  extra  diastatic  power  is 
probably  due  in  part  to  liquefying,  and  therefore  saccharifying  diastase, 
and  in  part  to  non-liquefying,  and  therefore  non-effective  diastase. 
The  use  of  2 lbs.  of  the  60°  Lintner  malt  extract  will  as  a general 
rule  in  bread-making  convert  more  starch  into  sugar  than  Avill  1 lb. 
of  the  120°  Lintner  extract.  Further  the  2 lbs.  will  have  imparted  to  the 
bread  all  the  extra  sugar,  dextrin,  etc.,  naturally  present  therein.  It 
must  not  be  forgotten  that  the  flavouring  effect  of  malt  extract  as  a bread 
improver  is  largely  due  to  the  empyreumatic  products  resulting  from  the 
kiln  drying  of  the  malt  itself.  Everything  else  being  equal,  with  less  malt 
extract,  less  of  these  products  will  be  added  to  the  bread.  In  addition,  in 
order  to  secure  a high  degree  of  diastase,  the  malt  is  usually  low  kiln  dried, 
and  so  the  empyreumatic  products  are  only  very  slightly  developed.  The  in- 
troduction of  a small  quantity  of  a highly  diastatic  extract  at  the  dough  stage 
suffices  for  the  conversion  of  a marked  amount  of  starch  into  dextrin  and 
maltose,  thus  conferring  both  moistness  and  sweetness  on  the  bread.  It 
also  exerts  a considerable  action  on  the  proteins  of  flour,  producing  a soften- 
ing effect  on  the  gluten.  In  the  case  where  strong,  harsh,  and  dry  flours 
are  in  use,  the  result  is  to  make  the  resultant  bread  approach  far  more 
closely  in  character  to  that  made  from  softer  and  sweeter  flours.  One  word  of 
caution  may  be  here  introduced  as  to  the  employment  of  these  exceptionally 
powerful  extracts  ; these  preparations  are  so  energetic  as  to  be  capable  of 
carrying  too  far  the  changes  in  starch  and  other  flour  ingredients,  and  thus 
yielding  a wet,  clammy  loaf.  The  obvious  remedy  is  to  employ  the  sub- 
stance in  less  proportion.  The  precise  amount  is  easily  determined  by  a 
very  few  trials. 


622.  Typical  American  High-grade  Yeast  Bread. — ^Wiley  regards  the 
following  as  representing  the  average  composition  of  a bread  of  this  type 


Moisture 
Protein . . 

Ether  Extract . . 
Starch  and  Sugar 
Fibre  . . 

Ash  . . 


35*00  per  cent. 
8*00 
0*75 
54*45 
0*30 
1*50 


The  ash  would  approximately  consist  of  0 *50  per  cent,  derived  from  the 
natural  mineral  ingredients  of  the  flour,  and  1 *0  per  cent,  due  to  the  addition 
of  salt.  The  moisture  may  rise  above  40  per  cent,  in  breads  made  of  flour 
rich  in  gluten,  or  sink  to  30  per  cent,  or  under  when  flour  of  an  inferior  gluten 
content  is  employed.  The  ether  extract  will  vary  according  to  the  amount 
of  milk  or  other  source  of  fat  employed  in  making  the  bread,  or  in  the 
case  of  tin  bread,  in  greasing  the  baking  tin. 

623.  Analyses  of  Commercial  Breads. — The  following  table  gives  the 
results  of  analyses  by  the  authors  of  a number  of  samples  of  bread  recently 
bought  for  that  purpose.  They  are  in  all  cases  ordinary  shop  products, 
and  were  purchased  without  giving  any  intimation  of  the  object  for  which 
they  were  procured,  either  to  the  bakers  or  the  manufacturers  of  the  flours. 


496 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  results  of  the  analyses  are  given  on  the  whole  breads,  and  also  as  cal- 
culated on  the  water-free  solids.  The  energy  in  Calories  is  also  given.  For 
this  purpose  the  whole  of  the  carbohydrates,  including  cellulose,  are  reckoned 
together. 


Names  of  Breads. 

No.  1.  Best  white  bread. 

,,  2.  London  households. 
,,  3.  Whole-meal  bread. 

,,  4.  Bermaline  bread. 

,,  5.  Ho  vis  bread. 

,,  6.  Daren  bread. 

,,  7.  Veda  bread. 

,,  8.  Turog  bread. 


Analyses  of  Commercial  Breads. 


Constituents. 

No. 

1. 

1 

No.  2. 

No. 

3. 

No. 

4. 

As 

Bought. 

Water 

Free. 

As 

Bought. 

Water 

Free. 

As 

Bought. 

W ater 
Free. 

i As 
Bought. 

Water 

Free. 

Moisture 

38-35 

40-00 

44-56 

42-94 

Proteins,  Soluble  . . 

0-42 

0-68 

0-57 

0-95 

0-57 

1-02 

0-35 

0-61 

,,  Insoluble 

6-62 

10-73 

7-93 

13-22 

7-13 

12-87 

1 6-69 

11-72 

Starch,  Cellulose,  etc. 

45-53 

63-79 

40-18 

60-97 

33-25 

37-98 

j 32-39 

56-79 

Maltose 

4-44 

7-22 

3-58 

6-47 

6-70 

12-08 

1 7-03 

jl2-32 

Other  Soluble  Matters 

2-82 

4-65 

5-95 

9-91 

4-29 

7-75 

i 7-78 

13-63 

Phosphoric  Acid  . . 

0-09 

0-15 

0-18 

0-30 

0-46 

0-84 

1 0-42 

0-74 

Other  Mineral  Matter 

0-71 

1-14 

0-50 

0-83 

0-89 

1 50 

0-70 

1-32 

Acidity  as  Lactic  Acid 

0-25 

0-40 

0-24 

0-40 

0-45 

0-81 

0-40 

0-70 

Fat  . . 

0-77 

1-24 

0-57 

1-95 

1-75 

3-15 

1-30 

2-27 

Energy  in  Calories 

251-7 

— 

243-9 

— 

229-2 

— 

234-5 

— 

No. 

.5. 

No. 

6. 

No. 

7. 

No. 

8. 

Moisture  . . 

47-81 

— 

45-02 

— 

32-57 

— 

46-82 

— 

Proteins,  Soluble  . . 

0-35 

0-67 

1-17 

2-12 

0-90 

1-33 

0-58 

1-09 

,,  Insoluble 

9-26 

17-74 

7-83 

14-41 

8-49 

12-59 

8-72 

16-39 

Starch,  Cellulose,  etc. 

27-20 

52-35 

26-97 

44-16 

24-38 

38-20 

36-68 

68-97 

Maltose 

6-46 

! 12-37 

6-81 

11-22 

19-87 

29-57 

> 3-40 

6-39 

( )ther  Soluble  Matters 

6-15 

11-80 

12-22 

23-06 

20-03 

29-81 

1-78 

3-35 

Phosphoric  Acid  . . 

0-43 

0-83 

0-56 

1 02 

0-41 

0-61 

0-39 

0-74 

Other  Mineral  Matter 

0-60 

1-13 

0-72 

1-31 

0-59 

0-87 

0-53 

0-99 

j Acidity  as  LacticAcid 

0-43i 

0-82 

0-40 

0-72 

0-51 

0-75 

0-50 

0-95 

Fat 

1 -30l 

2-49 

1-20 

2-00 

0-25 

0-37 

0-60 

1-13 

Energv  in  Calories 

1 

214-7  i 

i 

— 

239-0 

■ — “ i 

304-3 

— 

215-3 

1 

CHAPTER  XX 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 

624.  Agricultural  Improvement  of  Wheat. — Among  the  various  endea- 
vours made  to  improve  the  quality  of  bread  as  a food,  the  first  in  order  of 
natural  sequence  are  those  directed  to  the  improvement  of  the  wheat  itself. 
Conspicuous  among  these  is  the  work  of  the  Home-grown  Wheat  Com- 
mittee of  the  National  Association  of  British  and  Irish  Millers,  which  for 
some  years  has  devoted  itself  to  the  improvement  of  English  wheat.  Credit  for 
such  patriotic  work  is  largely  due  to  Humphries,  Biffen,  and  Wood,  by  whom 
most  of  the  requisite  extensive  researches  have  been  conducted.  English 
wheats  had  been  deteriorating  in  strength,  and  to  remedy  this  defect  experi- 
ments were  made  in  the  direction  of  selection  of  seed,  and  hybridisation, 
in  order  to  secure  stronger  varieties.  As  necessary  factors  in  strength  a 
sufficiency  of  gluten,  and  of  gluten  of  good  quality,  are  required.  Wood's 
most  recent  investigations  go  to  show  that  strength  is  associated  with  the 
presence  of  certain  mineral  salts  in  the  grain,  the  principal  of  which  is  a 
relatively  high  percentage  of  water-soluble  phosphates.  If  this  should  be 
completely  demonstrated,  the  obvious  course  will  be  first  to  secure  a suffi- 
ciency of  soluble  phosphates  in  the  soil  ; and  then  to  use  as  seed  wheats 
those  which  have  a natural  selective  preference  for  such  phosphates.  By 
cross-breeding  and  careful  selection  it  may  also  be  possible  to  induce  their 
absorption  by  other  varieties  of  the  grain. 

625.  Treatment  of  Wheat  by  Water-soluble  Phosphates,  Chitty  and  Jago. — 

This  subject  has  been  approached  by  the  above-named  investigators,  who 
have  been  granted  a patent.  No.  22,434,  1909,  for  a process  of  treating  wheat 
by  soaking  the  grain  in  a solution  of  phosphoric  acid  or  other  soluble  phos- 
phates. In  their  specification,  the  patentees  state  that  a very  marked 
improvement  is  thus  effected  in  certain  wheats  mentioned.  Such  treat- 
ment specially  increases  the  strength  of  the  wheats.  It  would  seem,  there- 
fore, that  not  only  are  wheats  favourably  affected  by  a naturally  high  water- 
soluble  phosphate  content,  but  they  are  also  similarly  improved  by  the 
addition  of  such  phosphates  in  appropriate  form  to  the  grain. 

626.  Application  of  Moist  Heat  to  Grain  and  Flour,  Simon. — In  1908, 

a patent  was  granted  to  Henry  Simon,  Ltd.,  No.  9,946,  for  improvements 
in  conditioning  flour  by  treatment  with  moisture-laden  air.  One  of  the 
objects  of  the  invention  is  the  replacement  of  such  natural  moisture  of  the 
wheat  as  is  removed  during  the  operations  of  milling.  Air  is  raised  in 
temperature  by  passage  through  heated  pipes  and  then  conducted  into  a 
chamber  in  which  water  is  being  sprayed.  The  hot  air  is  thus  charged 
with  moisture,  and  is  next  led  into  the  fully  milled  flour  as  it  passes  through 
an  apparatus  in  which  it  is  kept  in  a state  of  agitation.  The  proportion  of 
water  in  the  flour  is  thus  increased  by  OT  per  cent,  or  more  according  to 
requirements.  It  is  claimed  that  at  the  same  time  the  flour  is  conditioned, 
that  is,  is  improved  in  its  baking  qualities.  As  flour  may  easily  vary  in 
moisture  content  within  a range  of  as  much  as  I -0  per  cent,  as  the  result  of 
the  relative  dryness  or  humidity  of  the  atmosphere,  it  is  difficult  to  see 


498 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


where  an  increase  of  OT  per  cent,  of  moisture,  qua  moisture,  can  effect  any 
material  improvement  in  the  flour.  Investigation  by  the  authors  has  shown, 
however,  that  with  certain  flours  improvement  in  baking  qualities  does,  as  a 
matter  of  fact,  follow  the  treatment.  The  suggestion  is  made  that  it  is 
the  heat,  together  with  the  moisture,  by  which  the  improvement  is  effected. 

627.  Spraying  Treatment  of  Wheaten  Stock  and  Flour,  Humphries. — 

In  June,  1908,  an  application.  No.  13,135,  was  made  for  a patent  by  Hum- 
phries for  an  invention  essentially  consisting  of  the  introduction  of  various 
ingredients  into  flour  in  the  form  of  a very  finely  divided  spray.  The 
patentee  prefers,  however  to  apply  his  spray  to  stock,  as  during  the  subse- 
quent stages  of  milling  it  is  then  more  thoroughly  mixed  with  the  flour. 
When  the  stock  is  thus  sprayed,  even  with  water  alone,  there  is  stated  to 
be  an  improvement  in  the  colour  of  the  flour.  During  the  spraying  opera- 
tion the  flour  or  stock  require  to  be  kept  in  motion  by  some  suitable  appliance. 
Not  only  may  water  be  thus  introduced,  but  other  beneficial  ingredients 
either  dissolved  or  finely  suspended  in  the  water  may  be  added.  Among 
the  substances  thus  capable  of  introduction,  the  patentee  suggests  the 
following  : — 

(а)  Yeast  foods. — For  example  an  aqueous  solution  of  diastase,  contain- 
ing diastase  equal  to  about  0-02  per  cent,  of  the  flour,  or  solutions  of  maltose 
and  dextrin,  or  of  nitrogenous  yeast  foods. 

(б)  Substances  affecting  'physical  characteristics  of  the  flour. — These  im- 
prove the  dough,  and  may  consist  of  solutions  of  appropriate  mineral  salts 
u,s  those  of  potassium,  calcium  or  magnesium,  or  an  acid  such  as  phosphoric 
u^cid. 

(c)  Retarding  agents. — These  may  be  used  for  checking  fermentation 
■or  excessive  effect  of  enzymes,  so  as  to  improve  stability.  Examples  are 
a dilute  solution  of  potassium  carbonate,  or  a solution  of  common  salt,  or  the 
like. 

Formulae  are  given  of  quantities,  and  best  mode  of  applying  these  various 
reagents. 

The  application  for  this  patent  was  the  result  of  a prolonged  investiga- 
tion of  the  conditions  affecting  the  quality  of  wheaten  flour.  The  starting- 
point  was  the  discovery  that  the  soluble  matters  of  bran  were  found  capable 
■of  improving  such  flour.  A water  extract  of  bran  contains  mineral  salts, 
among  which  are  phosphates  of  lime,  magnesia,  and  potash,  and  in  smaller 
quantities  sulphates  and  chlorides.  In  addition  there  are  sugar  and  pro- 
teins, the  latter  possessing  considerable  diastatic  activity.  With  the  wide 
variations  in  the  characteristics  of  different  wheats,  it  was  found  that  a 
selection  from  among  these  was  necessary  in  order  to  obtain  the  greatest 
improvement  possible  with  each  variety.  Thus  with  those  deficient  in 
sugar,  an  addition  of  saccharine  constituents  is  obviously  indicated.  In 
Humphries’  opinion,  some  wheats  are  not  only  deficient  in  ready-formed 
sugars,  but  also  in  sufficient  diastase  to  produce  such  sugar  as  is  necessary 
during  fermentation  ; here  the  introduction  of  some  diastatic  body  is 
■desirable.  With  certain  peculiarly  hard  and  intractable  glutens,  he  regards 
the  addition  of  suitable  enzymes  as  being  of  considerable  service.  Where, 
on  the  other ‘hand,  these  enzymes  are  naturally  in  excess,  with  a tendency 
of  the  gluten  to  become  runny,  some  retarding  agent  is  of  advantage. 
Among  these  are  such  substances  as  common  salt  and  potash,  either  in  the 
form  of  hydroxide  or  carbonate.  In  whichever  form  added,  the  carbon 
dioxide  of  fermentation  causes  the  resultant  body  to  be  a carbonate.  Again, 
Wood  has  shown  that  a serious  defect  of  certain  wheats  is  the  deficiency  of 
certain  mineral  salts,  and  this  may  be  remedied  by  adding  appropriate 
salts  such  as  those  of  potassium,  calcium,  or  magnesium.  As  a stimulant 


WHEAT,  ELOUR,  AND  BREAD  IMPROVERS. 


499 


to  yeast  action,  such  a body  as  ammonium  phosphate  is  at  times  particularly 
useful  either  by  itself  or  in  combination  with  malt  extract.  The  result  is 
a good  fermentation  from  flours  made  from  wheats  which  have  been  grown 
in  very  hot  dry  conditions  of  atmosphere  and  soil.  Humphries  also  insists 
on  the  importance  of  affecting  the  physical  condition  of  flour,  even  by 
the  use  of  water  only,  so  that  the  natural  or  added  ferments  may  operate 
to  maximum  advantage  in  panary  fermentation.  In  other  cases  he 
would  reduce  the  percentage  of  water  in  wheat  before  grinding  with  the 
same  object. 

In  the  application  of  these  various  reagents,  Humphries  prefers  the 
employment  of  their  solution  in  the  form  of  spray,  as  thereby  an  exceedingly 
intimate  admixture  of  the  substances  with  the  flour  is  obtained.  For 
the  same  reason  he  prefers  to  make  the  addition  in  the  earlier  intermediate 
stages  of  milling;  as  the  following  grinding  processes  serve  to  effect  a very 
close  combination  with  the  flour. 

As  to  the  effect  of  the  water  itself,  employed  as  a carrier  of  the  different 
substances  used  in  the  spray,  Humphries  in  the  first  place  insists  that  only 
a very  small  proportion  is  needed  or  desirable,  and  certainly  no  such  amount 
as  seriously  increases  the  water  content  of  the  flour.  This,  he  finds,  will, 
■enable  the  pressure  on  the  rolls  during  grinding  to  be  considerably  dimin- 
ished, and  consequently  the  temperature  of  the  ground  stock  is  substantially 
lessened.  With  this  reduction  in  temperature,  the  amount  of  moisture 
given  off  in  grinding  is  decreased,  and  the  subsequent  condensation  or  “ sweat- 
ing inside  roller  mills  and  dressing  machines,  and  “ pasting  up  of  silks 
is  much  diminished  or  entirely  abolished.  It  is  a well-known  and  practically 
necessary  practice  in  milling  to  condition  hard  wheats  by  the  addition  of 
water,  and  Humphries  believes  such  addition  in  certain  cases  to  be  prefer- 
able after  the  removal  of  the  germ  and  the  bran,  as  thereby  the  percentage 
of  unstable  products  introduced  into  the  flour  from  these  bodies  is  reduced. 
Finally,  he  submits  that  the  materials  added  to  the  flour  are  desirable  food- 
stuffs, and  such  as  are  themselves  natural  to  wheat,  flour  or  bread. 

On  behalf  of  the  German  Patent  Office,  an  official  investigation  of 
the  Humphries’  process  has  been  made,  whose  report  has  been  placed  at 
the  disposal  of  the  authors.  They  regard  the  process  as  of  great  value,  and 
state  that  their  baking  tests  show  a greater  elasticity  of  the  dough  in  the  case 
■of  the  treated  flours,  which  they  regard  as  a material  improvement.  In 
addition  to  this,  there  is  a better  browning  of  the  crust  and  a very  large 
increase  in  the  volume  of  the  bread. 

628.  Flour  Improvers,  Manufacture  of  Phosphates. — Under  this  name 
may  be  included  any  preparations  offered  to  or  used  by  the  miller  for  the 
treatment  of  flour,  as  distinct  from  processes  such  as  already  described. 
The  principal  substance  of  this  type  is  the  acid  phosphate  of  calcium,  in 
addition  to  which  there  are  other  soluble  phosphates.  Being  white  powders, 
these  bodies  do  not  injuriously  affect  the  colour  of  the  flour. 

In  view  of  the  circulation  of  certain  recklessly  inaccurate  statements  as 
to  the  source  and  mode  of  manufacture  of  phosphates,  it  has  been  thought 
well  to  place  a definite  description  of  same  on  record.  Bones  consist  largely 
of  calcium  phosphate  and  carbonate  together  with  a certain  amount  of 
organic  matter.  On  the  addition  of  the  requisite  amount  of  sulphuric 
acid  to  ground  bones  the  phosphate  is  converted  into  the  soluble  form  thus: — 

Ca3(P04)3  + 2HBO4  = CaH4(P04).  + 2CaS04. 

Calcium  Sulphuric  Calcium  Calcium 

Phosphate.  Acid.  Hydric  Phosphate  Sulphate. 

(Superphosphate ). 

It  will  be  noticed  that  the  sulphuric  acid  as  such  has  entirely  disappeared, 
having  been  converted  into  the  sulphate.  For  manurial  purposes,  bones  are 


500 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


treated  in  this  manner,  and  the  whole  mixture  offered  as  “ dissolved  bones 
or  “ vitriolised  bones.""  This  preparation  is  very  valuable  for  the  purpose 
for  which  it  is  intended  ; but,  in  common  with  many  other  manures, 
possesses  such  an  objectionable  smell  and  taste  as  to  render  it  absolutely 
impossible  as  a constituent  of  food. 

For  food  and  medicinal  purposes,  the  principal  source  from  which  Great 
Britain  derives  its  raw  material  for  the  manufacture  of  phosphorus  com- 
pounds is  the  cattle-raising  districts  of  South  America.  The  bones  from 
the  slaughtered  carcases  are  first  treated  for  the  extraction  of  glue,  after  which 
the  mineral  matter  is  burned  or  calcined  at  a white  heat,  and  to  a white 
ash,  known  as  bone  ash.  This  consists  of  the  before-mentioned  phosphates, 
and  lime  from  the  carbonates,  and  is  free  from  organic  matter.  After 
importation  the  ash  is  treated  with  arsenic -free  sulphuric  acid,  manufac- 
tured from  sulphur  as  distinct  from  pyrites.  The  phosphate  undergoes  the 
same  change  as  before  described,  with  the  total  disappearance  of  any  free 
sulphuric  acid.  The  soluble  phosphate  is  then  separated  more  or  less  com- 
pletely from  the  calcium  sulphate ; or  for  the  cheaper  grades  the  two  are 
sold  together,  hence  the  high  percentage  of  calcium  sulphate  in  the  low 
grade  phosphates.  An  article  of  a high  degree  of  purity  is  obtained  by 
treating  the  bone  ash  with  phosphoric  acid  instead  of  sulphuric  acid.  The 
change  then  becomes  : — 

Ca3(P04)2  + 4H3PO4  = 3CaH4(P04)2. 

Calciuni  Phosp'ioric  Calcium  Hydric  Phosphate. 

Phosphate.  Acid.  (Acid  Phosphate). 

Tlie  phosplioric  acid  may  be  prepared  by  burning  phosphorus  in  air 
in  the  presence  of  water,  or  by  treatment  of  bone  ash  with  sufficient  sulphuric 
acid  to  convert  the  whole  of  the  lime  into  calcium  sulphate.  By  the  use  of 
properly  made  phosphoric  acid  it  is  possible  to  obtain  a phosphate  which 
may  be  sold  under  a guarantee  of  freedom  from  arsenic,  and  as  containing 
not  more  than  2 per  cent,  of  calcium  sulphate.  Bakers  are  strongly  recom- 
mended to  insist  on  the  supply  of  phosphate  of  this  degree  of  purity,  and 
to  refuse  acceptance  of  any  lower  quality. 

With  the  view  of  increasing  the  diastase  of  the  flour,  it  has  been  pro- 
posed to  add  small  quantities  of  highly  diastatic  malt  flour.  Unless  very 
finely  dressed  such  a preparation  will  cause  the  flour  to  look  “ specky."" 

629.  Chemical  Changes  produced  in  Flour  by  Bleaching,  Monier- Williams. — • 

A note  was  inserted  at  the  end  of  Chapter  XVII.,  page  399,  to  the  effect 
that  reports  on  flour  bleaching  and  flour  improvers  had  been  published  by 
the  Local  Government  Board.  As  most  of  the  book  was  then  in  type,  it 
was  only  found  possible  to  arrange  for  a reference  to  these  reports  in  this 
place.  An  extended  experimental  investigation  was  conducted  by  Monier- 
Williams.  A summary  of  his  more  important  conclusions  follows  : — • 

“ Summary  of  Results. 

The  action  of  air  containing  nitrogen  peroxide  upon  flour,  in  quantities 
up  to  300  c.c.  of  nitrogen  peroxide  to  one  kilogram  of  flour,  may  be  summar- 
ised as  follows  : — 

I.  The  golden-yellow  tint  of  the  flour  is  destroyed.  Immediately  after 
bleaching  no  difference  in  tint  due  to  excess  of  the  bleaching  agent  could 
be  observed  with  Lovibond’s  tintometer,  but  on  keeping  for  several  days 
the  more  highly  bleached  samples  became  decidedly  yellow,  while  those 
treated  with  30  to  100  c.c.  of  nitrogen  peroxide  per  kilogram  became  still 
whiter,  the  maximum  of  bleaching  effect  being  attained  within  these 
limits. 

II.  The  amount  of  nitrous  acid  or  nitrites  present  in  a freshly  bleached 


WHEAT,  ELOUE,  AND  BREAD  IMPROVERS. 


501 


flour  is  approximately  proportional  to  the  amount  of  nitrogen  peroxide 
employed,  and  eorresponds  to  about  30  per  cent,  of  the  total  nitrogen  ab- 
sorbed, rising  to  40  per  cent,  in  the  more  highly  bleached  samples.  After 
the  lapse  of  several  days,  the  proportion  of  nitrites  present  decreases  con- 
siderably in  the  higher  concentrations,  but  remains  very  nearlj^  the  same 
in  the  more  slightly  bleached  samples. 

III.  Approximately  60  per  cent,  of  the  total  nitrogen  introduced  as 
nitrogen  peroxide  into  the  flour  during  bleaching  can  be  recovered  as  am- 
monia a short  time  after  bleaching  by  reducing  the  aqueous  extract  of  the 
flour  with  a copper-zinc  couple,  and  may  be  assumed  to  be  present  in  the 
flour  as  nitric  and  nitrous  acids  or  as  nitrates  and  nitrites.  After  keep- 
ing the  bleached  flour  for  some  days  the  amount  of  nitric  acid  extracted 
with  cold  water  decreases.  Experiments  with  pure  glutenin  and  gliadin 
indicated  that  in  certain  circumstances  nitric  acid  may  be  withdrawn  from 
solution  or  ‘ adsorbed  ’ by  these  proteins. 

IV.  In  highly  bleached  flour  a considerable  increase  in  the  amounts  of 
soluble  proteins  and  soluble  carbohydrates  takes  place.  If  one  kilogram 
of  flour  is  bleached  with  300  c.c.  of  nitrogen  peroxide,  the  amount  of  soluble 
nitrogen  is  doubled.  This  appears  to  be  due  almost  entirely  to  the  solu- 
bility of  gliadin  in  nitric  acid  of  certain  concentrations.  The  simultaneous 
increase  of  soluble  carbohydrates  would  seem  to  point  to  an  intimate  relation- 
ship between  the  gliadin  and  certain  carbohydrates  in  flour. 

V.  If  highly  bleached  flour  is  allowed  to  stand  for  some  time  after 
bleaching,  the  oil  undergoes  very  considerable  alteration  and  acquires  the 
characteristics  of  an  oxidised  oil.  About  6 to  7 per  cent,  of  the  nitrogen 
introduced  as  nitrogen  peroxide  during  bleaching  is  absorbed  by  the  oil. 

VI.  The  absorption  of  nitrogen  peroxide  by  flour  does  not  appear  to  be 
accompanied  by  I the  production  of  free  nitrogen,  nor  was  any  evidence 
obtained  of  the  formation  of  diazo-compounds. 

VII.  Sodium  nitrite  was  found  to  exert  no  inhibitory  action  on  the 
digestion  of  soluble  starch  by  saliva,  but  the  rate  of  digestion  was  greatly 
retarded  if  the  starch  had  been  previously  treated  with  nitrogen  peroxide 
gas.  Bleaching  was  found  to  exercise  an  inhibitory  effect  on  the  salivary 
digestion  of  flour.”  {Reports  to  Local  Government  Boards  New  Series,  No.  49, 
April,  1911). 

I ! The  above  report  may  be  very  profitably  compared  with  the  results  of 
Snyder’s  investigations,  paragraph  518.  It  will  be  noticed  that  Snyder 
made  his  digestion  experiments  on  human  subjects  with  bread  from  un- 
bleached and  bleached  flours,  whereas  Monier- Williams  made  artificial 
digestion  tests  with  the  respective  flours. 

630.  Flour  Bleaching  and  “Inproving,”  Hamill. — In  response  to 
instructions  from  the  Local  Government  Board,  Hamill  has  inquired  into 
the  practices  of  flour  bleaching,  and  the  adding  thereto  of  improvers,  and 
has  made  a report  to  the  Board  of  which  the  following  are  the  principal 
conclusions.  Various  methods  of  treatment  of  flour  on  these  lines  are 
described  in  detail,  including  nitrogen  peroxide  and  ozone  bleaching  pro- 
cesses. He  then  goes  on  to  state  that — 

“ Flour  has  also  been  treated  with  sulphuryl  chloride,  sulphur  trioxide 
and  chlorine,  and  other  similar  mixtures,  but  I am  informed  that  the  results 
have  not  been  encouraging.  Sulphuryl  chloride  is  stated  to  improve  the 
strength  of  flour,  but  the  sulphur  trioxide  and  chlorine  mixture  is  uncertain 
in  action,  and  is  usually  without  any  beneficial  effect  on  the  baking  qualities 
of  flour.  In  practice  the  odour  which  these  substances  impart  to  the  flour 
precludes  their  use  as  ‘ improvers.’ 

In  some  recent  patents  it  is  proposed  to  treat  flour  with  phosphorus 


502 


THE  TECHNOLOGY  OF  BREAD-MAIvING. 


trichloride,  pentachloride  or  other  halogen  compounds  of  phosphorus,  or 
with  a mixture  of  these  and  sulphur  trioxide,  nitric  acid,  nitrous  acid,  iodic 
or  other  halogen  acids  ; also  formic,  acetic,  propionic  or  benzoic  acids, 
alcohol,  aldehydes,  or  ketones,  with  the  object  of  strengthening  the  flour 
and  improving  its  baking  qualities.  It  has  further  been  proposed  to  treat 
flour  with  phosphorus  pentoxide,  phosphorus  bisulphide,  and  phosphorus 
pentasulphide,  and  the  process  has  been  patented. 

Although  much  experimentation  of  an  empirical  kind  is  proceeding,  in 
the  course  of  which  a variety  of  heterogeneous  substances  may  be  added  to 
flour,  it  may  be  said  that  apart  from  nitrogen  peroxide  the  only  substances 
whose  use  as  yet  has  been  attended  with  any  measure  of  commercial  success 
are  certain  acids  and  salts,  more  particularly  phosphoric  acid  and  phos- 
phates.” 

In  summarising  the  effects  of  both  bleaching  and  the  use  of  improvers, 
Hamill  goes  over  much  of  the  ground  already  dealt  with  in  the  seventeenth 
and  present  chapters.  Omitting  these  matters  of  history  the  following  are 
his  most  important  conclusions  : — ■ 

“ Bleaching  and  so-called  Flour  ‘ Improving  ’ in  relation  to 

Public  Health  and  the  General  Interests  of  the  Consumer. 

Bleaching  hy  Nitrogen  Peroxide. 

Dr.  Harden  shows  that  under  the  conditions  in  which  his  experiments 
were  conducted  no  obvious  effects  were  produced  on  animals  fed  with  highly 
bleached  flour  or  with  aqueous  extracts  of  such  flour. 

Dr.  Harden’s  report  also  contains  an  account  of  experiments  in  regard 
to  peptic  and  pancreatic  digestion  of  bleached  and  unbleached  flour ; and 
Dr.  Monier-Williams  gives  corresponding  results  with  salivary  digestion. 
From  these  it  appears  that  bleaching  has  a distinctly  inhibitory  effect  on 
peptic  digestion,  but  no  observable  effect  on  the  pancreatic  (proteolytic) 
digestion  of  flour.  Sodium  nitrite  was  found  to  exert  no  inhibitory  effect 
on  the  salivary  digestion  of  starch,  but  in  the  case  of  starch  treated  with 
nitrogen  peroxide,  digestion  was  greatly  retarded.  Bleaching  was  also 
found  to  exercise  an  inhibitory  effect  on  the  salivary  digestion  of  flour. 

As  regards  the  action  of  nitrites  on  the  system,  it  should  be  remembered 
that  nitrites  when  administered  as  drugs,  produce  various  effects,  amongst 
which  disturbance  of  the  heart  and  vascular  system  are  prominent.  The 
amounts  of  nitrite  introduced  by  bleached  flour  would  be  of  a much  lower 
order  than  those  taken  when  nitrites  are  given  medicinally.^  Statements 
have  been  made,  however,  by  medical  practitioners  that  an  appreciable 
effect  may  be  produced  by  quite  small  doses  of  nitrite  : Gustav  Mann 
points  out  that  quantities  such  as  half  a grain  (32  milligrams)  of  nitrous 
acid  may  be  harmful  to  some  individuals.  What  may  be  the  physiological 
or  pathological  effect  of  ingestion  of  even  smaller  doses  when  taken  day  by 
day  throughout  many  months  or  years  it  is  impossible  to  say  ; there  is  no 
evidence  on  the  matter,  and  it  would  be  very  difflcult  to  obtain  any.  It 
cannot,  however,  be  regarded  as  desirable  that  minute  doses  should  be  in- 
gested day  by  day  of  a drug  which  in  larger  single  doses  has  a marked  action 
on  the  vascular  system. 

It  would  appear  from  experimental  and  other  considerations  to  which 
reference  has  already  been  made,  that,  apart  from  the  addition  of  nitrites, 
the  constitution  of  flour  may  be  altered  by  bleaching.  Dr.  Monier-Wil- 
liams has  clearly  shown  in  his  report  that  the  oil  of  flour  undergoes  a marked 
change  : it  has  been  suggested  by  Folin  that  nitration  of  the  flour  oil,  if 

‘The  phariTiacopoeial  dose  of  sodium  nitrite  is  1 to  2 grains,  and  of  nitro-glycerin 
(in  Liquor  Trinitrini)  to  -Aj  grain. 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 


503 


it  occurs,  might  entail  risk  to  health,  since  absorption  of  the  oil  and  its 
oxidation  in  the  tissue  might  occur,  resulting  in  the  liberation  of  nitrites. 
Ozone  produced  together  with  nitrogen  peroxide  in  certain  bleaching  pro- 
cesses also  exerts  a markedly  destructive  action  on  olein,  one  of  the  constitu- 
ents of  flour  oil.  In  sj^ite  of  assertions  to  the  contrary  there  seems  to  be 
evidence  pointing  to  the  possibility  of  the  protein  constituents  of  flour  being 
adversely  affected  as  the  result  of  bleaching.  Dr.  Monier- Williams  has 
shown  that  the  solubility  of  the  proteins  and  also  of  the  carbohydrates  is 
increased  by  such  treatment.  These  changes  in  the  oil,  the  protein  and  the 
carbohydrates  are,  of  course,  more  marked  when  flour  is  overbleached,  and 
though  over  bleaching  is  not  likely  nowadays  to  occur  throughout  the  whole 
of  the  flour,  local  overbleaching  may  take  place,  portions  of  flour  adhering 
to  the  sides  of  the  agitator  and  flour  spouts  may  become  overbleached  and 
contaminate  to  some  extent,  at  any  rate,  the  rest  of  the  flour. 

Looking  to  the  above  considerations,  it  may  be  concluded  that  the 
alterations  in,  and  the  additions  to,  flour  which  result  from  a high  degree  of 
bleaching  by  nitrogen  peroxide  cannot  be  regarded  as  free  from  risk  to  the 
consumer,  especially  when  regard  is  had  to  the  inhibitory  effect  of  the  bleach- 
ing agent  on  digestive  processes  and  enzymes.  Even  in  the  case  of  flour 
which  is  bleached  to  the  small  extent  which  is  at  present  ordinarily  prac- 
tised, it  would  in  present  knowledge  be  unwise  to  conclude  that  the  process 
is  attended  by  absolute  freedom  from  risk.  The  fact  that  bleached  flour 
has  been  shown  to  be  something  more  than  natural  flour,  the  colour  of  which 
has  been  modifled,  is  also  of  importance  in  considering  whether  bleached 
flour  may  properly  be  represented  as  genuine  flour. 

The  practice  of  bleaching  being  open  to  these  objections,  it  remains  to 
inquire  whether  the  consumer,  who  at  present  is  seldom  aware  that  his  flour 
has  been  bleached,  or  that  his  bread  is  made  from  bleached  flour,  can  bo 
said  to  obtain  any  compensating  benefit.  To  this  a negative  answer  must 
be  given. 

Apart  from  any  dietetic  considerations  a large  number  of  people  desire 
bread  of  exceptional  whiteness,  and  it  is  reasonable  to  suppose  that  what 
is  demanded  by  those  who  prefer  such  bread  is  an  article  made  from  flour, 
the  whiteness  of  which  is  due  to  its  being  prepared  from  specially  selected 
wheats  by  the  elaborate  mechanical  separation  and  ‘ purification  ’ of 
modern  milling  methods.  Few  people  would  carry  their  approval  of  white- 
ness to  the  extent  of  requiring  naturally  dark  flour  to  be  chemically  treated. 

So-called  ‘ Flour  Improvers.’’ 

Many  of  the  above  considerations  apply  also  to  the  addition  of 
‘improvers"  to  flour.  These  articles  can  hardly  be  regarded  as  proper 
constituents  of  what  is  represented  to  be  genuine  flour  in  this  country. 

Those  interested  in  these  preparations  advocate  their  use  on  the  grounds 
that  they  add  nothing  to  the  flour  that  is  not  normally  present  therein, 
and  that  they  increase  the  lightness  and  improve  the  quality  and  appear- 
ance of  the  loaf,  and  also  permit  of  more  loaves  being  made  from  a given 
quantity  of  flour.  The  first  of  these  contentions  is  based  on  the  assumption 
that  phosphorus  in  flour  is  present  in  the  form  of  phosphate,  chiefly  potas- 
sium phosphate.  This  is  not  so  ; it  is  true  only  of  the  ash  of  flour.  A large 
portion  of  the  phosphorus  in  flour  is  present  in  organic  combination,  and 
experimental  evidence  exists  which  would  seem  to  indicate  that  phosphorus 
in  this  form  may  possess  a dietetic  value  quite  different  from  inorganically 
combined  phosphorus.  This  is  recognised  by  certain  millers,  and  it  is  sug- 
gested that  such  organic  phosphorus  compounds  may  be  formed  when  solu- 
tions containing  phosphates  are  intimately  mixed  with  flour  in  the  form  of 
a fine  spray  from  an  ‘ atomiser.’  No  evidence  is  adduced  in  favour  of  this 


504 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


contention,  and  it  may  suffice  to  say  that  the  formation  of  complex  organic 
phosphorus  compounds  in  this  way  is  contrary  to  experience. 

The  second  advantage  claimed,  namely,  the  increased  loaf  production 
from  a given  quantity  of  flour,  is  one  which  will  appeal  only  to  the  miller 
and  baker.  The  gain  in  production  is  due  to  the  increased  amount  of 
water  which  the  flour  absorbs  and  to  the  increase  in  volume  of  the  dough, 
resulting  from  the  improved  elasticity  of  the  gluten.  This  naturally  means 
a diminution  in  the  actual  amount  of  flour  in  each  loaf,  and,  consequently, 
in  nutritive  value,  so  that  the  consumer  in  this  respect  loses  by  the  treat- 
ment. 

The  protein  content  of  flour  is  an  important  matter  from  the  standpoint 
of  nutrition,  especially  where  bread  enters  largely  into  a diet.  Flour  from 
weak  wheats,  which  are  generally  poor  in  gluten,  contains  less  protein  than 
flour  from  strong  wheats  which  are  rich  in  gluten.  But  by  the  use  of  ‘ im- 
provers ’ flour  from  weak  wheat  is  made  to  simulate  flour  from  a stronger 
wheat,  although  as  regards  protein  content  it  is  inferior  to  the  flour  which 
it  imitates. 

With  regard  to  other  substances  which  have  been  represented  as  ‘ im- 
provers,’ it  may  be  said  that  the  indiscriminate  addition  of  powerful  chemical 
substances  such  as  hydrofluoric  acid,  phosphorus  pentachloride,  and  the 
oxides  and  sulphides  of  phosphorus  to  flour  is  most  dangerous. 

The  increasing  activity  which  is  now  being  displayed  in  the  use  of  dif- 
ferent articles  as  additions  to  flour  must  be  regarded  with  considerable 
apprehension.  It  does  not  appear  desirable  that  such  an  indispensable 
foodstuff  as  flour,  the  purity  and  wholesomeness  of  which  are  of  first  im- 
portance to  the  community,  should  be  manipulated  and  treated  with  foreign 
substances,  the  utility  of  which,  from  the  point  of  view  of  the  consumer, 
is  more  than  questionable.”  {Report  to  Local  Government  Board,  New  Series, 
No.  49,  April,  1911). 

The  authors  are  prevented  by  exigencies  of  time  and  space  from  giving 
this  report  the  detailed  examination  it  merits  ; they  therefore  suggest  as 
with  that  of  Monier- Williams  its  careful  comparison  with  Snyder’s  bulletin, 
summarised  in  paragraph  518.  Hamill  and  Monier- Williams  have  appar- 
ently finally  disposed  of  the  statements  that  the  extract  of  bleached  flour  is 
violently  poisonous  to  animals  ; they  also  find  no  evidence  of  the  presence 
of  diazo-compounds.  In  considering  Hamill’s  remarks  on  the  physio- 
logical or  pathological  effect  of  continual  minute  doses  of  nitrite,  it  is  well 
to  bear  in  mind  the  actual  amounts  ingested  : on  page  384  of  this  book  it 
is  pointed  out  on  the  authority  of  Wesener  and  Teller  that  in  order  to  take 
the  maximum  safe  dose  of  nitrite  (3  grains)  by  eating  the  bread  from  bleached 
flour,  10,000  one  pound  loaves  would  have  to  be  eaten,  and  that  at  the 
average  rate  of  bread  consumption,  an  individual  who  commenced  the  day 
he  was  born  would  be  55  years  old  before  he  would  thus  have  taken  a single 
medicinal  dose  of  nitrogen  trioxide.  Flour  is  one  of  those  articles  of  food 
which  are  never  eaten  in  the  raw  state,  and  Snyder  states  categorically  that 
the  bleaching  gas  is  expelled  from  flour  in  all  the  various  ways  in  which  it  is 
prepared  for  food.  He  points  out  that  bread  made  from  bleached  flours  and 
baked  out  of  contact  with  combustion  of  gases  gives  no  reaction  for  nitrites, 
whereas  bread  made  from  unbleached  flour  and  baked  in  an  ordinary  gas 
oven  shows  appreciable  amounts  of  nitrites  formed  from  combustion  of  the 
gas.  He  then  asserts  that  “ since  the  material  used  in  the  bleaching  of 
flour  is  expelled  in  the  preparation  of  the  food,  there  remains  no  question 
for  physiological  consideration.”  Under  these  circumstances,  it  is  unfor- 
tunate that  the  reports  under  examination  deal  only  with  flour,  and  not 
with  the  resultant  bread. 

In  the  last  two  paragraphs  of  that  part  of  the  report  which  deal  with 


WHEAT,  ELOUR,  AND  BREAD  IMPROVERS. 


505 


flour  bleaching,  the  effect  on  the  consumer  is  dealt  with,  and  he  is  said  to 
obtain  no  compensating  benefit.  But  this  runs  counter  to  general  experi- 
ence ; as  Hamill  says  “ a large  number  of  people  desire  bread  of  exceptional 
whiteness.”  This  being  the  case,  any  process  which  tends  to  increase  the 
supply  of  white  flour  or  widen  the  sources  from  which  it  is  obtained  must 
necessarily  ultimately  result  in  lowering  the  price  to  the  consumer.  For 
example  the  mechanical  improvements  in  milling  have,  by  the  removal  of 
dirt,  materially  increased  the  whiteness  of  flour.  As  a consequence  the 
seconds  or  households  quality  of  bread,  sold  at  seconds  price,  is  now  better 
in  colour  than  was  the  best  bread  at  the  best  price  of  twenty  years  ago. 
The  miller  of  to-day  works  on  a finer  margin  of  profit  than  did  his  prede- 
cessor, and  the  consumer  has  reaped  the  full  advantage  of  the  various  im- 
provements in  modern  milling.  If  from  a dark  flour,  such  as  that  from  Walla 
Walla  or  Durum  wheat,  a dark  loaf  is  naturally  obtained,  and  there  is  an 
absolutely  harmless  process  by  which  it  can  be  made  into  a white  loaf,  then 
the  authors  incline  to  the  opinion  that  very  few  of  those  persons  who  prefer 
whiteness  would  object  to  its  treatment.  This  is  borne  out  by  analogies 
drawn  from  other  articles  of  food.  Loaf  sugar  is  naturally  of  a yellow  cast, 
and  this  is  corrected  in  manufacture  by  the  addition  of  ultramarine  or 
other  blue.  Yet  the  public  do  not  make  the  slightest  objection  to  the  white- 
ness of  sugar  being  obtained  by  chemical  treatment.  In  milk  the  public 
taste  runs  in  the  opposite  direction ; the  natural  white  colour  of  milk  is  dis- 
liked, and  a yellow  tint  preferred.  The  consumer  not  merely  tolerates  the 
addition  of  colouring  matter,  but  rejects  white  milk  and  insists  on  its  being 
yellow ; in  many  cases,  even  when  he  or  she  knows  quite  well  how  the  yellow- 
ness is  produced. 

So-called  “ Flour  Improvers^ — The  report  first  deals  with  the  proposed 
addition  of  mineral  phosphates  to  flour,  and  points  out  that  “ a large  portion 
of  the  phosphorus  in  flour  is  present  in  organic  combination  ” — this  is  an- 
other way  of  saying  that  a small  portion  is  present  in  the  inorganic  form. 
This  small  portion  of  mineral  phosphate  exercises  however  a most  profound 
influence  over  the  whole  quality  of  the  flour  for  bread-making  purposes. 
Proof  of  this  is  afforded  by  the  fact  that  to  flours  which  are  deficient  in  certain 
baking  qualities,  the  addition  of  what  is  the  merest  trace  of  certain  mineral 
salts  exercises  a most  remarkable  improving  effect.  These  additions  con- 
sist of  mineral  constituents  which  are  normally  present  in  wheat,  and  which 
usually  are  relatively  deficient  in  the  flour  improved  by  their  addition. 
The  fact  that  such  additions  result  in  marked  improvement  does  not  admit  of 
doubt. 

The  next  question  raised  is  that  of  increased  loaf  production  from  a given 
quantity  of  flour,  which  of  necessity  means  a diminution  in  the  actual  amount 
of  flour  in  each  loaf  and,  according  to  the  report,  a diminution  in  nutritive 
value,  a consequence  of  which  is  “ that  the  consumer  in  this  respect  loses 
by  the  treatment.”  This  is  an  important  issue,  and  requires  to  be  fairly 
faced  and  examined.  It  is,  however,  of  far  wider  importance  than  the 
mere  addition  of  “ improvers  ” to  flour.  Native  English  wheats  are  as  a 
whole  extremely  weak  in  character ; that  is  to  say,  their  flours  possess  a low 
protein  content,  low  water  absorbing  power,  and  produce  small  close  loaves. 
Because  of  these  properties  they  are  only  used  to  a small  extent  and  com- 
mand a comparatively  low  price.  The  Home  Grown  Wheat  Committee 
has  been  and  is  devoting  its  attention  to  the  improvement  of  English  wheats. 
Assuming  their  efforts  to  be  successful,  the  line  of  improvement  will  be  partly 
in  the  direction  of  an  increase  in  the  protein  or  gluten  content,  but  also 
largely  in  that  of  raising  the  quality  of  the  gluten  itself,  and  thereby  increas- 
ing the  strength  of  the  wheat.  In  so  far  as  the  committee  succeeds  it  will 
have  developed  and  augmented  one  of  our  most  valuable  national  assets  ; 


506 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


but  if  it  does  this,  the  result  will  be  that  a weak  wheat  will  liave  been 
made  to  simulate  a stronger  wheat  although  as  regards  protein  content  it  is 
inferior  to  that  which  it  imitates.  The  improvement  of  home  grown  wheat 
itself ; and  also  subsequently  that  of  flour  therefrom,  will  be  secured  by  the 
attainment  of  the  same  ends  (and  probably  largely  by  the  same  means,  viz., 
that  of  modifying  their  mineral  content),  and  both  must  stand  acquitted 
or  condemned  by  the  same  judgment.  The  logical  outcome  of  the  suggestion 
in  the  report  is  that  the  growth , improvement,  and  consequently  increased 
use  of  English  wheats,  should  so  far  as  possible  be  discouraged,  because  of 
their  inferiority  in  protein  content.  In  so  far  as  weakness  is  due  to 
quality  rather  than  quantity  of  gluten,  any  improvement  which  causes 
flour  from  the  same  wheat,  or  the  same  type  of  wheat,  to  yield  bolder 
loaves  and  of  better  texture,  whether  by  alteration  of  the  mineral  con- 
tent or  the  use  of  a more  vigorous  yeast,  will  at  the  same  time  increase 
the  water-absorbing  capacity  of  the  flour,  since  both  to  some  extent  go  hand 
in  hand.  But  it  does  not  quite  follow  that  the  consumer  thereby  loses. 
Everything  else  being  equal,  a bold  well-risen  loaf  is  more  digestible  than 
a small  and  clammy  one  from  the  same  flour.  It  may  therefore  well  be 
that  the  greater  digestibility  may  more  than  compensate  for  the  slightly  less 
flour  in  the  loaf  as  a result  of  the  increase  in  water-absorbing  power. 

In  these  matters  it  is  far  better  to  argue  from  actual  data  rather  than 
mere  generalities,  amd  accordingly  the  following  experiments  were  made  : — 
An  ‘‘  improver  ” was  selected  of  purely  mineral  and  inorganic  origin,  and 
this  was  added  to  the  flour  in  the  proportion  of  I oz.  to  the  sack.  This 
amounts  to  1 part  to  4480,  or  0-022  per  cent.  The  proportion  in  bread  is 
naturally  less,  being  an  addition  of  about  0-014  per  cent,  of  mineral  matter 
natural  to  wheat,  and  occurring  in  several  times  the  quantity  in  many  excel- 
lent drinking  waters.  Neither  in  the  mode  of  manufacture,  nor  in  the 
nature  of  its  residuum,  could  there  be  a suggestion  of  anything  but  absolute 
liarmlessness  in  the  particular  improver  employed.  Loaves  were  baked 
from  various  flours  with  and  without  the  improver  ; in  boldness  of  volume 
and  appearance  and  texture  of  crumb,  the  treated  loaves  were  judged  by 
millers  as  showing  an  improvement  equal  to  from  Is.  to  D.  6d.  in  the  com- 
mercial value  of  the  flour. 

The  first  test  was  made  with  an  all-English  flour,  the  following  quan- 
tities being  taken  : A,  560  grams  flour,  7 grams  salt,  10  grams  yeast,  and 
280  grams  water.  B consisted  of  the  flour  treated  at  the  rate  of  I oz.  per 
sack,  but  in  all  other  respects  the  same.  The  loaves  were  baked  in  tins  of 
the  same  size,  and  were  of  the  following  greatest  height  : A,  untreated,  13-3 
centimetres  ; B,  treated,  16-0  centimetres. 

The  volumes  would  be  in  the  same  relative  proportions  as  the  heights. 

On  analysis,  the  breads  gave  the  figures  quoted  below.  Both  were  sub- 
jected to  comparative  digestion  tests  in  which  50  grams  of  the  bread  were 
treated,  at  body  temperedure,  with  a slightly  acid  solution  of  Armour’s  stand- 
p.rd  pepsin  (artificial  gastric  juice),  and  afterwards  with  a slightly  alkaline 
solution  of  Armour’s  standard  pancreatin  (artificial  pancreatic  juice).  The 
resultant  mass  was  filtered,  and  proteins  determined  in  the  filtrate.  A correct- 
ion was  made  for  the  quantity  present  in  the  reagents  used.  The  following 
results  were  obtained  : — 


iMoisture 

A,  untreated.- 

. . 43-54  . . 

B,  treated. 
42-70 

Bread  solids 

. . 56-46  . . 

57-30 

Total  proteins  in  bread  . . 

ICO -00  .. 

6-76  . . 

100-00 

6-86 

Total  digested  proteins  of  each  bread 

5-72  . . 

6-04 

Percentage  of  total  protein  digested 

. . 84-61  . . 

88-04 

WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 


507 


As  the  water  used  in  each  case  was  the  same,  the  difference  in  bread 
solids  was  only  such  as  necessarily  follows  from  the  irregularities  of  baking. 
B had  in  fact  0-84  per  cent,  more  solids  than  A.  The  total  protein  in  each 
was  practically  the  same  ; but  under  the  conditions  of  the  digestion  test 
100  parts  of  A yielded  5-72  parts  of  digested  protein,  whereas  100  parts  of 
B similarly  yielded  6-04  parts.  Out  of  every  100  parts  of  protein  present  in 
A,  84-61  were  digested,  while  out  of  every  100  parts  of  protein  present  in  B, 
88-04  parts  were  digested  under  the  conditions  of  the  experiments.  The 
greater  digestibility  of  B was  very  noticeable  during  the  progress  of  the 
test  : inspection  showed  that  the  more  highly  vesiculated  and  spongy 
crumb  of  B broke  down  into  a homogeneous  pulp  much  more  rapidly  than 
did  that  of  A. 

In  the  next  place  experiments  were  made  with  different  quantities  of 
water  in  the  untreated  and  treated  loaves.  In  practice  it  is  very  doubtful 
whether  any  such  use  of  improvers,  as  is  being  described,  results  in  the 
successful  use  of  more  than  an  extra  two  quarts  of  water  per  sack.  That 
proportion  has  accordingly  been  added  to  the  treated  flours.  Tests  were 
thus  made  on  all-English  and  all-Manitoba  wheat  flours.  The  following 
are  the  quantities  used  : — 

A.  560  grams  English  flour  untreated,  7 grams  salt,  10  grams  yeast, 

280  grams  water  (equal  to  56  quarts  per  sack). 

B.  560  grams  same  flour  treated,  salt  and  yeast  as  before,  290  grams 

water  (equal  to  58  quarts  per  sack). 

C.  560  grams  Manitoba  flour  untreated,  salt  and  yeast  as  before,  280 

grams  water. 

D.  560  grams  same  flour  treated,  salt  and  yeast  as  before,  290  grams  water. 

Particulars  are  set  out  of  the  results  of  various  determinations  made, 

and  also  of  digestion  tests  like  those  ca^rried  out  on  the  previous  flour. 


English. 


Manitoba. 


Weight  of  dough  when  scaled, 
grams 

Weight  of  loaves  from  oven, 
grams 

Weight  of  loaves,  next  day, 
grams 

Greatest  height  of  loaves,  centi- 
metres 

Moisture  by  analysis  . . 

Bread  solids  by  analysis.  ..... 

Moisture  in  B and  D,  second 
day,  from  difference  in 
weight  of  loaves  . . 

Bread  solids  from  ditto 

Total  proteins  in  bread 

Total  digested  proteins  of  each 
bread 

Percentage  of  total  protein 
digested 


A. 

B. 

C. 

D. 

itreated. 

Treated. 

Untreated. 

Treated. 

840 

, . 850 

00 

. . 852 

787 

. . 790 

. . 788 

. . 792 

763 

. . 768 

. . 761 

. . 765 

12-9 

. . 15-0 

. . 16-8 

. . 18-2 

43-36 

. . 43-40 

. . 42-62 

. . 42-54 

56-64 

. . 56-60 

. . 57-38 

. . 57-46 

43-36 

. . 43-73 

. . 42-62 

. . 42-92 

56-64 

. . 56-27 

. . 57-38 

. . 57-08 

6-82 

6-77 

8-25 

8-20 

6-20 

6-14 

7-06 

7-50 

90-90 

. . 90-69 

. . 85-57 

. . 91-46 

As  the  result  of  analytic  determinations,  the  bread  solids  of  the  members 
of  each  pair  of  loaves  was  found  to  be  practically  the  same.  It  was  there- 
fore thought  to  be  the  fairest  comparison  to  take  the  analytic  data  for  the 
first  loaf  of  each  pair  and  then,  as  each  loaf  was  made  from  the  same  weight 
of  flour,  to  calculate  the  solids  of  the  second  loaves  from  the  difference  in 


508 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


weight  of  the  two  loaves  of  each  pair.  These  are  the  figures  given  as  being 
from  difference  in  weight  of  loaves.”  Evidently  they  must  take  cognis- 
ance of  the  whole  increased  weight  of  bread  obtained.  In  the  case  of  the 
English  flour  breads,  the  loss  in  weight  of  solids  due  to  increased  yield  is 
56*64  — 56*27  =0*37  per  cent.  With  the  Manitoban  flour  breads  the 
corresponding  loss  in  weight  is  57*38  — 57*08  = 0*30  per  cent.  The  loss 
in  weight  of  proteins  for  the  two  flours  is  respectively  : English,  6*82  — 
6*77  = 0*05  per  cent.,  and  Manitoban,  8*25  — 8*20  = 0*05  per  cent.  It  is 
submitted  that  these  differences  are  so  small  as  to  be  practically  inappreciable. 
On  being  subjected  to  digestion  tests,  the  protein  of  the  English  loaves  was 
digested  more  completely  than  in  the  preceding  test,  and  resulted  in  a slight 
advantage  in  favour  of  the  untreated  loaf,  the  difference  being  6*20  — 6*14 
= 0*06  per  cent.  With  the  harder  Manitoban  wheat  flour,  digestion  pro- 
ceeded with  considerably  more  rapidity  and  completeness  in  the  treated 
and  more  bulky  loaf,  the  figures  being  7*50  — 7*06  =0*44  per  cent,  in  fav- 
our of  the  treated  loaf.  Looking  at  the  whole  series  of  the  three  sets  of 
tests,  there  is  a decided  advantage  in  protein  digestibility  in  the  case  of  the 
treated  flours.  This  bears  out  the  previously  expressed  opinion  that  a 
bold,  well-risen  loaf  is  more  digestible  than  a small  and  clammy  one  from 
the  same  flour.”  Certainly,  these  results  cannot  be  said  to  afford  any  support 
to  the  view  that  there  is  a diminution  in  nutritive  value,  and  “ that  the  con- 
sumer in  this  respect  loses  by  the  treatment.” 

A further  question  is  whether,  even  if  obtainable,  any  advantage 
from  an  increase  of  yield  can  long  be  withheld  from  the  consumer.  No 
doubt  for  a time  any  miller  or  baker  who  discovers  a method  of  obtaining 
such  increase  will  benefit  thereby  ; but  almost  immediately,  he  utilises  his 
diminished  cost  of  production  by  offering  his  goods  at  a lower  rate  than  his 
competitors  in  order  to  increase  his  trade.  In  a surprisingly  short  time  the 
advantage  is  transferred  to  the  community  in  the  shape  of  a lower  price, 
or  increased  value  in  other  directions.  There  are  certain  towns  in  which 
the  general  taste  is  in  favour  of  varieties  of  bread  which  contain  an  unusually 
high  percentage  of  water,  but  this  compensates  itself  by  a lower  price  for 
the  bread.  If  the  price  is  worked  out  on  the  basis  of  charge  per  pound  of 
dried  solids  it  will  be  found  that  the  consumers  of  a bread  with  high  water 
content  pay  on  the  average  no  more  than  do  those  who  prefer  a drier  type 
of  bread  from  flour  of  the  same  price.  An  example  of  this  is  that  of  tlie 
bread  of  London  and  Manchester  respectively  ; the  former  is  a crusty  bread 
of  low  water  content,  while  the  latter  is  a tin  loaf  with  a higher  percentage 
of  moisture.  At  the  moment  of  wTiting  the  Board  of  Trade  Returns  give 
as  the  price  of  bread  : London,  5Jc?.,  Manchester,  ^d.  per  quartern  loaf. 
The  same  laws  would  naturally  operate  with  any  extended  improvement  in 
the  weaker  wheats, 

It  is  common  ground  that  some  additions  effect  very  marked  improve- 
ments in  certain  ways,  and  also  that  other  weird  preparations  and  addi- 
tions are  most  dangerous.  But  it  scarcely  follows  that  because  some  are 
bad  all  should  be  condemned.  The  whole  subject  points  to  the  advisability 
of  the  establishment  of  a Court  of  Reference  which  should  exercise  a general 
supervision  over  the  practice  of  additions  to  articles  of  food.  The  Court 
should  prescribe  such  regulations  as  it  deemed  necessary,  and  these  would 
be  a guide  both  to  manufacturers  and  vendors  of  articles  of  food,  and  also 
to  those  who  are  responsible  for  the  administration  of  the  Food  and  Drugs 
Acts.  The  Court  should  hear  applications  for  permission  to  employ  any 
process  which  involved  the  addition  of  foreign  substances  to  articles  of 
food,  together  with  arguments  and  evidence  in  favour  of  and  against  such 
permission  being  granted.  The  Court  would  then  unconditionally  refuse 
or  accede  to  such  application,  or  might  grant  the  desired  permission  subject 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS.  509 

to  conditions.  In  the  last  case  one  of  the  conditions  might  be  that  the 
nature  and  objects  of  the  addition  should  be  declared  by  the  vendor.  A 
declaration  made  under  these  circumstances  would  imply  that  the  proposed 
treatment  was  not  in  any  way  injurious  to  health.  Either  on  its  own  initia- 
tive, or  on  the  representations  of  parties  interested,  the  Court  should  be 
empowered,  on  proper  terms,  to  review  its  own  decisions,  and  either  increase 
in  stringency,  or  relax,  its  regulations  as  necessity  arose. 

631.  Bread  Improvers. — The  possibilities  of  treatment  by  the  baker 
a^re  much  greater  than  those  of  the  miller  inasmuch  as  he  can  make  use  of 
liquids  of  any  description  as  well  as  solids.  In  the  manufacture  of  bread,  the 
addition  of  certain  other  substances  than  flour  and  water  is  a recognised 
and  integral  part  of  the  manufacture.  When  brewer’s  yeast  was  the  only 
type  used,  some  yeast  stimulant  was  absolutely  necessary  for  reasons  already 
explained  (paragraphs  376-9).  Potatoes  were  found  exceedingly  useful  and 
convenient  for  the  purpose,  and  accordingly  the  potato  ferment  was  at  one 
time  a regular  part  of  the  process  of  bread-making.  With  the  use  of  dis- 
tiller’s yeast,  the  necessity  of  some  stimulant  for  the  yeast  no  longer  existed, 
and  accordingly  potatoes  have  largely  gone  out  of  use.  But  there  are  other 
functions  in  bread-making  fulfilled  by  the  potato,  and  these  continue  to 
require  attention.  Substances  added  for  the  purpose  of  effecting  improve- 
ments in  bread  may  be  grouped  into  the  following  classes  : — 

Milk. — Whole  or  separated  ; improves  flavour,  appearance  and  nutritive 
value. 

Butter. — This  and  other  fats  improve  flavour  and  shorten  crust,  thus 
preventing  toughness. 

Moistness-retaininj  bodies. — In  their  pure  state,  some  flours,  and  par- 
ticularly those  which  are  the  most  nourishing  as  a result  of  their  high  per- 
centage of  proteins,  produce  a bread  which  readily  becomes  somewhat  dry 
and  harsh.  To  remedy  this,  an  increase  in  the  quantity  of  gelatinised  starch 
and  dextrin  removes  harshness  and  makes  the  bread  remain  moist  and 
taste  moist  much  longer. 

Potatoes. — The  ordinary  boiled  potato  has  the  effect  just  mentioned.  As  a 
substitute,  it  has  been  proposed  to  dry  potatoes  and  grind  them  into  a meal 
or  flour.  Such  a preparation,  however,  only  adds  starch  in  the  ungelatinised 
form,  and  cannot  increase  the  moistness  as  a consequence.  Whatever  soluble 
constituents  the  potato  contains  are  thus  introduced  into  the  bread.  Re- 
cently, preparations  have  been  placed  on  the  market  which  consist  of  thor- 
oughly cooked  potatoes,  dried  and  reduced  to  a fine  powder.  These  are 
capable  of  acting  as  a direct  substitute  for  the  boiled  potato,  introducing 
the  same  substances  and  avoiding  the  mess  and  dirt  which  almost  of  necessity 
accompany  the  cooking  of  potatoes  in  a bakehouse. 

Gelatinised  Starches. — Among  members  of  this  group,  the  use  of  scalded 
flour  is  25re-eminent.  This  adds  gelatinised  starch,  which  may  be  used  in  a 
ferment,  or  if  wished  may  be  added  to  the  dough.  Scalded  rice  and  maize 
also  produce  the  same  effects.  The  employment  of  all  or  any  of  these  has 
the  advantage  of  greater  cleanliness  in  manipulation  than  occurs  with 
potatoes.  All  are  sources  of  gelatinised  starch.  Certain  grains  and  other 
starchy  bodies  are  now  gelatinised,  dried  off  and  sold  in  the  form  of  thin 
flakes.  These  may  be  used  as  ready -gelatinised  forms  of  starch  which 
require  no  cooking. 

Dextrinous  bodies. — From  its  well-known  gummy  properties,  dextrin 
serves  to  keep  bread  moist.  Its  principal  sources  in  bread  are,  starch 
which  has  been  converted  into  dextrin  by  enzymes,  malt  extract,  and  so- 
called  confectioners’  glucose,  which  is  really  almost  entirely  composed  of 
dextrin  and  maltose  (see  chapter  XXXIII.). 

Sweetening  bodies. — Sweetness  may  be  conferred  by  the  addition  of 


510 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


pure  sugar  or  by  the  use  of  malt  extract  or  “ glucose/’  both  of  which  contain 
maltose  in  large  quantities.  When  gelatinised  starch  is  acted  on  by  dias- 
tase, more  or  less  maltose  is  formed.  Maltose  may  be  thus  produced  from 
the  starch  of  the  flour  itself,  or  from  that  added  in  the  gelatinised  condition 
from  any  other  source.  In  addition  to  its  flavouring  properties,  sugar 
serves  the  yeast  as  a source  of  carbon  dioxide  gas. 

Diastatic  bodies. — Various  enzymes  serve  the  purpose  of  converting 
starch  into  dextrin  and  maltose.  Flour  itself  contains  a considerable 
quantity  of  diastase.  Carefully  prepared  malt  extract  is  also  actively 
diastatic,  while  certain  special  forms  contain  diastase  in  a very  concen- 
trated degree.  Malt  flour,  particularly  that  of  air-dried  malt,  is  also  rich 
in  diastatic  power.  All  these  substances  are  used  for  bread-making  purposes 
In  addition  to  the  starch  converting  diastase,  these  bodies  may  contain 
more  or  less  of  proteolytic  enzymes  by  which  the  gluten  of  flour  is  affected. 
The  charges  thus  produced  may  be  beneficial  or  otherwise  according  to  the 
nature  and  quality  of  the  gluten. 

Mineral  bodies. — First  among  these  is  common  salt,  which  in  addition 
to  its  flavouring  properties  acts  as  a binding  or  strengthening  agent  on  the 
dough.  Certain  other  mineral  bodies  have  beneficial  effects  on  bread. 
One  of  these  is  calcium  chloride,  which  in  small  quantities  serves  as  a 
strengthening  agent,  and  also  may  be  useful  as  a source  of  lime  for  nutritive 
jmrposes.  In  its  general  properties  calcium  chloride  falls  into  somewhat  the 
same  category  as  salt.  Magnesium  sulphate  is  at  times  employed,  more 
especially  it  is  said  in  some  of  the  Midland  counties.  For  reasons  already 
given,  the  addition  of  phosphates  and  phosphoric  acid  serves  to  effect  some 
improvements  in  bread. 

Yeast  nourishing  bodies. — Several  of  the  substances  already  mentioned 
are  of  service  as  direct  or  indirect  yeast  foods  ; among  these  are  sugars  and 
the  bodies  from  which  derived,  the  diastases  which  produce  sugar,  and  some 
mineral  salts.  In  addition  to  these  some  bodies  rich  in  organic  nitrogenous 
constituents  are  of  value  as  food  and  stimulants  for  yeast. 

632.  Malt  Extract. — This  being  one  of  the  substances  most  largely  used 
for  the  improvement  of  bread,  its  preparation  and  properties  require  a 
somewhat  extended  description.  Malt  extract  is  prepared  by  evaporating 
at  a low  temperature  in  vacuo  the  filtered  wort  from  mashed  malt  until  the 
resultant  liquid  is  of  the  consistency  of  a thick  syrup.  In  order  to  investigate 
the  composition  of  malt  extract  under  different  conditions,  the  folloving 
experiments  were  made  : — 

A high  quality  sample  of  pale  malt  w'as  finely  ground  ; and  of  this  500 
grams  w ere  taken,  mixed  whth  2,000  c.c.  of  w^ater,  and  mashed  for  2 hours, 
at  a temperature  of  60°  C.,  in  a w'ater- jacketed  pan.  The  resultant  wort 
was  then  filtered  bright,  and  the  “ grains  ” w^ashed,  dried  and  w'eighed, 
their  w^eight  being  113  grams,  showing  that  over  75  per  cent,  of  the  ma’t 
had  gone  into  solution.  This  w'ort  w^as  called  Preparation  I.,  Unevaporated. 
A portion  was  reserved  for  analysis,  and  the  remainder  evaporated  in  vacuo, 
the  operation  being  pushed  as  far  as  possible  : this  constituted  Preparation 
I.,  Evaporated. 

Another  500  grams  of  the  malt  w'ere  then  taken,  mixed  with  2,000  c.c. 
cold  water,  continually  stirred  during  3 hours,  and  then  allow  ed  to  stand 
overnight.  The  clear  liquid  was  poured  off  in  the  morning,  the  residual 
malt  drained  moderately  dry.  The  liquid  was  filtered  bright,  and  consti- 
tuted Preparation  II.,  Unevaporated.  A part  of  this  was  evaporated  in 
precisely  the  same  manner  as  with  No.  I.,  and  is  termed  Preparation  II., 
Evaporated. 

The  residual  malt  from  No.  II.  was  next  taken,  mashed  with  2000  c.c. 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS.  511 

more  water  for  6 hours,  at  60°  C.,  and  then  raised  to  100°  C.,  and  filtered 
bright.  This  constituted  Preparation  III.,  Unevaporated.  A portion  vv'as 
evaporated  in  vacuo  as  before,  and  this  formed  Preparation  III.,  Evapor- 
ated. 

Each  of  these  was  then  subjected  to  analysis,  determinations  being 
made  as  given  in  the  table  on  page  512,  in  which  are  also  included  similar 
analyses  of  commercial  samples  of  guaranteed  pure  malt  extract. 

^^arious  determinations,  as  given  below,  were  made  on  the  Unevaporated 
Preparations. 

Xo.  I.  No.  II.  No.  III. 

Specific  gravity  at  150°  C 1,057-5  1,020-7  1,050-0 

Dry  Solids,  grams  per  ICO  c.c.  calculated  from 

gravity  . . . . . . . . . . 14-93  5-37  13-CO 

Dry  Solids,  grams  per  ICO  c.c.  by  evaporation 

and  weighing  . . . . . . . . 14-06  4-93  12-78 

Dry  Solids,  weight  in  percentages  . . . . 13-30  4-83  12-17 

The  method  of  analysis  employed  is  that  described  in  Chapter  XXIX., 
and  is  subject  to  the  limitations  of  accuracy  there  explained.  It  should 
be  mentioned  that  all  the  figures,  both  on  the  liquids  and  the  extracts,  are 
the  results  of  direct  determinations  ; the  percentage  composition  of  “ Dried 
Solids  being  calculated  from  those  obtained  in  the  liquid  or  extract  with 
water  present.  The  dextrin  was  precipitated  by  alcohol  and  corrected  for 
solubility  and  amount  of  precipitated  protein  : it  no  doubt  contains  not 
only  pure  dextrin,  but  also  the  other  gum-like  substances  frequently  returned 
as  “ indeterminate  bodies.” 

The  No.  I.,  or  whole  extract,  contained  sucrose  in  the  wort,  but  this 
disappeared  during  concentration.  The  g'ucoses  also  show  a diminution, 
while  dextrin  increases.  The  dextrin  precipitate  in  the  evaporated  extract 
was  much  darker,  and  evidently  contained  a considerable  proportion  of 
products  of  caramelisation. 

The  cold  water  extracts.  No.  II.,  are  very  interesting.  The  proteins 
and  phosphates  are  very  high  : so  also  is  the  sucrose,  which,  however, 
diminishes  on  concentration.  The  quantity  of  maltose  is  very  small,  while 
the  glucoses  represent  about  half  the  total  weight  of  the  solids  present. 
The  sugars  here  again  diminish  during  concentration,  while  dextrin  increases, 
no  doubt  for  the  same  reason  as  in  No.  I. 

In  No.  III.,  as  might  be  expected,  sucrose  is  absent,  any  traces  in  the 
original  solution  being  doubtless  destroyed  during  the  prolonged  mashing. 
Glucose  (dextrose),  and  laevulose  are  present  in  very  small  quantity,  the  sugar 
being  almost  entirely  maltose.  As  might  be  expected,  the  dextrin  is  high,  and 
the  act  of  concentration  has  produced  practically  no  alteration  in  the  pro- 
portions of  the  constituents  present,  the  lengthened  period  of  mashing  and 
subsequent  boiling  having  reduced  all  bodies  present  to  a stable  condition. 

The  above  three  types  of  extract  are  sometimes  called — 

No.  I Whole  extract,  being  the  entire  extract  of  the  malt. 

No.  II.  Cold  water  extract,  from  the  fact  of  its  containing  the  cold  water 
soluble  constituents  only. 

No.  III.  Spent  extract,  being  prepared  from  the  comparatively  spent 
grains  after  extraction  with  cold  water.  This  is  also  sometimes  called  a 
“ split  ” extract,  since  the  products  of  the  malt  are  split  into  two  separate 
lots  in  its  production. 

All  three  of  these  are  more  or  less  represented  in  commercial  extracts, 
the  first  being  the  older  and  purely  normal  type  of  the  whole  malt.  With  the 
demand  for  extracts  of  high  diastatic  power,  No.  II.  type  came  into  the 
market.  The  manufacture  of  No.  II.  made  the  preparation  of  No.  III.  a 


512 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

Analyses  of  Malt  Extract  Preparations. 


Constituents. 


Water  . . 

Mineral  Matter  (Phosphates) 

Proteins 

Dextrin . . 

Sucrose  . . 

Maltose  . . 

Glucose  and  Lsevulose 


Cuprous  Oxide,  CU2O,  from  100  grams 
Reducing  Sugars,  calculated  entirely 
Maltose 


Water  . . 

Mineral  Matter  (Phosphates) 

Proteins 

Dextrin . . 

Sucrose  . . 

Maltose  . . 

Glucose  and  Lsevulose 


Cuprous  Oxide,  CU2O,  from  100  grams 
Reducing  Sugars,  calculated  entirely 
Glucose  and  Lsevulose 


M'ater  . . 

Mineral  Matter  (Phosphates) 

Proteins 

Dextrin 

Sucrose  . . 

Maltose 

Glucose  and  Lsevulose 


Cuprous  Oxide,  CU2O,  from  100  grams 
Reducing  Sugars,  calculated  as  Maltose 


Water  . . 

Mineral  Matter  (Phosphates) 

Proteins 

Dextrin . . 

Sucrose  . . 

Maltose  . . 

Glucose  and  Lsevulose 


(’uprous  Oxide,  CU2O,  from  100  grams 
Reducing  Sugars,  calculated  as  Maltose 


No.  I.,  Unevaporated.' 

No.  II.,  Evaporated. 

Whole  i 
j Liquid.  | 

Dried 

Solids. 

Whole 

Extract. 

Dried 
Solids.  1 

86-70 

14-70 

0-24 

1-77 

1-70 

1-99  ' 

0-86 

6-44 

5-27 

6-18 

1-32 

9-95 

10-82 

12-68 

0-43 

3-23 

Absent 

Absent 

, 9-04 

68-03 

60-97 

71-48  ' 

1-41 

10-58 

6-54 

7-67 

1 100-00  1 

100-00 

100-00  I 

100-00 

13-99 

105-2 

87-50 

103-70  . 

11-30 

84-93 

70-67 

82-85 

1 

No.  II. 5 Unevaforated 

No.  II.,  Evaporated. 

95-17  , 



22-90 



0-32 

6-52 

4-80 

6-23 

0-80 

16-56 

12-71 

16-49 

0-60 

12-36 

13-66 

17-72 

0-45 

9-31 

4-79 

6-21 

0-21 

4-20 

1 2-69 

3-48 

2-45 

51-05 

* 38-45 

L 

49-87 

100-00 

100-00 

100-00 

i 100-00 

5-11 

106-43 

79-49 

103-10 

2-57 

53-66 

40-08 

51-99 

No.  III. Unevaporated 

No.  III.,  Evaporated. 

87-83 

— 

11-20 



0-17 

1-40 

Ml 

1-24 

0-44 

3-61 

3-37 

3-79 

2-44 

20-03 

17-40 

19-60 

Absent 

Al  sent 

Absent 

Absent 

8-82 

72-45 

66-06 

74-40 

0-30 

2-51 

0-86 

0-97 

100-00 

100-00 

100-00 

100-00 

11-52 

94-67 

83-5 

94-03 

9-31 

1 76-48 

67-44 

75-94 

First  Commercial 
Extract. 

Second  Commercial 
Extract. 

Whole 

Extract. 

Dried 

Solids. 

Whole 

Extract. 

; Dried 
Solids. 

22-23 



27-64 

1 

1-10 

1-42 

1-40 

1-93 

3-01 

3-88 

4-74 

i 6-55 

12-90 

16-59 

5-80 

8-02 

3-59 

4-61 

1-92 

2-66 

54-84 

70-51 

53-65 

74-14 

2-33 

2-99 

4-85 

6-70 

100-00 

100-00 

100-00 

100-00 

72-5 

93-22 

80-0 

110-5 

58-55 

75-28 

64-61 

89-29 

WHEAT,  FLOUR,  AND  BREAD  IMPROVERS.  513 

necessity  in  order  to  utilise  the  very  large  proportion  of  residual  matter 
from  making  the  cold  water  extract. 

In  diastatic  power.  No.  I.,  if  properly  prepared  and  carefully  concen- 
trated, should  be  of  fair  quality.  No.  II.  will  be  of  very  high  diastatic 
value,  while  No.  III.  will  be  devoid  of  any  diastatic  power  whatever. 

Modern  manufacturing  processes  are  a combination  of  the  various 
methods  described,  mashing  being  made  at  various  temperatures,  or  at  a 
lower  than  normal  temperature  in  order  to  retain  diastase ; while  a good 
deal  of  the  purely  saccharine  extract  is  sacrificed,  or  obtained  in  a further 
extraction,  when  it  may  or  may  not  be  mixed  in  with  the  first  or  more  dias- 
tatic extract. 

The  samples  of  commercial  extract  call  for  but  little  remark  ; in  the 
first,  the  dextrin  is  fairly  high,  and  so  also  is  the  maltose ; sucrose,  dextrose, 
and  laevulose  being  present  in  small  quantity.  At  the  same  time,  the  sample 
is  well  concentrated,  but  22-23  per  cent,  of  water  being  present.  With  any 
less  moisture  the  extract  would  be  too  stiff  to  pour  out  of  tins  or  drums 
when  cold.  The  second  commercial  sample  affords  evidence  of  having  been 
worked  at  a higher  temperature,  although  the  degree  of  concentration  is 
less.  Both  these  extracts  show  all  signs  of  being  nothing  beyond  pure, 
normal  extracts  of  malt. 

In  breadmaking,  the  addition  of  malt  extract,  in  the  first  place,  increases, 
to  the  extent  to  which  it  is  used,  the  quantities  present  of  the  various  in- 
gredients of  the  extract,  among  which  are  sugars  which  impart  sweetness  ; 
dextrin,  by  which  the  bread  is  caused  to  remain  moister  ; and  phosphates, 
which  add  to  the  bone-forming  materials,  and  also  act  as  a yeast  stimulant. 
There  is  in  addition  the  specific  effect  on  the  constituents  of  the  flour  caused 
by  the  diastase  present  in  the  extract. 

633.  Malt  Extract,  Commercial  Manufacture,  British. — The  following 
is  a description  of  the  method  of  malt  extract  manufacture  as  carried  out 
by  the  British  DiaMalt  Company  at  their  works  at  Sawbridgeworth,  by 
whom  the  authors  were  afforded  full  opportunities  of  experimental  investi- 
gation of  their  various  processes  on  the  spot.  The  factory  is  conveniently 
situated  near  the  principal  barley  growing  districts  of  England,  and  comprises 
in  the  first  place  large  makings,  both  on  the  floor,  and  the  pneumatic  systems. 
Explanations  of  both  these  have  been  already  given  in  paragraph  39L 
The  Company  also  imports  large  quantities  of  Hungarian  barley  and  malt. 
The  malt  is  first  screened,  and  then  ground  in  a Seck-mill,  after  which  it 
finds  its  way  into  the  mash-tun,  where  only  malt  and  water  are  used.  (The 
manufacturers  make  a great  point  of  their  claim  that  their  extract  is  the 
product  of  pure  malt  only,  and  that  no  malt  substitute  finds  its  way  into 
their  factory.)  An  examination  of  the  preparation  made  for  bakers  and 
sold  to  them  under  the  name  of  Diamalt  shows  it  to  be  prepared  from  a pale 
diastatic  malt,  which  has  evidently  been  mashed  at  a comparatively  low 
temperature  in  order  to  conserve  the  diastase  as  much  as  possible.  In 
consequence  the  colour  of  the  extract  is  lighter,  and  the  yield  less  for  a given 
weight  of  malt  than  when  higher  temperatures  are  employed  and  the  mash- 
ing pushed  further.  The  diastase  and  protein  contents  exist  therefore  in  a 
more  concentrated  form  in  Diamalt  than  in  higher  temperature  extracts. 
The  British  Company  is  an  offshoot  of  the  parent  European  Company,  and 
manufactures  the  extract  from  a general  formula  employed  by  that  com- 
pany. They  are  therefore  under  an  embargo  of  secrecy,  and  a demonstra- 
tion of  their  whole  process  was  only  given  in  strictest  confidence.  The 
authors  can  only  say  that  the  mashing  and  concentration  in  vacuo  are  con- 
ducted in  plant  of  the  most  modern  and  perfect  description,  and  under 
conditions  of  the  most  absolute  cleanliness.  The  principle  of  the  whole- 

L L 


'514 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


■operation  is  very  simple,  but  at  all  stages  the  greatest  possible  care  and 
attention  are  required  in  order  to  maintain  the  correct  temperatures  on 
Avhich  the  success  or  non-success  of  the  manufacture  depends.  The  follow- 
ing are  the  results  of  an  analysis  of  the  extract  thus  obtained : — 


Gravity  of  10  per  cent,  solution 

. . 1,029 

Opticity  of  10  per  cent,  solution  in  2 decimetre  tube 

. . 15-40° 

Water 

. . 26-56 

Mineral  Matter  (Phosphates)  . . 

1-06 

Proteins  . . 

5-88 

Dextrin  . . 

4-65 

Sucrose  . . 

. . 2-87 

Maltose  . . 

. . 39-53 

Glucose  and  Lsevulose 

. . 19-45 

100-00 

Cuprous  Oxide,  CuaO,  from  100  grams  . . 

87-5  grams, 

Reducing  Sugars  calculated  entirely  as  Maltose 

70*67 

Diastase  expressed  in  degrees  Lintner 

90*0 

In  bread-making  tests  with  this  extract,  the  rate  of  fermentation  was 
accelerated,  and  the  percentage  of  soluble  matter  in  the  bread  increased. 
In  consequence  there  was  a decided  gain  in  the  moistness  and  flavour  of 
the  bread.  In  consequence  of  the  presence  of  proteolytic  enzymes,  the  gluten 
of  the  flour  was  softened  during  fermentation  ; a result  which  is  of  special 
value  wLen  a preponderance  of  very  hard  flour  is  used. 

634.  Malt  Extract,  Commercial  Manufacture,  American. — With  their 
•comparatively  hard  flours,  American  bakers  And  in  malt  extract  an  adjunct 
used  probably  even  more  extensively  than  in  Great  Britain.  Important 
information  both  as  to  the  manufacture  and  employment  of  malt  extract 
in  America  has  been  furnished  to  the  authors  by  the  Malt-Diastase  Com- 
pany of  New  York,  one  of  whom  recently  visited  their  factory  in  Brooklyn. 
The  principles  of  the  methods  of  manufacture,  Le.,  mashing  and  subsequent 
evaporation  in  vacuo,  are  obviously  as  already  described.  The  following 
-p.re  analyses  of  three  brands  of  extracts  supplied  by  this  Company.  All 
al’e  made  from  pure  malt  prepared  from  barleys  grown  in  Minnesota  and 
North-Avestern  Iowa,  selected  because  of  their  high  protein  content.  The 
different  characters  of  the  various  extracts  is  determined  almost  entirely  by 
.the  selection  of  malts  and  appropriate  modifications  of  the  mashing  process. 

In  estimating  diastatic  activity  for  bakers’  purposes,  the  Company 
•employs  what  is  known  as  the  unit  method,  i.e.,  one  part  of  extract  is  alloAved 
to  act  for  30  minutes  upon  an  excess  of  3 per  cent,  starch  solution,  at  a 
temperature  of  99°  F.,  and  the  resulting  sugar  (maltose)  determined.  If  the 
maltose  produced  is  equal  in  Aveight  to  the  extract  used,  the  extract  is  said 
to  have  a diastatic  poAver  of  one  unit.  In  other  Avords,  the  weight  of  sugar 
produced,  divided  by  that  of  extract  used  in  the  test,  gives  the  number  of 
units  of  diastatic  capacity.  It  Avill  be  noticed  that  this  is  a starch  paste 
determination  as  against  the  soluble  starch  method  of  Lintner.  The  under- 
mentioned data  AA'ere  furnished  by  the  manufacturers  : — 


No.  1.  Name  of  brand. — Diax. 

,,  2.  ,,  ,,  ,,  O.P.  Malt  Extract. 

„ 3.  ,,  „ ,,  Standard  Malt  Extract. 

1 2.  3. 

Specific  Gravity . . ..  ..  ..  1-375  1-375  1-373 

Diastase  expressed  in  units  . . . . 9-35  4*01  3-63 

,,  „ ,,  degrees  Lintner  . . 146-31  59  02  51-21 

Acid  calculated  as  Lactic  ..  ..  1-248  1*07  1’08 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 


515 


The  authors  obtained  the  following  results  on  analysis 

Gravity  of  10  per  cent,  solution  ..  1,030-2  1,030*0  1,029-2 

Opticity  of  10  per  cent,  solution  in 


2 decimetre  tube  . . 

12-266° 

13-000° 

13-616 

Water,  including  about  2 per  cent,  of 
alcohol 

30-42 

29-73 

29-86 

Mineral  Matter  (Phosphates) 

1-54 

1-58 

1-42 

Proteins 

8-03 

6-93 

6-19 

Dextrin 

6-30 

4-55 

4-70 

Sucrose 

0-48 

0-48 

1-44 

Maltose 

28-26 

32-88 

38-69 

Glucose  and  Lsevulose 

24  97 

23-85 

17-70 

Cuprous  Oxide,  CU2O,  from  100  grams 

100*00 

84-5 

100*00 

88-0 

100*00 

830 

Reducing  Sugars  calculated  entirely  as 
Maltose 

68-25 

7107 

67-04 

Diastase  expressed  in  degrees  Lintner 

139-0 

79-2 

72-8 

The  No.  1 or  Diax  is  a malt  extract  of  exceptionally  high  diastatic  capa- 
city, and  is  probably  prepared  for  the  use  of  those  who  prefer  an  extract 
of  great  converting  power.  Nos.  2 and  3 are  more  alike  in  character,  and 
both  possess  a high  diastatic  value  for  bakers’  extracts.  They  also  contain 
an  active  amount  of  proteolytic  enzyme  (protease  or  peptase)  and  conse- 
quently produce  considerable  gluten-softening  effects.  With  hard  flours 
a limited  softening  is  very  desirable,  but  with  the  weaker  varieties  this 
must  not  be  allowed  to  become  excessive,  as  the  doughs  are  then  rendered 
too  soft  and  sticky.  A description  has  been  already  given  in  Chapter  XVIII. 
of  the  use  of  malt  extract  in  American  bread-making  methods.  A process, 
which  is  largely  used  in  that  country,  consists  in  the  employment  of  a gelatin- 
ised starch,  such  as  corn  flakes,  allowing  the  extract  to  convert  the  starches 
into  sugar  and  using  the  resulting  mixture  as  a medium  in  which  to  grow 
a short  ferment  of  one  hour,  as  one  hour  simply  gives  the  yeast  an  oppor- 
tunity to  consume  the  sugar  and  is  not  sufficiently  long  to  permit  it  to 
reproduce  itself.  Ten  and  twelve  minute  ferments  are  also  recommended  so  as 
to  give  the  yeast  an  opportunity  to  become  enlivened  and  the  individual 
cells  to  become  covered  with  pabulum. 

The  Malt-Diastase  Company  has  devoted  considerable  attention  to  the 
use  of  malt  extract  in  barms.  The  object  here  is  to  make  a smooth  batter 
and  by  adding  the  proper  quantity  of  water  at  212°  F.  to  strike  a mean 
temperature  of  170°,  being  sufficient  to  gelatinise  the  starch  and  yet  not 
hot  enough  to  coagulate  the  albumins.  This  permits  the  hydrolysis  of  the 
starch  into  maltose,  etc.,  and  at  the  same  time  leaves  the  glutenous  portion 
in  a position  to  be  acted  upon  by  the  protease  of  the  malt.  By  allowing 
the  mixture  to  stand  for  12  hours  or  so,  the  peptonising  action  seems  to 
be  quite  considerable  ; and  as  it  keeps  well,  the  barm  gives  the  baker  very 
little  trouble.  Experimentally,  the  Company  state  that  they  have  used 
this  barm  after  standing  5 days,  and  the  results  seem  to  be  even  better  as 
regards  flavour  than  when  used  fresh. 

The  following  is  their  recipe  for  the  preparation  of  such  malt  extract 
barm  : — 

Malt  Extract  Barm. 

Total  ingredients  used. — Malt  extract,  3 lbs.  ; flour,  3 lbs.  ; water,  2 
gallons. 

Procedure. — Take  flour,  3 lbs.  ; malt  extract,  J pint  ; water  at  130°  F., 


516 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


1 gallon.  Place  these  into  a suitable  container  and  make  into  a smooth 
batter.  Boiling  water  (212°  F.),  1 gallon.  Pour  this  into  the  batter  just 
made,  stirring  constantly  the  while  ; the  more  rapidly  the  boiling  water 
is  added  the  better.  Allow  this  mixture  to  cool  until  the  temperature 
reaches  one  hundred  and  forty  (140°)  F.,  then  add  the  remainder  of  the 
malt  extract.  The  digestion  of  the  starches  will  be  complete  in  30  minutes, 
and  the  barm  is  ready  for  use  just  as  soon  as  the  temperature  reaches  86°  F. 
If  in  a hurry  it  can  be  cooled  by  pouring  it  over  cracked  ice  through  a colander 
Quick  result,  however,  defeats  one  of  the  better  features  of  the  barm,  namely 
the  generation  of  the  peptones  from  gluten  by  the  protease  of  the  malt 
extract.  It  is  recommended  therefore  that  the  barm  be  made  one  day  and 
used  the  next.  The  formula  as  given  is  recommended  for  flavour,  also  for 
the  production  of  sugar.  The  amount  of  flour  in  the  formula  can  be  in- 
creased if  desired,  or  the  baker  may  add  Sako  or  flakes  to  increase  the  pro- 
portion of  sugar.  Each  pound  of  flour  will  yield  | lb.  of  malt  sugar  when 
treated  in  this  manner.  If  the  baker  desires  to  use  hops  he  can  substitute 
a boiling  infusion  of  them  for  boiling  water. 

This  is  not  precisely  a barm  in  the  sense  in  which  that  term  is  used  in 
Great  Britain,  but  rather  a mash  from  which  by  fermentation  either  a barm 
(i.e.,  a yeast)  or  a ferment  may  be  prepared. 

635.  Further  Analyses  of  Malt  Extract. — By  kind  permission  of  Messrs. 
Peek  Frean  & Co.,  Ltd.,  biscuit  manufacturers,  the  following  particulars 
of  malt  extracts  are  herein  given.  This  firm  procured  from  various  sources 

Physical  Characters  of  Malt  Extracts. 


Reference 

Letter. 

Colour. 

Consistency. 

Odour. 

Flavour. 

A 

Light 

1 

Medium 

Pleasant 

Clean,  sweet. 

B 

Medium  . . 

Medium 

Less  pleasant 

Bitter,  sweet,  cling- 
ing. 

C 

Light 

Medium 

Pleasant 

Clean,  sweet. 

D 

Light 

Medium 

Pleasant 

Disagreeable. 

E 

Medium  . . 

Stiff  and  crys- 
talline 

Peculiar 

Recalls  low  grade 
honey. 

F 

Medium  . . 

Medium 

Slightly  burnt 

Slightly  burnt  but 
clean. 

G 

Light 

Rather  thin 

Pleasant 

D isagreeable, bitter . 

H 

Dark 

Medium 

Burnt 

Very  disagreeable. 

J 

Very  light 

Tenacious  . . 

Pleasant 

Pleasant. 

, K 

Light 

Rather  thin 

Pleasant 

Raw,  but  clean. 

L 

Dark 

Very  thin  . . 

Pleasant 

Rather  like  E. 

M 

Medium  . . 

Medium 

Very  slightly 
burnt 

Burnt,  bitter,  dis- 
agreeable. 

N 

Very  light 

Tenacious, 

granular 

Pleasant 

Pleasant. 

0 

Medium  . . 

Medium 

Peculiar 

, 

Peculiar,  unpleas- 
ant. 

P 

Dark 

Rather  thin 

Very  slight.  . 

Unpleasant. 

R 

Medium  . . 

Medium 

Pleasant 

Pleasant. 

S 

Very  light 

Very  tenacious 

Pleasant 

Sweet,  very  pleas- 
ant. 

T 

Light 

Exceedingly 

tenacious 

Pleasant 

1 

Sweet. 

WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 


517 


altogether  eighteen  samples  of  extract,  which  samples  are  practically  repre- 
sentative of  all  those  offered  on  the  market  for  bakers"  and  confectioners" 
use.  They  were  analysed,  otherwise  tested,  and  systematically  reported 
on  by  one  of  the  authors.  In  the  examination  the  objects  kept  in  view  were 
the  following  : — 

(1)  To  ascertain  the  purity  or  otherwise  of  the  samples. 

(2)  To  determine  their  chemical  composition  in  so  far  as  it  bears  on  their 
quality,  and  mode  of  extraction. 

(3)  To  advise  as  to  their  comparative  suitability  for  use  as  an  adjunct 
in  goods  manufactured  from  flour. 

The  samples  were  examined  as  to  their  physical  characteristics,  observa- 
tions being  made  as  to  their  colour,  consistency,  odour,  and  flavour.  The 
results  of  this  examination  are  embodied  in  the  table  given  on  the  preced- 
ing page. 

Remarks  : — 

E.  Odour  and  flavour  recall  low  grade  honey,  gritty  on  the  palate 
through  presence  of  crystallised  sugar,  colour  a curious  drab,  abnormal  as 
Sj  malt  extract. 

L.  Character  closely  resembles  that  of  E,  but  thinner,  both  devoid  of 
■characteristic  malt  flavour. 

N.  Slightly  crystallised. 

O.  Odour  reminded  one  of  compressed  yeast. 

S.  Flavour  malty,  very  free  from  bitterness. 

T.  Flavour  sweet  but  devoid  of  malt  character,  recalls  brewers"  invert 
■sugar  (see  page  86). 

In  the  course  of  analysis  the  following  determinations  were  made — water, 
mineral  matter,  proteins,  dextrin,  sucrose,  maltose,  and  glucose.  The 
flrst  three  estimations  are  quite  plain.  The  remaining  constituents  may  be 
grouped  together  as  carbohydrates.  Their  separation  into  dextrin,  sucrose 
(cane  sugar),  maltose  and  glucose  was  made  by  methods  described  in  the 
latter  part  of  this  work.  They  give  only  approximate,  but  still  fairly 
accurate,  results.  The  “ reducing  sugars  as  maltose  ""  were  obtained  by 
calculating  the  whole  of  the  precipitated  copper  oxide  as  being  due  to  mal- 
tose. As  throughout  the  whole  series  the  same  processes  were  employed,  the 
Tesults  are  comparable  with  each  other.  The  previously  given  results  of 
analysis  of  extracts  prepared  in  the  author"s  laboratory,  paragraph  632, 
should  be  studied  and  compared  with  those  following  on  page  518. 

Considerable  importance  attaches  to  the  diastatic  capacity  of  malt 
•extracts,  or  the  power  the  extract  possesses  of  activity  on  starch,  converting 
it  into  dextrin  and  maltose.  In  order  to  measure  the  capacity  for  effect- 
ing this  conversion,  the  effect  produced  by  the  extracts  on  flour  was  deter- 
mined, that  used  being  a weak  patent  flour  and  the  same  for  the  whole 
series.  The  tests  were  made  in  the  following  manner — 100  parts  by  weight 
of  flour  were  taken  together  with  2 parts  of  malt  extract,  and  400  parts 
of  water.  These  were  placed  in  a tightly  corked  flask,  thoroughly  shaken 
together,  and  then  maintained  for  4 hours  at  a constant  temperature  of 
140°  F.,  the  flasks  being  frequently  vigorously  shaken.  At  the  end  of  the 
time  the  contents  were  filtered,  and  on  the  clear  filtrate  determinations  were 
made  of  the  total  soluble  matter,  and  of  the  maltose  produced.  As  flour 
a,lways  contains  some  reducing  sugar  and  other  soluble  matter,  these  were 
determined  by  an  experiment  on  the  same  quantities  of  flour  and  water 
only,  allowed  to  stand  in  the  cold  for  4 hours  and  then  estimated  precisely 
like  the  extracts.  Flour  itself  also  contains  diastase,  and  to  determine 
the  effect  produced  by  this  (flour  diastase)  an  experiment  was  made  on  the 
.■same  quantities  of  flour  and  water  only,  maintained  at  140°  F.  for  4 hours. 


518 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Analyses  of  Malt  Extracts. 


Reference  Letter — 

a. 

B. 

1 

i c. 

i 

1 

D. 

E. 

F. 

Water 

27-70 

29-90 

27-90 

26-30 

25-90 

24-80 

Mineral  Matter 

1-25 

1-65 

1-70 

1-60 

1-80 

1-40 

Proteins 

3-81 

4-87 

6-29 

5-40 

6-02 

3-81 

Dextrin 

8-70 

4-60 

4-80 

7-65 

2-70 

10-95 

Sucrose 

3-35 

3-83 

1-91 

4-07 

5-74 

6-46 

Maltose 

42-87 

22-63 

29-29 

47-01 

40-53 

50-02 

Glucose 

12-32 

32-52 

28-11 

7-97 

17.31 

2-56 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

Reducing  Sugars 
Maltose 

as 

62-59 

74-71 

74-31 

59-76 

68-25 

54-11 

Reference  Letter — 

G. 

H. 

j. 

K. 

L. 

M. 

Water 

29-80 

29-20 

25-60 

28-50 

30-60 

28-80 

IMineral  Matter 

1-85 

1-90 

1-15 

1-45 

1-85 

1-75 

Proteins 

9-30 

9-83 

6-77 

6-29 

6-29 

9-12  ' 

Dextrin 

3-30 

3-00 

8-35 

3-75 

3-50 

2-50 

Sucrose 

' Nil 

Nil 

6-46 

1-91 

7-42 

1-91 

Maltose 

23-56 

34-48 

42-23 

35-72’ 

31-30 

28-71  : 

Glucose 

32-19 

21-59 

9-44 

22-38 

19-04 

27-21  1 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00  ; 

Reducing  Sugars 
Maltose 

as 

75-11 

69-05 

57-34 

71-88 

6D79 

72-29 

Reference  Letter — ' 

X. 

0. 

p. 

R. 

s. 

T. 

^ Water 

24-40 

27-30 

28-90 

25-30 

22-20 

18-30 

Mineral  Matter 

1-50 

0-85 

1-55 

1-55 

1-45 

1-35 

Proteins 

7-17 

7-97 

6-38 

7-70 

4-96 

7-62 

Dextrin 

1-30 

3-30 

3-20 

4-45 

8-85 

6-35 

Sucrose 

0-72 

1-19 

Nil 

Nil 

4-31 

8-14 

Maltose 

47-94 

33-92 

37-34 

33-50 

53-65 

46-95 

: Glucose 

16-97 

25-47 

22-63 

27-50 

4-58 

11-29 

100-00 

100-00 

100-00 

100-00 

100-00 

100  00  : 

Reducing  Sugars 
Maltose 

as 

■■  1 

75-11 

74-71 

73-50 

1 

77-53 

1 

60-98 

65-02  : 

WHEAT,  FLOUR,  AND  BREAD  IMPROVERS.  519' 

In  addition,  the  malt  extract  also  contains  maltose  and  other  soluble  matters. 
In  the  following  table,  there  is  given  on 

Line  1,  soluble  matter  normally  present  in  the  flour. 

Line  2,  additional  soluble  matter  resulting  from  the  diastatic  influence  of 
the  flour  upon  itself  during  the  4 hours  at  140°  F.,  being  self-  or  auto- 
digestion. 

Line  3,  soluble  matter  contained  in  the  malt  extract. 

Line  4,  additional  soluble  matter  resulting  from  the  diastatic  action  of 
the  malt  extract  upon  the  flour. 


Soluble  Matters  resulting  from  Action  of  Malt  Extract  on  Flour. 


Reference  Letter — . 

A. 

B. 

c.  i 

n. 

E.  ; 

F. 

Normally  present  in  Flour.  . 

5-52 

5-52 

5-52 

5-52  1 

5-52 

5-52 

Flour,  Auto-digestion 

31-88 

31-88  1 

31-88 

31-88  ^ 

31-88 

31-88 

In  Malt  Extract 

1-44 

1-40  j 

1-44 

1-47  i 

1-48 

1-50 

Malt  Extract  digestion 

5-28 

11-04  1 

1 

16-36 

10-29  ! 

12-12 

8-98 

i Total  

44-12 

49-84 

55-20 

49-16 

51-00 

47-88 

Reference  Letter — . 

G. 

H. 

J. 

Iv. 

L. 

M. 

Normally  present  in  Flour 

5-52 

5-52 

5-52 

5-52 

5-52 

5-52 

! Flour,  Auto-digestion 

31-88 

31-88 

31-88 

31-88 

I 31-88 

31-88 

In  Malt  Extract 

140 

1-41 

1-48 

1-43 

1-38 

1-42 

Malt  Extract  digestion 

18-12 

17-67 

9-36 

17-61 

16-74 

17-10 

Total 

56-92 

56-48 

48-24 

56-44 

55-52 

55-92 

Reference  Letter — . 

N. 

0. 

R. 

R. 

i 

T. 

Normally  present  in  Flour 

5-52 

5-52 

! 

5-52 

5-52 

5.52 

5-52 

Flour,  Auto-digestion 

31-88 

31-88 

31-88 

31-88 

1 31-88 

31-88 

In  Malt  Extract 

1-51 

1-45 

1-42 

1-49 

! 1-56 

1-63 

Malt  Extract  digestion 

13  57 

1595 

14-06 

16-55 

8-28 

10  *77 

Total 

1 

52  48 

1 

54-80 

i 52-88 

1 

55-44 

1 

1 47-24 

1 

49-80 

1 

The  table  on  page  520  gives  the  result  of  determinations  of  reducing  sugars 
calculated  as  maltose.  The  arrangement  is  the  same  as  in  the  preceding 
table. 

The  results  in  both  tables  are  given  in  percentages  of  the  flour  used.. 
The  reducing  sugars  are  throughout  assumed  to  consist  entirely  of  maltose. 
The  amounts  of  “ soluble  matter and  “ reducing  sugar  run  closely 
parallel  throughout  the  whole  of  the  two  series.  It  will  be  observed  that 
flour  itself  possesses  considerable  diastatic  power,  having  converted  over 
one-fifth  of  its  weight  into  sugar  under  the  conditions  of  the  test.  The  dias- 
tatic action  of  the  extracts  varies  from  2*47  per  cent,  of  flour  into  maltose 
with  A to  16*01  per  cent,  with  K. 

There  is  considerable  difficulty  in  detecting  with  certainty  adulterations 
of  malt  extracts,  firstly  because  of  the  great  variations  in  composition. 


520  THE  TECHNOLOGY  OF  BREAD-MAKING. 


Reducing  Sugars  resulting  from  Action  of  Malt  Extract  on  Flour. 


; Reference  Letter — . 

A, 

B. 

c. 

D. 

E. 

F. 

i Normally  present  in  Flour 

1-97 

1-97 

1-97 

1-97 

1-97 

1-97 

Flour,  Auto-digestion 

20-80 

20-80 

20-80 

20-80 

20-80 

20-80 

j In  Malt  Extract 

1-25 

1-49 

1-48 

1-19 

1-36 

1-08 

I Malt  Extract  digestion 

2-47 

’8-85 

13-71 

7-38 

10-60 

6-84 

Total 

26-49 

33-11 

37-96 

31-34 

34-73 

30-69 

Reference  Letter — . 

G. 

H. 

j. 

K. 

L. 

M. 

Normally  present  in  Flour.  . 

1-97 

1-97 

1-97 

1-97 

1-97 

1-97 

Flour,  Auto-digestion 

20-80 

20-80 

20-80 

20-80 

20-80 

20-80 

’ In  Malt  Extract 

1-50 

1-38 

1-14 

143 

1-23 

1-44 

Malt  Extract  digestion 

15-94 

15-42 

7-91 

16-01 

15-57 

15-84 

Total 

40-21 

39-57 

31-82 

40-21 

39-57 

40-05 

Reference  Letter — . 

N. 

0. 

p. 

R. 

s. 

T. 

' Normally  present  in  Flour.  . 

1-97 

1-97 

1-97 

1-97 

1-97 

1-97 

Flour,  Auto-digestion 

20-80 

20-80 

20-80 

20-80 

20-80 

20-80 

In  Malt  Extract 

1-50 

1-49 

1-47 

1-55 

1 22 

1-30 

Malt  Extract  digestion 

11-11 

14-67 

1227 

14-29 

6-95 

9-65 

Total 

35-38 

38-93 

36-51 

38  61 

30-94 

33-72 

resulting  from  different  modes  of  treatment  of  the  same  malt  (see  analyses, 
paragraph  632),  and  secondly  because  malts  themselves  differ  very  consider- 
ably in  composition,  according  to  whether  “ green  ""  or  air-dried,  amber,  or 
high  kiln-dried.  Further,  the  usual  adulterants  consist  of  the  same  constitu- 
■ents  obtained  from  other  and  cheaper  sources. 

The  following  is  an  attempt  at  a classification  of  the  foregoing  extracts  : — 

Whole  Extracts. — The  following  have  a high  proportion  of  maltose  and 
low  glucose,  and  are  similar  in  general  character  to  the  whole  extract  of  a 
good  pale  malt  : — 

D.  Flavour,  low  ; diastase,  medium. 

F.  Over-heated  ; diastase,  low. 

S.  Flavour,  best  of  all  ; diastase,  low. 

Cold  Water  or  Partial  Extracts. — These  are  characterised  by  having  a 
low  proportion  of  maltose  and  high  one  of  glucose.  The  diastase  runs  from 
medium  to  high.  They  are  also  probably  prepared  in  some  cases  from  green 
or  air-dried  malts.  Extracts  of  this  class  lay  themselves  open  to  sophisti- 
cation since  a small  quantity  of  the  air-dried  malt  yields  an  extract  of  very 
high  diastatic  value  ; and  admixture  of  glucose,  dextrinised  starch,  or 
brewers’  invert  sugar,  either  during  or  after  manufacture,  can  easily  be  made, 
Buch  mixtures  would  resemble  the  pure  extracts  of  this  class  very  closely. 

B.  Flavour,  low  ; diastase,  low  ; glucose,  high. 

C.  „ good  ,,  fair. 


521 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS. 


G. 

Flavour,  low  diastase,  high. 

H. 

? ? 

very  low  ,, 

high. 

K. 

5 ? 

fair  ,, 

high. 

M. 

?? 

very  low  ,, 

high. 

0. 

? ? 

low  ,, 

good. 

P. 

j ? 

low  ,, 

moderate. 

R. 

95 

good 

good. 

Unclassified  Extracts. — These  do  not  fall  definitely  into  either  of  the  fore- 
going two  classes. 

A.  On  the  whole  similar  to  ‘‘  whole  extract,''  but  diastase  practically 
absent.  Flavour,  good.  Probably  over-heated  in  earlier  stages  of  manu- 
facture. 

E.  Abnormal.  Dextrin,  very  low.  Flavour,  peculiar.  Diastase,  fair. 
(Adulteration  with  brewers'  invert  sugar  ?) 

J.  Probably  a whole  extract,  mashed  at  a low  temperature,  intermediate 
between  first  and  second  type  extracts.  Probably  somewhat  over-heated 
in  earlier  stages  of  manufacture,  as  diastase  is  low.  Still,  a fair  quality 
extract. 

L.  Abnormal.  In  flavour  resembles  E,  same  suggestion  of  brewers' 
invert  sugar.  The  diastase  is  high.  Dextrin  is  low. 

N.  Abnormal.  Flavour  recalls  brewers'  invert  sugar.  Diastase,  fair. 
Dextrin  is  low. 

T.  Very  low  percentage  of  water,  entire  absence  of  burnt  flavour,  and 
also,  that  of  malt  deficient.  Cane  sugar  high.  Query,  cane  sugar  adultera- 
tion ? 

Careful  examination  of  the  whole  of  these  extracts  leads  to  special 
notice  of  sample  S as  a whole  extract,  and  sample  K as  a type  of  the  highly 
diastatic  extracts. 


636.  Commercial  Bread  Improvers. — These  consist  principally  of  the 
substances  described  in  a previous  paragraph  (631),  either  alone,  or  mixed 
in  various  proportions.  One  of  those  most  extensively  advertised  was 
recently  analysed  by  the  authors  with  the  following  results  : — 

Mineral  Matter  ..  ..  ..  ..  0*20  per  cent. 

Moisture 


Insoluble  Proteins 
Soluble  Proteins 
Other  Soluble  Matter 
Starch,  etc. 


7-55 

3-60 

1*89 

37-36 

49-40 


Opticity  of  20  per  cent,  solution 
Ditto  after  inversion 


100-00 

. . + 8-866° 

..  - 1-200° 


Amount  of  change  . . . . . . . . 10-066° 

Cane  sugar  calculated  from  opticity  determinations,  27  -80  per  cent. 

The  composition  agrees  very  closely  with  that  of  a mixture  of  three 
parts  of  malt  flour  to  one  part  of  cane  sugar. 

637.  Restrictions  on  Use. — It  must  not  be  assumed  because  the  authors 
have  enumerated  these  various  substances  that  are  or  have  been  used  with 
the  object  of  effecting  improvements  in  flour  or  bread,  that  in  their  opinion 
all  such  substances  are  well  adapted  for  that  purpose  or  can  be  recom- 
mended for  such.  Obviously  neither  all  nor  many  of  them  can  be  used 
together,  since  they  aim  at  remedying  opposite  deficiencies.  Thus  some  are 
corrections  of  the  weak  flours,  while  others  deal  with  defects  associated 
with  over- strength.  In  the  language  of  pharmacy,  these  are  incompatibles. 


522 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


If  that  which  is  the  A^Tong  specific  be  applied,  the  remedy  may  be  worse 
than  the  disease. 

The  following  are  the  legal  restrictions  on  the  range  of  materials  that 
may  be  used  in  the  manufacture  of  bread.  The  quotation  is  from  the 
Bread  Acts,  1822  and  1836  : — 

“ Bread  made  of  the  articles  herein  mentioned  may  he  sold. 

II.  And  be  it  [further]  enacted.  That  it  shall  and  may  be  lawful 
for  the  Several  Bakers  or  Sellers  of  Bread  within  [out  of]  the  City  of 
London  and  the  Liberties  thereof,  within  [and  beyond]  the  Weekly 
Bills  of  Mortality,  and  within  [beyond]  Ten  Miles  of  the  Royal  Ex- 
change, to  make  and  sell,  or  offer  for  Sale,  in  his,  her,  or  their  Shops, 
or  to  deliver  to  his,  her,  or  their  Customer  or  Customers,  Bread  made 
of  Flour,  or  Meal  of  Wheat,  Barley,  Rye,  Oats,  Buck  Wheat,  Indian 
Corn,  Peas,  Beans,  Rice,  or  Potatoes,  or  any  of  them,  and  Avith  any 
common  Salt,  pure  Water,  Eggs,  Milk,  Barm,  Leaven,  Potatoe,  or 
other  Yeast,  and  mixed  in  such  Proportions  as  they  shall  think  fit, 
and  AA’ith  no  other  Ingredients  or  Matter  AA'hatsoever,  subject  to  the 
Regulations  herein-after  contained.” 

The  above  section  strictly  limits  the  materials  from  aaLIcIi  bread  may 
be  made.  The  meal  or  flour  of  most  of  the  cereal  bodies  is  permitted,  and 
also  of  peas,  beans,  and  potatoes.  So,  too,  are  eggs  and  milk,  and  any  form 
of  leaven  or  yeast.  The  latter  terms  AA^ould  probably  also  include  any 
substance  used  as  a part  of  a “ ferment.”  Cane  sugar,  glucose,  malt,  malt 
extract,  and  hops,  AA'ould  most  likely  fall  AAuthin  the  category  as  constituents 
of  yeast,  using  that  AA'ord  in  the  AAuder  sense  in  AALich  it  AA^as  understood 
at  the  passing  of  the  Act.  Since  1822,  there  have  been  developments  and 
improvements  in  the  substances  suitable  for  bread-making  purposes.  Arnong 
these  may  be  mentioned  banana-meal,  malt  extract  used  other  than  as  a 
yeast  constituent,  butter  or  other  fats,  cream  of  tartar,  carbonate  of  soda, 
and  other  aerating  bodies.  As  the  Act  stands,  the  use  of  any  of  these  is 
prohibited.  The  laAV  in  this  particular  is  a dead  letter,  but  still  it  remains 
on  the  Statute  Book,  should  any  one  see  fit  to  resurrect  it. 

The  bearing  of  The  Sale  of  Food  and  Drugs  Acts  has  also  to  be  con- 
sidered. Their  general  effect  is  that  the  mixing  of  any  ingredient  AAdth  an 
article  of  food,  so  as  to  render  it  injurious  to  health,  is  prohibited.  Further, 
no  person  may  sell  to  the  prejudice  of  the  purchaser  any  article  of  food 
AA'hich  is  not  of  the  nature,  substance  and  quality  of  the  article  demanded. 
It  may  be  argued  that  flour  or  bread  having  any  addition  made  thereto  is 
not  of  the  nature,  substance  and  quality  of  the  article  demanded.  If  so, 
the  further  question  arises,  if  the  addition  is  in  every  AA^ay  an  improvement, 
and  in  no  AA^ay  an  injury,  has  an  offence  been  committed  ? In  deciding  a 
case  in  AALich  this  point  arose,  the  learned  judge  said  : “ The  AAmrds  ‘ to 
the  prejudice  of  the  purchaser  ’ are  necessary,  because  if  they  had  not  been 
inserted,  a person  might  have  received  a superior  article  to  that  AAfliich  he 
demanded  and  paid  for,  and  yet  an  offence  AA'ould  have  been  committed. 
The  AA'ords  are  intended  to  sIioaa'  that  the  offence  is  not  simply  giving  a dif- 
ferent thing,  but  giving  an  inferior  thing  to  that  demanded  and  paid  for.” 
Presumably,  therefore,  the  addition  of  an  “ improver,”  AALich  does  in  fact 
improAm  the  article,  does  not  come  AAuthin  the  purvieAV  of  the  Act. 

It  AAill  be  noticed  that  most  of  the  suggested  modes  of  improvement 
consist  either  of  modifications  of  the  manufacturing  processes  or  the  ad- 
dition of  substances  AALich  are  themselves  naturally  present  in  flour.  Fur- 
ther, in  those  defective  flours  to  Avhich  it  is  proposed  that  the  additions 
should  be  made,  there  is  less  of  the  substances  than  is  naturally  present 
in  flours  of  the  best  type,  so  far  as  the  particular  defect  proposed  to  be  remedied 
is  concerned. 


WHEAT,  FLOUR,  AND  BREAD  IMPROVERS  523 

638.  General  Opinion  of  Chemical  Authorities. — Public  analysts,  on 
A^'hom  the  responsibility  for  advising  action  on  these  matters  rests,  are 
somewhat  sharply  divided  in  opinion  on  this  point.  This  is  well  illus- 
trated by  their  attitude  toward  certain  operations  in  the  manufacture  of 
vinegar.  Among  the  substances  naturally  present  in  vinegar  there  are  some 
which  very  much  impair  its  keeping  qualities.  In  consequence,  vinegar 
brewers  have  devised  methods  of  removing  these  objectionable  bodies. 
In  discussing  this  treatment  of  vinegar,  the  following  opinions  were 
expressed  by  high  chemical  authorities.  A speaker  on  one  side  wished 
to  protest  against  the  removal  of  these  bodies,  and  “ thought  that  the 
manufacturer  had  absolutely  no  right  to  effect  such  a removal.  The 
removal  was  prejudicial  to  the  purchaser.  . . . Here  again  he  was  of 
opinion  that  the  long-recognised  and  legitimate  modes  of  manufacture 
should  be  adhered  to,  and  the  introduction  of  chemical  meddling  with 
food  materials  resisted.  It  should  not  be  left  to  the  discretion  of  the  manu- 
facturer of  articles  of  food  to  say  which  constituents  were  valuable  and 
essential  and  which  were  not,  and  in  no  case  should  such  removal  be  effected 
without  due  notice  to  the  purchaser."' 

The  following  speaker  “ entirely  disagreed  with  the  preceding  one,  tliat 
a vinegar  manufacturer  was  not  at  liberty  to  remove  things  prejudicial  to 
vinegar.  It  was,  in  his  opinion,  the  manufacturer’s  business  to  make  good 
vinegar,  and  so  long  as  he  sold  it  for  \vhat  it  was,  he  was  at  perfect  liberty 
to  remove  any  objectionable  constituents  which  impaired  its  qualities.” 
The  same  line  of  argument  would  justify  the  removal  of  undesirable  colour- 
ing matter  from  flour.  The  speaker  would  probably  agree  that  it  is  the 
business  of  the  miller  and  baker  respectively  to  make  the  best  possible 
flour  and  bread,  though  it  does  not  quite  follow  that  he  would  approve  of 
the  addition  of  commendable  bodies  as  well  as  the  removal  of  those  w'hich 
are  objectionable. 

Critics  as  a class  have  not  been  famed  for  their  constructive  capacity, 
and  it  is  only  fair  to  remember  that  the  manufacture  of  vinegar,  of  flour 
and  of  bread,  in  common  with  that  of  most  other  commodities,  has  been 
slowly  progressive  in  its  developments,  as  the  result  of  the  application  of 
improvements  devised  by  the  manufacturers  themselves.  It  would  there- 
fore seem  scarcely  logical  to  step  in  at  any  moment  and  say  these  articles 
of  food  shall  consist  of  bodies  made  by  the  methods  so  far  devised  and 
gradually  adopted  by  the  makers  ; but  they,  the  manufacturers,  shall  not 
be  permitted  to  employ  any  further  improvements  they  may  invent  or 
discover.  The  public  may  safely  be  trusted  to  discriminate  between  those 
modifications  wliich  in  their  opinion  are  improvements  and  those  wdiich 
are  not.  It  follow^s  that  in  this  direction  liberty  of  action  should  be  allow^ed 
to  manufacturers,  subject  to  nothing  being  permitted  wliich  is  to  the 
prejudice  of  the  purchaser,  or  is  injurious  to  health.  If  any  strengthening 
of  the  present  law^  be  deemed  advisable,  it  is  again  suggested  that  it  should 
be  in  the  direction  of  the  establishment  of  a Court  of  Reference  on  the  lines 
indicated  on  page  508. 

639.  Notice  of  Mixture. — By  Section  8 of  the  Sale  of  Food  and  Drugs 
Act,  1875,  it  is  specially  enacted  that,  subject  to  certain  conditions,  it  shall 
not  be  an  offence  to  sell  an  article  of  food  mixed  with  any  matter  or  ingredi- 
ent not  injurious  to  health,  if  at  the  time  of  delivering  such  article  the  vendor 
“ shall  supply  to  the  person  receiving  the  same  a notice,  by  a label  distinctly 
and  legibly  wultten  or  printed  on  or  with  the  article  to  the  effect  that  the 
same  is  mixed.”  It  is  often  urged  that  if  certain  additions  to  flour  or  bread 
are  in  fact  improvements,  the  vendor  w'ould  fully  comply  with  the  law' 
and  satisfy  general  requirements,  if  the  article  w'ere  sold  with  a declaration 


524 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  such  addition  in  the  form  required  by  the  section. just  quoted  from  the 
Act.  To  this,  the  vendor  usually  raises  the  objection  that  any  such  declar- 
ation might  be  used  to  his  injury  by  rival  traders.  Further,  that  the  pro- 
ceedings of  some  officials  responsible  for  the  administration  of  these  Acts 
renders  such  a course  impossible.  It  must  be  admitted  that  there  is  some 
force  in  the  latter  of  these  contentions.  While  this  chapter  was  being 
written,  the  following  was  brought  to  the  notice  of  the  authors.  The  Chief 
Foods  Inspector  reported  to  the  Sanitary  Committee  of  one  of  the  largest 
boroughs  in  England  that  calcium  phosphate  was  being  added  to  flour 
and  bread  by  millers  and  bakers.  He  then  comments  as  follows  : — 

“ I need  not  point  out  to  you  and  the  medical  members  of  the  Committee 
the  extreme  undesirability  of  this  mixture  being  added  to  bread,  for,  as 
you  are  aware,  phosphorus  and  its  compounds  are  spinal  and  brain  stimu- 
lants and  the  constant  stimulation  of  these  centres  with  phosphorus  is  clearly 
contra-indicated.  In  my  opinion  the  use  of  this  adulterant  should  be  most 
strongly  put  down,  as  the  adulterated  loaf  is  harmful  in  every  way,  especi- 
ally to  those  with  neurotic  temperaments.” 

The  cardinal  error  of  this  statement  is  that  the  medicinal  properties  of 
phosphorus  are  ascribed  to  the  calcium  phosphate,  whereas  therapeutically 
they  have  nothing  in  common.  Because  sodium  would  take  Are  in  the 
mouth  and  chlorine  would  instantly  suffocate,  and  therefore  both  are 
regarded  as  virulent  poisons,  it  would  be  just  as  logical  to  argue  that  sodium 
chloride  or  common  salt  is  a most  harmful  substance,  and  therefore  its 
use  should  in  every  case  be  regarded  as  an  adulterant.  Whatever  evidence 
might  be  forthcoming  that  this  substance  is  harmless  and  even  beneficial, 
and  however  fully  it  might  be  accepted  by  a Court  of  Justice,  it  would 
now  be  commercially  impossible  for  any  miller  or  baker  to  declare  the 
admixture  of  calcium  phosphate  in  the  district  where  this  report  is  circulated 
and  accepted. 


CHAPTER  XXI. 


THE  NUTRITIVE  VALUE  AND  DIGESTIBILITY  OF  BREAD. 


640.  Nutrition  and  Food. — Nutrition  may  be  regarded  as  the  process 
of  supplying  the  materials  necessary  in  order  to  effect  the  growth  and 
development  of  living  organisms,  and  the  maintenance  in  a healthy  con- 
dition  of  those  organisms  when  fully  developed.  The  human  organism 
is  for  practical  purposes  the  only  being  whose  requirements  need  be  here 
considered.  Food  may  be  regarded  as  that  which  when  taken  into  the 
body  provides  material  for  its  growth  and  development,  the  reparation  of 
the  waste  of  its  tissues,  the  production  of  heat,  and  the  energy  necessary 
both  for  internal  and  external  muscular  work.  In  other  w'ords  food  com- 
prises those  substances  which  are  available  for  purposes  of  nutrition. 

Food  substances  or  “ nutrients  ” are  derived  from  the  animal,  vegetable, 
and  mineral  kingdom.  They  belong  to  the  following  chemical  groups  of 
substances — proteins  and  closely  allied  bodies,  as  sclero-proteins  (gelatin), 
carbohydrates,  fats,  and  mineral  matters,  especially  those  containing  lime, 
potassium,  sodium,  phosphorus,  and  chlorine,  also  water.  An  old  classifi- 
cation of  nutrients  was  into  flesh  formers,  as  proteins  ; heat-formers,  as 
carbohydrates  and  fat  ; and  bone-formers,  as  calcium  phosphate.  A more 
modern  arrangement  is  into  the  two  groups  of  tissue-formers  and  work  and 
heat  producers  as  under  : — 


Tissue- formers.  Work  and  Heat  Producers. 

Proteins.  Proteins. 

Mineral  Matters.  Sclero-Proteins. 

Water.  Carbohydrates. 

Fats. 

(?)  Mineral  Matters  and  Water. 

The  proteins  are  distinguished  from  among  the  other  organic  constituents 
of  food  by  their  being  capable  of  exercising  both  the  above-mentioned 
functions  of  nutrition. 

In  estimating  the  nutritive  value  of  foods  they  are  subjected  to  tests 
of  three  kinds  : — 

I.  Chemical  analysis,  by  which  the  proportions  of  the  various  constitu- 
ents are  determined. 

II.  The  heat  produced  by  their  combustion  in  oxygen,  this  being  a 
measure  of  their  heat  and  energy  producing  capacity. 

III.  Physiological  tests,  in  which  their  degree  of  capacity  for  utilisation 
by  the  body  is  measured. 

The  general  composition  as  ascertained  by  chemical  analysis  need  not 
be  further  enlarged  on  here. 


641.  Heat  of  Combustion. — This  requires  some  further  description. 
Excluding  the  mineral  matters  and  water,  the  other  food  constituents  are 
all  combustible,  and  each  variety  evolves  a definite  amount  of  heat  when 
completely  burned,  depending  on  its  composition.  The  unit  measure  of 
heat  is  that  which  is  required  to  raise  I gram  of  water  from  0°  to  1°  C.,  and 
this  is  called  a “ calorie.”  For  food  valuations  a larger  unit  is  convenient  ;; 

525 


526 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  accordingly,  that  selected  is  the  large  or  kilo -calorie,  which  is  the 
amount  of  heat  necessary  to  raise  1 kilogram  (1,000  c.c.)  from  0°  to  1°  C. 
The  kilo-calorie  or  large  Calorie  is  indicated  by  its  being  spelled  with  a 
capital  C.  When  burned  with  an  excess  of  oxygen  the  whole  of  the  con- 
stituents of  any  food  are  completely  oxidised  ; but  when  consumed  in  the 
body,  they  are  finally  excreted  in  only  a partially  oxidised  state,  and  there- 
fore some  allowance  must  be  made  for  the  heat  still  remaining  unused  in 
these  bodies.  That  having  been  done,  the  amount  of  energy  liberated  by 
any  food  follows  just  the  same  laws  as  though  it  were  burned  in  the  ordinary 
way.  The  heat  liberated  within  the  body  by  the  following  substances  is, 
according  to  Hutchison  : — 

One  gram  of  Proteins  . . . . . . . . 4T  Calories. 

,,  ,,  Carbohydrates  . . . . . . 4T  ,, 

,,  ,,  Fat  . . . . . . . . 9-3  ,, 

The  energy  value  of  a food  is  easily  calculated  from  its  analysis.  If  the 
percentages  of  proteins  and  carbohydrates  are  multiplied  by  4T,  and  that 
of  the  fat  by  9*3,  the  sum  of  these  numbers  gives  the  energy  in  Calories  of 
the  food  itself.  Thus  if  a sample  of  flour  gives  the  following  results  on 
analysis,  the  heat  energy  is  as  shown  : — 

Per  cent.  Factor.  Heat  of  Combustion. 

Protein  11-08  x 4-1  = 45-428 

Carbohydrates  . . . . . . 76-85  x 4-1  = 315-085 

Fat 1-15x9-3=  10-695 


Kilo-Calories  per  100  grams  ..  ..  ..  ..  371-208 

,,  ,,  ,,  1 gram  . . . . . . . . 3-71208 

Gram-calories  per  1 gram  . . . . . . . . 3712-08 

Snyder,  to  whose  results  a somewhat  extended  reference  follows,  returns 
his  “ Heat  of  combustion  ''  in  terms  of  the  complete  oxidation  obtained 
by  burning  in  oxygen,  and  without  any  deduction  for  incomplete  combustion 
in  the  body.  He  uses  therefore  the  following  factors  for  calculating  the 
heat  of  combustion  from  the  analysis.  They  are  applied  to  the  same  analysis 
of  flour. 

Per  cent.  Factor.  Heat  of  Combustion. 

Protein  ..  ..  ..  ..  11-08  x 5-9  = 65-372 

Carbohydrates  . . . . . . 76-85  x 4-2  = 322-770 

Fat 1-15x9-3=  10-695 


Kilo-Calories  per  100  grams  . . . . . . . . 398-837 

,,  ,,  ,,  1 gram  . . . . . . . . 3-988 

Ditto  determined  direct  on  the  flour  . . . . 4-032 

642.  Digestibility. — In  making  physiological  tests  this  term  is  used  as 
meaning  the  measure  of  tlie  total  amount  of  the  food  utilised  or  absorbed 
by  the  body.  The  principle  of  the  determination  is  the  weighing  the  whole 
of  the  food  of  known  composition  eaten  during  a certain  period,  and  the 
estimation  of  the  weight  and  composition  of  that  which  is  ejected  in  the 
excreta.  The  difference  is  the  amount  absorbed.  The  more  popular 
meaning  attached  to  the  word  digestibility  relates  to  the  comparative  ease 
or  discomfort  with  which  the  food  passes  through  the  stomach.  In  view 
of  the  use  of  the  word  in  this  latter  sense,  Hutchison  has  proposed  to  use 
the  word  “ absorbability  ''  instead  of  digestibility  when  dealing  with  the 
proportion  of  a food  which  is  absorbed  or  utilised  by  the  body.  But  as 
most  writers  still  employ  digestibility  as  synonymous  with  absorbability 
it  will  be  used  in  that  sense  in  this  work. 


THE  NUTRITIVE  VALUE  OF  BREAH. 


527 


643.  Amount  of  Food  required. — To  discuss  this  question  adequately 
would  require  much  more  space  than  can  possibly  be  devoted  to  it  here. 
The  student  is  therefore  referred  to  Food  and  Dieteticd  by  Hutchison  for 
full  information  on  this  subject.  From  his  most  interesting  book  the  follow- 
ing summary  is  quoted  : — 

“ One  may  sum  up  the  standard  amounts  of  the  different  nutritive  con- 
stituents required  daily  thus  ; — 

Protein  . . . . . . . . . . . . 125  grams. 

Carbohydrate  . . . . . . . . . . 500  ,, 

Fat  . . . . . . . . . . . . . . 50  ,, 

These  would  yield  the  following  amount  of  energy  in  Calories  : — 

Protein 125  X 4-1  = 512-5 

Carbohydrate  . . . . . . 500  x 4-1  = 2050-0 

Fat  50  X 9-3  = 465-0 


Total  . . . . . . . . . . = 3027-5  Calories. 

Or,  in  terms  of  carbon  and  nitrogen  : — 

125  grams  of  Protein  = 20  grams  N and  62  grams  C. 

500  ,,  ,,  Carbohydrate  = 200  ,,  ,, 

50  ,,  ,,  Fat  = 38  ,,  ,, 


Total  = 20  grams  N and  300  grams  C. 

Such  a standard  may  be  regarded  as  the  minimum  for  a man  of  average 
build  and  weight,  and  doing  a moderate  amount  of  muscular  work.  . . . 
In  such  standards  the  ratio  of  protein  to  carbohydrates  and  fat  taken  to- 
gether is  of  some  importance.  It  is  called  the  nutritive  ratio.  If  I part 
of  fat  be  counted  as  2-25  parts  of  carbohydrate,  the  nutritive  ratio  . . . 
is  as  I to  4-9.  In  this  ratio  we  have  an  index  of  the  proportion  which  the 
building  material  of  the  diet  ought  to  bear  to  its  purely  energy-yielding 
constituents."'*  For  the  figure  4-9,  that  of  5-3  more  closely  represents  the 
average  ratio  of  a number  of  authorities.  In  the  diet  of  a child  the  ratio 
should  be  approximately  as  1 to  4-3. 

644.  Nutritive  Ratio  of  Wheat  Products. — The  following  figures  of 
analysis  are  taken  from  those  of  spring  and  winter  American  wheats  and 
their  products  : — 


( 

Protein. 

Carbohydrates. 

Fat. 

Xutritive 

Ratio 

Spring  Wheat  . . 

14-35 

70-37 

2-74 

1 : 5 -3 

Baker’s  Flour  . . 

14-88 

69-99 

2-00 

1 : 5 -0 

Patent  Flour 

12-95 

73-55 

1-45 

1 : 5 -9 

Bran 

16-28 

56  21 

5-03 

1 : 4-1 

Germ 

33-25 

35-19 

15-61 

1 : 2-1 

Winter  Wheat  . . 

12  43 

71-67 

2-46 

1 : 6 -2 

Baker’s  Flour  . . 

13-13 

71-52 

1-77 

1 : 5 -4 

Patent  Flour 

10-18 

78-28 

1-05 

1 : 7 -9 

For  the  moment,  neglecting  the  waste  through  variations  in  digestibility, 
spring  wheat  and  spring  wheat  baker’s  flour  contain  sufficient  protein  to 
comply  with  the  standard  nutritive  ratio.  Bran  contains  a large  excess  of 
protein,  while  that  in  germ  is  approximately  two  and  a half  times  as  much 
as  required  by  the  standard.  Evidently  a mixture  of  germ  and  white 


528 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


flour  may  be  made  in  such  proportions  as  to  comply  exactly  with  the  nutri- 
tive ratio.  The  spring  patent  is  slightly  deficient  in  protein,  but  the  de- 
ficiency is  but  small.  The  winter  wheat  and  its  products  are  all  lower  in 
protein  matter.  An  interesting  point  is  that  the  spring  patent  flour  has 
very  nearly  the  same  ratio  as  the  baker’s  flour  from  winter  wheat.  The 
baker’s  flours  have  a slightly  higher  nutritive  ratio  than  the  wheats  from 
which  they  were  obtained,  while  the  ratio  is  definitely  lower  in  the  case  of 
the  patent  grades.  English  wheats,  and  the  general  average  of  wheats 
milled  in  England,  have  a lower  protein  content  than  spring  American  wheat. 
From  analysis  of  a number  of  representative  English  millers’  flour  the- 
following  figures  have  been  deduced  : — 


Moisture 
Proteins  . . 
Carbohydrates  . 
Fat 
Ash 

Cellulose 


14*0  per 

cent. 

ILO  „ 

72*7  „ 

L5  „ 

0-5  ., 

? ? 

0-3  „ 

ICOO 


Nutritive  ratio..  ..  ..  ..  ..  6-9 


Viewed  from  the  standpoint  of  a perfectly  balanced  food,  such  flour  is 
markedly  deficient  in  fat,  and  slightly  deficient  in  proteins.  In  an  actual 
mixed  diet,  these  deficiencies  are  made  up  by  the  addition  of  butter  to- 
bread,  and  the  consumption  therewith  of  such  substances  as  lean  meat  and 
cheese. 


645.  Relative  Digestibility  of  White  and  Brown  Bread,  Lauder  Brunton. 
and  Tunnicliffe. — The  results  of  a research  by  these  gentlemen  were  pub- 
lished in  1899.  They  selected  the  best  white  bread  of  a West  End  London 
baker,  and  a whole-meal  bread,  i.e.,  one  made  from  the  whole  of  the  wheat 
granule.  The  writers  state  that  chemically  the  chief  substances  in  which 
white  bread  is  deficient  as  compared  with  browm  are  ash  (consisting  mostly 
of  phosphates  of  potash,  lime  and  soda),  nitrogenous  matters,  fatty  matters, 
and  cellulose.  The  results  of  analyses  of  the  two  breads  selected  for 
experiment  are  set  out  in  Table  I,  page  529. 

In  order  to  determine  their  digestibility  in  saliva,  a sufficiency  of  that 
fluid  was  carefully  collected,  and  filtered,  and  the  following  mixtures  made- 
with  No.  I.  white  bread,  and  No.  II.  brown  bread,  respectively  : — 

Bread,  white  and  Brown  respectively  . . . . 2 grams. 

Distilled  Water  . . . . . . . . . . 30  c.c. 

Mixed  Saliva  and  Distilled  Water,  equal  volumes  30  c.c. 

The  mixtures  were  maintained  at  from  35-40°  C.  for  30  minutes,  then 
boiled,  and  the  sugar  in  each  mixture  estimated. 

In  order  to  determine  their  relative  pancreatic  digestibility,  the  following 
mixtures  were  made  : — 

Bread,  White  and  Brown  respectively  . . . . 2 grams. 

Benger’s  Liquor  Pancreaticus  . . . . . . 15  c.c. 

Distilled  Water  . . . . . . . . . . 45  c.c. 

A few  drops  of  a saturated  solution  of  sodium  carbonate. 


Tliese  mixtures  were  maintained  at  37°  C.  for  7 hours,  then  boiled,  and 
sugar  estimated.  The  results  are  shown  in  Table  II,  page  529. 

From  tliese  tables  it  will  be  seen  that  the  starch  of  white  bread  is  much 
more  rapidly  and  completely  acted  on  than  that  of  brown  bread.  Experi- 


THE  NUTKITIVE  VALUE  OF  BREAD. 


529 


merits  were  next  made  on  the  digestibility  of  the  nitrogeneous  constituents. 
For  this  purpose  they  were  submitted  to  Gastro- Pancreatic  digestion.  The 


Table  I. 


I’ercentage  Composition  of 

i 

Constituents. 

Bread  as  Supplied. 

Water-Free  Breads.  | 

i 

White 

Bread. 

Brown 
Brea  1. 

White 

Bread. 

Brown 

Bread. 

Water 

Per  cent. 

39  10 

Per  cent. 

40-18 

Per  cent. 

Per  cent. 

Dry -Substance 

60-90 

59-82 

— 

— 

Total  Ash  . . 

0-59 

i 1-88 

0-97 

3-14 

Phosphoric  Acid  . . 

0-16 

0-51 

0-26 

0-85 

Soluble  Matter 

4-73 

i 7-54 

7-77 

12-60 

Nitrogen 

1-32 

1-25 

2-17 

2-09 

Albumin,  calculatedfrom  Nitrogen  ^ 

8-25 

7-87 

13-54 

13-16 

Pure  Albumin  ^ . . 

7-34 

7-86 

12-05 

13-15 

Soluble  Nitrogenous  Matter  ^ 

0-61 

^ 0-73 

1-00 

1-22 

Starch  and  Saccharine  Matters,  etc. 

51-85 

49-44 

— 

— 

Starch 

38-45 

39-18 

63-13 

65-49 

Sugar  (Maltose) 

1-19 

1-77 

1-95 

2-96 

Dextrin 

0-84 

0-71 

1-38 

1-19 

Cellulose 

0-24 

1-06 

0-39 

1-68 

Fat  . . 

0-21 

0-63 

0-34 

1-05 

Acidity  (Lactic  Acid) 

0-19 

0-29 

— 

— 

Loss  of  water  in  fifteen  days 

9-23 

! 

^ Total  proteins.  ^ Insoluble  proteins.  ^ goluble  proteins  and  other  nitrogenous  bodies. 


Table  II. 


Particulars. 

No.  I. 

White  Bread. 

No.  II. 
Brown  Bread. 

Percentage  of  total  possible  Sugar  calculated 
from  Starch,  on  Dried  Solids  of  Bread 

70-14 

72-76 

Actual  formed  Sugar — 

(a)  Saliva,  half  hour 

21-64 

9-99 

[h)  Pancreas,  7 hours 

33-07 

19-75 

Percentage  of  actual  formed  Sugar  to  possible 
Sugar — 

(a)  Saliva,  half-hour 

30-85 

13-73 

{h)  Pancreas,  7 hours  . . 

51-42 

27-14 

following  mixtures  were  made  : — 

Bread,  White  and  Brown  respectively  . . . . ' 2 grams. 

Benger’s  Liquor  Pepticus  . . . . . . . . 10  c.c. 

Distilled  Water  . . . . . . . . . . 50  c.c. 

These  were  maintained  at  37°  C.  for  10  hours,  then  boiled  and  filtered. 
The  residue  was  then  submitted  to  pancreatic  digestion,  in  the  same  manner 
as  before  described,  for  6 hours,  and  again  filtered.  The  residual  nitrogen 
was  then  determined  and  calculated  into  proteins.  The  difference  between 
this  figure  and  the  quantity  originally  present  in  the  bread  was  regarded 

M M 


530 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


as  having  been  digested.  Another  pair  of  samples  was  subjected  to  pan- 
creatic digestion  only,  in  the  same  manner  as  before,  and  the  residual  pro- 
teins determined  after  11  hours’  treatment.  The  following  table  shows 
the  results  : — 


Particulars. 

White. 

Brown. 

Percentage  of  Nitrogenous  Matter  digested,  cal- 
culated to  total  Nitrogenous  Matter  in  Water- 
free  Breads  — 

Per  cent.  1 

Per  cent. 

{a)  Gastro-pancreatic  Digestion — 

Ten  hours  Gastric 

Six  hours  Pancreatic 

]-  74-89 

60-71 

1 

(6)  Pancreatic  alone,  II  hours 

79-38 

69-81 

From  this  table  it  will  be  seen  that  in  tlie  case  of  the  gastro-pancreatic 
digestion  of  white  bread,  14  per  cent,  more  of  the  nitrogenous  constituents 
Avere  digested  than  in  the  case  of  brown.  In  pancreatic  digestion  the  excess 
of  nitrogenous  matter  digested  in  white  bread  amounts  to  nearly  10  per 
cent. 

The  Avriters  next  experimented  on  the  cellulose  ; as  might  be  expected 
they  found  a much  greater  residue  from  the  brown  bread,  which  was  in 
thick  flakes  ; Avhereas  that  from  the  Avhite  bread  was  in  very  small  thin 
flakes.  They  regard  the  cellulose  of  the  former  as  producing  an  irritant 
action  upon  the  intestines,  by  which  the  sluggish  intestines  may  be  stimu- 
lated up  to  the  normal  condition.  On  the  other  hand  by  causing  excessive 
peristalsis  in  irritable  intestines,  digestion  may  only  partially  take  place, 
and  both  a loss  of  nutritive  material  and  diarrhoea  may  ensue. 

The  wTiters  are  of  opinion  that  probably,  in  fact  almost  certainly,  all 
the  salts  and  all  the  fat  in  bread  are  absorbed,  and  therefore  in  this  respect 
at  any  rate,  if  the  fact  that  brown  bread  may  remain  for  less  time  in  the 
alimentary  canal  is  neglected,  brown  bread  is  superior  to  white. 

From  the  above  results  they  formulate  the  folloAving  conclusions  : — 

1.  White  bread  is,  weight  for  weight,  more  nutritious  than  brown. 
Therefore,  it  appears  the  preference  given  by  operatives  in  large  towns  for 
Avhite  bread  has,  to  a certain  extent,  a sound  physiological  basis. 

2.  In  the  case  of  people  with  irritable  intestines,  Avhite  bread  is  to  be 
preferred  to  brown. 

3.  In  the  case  of  people  with  sluggish  intestines,  broAvn  bread  is  prefer- 
able to  white,  as  it  tends  to  maintain  regular  peristaltic  action,  and  ensure 
regular  evacuation  of  the  bowels,  with  all  its  attendant  advantages. 

4.  In  cases  Avhere  the  proportion  of  mineral  ingredients,  and  especially 
of  lime  salts,  in  other  articles  of  food  or  drink  is  insufflcient,  brown  bread 
is  preferable  to  white.  It  is  possible  that  in  the  case  of  operatives  living 
chiefly  upon  bread  and  tea,  the  preference  for  white  bread  which  obtains 
in  large  towns  may  be  responsible,  in  part  at  least,  for  the  early  decay  of  the 
teetli  of  those  living  on  such  a dietary. 

5.  An  abundant  supply  of  mineral  constituents  is  especially  required  in 
pregnant  and  suckling  women  and  in  growing  children,  in  order  to  supply 
material  for  the  nutrition  of  the  foetus,  the  constituents  of  the  milk,  and 
for  the  growth  of  the  tissues,  especially  of  the  bones.  In  such  cases,  if 
mineral  salts,  especially  those  of  calcium,  are  not  supplied  by  other  food- 
stuffs, drinks,  or  medicines,  brown  bread  is  preferable  to  white. 

G.  If  the  dietary  is  insufficient  in  fat,  or  if  the  patient  is  unable  readily 


THE  NUTRITIVE  VALUE  OF  BREAD.  531 

to  digest  fat  in  other  forms,  brown  bread  may  possibly  be  preferable  to 
■white.  {Bartholomew’s  Hospital  Reports,  vol.  xxxiii.) 

646.  Bread  : Digestive  and  Nutritive  Properties,  Jago. — In  1899,  a com- 
munication was  made  by  one  of  the  authors  to  the  National  Association 
of  Master  Bakers  of  the  United  Kingdom,  under  the  above  title.  It  con- 
sisted of  the  results  obtained  by  submitting  various  samples  of  bread  to 
artificial  digestion  in  the  following  manner  ; — 

Method  of  experiment. — As  digestive  agents.  Armour’s  standard  pepsin  and 
pancreatin  were  employed.  Definite  weights  of  the  crumb  of  bread,  water, 
acid  and  pepsin  were  taken  ; these  were  rubbed  down  into  a pulp,  and 
transferred  to  a flask,  and  then  kept  at  body  temperature  (98°  F.  = 36-6°  C.) 
for  3 hours.  At  the  end  of  that  time  definite  quantities  of  alkali  and 
pancreatin  were  added  and  the  digestion  continued  for  an  additional  5 
hours.  The  following  determinations  were  then  made 

In  soluble  portion. — (1)  Peptones,  or  fully  digested  proteins  ; (2)  pro- 
teoses, or  partly  digested  proteins  ; (3)  proteins  simply  dissolved  ; (5) 

maltose  and  dextrin  as  results  of  carbohydrate  digestion  ; (8)  phosphates 
obtained  in  soluble  form. 

In  imdissolved  portion. — (4)  Undissolved  proteins  ; (6)  starchy  matter 
undissolved.  This  was  determined  by  separating  the  branny  matter  by 
means  of  a very  fine  sieve.  (7)  Branny  matter. 

Description  of  hreids  examined.  These  were  : — 

I.  Whole-meal  bread. — This  was  a plain  whole-meal  loaf  made  from  a 
rather  coarse  meal. 

II.  Malt  digestive  bread. — This  was  made  from  a mixture  of  white  flour, 
fine  whole  meal,  malt  extract,  and  no  chemicals  for  raising  purposes. 

III.  Best  quality  white  bread. — Baker’s  ordinary  loaf. 

IV.  Best  quality  white  bread. — Baker’s  ordinary  loaf. 

V.  Straight  flour  from  all  English  wheat. — This  was  specially  prepared 
by  taking  fine  English  whole-meal  and  hand  dressing  it  through  a fine  sieve. 
This  flour  approximated  as  nearly  as  possible  to  an  old-fashioned  stone- 
milled  and  bolted  flour  from  English  wheat. 

VI.  Malt  digestive  bread. — This  was  similar  to  No.  II.,  except  that  it 
contained  in  addition  cream  of  tartar  and  bicarbonate  of  soda. 

VII.  Germ  bread. — This  was  prepared  from  a mixture  of  white  flour 
and  wheat  germ. 

No.  I.  is  a sample  of  baker’s  ordinary  whole-meal  bread.  Nos.  III.  and 
IV.  were  samples  of  baker’s  best  bread  made  in  the  ordinary  way  of  business. 
Nos.  II.,  V.,  VI.  and  VII.  were  specially  prepared  representations  of  special 
types,  but  must  not  be  regarded  as  examples  of  any  particular  proprietary 
articles. 

Composition  of  breads. — Analyses  were  made  of  the  breads  themselves 
with  the  results  shown  in  the  table  on  following  page.  The  “ gross  nutritive 
ratio  ” is  that  of  the  proteins  as  against  the  whole  of  the  other  solid  con- 
stituents taken  as  carbohydrates.  The  fat  being  reckoned  as  starch  is  under- 
valued, but  this  is  roughly  compensated  by  the  cellulose,  salts,  etc.,  being 
reckoned  as  nutritive  carbohydrates.  In  consequence,  this  figure  must  be 
regarded  as  only  approximate.  The  total  energy  in  Calories  is  also  deficient 
through  fat  not  being  separately  reckoned. 

The  water  of  the  white  bread  is  considerably  less  than  that  of  any  of 
the  others.  One  result  of  that  is  that  although  the  proteins  of  whole-meal 
bread  are  more  on  the  dried  solids  than  are  those  of  white  bread,  yet  the 
percentage  per  weight  of  bread  as  sold  and  eaten  is  more  with  the  white 
than  the  whole-meal  bread.  The  proteins  of  the  “ All  English  ” bread. 
No.  V.,  are  less  than  those  of  the  baker’s  ordinary  bread.  In  the  case  of 


532 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Constituents. 

I.  Whole  Meal. 

II.  Malt  Bread. 

III.  White  Bread. 

Natural. 

Dried. 

Natural.  1 

Dried. 

Natural. 

Dried. 

Moisture  . . 

49-91 

1 

44-77 

40-10 

Proteins  . . 

6-29 

12-55 

6-40 

11-58 

i 7-06 

11-78 

Soluble  Extract  . . 

8-84 

17-65 

15-56 

28-17 

11-92 

19-90 

Starch,  Fat,  etc. . . 

34-96 

69-80 

33-27 

60-25 

40-92 

68-32 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

Gross  Nutritive  ratio 

7-0 

7-0 

7-6 

7-6 

7-5 

7-5 

Total  Energy  in  Calories 

210  4 

420-0 

232-0 

420-0 

251-6 

j 

420-0 

lA".  AA'hite  Bread. 

1 Y.  All  English. 

VI.  Malt  Bread. 

VII.  Germ  Bread. 

Natural. 

Dried. 

Natural. 

Dried. 

Natural. 

Dried . 

Natural. 

Dried. 

Moisture  . . 

39-64 

44-10 

41-10 

45-40 

Proteins  . . 

Soluble  Extract,  Starch, 

6-99 

11-8 

6-55 

10-93 

6-33 

10-74 

10-36 

18-95 

etc. 

53-37 

88-42 

49-35 

89-07 

57-57 

89-26 

44-24 

81-05 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

Gross  Nutritive  ratio  . . 

7-6  1 

7-6 

8-1 

8-1  ! 

8-3 

8-3 

4-3 

1 4-3 

Total  Energy  in  Calories 

253-5 

420-0 

234-8 

420-0 

247-4 

o 

6 

229-3 

420-0 

the  whole  of  the  breads  Avith  but  one  exception,  the  gross  nutritive  ratio- 
falls  below  the  requirements,  5*3,  of  a well-balanced  food.  In  the  germ 
bread,  proteins  are  in  considerable  excess,  and  bread  of  this  kind  acts  as  a 
sparer  of  more  expensive  protein  foods. 

Results  of  Digestion. — Before  giving  these  it  must  be  mentioned  that  the 
first  tliree  tests  were  made  together.  It  was  subsequently  thought  desirable 
to  make  the  other  tests,  numbered  V.,  VI.  and  VII.  Unfortunately,  the 
original  stock  of  pepsin  and  pancreatin  Avas  entirety  exhausted  betAveen  the 
tAvo  sets  of  experiments,  and  a fresh  supply  was  obtained  direct  from  the 
manufacturers.  In  order  to  test  the  ncAV  pepsin  and  pancreatin,  another 
test  Avas  made  on  the  best  white  bread.  No.  IV.  sample  being  of  the  same 
make  and  quality  as  No.  III.  Consequently,  the  members  of  the  first 
group,  I.,  II.  and  III.,  and  of  the  second  group,  IV.,  V.,  VI.  and  VII.,  are 
comparable  among  each  other  ; but  members  of  the  one  group  cannot  be 
directly  compared  AAuth  the  other  group.  Nos.  HI.  and  IV.  are  practically 
the  same  bread  digested  under  the  same  conditions,  except  that  different 
samples  of  the  same  make  of  pepsin  and  pancreatin  were  used  in  each  case. 
Taldng  the  proteose  and  peptone  together  there  is  not  much  difference  in 
their  activity  ; but  the  No.  II.  samples  possess  greater  peptonising  power 
and  convert  much  more  of  the  proteose  completely  into  peptone.  No.  II. 
samples  also  shoAV  slightly  more  starch-converting  poAver.  In  the  first  table 
on  page  533,  the  digestion  of  the  proteins  only  is  considered,  and  the  results  are 
Avorked  out  in  such  a Avay  as  to  sIioav  AA^hat  becomes  of  100  parts  of  protein 
matter. 

In  examining  these  results,  the  starting  point  must  be  samples  III.  and 
IV.,  since  these  are  the  connecting  links  betAveen  the  tAvo  sets  of  experi* 
ments.  In  No.  III.,  there  is  less  protein  left  absolutely  unacted  on,  but 
the  digestive  process  has  not  been  carried  so  far  as  Avith  No.  IV.  Still 


THE  NUTRITIVE  VALUE  OF  BREAD.  533 

Protein  Digestion  in  Terms  of  IOO  Parts  of  Protein. 


Constituents. 

I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

Digested,  Peptones 

35*46 

44;68 

48-C2 

81-28 

79-31 

80-66 

83-26 

Partly  digested,  Proteoses 

48-79 

36-0*2 

47-28 

9-62 

5-39 

8-44 

5-84 

Dissolved  only.  . 

0-40 

1-20 

1-10 

3-10 

1-20 

1-20 

1-40 

Undissolved 

15-35 

18-10 

2-70 

6-00 

14-10 

9-70 

9-50 

1 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

1 100-00 

there  are  only  2-7  and  6-00  per  cent,  respectively  of  protein  matter  un- 
attacked. Comparing  whole-meal,  No.  I.,  with  best  white  bread,  No.  HI., 
the  quantity  of  assimilated  protein  in  the  latter  is  greater  along  the  whole 
line.  The  peptones  are  much  higher,  the  proteoses  are  about  the  same, 
while  15*35  against  2*70  per  cent,  remains  unacted  on.  The  most  inter- 
esting comparison  in  the  second  series  is  between  No.  IV.  best  bread,  and 
No.  V.  from  all  English  wheat  flour,  prepared  so  as  to  resemble  as  closely 
as  possible  an  old-fashioned  home-made  loaf  from  country  stone-ground 
flour.  Examination  shows  that  in  the  case  of  the  best  white  bread  there 
is  more  of  every  form  of  digestive  protein  than  in  the  case  of  the  darker 
old-fashioned  loaf,  while  14  per  cent,  remains  unacted  on  as  against  6 per 
cent,  in  the  other.  Nos.  II.  and  VI.  are  malt  extract  “ digestive  ''  breads  ; 
so  far  as  proteins  are  concerned,  these  do  not  greatly  differ  from  whole- 
meal. No.  VII.  was  prepared  from  a germ  flour  ; the  digestibility  of  the 
proteins  is  very  nearly  the  same  as  that  of  white  bread.  Taking  the  whole 
series,  the  baker’s  best  white  bread  has  the  highest  degree  of  protein  digesti- 
bility. 

In  the  next  table  are  shown  the  products  of  digestion  of  100  parts  of 
the  bread  as  obtained  from  the  baker.  For  the  nutritive  ratio,  the  peptones, 
proteoses,  and  simply  dissolved  proteins,  are  all  taken  together.  The  carbo- 

Products  of  Digestion  expressed  in  Percentages  of  Bread 

Employed. 


Constituents. 

I. 

II. 

III. 

ly. 

V. 

VI. 

VII. 

Proteins- — - 

(1)  Digested,  Peptones 

2-23 

2-86 

3-45 

5-68 

5-19 

5-10 

8-48 

(2)  Partly  digested,  Pro- 
teoses 

3-06 

2-30 

3-34 

0-67 

0-36 

0-54 

0-60 

(3)  Dissolved  only 

0-03 

0-08 

0-08 

0-22 

0-08 

0-08 

0-15 

(4)  Undissolved 

0-97 

1-16 

0-19 

0-42 

0-92 

0-61 

0-96 

Carbohydrates — 

(5)  Digested,  Maltose,  etc 

32-49 

36-50 

43-49 

46-53 

43-12 

42-41 

37-20 

(6)  Starchy  Matter,  un- 
dissolved . . 

6-65 

9-55 

9-35 

6-84 

5-28 

7-98 

5-43 

(7)  Branny  Matter,  un- 
dissolved . . 

4-66 

2-78 

Nil 

Nil 

0-95 

2-18 

1-78 

Water 

49-91 

44-77 

40-10 

39-64 

44-10 

41-10 

45-40 

100-00 

100-00 

100-00 

dOO-00 

100-00 

100-00 

100-00 

Nutritive  ratio . . 

6-1 

7-0 

6-3 

7-1 

7-6 

7-4 

4-0 

Energy  in  Calories 

158-8 

175-3 

211-5 

223-0 

204-7 

202-1 

195-0 

Calculated  Fat . . 

1-25 

1-10 

0-72 

0-72 

1-10 

1-18 

5-50 

Energy  in  Calories  allow- 
ing for  Calculated  Fat 

170-4 

185-5 

218-2 

229-7 

1 214-9 

213-0 

246*1 

534 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


hydrates  are  taken  as  the  whole  of  the  remaining  digested  matter,  and 
include  the  mineral  salts.  The  fat  is  excluded  altogether  in  the  calculation, 
but  the  quantity  is  very  small  except  in  the  case  of  the  germ  bread,  and 
with  that  there  must  be  a considerable  deficit  of  carbohydrate.  This  is 
provided  for  in  a subsequent  separate  calculation.  The  energy  is  that 
calculated  from  the  dissolved  constituents. 

Correction  for  Fat. — Neither  the  Nutritive  ratio,  nor  the  Energy  in 
Calories  were  included  in  the  original  paper,  but  have  been  added  when 
preparing  the  present  work.  The  fat  was  not  determind  in  any  of  the  breads, 
but  from  the  average  composition  of  the  meals  and  flours  used  can  be  calcu- 
lated with  fair  accuracy.  The  approximate  figure  thus  obtained  is  given 
at  the  foot  of  the  table,  and  then  the  Energy  in  Calories  allowing  for  the 
calculated  fat.  It  is  assumed  that  this  latter  would  be  entirely  absorbed 
in  the  process  of  digestion. 

In  the  foregoing  table  many  of  the  results  are  modified,  because  they 
are  affected  not  only  by  the  degree  of  digestibility,  but  also  by  the  actual 
quantity  of  each  constituent  present.  A point  frequently  overlooked  in 
comparing  the  nutritive  qualities  of  different  t3q)es  of  bread  is  that  of  the 
proportion  of  water  commonly  present.  It  may  be  fairly  assumed  that 
the  baker  will  give  respectively  appropriate  quantities  of  water  to  each 
type  of  meal  or  flour  to  make  it  into  bread,  and  in  the  case  of  the  loaves 
now  under  consideration  the  percentage  varies  from  49*91  with  the  whole- 
meal bread  to  39*64  in  the  white  loaf.  These  figures  are  borne  out  by 
general  experience,  and  hence  when  comparing  the  composition  of  whole-meal 
and  flour  breads  against  each  other,  it  must  be  remembered  that  the  greater 
quantity  of  water  necessary  to  make  the  whole-meal  loaf  will  correspond- 
ingly lower  its  comparative  nutritive  value.  In  examining  the  results,  the 
two  white  bread  samples  must  again  be  taken  as  a starting  point.  Grouping 
the  digested  and  partly  digested  proteins  together,  there  is  6*79  in  the  one 
as  against  6*35  per  cent,  in  the  other,  which  is  no  very  great  difference. 
In  starchy  matter.  No.  IV.  has  a slight  advantage,  46*53  as  against  43*40 
per  cent.  Branny  matter  was  of  course  absent  from  these  samples.  Com- 
paring the  whole-meal  No.  I.  against  No.  III.,  there  is  a total  of  digested 
and  partly  digested  proteins  of  5*29  in  the  former  against  6*79  in  the  latter. 
Digested  starchy  matter  is  also  low,  being  32*22  against  43*40  per  cent. 
As  whole-meal  bread  contains  a low  proportion  of  starch  to  begin  with, 
it  is  only  natural  that  a comparatively  small  amount  should  remain  un- 
digested, viz.,  6*65  as  against  9*55  per  cent.  Counterbalancing  this  there 
is  4*66  per  cent,  of  branny  matter,  against  nil  in  the  white  bread.  This 
residual  branny  matter  gave,  on  analysis,  8*32  per  cent,  of  protein,  being 
roughly  rather  over  one-half  of  that  contained  in  bran  in  its  natural  con- 
dition. Taking  in  the  next  place  No.  IV.,  best  white  bread,  against  the 
special  old-fashioned  loaf.  No.  V.,  there  is  in  No.  IV.  more  of  peptone,  pro- 
teose and  dissolved  protein  than  in  No.  V.,  the  total  being  6*57  against  5*6S 
per  cent,  in  the  latter.  There  is  more  than  double  as  much  undissolved 
]wotein  in  No.  V.,  but  this  alone  does  not  make  up  the  difference.  The 
explanation  is  that  No.  V.  contained  less  protein  to  start  with,  and  of  that 
less  amount  a smaller  proportion  is  digested  under  the  same  conditions. 
No.  V.  also  shows  less  starch  digestion.  Turning  next  to  the  two  malt 
extract  breads,  they  fall  slightly  below  the  best  white  loaves  in  both  protein 
and  starch  digestibility.  Taking  Nos.  II.  and  VI.,  they  differ  principally 
in  that  cream  of  tartar  and  soda  have  been  used  in  the  preparation  of  the 
latter.  So  far  as  an  indirect  comparison  can  be  made  between  them,  there 
does  not  seem  to  be  evidence  that  these  chemicals  have  exercised  a retard- 
ing effect  on  digestion.  On  referring  to  No.  VII.,  it  wiW  be  seen  that  the 


THE  NUTRITIVE  VALUE  OF  BREAD. 


535 


presence  of  germ  has  very  considerably  increased  the  percentage  of  protein 
present,  and  hence  the  amount  of  peptone  yielded  is  represented  by  a very 
high  figure,  8-48  per  cent.  The  digested  starch  is  not  so  high,  but  then 
this  is  a natural  result  of  the  preparation  containing  starch  in  low  propor- 
tion. Under  the  heading  of  branny  matter,  the  figure  U78  is  given  ; but 
this  in  reality  is  not  all  bran,  the  major  portion  consists  of  the  white  intact 
cellulose  skeletons  of  the  germs  themselves.  In  nutritive  ratio  the  whole  of 
the  breads  except  the  germ  show  a deficiency  of  protein.  Comparing|.the 
two  most  important  types,  whole-meal  and  white  bread,  the  whole-meal 
is  6T  as  against  6-3  and  7T  respectively.  The  low  figure  with  the  whole 
meal  is  not  due,  however,  to  excess  of  protein,  but  to  a deficit  of  carbo- 
hydrate. The  two  best  white  breads  show  a greater  amount  of  calorific 
energy  of  the  actually  digested  constituents  than  either  the  old-fashioned 
loaf  (No.  V.)  or  the  whole-meal.  No.  I.  The  last  is  in  fact  the  least  valuable 
in  terms  of  energy  of  the  whole  series.  As  a result  of  its  fat,  the  germ 
bread  heads  the  list  in  point  of  energy.  {National  Association  Review,  1899, 
XVI.  349. 

647.  Studies  in  Digestibility  and  Nutritive  Value  of  Bread  ; Atwater,  Woods, 
and  Snyder. — A most  important,  systematic,  and  exhaustive  study  of  this 
subject  has  been  made  by  the  above  investigators,  under  the  auspices  of 
the  United  States  Department  of  Agriculture.  Supervision  was  exercised 
by  Atwater  and  Woods,  the  actual  experiments  being  made  by  Snyder  at 
the  University  of  Minnesota,  U.S.A.  Snyder's  investigations  extend  over 
the  years  1899-1905,  and  are  described  and  reported  in  Bulletins  Nos.  101, 
126  and  156  of  the  U.S.  Department  of  Agriculture.  Snyder  has  specially 
directed  his  attention  to  the  comparative  values  of  different  kinds  of  flour 
or  meal  from  the  same  wheat,  since  unless  that  precaution  be  taken,  the 
differences  may  be  due  to  the  intrinsic  value  of  the  entire  wheats  rather 
than  the  special  type  of  meal  or  flour  obtained  therefrom.  He  therefore 
regards  it  as  evident  that  a fair  comparison  of  the  nutritive  values  of  the 
different  kinds  of  flour — graham,  entire-wheat,  and  standard  patent — can 
be  made  only  when  the  three  kinds  of  flour  have  been  milled  from  the  same 
lot  of  wheat.  This  was  done  in  the  investigations  here  reported,  a hard, 
Scotch  Fife  spring  wheat  being  used.  The  importance  of  the  subject,  it  is 
believed,  has  justified  this  systematic  inquiry.  It  is  to  be  particularly 
observed  that  the  “ graham  " flour  is  unbolted  wheat  meal,  while  the  so- 
caUed  “ whole-wheat,"  or  entire-wheat  flour,  contains  all  of  the  kernel 
except  a portion  of  the  bran.  The  “ patent  " and  “ clear  grade  " flours 
contain  practically  none  of  the  bran  or  episperm  and  very  little  of  the  germ 
or  embryo  of  the  wheat  kernel. 

From  the  above  wheat  the  following  samples  were  obtained  and  first 
submitted  to  analysis  : — 

No.  1.  First  patent  flour  ; produced  by  the  roller  process  of  milling. 
This  is  the  highest  grade  of  patent  flour  manufactured.  The  gluten  from 
this  flour  has  a greater  power  of  expansion  than  that  from  any  other  grade, 
and  the  flour  also  absorbs  the  most  water  and  produces  the  whitest  and 
largest  sized  loaf  of  bread. 

No.  2.  Second  patent  flour,  sometimes  called  standard  Minneapolis 
patent  flour.  It  is  similar  to  first  patent  flour,  but  the  bread  produced  is 
a shade  darker  in  colour,  and  the  gluten  does  not  possess  quite  so  high  a 
power  of  expansion. 

No.  3.  Standard  patent  flour  is  made  up  of  the  sum  of  the  first  and 
second  patent  grades  and  the  first  clear  or  bakers'  grade  of  flour,  and  is 
the  ordinary  bread  flour  most  frequently  found  on  the  market.  It  is  used 
in  this  investigation  as  the  standard  for  comparison  with  the  entire-wheat 


536 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  graham  flours.  About  72*6  per  cent,  of  the  screened  wheat  is  recovered 
as  standard  patent  flour.  [It  will  be  noticed  that  the  “ standard  patent 
flour  ” is  practically  a straight  grade  flour,  i.e.,  the  whole  of  the  flour  of  the 
wheat.] 

No.  4.  First  clear  grade  flour.  After  the  first  and  second  grades  of 
patent  flour  are  removed,  about  II -8  to  12  per  cent,  of  the  first  clear  grade 
flour  is  obtained,  which  contains  slightly  more  protein  than  either  the  first 
or  second  patent  flour.  The  protein,  however,  does  not  contain  gliadin 
and  glutenin  in  the  right  proportions  to  produce  so  good  a quality  of  bread 
as  the  patent  grade  flours. 

No.  5.  Second  clear  or  low  grade  flour.  After  the  standard  patent 
flour  has  been  removed  there  is  obtained  about  0-5  per  cent,  of  flour  called 
second  clear  or  low  grade,  which  contains  a high  percentage  of  protein. 
The  gluten,  however,  is  of  poor  quality  for  bread-making  purposes. 

No.  6.  “ Red  dog ''  flour.  This  is  the  lowest  grade  of  flour  produced. 
It  is  dark  in  colour  and  has  but  little  power  of  expansion.  It  is  secured 
largely  from  the  germ  or  embryo  and  adjacent  portions  of  the  wheat,  and 
coiRains  a relatively  high  percentage  of  protein.  “ Red  dog  ''  flour  pro- 
duces a small  and  dark-coloured  loaf  of  bread  as  compared  with  flour  of 
better  quality. 

No.  7.  Middlings  or  shorts.  About  11-6  per  cent,  of  the  cleaned  wheat 
is  recovered  in  middhngs,  which  consists  of  the  fine  bran  that  has  been 
more  completely  pulverised.  When  this  product  contains  a large  part  of 
the  germ  it  is  much  richer  in  protein  than  ordinary  shorts  and  is  called  shorts 
middlings.  The  term  middlings,  as  used  in  this  sense,  should  not  be  con- 
fused with  the  same  term  applied  to  the  material  obtained  when  wheat  is 
milled  by  the  old  process.  The  middlings  of  the  old  process  are  now  reduced 
and  recovered  in  the  various  grades  of  patent  flours. 

No.  8.  Bran.  This  is  the  episperm  or  outer  covering  of  the  wheat  kernel. 

No!  9.  Entire-wheat  flour.  This  is  the  product  obtained  by  removing 
a portion* of  the  bran  and  then  grinding  the  remainder  of  the  wheat  kernel. 
The  flour  is  of  a coarser  texture  than  the  patent  and  clear  grades.  Entire- 
wheat  flour  is  sometimes  called  “ purified  graham  or  ‘‘  natural  " flour. 

No.  10.  Graham  flour.  This  is  the  entire-wheat  kernel  (bran  and  all) 
ground  into  meal.  The  presence  of  the  bran  prevents  the  fine  grinding  of 
the  material,  and  particles  of  the  bran  are  apparent  when  the  flour  is  ex- 
amined. Graham  flour  is  practically  wheat  meal.  No  sieves  or  bolting 
cloths  are  employed  in  its  manufacture,  and  many  coarse  particles  of  un- 
pulverised material  are  present  in  the  product. 

No.  11.  Cleaned  wheat,  scoured  and  polished  for  milling.  This  is  a 
hard  Scotch  Fife  spring  wheat,  plump,  and  of  good  quality,  weighing  60  lbs. 
per  bushel.  The  sample  analysed  was  ground  in  the  laboratory  in 
a Maercker  mill.  All  of  the  grades  of  flour  and  the  various  products 
given  in  the  list  of  samples  were  obtained  from  this  wheat. 

^ No.  12.  Gluten  flour.  This  is  a flour  containing  as  high  a percentage 
of  protein  as  it  is  possible  to  secure  by  the  ordinary  roller-process  milling. 
It  is  not  composed  entirely  of  gluten,  but  simply  contains  a high  percentage 
of  this  material.  No  flour  can  be  composed  entirely  of  gluten. 

The  table  on  page  537  gives  the  results  of  analysis  of  the  foregoing  pro- 

^^^The  heat  of  combustion  or  energy  was  determined  in  a bomb  calori- 
meter, as  described  in  Chapter  XXVii  of  this  work.  When  calculated  from 
tlie  constituents  the  following  factors  were  employed 

Protein.  . • • • • • . . 5-9  Calories  per  gram. 

Fat  . . . . • • • • . . 9-3  „ ,,  „ 

Carbohydrates  . . • • . . 4*2  „ „ „ 


THE  NUTRITIVE  VALUE  OE  BREAD. 


537 


Composition,  Acidity,  and  Heats,  of  Combustion  of  Flours  and 
OTHER  Milling  Products  of  Wheat. 


1 

Sam- 

Carbo- 

Phos-  i 

Acidity 

calcu- 

Heat of  Combus- 
tion per  gram. 

i pie 

1 No. 

Milling  Product. 

Water. 

Protein 
(NX  5-7). 

Fat. 

liy- 

drates. 

Ash. 

phoric 

Acid. 

lated  as 
Lactic 
Acid. 

1 

Calcu-  1 
lated.  j 

Deter- 

mined. 

P.  ct. 

P.  ct. 

P.  ct. 

P.  ct. 

P.  ct. 

P.  ct. 

P.  ct. 

Calories.’ 

Calories. 

I 1 

First  Patent  Flour . . 

10-5.5 

11-08 

1-15 

76-85 

0-37 

0-15 

0-08 

3-989  ! 

4-032 

Second  Patent  Flour 

10-49 

11-14 

1-20 

76-75 

0 42 

017 

0 08 

i 3-992 

4-006 

I ' 

Straight  or  Standard 
Patent  Flour 

10-54 

11-99 

1-61 

75-36 

0-50 

0 20 

0-09 

4-022 

4-050 

i 4 

1 

First  Clear  Grade 
Flour 

10-13 

13-74 

2-20 

73-13 

0'80 

0-34 

0-12 

4-087 

4-097  1 

5 

Second  Clear  Grade 
Flour 

10-08 

15-03 

3-77 

69-37 

1-75 

0-56 

0-27 

4-153 

1 

4-267 

: 6 

“ Red  Dog  ” Flour 

9-17 

18-93 

7-00 

61-37 

3-48 

— 

0-59 

4-349 

4-485 

7 

Shorts 

8-73 

14-87 

6-37 

65-47 

4-56 

— 

014 

4-219 

4-414 

8 

Bran 

9-99 

14-02 

4-39 

65-54 

6-06 

2-20 

0-23 

3-988 

4-198 

9 

Entire- wheat  Flour 

10-81 

12-26 

2-24 

73-67 

1-02 

0-54 

0-32 

4-026 

4-032 

10 

Graham  Flour 

8-61 

12-65 

2-44 

74-58 

1-72 

0-71 

0-18 

4-123 

4-148 

11 

Wheat  ground  in 
Laboratory- 

8-50 

1 

12-65  : 

2-36 

74-69 

1-80 

0-75 

018 

4-114 

4-140 

12 

Gluten  Flour 

8-57 

16-36 

3-15 

70-63 

1-29 

0 14 

— 

— 

Digestion  Experiments. — The  most  important  part  of  Snyder’s  researches 
consisted  of  the  elaborate  digestion  experiments  made.  The  subjects  were 
young  men  in  good  health,  designated  in  these  experiments  as  Nos.  1,  2,  3, 
and  4.  In  so  far  as  possible  the  experiments  were  alike,  except  as  regards 
the  kind  of  flour  from  which  the  bread  eaten  was  made.  All  the  food  con- 
sumed and  faeces  excreted  were  weighed  and  samples  were  analysed  The 
separation  of  the  faeces  for  the  experimental  period  was  made  by  the  use 
of  charcoal,  which  was  given  to  the  subjects  in  capsules  with  the  last  meal 
before  and  the  first  meal  after  each  period.  The  digestibility  of  the  bread 
and  milk  diet  as  a whole  was  measured  by  the  difference  between  the  total 
nutrients  in  the  diet  and  those  in  the  faeces.  Then,  by  assuming  certain 
factors  for  the  digestibility  of  the  nutrients  in  the  milk,  the  digestibility  of 
those  in  the  bread  alone  was  estimated. 

The  following  is  a detailed  record  of  one  of  these  experiments  : — 

“DIGESTION  EXPERIMENT  No.  162. 

Kind  of  food. — Bread,  made  from  standard  patent  flour,  and  milk. 

Subject. — Student  No.  2 ; 24  years  of  age,  with  average  amount  of 
exercise. 

Weight. — At  the  beginning  of  the  experiment,  140  lbs  ; at  the  close, 
139  lbs. 

Duration. — Two  days,  with  six  meals,  beginning  with  breakfast,  April  5, 
1899. 

During  this  experiment,  the  details  of  which  are  given  in  the  flrst 
table  on  page  538,  the  subject  eliminated  1,390*3  grams  urine,  containing 
1*82  per  cent.,  or  25*3  grams,  nitrogen.  The  average  nitrogen  balance 
per  day  was  therefore  as  follows  : Income  in  food,  10*8  grams  ; outgo  in 
urine,  12*7  grams,  and  in  faeces,  0*9  gram  ; implying  a loss  of  2*8  grams 
nitrogen,  corresponding  to  17*5  grams  protein.  The  total  heat  of  com- 
bustion of  the  urine  as  determined  was  168  Calories.” 

Fiom  the  results  of  twelve  such  experiments  the  second  table  on  page 
538  was  computed,  the  nutritive  value  of  the  milk  being  calculated  and 
allowed  for. 


538 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Results  of  Digestion  Experiment  No.  162. 


Sam 

pie 

No. 

Weight 
of  Ma- 
terial. 

Protein 
(NX  6-25). 

Fat. 

Carbohy- 

drates. 

Ash. 

i 

Heat  of 
Combus- 
tion. 

Grams. 

1 Grams. 

Grams. 

Grams. 

Grams. 

Calories. 

Food  consumed — 

53 

Bread 

876-0 

67-9 

7-8 

410-9 

2-8 

2,146 

54 

Milk 

2,100-0 

66-2 

97-2 

105-0 

14-7 

1,664 

Total 

— 

134-1 

105-0 

515-9 

17-5 

3,810 

56 

Faeces  (water-free) 
Estimated  Faeces  from 

40-3  i 

11-3 

8-6 

10-6 

9-7 

208  1 

Food  other  than  Bread 

— 

2-0 

4-9 

2-1 

— 

72 

Estimated  Faeces  from 

i 

Bread  . . 

— 

9-3 

3-7 

8-5 

— 

136  ! 

Total  amount  digested.  . 
Estimated  Digestible  Nu- 

— 

122-8 

96-4 

505-3 

7-8  . 

3,602 

I 

trients  in  Bread 

— 

58-6 

4-1 

402-4 

— 

2,010 

1 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

Co-efficients  of  digestibility 
of  total  Food . . 
Estimated  Co-efficients  of 

— 

91-6 

91-8 

1 97-9 

44-6 

94-5 

digestibility  of  Bread 
Proportion  of  Energy  ac- 

— 

86-3 

52-6 

97-9 

93-7 

tually  available  to  body 

90-5 

In  total  Food 

— ■ 

— 

— 

— 

! — 

In  Bread  alone 

“ 

90-8 

Digestibility  of  Nutrients  and  Availability  of  Energy  of 

Bread  alone. 


Experi- 
ment 
j No. 

Subject.! 

No. 

Kind  of  Food. 

Protein. 

Fat. 

Carbo- 

hydrates. 

Energy. 

1 

Per  cent. 

Per  cent. 

Per  cent. 

Per  cent. 

161 

1 

Mffiite  Bread  (standard  patent) 

86-7 

65-2 

97-4 

90-0 

162 

2 

86-3 

52-6 

97-9 

90-8 

163 

3 

i ..  ,, 

1 ” 

82-8 

51.3 

97T 

89-5 

j 

Average  of  3 

85-3 

56-4 

97-5 

90-1 

1 

165 

1 

Entire-wlieat  Bread  . . 

78-1 

55-6 

93-5 

84  4 

166 

2 

! 

83-9 

48-1 

94-6 

86-1 

1 167 

3 

79-1 

63-6 

94-1 

86-1 

i 

Average  of  3 

80-4 

55-8 

94-1  j 

85-5 

170 

1 

Graham  Bread 

81-0 

67-8 

88-1 

81-8 

171 

2 ! 

80-6 

55-1 

88-7 

81-6 

172 

3 i 

71-1 

51-2 

88-5 

78-6 

Average  of  3 

77-6 

58-0 

88-4  i 

1 

80-7 

164 

4 i 

White  Bread  (first  patent)  . . 

90-5 

— 

98-0 

92-8 

168 

4 

,,  ,,  (second  patent) 

91-4 

— 

98-7  1 

93-5 

’ 169 

4 

,,  ,,  (standard  patent) 

90-3 

— 

97-4 

92.2 

1 

Average  of  3 . . . . 

90-7 

— 

98-0 

1 92-8 

THE  NUTRITIVE  VALUE  OF  BREAD. 


539 


Assuming  that  the  averages  for  bread  of  different  kinds  given  in  tlie 
above  table  represent  also  the  coefficients  of  digestibility  of  the  nutrients 
in  the  different  flours,  the  proportions  of  digestible  nutrients  in  the  flours  may 
be  calculated  from  their  composition  as  given  in  the  table  on  page  537 . Thus 
standard  patent  flour  contains  11 -99  per  cent,  protein,  85-3  percent,  of  which 
is  digestible  ; the  proportion  of  digestible  protein  in  standard  patent  flour 
would  then  be  (11-99  per  cent,  x 85-3  =)  10-2  per  cent.  In  like  manner 
the  digestible  carbohydrates  and  available  energy  may  be  calculated.  Such 
calculations  have  been  made  for  standard  patent  flour,  entire-wheat  flour, 
and  graham  flour  on  the  basis  of  the  composition  of  the  flour  as  milled. 
The  following  table  shows  the  results,  as  well  as  the  total  protein  and  carbo- 
hydrates, in  comparison  with  the  proportions  of  the  nutrients  and  energy 
in  the  different  flours. 


Proportions  of  Total  and  Digestible  Nutrients  and  Available 
Energy  in  Different  Grades  of  Flour  as  Milled. 


Flour. 

Protein. 

Carbohydrates. 

Heat  of  Com- 
bustion per 
gram. 

X X 5-70. 

X X 6-25  j 

XX5-70. 

X'x6-25. 

Total. 

Diges- 

tible. 

Total.  1 

1 

Diges- 

tible. 

Total. 

Diges- 

tible. 

Total 

tible. 

Total. 

Avail- 

able. 

‘ Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

' 1 

Per  ct.  Per  ct. 

Calories. 

Calories. 

j Standard  Patent  . . 

j 11-99 

10-2 

13-14 

11-2 

75-36 

73-5 

74-21  72-3 

4-050 

3-650 

1 Entire  Wheat 

i 12-26 

9-9 

13-44 

10-8 

73-67 

69-3 

72-49i  68-2 

4-030 

3-445 

j Graham 

12-65 

9-8 

13-86 

10-7 

74-99 

66-3 

: 73-78|  65-2 

4-150 

3-350 

From  this  table  it  will  be  observed  that  according  to  composition,  the 
graham  flour  contained  the  largest  proportion  of  protein  and  the  largest 
amount  of  energy,  while  the  standard  patent  flour  contained  the  smallest 
proportion  of  protein,  but  a little  more  energy  than  the  entire  wlieat  flour. 
According  to  the  results  of  the  digestion  experiments,  however,  the  propor- 
tions of  digestible  protein  and  the  amount  of  energy  actually  available  to 
the  body  were  greater  in  the  standard  patent  flour  than  in  the  entire-wheat 
or  the  graham  flour.  The  latter  contained  the  least  digestible  protein  and 
available  energy.  A microscopic  examination  of  the  faeces  showed  that 
those  derived  ffom  standard  patent  flour  contained  very  small  particles  of 
disintegrated  starch.  The  faeces  from  graham  and  entire-wheat  breads 
contained  masses  of  material  containing  wheat  starch  grains  in  practically 
the  same  form  as  in  the  original  graham  and  entire-wheat  flour  breads. 

Artificial  digestion  experiments  were  also  made,  but  as  these  agree  with 
the  results  of  previous  investigations  already  described,  their  inclusion 
here  is  scarcely  necessary. 

An  extended  series  of  digestion  experiments  was  made  in  order  to 
determine  the  degree  of  digestibility  when  a limited  instead  of  a full  ration 
of  bread  was  given.  The  results  indicate  that  when  food  is  taken  in  small 
amounts  it  is  more  thoroughly  digested  than  when  taken  in  large  amounts, 
and  that  it  is  possible  for  the  digestive  tract  to  be  supplied  with  such  a 
quantity  of  food  that  the  highest  degree  of  digestibility  is  not  secured. 

On  mixing  starch  with  flour,  the  digestibility  of  the  proteins  is  found 
to  be  modified.  A fairly  strong  flour  was  taken  and  diluted  by  the  addition 
of  20  per  cent,  of  starch  (80  -f  20  = 100).  In  this  manner  the  equivalents 
of  flours  with  a high  and  a low  protein  content  were  obtained.  Digestion 
experiments  were  carried  out  with  breads  made  from  the  two.  The  follow- 
ing table  gives  the  digestibility  of  nutrients  and  availability  of  energy  of 
the  ordinary,  compared  with  the  starched  bread,  in  percentages  : — 


540 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


Protein.  Carbohydrates.  Energy. 

Ordinary  bread,  average  of  three  ex- 
periments ..  ..  ..  ..87-3  97-6  91-9 

Starched  bread,  ditto..  ..  ..  84*1  97-9  93-0 

The  two  series  of  experiments  indicate  that  a proportionally  small 
amount  of  protein  is  less  thoroughly  digested  than  a proportionally  large 
amount. 

In  continuation  of  these  investigations  a similar  series  of  digestion 
experiments  was  made  with  a hard  spring  wheat,  characterised  by  a very 
high  protein  content,  namely  15*5  per  cent.  The  experiments  lasted  over 
four  days  instead  of  two,  with  similar  results  to  those  already  recorded. 

In  the  next  place  experiments  were  made  with  the  following  soft  winter 
wheats,  and  flours  therefrom,  of  which  analyses  are  given  below  : — 

No.  218.  Cleaned  soft  winter  wheat,  from  Goshen,  Ind.,  prepared  for 
milling,  of  good  quality,  and  weighing  60  lbs.  per  bushel.  The  sample 
analysed  was  ground  in  the  laboratory  in  a Maercker  mill. 

No.  221.  Mixed  grade  flour,  ground  from  soft  winter  wheat.  No.  218, 
and  consisting  largely  of  straight  flour  with  some  lower  grades  and  a little 
germ.  This  sample  was  not  strictly  a straight  grade  flour,  but  more  properly 
a blend. 

No.  222.  Entire-wheat  flour,  ground  from  soft  winter  wheat  No.  218, 
after  removing  a small  amount  of  bran.  This  sample  was  different  from  the 
entire  wheat  used  in  former  work  with  hard  wheat  ; it  had  more  of  the 
characteristics  of  graham.  It  was,  however,  more  finely  pulverised  than 
the  graham  flours  used  in  the  previously  described  experiments. 

No.  268.  Bran,  from  soft  winter  wheat  No.  218. 

No.  237.  Soft  winter  wheat,  of  good  quality,  from  North  Lansing,  Mich., 
weighing  59  lbs.  per  bushel,  cleaned  and  prepared  for  milling. 

No.  240.  Straight  grade  or  standard  patent  flour,  milled  from  soft  wheat 
No.  237.  It  should  be  classed  as  a high  grade  rather  than  as  a straight - 
grade  flour.  It  possessed  good  bread-making  qualities,  but  required  more 
thorough  mixing  and  kneading  than  hard- wheat  flours. 

No.  239.  Bran,  from  soft  winter  wheat  No.  237,  obtained  in  milling 
flour  No.  240. 

Composition  of  Wheats,  Flours,  and  Offals,  and  of  Bread  used 
IN  Digestion  Experiments  with  Soft  Wheat  Breads. 


Sample 

No. 

Whence  obtained. 

Water. 

Protein 
NX  5-7 

Fat. 

Carbo- 

hydrates. 

Ash. 

Heat  of 
Combus- 
tion per 
gram, 
deter- 
mined. 

1 Soft  Wheat — 

Per  cent. 

Per  cent. 

Per  cent. 

Per  eent. 

Per  cent. 

Calories. 

218 

i Wheat  from  Indiana  . . 

8-09 

13-10 

1-52 

75-38 

1-85 

4-090 

219 

Entire-wheat  Flour 

9-00 

12-80 

1-54 

74-40 

1-00 

4-020 

221 

Mixed  Grade  Flour 

10-30 

12-30 

0-93 

75-94 

0-53 

4-010 

237 

Wheat  from  Michigan 

10-25 

12-34 

1-35 

74-23 

1-83 

4-000 

239 

Bran 

8-74 

14-90 

4-41 

05-78 

0-11 

4-108 

240 

Straight  Patent  Flour . . 

10-97 

10-92 

0-50 

77-15 

0-40 

3-799 

241 

! Entire-wheat  Flour 

11-01 

12-01 

1-53 

74-17 

1-28 

3-800 

242 

Graham  Flour  . . 

11-23 

12-24 

1-41 

73-27 

1-85 

3-900 

208 

Bran 

Bread  made  from — 

10-94 

10-72 

4-42 

01-20 

0-72 

— 

223 

1 Mixed  Grade  Flour.  . 

39-50 

8-01 

0-00 

51-32 

0-51 

2-710 

231 

Entire-wheat  Floux . . 

39-50 

8-53 

1-02 

49-49 

1-40 

2-040 

244 

1 Straight  Patent  Flour 

30-87 

7-59 

0-38 

54-07 

0-49 

2-010 

251 

' Entire- wheat  Flour.  . 

37-02 

8-33 

1-08 

51-70 

1-27 

2-090 

200 

1 Graham  Hour 

38-12 

, 8-30 

0-87 

51-20 

1-45 

1 

i 2-020 

1 

THE  NUTRITIVE  VALUE  OE  BREAD. 


541 


No.  241.  Entire-wheat  flour,  prepared  from  soft  winter  wheat  No.  237. 

No.  242.  Graham  flour,  obtained  from  soft  winter  wheat  No.  237. 

No.  223.  Mixed-grade  flour  bread.  This  was  made  of  the  flour  from 
which  sample  No.  221  was  taken. 

No.  231.  Entire-wheat  flour  bread.  This  was  made  of  the  flour  from 
which  sample  No.  219  was  taken. 

No.  244.  Straight  patent  flour  bread.  In  making  this  bread  flour  was 
used  from  which  sample  No.  240  was  taken. 

No.  251.  Entire-wheat  flour  bread.  This  bread  was  made  of  the  flour 
from  which  sample  No.  241  was  taken. 

No.  260.  Graham-flour  bread.  The  graham  flour  used  was  the  lot  from 
which  sample  No.  242  was  taken. 

The  results  of  the  digestion  experiments  are  given  in  the  following  table  : — 

Summary  of  Digestion  Experiments  with  Soft  Winter  Wheat  ; 

Digestibility  of  Nutrients  and  Availibility  of  Energy  of  Bread 

ALONE. 


Experi- 

ment 

Xo 

Subject 

No. 

Kind  of  Food. 

Protein. 

Carbo- 
liydrates.  * 

Energy. 

Experiments  with  Indiana  Wheat. 

Per  cent. 

Per  cent.  { 

Per  cent. 

309 

1 

White  Bread  (mixed  grade  flour) 

94-2 

95-6  ! 

90-4 

310 

2 

,,  ,,  ,,  ,, 

89-4 

90-0  1 

90-4 

311  1 

3 

83-0 

95-8  ' 

90-4 

Average  of  3 

88-9 

90-0 

90-4 

312  ! 

1 

Entire-wheat  Bread 

89-5 

90-3 

85-2 

313  i 

2 

84-9 

89-8 

84-5 

314  i 

3 

79-3 

88-8 

82-9 

A\"erage  of  3 

84-6 

89-6 

84-2 

Experiments  with  Michigan  Wheat. 

315 

1 

White  Bread  (standard  patent) 

930 

97-6 

93-4 

310 

2 

94-4 

98-3 

951 

317 

3 

90-9 

98-2 

941 

Average  of  3 

92-8 

98-0 

1 94-2 

318 

1 

Entire- wheat  Bread 

80-8 

92-2 

87-9 

319 

2 

'9  99 

82-8 

93-2 

86.8 

.320 

3 

„ 

87-4 

93-4 

89-4 

I 

i Average  of  3 

85-7 

92-9 

! 88-0 

321 

! 1 

Graham  Bread  . . 

79-2 

88-9 

82-7 

322 

2 

,,  . 

80-1 

89-5 

81-7 

323 

' 3 

„ 1 79-0 

89-6 

83-5 

Average  of  3 

79-4 

89-3 

I 82-6 

These  results  are  summarised  in  the  following  table  : — 


No. 

of 

Sample. 

Grade  of  Flour. 

Protein. 

Carbohydrates.  | 

Heat  of  Combustion 
per  Gram. 

Total. 

Digest- 

ible. 

Total. 

Digest- 

ible. 

Total. 

Avail- 

able. 

221 

Mixed-grade  Flour 

Per  cent. 

12-30 

Per  cent. 
10-93 

Per  cent. 

75-94 

Per  cent. 

72-90 

i 

Calories. 

4-010 

Calories. 

3-645 

219 

Entire-wheat  Flour 

12-80 

10-82 

74-40 

66-66 

4-020 

3-384 

240 

Straight  White  Flour  . . 

10-92 

10-13 

77-15 

75-61 

3-799 

3-579 

241 

Entire- wheat  Flour 

12-01 

10-29 

74-17 

68-80 

3-860 

3-399 

242 

1 Graham  Flour  . . . . 

12-24 

9-72 

73-27 

65-43 

3-906 

3-226 

542 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


With  soft  winter  wheat  flours,  the  results  obtained  are  in  entire  accord- 
ance with  those  in  tests  wdth  bread  made  from  different  grades  of  hard 
wheat  flours. 

The  experiments  were  continued  with  Oregon  soft  wdnter  and  Oklahoma 
hard  wdnter  wheats,  of  which  the  following  are  particulars  : — 

No.  269.  Oregon  white  winter  wheat  weighing  69  lbs.  per  bushel, 
grow'n  at  the  Oregon  Experiment  Station,  Corvallis,  Oreg. 

No.  271.  Graham  flour  prepared  from  Oregon  wheat.  No.  269. 

No.  272.  Entire-wheat  flour  from  Oregon  wheat.  No.  269. 

No.  273.  Straight-grade  flour  from  Oregon  wheat.  No.  269.  About  70 
per  cent,  of  the  Avheat  was  recovered  as  straight -grade  flour. 

No.  270.  Hard  wdntei?  Weissenburg  wheat  weighing  62  lbs.  per  bushel, 
grown  at  the  Oklahoma  Ex:periment  Station,  Stillwater,  Okla. 

No.  274.  Graham  flour  from  Oklahoma  wheat.  No.  270. 

No.  275.  Entire-wheat  flour  from  Oklahoma  wdieat.  No.  270.  86  per 

cent,  of  the  wdieat  was  recovered  as  entire- wheat  flour. 

No.  276.  Straight-grade  flour  from  Oklahoma  wheat.  No.  270.  About 
70  per  cent,  of  straight -grade  flour  was  recovered. 

No.  413.  Bran  from  Oklahoma  wLeat,  No.  270. 

No.  414.  Germ  from  Oklahoma  wheat.  No.  270. 

No.  415.  Bran  flour.  The  sample  was  prepared  by  adding  14  per  cent, 
of  finely  ground  bran  (No.  413)  to  the  straight-grade  Oklahoma  flour  (No.  276). 

No.  416.  Germ  flour.  The  sample  was  prepared  by  mixing  93  per  cent, 
of  straight-grade  Oklahoma  flour  (No.  276)  with  7 per  cent,  of  finely  ground 
germ  (No.  414). 

Particulars  of  these  are  given  in  the  following  table 


Composition  and  Heat  of  Combustion  of  Wheats  and  Flours. 


1 

Sam- 

ple 

No. 

Kind  of  Material. 

Water. 

Protein. 

Fat. 

Carboliydrates 
when  Protein  is 
estimated  a'. — 

Ash. 

Heat  of  Combus- 
tion per  gram. 

(NX6-25).  (Nx5-7).| 

N X 6-25 

N X 5-7 

Calcu-  1 
lated.  I 

Deter- 

mined. 

269 

Oregon  Wheat  . . 

Per  ct. 
8-99 

Per  ct. 
9-12 

Per  ct. 
8-32 

Per  ct. 
1-83 

Per  ct. 
78-30 

Per  ct. 
79-10 

Per  ct. 
1-76 

Calories. 
3-997  1 

Calories. 

4-008 

271  1 

Graham  Flour  from 
No.  269.. 

8-15 

8-97  ' 

8-18 

1-68 

79-43 

80-27 

1-72 

1 

4-023  1 

3-990 

272 

Entire-wheat  Flour 
from  No.  269  . . 

8-66 

8-25  1 

7-52 

1-67 

80-35 

81-03 

1 1-07 

4-016  ' 

3-900 

273 

Straight-grade  Flour 
from  No.  269  . . 

8-94 

7-55 

6-90 

1-25 

I 

81-82  1 

82-47 

0-44 

3-993 

3-880  i 

270 

Oklahoma  Wheat 

8-65 

16-82 

15-33 

1-83 

71-33 

72-87 

1-32 

4-160 

4-110  ; 

274 

Graham  Flour  from 
No.  270.. 

7-73 

16-81 

15-33 

1-79 

72-35 

73-83 

1-32 

4-193 

4-178  1 

275 

Entire-wheat  Flour 
from  No.  270  . . 

7-46 

16-63 

15-16 

1-64 

73-05 

74-52 

1-22 

4-201 

1 

4-159 

276 

Straight-gradeFlour 
from  No.  270  . . 

9-93 

15-06 

13-74 

' 0-92 

73-57 

74-89 

0-52 

4-065 

4-040 

413 

Bran 

9-91 

16-39 

14-93 

’ 4-50 

62-79 

64-25 

6-41 

4-022 

4-103 

414 

Germ 

8-73 

29-88 

1 27-24 

11-23 

45-45 

48-09 

4-71 

4-716 

4-597 

415 

Bran  Flour 

9-69 

15-35 

13-96 

1-48 

72-23 

73-82 

1-25 

4-077 

3-876  , 

416 

Germ  Flour 

9-63 

16-30 

14-87 

1-66 

71-54 

^ 72-97 

0-87 

4-124 

3-962  , 

The  jireceding  table  illustrates  the  fact  that  different  wheats  and  different 
types  of  flour  vary  wddely  in  composition.  Thus,  straight-grade  flour  (No.  276) 
prepared  from  Oklahoma  wheat  contained  a much  larger  amount  of  protein 
than  graham  flour  (No.  271)  prepared  from  Oregon  wdieat.  This  empha- 
sises the  importance,  previously  pointed  out,  of  prepaiing  the  different 
kinds  of  flour  for  investigations  of  this  nature  from  the  same  lot  of  wheat. 
Otlierwise,  if  a straight-grade  flour  milled  from  one  lot  of  wheat  w'ere  com- 
pared wdth  an  entire-wheat  flour  milled  from  another  and  entirely  different 
lot  of  wheat,  the  straight-grade  flour  might  contain  either  more  or  less  starch 
or  protein  than  the  graham  flour,  according  to  the  character  of  the  wheats 
from  which  they  were  prepared. 


THE  NUTRITIVE  VALUE  OF  BREAD.  543 

The  breads  prepared  from  the  above  flours  had  the  following  com- 
position : — 


Composition  of  Bread  used  in  Digestion  Experiments  with 
Oregon  and  Oklahoma  Wheat  Breads. 


;Sam- 

ple 

No. 

Kind  of  Material. 

Water. 

Protein 
(NX  6-25) 

Fat. 

Carbo- 

hy- 

drates. 

Ash. 

Heat  of 
Combus- 
tion per 

gram. 

Per  cent. 

Per  cent. 

Per  cent.' 

Per  cent. 

Per  cent. 

Calories. 

Bread  made  from  : 

1 

277 

Oregon  Entire-wheat  Flour  . . 

39-95 

5-70 

1-09 

52-39 

0-87 

2-566 

294 

Oregon  Straight-grade  Flour  . . 

34-95 

5-41 

0-89 

57-85 

0-90 

2-765 

311 

Oregon  Graham  Flour . . 

38-55 

6-11 

1-12 

52-68 

1-54 

2-562 

328 

Oklahoma  Straight-grade  Flour 

37-65 

10-13 

0-64 

51-14 

0-44 

2-783 

345 

Oklahoma  Entire-wheat  Flour 

41-31 

10-60 

1-04 

46-11 

0-94 

2-714 

362 

Oklahoma  Graham  Flour 

42-20 

10-65 

1-12 

44-58 

1-45 

2-516 

379 

Straight-grade  Flour  with  149^ 

Bran  . . 

43-20 

9-50 

0-84 

45-55 

0-91 

2-499 

396 

Straight-grade  Flour  with  7"b 

1 

Germ 

38-00  1 

11-07 

1-13 

49-12 

0-68 

2-793 

Digestibility  of  Nutrients  and  Availibiltty  of  Energy  of 

Bread  alone. 


Experi- 

ment 

No. 

Subject 

No. 

Kind  of  Food. 

Protein. 

i 

Carbohy- 

drates. 

! 

! Energy. 

Per  cent. 

Per  cent. 

Per  cent. 

Experiments  with  Oregon  Wheat. 

469 

'l 

Entire- wheat  Flour  Bread 

66-9 

93-8 

87-0 

470 

2 

95  99  99  • • . 

77-5 

94-6 

89-5 

471 

3 

68-9 

93-8 

86-7 

1 

Average  . . . . . . 

71-1 

94-1 

87-7 

472 

1 

Straight-grade  Flour  Bread 

85-6 

98-0 

94-8  1 

473  j 

2 

89-4 

98-9 

96-3  ! 

474  : 

3 

79-8 

97-8 

91-0 

Average 

84-9 

93-2 

95-0  i 

475 

1 

1 

Graham  Flour  Bread 

60-6 

90-1 

80-7  i 

476 

2 

65-3 

90-9 

83-5 

477 

3 

a 40-5 

92-6 

82-6  1 

Average 

63-0 

91-2 

82-3 

1 Experiments  with  Oklahoma  Wheat. 

481 

1 

Entire-wheat  Flour  Bread 

75-7 

89-6 

81-9 

482 

2 

,, 

84-4 

92-0 

86-5 

483 

3 

78-7 

90-0 

82-9 

Average 

79-6 

90-5 

83-8 

478 

1 

Straight-grade  Flour  Bread 

90-2 

96-7 

90-7  I 

479 

2 

99  99  99 

91-9 

98-2 

93-3 

480 

3 

90-6 

98-1 

92-2 

Average 

90-9 

97-7 

92-1 

484 

1 

Graham  Flour  Bread 

74-1 

85-6 

76-1 

485 

2 

99  99  99 

82-2 

89-1 

86-1 

486 

3 

- 

75-6 

87-4 

79-6 

Average  . . . . . . 

77-3 

87-4 

80-(> 

a Omitted  from  average. 


544 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  second  table  on  page  543  is  a summary  of  the  results  of  the  diges- 
tion experiments.  Examination  of  this  shows  that  different  subjects  possess- 
different  digestive  powers  for  the  protein  of  graham  bread.  The  figure 
with  subject  No.  3 is  regarded  as  abnormally  low  and  therefore  is  not  in- 
cluded in  the  average.  But  notwithstanding  the  wide  range  in  the  digesti- 
bility of  protein  of  the  same  flour  by  the  different  subjects,  the  results  are 
in  perfect  accord  in  this  respect,  that  each  subject  digested  the  nutrients  of 
the  straight-grade  flour  more  thoroughly  than  those  of  the  entire-wheat, 
and  the  nutrients  of  the  latter  more  thoroughly  than  those  of  the  graham 
flour.  Likewise  the  energy  of  the  straight-grade  flour  was  more  available- 
than  that  of  entire-wheat  or  graham. 

The  following  table  summarises  the  relative  digestibility  of  the  different- 
grades  of  flour  : — 

Proportion  of  Total  and  Digestible  Nutrients  and  Total  and- 
Available  Energy  in  Different  Grades  of  Oregon  and  Oklahoma 
Flour  as  Milled. 


Sample  j 

1 

Kind  of  Flour. 

Protein  (N  x 6-25). 

Carbohydrates. 

Energy  per  gram.. 

Xo.  ' 

Total.  ' 

Digest- 

ible. 

Total. 

Digest- 

ible. 

Total  1 Avail- 
able. 

271 

Oregon  Graham  Flour  . . 

Per  ct. 

8-97  ! 

Per  ct. 
5-65 

Per  ct. 
79-48 

Per  ct. 

72-49 

Calories . Calories. 
3-990  3-284 

272  i 

Oregon  Entire-wheat  Flour 

8-25  i 

5-87 

80-35 

75-61  : 

3-900  3-420 

273  1 

Oregon  Straight-grade  Flour  . . 

7-55 

6-41 

81-82 

80-35 

3-880  3-686 

274 

[ Oklahoma  Graham  Flour 

16-81 

12-99 

72-35 

63-23 

4-178  3-367 

275 

' Oklahoma  Entire-wheat  Flour 

1 16-63 

13-24 

73-05 

66-11 

4-159  3-485 

276 

Oklahoma  Straight-grade  Flour 

1 15-06 

13-69 

73-57 

71-88 

4-040  3-721 

The  general  results  of  these  latter  experiments  are  in  entire  accord  with 
those  previously  described. 

Experiments  with  “ Bran  Flour  ” — The  lesser  digestibility  of  whole- 
meal and  graham  flour  is  at  times  attributed  to  the  coarseness  of  the  branny 
particles.  In  order  to  determine  what  influence  bran  in  a fine  state  of 
division  would  have  upon  the  completeness  of  digestion,  three  experiments 
were  made  with  straight -grade  flour  to  which  very  finely  ground  bran  was 
added.  For  convenience  this  material  has  been  designated  “ bran  flour.'^ 
This  bran  flour  was  prepared  from  milling  products  of  Oklahoma  wheat. 
A quantity  of  the  bran  (No.  413)  was  ground  until  it  was  very  fine.  Some 
of  the  ground  bran  was  then  mixed  with  straight -grade  flour  (No.  276), 
tlie  quantity  of  bran  in  the  mixture  (No.  415)  being  14  per  cent,  of  the  total, 
which  was  about  the  proportion  of  bran  removed  in  milling.  Bread  was^ 
made  from  this  modified  flour  in  the  same  way  as  with  the  ordinary  flours, 
and  was  used  in  digestion  experiments.  A summary  of  the  results  is  given 
in  the  first  table  on  the  following  page. 

Considering  the  averages  of  the  experiments  with  both  kinds  of  flour, 
the  digestibility  of  the  bread  from  the  flour  with  the  bran  was,  for  protein 
85-9  per  cent.,  and  for  carbohydrates  93-4  per  cent.,  whereas  that  of  the 
bread  from  the  same  flour  without  the  bran  was,  for  protein  90-9  per  cent., 
and  for  carbohydrates  97*7  per  cent.  The  inference  from  these  results  is 
that  the  addition  of  the  finely  ground  bran  decreased  the  digestibility  of 
the  product. 

Though  the  bran  flour  contained  a larger  percentage  of  protein  than  tho 
flour  without  the  bran,  in  consequence  of  its  lower  digestibility  the  nutritive 
value  of  the  former  was  actually  less,  as  will  be  apparent  from  a comparison 


THE  NUTRITIVE  VALUE  OF  BREAD.  545 


Digestibility  of  Nutrients  and  Availability  of  Energy  of  Bread 
FROM  Straight-Grade  Flour  with  and  without  Bran. 


Expel  i- 
ment 
No. 

Subject 

No. 

Kind  of  Bread. 

Protein. 

Carbohy- 

drates. 

Energy. 

487 

1 

Bread  from  Straight-grade  Flour 
with  Bran  added 

Per  cent. 

83-2 

Per  cent,  i 

93-0 

Per  cent. 

86-3 

488 

2 

Ditto  . . 

84-4 

92-8 

86-8 

489 

3 

Ditto  . . 

90-0 

94-3 

89-7 

Average  . . 

85-9 

j 93-4  1 

87-6 

478 

i 

1 

Bread  from  Straight-grade  Flour 
without  Bran  . . 

90-2 

96-7 

90-7 

I 479 

2 

Ditto  . . 

91-9 

98-2 

93-3 

480 

3 

Ditto  . . 

90-6 

98-1 

92-2 

1 

Average 

1 

90-9 

97-7 

92-1 

of  the  data  summarised  in  the  following  table,  showing  the  percentages  of 
total  and  digestible  nutrients  and  the  total  and  available  energy  per  gram 
in  both  kinds  of  flour  : — 


Comparison  of  Total  and  Digestible  Nutrients  and  Total  and 
Available  Energy  in  the  same  Flour  with  and  without  Bran. 


Sample 

No 

i 

Kind  of  Flour. 

Protein  (N  x 6-25). 

Carbohydrates,  j Energy  per  gram. 

Total. 

Digest- 

ible. 

i Total. 

Digest-  ^ . 

Avail- 

able. 

415 

Straight-grade  Flour  with  Bran 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct.  Calories. 

Calories. 

added  . . 

15-35 

13-19 

72-23 

67-46  3-876 

3-395 

276 

Straight-grade  Flour  without 

Bran  . . 

1 

15-06 

1 

13-69 

1 

73-57 

71-88  4-040 

1 

3-721 

There  was  a larger  percentage  of  total  protein  and  a smaller  percentage 
of  total  carbohydrates  in  the  flour  with  the  bran  than  in  that  without  it  ; 
but  comparing  the  digestible  nutrients  it  will  be  observed  that  what  little 
v as  gained  in  total  amount  added  by  including  the  finely  ground  bran  v^as 
more  than  lost  in  the  decreased  digestibility  due  to  the  addition  of  the  bran, 
the  proportions  of  digestible  nutrients  and  available  energy  being  larger 
in  the  flour  without  the  bran  added.  This  means  that  from  the  same  amounts 
of  both  kinds  of  flour  the  body  would  actually  derive  more  nutrients  and 
energy  from  the  flour  without  the  bran  in  spite  of  the  fact  that  the  amount 
of  protein  is  larger  in  the  flour  with  the  bran  added. 

Experiments  with  “ Germ  Flour  ” — Experiments  similar  to  those  with 
bran  were  also  made  to  determine  the  influence  of  the  addition  of  germ  to 
Avliite  flour.  A sample  of  germ  (No.  414,  obtained  in  milling  flour  No.  276) 
containing  29-88  per  cent,  of  protein  and  11-23  per  cent,  fat  was  ground 
in  the  same  manner  as  the  bran.  A mixture,  designated  as  “ germ  flour,"' 
was  then  made,  containing  93  per  cent,  of  Oklahoma  straight -grade  flour 
(No.  276)  and  7 per  cent,  of  the  finely  ground  germ,  the  germ  being  added 
in  about  the  same  proportion  as  is  removed  during  the  milhng  process. 
Bread  was  made  from  this  mixture  as  previously  described,  and  a digestion 
experiment  was  conducted  with  three  subjects.  The  results  of  the  experi- 
ments are  summarised  in  the  following  table.  For  comparison  the  results 

N N 


546 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  experiments  with  bread  made  from  the  same  flour  without  the  germ  arc 
also  included. 

Digestibility  of  Nutrients  and  Availability  of  Energy  of  Bread 
FROM  Straight-Grade  Flour  with  and  without  Germ. 


j Experi- 
' ment 
No. 

Sub- 

ject 

No. 

Kind  of  Bread. 

Protein. 

Carbohy- 

drates. 

Energy. 

1 

Per  cent. 

Per  cent. 

Per  cent. 

490  I 

1 

Bread  from  Flour  with  Germ  added 

i 87-6 

97-0 

90-5 

491 

2 

,,  ,,  ,,  ,, 

1 9M 

97-9 

92-3 

492 

3 

91-3 

97-9 

91-7 

t 

Average 

90-0 

97-6 

91-5 

478 

1 

Bread  from  Flour  without  Germ 

90-2 

96-7 

90-7 

479 

2 

J?  9? 

91-9 

98-2 

93-3 

480 

3 

90-6 

98-1 

92-2 

Average 

j 90-9 

97-7 

92-1 

Apparently  the  presence  of  the  finely  ground  germ  exerts  no  appreciable 
influence  upon  the  digestibility  of  the  flour. 

The  relative  nutritive  value  of  the  flour  with  and  without  the  germ  is 
illustrated  by  the  data  here  summarised. 

Comparison  of  Total  and  Digestible  Nutrients  and  Total  and 
Available  Energy  in  the  same  Flour  with  and  without  Germ. 


i 

Sample 

No. 

1 

Kind  of  Flour. 

1 

i 

Protein  (N  x 6-25) 

Carbohydrates. 

Energy  per  gram . 

Total. 

1 

Digest- 

tible. 

Total. 

Digest- 

ible. 

Total. 

Avail- 

able. 

416 

Straight-grade  Flour  with  Germ 

Per  ct. 

Per  ct. 

Per  ct. 

Per  ct. 

Calories. 

Calories . 

added  . . 

16*30 

14*67 

71*63 

69*91 

3*962 

3*625 

276 

Straight-grade  Flour  without 

Germ  . . 

15*06, 

13*69 

73*57 

i»- 

71*88 

4*040 

3*721 

As  will  be  seen,  both  the  total  protein  and  the  digestible  amount  are 
larger  with  the  germ  than  without  it,  the  order  being  reversed  in  the  case 
of  the  carbohydrates.  The  difference  is  much  greater  when,  as  in  the 
authors’  previously  described  experiments,  there  is  a much  larger  propor- 
tion of  germ  added.  Snyder  thus  summarises  the  whole  of  his  conclusions  : — 
In  fifty-four  digestion  trials  with  both  hard  spring  wheats  and  soft  winter  wheats 
in  which  six  separate  samples  of  wheat  have  been  milled  so  as  to  produce  the  three 
types  of  flour — graham,  entire-wheat,  and  straight  grade — uniform  results  have 
been  secured,  and  in  all  of  the  comparative  trials  the  largest  amounts  of  available 
nutrients  and  energy  have  been  secured  from  the  white  flour.  In  the  three  digestion 
trials  in  which  finely  pulverised  bran  was  added  to  white  flour  in  the  same  propor- 
tion as  is  removed  in  milling,  it  was  found  that  the  addition  of  the  bran  lowered  the 
digestibility  of  the  flour  so  that  a smaller  amount  of  digestible  nutrients  and  available 
energy  was  obtained  from  the  bran  flour  than  from  the  white  flour  with  which 
the  bran  was  mixed. 

648.  Mineral  Nutritive'  Value. — This  section  of  the  subject  has  not  been 
worked  out  with  anything  like  the  completeness  that  has  been  attained 
with  tlie  organic  constituents  of_flour.  Even  in  whole  wheat  the  ash  is 


THE  NUTRITIVE  VALUE  OF  BREAD. 


547 


not  very  high,  the  principal  constituents  being  phosphoric  acid  and  potash. 
As  stated  in  Chapter  V.,  the  potash  and  lime  are  proportionately  more  in 
the  fine  fiour  than  in  the  wheat  ; so  also  are  the  silica  and  ferric  oxide. 
Even  in  the  flour,  the  lime  is  very,  little  amounting  only  to  5*59  per  cent, 
of  the  total  ash. 

Hutchison  [Food  and  Dietetics,  1900,  Chapter  XVI.)  discusses  the  mineral 
requirements  of  the  body  somewhat  fully.  He  finds  that  the  amount  of 
mineral  matters  present  in  an  ordinary  mixed  diet  is  more  than  sufficient 
for  all  the  needs  of  the  body,  and  that  amount  he  fixes  at  about  20  grams  per 
day.  As  to  the  form  in  which  they  enter  into  an  ordinary  diet,  most  of  them 
are  in  a state  of  organic  combination,  such  as  calcium  and  phosphorus  in 
milk.  “ It  would  appear  that  such  organic  mineral  compounds  are  of 
special  value  in  nutrition.  It  cannot  be  maintained,  however,  that  it  is 
only  in  such  forms  that  mineral  matter  can  find  access  to  the  blood.  Ex- 
periment has  shown  that  even  such  a substance  as  carbonate  of  lime  is 
absorbed  to  some  extent.’'  From  analyses  of  human  milk,  it  would  appear 
that  an  infant  requires  about  0*33  gram  of  lime  daily  : the  adult  requires 
less,  because  of  the  cessation  of  the  growth  of  the  bones.  In  the  case  of 
pregnant  women,  the  requirements  of  the  foetus  in  the  way  of  bone  formation 
increases  the  demand  for  lime.  A litre  of  milk,  whether  whole  or  skimmed, 
contains  about  1 -5  grams  of  lime,  or  0 -86  gram  per  pint.  Hutchison  regards 
phosphorus  as  a most  important  building  material  of  the  body,  being  found 
in  cell  nuclei  and  in  abundance  in  bones  and  nerve  tissue.  It  is  therefore 
of  great  importance  during  the  development  of  young  animals.  Phosphorus 
is  present  to  a much  greater  extent  in  meats  than  in  vegetable  products  ; 
>among  the  latter,  haricot  beans  contain  a very  high  proportion.  “ The 
phosphorus  contained  in  foods  is  for  the  most  part  present  in  an  organic 
form  of  combination  . . . but  in  part  also  in  an  inorganic  form  as  phos- 
phates of  the  alkalies  or  earths.  There  is  reason  to  believe  that  the  organic 
forms  are  the  more  valuable  for  contributing  to  the  growth  and  repair  of 
tissue.  Examples  of  these  are  the  chemical  substances  nuclein,  lecithin, 
•glycero -phosphoric  acid,  and  phospho-carnic  acid,  all  of  which  are  probably 
valuable  dietetic  sources  of  the  element.  The  foods  richest  in  these  are 
such  articles  as  yolk  of  egg  . . . and  the  germ  of  wheat.  It  is  doubtful, 
on  the  other  hand,  whether  the  inorganic  compounds  containing  phosphorus 
are  of  much  value  in  the  body.  . . . One  can,  therefore,  hardly  approve 
of  the  addition  to  the  diet  of  phosphates  in  their  inorganic  form.  . . . 
The  recommendation  of  such  preparations  is  based  upon  the  groundless 
assumption  that  an  ordinary  mixed  diet  is  too  poor  in  phosphorus  to  be 
^ble  adequately  to  supply  our  need  of  that  substance.  It  may  be  remarked 
in  this  connection  that  we  know  of  no  diseased  condition  which  can  be 
•clearly  traced  to  a deficiency  of  phosphorus  in  the  diet.  This  is  true,  indeed, 
not  of  phosphorus  alone,  but  of  all  the  other  mineral  ingredients  of  the  diet 
with  the  exception  of  iron,  and  possibly  also  of  calcium.  A deficiency  of 
iron  in  the  food  may,  as  already  remarked,  lead  to  the  development  of 
anaemia,  and  too  little  lime  in  the  food  may  cause  the  bones  of  children  to 
become  soft  ; but  with  these  rather  doubtful  exceptions  it  may  be  safely 
assumed  that  an  ordinary  diet  will  amj^ly  provide  for  all  the  mineral  matter 
we  require.”  Hutchison  further  remarked  that  “ of  the  comparatively  small 
amount  of  mineral  matter  met  with  in  bread,  one-fourth  is  excreted  uii- 
absorbed.  Seeing  that  this  is  the  case,  it  is  surely  futile  to  recommend  the 
use  of  bread  containing  a larger  amount  of  mineral  constituents.” 

As  already  observed,  Brunton  and  Tunnicliffe  regard  brown  bread  as 
being  preferable  to  white  where  mineral  ingredients  and  especially  lime  salts 
are  deficient  in  other  articles  of  food.  As  wheat  is  one  of  those  articles 
in  which  lime  is  very  deficient,  it  is  difficult  to  see  where  in  any  case  bread, 


548 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


whether  brown  or  wliite,  can  very  materially  help  as  a lime  food.  On  this 
point,  Girard  states  that  the  difference  in  amount  of  phosphoric  acid  in 
white  and  brown  breads  is  but  small,  and  that  in  view  of  the  quantity  of 
phosphoric  acid  contained  in  ordinary  food  rations,  this  difference  is  insig- 
nificant. In  any  case  there  is  a large  excess  of  phosphoric  acid  in  the  food 
over  the  highest  estimate  of  what  is  normally  eliminated  (viz.,  3 T9  grams 
per  day).  He  therefore  concludes  that  for  general  consumption  white 
bread  is  the  best.  (Comptes  Rend.,  1896,  122,  1382.) 

649.  Importance  of  the  Mineral  Constituents  of  Foods,  Ingle. — A paper 
on  this  subject  was  read  at  the  Leeds  Congress  of  the  Royal  Institute  of 
Public  Health  in  1909.  From  the  analogy  of  milk,  Ingle  regards  the  most 
suitable  proportions  of  lime  and  phosphoric  acid  (P2O5)  in  food  as  being 
about  0-87  of  hme  to  1 of  phosphoric  acid.  In  support  of  this  view  he  cites 
the  authority  of  Weiske,  by  whom  it  has  been  shown  that  rabbits  fed  on 
oats  alone  developed  thin,  fragile  skeletons,  while  similar  animals  fed  upon 
oats  and  meadow-hay  produced  normal  bones  ; moreover,  that  the  addi- 
tion of  sodium  dihydrogen  phosphate  to  the  diet  intensified  the  bad  effect 
upon  bone  development,  while  the  addition  of  calcium  carbonate  to  a diet 
of  oats  only,  greatly  improved  the  development  of  bone.  Now  oats  contain 
about  seven  times  as  much  phosphoric  acid  as  lime,  while  meadow-hay 
contains  2-5  times  as  much  lime  as  phosphoric  acid.  The  wTiter  points- 
out  that  in  seeds  generally,  among  which  wheat  is  included,  there  is  this 
injurious  excess  of  phosphoric  acid,  and  although  in  wheat  there  is  between 
three  and  four  times  as  much  magnesia  as  lime,  yet  for  bone  formation, 
magnesia  can  only  to  a limited  extent  replace  lime,  for  in  the  ash  of  bone 
only  about  1 per  cent,  of  magnesium  phosphate  is  usually  found,  as  com- 
joared  with  from  84  to  87  per  cent,  of  calcium  phosphate. 

The  vTiter  then  proceeds  to  express  himself  very  strongly  as  to  the  merits, 
or  ratlier  demerits,  of  bran  in  the  following  terms  : — “ Allusion  may  here  be 
made  to  what  the  writer  believes  to  be  a widespread  fallacy — the  impression 
that  bran  is  well  adapted  to  promote  bone  formation  and  nutrition.  Bran 
is  rich  in  ash,  but  contains  an  overwhelming  excess  of  phosphorus  pentoxide 
over  lime — in  some  samples  the  writer  found  the  ratio  to  be  as  high  as 
1 : 0-055 — and,  according  to  the  views  here  given,  should  be  extremely  un- 
suited to  bone  nutrition.  This  is  indeed  the  case,  for  a disease  of  the  bones 
of  liorses,  known  as  ‘ millers’  horse  rickets  ’ or  ‘ bran  rachitis,’  is  knovui  to 
be  produced  by  the  excessive  use  of  bran  as  food.”  He  regards  bone  dis- 
eases, e.g.,  rickets,  as  being  probably  associated  with  the  use  of  a diet  con- 
taining a preponderance  of  phosphoric  acid  over  hme,  and  suggests  as  a 
remedy  for  deficiencies  in  mineral  constituents  of  food  their  artificial  addi- 
tion in  the  form  of  inorganic  compounds.  Thus  in  the  preparation  of 
‘‘  liumanised  ” milk  from  cows’  milk,  he  recommends  the  addition  of  finely 
divided  calcium  carbonate.  Ingle  regards  the  preponderance  of  phosphoric 
acid  rather  than  the  deficiency  of  lime  in  cows’  milk  as  being  the  cause  which 
renders  it  more  liable  than  human  milk  to  induce  malnutrition  of  bone  in 
infants.  The  same  preponderance  of  phosphoric  acid  leads  him  to  regard 
wlieat,  flour,  and  bread,  as  not  presenting  the  most  favourable  conditions 
for  bone  development.  He  recognises,  however,  that  cereal  grains  and 
their  products  form  a large  proportion  of  human  diet  without  ill  effects, 
and  for  adults  at  least  the  excess  of  phosphoric  acid  is  not  injurious.  He 
regards  this  as  being  possibly  due  to  different  requirements  in  man  to  other 
animals,  and  also  to  the  fact  that  the  phosphoric  acid  of  the  ash  does  not 
all  exist  in  the  grain  as  such,  but  is  largely  derived  from  organic  phosphorus 
combinations  as  lecitliin.  Such  phosphorus  is  possibly  not  converted  into 
ifiiosphoric  acid  in  the  body,  and  would  therefore  not  act  harmfully  in  bona 


THE  NUTRITIVE  VALUE  OF  BREAD. 


549 


nutrition,  the  really  important  ratio  being  that  of  lime  to  phosphorus  pent- 
oxide  existing  as  acid  in  the  food.  [Jour.  Royal  Institute  of  Public  Health, 
1909,  XVII.,  736.) 

650.  Nutritive  Value  of  Phosphates,  Holsti. — Almost  concurrently  'with 
Ingle,  Holsti  points  out  that  experiments  on  animals  in  which  the  question 
has  been  investigated  whether  the  body  can  obtain  its  phosphorus  from 
inorganic  sources,  have  not  in  the  hands  of  various  investigators  yielded 
concordant  results.  In  the  present  experiments  described  by  him,  in  which 
organic  and  inorganic  phosphorus  were  determined  in  the  food  and  excre- 
tions of  man,  the  result  obtained  is  that  it  is  possible  to  supply  the  necessary 
phosphorus  in  large  measure  from  inorganic  phosphates.  (Skand.  Arch. 
Physiol.,  1909,  23,  143.) 

651  Conclusions. — The  balance  of  evidence  is  in  favour  of  the  view  that 
ordinary  diet  contains  a more  than  sufficient  quantity  of  phosphorus,  and 
therefore  that  the  amount  present  in  bread  is  of  but  little  or  no  importance. 
Ingle  goes  further  and  regards  the  preponderance  of  phosphoric  acid  over 
lime  as  positively  detrimental.  There  is  considerable  divergence  of  opinion 
as  to  the  nutritive  value  of  phosphates.  Thus  Hutchison  looks  upon  them 
with  doubt,  but  admits  that  in  certain  cases  inorganic  salts  such  as  calcium 
carbonate  undergo  some  degree  of  absorption.  Ingle  evidently  agrees 
with  Wieske  that  oats  is  a very  bad  bone-forming  food,  and  similarly  con- 
demns wheat  ; they  both  regard  the  addition  of  calcium  carbonate  as  a 
definite  bone-food.  Ingle  rather  queries  whether  the  phosphorus  of  such 
organic  compounds  as  lecithin  is  even  converted  into  phosphoric  acid  in 
the  body.  If  not,  it  evidently  cannot  act  as  a bone  nutrient,  for  which  the 
inorganic  calcium  phosphate  is  required.  Holsti,  as  a result  of  direct  experi- 
ment, regards  inorganic  phosphates  as  capable  of  supplying  a large  measure 
of  the  necessary  phosphorus  of  the  body.  The  authors  suggest  as  a pro- 
bable solution  of  the  problem  that  the  human  body  requires  phosphorus 
in  two  distinct  forms  : (1)  as  organic  compounds  for  the  building  up  of  brain 
and  nerve  tissue,  which  contain  such  compounds  of  phosphorus  in  large 
quantity ; (2)  as  inorganic  salts  for  the  building  up  of  bone  tissue,  which 
consists  largely  of  calcium  phosphate.  Lecithin  and  such  substances  will 
naturally  go  to  the  construction  of  nerve  tissue,  and  inorganic  phosphates 
to  bone-formation  When  either  organic  or  inorganic  compounds  of  phos- 
phorus are  deficient,  the  human  body  is  probably  able  to  utilise  for  both 
purposes  phosphorus  compounds  of  either  type. 

In  the  case  of  lime,  the  position  is  different,  Brunton  and  Tunnicliffe, 
Ingle,  and  to  a lesser  degree  Hutchison,  regard  lime-starvation  as  being 
within  the  bounds  of  possibility.  Ingle  adduces  very  strong  evidence  that 
such  deficiency  may  be  made  up  by  the  use  of  lime  carbonate  as  a part  of 
the  food.  Unfortunately,  wheat  in  any  of  its  forms  contains  very  little 
lime.  In  particular,  the  use  of  bran  as  a food  is  strongly  contra-indicated, 
as  it  may  very  possibly  be  the  cause  of  actual  injury  to  bone  formation  and 
nutrition. 

652.  Comparative' Bacteriological  Purity. — Owing  to  causes  over  which 
the  miller  has  no  control  some  wheats  reach  him  in  a very  dirty  condition. 
As  a remedy  most  complete  installations  of  wheat-cleaning  machinery 
form  part  of  the  equipment  of  every  modern  mill.  The  wheat  is  dry- 
scoured,  washed  most  thoroughly  and  dried  ; but  it  is  impossible,  owing 
largely  to  the  crease  in  the  grain,  to  thus  ensure  its  absolute  freedom  from 
external  impurity.  Such  impurity  is  naturally  associated  with  the  bran, 
and  during  the  operations  of  milling  remains  in  most  part  attached  thereto. 
A portion  is  rubbed  off  by  the  more  severe  reductions  into  the  lower  grade 


550 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


flours,  but  the  higher  grade  flours  are  practically  free  from  any  contamina- 
tion that  may  exist  on  the  outer  side  of  the  bran.  Among  such  impurities 
are  found  large  numbers  of  bacteria,  and  some  of  these  may  be  very  objec- 
tionable, and  in  rare  cases  even  dangerous  in  their  natuie.  In  consequence, 
whole-meal  and  the  darker  low-grade  flours  are  much  more  liable  to  bacterial 
contamination  than  those  of  the  patent  types.  The  results  of  these  con- 
ditions have  long  been  familiar  to  the  baker,  who  knows  that  the  darker 
flours  are  much  more  likely  to  produce  sour  bread.  In  the  following  experi- 
ment a first  patent  flour  and  a dark  or  low-grade  flour  from  the  same  class 
of  wheat  were  taken,  and  fermented  and  baked  in  precisely  the  same  way. 
Loaves  were  baked  from  each  after  3J  hours  and  9 hours’  fermentation 
respectively.  They  yielded  on  analysis  the  following  amounts  of  acidity 
per  cent.  : — - 

White  Bread,  Dark  Bread. 

After  3J  hours  ..  ..  ..  ..  0-477  1-140 

After  9 hours  ..  ..  ..  ..  ..  0-491  1-300 

The  less  fermented  loaves  had  the  following  characteristics  : White, 
sweet  in  smell  and  taste  ; Dark,  characteristic  odour  of  bread  from  low- 
grade  flours,  but  perfectly  sweet  in  taste  and  smell.  The  9-hour  loaves 
had  shown  some  further  change.  The  White  was  darker  in  colour,  had  an 
incipient  sour  smell,  but  no  sour  taste.  The  Dark  had  the  colour  changed  to 
dark  reddish  brown,  sour  smell,  and  unpleasant  taste,  rather  of  decomposi- 
tion than  acidity. 

Kenwood,  in  conjunction  with  one  of  the  authors,  has  on  several  occa- 
sions made  comparative  bacteriological  examinations  of  wheat  and  flours. 
The  following  are  the  results  of  one  such  test.  Three  flours  were  taken  : — 

A.  Highest  grade  patent  flour. 

B.  Lower  grade  flour. 

C.  Stone-milled  flour. 

These  were  similarly  treated,  and  preparations  of  each  were  incubated  for 
bacteria  on  gelatin  plates.  At  the  end  of  42  hours  the  following  observations 
were  made  : — 

A.  No  growth. 

B.  Four  large  colonies  and  over  100  small  ones  (non-liquefying). 

C.  Twenty  well-marked  colonies,  and  many  organisms  (which  could 
not  be  enumerated),  had  liquefled  one-third  of  the  gelatin. 

At  the  end  of  72  hours  : — 

A.  One  non-liquefying  colony. 

B.  One  liquefying  colony,  and  quite  200  small  non-liquefying  ones. 

C.  The  gelatin  was  entirely  liquefied. 

In  another  test,  experiments  were  made  with  a wheat  containing  B.  coli 
communis.  The  wheat  itself  yielded  twelve  colonies  of  coli.  Samples  of 
liighest  grade  flour,  medium  grade  flour,  and  bran  from  this  wheat  were 
examined.  Repeated  tests  on  the  highest  grade  flour  gave  no  growths  of 
coli.  In  each  of  separate  tests,  two  colonies  of  coli  were  obtained  from 
the  medium  grade  flour.  The  bran  yielded  a growth  of  coli  which  covered 
the  gelatin  plate. 

High  grade  flours  are  practically  sterile,  and  bacteriologically  cleaner 
than  medium  and  low-grade  flours,  and  far  cleaner  than  whole-meals.  Such 
organisms  as  B.  coli  communis,  if  present  in  the  wheat,  are  absent  from  the 
liighest  grade  flour,  present  in  small  quantity  on  that  of  medium  grade, 
and  abundant  in  whole-meal.  The  same  differentiation  would  no  doubt 
apply  to  other  organisms  having  the  same  habitat  as  B.  coli  communis,  if 
they  happened  to  be  present. 


THE  NUTRITIVE  VALUE  OF  BREAD. 


551 


653.  Attractiveness  and  Palatability. — These  two  factors  have  immense 
weight  in  deciding  what  shall  be  the  leading  type  ot  bread  consumed  by 
the  community.  They  are  also  of  the  utmost  importance.  As  long  ago 
as  1857,  Lawes  and  Gilbert  recognised  that  : “ It  is  also  well-known  that 
the  poorer  classes  almost  invariably  prefer  the  whiter  bread,  and  among 
some  of  those  who  work  the  hardest  and  who  consequently  soonest  appre- 
ciate a difference  in  nutritive  quality  (navvies,  for  example)  it  is  distinctly 
stated  that  their  preference  for  the  whiter  bread  is  founded  on  the  fact  that 
the  browner  passes  through  them  too  rapidly  ; consequently,  before  their 
systems  have  extracted  from  it  as  much  nutritions  matter  as  it  ought  to 
yield  them.''  The  fact  of  this  preference  also  applies  to  such  districts  as 
some  parts  of  Scotland,  where  very  little  meat  is  eaten,  and  also  to  even  the 
poorest  parts  of  Ireland.  In  both  cases  a very  white  bread  is  demanded. 
But  not  only  does  this  taste  exist  among  the  poorer  and  harder  physically 
worked  classes,  it  is  also  general  throughout  the  whole  community.  As 
recently  stated  in  the  daily  press,  “ there  is  a popular  craving  for  white 
bread."  If  asked  the  reason  why  they  preferred  a white  loaf,  the  probable 
answer  of  the  people  would  be  We  prefer  a white  loaf  because  it  is  more 
dainty  in  appearance,  and  because  whiteness  is  instinctively  associated 
with  cleanliness.  A muddy-looking  loaf  may  be  quite  clean,  but  does  not 
so  thoroughly  convey  that  impression  as  a creamy  white  one.  Further, 
the  white  loaf  has  a nicer  taste."  Snyder  puts  it  on  record  that  during  the 
severe  monotony  of  his  digestion  tests,  in  which  the  subjects  were  restricted 
to  a diet  of  bread  and  milk  only,  they  keenly  preferred  the  white  bread  to 
the  browm.  In  other  words,  the  general  taste  regards  the  white  loaf  as  the 
more  attractive  and  palatable.  Authorities  on  diet  regard  both  of  these  as 
being  of  importance.  Tunnicliffe  writes  : “ Recent  research  has  distinctly 
taught  us  that,  from  the  point  of  view  of  its  nutritive  value,  great  importance 
attaches  to  the  appetising  appearance  of  food."  [Blue  Book  on  the  Use  of 
Preservatives  in  Food,  p.  xxxi.).  Hutchison  is  also  strongly  in  favour  of 
regarding  the  flavour  of  food  as  one  of  the  essential  characteristics  of  the 
diet.  He  sums  up  his  position  by  the  remark  : “To  persons  of  jaded 
appetite,  however,  and  to  invahds  and  convalescents,  the  flavouring  agents 
of  the  food  are  very  powerful  aids  to  digestion,  and  no  adjustment  of  the 
diet  in  such  cases  can  be  regarded  as  satisfactory  which  leaves  this 
consideration  out  of  account."  {Food  and  Dietetics,  p.  274.)  On  general 
dietary  principles,  therefore,  there  is  a scientific  justification  for  the  popular 
preference. 

654.  Complementary  Foods  to  Bread. — In  view  of  the  fact  that  bread 
is  naturally  deficient  in  protein  and  fat,  amongst  organic  nutrients,  and 
in  lime  among  mineral  matters,  it  may  be  well  to  indicate  those  articles  of 
food  which  are  appropriately  regarded  as  complementary  or  supplementary 
to  bread  itself.  Bread  is  very  rarely  eaten  alone  ; meat  and  cheese  supply 
its  deficiency  in  protein  ; leguminous  vegetables  such  as  haricot  beans 
have  the  same  effect.  Fat  is  almost  universally  added  to  bread  in  the  form 
of  butter.  Dietetically,  jam  or  other  sweets  cannot  be  regarded  as  an 
efficient  substitute  for  butter,  margarine,  or  dripping.  In  view  of  the 
deficiency  in  lime,  milk  is  strongly  indicated  as  an  accompaniment  to  bread. 
Here  custom  anticipates  science  by  causing  bread- and- milk  to  occupy  a 
prominent  position  in  the  dietary  of  children.  May  not  the  reputation  of 
“ the  halesome  parritch  " as  a bone-food  be  largely  due  to  the  milk  consumed 
therewith  rather  than  to  the  oats  from  which  it  is  prepared?' 

In  improved  methods  of  bread-making,  both  fat  and  milk  are  at  times 
employed.  Both  are  good  ; but  the  latter  especially,  whether  with  or 
without  the  cream,  serves  to  increase  the  lime  content  of  the  bread.  If 


552 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


bread  be  made  entirely  with  skimmed  milk,  a half  kilo  (approximately 
1 lb.)  will  contain  about  0-3  gram  of  lime,  or  roughly  the  daily  amount  re- 
quired by  an  infant.  Such  bread  would  be  far  better  adapted  to  the  require- 
ments of  pregnant  women  than  that  from  whole-meal.  Judging  by  analogy, 
the  addition  of  a small  proportion  of  an  appropriate  lime  salt  would  be  a 
further  advantage.  Such  salt  might  possibly  be  the  carbonate,  which 
would  be  changed  into  the  chloride  by  the  hydrochloric  acid  of  the  gastric 
juice  ; or  it  might  be  added  direct  as  the  chloride,  in  which  case  it  would 
partly  replace  sodium  chloride  or  common  salt. 

In  some  districts  a portion  of  the  liquor  used  in  making  dough  consists 
of  lime-water  ; the  lime  of  this  is  converted  into  the  carbonate,  by  the 
carbon-dioxide  gas  evolved  during  fermentation.  The  use  of  hard  waters 
for  bread-making,  t.e.,  those  containing  calcium  carbonate  or  sulphate, 
also  adds  to  the  lime  content  of  the  bread.  Hard  water  is  itself  an  important 
source  of  lime  in  the  daily  income  of  food,  and  may  under  certain  circum- 
stances contribute  that  substance  in  excess. 

655.  Summary. — The  foregoing  data  justify  the  following  conclusions. 

Taking  breads  as  supplied  by  the  baker,  white  bread  is  more  nutritious 
than  whole-meal  or  ordinary  brown  breads.  The  average  best  white  bread 
is  more  nutritious  than  the  second  quality  or  that  made  from  the  darker 
or  low-grade  flours. 

When  from  any  kind  of  wheat,  standard  patent  (which  is  practically  the 
whole  of  the  flour  of  the  wheat)  is  compared  with  entire- wheat,  and  graham 
flour  from  the  same  wheat,  the  white  flour  yields  more  nutriment  and  energy 
than  either  of  the  others. 

The  addition  of  finely  divided  bran  to  white  flour  lowers  the  nutritive 
value  of  the  mixture. 

The  addition  of  germ  in  excess  of  that  normally  present  in  wheat,  in- 
creases the  nutritive  value  of  the  bread. 

Wheat  and  all  kinds  of  flour  therefrom  are  comparatively  poor  in  mineral 
constituents.  The  phosphoric  acid  is  largely  in  excess  of  the  lime.  No 
diseased  condition  is  known,  which  can  be  clearly  traced  to  a deficiency 
of  phosphorus  in  the  diet.  All  breads  contain  more  phosphates  than  are 
absorbed  by  the  human  digestive  system.  All  wheat  preparations  are 
deficient  in  lime.  Bran  is  detrimental  to  healthy  bone-formation. 

The  human  body  requires  phosphorus  in  two  distinct  forms,  as  organic 
compounds  for  the  building  up  of  brain  and  other  phosphoric  tissues,  and 
as  inorganic  salts  for  the  building  up  of  bone  tissue  which  consists  largely 
of  calcium  phosphate.  In  case  of  deficiency  of  compounds  of  either  type, 
the  body  is  probably  able  to  utilise  for  both  purposes  phosphorus  compounds 
of  either  variety. 

Wheat  is  liable  to  bacteriological  contamination,  which  conceivably 
may  be  of  objectionable  or  even  dangerous  character.  The  whole-meal 
wili  obviously  contain  the  same  bacteria  as  the  wheat.  The  low-grade 
flours  contain  less  bacteria  than  the  wheat,  but  some  are  still  present.  The 
high-grade  or  patent  flour  is  practically  bacteriologically  clean,  even  when 
made  from  a eontaminated  wheat. 

The  bakers’  best  white  bread -is  more  attractive  and  palatable  than 
darker  coloured  or  whole-meal  breads  made  from  plain  flour  or  meal  only. 
These  in  themselves  are  valuable  nutritive  assets. 

The  nutritive  deficiencies  of  bread  are  best  remedied  by  the  addition 
of  butter,  milk,  cheese,  meat,  and  leguminous  vegetables  to  the  diet.  These 
suj)ply  respectively  fat,  lime  salts,  and  protein.  Hard  water,  or  appropriate 
lime  salts  added  direct,  would  probably  help  in  correcting  the  deficiency  of 
lime  in  wheat. 


THE  NUTRITIVE  VALUE  OF  BREAD. 


553 

No  case  has  been  made  out  for  recommending  the  use  of  Avhole-meal 
Bread  by  growing  children  or  i:>regnant  or  nursing  women. 

656.  “ Standard  Bread.” — Since  the  foregoing  was  written  there  has 
been  a revival  of  the  controversy  as  to  the  respective  merits  of  various 
types  of  bread.  An  important  contribution  to  the  discussion  consisted  of 
a manifesto  signed  by  eight  eminent  London  medical  men,  of  which  the 
following  is  a copy  : — 

“ We,  the  undersigned,  believe  it  to  be  a national  necessity  that  a stan- 
dard should  be  fixed  for  the  nutritive  value  of  what  is  sold  as  bread.  Such 
a standard  has  already  been  enforced  by  law  for  milk.  The  standardisation 
of  bread  is  even  more  important,  bread  and  flour  forming  about  two -fifths 
of  the  weight  of  the  food  consumed  by  the  working  classes  and  constituting 
almost  the  whole  diet  of  many  poor  children. 

“ In  view  of  the  inf erior  nourishing  qualities  of  the  white  bread  commonly 
sold  in  this  country,  we  urge  that  legislation  should  be  passed  making  it 
compulsory  that  all  bread  sold  as  such  should,  unless  distinctly  labelled 
otherwise,  be  made  from  unadulterated  wheat  flour  containing  at  least  80 
per  cent,  of  the  whole  wheat,  including  the  germ  and  semolina.” 

It  is  to  be  feared  that  the  fixing  of  a standard  for  the  nutritive  value  of 
bread  is  not  so  simple  as  would  appear  on  the  face  of  the  above  document. 
Taking  two  such  typical  wheats  as  English  and  Manitoban  of  the  1910  crop, 
both  largely  used  by  British  millers,  their  protein  contents  were  9-2  and  14-3 
per  cent,  respectively.  If  both  were  turned  into  standard  flour,  the  Mani- 
toban would  in  protein  value  be  more  than  half  as  rich  again  as  the  English. 
These  extremes  are  as  a matter  of  fact  much  wider  than  are  met  with  in 
practice  in  commercial  wheat  flours.  In  other  words,  the  so-called  standard 
permits  a greater  variation  in  nutritive  value  than  is  found  without  its 
adoption  in  the  white  bread  flours  of  ordinary  bakers. 

In  practice,  the  miller  aims  at  getting  as  long  a straight-run  flour  as 
he  can  out  of  every  variety  of  wheat.  By  straight -run  is  meant  the  whole 
of  the  flour  the  wheat  is  capable  of  yielding  in  a condition  of  freedom  from 
particles  of  the  branny  envelope  or  germ.  The  percentage  of  such  straight- 
run  flour  varies  considerably  in  different  wheats.  In  the  dictionary  of 
wheats,  pages  284-289,  the  extreme  figures  given  are  60  and  74  per  cent, 
respectively.  In  exceptional  wheats  the  yield  may  be  as  low  as  55  per 
cent,  or  as  high  as  75  per  cent,  of  perfectly  good  flour.  This  straight-run 
flour  is  the  normal  product  of  every  mill,  and  has  always  been  obtainable 
commercially  without  the  least  difflculty.  In  practice  some  of  the  straight- 
run  is  divided  into  a whiter  flour  known  as  “ patents,”  and  a darker  flour 
called  households  or  “ seconds.”  By  whatever  names  they  may  be  Imown 
the  millers’  leading  grades  are  : — 

1.  Best  quality,  consisting  of  “ patents  ” or  whitest  portions  of  straight- 
run. 

2.  Second  quality,  consisting  of  straight-run. 

3.  Third  quality,  consisting  of  the  remainder  of  the  straight-run  after 
the  removal  of  the  patents. 

Obviously,  intermediate  flours  may  be  prepared  by  mixing  these  three 
varieties  in  different  quantities  or  altering  the  proportions  of  patents  and 
remainders  into  which  the  straight-run  is  separated.  But  the  main  thing 
is  that  the  straight-run  is  the  starting  point  ; the  variations  therefrom  are 
simply  further  separations  made  to  meet  the  requirements  of  purchasers. 
The  millers’  straight-run  is  the  whole  of  the  flour  of  the  wheat  and  no  more 
than  the  flour,  and  varies  in  percentage  with  the  actual  flour  content  of  the 
wheat  itself.  The  suggested  standard  is  “ at  least  80  per  cent,  of  the  whole 
wheat,”  and  takes  no  cognisance  of  the  amount  of  flour  the  wheat  really 


554 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


possesses.  Thus  a standard  flour  made  from  Azima  or  Ghirka  wheat  would 
contain  about  75  per  cent,  straight-run  flour,  and  25  per  cent,  of  germ  and 
branny  matter.  If  the  standard  flour  be  milled  from  Minnesota  or  Mani- 
toba wheats,  it  will  contain  92-5  per  cent,  of  straight-run  flour  and  7*5  per 
cent,  of  germ  and  branny  matter.  Which  of  these  is  the  more  desirable 
quantity  ? Or  if  7*5  per  cent,  of  offal  is  sufficient  for  a standard  with 
Manitoba  wheats,  why  insist  on  25  per  cent,  in  the  standard  flour  from 
Azima  ? If  a certain  proportion  of  branny  matter  is  desirable  in  all  flours, 
then  surely  in  a proposed  standard  having  legal  sanction,  the  proper  and 
most  desirable  amount  should  be  fixed  a little  more  precisely. 

In  the  next  place  the  standard  flour  must  include  the  germ.  In  old 
stone-milling  times  the  germ  was  always  more  or  less  comminuted  by  the 
millstone,  and  so  some  portion  got  into  the  flour  ; but  even  in  those  days 
the  main  part  was  dressed  out  with  the  offal.  Still  the  portion  which 
found  its  way  into  the  flour  was  sufficient  to  materially  injure  the  quality. 
The  most  essential  functions  of  the  germ  in  the  economy  of  the  growing 
wheat  plant  are  to  effect  the  decomposition  of  both  the  starch  and  protein 
contents  of  the  endosperm.  In  the  resting  seed  the  germ  is  separated 
from  the  endosperm  by  the  scutellum  or  shield,  and  thus  is  inactive  until 
subjected  to  those  conditions  of  warmth  and  moisture  which  induce  ger- 
mination. But  if  ground  up  into  the  flour  its  enzymes  are  set  free,  and 
may  at  once  in  the  presence  of  sufficient  warmth  and  moisture  commence 
the  attack  on  the  endosperm.  It  is  a matter  of  common  knowledge  among 
millers  that  in  fact  objectionable  changes  do  take  place  in  flour  containing 
germ  from  the  very  time  of  manufacture.  Further,  when  such  flour  is  sub- 
jected to  fermentation,  excessive  diastatic  action  is  likely  to  occur,  and 
hence  a sticky  dough  is  liable  to  be  produced,  which  yields  comparatively 
heavy  small  loaves.  It  is  because  of  such  reasons  that  millers  incurred  the 
expense  of  efficient  germ-removing  plant,  and  sold  their  separated  germ 
as  offal,  rather  than  put  it  in  their  flour  and  sell  it  as  flour.  If  the  buying^ 
public  is  willing  to  condone  the  faults  of  the  germ,  the  miller  will  be  only 
too  pleased  to  return  it  to  the  flour  sack.  Reference  may  here  be  appro- 
priately made  to  the  nature  of  the  inner  layers  of  the  bran,  which  form  a 
large  proportion  of  the  additional  matter  proposed  to  be  incorporated  in 
the  80  per  cent,  flour.  Like  the  germ,  these  are  rich  in  enzymes,  and  to- 
gether with  it  are  potent  agents  of  change  in  the  dough  during  fermentation. 
The  both  will  favour  the  production  of  acidity  in  bread  ; and  in  summer 
time  standard  dough  and  bread  will  afford  a peculiarly  suitable  environ- 
ment for  the  development  of  ropiness  in  the  presence  of  the  rope  organism. 
Where  standard  bread  is  being  made,  a keen  look-out  should  therefore  be 
kept  for  the  first  signs  of  the  advent  of  this  trouble.  (See  paragraphs. 
583,  584,  587.) 

As  a set-off  against  the  before-recited  bad  qualities  of  the  germ,  it  has 
naturally  a very  high  nutritive  value  ; but  the  quantity  present  in  wheat 
amounts  only  to  from  1-5  to  2-0  per  cent,  of  the  entire  grain.  Taking  a 
78  per  cent,  flour  without  the  germ,  and  adding  thereto  one  thirty-ninth 
its  weight  of  germ,  the  quantity  of  fat  would  theoretically  be  increased  by 
about  0-3  per  cent.,  say  from  1-2  to  1-5.  The  percentage  of  protein  would 
similarly  be  increased  about  0-55,  or  say  from  II  *6  to  I2T5  per  cent. 

In  tile  next  place  tlie  standard  flour  must  contain  the  semolina.  Semo- 
lina is  a millers’  term  for  the  small  granular  fragments  into  which  the 
endosperm  of  a grain  of  wheat  is  broken  during  the  process  of  its  gradual 
reduction.  In  milling  operations  these  are  all  at  last  ground  into  flour 
and  find  tlieir  way  into  the  straight-run  flour.  When  such  straight-run  i& 
separated  into  a first  and  third  quality,  some  streams  of  semolina  are  used 
for  the  manufacture  of  the  higher  quality  and  some  for  the  lower,  so  that 


THE  NUTRITIVE  VALUE  OF  BREAD. 


555 


neither  of  the  two  fractions  contains  all  the  semolina.  The  intention  is 
probably  to  insist  that  the  standard  flour  shall  contain  all  the  straight-run 
flour  and  sufficient  other  matter  to  bring  the  percentage  up  to  80  of  that  of 
the  wheat. 

One  of  the  last  but  not  the  least  of  the  points  remaining  to  be  dealt 
with  in  the  manifesto  is  the  allegation  that  the  white  bread  commonly  sold 
in  this  country  is  of  inferior  nourishing  qualities.  This  merits  some  rather 
more  detailed  examination,  and  accordingly  the  authors  asked  a responsible 
firm  of  millers  to  specially  mill  for  them,  under  the  firm’s  personal  super- 
vision, a series  of  flours.  For  several  reasons,  English  wheat  was  selected 
for  the  purpose  ; first  because  it  is  naturally  a sweet  flavoured  wheat,  and 
secondly  because  it  has  been  widely  advocated  for  the  manufacture  of 
standard  flour.  The  following  samples  were  prepared  : — 

I.  Straight-run  roller-milled  flour,  amounting  to  70  per  cent,  of  the  wheat. 

II.  Stone-ground  flour  from  the  same  wheat,  with  20  per  cent,  of  the 
coarser  bran  removed,  leaving  80  per  cent,  of  the  wheat  to  form  standard 
flour. 

III.  Patent  flour  consisting  of  30  per  cent,  of  the  straight-run. 

IV.  Bakers’  flour  consisting  of  the  remaining  70  per  cent,  of  the  straight- 
run. 

Being  asked  to  quote  the  commercial  price  of  these  flours,  the  millers 
replied  : “Of  course  such  flours  as  these  would  not  be  used  hy  bakers.  They 
demand  a blend  of  70-80  per  cent,  foreign.  The  prices  are  as  under, 
net  delivered  : stone-ground,  21s.  ; patent,  29,9.  ; and  bakers’,  2Qs.  per 
sack.”  In  view  of  the  millers’  strong  expression  of  opinion,  a further 
sample  of  flour  was  prepared  by  the  authors,  in  order  to  imitate  more  closely 
the  actual  mixture,  containing  English  wheat,  which  would  be  prepared  for 
the  baker  and  sold  by  him  as  bread  to  the  public.  This  had  the  following 
composition : — 

V.  Mixture  of  50  per  cent,  straight-run  flour.  No.  I.,  with  50  per  cent, 
strong  American  patent  flour. 

The  whole  of  these  were  subjected  to  analysis  with  the  folio vdng  results: — ■ 


Analyses  of  Flours. 


Constituents. 

I.  S.R. 

II.  Std. 

III.  Ptnt. 

IV.  Bkrs. 

V.  i Am. 

Moisture  . . . . . . , 

14  82 

14-12 

14-60 

1500 

13-20 

Proteins 

10  09 

11-05 

9-97 

10  21 

11-90 

Carbohydrates.  . . . . . i 

73-37 

7271 

7421 

7306 

73-24 

Fat 

1-10 

1-38 

0-84 

1-17 

1-16 

Phosphoric  Acid 

0 26 

0-35 

0-18 

0-27 

0-27 

Other  Mineral  Matter 

0-36 

0-39 

0-20 

0-29 

1 

0 23 

Total  Dried  Solids 

100-00 

85-18 

100-00 

85-88 

100-00 

85-40 

100-00 

85-00 

100-00 

86-80 

Proteins,  per  cent,  of  Dried 
Solids 

11-82 

12-86 

11-67 

1201 

13-71 

Total  Ash 

0-62 

0-74 

0-38 

0-56 

0 50 

Energy  in  Calories  . . . . 

1 

3524 

356  2 

352-9 

352  3 

359-8 

i 

All  the  flours  were  baked  into  bread  in  the  ordinary  manner,  flour,  yeast, 
salt,  and  water  only  being  used  in  their  manufacture.  Moisture  was  deter- 
mined on  the  bread,  which  was  then  subjected  to  an  artificial  digestion 


556 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


test  with  the  object  of  ascertaining  the  relative  protein  digestibility  of  the 
various  loaves  The  following  quantities  were  taken  : Bread  50  grams, 
water  60  c.c.  decinormal  hydrochloric  acid  75  c.c.,  in  which  0-3  gram  of 
Armour’s  standard  pepsin  had  been  dissolved  ; this  was  allowed  to  digest 
for  IJ  hours.  Fifteen  c.c.  of  normal  sodium  carbonate,  in  which  0-5  gram 
of  Armour’s  standard  pancreatin  had  been  dissolved,  was  next  added  and 
digestion  allowed  to  proceed  for  a further  1 J hours.  The  tests  on  the  whole 
of  the  breads  were  carried  out  simultaneously,  the  flasks  containing  the 
mixtures  being  submerged  in  a Avater-bath  at  slightly  above  body  tempera- 
ture, and  shaken  at  frequent  intervals.  At  the  close  of  the  time,  an  addi- 
tional 100  c.c.  of  water  was  added  to  each,  which  was  shaken  and  Altered. 
Proteins  were  determined  by  the  Kjeldahl  test  in  the  filtrates,  and  the 
following  figures  obtained.  A deduction  has  been  made  for  the  protein 
matters  of  the  digestive  agents  and  the  yeast  employed  for  fermentation. 


Constituents.  ' 

1 

I.  SR.  i 

II.  Std. 

III.  Pint. 

lA^  Bkrs. 

V.  \ Am. 

Moisture 

43-52 

44-12 

43-78 

43-46 

44-28 

Dried  Solids  . . 

56-48 

55-88 

56-22 

56-54 

55-72 

Digested  Proteins,  per  cent,  of  Bread 
Digested  Proteins,  per  cent,  of  Dried 

6-31 

6-09 

6-42 

6-23 

72-8 

Solids 

Digested  Proteins,  per  cent,  of  Total 

11-17 

10-89 

11-43 

11-02 

13-06 

Proteins  present  . . 

94  50 

84-68 

97-90 

91-75 

95-25 

Looking  first  at  the  results  of  flour  analyses  and  comparing  the  straight- 
run,  No.  I.,  and  standard,  No.  II.,  flours,  the  latter  is  considerably  richer 
in  protein  ; but  on  turning  to  the  results  of  digestion  experiments,  the  100 
parts  of  straight-run  bread  yield  6*31  parts  of  digested  protein,  whereas 
the  standard  yields  only  6-09  parts.  It  follows  that  as  a source  of  available 
protein,  70  per  cent,  straight-run  flour  makes  a more  nutritious  bread  than 
does  the  proposed  80  per  cent,  standard.  Under  the  conditions  of  the 
experiment,  with  straight-run  flour,  94-5  per  cent,  of  the  total  protein 
present  is  digested  ; whereas  of  that  of  standard  bread,  only  84-68  per 
cent,  is  digested.  In  view  of  the  oft-repeated  assertion  that  millers’  white 
flours  and  bakers’  white  breads  are  practically  only  starch,  it  is  of  interest 
to  compare  the  patents,  straight-run  and  bakers’  flours  from  the  same  wheat. 
With  a 70  per  cent,  straight-run  the  proteins  amount  to  10-09  ; with  a 
high  class  patent  of  the  most  delicate  and  creamy  Avhite  tint,  the  protein 
is  9-97  per  cent.  ; while  the  corresponding  bakers’  grade  contains  10-21 
per  cent,  of  proteins.  Substantially,  therefore,  the  whole  three  grades  are 
alike  in  protein  composition.  But  on  turning  to  the  digestion  tests,  the 
absolute  amount  of  digested  protein  is  higher  for  the  patent  flour  bread, 
6-42  per  cent.,  than  for  either  of  the  others.  This  is  due  to  its  very  great 
digestibility,  as  97-9  per  cent,  of  the  total  proteins  have  been  digested  as 
against  84-68  per  cent,  in  the  case  of  the  standard  bread.  So  far  from  the 
white  bread  being  of  inferior  nourishing  qualities,  the  patent  flour  yields 
more  protein  nourishment  than  the  standard  flour  from  the  same  wheat. 
But  as  already  remarked,  the  baker  would  regard  all  these  English  flours  as 
too  Aveak  for  his  j)urpose,  and  insists  on  a liberal  admixture  of  flour  from 
foreign  Avheats.  Number  V.,  AA'hich  is  composed  of  half  English  straight-run 
and  half  strong  American  patent,  is  much  nearer  what  a baker  Avould  actu- 
ally use  in  practice.  This  flour,  though  a very  Avhite  flour,  contains  con- 
siderably more  protein  than  the  standard,  11-90  against  11-05  per  cent. 


THE  NUTRITIVE  VALUE  OF  BREAD. 


557 


But  when  subjected  to  a digestion  test,  the  amount  of  protein  digested 
is  7*28  against  6-09  per  cent,  with  the  standard  bread.  The  difference  is 
partly  due  to  the  larger  amount  of  protein  present,  and  partly  to  its  greater 
digestibility,  95-25  per  cent,  of  the  total  being  digested  as  against  84-68 
per  cent. 

The  question  may  very  fairly  be  raised  as  to  how  these  artificial  digestion 
tests  compare  vith  the  normal  process  of  human  digestion.  Hutchison 
regards  Rubner’s  experiments  on  this  point  as  being  most  conclusive.  Rub- 
ner  finds  on  tests  with  human  subjects  that  with  the  finest  white  flour  some 
20  per  cent,  of  the  proteins  are  lost  in  digestion,  with  larger  amounts  in 
darker  flours  and  whole-meal.  In  the  authors’  experiments  the  digestion 
was  carried  considerably  farther  than  this,  as  with  the  patent  flour  tests 
a loss  of  only  2-1  per  cent,  was  experienced.  These  experiments  were 
therefore  too  effective  when  compared  with  human  digestion.  But  as  a 
consequence  of  over-digestion  there  is  a general  levelling-up  of  the  less 
digestible  substances  ; and  therefore  in  the  comparative  tests  recorded,  the 
more  difficultly  digestible  breads  show  up  more  favourably  than  they  would 
do  in  experiments  on  the  human  subject. 

A number  of  other  similar  tests  have  been  made  wdth  straight-run  flours 
and  80  per  cent,  standard  flours  from  other  wheats  and  wheat  mixtures; 
but  in  every  case  the  comparative  results  both  in  nutritive  value  and  digesti- 
bility have  been  the  same.  In  one  case  tests  were  made  on  the  breads, 
not  only  when  new,  but  also  when  one  day  old.  Both  breads  were  less 
digestible  on  the  second  day,  and  gave  83-6  per  cent,  of  digested  proteins 
with  the  straight-run,  and  78-9  per  cent,  with  the  standard  bread.  This 
is  borne  out  in  a remarkable  manner  by  the  fact  that  standard  bread,  in 
common  with  whole-meal  breads,  is  commercially  unsaleable  when  one 
day  old. 

No  direct  estimations  of  carbohydrate  digestion  were  made  on  these 
breads,  because  in  all  cases  of  flours,  as  excluding  whole-meal,  the  carbo- 
hydrates are  almost  completely  absorbed.  But  according  to  Rubner, 
what  difference  there  is  is  in  favour  of  the  patent  flour. 

In  the  case  of  fats,  Rubner  states  that  with  patent  flour  44-7  per  cent, 
is  lost  in  human  digestion,  and  as  much  as  62-8  in  seconds  flour.  There 
being  so  little  fat  in  either  of  the  two  flours,  the  difference  is  very  small, 
and  both  flours  may  be  regarded  as  yielding  practically  the  same  amount 
of  digestible  fat  nutriment. 

Taking  proteins,  carbohydrates  and  fat  as  a whole,  the  straight-run 
flour  is  of  higher  nutritive  value  in  digestible  materials  than  is  the  proposed 
standard. 

In  the  matter  of  mineral  constituents,  the  straight-run  flour  contained 
0-26  per  cent,  of  phosphoric  acid  as  against  0-35  per  cent,  in  standard  flour. 
No  determinations  of  either  iron  or  lime  were  made  on  either  of  these  flours  ; 
but  another  pair  of  similar  flours,  in  each  case  from  the  same  wheat,  gave 
the  following  results  : — 

straight-run  Standard 
Flour.  Flour. 

Iron  Oxide,  per  cent.  . . . . . . 0-002  0-004 

L ine,  per  cent.  ..  ..  ..  ..  0-026  0-040 

Again  citing  Rubner,  the  loss  of  mineral  matter  in  human  digestion 
amounts  to  19-3  per  cent,  in  the  case  of  patent,  and  30-3  per  cent,  in  the 
case  of  seconds  flour.  In  view  of  the  fact  that  both  these  flours  are  finely 
ground,  the  authors  are  of  opinion  that  in  an  acid  medium  such  as  gastric 
juice,  most  if  not  all  of  the  phosphates  of  iron  and  calcium  are  rendered  soluble. 
Such  at  least  was  the  case  in  the  artificial  digestion  tests  made  by  them  on 
the  flours  just  referred  to.  They  therefore  regard  all  such  salts  in  both 


558 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


instances  as  being  available  for  assimilation  by  the  human  body  should  it 
require  it.  In  paragraph  648,  the  question  of  mineral  nutritive  value  of 
bread  has  been  already  fully  discussed  : it  is  there  pointed  out  on  the 
authority  of  Hutchison  that  no  diseased  condition  can  be  clearly  traced  to 
a deficiency  of  any  of  the  mineral  ingredients  of  the  diet,  with  the  exception 
of  iron,  and  possibly  also  of  calcium.  The  question  of  the  comparative 
food  value  of  organic  and  inorganic  mineral  compounds  is  also  there  dis- 
cussed. In  the  case  of  lime,  the  total  quantity  from  the  food  standpoint 
is  negligible  in  both  varieties  of  bread.  The  difference  between  the  two 
is  0-014  per  cent,  in  favour  of  the  standard  flour.  It  may  be  instructive 
to  see  what  these  quantities  actually  mean.  Assuming  1 lb.  of  bread  per 
day  to  be  the  food  ration  of  a man,  then  the  lb.  of  straight-run  bread  gives 
him  from  the  flour  1-19  grains  of  lime,  while  the  standard  bread  will  give 
him  1-68  grains  of  lime,  or  a difference  of  0-49  grain  in  favour  of  the  latter. 
Taking  a medium  hard  water  containing  30  grains  of  lime  salts  per  gallon, 
the  amount  of  0-49  grain  of  lime  would  be  yielded  by  about  5 oz.  or  half  a 
tumbler  of  such  water. 

There  is  another  aspect  of  the  case  which  deserves  examination.  Hop- 
kins of  Cambridge  has  made  the  following  public  statement  : — 

“ From  my  own  experiments  on  young  rapidly  developing  animals  I 
am  convinced  that  if  one  group  of  children  could  be  kept  for  a fortnight 
on  a dietary  two -thirds  of  which  was  made  up  of  80  per  cent,  standard 
bread,  and  a second  similar  group  was  kept  on  the  same  food  proportion 
of  the  superfine  white  bread,  the  first  group  would  show  unmistakable 
and  most  conclusive  signs  of  the  better  tissue-building  qualities  of  the 
standard  bread.  The  actual  amounts  of  pure  proteins,  starches,  fats, 
sugars,  and  salts  in  a food  are  not,  when  considered  alone,  a sufficient  criterion 
of  the  amount  of  building  material  a person  can  assimilate  from  it  ; so  the 
fact  that  the  80  per  cent,  flour  retains  more  of  the  natural  food  elements 
of  the  grain  does  not  prove  that  the  body  can  make  efficient  use  of  them 
all.  I do  not,  however,  refer  to  the  question  of  mere  digestibility.  The 
superior  value  of  the  80  per  cent,  flour,  in  my  opinion,  lies  in  the  fact  that 
in  such  flour  there  are  retained  certain  at  present  unrecognised  food  sub- 
stances, perhaps  in  very  minute  quantities,  whose  presence  allows  our 
systems  to  make  full  use  of  the  tissue- building  elements  of  the  grain.  These 
substances  of  undetermined  nature  are  apparently  removed  to  a great 
extent  from  the  fine  white  flour  in  the  milling.  Curiously  enough,  I began 
long  ago  a series  of  experiments  on  the  relative  tissue  building  values  of 
fine  white  flour  and  of  flours  which,  like  the  80  per  cent,  flour,  contain 
a larger  proportion  of  the  whole  grain.  These  experiments  were  made, 
among  others,  in  the  endeavour  to  discover  the  nature  of  the  unknown 
substances  which  I have  just  mentioned.  In  their  existence  I believe 
greatly,  because  of  my  experimental  results.  Unfortunately  I am  not 
vSufflciently  advanced  to  publish  any  concrete  conclusions,  but  I may  say 
that  all  my  work  to  date  confirms  my  belief  in  the  superior  food  value  of 
what  is  termed  standard  bread.  After  definitely  proving  that  young  animals 
grow'  with  very  much  greater  rapidity  on  browm  flour  than  on  white  flour, 
I have  been  able  to  improve  the  tissue-building  rate  of  the  white  flour 
subjects  by  adding  to  their  w'hite  flour  an  extract  made  from  the  brow  n 
flour.  This  suggests  not  so  much  that  the  80  per  cent,  flour  contains  more 
])roteins,  iron,  phosphorus,  etc.,  used  in  building  up  tissues,  but  that  it  con- 
tains more  of  certain  as  yet  little  studied  substances  which  allow  us  to 
make  better  use  of  the  various  ingredients  of  the  wheat  berry.  To  make 
the  best  use  of  any  food  material,  such  as  proteins,  etc.,  certain  other  food 
substances,  and  possibly  a variety  of  tliem,  must  also  be  present  in  definite 
proportions.  If  one  essential  food  constituent  which  ought  to  make  up. 


THE  NUTRITIVE  VALUE  OE  BREAD. 


559 


say,  even  as  little  as  1 per  cent,  of  the  total  food  is  present  in  only  half  its  nor- 
mal amount,  then  when  it  is  a case  of  building  up  the  tissues  the  system  will 
only  be  able  to  make  use  of  half  of  the  other  food  elements,  even  if  these 
other  elements  make  up  the  main  bulk  of  the  food.  . . . Returning  to  our 
bread,  the  substances  of  unknown  nature  which  I just  now  mentioned  may 
need  to  be  present  in  very  small  amounts,  but  if  the  necessary  minimum  is 
not  available  the  utilisation,  in  tissue  growth  or  repair,  of  all  other  constitu- 
ents is  infallibly  deficient.  In  the  process  of  converting  the  wheat  grain 
to  the  fine  wLite  flour  these  unknown  elements  apparently  are  lost  or  de- 
stroyed to  a great  extent.  It  follows  that  no  matter  how  much  iron,  plios- 
phorus,  protein,  etc.,  may  be  retained  in  the  white  flour,  our  systems  cannot 
make  the  best  use  of  them.  Probably  because  it  is  much  less  tampered 
with  or  disturbed  in  the  milling,  the  80  per  cent,  flour  retains  the  various 
food  elements  of  the  grain  in  a much  more  natural  combination.  This  alone 
is  sufficient  to  account  for  the  greater  use  our  systems  can  make  of  the  build- 
ing materials  retained  in  the  standard  flour.'’ 

According  to  this  view,  the  white  bread  may  contain  more  digestible 
protein,  fat,  and  carbohydrates  than  the  standard  bread,  and  yet  the  latter 
may  be  the  more  valuable  article  of  food.  The  theory  is  advanced  that 
standard  flour  contains  certain  at  present  unrecognised  food  substances,  per- 
haps in  very  minute  quantities,  which  may  confer  superior  food  value  on  the 
standard  bread.  Because  these  substances  of  unknown  nature  are  appar- 
ently lost  or  destroyed  in  the  manufacture  of  white  flour,  and  are  probably 
less  tampered  with  in  milling  80  per  cent,  flour,  Hopkins  regards  the  latter 
as  a much  more  natural  combination.  Underlying  all  such  hypotheses,  there 
seems  to  be  the  belief  that  the  wheat  grain  is  specially  designed  by  nature 
as  a food  for  man.  One  readily  understands  that  milk  is  thus  intended  for 
food  and  only  for  food,  and  that  by  removing  any  one  part,  which  removal 
may  be  considered  harmless,  the  whole  balance  of  nutritive  value  may  be 
upset,  because  some  unknowm  but  nevertheless  most  important  constitu- 
ent has  been  taken  away,  which  Nature  introduced  for  a special  purpose. 
But  the  natural  function  of  the  wheat  grain  is  the  reproduction  of  the  plant. 
The  germ  is  the  future  plant,  the  endosperm  is  intended  as  its  food  during 
the  earlier  stages  of  germination,  and  the  bran  is  simply  the  protective 
coating.  From  the  point  of  view  of  plant  life  the  endosperm  or  white 
flour  portion  is  the  only  part  that  is  intended  for  food.  Both  the  germ 
and  the  inner  surface  of  the  bran  contain  active  enzymes  whose  function 
it  is  to  exercise  a digestive  action  on  the  endosperm  for  the  benefit  of  the 
young  and  growing  embryo.  It  is  now  universally  conceded  that  the  whole 
grain  is  not  so  well  adapted  for  human  food  as  certain  portions  thereof. 
But  once  admit  the  principle  of  selection,  and  it  is  difficult  to  see  why  it  is 
less  natural  to  select  those  portions  of  the  grain  which  constitute  a 70  per 
cent,  white  flour,  than  those  which  yield  an  80  per  cent,  standard  flour, 
especially  when  the  former  contains  a higher  proportion  of  the  hitherto 
recognised  food  constituents  in  the  digestible  form.  Hopkins  has  so  far 
been  unable  to  discover  the  nature  of  these  unknown  substances,  and 
unfortunately  cannot  publish  any  concrete  conclusions.  His  general 
opinion  is  based  on  feeding  experiments  with  young  animals  which  grow 
with  much  greater  rapidity  on  brown  flour  than  on  white  flour.  It  is  sub- 
mitted by  the  authors  that  the  similarity  between  the  digestive  systems 
of  young  animals  and  children  is  not  sufficiently  great  to  enable  any  very 
positive  conclusions  to  be  drawn  in  the  one  case  from  observations  made 
in  the  other.  There  are  most  valuable  animal  food-stuffs  that  would  be 
absolutely  unfitted  for  the  diet  of  children.  With  regard  to  the  proposed 
fortnight's  experimental  dietary  on  children,  the  author's  opportunities  of 
observation  have  been  comparatively  limited.  But  so  far  as  they  go,  they 


5G0 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


have  not  been  confirmatory  of  the  opinion  advanced.  In  such  cases, 
the  children  have  bitterly  complained  of  the  less  palatable  nature  of  their- 
bread,  have  eaten  less  of  it,  and  have  begged  to  be  allowed  again  to  have 
white  bread.  On  the  change  being  made,  their  bread  was  eaten  with 
keener  relish  and  more  of  it,  with  an  improvement  in  the  children's  general 
spirits.  In  any  reasonable  children's  dietary  the  authors  have  the  gravest 
doubts  as  to  the  superiority  of  standard  bread  such  as  No.  II.  in  the  pre- 
ceding table  with  its  6-09  per  cent,  of  digestible  protein  as  against  the 
baker's  white  bread  No.  V.  with  its  7*28  per  cent,  of  protein  in  its  digestible 
form.  Turning  from  children  to  grown  men,  they  express  in  no  uncertain 
tone  their  preference  for  white  bread.  From  the  navvies  referred  to  by 
Lawes  and  Gilbert,  paragraph  653,  to  the  colliers  of  Durham  and  men  of 
the  navy  of  the  present  day,  these  disciples  of  hard  work  all  find  white 
bread  a better  and  more  sustaining  food  than  the  browner  varieties. 

But  assuming  for  the  moment  that  Hopkins  has  established  his  case, 
that  he  has  identified  his  unknown  food  substances,  and  demonstrated  their 
high  nutritive  value,  there  yet  remains  “ a more  excellent  way  " to  obtain 
these  advantages  than  by  the  use  of  standard  flour.  In  the  experiments 
before  cited,  a straight-run  flour  of  70  per  cent,  has  been  taken,  and  this 
with  another  10  per  cent,  of  the  wheat  composed  of  the  germ  and  finest 
offal  makes  up  the  standard  flour.  If  the  straight-run  flour  is  split  up  into 
patents  and  bakers'  grade,  then  the  latter  only  may  be  mixed  with  the  same 
10  per  cent,  of  germ  and  offal,  and  a flour  almost  identical  with  the  standard 
is  produced.  For  convenience  in  description,  the  resultant  flour  may  be 
called  “ Improved  Standard,"  and  is  slightly  the  darker,  because  of  the  with- 
drawal of  the  patent  flour  ; in  addition,  the  10  per  cent,  of  germ  and  offal 
w'hich  constitute  12-5  per  cent,  of  the  whole  standard  flour  will  be  a larger 
percentage  of  the  improved  flour.  This  allocation  of  the  flour  in  milling 
w ill  permit  the  individual  who  believes  in  the  superiority  of  white  flour  to 
still  satisfy  his  requirements,  while  the  advocate  of  the  darker  flour  wall 
also  have  his  tastes  gratified.  Whatever  unknown  food  substances  are 
contained  in  this  last  10  per  cent,  of  germ  and  offal  run  into  the  flour,  they 
will  be  present  wuth  all  their  advantages  and  in  a more  concentrated  form 
in  the  improved  standard  flour  prepared  in  this  manner.  This  improved 
flour  has  another  great  recommendation,  and  that  is  that  it  can  be  produced 
and  sold  at  2s.  6d.  per  sack  less  at  present  prices  than  the  80  per  cent, 
standard.  In  the  case  of  the  extremely  poor,  this  greater  cheapness  is  a 
very  material  advantage.  The  authors  have  made  analyses  of  70  per  cent, 
straight-run,  80  per  cent,  standard,  and  improved  standard,  all  obtained 


from  the  same  wiieat.  The  following  are 

the  results 

straight- 

run. 

80  per  cent. 
Standard. 

Improved 

Standard. 

Proteins 

10-72 

11-50 

12-64 

Carbohydrates 

75-02 

74-13 

72-78 

Fat  . . 

1-06 

1-46 

1-75 

Pliosphoric  Acid  . . 

0-21 

0-31 

0-39 

In  the  important  constituents  proteins,  fat,  and  phosphoric  acid,  the' 
improved  standard  is  about  as  much  better  than  the  80  per  cent,  standard 
as  that  in  turn  is  better  than  the  straight-run.  On  making  these  into  bread, 
the  80  per  cent,  standard  and  improved  standard  were  scarcely  distinguish- 
able in  appearance,  they  were  nearly  exactly  alike.  On  being  subjected  to 
the  practical  test  of  the  breakfast  table,  the  breads  on  comparison  could  not 
be  distinguished  from  each  other,  and  no  preference  was  expressed  for  the 
flavour  of  either  variety.  Digestion  tests  of  the  same  kind  as  before  were 
made  with  these  breads,  in  which  the  following  results  w^ere  obtained  : — - 


THE  NUTRITIVE  VALUE  OE  BREAD. 


561 


Straight-  80  per  cent.  Improved 
run.  Standard.  Standard. 

Digested  Proteins  per  cent,  of  bread  6-58  6-37  6-86 

Digested  Proteins  per  cent,  of  Total 

Proteins  present..  ..  ..  95-2  93*5  91-1 

The  degree  of  digestibility  diminished  steadily  under  the  conditions  of 
the  tests  as  the  white  flour  was  departed  from,  being  95-2  in  the  white, 
93*5  in  the  80  per  cent,  standard,  and  91 T per  cent,  of  the  total  protein 
present  in  the  improved  standard.  In  the  case  of  the  latter,  however, 
the  greater  quantity  of  protein  present  rather  more  than  compensates  for 
its  diminished  digestibility,  and  a larger  total  was  afforded  by  this  flour. 
So  far  as  the  unknown  substances  of  possibly  high  nutritive  value,  which 
may  be  contained  in  the  added  offal,  are  concerned,  they  must  obviously 
be  just  as  available  in  the  improved  standard  as  in  the  80  per  cent,  standard, 
the  only  difference  being  that  the  quantity  is  proportionately  greater. 

657.  Standard  Bread,  Snyder. — The  authors  forwarded  the  Standard 
Bread  Manifesto,  together  with  copies  of  the  press  arguments  in  favour  of 
same,  to  Snyder,  whose  classic  investigations  of  the  digestibility  and  nutri- 
tive value  of  bread  by  human  subjects  have  been  so  extensively  quoted 
from  in  paragraph  647.  They  have  received  the  following  expression  of 
opinion  in  reply  : — 

“I  have  read  with  interest  your  letter  of  recent  date  on  the  subject 
of  Standard  Bread.  To  make  Standard  Bread  requires  standard  flour,  and 
this  in  turn  necessitates  standard  wheat.  Unfortunately  nature  does  not 
make  such  a wheat — she  produces  wheat  with  proteins  ranging  from  8 to 
16  per  cent,  or  more.  Now  it  is  quite  evident  that  a so-called  standard 
loaf  from  a flour  of  low  protein  would  have  less  of  this  nutrient  than  a high 
patent  milled  from  wheat  rich  in  protein.  There  is  no  definite  basis  upon 
which  a standard  can  rest — that  is  a standard  as  the  term  is  used  in  science. 

To  make  a so-called  80  per  cent,  flour  would  necessitate  including  in  the 
flour  a portion  of  the  wheat  offals  ; and  the  principle  has  been  well  estab- 
lished that  any  addition  of  any  such  materials  results  in  a decrease  in  the 
digestibility  of  the  product  as  a whole.  I am  using  the  term  “ 80  per  cent, 
flour  ” not  in  its  ordinary  sense,  but  as  it  is  used  in  the  article  sent  me — 
all  of  the  flour  of  the  wheat  kernel,  and  5 to  10  per  cent,  of  wheat  oflal 
finely  ground  and  admixed  with  the  flour. 

I think  there  is  much  misconception  as  to  the  amount  of  germ  in  wheat  ; 
it  constitutes  about  7 per  cent,  of  the  ofjals  and  not  of  the  entire  herry,  making 
only  about  1 -7  per  cent,  of  the  entire  constituents  of  wheat.  If  it  is  desired 
to  secure  flours  with  more  protein,  this  is  possible  by  the  more  liberal  use 
of  the  clears  which  contain  even  more  than  the  proposed  standard.  The 
result  of  any  considerable  amount  of  clears  on  the  quality  of  the  bread 
product  is  well-known — an  inferior  loaf . Hence  the  “ standard  flour  ” con- 
taining not  only  clear  stock  but  offal  also  would  necessarily  still  further 
lower  the  quality  of  the  bread. 

I am  satisfied  that  it  is  not  feasible  from  a milling  point  of  view  to  include 
in  the  flour  the  offal  or  any  part,  no  matter  how  finely  ground  ; that  it  results 
in  a poorer  quality  of  bread  physically,  and  lowers  the  total  digestibility  of 
the  bread. 

I cannot  see  where  there  is  anything  gained  by  the  addition  of  any  of 
the  wheat  offals  to  flour  ; the  flour  and  the  offal  should  be  kept  distinct.  The 
germ,  although  comparatively  rich  in  protein,  is  very  fermentable  in  char- 
acter, and  it  imparts  to  flour  an  antagonistic  action  to  yeast.  It  is  difficult 
to  get  the  pure  germ  without  admixture  with  other  offal. 

The  whole  art  of  milhnghashadfor  its  object  the  elimination  of  offal,  and 
this  has  been  strictly  in  accordance  with  scientific  principles,  and  has  resulted 
in  the  production  of  flour  from  which  better  bread  can  be  made  and  also 
bread  of  higher  nutritive  value."’  [Personal  February,  1911.) 

o o 


CHAPTER  XXII. 


THE  WEIGHING  OF  BREAD. 

658.  The  Baker’s  Position. — The  baker’s  attitude  toward  the  weighing 
of  bread  is  partly  governed  by  the  exigencies  of  its  manufacture,  and  partly 
by  the  various  sanctions  imposed  upon  him  by  law.  There  are,  moreover, 
scientific  reasons  which  bear  on  the  whole  question.  The  authors  there- 
fore feel  justified  in  acceding  to  a somewhat  general  request  to  include 
this  subject  in  the  present  work.  The  obligation  to  weigh  bread  has  been 
imposed  by  law,  and  therefore  the  most  convenient  way  of  dealing  with 
it  will  be  to  follow  the  chronological  development  of  the  laws  relating  to  the 
weight  of  bread.  A great  deal  of  the  substance  of  this  chapter  has  already 
appeared  in  a series  of  articles  contributed  by  one  of  the  authors  to  The 
British  Baker. 

659.  Act  of  31  George  II.,  c.  29,  1757. — The  investigation  of  the  Bread 
Laws  requires  some  starting  point  to  be  taken,  and  for  that  purpose  the 
Act  now  referred  to  may  be  selected.  The  title  of  the  Act  is  “ An  Act  for 
the  due  making  of  Bread  ; and  to  regulate  the  Price  and  Assize  thereof  ; 
and  to  punish  Persons  who  shall  adulterate  Meal,  Flour  or  Bread.”  This 
is  not,  however,  the  earliest  recorded  Bread  legislation,  for  the  opening 
sentence  of  the  Act  is  “ WHEREAS  by  an  Act  of  Parliament  made  in  the 
one  and  fiftieth  year  of  the  Reign  of  King  Henry  the  Third,  entitled  Assisa 
Panis  (&;  Cervisiae,  Provision  was  made  among  other  Things,  for  setting  the 
Assize  of  Bread.”  This  Act  was  variously  amended,  but  the  principle  of 
an  Assize  was  continued  down  through  a series  of  Acts  until  this  Public 
Act  of  the  thirty -first  year  of  the  reign  of  George  II.,  which  was  largely  a 
consolidating  Act  passed  in  order  “ to  reduce  into  one  Act  the  several  Laws 
now  in  Force  relating  to  the  due  making,  and  to  the  Price  and  Assize  of 
Bread.” 

660.  Assize  of  Bread. — Whatever  the  original  meaning  of  the  word 
‘‘  Assize  ” it  had  come  at  the  time  of  this  Act  to  signify  in  this  relationship 
an  ordinance  determining  from  the  price  per  bushel  of  wheat  the  weight 
at  which  loaves  to  be  sold  at  certain  fixed  prices  were  to  be  made. 

661.  Price  of  Bread. — This,  like  the  Assize,  consisted  of  a sliding  scale. 
With  various  prices  for  the  Winchester  bushel  of  wheat,  the  price  at  which 
tlie  Peck,  Half  Peck,  and  Quartern  loaves  were  to  be  sold  was  fixed. 

662.  Setting  an  Assize. — In  order  that  “ a plain  and  constant  Rule  and 
Method  might  be  duly  observed  and  kept  in  the  making  and  assizing  of  the 
several  Sorts  of  Bread,”  it  was  provided  that  the  Court  or  person  or  persons 
authorised  by  the  Act  to  set  the  Assize  of  Bread  should  have  respect  to  the 
j)rice  at  which  the  Grain,  Meal,  or  Flour  whereof  such  Bread  should  be 
made,  “ shall  bear  in  the  publick  Market  ” in  or  near  the  place  for  which 
any  such  Assize  of  Bread  shall  be  set.  They  were  also  required  “ from 
Time  to  Time,  to  make  reasonable  Allowance  to  the  Makers  of  Bread  for 
Sale,  for  their  Charges,  Labour,  Pains,  Livelihood  and  Profit,  as  such  Cour 

562 


THE  WEIGHING  OF  BREAD. 


563 


shall  from  Time  to  Time  deem  proper/'  The  bakers  were  also  prohibited 
from  making  for  Sale  any  sort  of  Bread  “ except  Wheaten  and  Household, 
otherwise  brown  Bread,"  and  such  other  sorts  of  bread  as  were  specially 
permitted.  By  the  above  definition,  Wheaten  bread  apparently  meant 
white  bread,  while  Household  bread  was  brown  bread. 

663.  Table  of  Assize  and  Price  of  Bread  made  of  Wheat. — For  the  guid- 
ance of  the  Court  of  Assize,  two  tables  were  set  out.  The  first  is  the  Assize 
Table.  This  gives  first  of  all  the  price  of  the  bushel  of  Avheat,  Winchester 
measure.  This  was  taken  from  the  public  market  price  ; to  this  the  Court 
added  the  sum  which  the  Court  held  to  be  an  adequate  recompense  to  the 
baker  for  baking.  Two  examples  are  given — “ If  the  Price  of  Wheat  in 
the  Market  is  5s.  the  Bushel,  and  the  Magistrates  allow  Is.  6d.  the  Bushel 
to  the  Baker  for  Baldng,  find  6s.  6d.  in  Column  No.  I,  and  even  therewith 
under  No.  II  will  be  found  the  Weights  of  the  several  loaves  ; but  if  the 
Price  in  the  Market  is  3s.  and  the  allowance  Is.,  then  the  Weight  of  the 
said  Loaves  will  be  found  even  with  4^."  Further  directions  are  given 
in  a note,  that  the  wheaten  loaves  are  at  all  times  to  weigh  three-fourths 
of  the  weight  of  the  Household  Loaves.  The  weight  of  the  loaves  is  through- 
out in  exact  inverse  proportion  to  the  figure  obtained  by  adding  together 
the  price  of  wheat  and  the  baker's  allowance  for  making.  So,  too,  the 
weight  of  the  larger  loaves  is  in  direct  proportion  to  the  price.  The  follow- 
ing is  the  line  of  weights  for  the  price  of  6^.  6d.  per  bushel  : — 

Assize  Bread. 

Weight. 

Wheaten.  Household. 


Price. 

The  Penny  Loaf 

lbs. 

ozs. 

9 

drams. 

4 

lbs. 

ozs. 

12 

drams. 

10 

The  Twopenny  Loaf 

I 

2 

9 

1 

9 

4 

The  Sixpenny  Loaf 

3 

7 

10 

4 

11 

13 

Twelvepenny  Loaf 

6 

15 

4 

..  9 

7 

11 

Eighteenpenny  Loaf 

10 

6 

13 

. . 14 

3 

8 

The  Price  Table  gives  as  before  the  price  of  wheat  added  on  to  the  Baker's 
Allowance,  the  latter  being  fixed  in  each  case  by  the  Court.  Then  the 
prices  to  be  charged  for  the  Peck,  Half  Peck,  and  Quartern  loaves  are  given. 
The  Magistrates  and  Justices  are  also  directed  “ to  take  Notice,  that  the 
Peck  Loaf  of  each  Sort  of  Bread  is  to  weigh,  when  well  baken,  17  lbs. 
6 ounces  Averdupois,  and  the  rest  in  Proportion  ; and  that  every  Sack  of 
Meal  or  Flour  is  to  weigh  2 cwt.  2 qrs.  nett  ; and  that  from  every  Sack 
of  Meal  or  Flour  there  ought  to  be  produced  on  the  Average,  20  such  Peck 
Loaves  of  Bread."  It  will  be  seen  from  this  that  the  sack  of  flour  is  estimated 
to  yield  347 J lbs.  of  bread,  which  would  amount  to  86  quarterns  of  the 
modern  weight  of  4 lbs.,  with  a piece  3 Jibs.  over.  Another  point  of  interest 
in  passing  is  that  the  old  peck  loaf  was  a twentieth  of  the  average  yield  of 
a^sack,  making  the  quartern  the  eightieth  part  of  such  average  yield,  and 
weighing  4 lbs.  5J  ozs.  The  following  is  the  line  of  bread  prices,  with  wheat 
and  allowance  taken  at  6^.  6d.  per  bushel  : — 


Priced  Bread. 

Price. 


Wheat. n. 

s.  d. 

Household. 

s.  d. 

Quartern  Loaf 

. . 0 

0 

5^ 

Half-peck  Loaf 

. . 1 

3 

0 

11 

Peck  Loaf 

. . 2 

6 

1 

10 

The  Household,  otherwise  Brown,  bread  runs  throughout  at  roughly 


564 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

three-quarters  of  the  price  of  white  or  wheaten  bread.  Evidently  at  this 
time  brown  breads  were  not  regarded  as  being  an  article  of  luxury  and 
meriting  a higher  price.  It  was  simply  the  commonest  household  type, 
and  was  directed  to  be  sold  at  the  lowest  figure. 

The  Act  proceeds  further  to  set  out  the  machinery  by  which  the  Assize 
is  to  be  set  and  enforced.  Thus  returns  are  to  be  made  weekly  of  the  public 
prices  of  wheat,  and  the  assize  and  prices  are  to  be  then  fixed.  In  London, 
before  any  advance  or  reduction  is  made,  a copy  of  the  wheat  price  returns 
is  to  be  left  at  the  Bakers’  Hall.  In  other  places  the  bakers  may  see  such 
returns  at  seasonable  times  at  the  place  where  they  are  kept.  Then  the 
assize  is  published  in  due  form.  First  the  date  and  place  are  set  forth,  and, 
then  it  is  ordered— “ And  in  Places  where  Penny,  Twopenny,  Sixpenny, 
Twelvepenny,  and  Eighteenpenny  Loaves  shall  be  made,  as  followeth  ; the 
Penny  Loaf  Wheaten  is  to  weigh  .... 

[And  so  on  for  the  whole  of  the  prices.] 

And  in  Places  where  Quartern,  Half  Peck,  and  Peck  Loaves  shall  be  made, 
then  as  follows  : 

The  Peck  Loaf  Wheaten  is  to  weigh  ....  and  is  to  be  sold  for  — s.  — d. 
Ditto  Household  is  to  weigh,  etc.” 

A further  provision  was  made  in  the  Act  whereby  the  baker  has  to  make 
his  election  between  making  Assize  or  Priced  Bread,  as  he  could  not  at  the 
same  time  make  and  sell  the  two  denominations.  The  wording  of  the 
section  ran  : — 

I “ And  be  it  also  enacted.  That  in  Places  where  any  six  Penny,  twelve 

Penny,  and  eighteen  Penny  Loaves  shall  at  any  time  be  ordered  or 
allowed  to  be  made  or  sold.  No  Peck,  Half  Peck,  or  Quarter  of  a Peck 
Loaves  shall  be  permitted  or  allowed  at  the  same  time  to  be  there 
made  or  sold  ; to  the  intent  that  one  of  those  Sorts  of  Loaves  of  Bread 
may  not  be  sold  designedly,  or  otherwise,  for  the  other  Sort  thereof, 
to  the  Injury  of  unwary  People.” 

The  Act  further  provides  that  bread  is  to  be  always  well  made,  and 
shall  be  free  from  adulteration,  as  set  out  in  the  following  words 

“ The  several  Sorts  of  Bread  . . . shall  always  be  well  made,  . . . 
according  to  the  Goodness  of  the  several  Sorts  of  Meal  or  Flour  whereof 
the  same  ought  to  be  made  ; and  that  no  Allum,  ...  or  any  other 
Mixture  or  Ingredient  whatsoever  (except  only  the  genuine  Meal  or 
Flour  which  ought  to  be  put  therein,  and  common  Salt,  pure  Water, 
Eggs  Milk  Yeast  and  Barm,  or  such  Leaven  as  shall  at  any  Time  be 
allowed  to  be  put  therein  by  the  Court)  . . . shall  be  put  into,  or  m 
any  wise  used  in  making  Dough,  . . or  on  any  other  account,  m the 
Trade  or  Mystery  of  making  Bread,  under  any  Colour  or  Pretence 
whatsoever.” 

]\Iost  drastic  fines  were  provided  for  any  shortage  in  weight  of  bread. 
The  seller  had  to  “ forfeit  and  pay  a Sum  not  exceeding  five  Shillings,  nor 
less  than  one  Shilling,  for  every  Ounce  of  Bread  ” deficiency  m weight. 
And  if  the  deficiency  were  less  than  one  ounce,  then  a minimum  fine  oi 
2s.  6ri.  and  a maximum  fine  of  7^.  U.  was  exacted.  Penalties  were  also 
provided  for  enforcing  the  sale  of  Priced  Bread  at  the  prices  fixed  by  the 

Under  the  working  of  this  Act  the  banker  had  absolutely  no  liberty  in 
the  way  of  fixing  the  prices  or  weights  of  his  bread.  All  was  decided  tor 
him,  and  any  contravention  of  the  regulations  laid  down  for  his  guidance 
was  ])unished  most  severely. 

664.  Acts  Subsequent  to  31  George  II.,  c.  29,  1757.— Almost  immediately 


THE  WEIGHING  OF  BREAD. 


565 


on  the  passing  of  the  Act  of  31  George  II.  amendments  were  discovered  to  be 
necessary,  and  further  regulations  as  to  the  Assize  and  Price  of  Bread  were 
found  in  an  Act  of  the  following  year,  1758.  Following  on  this  were  no  less 
than  eight  other  Acts  further  regulating  the  Assize  of  Bread,  and  in  some 
cases  passed  in  order  to  render  more  effectual  the  Act  of  31  G.  II.  The 
last  of  this  series  was  that  of  48  George  III.,  c.  70,  1808,  the  only  object  of 
which  was  again  to  amend  the  original  George  II.  Act,  and  “ to  regulate  the 
Price  and  Assize  of  Bread.'’  Notwithstanding  all  these  modifications,  the 
Act  of  George  II.  was  evidently  still  unsatisfactory,  for  we  next  come  to 
another  Act,  that  of 

665.  55  G.  III.,  c.  99, 1815. — In  this  Act  it  was  recited  that — 

Whereas  it  is  deemed  expedient  that  the  said  several  recited  [Assize 

of  Bread]  Acts,  so  far  as  the  same  relate  to  the  City  of  London,  . . . 
and  within  Ten  Miles  from  the  Royal  Exchange,  . . . should  be 
repealed  ; and  that  there  shall  no  longer  be  an  Assize  of  Bread,  or  any 
Regulations  respecting  the  Price  of  the  same,  within  the  said  Limits  ; 

. . . there  shall  be  no  longer  any  Assize  of  Bread  within  the  same 
City,  ...  or  any  Regulations  respecting  the  Price  thereof. 

The  right,  never  again  withdrawn,  was  thus  conferred  on  the  Baker  to 
sell  his  bread  at  whatever  price  he  chose. 

The  Act  further  provided  for  consolidating  the  various  Acts  dealing 
with  adulteration  of  Bread.  It  also  enacted  that  the  Peck  Loaf  should 
weigh  17  lbs.  6 ozs.,  the  Quarter  Peck  4 lbs.  5J  ozs.,  the  Half  Quarter  Peck 
2 lbs.  2J  ozs.,  and  every  Pound  Loaf  sixteen  ounces. 

Scales  and  weights  were  to  be  provided  for  weighing  in  the  presence  of 
the  purchaser,  and  an  increased  penalty  not  exceeding  Ten  Shillings  was 
provided  for  every  ounce  deficiency  in  weight.  In  this  Act  a Proviso  is 
found  in  which  French  Bread  appears.  The  following  is  its  wording  : — 
Provided  always,  that  no  Baker  or  Seller  of  Bread  shall  be  liable 
for  any  Deficiency  in  the  Weight  of  any  Bread,  unless  the  same  shall 
be  Weighed,  and  the  Deficiency  of  the  Weight  thereof  ascertained, 
within  Twenty-four  Hours  next  following  the  time  of  the  same  having 
been  baked  ; and  that  nothing  in  this  Act  shall  be  construed  to  extend 
to  or  to  include  such  Bread  as  is  usually  made,  and  sold  under  the 
Denomination  of  French  or  Fancy  Bread  or  Rolls. 

It  should  be  noted  that  sale  by  weight  applied  to  even  the  Pound  Loaf, 
and  that  that  equally  with  the  larger  loaves  came  within  the  penal  clauses 
of  the  Act  dealing  with  short  weight.  Previous  Acts  contain  the  provision 
that  loss  of  weight  of  bread  must  be  ascertained  within  tw'enty-four  hours, 
but  so  far  as  the  authors  have  been  able  to  find  after  searching  a large  num- 
ber of  Bread  Acts,  this  is  the  first  containing  the  Proviso  relating  to  French 
or  Fancy  Bread  and  Rolls.  This  particular  Act  is  one  of  those  classed  as 
Local  and  Personal  Acts  declared  public  and  to  be  judicially  noticed.” 

666.  59  G.  III.,  c.  127,  1819. — This  was  also  a local  and  personal  Act, 
declared  to  be  public  and  to  be  judicially  noticed.  It  was  passed  in  order 
to  alter  and  amend  the  Act  of  55  G.  III.  just  referred  to.  The  principal 
point  of  historic  interest  is  found  in  the  proviso  attached  to  the  section  deal- 
ing with  the  penalty  for  deficiency  in  weight.  Such  proviso  runs  : — 

“ Provided  always  that  no  Baker  or  Seller  of  Bread  shall  be  subjeet 
or  liable  to  any  penalty  for  any  Deficiency  in  the  Weight  of  any  Bread 
sold  or  offered  for  Sale  in  his,  her,  or  their  Shop,  unless  the  same  shall 
have  been  weighed  by  the  Baker  or  Seller  of  such  Bread  at  the  Time 
of  Sale  thereof,  in  the  Presence  of  the  Seller  or  Sellers  and  the  Pur- 
chaser or  Purehasers  thereof  ; but  that  this  Provision  and  Exception 
shall  not  extend  to  or  include  any  Bread  which  shall  be  dehvered  by 


566 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

any  such  Baker  or  Seller  of  Bread  out  of  his,  her,  or  their  Shop,  to  any 
Customer  or  Customers  at  the  House  or  Houses  of  such  Customer  or 
Customers  ; and  that  nothing  in  this  Act  shall  be  construed  to  extend 
to  or  include  such  Bread  as  is  usually  made  and  sold  under  the  Denomin- 
ation of  French  or  Fancy  Bread  or  Rolls/' 

The  earlier  part  of  this  proviso  exempts  the  baker  from  all  penalties 
tor  short  weight  when  the  bread  is  not  weighed  at  the  time  of  sale  in  the 
presence  of  both  seller  and  purchaser.  Consequently,  if  the  purchaser  did 
not  insist  on  the  bread  being  weighed,  and  the  seller,  as  a result,  did  not 
weigh  it,  then  the  baker  was  freed  from  all  liabilities  for  short  weight. 
This  exemption  was,  however,  not  allowed  to  include  delivered  bread,  and 
with  this  the  seller  was  still  under  penalties  for  short  weight.  The  reason 
probably  was  that  when  the  bread  was  delivered  the  purchaser  had  no 
opportunity  of  seeing  it  weighed  in  his  presence  and  also  that  of  the  seller. 
Consequently,  the  buyer  could  not  waive  such  right,  and  the  responsibility 
was  still  cast  on  the  seller  to  see  that  he  gave  full  weight.  The  next  sec- 
tion of  the  Act  provides  that  when  there  is  any  deficiency  m weight,  no  pro- 
ceedings shall  be  taken  unless  the  Bread  complained  of  shall  have  been 
produced  and  weighed  within  twenty-four  hours  after  the  baking  thereof  in 
the  presence  of  the  magistrates.  It  will  be  noticed  that  again  the  exempting 
French  or  Fancy  Bread  clause  appear  in  the  proviso. 

667.  Basis  of  Bread  Legislation.— The  authors  have  for  many  years  been 
interested  in  trying  to  find  out  the  causes  which  impelled  the  Legislature 
to  make  enactments  on  the  sale  of  bread,  and  especially  the  views  which 
were  expressed  on  the  subject  by  members  of  Parliament  during  their 
debates  Newspapers  of  one  or  two  centuries  ago  did  not  give  such  volu- 
minous reports  as  those  that  now  regularly  appear,  and  a search  for  the 
liistory  of  the  proceedings  which  resulted  in  the  passing  of  the  various  Acts 
has  been  long,  tedious,  anfi  not  productive  of  large  quantities  of  infor- 
mation. Among  other  works,  Cohhett’s  Political  Eegister  has  been  care- 
fully examined  for  the  period  covering  the  greatest  activity  in  legislation, 
but  with  no  success.  Although  Cobbett  was  so  keenly  interested  m the 
Corn  Laws,  and  in  other  cognate  questions,  the  matter  of  the  Bread  Acts 
seems  to  have  escaped  him  entirely.  Searching  in  other  directions,  the 
records  of  the  circumstances  which  led  to  the  passing  of  the  Act  of  1815 
have  been  the  most  fruitful  in  throwing  light  on  the  principles  which  have 
governed  the  historical  developments  of  Bread  Legislation. 

668.  Debate  on  Assize  of  Bread,  1815.— On  Tuesday,  April  4,  1815,  Mr. 
Frankland  Lewis  rose  in  his  place  in  the  House  of  Commons  to  move  for 
the  appointment  of  a committee  to  consider  the  existing  laws  with  regard 
to  the  regulation  of  the  Assize  of  Bread,  and  also  whether  it  is  expedient 
or  not  to  have  any  established  assize.  The  lion,  member  observed  that 
when  the  Corn  Bill  was  under  discussion  it  was  repeatedly  asserted  that 
if  the  average  price  of  corn  were  at  805.  a quarter,  the  quartern  loaf  must  be 
at  IfitZ.,  an  assertion  which  was  disproved  again  and  again.  But  it  was  b^ome 
obviously  material  to  inquire  in  order  to  set  the  matter  at  rest.  I here 
were  however,  other  grounds  upon  which  the  inquiry  he  proposed  was 
desiralile.  An  opinion  prevailed  throughout  the  country  that  these  laws 
of  assize  were  rather  productive  of  mischief  than  of  good.  But  yet  these 
laws  had  so  long  existed,  even,  indeed,  since  the  days  of  King  John,  that 
it  would  be  evidently  improper  to  accede  without  previous  inquiry  to  any 
such  measure  as  some  gentlemen  proposed  for  doing  away  with  these  laws 
altogether.  On  this  ground,  then,  he  conceived  a committee  of  inquiry 
ought  to  be  appointed.  He  did  not  wish  to  make  any  perplexing  state- 
ment, but  must  say  a few  words  as  to  the  operation  of  the  assize  system. 


THE  WEIGHING  OF  BREAD. 


567 


It  was  a fact  that  in  places  where  no  assize  was  resorted  to — for  it  was  dis- 
cretionary with  the  magistrates  to  act  upon  the  law  of  assize  or  not — the 
public  were  more  favourably  circumstanced.  For  instance,  in  the  town  of 
Birmingham,  where  the  law  of  assize  was  not  established,  and  where  wheat 
was  at  655.  a quarter,  the  quartern  loaf  was  sold  at  8Jd.  by  a company,  too, 
which  divided  20  per  cent,  upon  their  capital.  He  did  not  mean  to  say  that 
this  bread  was  quite  so  white  as  that  sold  in  London,  but  it  was  of  the 
standard  wheaten  quality.  If,  then,  the  assize  laws  were  really  beneficial 
liow  came  this  difference  ? According  to  the  old  law,  the  assize  of  bread 
was  set  by  the  price  of  wheat,  but  by  a statute,  applicable  to  London  only, 
which  was  enacted  in  1797,  the  assize  was  set  by  the  price  of  flour  ; and  this 
statute,  which  passed  as  a private  Bill,  was  actually  brought  in  upon  the 
petition  of  the  bakers  of  London.  To  this  statute  the  hon.  gentleman 
attributed  the  greater  part,  if  not  the  whole,  of  the  evil  complained  of  in 
the  London  assize.  The  hon.  gentleman  concluded  by  formally  moving 
the  appointment  of  a select  commitee.  After  some  further  remarks  tho 
motion  was  agreed  to,  and  a committee  appointed. 

669.  Report  of  Select  Committee  Appointed,  1815. — The  committee 
just  referred  to  after  appointment  went  rapidly  to  work,  for  on  June  6,  1815,. 
the  House  of  Commons  ordered  to  be  printed  the  “ Report  from  the  Com- 
mittee on  Laws  relating  to  the  manufacture,  sale,  and  assize  of  bread.'" 

Copies  of  this  report  are  at  the  present  time  very  scarce,  but  thanks  ta 
the  Librarian  of  Lincoln's  Inn  Library,  the  authors,  after  wading  through 
vast  masses  of  old  Parliamentary  papers,  have  succeeded  in  unearthing 
a copy,  of  which  the  following  is  a 'precis.  It  cannot  fail  to  appeal  to  those 
interested  in  the  history  of  the  development  of  bread  legislation. 

The  Committee  proceeded  in  pursuance  of  the  orders  of  the  House,  to 
examine  and  compare  the  statute  called  “ Assisa  Panis  et  Cervisise,"  made 
in  the  31st.  year  of  Henry  III.,  with  various  other  ordinances  issued  since 
that  date. 

They  find  that  the  31st  Henry  III.  was  (at  the  petition  of  the  Bakers  of 
Coventry)  an  exemplification  of  certain  ordinances  of  Assize  made  in  the 
reign  of  King  John,  the  purpose  of  which  appears  to  have  been  to  regulate 
the  charges  and  profits  of  Bakers  ; it  being  stated  in  the  Act  “ that  then 
a baker  in  every  quarter  of  wheat  (as  is  proved  by  the  King's  bakers)  may 
gain  fourpence  and  the  bran,  and  two  loaves  for  advantage  ; for  three 
servants  three  halfpence,  for  two  lads  one  halfpenny,  for  candle  one  far- 
thing, for  wood  twopence,  for  his  bultel  (or  bolting)  three  halfpence,"  in  all 
sixpence  three  farthings,  and  two  loaves  for  advantage. 

[That  is  to  say,  on  the  Assize  prices  the  baker's  profit  per  quarter  of 
wheat  was  fourpence  and  the  bran,  and  in  addition  sixpence  three  farthings 
to  cover  his  expenses  of  manufacture.  He  also  had  two  extra  loaves  for 
his  own  advantage.] 

The  Committee,  observing  the  allowance  thus  stated  to  be  made  to  the 
bakers  was  partly  in  money  and  partly  in  bread,  proceeded  to  examine  in 
what  way  the  table  of  assize  was  constructed  for  the  purpose  of  ensuring 
them  this  allowance.  They  took  the  case  of  “ wheaten  bread  " as  an  ex- 
ample. They  find  that  of  this  bread  it  is  stated  in  the  table,  “ When  wheat 
shall  sell  at  \2d.  the  quarter,  the  farthing  loaf  shall  weigh  lOZ.  ID.  6J.,"  which 
weight  (as  was  usual  in  those  times)  being  expressed  in  pounds,  shillings, 
and  pence,  the  Committee  find  the  pounds  to  be  the  Saxon  or  Tower  pound, 
which  is  to  the  Troy  pound  in  the  proportion  of  15  to  16.  They  then  cal- 
culate that  the  quantity  of  wheaten  bread  expressed  in  the  Statute  by  the 
denomination  of  lOZ.  ID.  6J.  is  equal  to  10-575  lbs.  Troy,  and  8-7087  lbs. 
Avoirdupois  ; as  one  loaf  of  this  weight  was  to  be  sold  for  a farthing  when 


568 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


a quarter  of  wheat  was  at  \2d.,  it  follows  that  48  such  loaves  (which  weigh 
418-02  lbs.  Avoirdupois)  was  the  exact  quantity  of  bread  which  was  to  be 
sold  for  the  price  of  a quarter  of  wheat  ; whatever  bread  could  be  made 
from  it  over  and  above  418  lbs.  was  for  the  baker’s  advantage,  and  this  is 
stated  in  the  statute  to  have  been  proved,  on  experiment,  to  have  amounted 
to  two  loaves  ; and  if  these  were  peck  loaves,  452  lbs.  14  ozs.  of  wheaten  bread 
was  the  quantity  obtained  by  the  King’s  bakers  from  a quarter  of  wheat. 

The  Committee  then  proceeded  to  examine  whether  the  quantity  of 
bread  at  that  time  obtained  from  a quarter  of  wheat  agreed  with  the  quantity 
asserted  in  the  statute.  They  appeal  to  the  record  of  an  experiment  re- 
ported to  the  House  in  1800,  by  which  it  appears  that  the  flour  from  a 
quarter  of  wheat  weighing  only  55  lbs.  a bushel,  and  dressed  after  the  mode 
then  in  use  for  preparing  flour  for  the  London  market  was  baked  into  433  lbs. 
of  wheaten  bread,  and  25  lbs.  of  household  bread.  The  Committee  are 
thereby  assured  that  when  the  baker  was  forced  to  sell  no  more  than  418 
lbs.  of  bread  for  the  price  of  a quarter  of  wheat,  he  really  obtained  in  surplus 
bread  the  two  [peck]  loaves  for  advantage  which  the  Statute  professed  to 
allow  him. 

The  money  allowance  appears  to  have  been  for  the  purpose  only  of 
repaying  the  baker’s  charges  for  grinding  and  baking,  while  the  advantage 
loaves  were  for  his  maintenance  and  profit. 

The  Committee  then  proceeded  to  trace  the  successive  alterations  which 
had  taken  place  in  these  two  allowances  to  the  bakers,  and  with  regard  to 
the  payment  in  money,  they  found  it  was  from  time  to  time  increased  and 
altered  : in  the  12th.  of  Henry  VI.  it  was  raised  to  two  shillings  per  quarter  ; 
and  the  Committee  begged  leave  to  point  out  that  a large  quantity  of  this 
allowance  appears  to  have  been  appropriated  to  the  baker  and  his  family 
who  by  31  Henry  III.  were  providedjor  by  the  advantage  loaves  : — 


“ Anno  1405,  12  Henry  VII.,  and  as  the  said  Book  of  Assize  declareth,” 
“ when  the  best  wheat  was  sold  at  Is.,  the  second  at  65.  Q)d.,  and  the  third 
at  65.  the  quarter. 

The  Baker  was  allowed. 


s.  d. 


“ Furnace  and  wood  . . . . . . . . ..06 

The  miller  . . . . . . . . . . ..04 

Two  journeymen  and  two  apprentices  . . ..05 

Salt,  yeast,  candle,  and  sack  bands  . . . . ..02 

Himself,  his  house,  his  wife,  his  dog,  and  his  cat  . . 0 7 


In  all 2 0 

And  the  Branne  to  his  advantage.” 

[Examination  of  the  figures  does  not  altogether  bear  out  the  Committee’s 
contention.  The  advantage  loaves  were  not  the  only  provision  for  the 
baker  in  the  days  of  King  John.  He  then  had  6|J.  for  his  expenses,  and 
4J.  allowance  and  the  bran  in  addition  to  the  advantage  loaves.  The  loaf 
allowance  and  the  bran  were  the  same  at  both  periods,  while  in  King  John’s 
time  the  total  money  allowance  was  lOfJ.,  against  2s.  Od.  in  1405.  From 
the  prices  given  for  wheat  the  value  of  money  was  about  six  times  as  much 
in  the  reign  of  John  as  in  the  time  of  Henry  VII.,  therefore  \0%d.  in  John’s 
reign  would  be  equal  to  10|J.  x Q = 5s.  4t^d.  The  baker’s  allowance  was 
thus  comparatively  much  less  in  1405.] 

For  the  long  period  of  556  years  the  quantity  of  bread  that  was  required 
to  be  sold  for  the  price  of  a quarter  of  wheat  remained  the  same,  that  is  to 
say  418  lbs.  But  the  money  allowance  was  from  time  to  time  raised,  until 
in  the  time  of  Anne  it  was  at  12<s.  per  quarter. 


THE  WEIGHING  OF  BREAD. 


569 


The  Committee  next  proceed  to  examine  the  Act  of  31  George  II.  [already 
■discussed],  and  point  out  that  the  table  of  assize  contained  therein  is  con- 
structed on  a principle  differing  from  all  those  which  preceded.  Instead 
of  417  [or  418]  lbs.,  the  bakers  were  to  sell  no  more  than  365  lbs.  of  wheaten 
bread  for  the  price  of  a quarter  of  wheat,  and  52  lbs.  of  bread  were  by  these 
means  added  to  the  two  advantage  loaves  originally  granted,  an  alteration 
which  could  not  fail  materially  to  raise  the  price  of  bread.  This  is  shown 
by  the  fact  that  in  the  table  in  8th.  of  Anne  [the  previous  assize  table],  when 
wheat  was  at  845.  the  quarter,  and  the  baker's  allowance  at  125.,  the  quartern 
loaf  of  wheaten  bread,  weighing  4 lbs.  5J  ozs.,  was  to  be  sold  for  one  shilling. 
By  the  table  of  31  George  II.,  with  the  price  of  wheat  and  all  other  con- 
ditions the  same  amount,  the  quartern  loaf  was  to  be  sold  at  13|c?.  This 
increase  in  the  price  of  bread  gave  rise  to  much  inquiry,  and  in  the  1 3th. 
of  George  III.  an  Act  was  passed  re-enacting  the  table  of  the  8th.  of  Anne. 
The  bakers’  profits  were  thus  so  largely  reduced  that  they  found  means  to 
prevent  the  possibility  of  putting  the  Act  in  force  in  London.  The  Com- 
mittee next  investigated  the  methods  by  which  the  market  price  of  wheat, 
and  latterly  of  flour,  were  to  be  ascertained,  and  place  on  record  that  they 
are  to  be  those  at  which  the  grain,  meal,  or  flour  shall  openly  and  publicly 
be  sold  during  the  whole  market,  and  not  at  any  particular  times  thereof, 
and  these  prices  were  to  be  returned  on  oath. 

The  preamble  of  the  Act  of  Anne  defines  the  object  of  the  Assize  laws 
to  be  “ to  provide  for  the  reasonable  price  of  bread,  and  to  prevent  covetous 
and  evil-disposed  persons  for  their  own  gain  and  lucre  from  deceiving  and 
oppressing  her  Majesty’s  subjects,  especially  the  poorer  sort.”  Summing 
up  their  conclusions,  the  Committee  report  that  they  “ cannot  but  enter- 
tain doubts  whether  the  Assize  laws,  even  in  their  earlier  and  better  state, 
ever  really  effected  their  intended  object  ; but  in  later  times,  when  the 
tables  in  the  31st.  George  II.  came  into  use,  your  Committee  are  founded  in 
believing  they  had  a contrary  effect.” 

The  Committee  next  proceeded  to  examine  the  Acts  of  37  George  III. 
and  other  subsequent  amending  Acts,  and  in  so  doing  comment  on  the 
introduction  of  the  price  of  flour  into  the  considerations  determining  the 
price  of  bread.  The  earliest  direction  to  that  eSect  to  the  magistrates  as 
a Court  of  Assize  was  in  the  8th.  of  Anne  ; but  it  appears  from  the  Journal 
of  the  House  that  in  the  year  1735  a petition  was  presented  to  the  House 
by  the  Bakers’  Company,  stating  the  hardships  under  which  they  laboured, 
and  praying  that  the  assize  of  bread  might  be  set  by  the  price  of  flour. 
For  the  first  time  in  any  statute  a regular  flour  table  was  introduced  in  the 
37th.  of  George  III.,  which  was  calculated  on  the  principle  of  31  George  II., 
where  it  is  directed  generally  that  20  peck  loaves  are  to  be  made  and  sold 
from  a sack  of  280  lbs.  of  flour  ; and  by  this  direction  it  appears  the  magis- 
trates of  the  City  of  London  proceeded  to  fix  the  price  of  bread,  and  from 
that  time  but  little  reference  has  been  made  to  the  price  of  wheat.  On 
this  flour  basis  it  is  to  be  observed  that  no  advantage  bread  was  intended 
to  be  allowed  to  the  baker,  it  having  been  assumed  that  20  peck  loaves  is 
the  whole  quantity  which  can  be  made  from  a sack  of  flour,  though  the 
Committee  were  informed  by  several  witnesses  whom  they  examined  that 
a larger  quantity  is  almost  always  made  from  it  ; by  this  table  a money 
allowance  of  II5.  8J.  per  sack  was  made  to  the  baker,  which  has  been 
subsequently  increased  to  145.  \d.  The  alternative  wheat  table  given  in 
this  Act  differs  but  little  from  that  in  the  preceding  Act.  The  Committee 
proceed  to  compare  the  two,  and  “ could  not  help  observing  with  surprise 
that  the  price  of  bread  as  actually  set  by  the  flour  table  was  nearly  as  high, 
and  sometimes  actually  higher,  than  it  would  have  been  if  set  by  the  wheat 
table.”  In  order  to  find  some  solution  of  this  the  Committee  proceeded 


570 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


to  examine  the  mode  in  which  the  returns  of  flour  were  now  obtained,  and 
found  that,  instead  of  the  mode  of  taking  the  prices  in  pubhc  market,  “ the 
bakers  are  now  directed  to  make  weekly  returns  upon  oath  to  the  Cocket 
Office  of  all  flour  and  meal  which  shall  have  respectively  been  bought  by 
them  during  the  week  preceding  ; and  the  price  of  bread  depends  entirely 
on  the  average  of  these  returns,  as  they  must  be  acted  on  as  true  without 
they  can  be  proved  to  be  false,  whenever  the  price  of  bread  is  set  by  the 
flour  table.'' 

The  Committee  next  And  that  a small  portion  only  of  what  is  included 
in  the  bakers'  returns  is  bought  and  sold  in  public  market,  and  that  the 
full-priced  bakers  are  very  little  in  the  habit  of  attending  the  flour  market, 
or  of  endeavouring  to  purchase  flour  at  the  lowest  price  ; that  they  are  for 
the  most  part  persons  in  needy  circumstances,  largely  indebted  to  the  millers 
and  flour  factors  with  w'hom  they  deal,  and  in  consequence  are  under  the 
necessity  of  receiving  flour  from  them  at  the  price  they  think  fit  to  put  upon 
it  ; provided  only  that  the  flour  is  of  the  best  quality,  and  the  price  is  not 
liigher  than  that  which  is  returned  as  the  general  price  of  the  week  by  the 
Lord  Mayor ; although  it  appears  by  the  evidence  that  it  can  at  all  times  be 
purchased  for  ready  money  or  on  short  credit,  for  a less  price  than  the  bakers 
are  prepared  to  take  it  at. 

The  Committee  could  not  fail  further  to  observe  that  the  bakers,  taking 
them  as  a trade  collectively,  were  prevented  by  the  operations  of  the  assize 
law  from  having  any  direct  interest  in  the  price  at  which  they  purchased 
flour  ; whatever  price  they  gave  for  it  per  sack,  that  price  is  to  be  returned 
to  them  for  eighty  quartern  loaves  : if  the  price  of  flour  is  reduced,  a 
simultaneous  and  exactly  corresponding  decrease  in  the  price  of  bread 
prevents  the  bakers  from  deriving  the  smallest  advantage  by  it  ; but  if  it 
is  raised,  then  a similar  increase  in  the  price  of  bread  prevents  them  from 
being  exposed  to  the  smallest  loss  ; equally  whether  the  price  is  low  or 
high,  they  obtain  145.  Id.  per  sack  for  their  expenses  in  baking,  and  if  80 
quartern  loaves  was  the  precise  quantity  of  bread  they  could  at  all  times 
make  from  a sack  of  flour,  they  would  have  no  interest  whatever  in  its  general 
price,  either  one  way  or  another  ; but  the  surplus  bread,  whatever  may 
be  its  amount  which  they  can  make  above  that  quantity  (and  it  is  stated 
by  various  persons  to  average  from  two  to  four  loaves),  is  to  them  a profit 
in  kind,  the  value  of  which  must  necessarily  increase  with  the  price  of 
bread.  And  as  the  high  price  of  flour,  which  occasions  this  increase,  is  in 
no  other  respect  disadvantageous  to  the  bakers,  they  have  as  far  as  it  goes 
an  obvious  interest  in  the  high  price  of  flour.  And  it  is  to  the  operation  of 
this  principle  which  the  Committee  attributes  the  indifference  about  the 
price,  as  well  as  the  anxiety  about  the  quality  of  flour,  for  the  best  flour  will 
always  make  more  bread,  as  well  as  whiter  bread  ; and  where  the  price 
by  the  assize  is  uniform,  the  seller  has  no  mode  of  seeking  for  better  custom 
but  by  offering  a whiter  loaf  than  his  neighbour. 

The  attitude  of  the  sellers  of  flour  is  also  examined  by  the  Committee, 
who  find  that  they  are  eager  to  dispose  of  it  at  the  high  prices  returned  to 
the  Lord  Mayor  : but  that  in  order  to  do  this  it  seems  they  must  be  content 
to  sell  on  long  and  doubtful  credit,  and  many  of  them  have  recourse  to 
becoming  proprietors  of  bakehouses,  and  carrying  on  the  baking  trade  on 
tlieir  own  account  by  means  of  journeymen,  to  obtaining  leases  of  bakers' 
liouses,  encouraging  journeymen  to  set  up  for  themselves,  and  to  giving 
large  sums  for  the  goodwill  of  bakers'  houses.  These  practices  the  Committee 
find  liave  divided  the  trade  into  two  sections,  the  one  of  which  carries  on 
a high-priced  credit  business,  and  another  consisting  of  those  who  sell  for 
money  in  a regular  way  and  are  contented  with  a low  price.  Latterly  this 
lias  led  to  the  establishment  of  numerous  shops  in  which  bread  is  sold  below 


THE  WEIGHING  OF  BREAD. 


571 


the  assize  price  ; and  the  Committee  are  informed  that  these  shops  are 
enabled  to  go  on  chiefly  by  the  low  price  at  which  flour  is  to  be  bought  by 
persons  with  capital,  though  some  of  them  appear  to  derive  advantage  from 
selling  for  ready  money  only. 

The  Committee  also  pointed  out  that  the  high  prices  which  are  returned 
to  the  Cocket  Office  are  further  influenced  by  the  following  circumstances  : — 

“ 1st. — That  it  is  the  practice  of  some  bakers  to  return  their  purchases 
of  flour  at  a full  credit  price,  though  they  subsequently  obtain  an  allow- 
ance for  prompt  payment  in  the  shape  of  discount.  2ndly. — That  much 
flour  is  returned  at  a higher  price  than  that  at  which  it  was  purchased. 
3rdly. — That  much  low-priced  flour  is  omitted  in  the  returns  altogether. 

The  Committee,  for  the  foregoing  reasons,  were  led  to  believe  that  “ the 
assize  price  of  bread  in  London  is  higher  than  if  no  assize  had  ever  existed, 
were  further  confirmed  in  that  opinion  by  information  which  they  procured 
from  Manchester,  Birmingham,  Newcastle,  Bath,  and  Lewes,  in  which 
places  they  were  informed  no  assize  was  set  ; and  they  found  in  all  of  them 
the  prices  both  of  flour  and  bread  have  been  lower  than  in  London,  though 
it  does  not  appear  that  wheat  has  been  cheaper.’' 

The  Committee  next  addressed  themselves  to  the  question  whether  it 
was  possible  to  frame  an  assize  law  which  should  be  free  from  the  foregoing 
objection,  that  it  is  of  no  importance  to  the  baker  whether  the  price  of  flour 
is  low  or  high.  They,  however,  came  to  the  conclusion  that  the  evil  was 
inherent  in  the  nature  of  an  assize.  They  then  considered  whether  it  would 
be  well  to  revert  to  taking  the  price  of  wheat  instead  of  that  of  flour,  but 
for  a number  of  reasons,  duly  set  out,  they  came  to  the  conclusion  “ that  no 
benefit  is  likely  to  result  from  any  mode  which  could  be  resorted  to  in  London 
of  fixing  the  assize  of  bread  by  the  price  of  wheat.”  They  next  inquired 
as  to  how  far  it  might  be  possible  to  obtain  true  returns  of  the  genuine 
price  of  flour,  but  came  to  the  conclusion  that  no  enactment  could  avail 
to  entirely  prevent  fraud  in  maldng  such  returns.  And  even  if  it  were 
possible  to  fix  an  assize  based  on  the  accurate  price  of  flour,  the  Committee 
begged  leave  to  point  out  “ that  no  benefit  can  be  expected  to  result  from 
it,  beyond  that  of  fixing  a rate  upon  the  labour  and  profits  of  the  bakers, 
whilst  the  millers  and  mealmen  must  be  left  wholly  without  any  control.” 

The  Committee  summarised  the  result  of  their  labours  in  the  following 
conclusions  : — 

“ Your  Committee  are  distinctly  of  opinion  that  more  benefit  is  likely 
to  result  from  the  effects  of  a free  competition  in  their  trade  than  can  be 
expected  to  result  from  any  regulations  or  restrictions  under  which  they 
could  possibly  be  placed.” 

“ Your  Committee  are  of  opinion  that  if  the  trade  was  thrown  open  by 
the  repeal  of  the  Assize  Laws  it  would  have  the  effect  of  gradually  drawing 
persons  with  capital  into  it,  of  diminishing  the  waste  of  labour  and  un- 
necessary sub-division  of  profit,  which  appear  by  the  evidence  at  present 
to  exist.” 

Finally,  your  Committee  came  to  the  following  resolution  : — 

“ Resolved,  That  it  is  the  opinion  of  this  Committee  that  it  is  expedient 
that  the  Bread  Assize  Laws  for  the  City  of  London,  and  ’within  ten  miles 
of  the  Royal  Exchange,  should  be  forthwith  repealed.” 

670.  Leave  to  Bring  in  a Bill. — After  this  report  of  June  6,  little  tin  e 
was  lost  in  taking  the  necessary  steps  to  give  effect  to  the  resolution  of 
the  Committee  by  legislation.  On  June  22,  1815,  Mr.  Frankland  Lewis 
called  the  attention  of  the  House  of  Commons  to  the  report,  and  moved 
“ that  leave  be  given  to  bring  in  a Bill  to  repeal  the  laws  relating  to  the 
Assize  of  Bread,  in  the  City  of  London,  and  within  ten  miles  of  the  Royal 
Exchange.” — Leave  was  accordingly  given. 


572 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Motion  for  Second  Reading  of  Bill. — This  took  place  on  June  27. 

Mr.  Calcraft  expressed  a wish  that  it  should  be  postponed,  in  order  that 
the  public  should  have  sufficient  opportunity  of  considering  its  merits. 
For  himself,  lie  declared  an  inability  to  comprehend  how  the  public  could  be 
benefited  by  a measure  of  this  nature. 

Mr.  Alderman  C.  Smith  had  no  objection  to  the  Bill,  but  wished  that 
the  bakers  should  be  protected. 

General  Thornton  wished  that  its  provisions  were  extended  throughout 
the  country. 

Mr.  Alderman  Atkins  thought  that  the  House  should  be  very  cautious 
how  they  overturned  a system  which  had  stood  the  test  of  700  years.  The 
principle  of  the  Ass:ze  Law  was,  in  his  opinion,  unobjectionable. 

Mr.  F.  Lewis  argued  in  support  of  the  Bill,  basing  his  argument  princi- 
pally on  the  reasons  and  conclusions  of  the  Committee. 

After  further  discussion  the  Bill  was  then  committed. 

Discussion  in  Committee. — It  was  not  so  much  the  merits  of  the  Bill  as 
whether  it  should  be  proceeded  with  or  deferred  which  principally  occupied 
the  attention  of  the  Committee  on  June  30.  Mr.  Alderman  C.  Smith  thought 
the  passing  of  the  Bill  would  be  a relief  to  bakers.  Finally  the  Bill  was 
committed,  and  read  a first  and  second  time. 

After  further  debate,  Alderman  Atkins  proposed  a clause  to  allow  bakers 
to  make  bread  of  any  weight,  without  binding  them  to  a specific  quantity 
in  the  size  of  the  loaf,  but  merely  to  sell  it  at  a certain  price  per  pound. 
This  clause  was  rejected. 

Petitions  For  and  Against. — On  July  4 Mr.  F.  Lewis  presented  a Petition, 
signed  by  800  Master  Bakers,  praying  that  the  Bill  now  in  progress  through 
the  House  for  the  purpose  of  abolishing  the  assize  of  bread  in  London  and 
its  vicinity  might  be  passed  into  a law.  Mr.  Alderman  Atkins  presented 
a Petition  from  the  Master  and  Wardens  of  the  Bakers"  Company  against 
the  Bill.  The  Petition  expressed  the  conviction  of  the  petitioners  that  it 
would  be  mischievous  to  them,  and  not  at  all  beneficial  to  the  public. 

Mr.  F.  Lewis  said  it  at  first  sight  must  appear  strange  that  two  parties 
seemingly  connected  with  the  same  trade  should  express  sentiments  so  very 
dissimilar.  But  the  fact  was,  that  scarcely  a person  whose  name  was  signed 
to  the  last  Petition  was  a baker.  The  petitioners,  though  calling  them- 
selves bakers,  were  chiefly  meal-men  and  flour-factors. 

Third  Reading. — The  Bill  was  read  a third  time  on  July  5,  and  passed. 

In  no  reports  or  discussions  on  the  passing  of  this  Act  are  there  found 
any  references  to  the  reasons  which  led  to  the  introduction  of  the  Proviso 
exempting  French  or  Fancy  Bread  from  the  necessity  of  being  sold  by  weight. 

After  700  years  during  which  Bakers  were  compelled  to  sell  a fixed  quan- 
tity of  bread  for  a fixed  price,  liberty  to  sell  at  whatever  price  they  wished 
was  first  given  by  this  Act,  which  came  into  operation  on  September  1,  1815, 
a date  which  may  well  be  called  that  of  The  Magna  Charta  of  the  Baking  Trade. 

671.  Further  Legislation. — ^The  Act  of  59  George  III.,  1819,  has  already 
received  notice.  But  still  the  Bread  Laws,  even  in  their  radically  altered 
form,  failed  to  secure  to  the  public  that  protection  which  it  was  thought 
they  required,  and  remained  a source  of  annoyance  to  the  baking  trade. 
Accordingly,  on  March  15,  1821,  we  find  Mr.  Harhord  moved  for  the  appoint- 
ment of  a Select  Committee  to  take  into  consideration  the  existing  regula- 
tions for  the  sale  of  Bread.  In  his  view,  the  existing  law  on  the  subject 
was  pernicious  in  tendency,  inasmuch  as  it  held  forth  to  the  poor  the  ex- 
pectation of  a protection  which  it  did  not  realise,  and  prevented  them  from 
using  that  caution  to  which  they  would  otherwise  resort.  Mr.  Littleton 
was  inclined  to  think  tliat  unrestricted  competition  would  afford  the  public 


THE  WEIGHING  OF  BREAD. 


573 


greater  security  than  any  legislative  enactment,  but  was  of  opinion,  at  the 
same  time,  that  there  should  be  either  an  entire  repeal  of  the  law,  or  that 
bread  should  in  future  be  sold  by  weight.  The  Select  Committee  was 
appointed. 

672.  Report  of  Select  Committee,  April  17,  1821. — The  result  of  the 
deliberations  of  the  Committee  are  contained  in  the  following  summary  : — 

“ On  the  part  of  the  Baker  and  seller  of  Bread,  it  has  been  proved  by  the 
evidence,  taken  before  Your  Committee,  of  respectable  Bakers  in  the  metro- 
polis (which  evidence  is  subjoined  in  the  Appendix),  that  it  is  impossible 
for  the  Baker,  even  under  the  present  law,  to  guard  against  vexatious  and 
unjust  informations  for  selling  Bread  deficient  in  weight.  It  appears  that 
unless  the  Baker  makes  all  the  loaves  in  a batch,  upon  an  average,  so  heavy 
as  to  cover  the  partial  deficiency  of  weight  in  any  of  them  (occasioned 
either  by  their  particular  position  in  the  oven,  or  from  some  part  of  one 
loaf  unavoidably  adhering  to  the  other),  there  must  be  loaves  which,  with- 
out any  fraudulent  intention  on  the  part  of  the  Baker,  would  be  deficient  in 
weight,  and  render  him  liable  to  conviction  under  the  existing  law.  It  is 
obvious,  that  were  the  Baker  to  adopt  the  only  course  which  could  give 
him  security,  namely,  that  of  making  the  batch  of  loaves  so  much  over 
weight  as  to  cover  the  partial  deficiency  in  any  of  them,  his  price  being 
fixed  upon  the  minimum  of  weight  among  the  loaves  of  the  batch,  he  must 
lose  his  profit  upon  the  average  of  loaves,  or  sell  at  a rate  above  the  pre- 
vailing prices,  which  would  be  the  means  of  losing  his  customers.  It  has 
also  been  stated  in  evidence,  that  the  present  law  relative  to  the  sale  of 
Bread,  fails  in  affording  the  Baker  protection  against  the  persecution  of 
common  informers.  Individuals  of  their  trade  known  to  themselves,  have 
been  induced  by  threats  from  that  class  of  persons,  to  enter  into  a sort  of 
compromise  with  them,  and  to  bargain,  that  upon  payment  of  a certain 
sum  per  month,  they  should  be  allowed,  with  impunity  (so  far  as  the  informer 
of  the  district  is  concerned),  to  impose  upon  the  public  by  selling  their  Bread 
deficient  in  weight.  Whatever  their  original  disposition  therefore  might 
be,  after  entering  into  such  eui  agreement,  it  is  natural  to  conclude,  that 
they  indemnify  themselves  to  that  amount  at  the  expense  of  the  public. 

The  nugatory  and  consequently  mischievous  tendency  of  the  existing 
law,  holding  forth  to  the  public  an  expectation  of  protection,  which,  in 
reality,  it  does  not  afford,  thereby  suspending  the  caution  natural  to  all 
men  in  their  own  defence,  appears  to  be  sufficient  objection  to  the  existing 
law,  so  far  as  concerns  the  public.  It  thence  became  a question,  what  im- 
provement in  the  law  could  be  made  ? A deliberate  review  of  the  subject 
has  been  taken  by  Your  Committee  ; and  they  have  no  hesitation  in  recom- 
mending that  the  law  relative  to  the  sale  of  Bread,  should  in  future  impose 
no  restriction  as  to  the  denomination  of  loaves,  or  their  weight.  Com- 
petition has  been  found,  in  most  cases,  effectually  to  supply  the  place  of 
legisledive  regulation.  And  Your  Committee  cannot  discover  any  reason 
for  supposing  that  it  would  fail  upon  trial  equally  to  secure  to  the  public  a 
fair  quantity  of  this,  as  of  all  other  articles  of  subsistance,  which  are  sold 
by  weight  generally  without  restriction.  Your  Committee  have  been 
informed,  that  the  practice  of  selling  Bread  free  from  all  restrictions  has 
prevailed  in  some  districts  of  the  Kingdom  for  many  years.  Communica- 
tion has  been  had  with  some  of  those  districts,  and  no  complaint  is  there 
heard  against  the  Bakers,  and  Bread  has  been,  and  continues  to  be,  sold  in 
such  places,  of  excellent  quality,  and  at  the  lowest  possible  price.” 

673.  Bill  of  1822. — On  Thursday,  April  2,  Mr.  Calvert  moved  for  leave 
to  bring  in  a bill  dealing  with  the  sale  of  bread  within  ten  miles  of  the  Royal 
Exchange.  He  thought  the  public  might  be  protected  in  two  ways — the 


574 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


one  by  the  sale  of  bread,  like  any  other  article,  by  the  pound  ; and  the  other 
by  the  sale  of  it  by  the  piece,  that  is  in  loaves  of  the  value  of  I5.,  6d.,  3d., 
and  so  on.  He  still  regarded  legislation  on  adulteration  as  necessary,  as 
it  appeared  from  a pamphlet  that  a great  deal  of  marble  powder  was  used 
by  some  of  the  London  bakers  in  the  composition  of  what  they  called  bread. 
Leave  was  given  to  bring  in  the  bill,  which  ultimately  became  the 

674.  Act  of  3 George  IV.,  c.  108,  July  22,  1822. — The  essential  subject 
matter  of  this  Act  is  the  following.  It  repeals  the  Acts  now  in  force  relating 
to  Bread  to  be  sold  in  the  City  of  London,  and  Ten  Miles  of  the  Royal  Ex- 
change ; and  provides  other  Regulations  for  the  Making  and  Sale  of  Bread, 
and  preventing  the  Adulteration  of  Meal,  Flour,  and  Bread,  within  the 
Limits  aforesaid.  The  Act  provides  that  Bread  made  of  the  Articles  therein 
mentioned,  but  from  no  others,  may  be  sold,  and  that  Bakers  may  make 
Bread  of  any  Weight  or  Size.  The  Bread  must  be  sold  by  Weight,  and 
in  no  other  manner,  under  Penalty  not  exceeding  405.  This  last  enactment 
is  not  to  extend  to  French  or  Fancy  Bread  or  Rolls. 

675.  Act  of  6 and  7 William  IV.,  c . 37,  July  28,  1838.— It  will  be 
noticed  that  this  Act  was  passed  fourteen  years  after  that  last  referred  to. 
Its  object  was  ‘ ‘ to  repeal  the  several  Acts  now  in  force  relating  to  Bread  to  be 
sold  out  of  the  City  of  London  and  beyond  Ten  Miles  of  the  Royal  Exchange  ; 
and  provides  other  Regulations  for  the  Making  and  Sale  of  Bread,  and  for 
preventing  the  Adulteration  of  Meal,  Flour,  and  Bread,  beyond  the  Limits 
aforesaid.” 

The  Act  first  of  all  recites  the  title  of  the  Act  of  3 George  IV.,  and  goes 
on  to  state  that  such  Act  has  “ been  found  beneficial  to  the  Public,  as  well 
as  to  the  Bakers  within  the  said  limits.”  It  in  consequence  goes  on  to  enact 
that  all  Acts  relating  to  the  making  and  selling  of  Bread,  or  to  the  Punish- 
ment for  adulterating  Meal,  etc.,  out  of  the  City  of  London  and  other  dis- 
tricts associated  therewith  are  repealed.  In  particular,  that  “ there  shall 
be  no  longer  any  Assize  of  Bread,  beyond  the  Limits  aforesaid,  or  any  Regu- 
lations respecting  the  Price  thereof.”  It  then  proceeds  to  enact  precisely 
similar  provisions  to  those  previously  recited  as  being  of  the  essence  of  the 
Act  of  3 George  IV.  The  whole  of  Great  Britain  was  thus  brought  under 
wliat  are  practically  the  same  Bread  Laws.  Ireland,  however,  was  ex- 
pressly exempted  from  the  operation  of  this  Act. 

676.  Summary  of  Historical  Development. — From  the  time  of  King  John, 
down  to  the  Act  of  55  George  III.,  1815,  roughly  about  700  years,  the 
authorities  throughout  the  kingdom  had  power  to  compel  the  baker,  by 
what  was  known  as  the  Assize  of  Bread,  to  sell  his  Bread  according  to  a 
fixed  scale  of  prices  and  weights. 

By  the  Act  of  55  George  III.,  1815,  the  Assize  of  Bread  was  abolished 
within  tlie  City  of  London  and  ten  miles  of  the  Royal  Exchange.  The 
London  Bakers  were  thus  enabled  to  charge  what  price  they  pleased  for  their 
Bread,  but  were  still  compelled  to  sell  it  in  loaves  of  certain  specified  weights. 
For  the  first  time  a proviso  is  here  inserted  which  exempts  French  or  Fancy 
Bread  or  Rolls  from  the  obligation  of  sale  by  weight. 

By  the  Act  of  3 George  IV.,  1822,  London  bakers  were  permitted  to 
make  bread  of  any  weight  or  size  they  chose  and  sell  by  weight  at  any  price 
they  liked,  still  subject  to  the  Fancy  Bread  exemption. 

Until  6 and  7 William  IV.,  1836,  the  Assize  of  Bread  Acts  were  still  in 
existence  for  the  rest  of  Great  Britain,  except  London.  Their  enforcement 
was,  liowever,  optional,  and  gradually  they  had  been  falling  into  desuetude, 
until  by  this  Act  the  whole  of  such  obligations  were  repealed.  From  that 
date  until  the  present  one  practically  uniform  law  has  been  in  operation  for 


THE  WEIGHING  OF  BREAD.  575 

■Great  Britain,  and  is  contained  in  the  two  Acts  of  3 George  IV.  and  6 and  7 
William  IV.,  known  together  as  the  Bread  Acts. 

It  is  worthy  of  notice  how  carefully  the  whole  experiment  of  removing 
the  restrictions  on  the  sale  of  bread  was  made.  Each  increase  of  liberty 
to  the  baker  was  given  with  timidity  and  the  expression  of  much  misgiving 
by  many  legislators.  This  is  most  strikingly  exemplified  by  the  state  of 
things  existing  from  1822  to  1836.  Three  sets  of  conditions  then  existed 
in  the  country  side  by  side.  London  had  had  the  Assize  of  Bread  abolished 
by  express  statutory  enactment.  In  the  provinces  the  setting  of  an  Assize 
was  optional,  and  while  still  enforced  in  some  districts,  had  become  obsolete 
in  others.  A careful  study  of  the  effects  of  the  various  modes  of  regulating 
bread  sales  led  Parliament  to  the  conclusion^  expressed  in  the  first  clause  of 
6 and  7 William  IV.,  that  the  abolition  of  the  Assize  of  Bread  had  “ been  found 
beneficial  to  the  Public  as  well  as  to  the  Bakers.’'  Experiment,  therefore, 
fully  bore  out  the  statesmanlike  view  expressed  by  the  Select  Committee  of 
1815,  viz.,  that  more  benefit  would  result  from  the  effects  of  a free  com- 
petition in  the  baker’s  trade,  than  could  be  expected  to  result,  “ from  any 
regulations  or  restrictions  under  which  bakers  could  possibly  be  placed.” 

677.  Operative  Weight  Sections  of  the  Bread  Acts. — The  following  are 
such  sections  of  the  Acts,  dealing  with  the  weighing  of  bread  as  seem  to  be 
of  importance  in  connection  with  the  present  subject.  The  text  is  that  of 
the  earlier  Act,  with  any  differences  in  the  latter  inserted  in  brackets.  The 
marginal  notes  of  the  Acts  are  for  convenience  printed  in  italics  at  the  head 
of  each  section. 

Bakers  to  make  Bread  of  any  Weight  or  Size. 

III.  And  be  it  [further]  enacted,  That  it  shall  and  may  be  lawful 
for  the  several  Bakers  or  Sellers  of  Bread  within  [beyond]  the  limits 
aforesaid,  to  make  and  sell,  or  offer  for  Sale,  in  his,  her,  or  their  Shop, 
or  to  deliver  to  his,  her,  or  their  Customers,  Bread  made  of  such  Weight 
or  Size  as  such  Bakers  or  Sellers  of  Bread  shall  think  fit  ; any  Law 
or  Usage  to  the  contrary  notwithstanding. 

This  was  the  essential  and  operative  clause  of  the  Acts,  whereby  bakers 
-were  expressly  freed  from  the  obligation  to  sell  by  the  Peck  and  other  fixed 
weight  loaves,  including  the  Quartern  and  Half- quartern. 

Broad  to  he  sold  hy  Weight,  and  in  no  other  manner  under  Penalty  not 
exceeding  40s.  Not  to  extend  to  French  or  Fancy  Bread  or  Rolls. 

IV.  And  be  it  [further]  enacted.  That  from  and  after  the  Com- 
mencement of  this  Act,  all  Bread  sold  within  [beyond]  the  Limits 
aforesaid,  shall  be  sold  by  the  several  Bakers  or  Sellers  of  Bread  re- 
spectively within  [beyond]  the  said  Limits  by  Weight  ; and  in  case 
any  Baker  or  Seller  of  Bread  within  [beyond]  the  Limits  aforesaid 
shall  sell,  or  cause  to  be  sold.  Bread  in  any  other  Manner  than  by 
Weight,  then  and  in  such  case  every  such  Baker  or  Seller  of  Bread 
shall,  for  every  such  Offence,  forfeit  and  pay  any  Sum  not  exceeding 
Forty  Shillings,  which  the  Magistrate  or  Magistrates,  Justice  or  Jus- 
tices, before  whom  such  Offender  or  Offenders  shall  be  convicted,  shall 
order  and  direct  : Provided  always,  that  nothing  in  this  Act  contained 
shall  extend  or  be  construed  to  extend  to  prevent  or  hinder  any  such 
Baker  or  Seller  of  Bread  from  selling  Bread  usually  sold  under  the 
Denomination  of  French  or  Fancy  Bread,  or  Rolls,  without  previously 
Aveighing  the  same. 

Penalty  on  Bakers  using  any  other  Weight  than  Avoirdupois  Weight, 
.not  exceeding  51.  nor  less  than  40s. 

V.  And  be  it  further  enacted.  That  the  several  Bakers  or  Sellers 


570 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

of  Bread  respectively  within  [beyond]  the  said  Limits,  in  the  Sale- 
of  Bread  shall  use  the  Avoirdupois  Weight  of  Sixteen  Ounces  to  the 
Pound,  according  to  the  Standard  in  the  Exchequer,  and  the  several 
Gradations  of  the  same  for  any  less  Quantity  than  a Pound  ; etc.,  etc. 

By  the  Weights  and  Measures  (Metric  System)  Act,  1897,  it  is  enacted 
that  “ the  use  in  trade  of  a weight  or  measure  of  the  metric  system  shall  be 
lawful.''  If  this  should  be  held  to  override  the  specific  statute,  the  baker 
is  now  permitted,  if  he  so  wishes,  to  sell  Bread  by  the  metric  system,  the 
commercial  unit  of  which  is  the  kilogram,  which  is  equivalent  to  2 lb.  SJ  oz. 
of  avoirdupois. 

The  Peck  Loaf  and  its  Subdivisions  not  to  be  made  or  sold  during  the 
next  Two  Years  : Under  Penalty  not  exceeding  10/.  nor  less  than  40^. 

VI.  Provided  always,  and  be  it  further  enacted,  That  it  shall  not 
be  lawful  for  any  Baker  or  Seller  of  Bread  within  the  limits  aforesaid, 
during  the  Space  of  Two  Years  from  the  Commencement  of  this  Act, 
to  make  and  sell,  or  offer  for  Sale  in  his,  her,  or  their  Shop,  or  to  deliver 
to  his,  her,  or  their  Customer  or  Customers,  any  Loaf  or  Loaves,  of  the 
Description  or  Denomination  of  the  Peck,  Half  Peck,  Quarter  of  a 
Peck,  or  Half-quarter  of  a Peck  Loaf  or  Loaves,  or  any  or  either  of 
them  ; etc.,  etc. 

[There  is  no  corresponding  section  in  the  Act  of  William  IV.] 

Penalty  for  selling  Bread  not  previously  Weighed,  not  exceeding  IO5. 

VII.  And  be  it  further  enacted.  That  in  case  any  such  Baker  or 
Seller  of  Bread  shall  at  any  Time  before  the  Expiration  of  Two  Years 
from  the  Commencement  of  this  Act,  sell  or  deliver  in  his,  her,  or 
their  Shop,  House,  or  Premises,  any  Bread  wLich  shall  not  have  been 
previously  weighed  in  the  Presence  of  the  Party  purchasing  the  same, 
whether  required  by  the  Purchaser  so  to  do  or  not,  except  as  afore- 
said, then  and  in  every  such  case,  every  such  Baker  of  Bread  so  offend- 
ing, shall,  upon  Conviction  in  Manner  hereinafter  mentioned,  forfeit 
and  pay  for  every  such  Offence,  any  Sum  not  exceeding  the  Sum  of 
Ten  Shillings,  as  the  Magistrate  or  Magistrates,  Justice  or  Justices, 
before  wLom  such  Conviction  shall  take  place,  shall  from  Time  to 
Time  order  and  adjudge. 

[There  is  no  corresponding  section  in  the  Act  of  William.  IV.] 

678.  Intention  of  the  Bread  Acts. — To  obtain  a further  understanding 
of  the  operation  of  the  Bread  Acts  (by  wdiich  is  meant  the  tw^o  Acts  of  1822 
and  1836),  it  is  desirable  to  gather  as  far  as  one  can  what  was  the  actual 
intention  of  the  legislation  at  the  time  they  were  passed.  Although  the  Act 
of  1815  abolished  the  Assize  of  Bread  in  London,  it  still  compelled  the  sale 
to  be  in  loaves  of  certain  specified  w'eights.  There  can  be  little  doubt  that 
both  bakers  and  the  public  were  in  the  habit  of  regarding  the  loaf  as  the 
unit  of  sale  and  purchase.  People  not  only  bought  loaves,  but  thought 
in  loaves.  A buyer  purchased  so  many  loaves,  and  the  question  of  the 
precise  w'eight  of  bread  contained  in  each  w^as  a secondary  consideration. 
Parliament  in  1822  came  to  the  conclusion  that  it  wwld  be  a better  course 
for  both  the  baker  and  the  public,  that  they  should  buy  and  sell  by  w^eight 
of  bread,  and  that  the  loaf  should  be  the  secondary  consideration.  In  the 
Report  of  the  Select  Committee  of  1821  the  suggestion  is  made  that  com- 
petition would  “ secure  to  the  public  a fair  quantity  of  this  [bread],  as  of  all 
articles  of  subsistence,  whicli  are  sold  by  w^eight  generally."  Evidently 
tlieir  view'  w'as  that  bread  should  be  sold  by  w'eight  just  as  w'ere  other  articles- 
of  subsistence.  Tliis  being  so,  the  Acts  say  “ Bread  shall  be  sold  by  Weight, 
and  in  no  otlier  manner."  Just  as  a man  buys  a joint  of  meat  at  so  muck 


THE  WEIGHING  OF  BREAD. 


577 


per  lb.  it  was  intended  that  he  should  also  buy  bread  in  the  same  way.  The 
view  apparently  was  that  the  purchaser  should  demand  so  many  pounds  of 
bread,  or  if  he  selected  a loaf,  then  it  should  be  weighed,  and  he  should  pay 
for  that  weight  of  bread  at  a price  per  lb.  In  order  to  attain  this  object, 
the  baker  is  to  use  avoirdupois  weight,  and  must  provide  himself  with 
weights  of  this  denomination,  together  with  “ the  several  Gradations  of 
the  same  for  any  less  Quantity  than  a Pound.”  And  also  for  the  period  of 
two  years  from  the  commencement  of  the  Act  it  w^as  made  compulsory  on 
the  baker  under  penalty  to  weigh  the  bread  in  the  presence  of  the  purchaser 
before  selling  the  same,  whether  required  by  the  purchaser  to  do  so  or  not. 
One  can  only  assume  that  the  purpose  of  this  enactment  was  to  educate 
both  buyer  and  seller  into  the  habit  of  regarding  weight  as  being  of  the  essence 
of  the  transaction  of  the  sale  of  bread.  Simultaneously,  and  for  the  same 
space  of  time,  the  baker  was  also  under  penalty  prohibited  from  making 
or  selhng  any  Peck,  Half  Peck,  Quarter  Peck,  or  half-quarter  Peck  loaves. 
The  loaves  with  which  both  parties  were  familiar  were  not  to  be  made  or 
sold,  and  instead  a system  of  weighing  in  the  presence  of  the  buyer  had  to 
be  adopted.  Had  these  measures  succeeded  in  their  object,  the  buyer  of 
bread  w^ould  have  acquired  the  habit  of  buying  his  loaf  in  the  same  way  as 
his  joint  of  meat,  that  is  by  ascertaining  the  weight  and  then  paying  for 
so  many  pounds  and  ounces  at  a given  price  per  pound.  This  result  was  not, 
however,  realised.  Possibly  the  habit  of  seven  centuries"  growdh  was  not 
to  be  eradicated  by  a legal  prohibition  extending  over  two  years.  Further 
the  requirements  of  the  buyer  of  bread  were  still  best  served  by  the  sale  of 
a loaf.  A good  many  reasons  exist  for  this  preference  ; in  addition  to  the 
inevitable  irregularities  inseparable  from  the  incidents  of  manufacture,, 
one  other  among  them  may  be  cited.  The  tastes  of  consumers  of  bread 
vary  very  considerably  as  to  the  shape  of  loaf  which  they  prefer,  and  the 
degree  of  baking  to  Avhich  they  like  it  to  be  subjected.  It  is  comparatively 
recently  that  a baker  produced  on  oath,  before  a Committee  of  the  House 
of  Commons,  two  loaves  of  bread  each  made  from  2 lb.  2 oz.  of  dough — one 
weighed  2 lb.,  the  other  1 lb.  9 oz.,  and  both  represented  kinds  of  bread 
which  were  demanded  by  respective  sections  of  the  public.  Between  these 
extremes  there  are  intermediate  varieties  of  bread  of  every  gradation.  It 
is  practically  impossible  to  devise  a scheme  of  prices  by  weight  to  cover 
these  differences  of  yield  from  the  same  amount  of  dough.  But  as  all  are 
obtained  from  such  same  weight,  it  is  a perfectly  equitable  proceeding  to 
sell  all  at  the  same  price  per  loaf. 

We  have  therefore  the  baker  under  legal  compulsion  to  sell  bread  by 
weight,  and  at  the  same  time  the  consumer  insisting  on  buying  his  bread 
by  the  loaf,  and  requiring  such  variations  in  the  character  of  that  loaf  as 
to  render  a system  of  weight  prices  commercially  impracticable.  The  exist- 
ence of  this  conflict  between  the  legal  obligations  of  the  baker  and  the 
demands  of  the  bread- buying  public  should  be  borne  in  mind  when  studying 
the  various  cases  under  the  Bread  Acts  in  which  judicial  decisions  of  im- 
portance have  been  given. 

679.  What  Constitutes  Sale  by  Weight. — Jones  y.  Huxtable,  16L.T.R.  262 

(1867).  In  this  action  at  law,  it  was  decided  that  weighing  the  dough  before 
baking,  and  allovdng  a certain  weight  for  loss  in  the  oven  is  not  selling  bread 
by  weight. 

The  general  nature  of  this  case  is  well  summed  up  in  the  judgment  of 
Lush,  J.  : “ The  conviction  was  right.  The  object  of  the  Act  was  to  secure 
to  the  purchaser  of  bread  a proper  quantity  for  his  money,  and  the  question 
is  whether  the  justices  were  right  in  coming  to  the  conclusion  that  the  bread 
was  sold  otherwise  than  by  weight.  The  practice  of  the  appellant,  as 

p P 


578 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


proved,  was  to  weigh  the  dough  previous  to  baking,  but  to  do  nothing  to 
ascertain  the  weigh  of  the  loaf  when  baked,  which  stiould  have  been  four 
pounds  ; and  inasmuch  as  a quartern  loaf,  under  certain  circumstances, 
will  sometimes,  as  he  himself  shows,  lose  as  much  as  two  ounces,  or  even 
more,  in  the  twenty-four  hours,  it  becomes  the  more  necessary,  in  justice 
to  the  purchaser,  that  the  weight  should  be  duly  ascertained  at  the  time  of 
the  purchase.  When,  therefore,  as  in  the  present  instance,  a baker  sells 
that  which  he  represents  to  be  a quartern  loaf  of  four  pounds,  the  weight  of 
which  he,  nevertheless,  does  not  know  and  has  taken  no  pains  to  ascertain, 
it  is  clear  he  sells  by  denomination,  and  not  by  weight  as  required  by  the 
statute."^ 

It  will  be  seen  that  one  of  the  first  of  the  recorded  cases  under  the  Act 
deals  with  the  weighing  of  dough  instead  of  bread.  The  weighing  (or  equi- 
valent measuring)  of  dough  is  a necessity  in  bread  manufacture,  but  this 
weighing  does  not  obviate  the  necessity  of  the  weighing  of  bread.  The  law 
insists  that  it  is  the  weight  of  bread  at  the  time  of  sale  which  shall  govern 
the  transaction.  Variations  through  evaporation  or  other  causes  (which 
presumably  include  irregularities  in  the  degree  of  baking)  are  not  excuses 
for  bread’  being  deficient  in  weight,  but,  on  the  contrary,  urgent  reasons 
why  the  ascertainment  of  weight  should  be  made  at  the  time  of  the  purchase. 
From  the  judgment  it  appears  that  in  1867  the  quartern  loaf  had  come  to 
be  regarded  as  weighing  four  pounds. 

The  decision  in  this  case  lays  down  the  law  very  clearly  as  to  the  neces- 
sity for  weighing  the  bread,  even  though  the  pieces  of  dough  for  each  loaf 
have  been  accurately  weighed.  Nevertheless,  although  perfectly  unavail- 
ing, the  same  defence  is  still  being  continually  made.  The  preceding  para- 
graph will  have  made  clear  some  of  the  reasons  why  the  baker  feels  that 
an  exact  weighing  of  the  dough  is  the  most  equitable  proceeding.  Loaves 
for  which  he  obtains  the  same  price  have  greatly  varying  weights,  because 
of  different  requirements  of  his  customers,  though  all  are  made  of  the  same 
weight  of  dough.  The  reasons  advanced  by  the  learned  judge  for  his 
decision  are  not,  it  is  submitted,  scientifically  correct.  If  a loaf  of  bread 
when  baked  and  first  offered  to  the  public  loses  two  or  more  ounces  in  weight 
during  24  hours,  that  which  is  lost  is  only  the  natural  loss  of  water 
by  evaporation.  The  nutritive  substance  of  the  loaf  still  remains  intact 
and  undiminished.  Such  a loaf  when  first  baked  will  have  consisted 
of  about  30  ozs.  of  nutritive  bread  solids  and  18  ozs.  of  water.  After 
24  hours  it  will  have  still  contained  30  ozs.  of  nutritive  solid  matter  and 
16  ozs.  of  water.  No  injustice  whatever  is  done  to  the  purchaser  by  this 
loss  of  weight  of  water. 

Another  reason  why  the  baker  so  clings  to  the  weighing  of  dough  as  the 
fairest  method  of  dealing  with  bread,  is  that  it  is  the  only  stage  of  manufac- 
ture at  which  the  weight  is  within  his  control.  From  that  moment  on- 
Avards  there  is  a continual  diminution  in  AA^eight,  first  through  loss  in  the 
OAmn,  and  secondly  through  evaporation  until  sold.  This  last  is  a very 
variable  factor,  being  dependent  on  a number  of  causes,  as  for  examjle 
Avhether  the  bread  be  kept  in  a closed  or  an  open  space  ; AAdiether  the  air  is 
Avarm  or  cold,  Avhether  it  is  dry  or  humid  ; and  AAhether  the  AA'eather  is 
Avindy  or  calm.  Most  of  these  variations  are  entirely  beyond  the  baker’s 
control.  It  may  be  suggested  that  the  baker  should  AAeigh  the  bread  at 
the  time  of  delivery,  and  make  up  the  AA^eight  to  a standard,  or  charge  for 
actual  Aveight  delivered.  Except  in  tlie  very  poorest  districts,  bread  is  noAV 
deliA^ered  by  the  baker  at  tlie  buyer’s  house.  Purchasers  aauII  not,  hoAA^ever, 
tolerate  bread  being  AA'eiglied  on  delivery  at  their  houses  ; and  further,  the 
A^ariations  in  Aveight  referred  to  are  not  of  nutritive  solids  but  of  AAater  only. 
Tliere  is  tlie  curious  anomaly  that  a baker  may  start  from  his  shop  AAuth  tAA'o 


THE  WEIGHING  OF  BREAD. 


579 


loaves  in  liis  van,  both  of  the  same  weight,  and  over  the  standard  weight ; 
one  he  delivers  immediately  and  it  complies  with  the  law.  The  second  is 
taken  for  perhaps  two  miles  at  the  baker's  expense  and  is  then  sold  at  the 
same  price  as  the  first.  Through  natural  evaporation,  this  second  loaf  has 
become  of  light  weight,  and  its  sale  constitutes  an  offence,  though  the  nutri- 
tive value  is  the  same  and  the  loss  has  occurred  during  its  gratuitous  car- 
riage by  the  baker  for  the  convenience  of  his  customer.  Another  suggested 
remedy  is  that  the  baker  should  make  the  whole  of  his  loaves  sufficiently 
over  weight  to  provide  against  all  contingencies  of  loss  by  evaporation. 
But  as  put  so  cogently  in  the  Report  of  the  Select  Committee,  1821,  if  the 
baker  adopt  this  course,  “ his  price  being  fixed  upon  the  minimum  of  weight 
among  the  loaves  of  the  batch,  he  must  lose  his  profit  upon  the  average  of 
loaves,  or  sell  at  a rate  above  the  prevailing  prices,  which  would  be  the 
means  of  losing  his  customers." 

As  the  law  at  present  stands,  the  baker  has  but  little  option  other 
than  to  weigh  his  dough  at  a sufficient  weight  to  cover  all  ordinary  loss  by 
evaporation,  and  take  the  risk  of  any  extra  decrease  in  weight  arising 
from  abnormal  escape  of  moisture  due  to  unavoidable  causes. 

680.  London  County  Council  Bread  Bill,  1905. — In  1905  the  London 
County  Council  promoted  a Bill  in  Parliament  to  amend  the  law  relating 
to  the  sale  of  Bread  in  the  County  of  London.  The  operative  sections  of 
the  Bill  were  the  following  : — 

4.  Section  3 (Bakers  to  make  bread  of  any  weight  or  size)  and  Sec- 
tion 4 (Bread  to  be  sold  by  weight  and  in  no  other  manner  under  penalty 
not  exceeding  forty  shillings  not  to  extend  to  French  or  fancy  bread 
or  rolls)  of  the  principal  Act  and  Section  32  (Explanation  of  law  as 
to  bakers)  of  “ The  Weights  and  Measures  Act,  1889,"  shall  cease 
to  apply  or  have  any  effect  within  the  County. 

5.  All  bread  sold  within  the  County  shall  be  sold  by  weight  and  not 
otherwise,  and  shall  be  sold  only  in  loaves,  the  weight  of  each  of  which  is 
one  imperial  pound,  or  any  greater  weight  being  a complete  number  of 
imperial  pounds. 

The  principal  Act,  above  referred  to,  is  the  Bread  Act  of  3 George 
IV.,  c.  106,  1822.  The  object  of  the  bill  was  to  enforce  the  selling  of  bread 
in  loaves  of  exact  weight,  such  weight  being  one  or  any  other  complete 
number  of  imperial  pounds.  The  bill  was  opposed  by  various  organisa- 
tions representing  sections  of  the  Baking  Trade.  As  expressed  in  Petition 
against  the  Bill,  among  the  grounds  of  opposition  were  the  following  : — 

“ The  public  require  and  demand,  and  in  compliance  with  such 
demand  are  now  supplied  with,  bread  made  into  loaves  of  kinds  and 
weights,  to  supply  which  is  rendered  a penal  offence  by  the  Bill  ; 

“ The  provisions  of  the  Bill  are  such  that  from  the  very  nature  of 
bread,  and  the  processes  of  its  manufacture,  it  is  physically  impossible 
to  comply  therewith." 

Tlie  Bill  was  referred  to  a Committee  of  the  House  of  Commons.  In 
support  of  the  opposition,  evidence  was  given  that  on  one  day  a baker  may 
put  into  the  oven  two  pieces  of  dough  made  in  the  same  way  and  of  pre- 
cisely the  same  weight,  and  yet  there  may  be  a difference  of  quite  2 ozs. 
in  the  two  loaves  as  the  result  of  the  baking.  An  interesting  piece  of  evidence 
was  given  by  Mr.  Geo.  Wallace,  for  ten  years  head  manager  to  Messrs. 
Callard,  Stewart  & Watts,  who  produced  the  following  table  showing 
the  variation  in  crusty  loaves  baked  by  him  and  the  loss  in  weight  of  loaves 
after  12  and  24  hours. 


580 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  1.  4 Household  loaves  ; total  weight  : 

Lost  when  baked  : 10  ozs. 

,,  at  12  hours  : 13  ozs. 

,,  at  24  hours  : 14 J ozs. 

No.  2.  Long  loaf  : 2 lbs.  6 ozs. 

Lost  when  baked  : 9|  ozs. 

,,  at  12  hours  : lOJ  ozs. 

,,  at  24  hours  : lOJ  ozs. 

No.  3.  Long  loaf  : 2 lbs.  2 ozs. 

Lost  when  baked  : 5 ozs. 

,,  at  12  hours  : 5J  ozs. 

,,  at  24  hours  : 6 ozs. 

No.  4.  Crusty  Cottage  : 2 lbs.  2 ozs. 

Lost  when  baked  : 3J  ozs. 

,,  at  12  hours  : 4|  ozs. 

,,  at  24  hours  : 5 ozs. 

No.  5.  Soft  baked  Cottage  : 2 lbs.  2 ozs. 

Lost  when  baked  : 2 ozs. 

,,  at  12  hours  : 2f  ozs. 

,,  at  24  hours  : 3 ozs. 

No.  6.  Crusty  loaf  (occasionally  ordered)  : 

Lost  when  baked  : 5 ozs. 

,,  at  12  hours  : ozs. 

,,  at  24  hours  : 6 ozs. 

No.  7.  Coburg  loaf  : 2 lbs.  2 ozs. 

Lost  when  baked  : 3J  ozs. 

,,  at  12  hours  : 4 ozs. 

,,  at  24  hours  : 4J  ozs. 

No.  8.  Rasped  tin  loaf  : 2 lbs.  2 ozs. 

Lost  when  baked  : 4 ozs. 

,,  ,,  trimmed  : 5J  ozs. 

,,  at  12  hours  : 6J  ozs. 

,,  at  24  hours  : ozs. 

No.  9.  Brick  loaf  : 2 lbs.  2 ozs 

Lost  when  baked  : 2 ozi. 

,,  at  12  hours  : 3 ozs. 

,,  at  24  hours  : 3J  ozs. 


8 lbs.  12  ozs. 


2 lbs.  2 ozs. 


In  reply  to  Counsel,  the  witness  explained  as  the  net  result  that  there 
is  at  least  a margin  of  8 ozs.  in  loaves  baked  at  the  same  time  and  under  the 
same  conditions.  He  produced  a long  French  loaf  which  went  into  the 
oven  at  2 lbs.  6 ozs.,  and  which  lost  9|  ozs.  in  the  baking.  That  was  the 
ordinary  depreciation  in  weight  with  the  ordinary  methods  of  baking.  It 
was  not  baked  in  any  way  different  from  the  ordinary  course  of  trade. 
Evidence  was  also  given  that  there  is  a demand  on  the  part  of  the  public 
for  loaves  between  1 lb.  and  2 lbs.  in  weight. 

After  hearing  evidence,  and  speeches  of  Counsel  on  both  sides,  the  Com- 
mittee decided  that  the  preamble  had  not  been  proved,  and  accordingly 
threw  out  the  Bill. 

The  law  therefore  stands  at  present  unchanged,  and  while  the  baker  is 
compelled  to  sell  by  weight,  that  weight  may  be  any  quantity  decided  on  by 
the  seller,  and  acceptable  by  the  purchaser. 


CHAPTER  XXIII. 


BAKEHOUSE  DESIGN. 

681.  Selection  of  Site. — In  determining  the  site  for  a bakery,  one  of  the 
first  matters  to  engage  attention  should  be  to  select  a locality  suitable 
from  a commercial  point  of  view.  A practical  baker  would  at  once 
satisfy  himself  whether  or  not  a neighbourhood  looked  as  though  it  were 
growing  and  improving,  or  the  reverse  ; whether  it  was  already  over- 
stocked with  bakeries,  or  whether  there  were  still  openings  ; whether 
full  prices  were  being  obtained,  or  whether  the  locality  was  an  undercutting 
one.  The  nature  of  the  roads,  whether  hilly  or  level,  and  all  items  bearing 
on  the  cost  of  getting  flour  into  the  bakehouse  and  of  delivering  bread  from 
the  bakehouse,  would  be  duly  noted,  and  the  proper  weight  given  to  them 
in  forming  a judgment  as  to  the  suitability  of  the  spot.  All  these  may 
fairly  be  termed  commercial  aspects  of  the  question  ; but  beyond  these 
there  are  considerations  which  are  more  intimately  associated  with  the 
practical  necessities  of  bread-making. 

Among  these  a leading  place  must  be  given  to  the  degree  of  fresh  air 
obtainable,  and  general  hygienic  surroundings.  The  situations  best  adapted 
for  selling  bread  are  not  necessarily  those  also  best  suited  for  making  the 
same.  A good  shop  will  be  naturally  where  rents  rule  high  and  property  is 
valuable  ; as  a result,  baking  operations  are  of  necessity  frequently 
conducted  in  a far  too  limited  space  for  the  most  efflcient  and  healthy  work- 
ing. In  consequence,  the  system  of  having  bakeries  in  more  thinly  popu- 
lated districts,  where  land  is  less  valuable  and  a building  capacious  enough  to 
accommodate  modern  labour-saving  plant  can  be  erected,  and  using  the  shops 
as  selling  places  only,  is  being  more  and  more  adopted.  With  large  Arms 
having  abundance  of  capital  this  is  comparatively  easily  managed,  but  in 
the  case  of  smaller  concerns  greater  difficulty  exists.  But  except  where  really 
good  bakehouses  are  actually  in  use,  it  is  a matter  for  serious  consideration 
whether  the  bakehouse  should  not  be  altogether  distinct  from  the  shop. 
However  crowded  a locality,  there  may  generally  be  found  at  a not  unwork- 
able distance  a site  where  a bakehouse,  pure  and  simple,  may  be  erected. 
The  bread  rounds  may  be  served  direct  from  where  the  bread  is  baked, 
and  only  those  goods  brought  to  the  shop  which  are  requisite  for  a counter 
trade.  The  difficulty  is  that  this  means  two  places  to  be  supervised  instead 
of  one  ; but  even  when  under  the  same  roof  the  bakehouse  is  absolutely 
distinct  from  the  shop,  and  the  hours  of  work  are  by  no  means  simultaneous. 
By  the  use  of  the  telephone,  communication  betAveen  the  two  becomes  such 
that  orders  and  messages  may  be  readily  transmitted.  Granted  that 
arrangements  of  this  kind  mean  extra  expense,  still  in  the  matter  of  hygienic 
requirements  the  public  is  master,  and  will  in  the  long  run  insist,  in  no 
uncertain  manner,  upon  bread-making  being  carried  on  under  satisfactory 
sanitary  conditions,  and  the  trader  Avho  keeps  ahead  of  time,  reaps  a hand- 
some reward  for  his  enterprise. 

There  is  no  doubt  that  a bakery  on  the  ground  floor  has  a far  better 
chance  than  one  situated  underground.  Xo  one  more  thoroughly  recog- 
nises than  the  authors  the  difficulties,  in  many  cases,  of  finding  in  old  bakers* 

581 


582 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


shops  accommodation  for  the  bakehouse  other  than  below  the  shop,  and 
also  that  many  bakeries  exist  below  the  street  level,  and  are  yet  clean  and 
healthy  ; but  it  is  in  spite  of  their  situation,  and  not  because  of  it,  that 
they  are  thus  clean.  To  keep  them  so  requires  far  more  effort  and  attention 
than  when  they  are  above  ground.  When  a new  building  is  being  erected, 
it  may  frequently  be  an  advantage  to  have  a sloping  site,  thus  permitting 
two  approaches  on  different  floor  levels  ; this,  however,  is  not  often  obtain- 
able. It  may  further  mean  that  the  district  is  hilly  and,  so,  difficult  for 
the  delivery  of  bread.  The  site  should  be  dry  and  well  drained  ; also  well 
ventilated,  but  sheltered  as  far  as  possible  from  exposure  to  cold  winds, 
especially  on  the  north  and  east  sides.  The  top  of  a hill  has  advantage 
over  the  bottom  for  the  delivery  of  bread,  inasmuch  as  the  full  vans  have 
a downhill  journey. 

682.  Underground  Bakehouses. — The  Factory  Act  of  1901  contains 
some  most  important  provisions  as  to  underground  bakehouses,  among 
which  occur  the  following  : — 

S.  lOI. — (I)  An  underground  bakehouse  shall  not  be  used  as  a bake- 
house unless  it  was  so  used  at  the  passing  of  this  Act. 

(2)  Subject  to  the  foregoing  provision,  after  the  first  day  of  January, 
One  thousand  nine  hundred  and  four,  an  underground  bakehouse  shall 
not  be  used  unless  certified  by  the  district  council  to  be  suitable  for  that 
purpose. 

(3)  For  the  purpose  of  this  section  an  underground  bakehouse  shall 
mean  a bakehouse,  any  baking  room  of  which  is  so  situate  that  the 
surface  of  the  floor  is  more  than  three  feet  below  the  surface  of  the 
footway  of  the  adjoining  street,  or  of  the  ground  adjoining  or  nearest 
to  the  room.  The  expression  “ baking  room  ""  means  any  room  used 
for  baking,  or  for  any  process  incidental  thereto. 

(4)  An  underground  bakehouse  shall  not  be  certified  as  suitable 
unless  the  district  council  is  satisfied  that  it  is  suitable  as  regards 
construction,  light,  ventilation,  and  in  all  other  respects. 

The  first  sub-section  prohibits  the  use  of  an  underground  bakehouse 
as  such  unless  it  was  so  used  at  the  passing  of  this  Act,  that  date  for  this 
purpose  being  taken  as  January  1,  1902.  The  evident  object  of  the 
legislature  is  to  discourage  such  bakehouses,  and  while  forbidding  the  use, 
and  as  a consequence  the  erection,  of  new  underground  bakehouses,  its 
general  effect  tends  to  the  gradual  extinction  of  those  already  in  existence. 
Sub-section  3 defines  an  underground  bakehouse,  and  provides  that  if  in 
any  bakehouse  any  baking  room  has  the  surface  of  its  floor  more  than  threo 
feet  below  (1)  the  surface  of  the  footway  of  the  adjoining  street,  or  (2)  of 
the  ground  adjoining  or  nearest  to  the  room,  such  bakehouse  shall  be  re- 
garded as  an  underground  bakehouse.  The  simplest  possible  case  is  that 
which  falls  within  clause  1,  which  applies  to  any  bakehouse  which  abuts 
directly  on  the  footway  without  any  intervening  area  or  air-space.  Under 
these  circumstances  there  is  no  doubt  that  if  the  floor  of  the  bakehouse  is 
more  than  three  feet  below  the  surface  of  the  adjoining  footway,  the  bake- 
house is  included  within  the  definition  as  being  underground.  A more 
difficult  case  arises  where  there  is  an  area  between  the  bakehouse  and  the 
footway.  In  the  construction  of  basement  houses  it  is  not  an  uncommon 
occurrence  to  find  the  ground  floor  level  with,  or  just  higher  than,  the  surface, 
of  the  street  ; the  front  area  being  excavated  to  the  level  of  the  underground 
floor  or  basement.  Any  rooms  in  such  basement  then  look  out,  and  pos- 
sibly open  out,  on  a small  yard  level  with  themselves,  and  having  a wall  on 
tlie  side  opposite  to  the  basement-room,  formed  by  the  face  of  the  excavated 
area  where  it  adjoins  the  street.  If  such  a room  be  used  as  a bakehouse. 


BAKEHOUSE  DESIGN. 


583 


then  clause  (1)  cannot  apply,  because  there  is  no  adjoining  street  ; it  is 
further  submitted  that  clause  (2)  does  not  cause  such  a bakehouse  to  become 
an  underground  bakehouse,  because  the  ground  adjoining,  the  yard  or 
area,  is  not  above  the  level  of  the  bakehouse,  and  further  that  is  the  ground 
which  is  nearest  to  the  baking  room.  Another  case  may  arise  where  a house 
or  terrace  of  houses  is  built  on  the  side  of  a hill.  Such  houses  may  open  on 
the  front  to  one  street,  and  on  the  back  to  another,  between  which  two 
streets  there  may  be  a difference  of  level  of  several  feet,  say  for  the  present 
purpose  more  than  three  feet.  Taking  the  lower  level  street  of  the  two,  a 
house  may  be  built  with  its  lowest  floor,  level  with  this  street,  and  the  rooms 
on  this  floor  opening  out  on  and  receiving  light  and  air  from  this  lower  level 
street.  The  back  of  such  room  will  abut  on  the  ground  of  the  high  level 
street,  and  its  floor  will  be  more  than  three  feet  below  the  ground  adjoining 
the  room.  If  such  a room  be  used  as  a bakehouse  should  it  be  regarded  as 
being  underground  ? It  is  submitted  that  it  should  not.  Clearly  in  the 
case  of  a room  which  is  on  a level  piece  of  ground,  with  windows  and  door 
on  the  one  side  only  and  the  other  three  sides  blank  walls,  there  is  no  doubt 
that  it  would  not  be  regarded  as  an  underground  bakehouse.  Assuming 
that  the  walls  are  impermeable  to  damp,  it  is  equally  clear  that  an  alteration 
of  the  level  of  the  ground  adjoining  the  hack  wall  would  not  in  the  slightest 
degree  affect  the  sanitary  condition  of  the  room  itself,  nor  the  question  of 
the  relation  of  its  level  to  that  of  the  street  or  space  from  which  it  receives 
light  and  air.  In  the  case  of  any  bakehouse  built  on  a sloping  site,  with  its 
entrance,  windows,  doors,  and  other  means  of  ventilation  opening  on  and 
adjoining  ground  which  is  level  with  the  surface  of  the  floor,  it  is  submitted 
that  such  ground  should,  for  the  purposes  of  this  section,  be  regarded  as 
that  which  is  adjoining  or  nearest  to  the  room.  Any  rising  ground  which 
is  at  the  back  or  sides,  and  which  is  separated  from  the  interior  of  the  bake- 
house by  a blank  wall,  should  be  regarded  as  the  more  remote  in  point  of 
actual  distance,  as  well  as  being  absolutely  distinct  and  apart  from  the 
bakehouse  so  far  as  all  questions  of  sanitation  are  affected.  An  explanation 
is  further  given  as  to  what  is  meant  by  “ baking  room,'’  which  phrase  in- 
cludes any  room  used  for  baking,  or  for  any  process  incidental  thereto. 
A question  arises  as  to  what  may  be  regarded  as  incidental.  A “ sponge  ” 
room  or  room  where  any  part  of  the  manufacturing  operation  is  conducted 
would  no  doubt  be  viewed  as  included  by  the  definition  in  “ baking  room.” 
But  as  the  storage  of  flour  or  other  raw  material,  and  of  bread  after  the 
completion  of  baking  and  during  the  cooling  stage,  is  not  in  any  way  a pro- 
cess incidental  to  baking,  the  fact  of  rooms  being  used  for  these  purposes 
v'ould  not  make  them  baking  rooms,  nor  consequently  the  bakehouse  an 
underground  bakehouse. 

683.  Requirements  for  Underground  Bakehouses  Formulated  by  Med’cal 
Officers  of  Health. — The  fourth  sub-section  provides  that  the  district  council 
shall  not  certify  an  underground  bakehouse  as  suitable  unless  it  is  satisfied 
that  it  is  suitable  as  regards  construction,  light,  ventilation,  and  all  other 
respects.  In  view  of  the  fact  that  the  medical  officers  of  health  are  the 
advisers  of  district  councils  in  sanitary  matters,  and  are  also  appointed 
executive  officers  under  the  Act  in  a subsequent  section,  the  “ Incorporated 
Society  of  Medical  Officers  of  Health  ” gave  the  whole  subject  their  careful 
consideration  and  drew  up  a series  of  suggestions  ” for  the  guidance  of 
medical  officers  of  health  in  advising  their  sanitary  authorities  as  to  require- 
ments that  may  be  needed  under  the  Act.  One  of  their  objects  in  so 
doing  was  to  secure  uniformity  of  action  throughout  the  country.  The 
following  is  a copy  of  their  memorandum  ; — 


584 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

Suggested  Requirements  for  Underground  Bakehouses.’' 

A.  Construction, 

(1)  No  underground  bakehouse  shall  be  less  than  eight  feet  in  height 
throughout,  measured  from  the  floor  vertically  to  the  ceiling  ; and 
in  case  the  floor  area  exceeds  300  square  feet,  such  height  shall  be  at 
least  8 feet  6 inches. 

(2)  No  underground  bakehouse  shall  have  a cubic  capacity,  clear  of 
the  oven,  of  less  than  1,500  feet. 

(3)  The  floor  shall  be  constructed  of  hard,  smooth,  durable,  and 
impervious  material. 

(4)  The  walls  shall  be  constructed  of  a material  which  is  hard, 
smooth,  durable,  and  impervious  to  damp. 

Note, — Where  adjacent  ground  abuts  on  a wall,  or  walls,  such 
walls  should  be  lined  with  the  best  glazed  bricks,  uniformly  jointed 
with  Portland  cement,  to  form  internal  walls,  separated  from  the 
intervening  existing  walls  by  a cavity  and  bonded  to  them,  the  space 
being  ventilated  to  the  outer  air. 

(5)  The  ceiling  shall  be  even,  impermeable  to  damp  and  dust,  and 
durable. 

(6)  Every  underground  bakehouse  shall  be  approached  by  a suitable 
staircase,  adequately  lighted  and  ventilated. 

No  outside  staircase  shall  terminate  within  an  underground  bake- 
house. Any  opening  into  the  shop  above  must  be  so  covered  as  to 
prevent  the  entrance  of  dust. 

B.  Light. 

(7)  The  underground  bakehouse  shall  be  adequately  lighted  with 
daylight  throughout  to  the  satisfaction  of  the  sanitary  authority,  and 
the  lighting  maintained  shall  be  such  that  an  Official  Copy  of  the 
Abstract  of  the  Factory  Acts  may  ordinarily  be  read  in  all  parts  of  such 
bakehouse,  between  the  hours  of  11  a.m.  and  3 p.m. 

C.  Ventilation. 

(8)  Ventilation  shall  be  so  arranged  that  the  circulation  of  air  is 
-confined  to  the  underground  bakehouse. 

(9)  Ventilation  shall  be  adequate,  that  is  to  say,  fresh  clean  air  shall 
be  supplied  constantly  during  working  hours,  so  as  to  provide  not  less 
than  3,000  cubic  feet  of  air  per  hour  for  each  person  employed,  with 
any  additional  amount  required  for  purposes  of  combustion,  in  such 
a manner  as  to  avoid  the  occurrence  of  draught,  and  so  that  the  air  is 
sufficiently  renewed  in  all  parts  of  the  underground  bakehouse  ; and 
by  the  aid  of  mechanical  power,  when,  in  the  opinion  of  the  medical 
officer  of  health,  such  is  necessary. 

Provision  shall  be  made  for  the  removal  of  steam  from  the  under- 
ground bakehouse.  ,/ 

Wliere  mechanicav  power  is  used,  the  fresh  air  shall  be  taken  from  a 
height  above  the  level  of  the  adjoining  ground,  of  not  less  than  6 feet, 
and  be  distributed  to  different  parts  of  the  underground  bakehouse 
in  such  a manner  as  to  change  the  air  of  such  bakehouse  in  all  parts. 

Note. — This  will  generally  require  the  provision  of  a fan.  Foul  air 
may  also  be  extracted  by  means  of  a fan,  with  any  aid  available 
from  gas  and  ventilating  shafts. 

(10)  Arrangements  for  ventilation  shall  be  such  that  the  temperature 
of  the  underground  bakehouse  from  October  1 to  May  31  shall  not 


BAKEHOUSE  DESIGN.  585 

exceed  80°  F.,  except  within  half  an  hour  after  a batch  of  bread  has 
been  drawn. 

D.  All  other  respects. 

(11)  Proper  provision  shall  be  made  for  the  storage  of  flour  elsewhere 
than  in  the  underground  bakehouse  itself. 

(12)  There  shall  be  no  opening  into  the  underground  bakehouse  for 
any  purpose  which  will  tend  unduly  to  the  admission  of  dust  from  the 
adjoining  street. 

(13)  Conveniences  for  personal  ablution  shall  be  provided  in  a suit- 
able position,  and  shall  include  a water  tap  and  a sink  or  lavatory  basin 
of  an  approved  character. 

Note. — These  conveniences  should  be  outside  the  underground 

bakehouse. 

Free  access  shall  be  provided  to  suitable  sanitary  conveniences 

suitably  situated. 

(14)  All  troughs,  tables,  or  other  furniture  standing  on  the  floor  of 
the  underground  bakehouse  shall  be  provided  with  strong  ball-bearing 
castors. 

(15)  Proper  provision  shall  be  made  for  the  depositing  of  wearing 
apparel  outside  the  underground  bakehouse. 

• (16)  An  underground  bakehouse  shall  not  be  in  communication 

with  a washhouse,  nor  with  any  room,  cellar,  or  area  containing  ob- 
jectionable materials. 

(17)  An  underground  room,  not  entirely  separated  from  the  under- 
ground bakehouse,  shall  be  well  lighted  throughout,  shall  be  suffi- 
ciently protected  against  the  entrance  of  ground  air,  shall  be  properly 
ventilated,  and  shall  be  at  all  times  clean. 

(18)  All  statutory  obligations  shall  be  fulfilled. 

(19)  Before  making  any  alterations  with  a view  to  meeting  these 
requirements,  the  owners  or  occupiers  of  underground  bakehouses  shall 
submit  to  the  sanitary  authority  a specification  (and  plans)  of  the 
alterations  which  they  propose  making.” 

This  memorandum  of  suggested  requirements  formed  the  basis  of  most 
local  regulations,  and  resulted  in  such  being  framed  throughout  the  country 
in  much  the  same  spirit.  It  has  the  additional  advantage  of  throwing  light  on 
what  would  be  regarded  by  tlie  sanitary  authorities  as  the  minimum  require- 
ments in  bakehouses  generally. 

684.  Requirements  in  the  Building. — These  will  be  best  grouped  under 
warious  headings,  each  of  which  will  be  considered  in  turn. 

The  following  general  conditions  should,  however,  be  borne  in  mind  in 
connection  with  all  that  follows,  and  especially  in  reference  to  the  descrip- 
tion of  t3rpical  bakehouses  illustrated. 

Floors. — Many  different  types  of  floors  have  been  tried,  but  it  may  be 
accepted  that  the  best  plan  is  to  select  some  type  of  flagged  or  tiled  floor. 
Owing  to  heavy  traffic  certain  parts  of  the  floors  '^^ear  more  than  others,  and 
no  homogeneous  flooring  material  that  will  lend  itself  to  efficient  repair  in 
selected  places  has  yet  stood  the  test  of  hard  work.  The  heat  in  bakehouses, 
together  with  the  short  time  during  which  repair  work  can  be  permitted, 
constitute  the  great  difficulties  in  this  respect.  It  is  obvious  therefore  that 
stone  flagging,  artificial  stone  slabs,  tiles  or  hard  bricks,  which  can  all  be 
readily  removed  in  worn  places,  and  relaid  efficiently  without  interruption 
to  work  or  fear  of  break  up,  form  the  ideal  materials  for  a bakehouse  floor. 
In  certain  factories  where  the  wear  is  very  heavy,  floors  have  been  introduced 
with  a surface  of  cast-iron  plates  with  hexagonal  honeycomb  perforations. 


586  THE  TECHNOLOGY  OE  BREAD-MAKING. 

The  plates  are  laid  on  cement  and  the  holes  filled  with  cement  to  the  upper 
surface. 

Walls  and  Ceiling. — These  should  preferably  be  of  washable  material 
(glazed  bricks,  parian  cement,  tiles  or  the  like)  ; all  piers  should  be  outside 
the  building  ; only  plain  surfaces  should  be  used  inside  and  no  sharp  corners 
should  be  employed.  Thus,  the  walls  should  join  one  another,  the  ceiling 
or  the  floor,  by  a rounded  corner  with  a radius  of  at  least  one  inch.  Where 
considerations  of  expense  make  such  perfection  impossible,  plain  brickwork 
walls,  kept  well  lime-washed,  are  the  only  alternative  which  can  be  recom- 
mended. Upper  floors  should  preferably  be  ferrc -concrete  with  girders 
and  joists  cased  in  cement,  again  avoiding  all  sharp  corners. 

Windows  and  Doors  should  be  placed  to  avoid  draughts  as  far  as  possible 
they  should  be  well  fitting,  especially  on  walls  exposed  to  strong  winds. 
Sloping  window  sills  are  advisable,  as  they  prevent  the  accumulation  of 
dust  and  cannot  be  used  for  the  storage  of  odds  and  ends,  which  are  not 
only  objectionable,  but  are  often  the  cause  of  broken  windows. 

Chimneys  should  never  be  less  than  9 in.  x 9 in.,  measured  interneJly,  and 
should  run  up  outside  main  walls  to  above  the  ridge  of  roof  or  highest 
building  adjoining.  Avoid  cowls  and  horizontal  connections,  and  never  put 
a round  chimney  pot  on  a square  chimney  unless  its  diameter  equals  the 
diagonal  of  the  square  chimney  section.  One  chimney  to  take  a number  of 
ovens  is  quite  satisfactory  if  large  enough  and  properly  arranged,  but  often 
a number  of  smaller  ones  is  less  costly. 

Roofs  should  exclude  draughts  as  well  as  wet.  If  fitted  with  ventilators, 
these  should  have  means  for  control.  Avoid  too  much  glass  roofing  over 
the  actual  doughing  room  and  bakery  (in  such  cases  where  there  is  no  floor 
over)  : it  is  too  hot  in  the  summer  and  too  cold  in  the  winter. 

General. — Avoid  fixtures  as  far  as  possible  ; let  all  tables,  troughs,  bread 
racks  and  fittings  be  on  castors  or  wheels  to  facilitate  transportation  and 
cleanliness. 

Motive  Poiver. — Gas  engines  are  shown  in  some  of  the  plans  on  account 
of  their  being  the  most  usually  available  source  of  power,  and  also  the  heavi- 
est and  most  difficult  to  accommodate,  thus  showing  that  lighter  or 
smaller  prime-movers  will  have  ample  room.  Space  and  often  expense  will  of 
course  be  saved  by  adopting  electric  motors  where  current  is  available. 
The  subject  of  motive  power  is  fully  dealt  with  in  paragraphs  705  to  711. 

685,  Sanitation. — Among  Bakehouse  requirements,  those  of  most  vital  im- 
portance are  demanded  for  sanitary  purposes.  The  various  Factory  Acts  lay 
down  a minimum  in  this  direction  which  by  law  is  made  compulsory.  It  will 
be  well  here  to  examine  these  somewhat  in  detail,  so  far  at  least  as  they  affect 
the  question  of  actual  design  as  distinguished  from  precautions  in  after  use 
of  the  bakery.  The  quotations  following  are  from  the  Act  of  1901,  and 
the  word  “ bakehouse,""  in  brackets,  [ ],  is  substituted  for  “ factory  or 
workshop  ""  wherever  bakehouses  are  obviously  included  in  that  phrase. 

Space  and  Ventilation  are  dealt  with  in  Section  1 : — 

S.  1. — (1)  (d)  It  [the  bakehouse]  must  be  ventilated  in  such  a man- 
ner as  to  render  harmless,  so  far  as  is  practicable,  all  the  gases,  vapours, 
dust,  or  other  impurities  generated  in  the  course  of  the  manufacturing 
process  or  handicraft  carried  on  therein,  that  may  be  injurious  to  health. 
The  provisions  for  ventilation  usually  found  in  a bakehouse  are  sufficient 
to  meet  the  requirements  of  the  Act.  But  it  should  be  remembered  that 
wliere  considered  insufficient,  power  is  given  to  compel  efficient  ventilation. 
S.  3. — (1)  A [bakehouse]  shall  be  deemed  to  be  so  overcrowded  as 
to  be  dangerous  or  injurious  to  the  health  of  the  persons  employed 
therein,  if  the  number  of  cubic  feet  of  space  in  any  room  therein  bears 


BAKEHOUSE  DESIGN. 


587 


to  the  number  of  persons  employed  at  one  time  in  the  room  a proportion 
less  than  two  hundred  and  fifty,  or,  during  any  period  of  overtime, 
four  hundred,  cubic  feet  of  space  to  every  person. 

(2)  Provided  that  the  Secretary  of  State  may,  by  Special  Order, 
modify  this  proportion  for  any  period  during  which  artificial  light  other 
than  electric  light  is  employed  for  illuminating  purposes,  and  may  by 
like  order,  as  regards  any  particular  manufacturing  process  or  handi- 
craft, substitute  for  the  said  figures  of  two  hundred  and  fifty,  and  four 
hundred  respectively,  any  higher  figures,  and  thereupon  this  section 
shall  have  effect  as  modified  by  the  order. 

(4)  There  shall  be  affixed  in  every  [bakehouse]  a notice  specifying 
the  number  of  persons  who  may  be  employed  in  each  room  of  the 
[bakehouse]  by  virtue  of  this  section. 

The  work  in  a bakehouse  is  such  as  to  require  considerable  space  for  the 
ordinary  operations  of  manufacture,  and  therefore  there  is  as  a rule  an  ample 
margin  of  cubic  feet  of  space  for  the  workers. 

Sanitary  Accommodation  : — 

S.  9. — (1)  Every  [bakehouse]  must  be  provided  with  sufficient  and 
suitable  accommodation  in  the  way  of  sanitary  conveniences,  regard 
being  had  to  the  number  of  persons  employed  in,  or  in  attendance 
at,  the  [bakehouse],  and  also  where  persons  of  both  sexes  are,  or 
are  intended  to  be  employed  or  in  attendance,  with  proper  separate 
accommodation  for  persons  of  each  sex. 

It  should  be  noticed  that  the  Act  clearly  insists  on  the  provision  of 
adequate  sanitary  accommodation,  and  further  that  each  sex  shall  be  accom- 
modated separately. 

Sanitary  Provisions  : — 

S.  97. — (I)  It  shall  not  be  lawful  to  let  or  suffer  to  be  occupied,  or 
to  occupy  any  room  or  place  as  a bakehouse,  unless  the  following 
regulations  are  complied  with  : — 

(а)  A water-closet,  earth-closet,  privy,  or  ashpit  must  not  be  within 
or  communicate  directly  with  the  bakehouse. 

(б)  Every  cistern  for  supplying  water  to  the  bakehouse  must  be 
separate  and  distinct  from  any  cistern  for  supplying  water  to  a water- 
closet. 

(c)  A drain  or  pipe  for  carrying  of  faecal  or  sewage  matter  must  not 
have  an  opening  within  the  bakehouse. 

To  fulfil  the  first  of  these  conditions  closets  are  preferably  erected  in 
an  open  yard  where  an  air  space  intervenes  between  them  and  the  bakery. 
But  while,  theoretically,  it  may  be  good  designing  to  place  closets  and  urinals 
completely  away  from  the  bakehouse  with  a good  space  between,  we  are 
met  by  the  practical  difficulty  that  bakers  work  in  a warm  atmosphere,  and 
find  it  dangerous  to  freely  expose  themselves  suddenly  to  the  cold.  If  such 
accommodation  be  provided  too  far  away,  there  is  a danger  of  a nuisance 
being  created  by  the  improper  use  of  some  other  part  of  the  bakery  and  its 
surroundings.  A very  good  arrangement  is  that  in  which  a door  opens, 
preferably  from  the  stokehole  or  some  similar  part  of  the  building,  into  a 
small  yard,  with  a passage  intervening  between  the  closets  and  the  bake- 
house. By  a proper  system  of  roofing,  free  ventilation  is  secured,  while 
protection  is  afforded  from  rain  or  cold. 

In  some  of  the  best  fitted  bakeries,  dressing-rooms  are  provided  for  the 
workmen,  and  out  of  these  lead  lavatories,  bathrooms  and  closets,  with 
adequate  ventilating  provisions,  so  that  a current  of  air  leads  from  tlie 
bakery  towards  the  lavatories,  and  thus  out  of  the  building. 

The  second  condition,  which  applies  to  the  water  supply,  is  one  easily 


588 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


arranged  for.  As  a contingency  against  accidents,  bakeries  should  possess 
a water  cistern  holding  at  least  one  day’s  supply.  To  this  the  draw-off  for 
bakehouse  use  may  be  affixed  direct,  but  closets  should  be  supplied  with 
an  intervening  cistern,  sach  as  the  ball-cock  flush  cistern  now  seen  as  an 
almost  universal  accompaniment  to  the  closet. 

The  third  requirement,  as  to  drains  is  also  a matter,  the  necessity  of 
which  is  self-evident.  It  follows  from  it  that,  whether  trapped  or  not,  there 
should  be  no  direct  drain  communication  with  the  sewers.  All  drains 
within  the  bakehouse  should  be  carried  out  by  means  of  as  short  and  straight 
a pipe  as  possible  into  the  open,  and  there  allowed  to  pour  into  a trapped 
outside  drain.  It  is  not  advisable  even  to  place  a trap  in  this  short  length 
of  drain  ; for  wet  flour  and  dough  so  quickly  undergo  putrefaction,  that  no 
lodgment  should  be  permitted  for  them  by  even  the  simplest  of  traps. 

686.  Safety  from  Fire. — The  law  is  now  very  insistent  on  the  provision  of 
ample  means  of  escape  from  fire  in  the  case  of  every  factory  and  workshop  : — 

S.  14. — (1)  Every  factory  of  which  the  construction  was  not  com- 
menced on  or  before  the  1st  day  of  January,  One  thousand  eight  hundred 
and  ninety-two,  and  in  which  more  than  forty  persons  are  employed, 
and  every  workshop  of  which  the  construction  was  not  commenced 
before  the  1st  day  of  January,  One  thousand  eight  hundred  and  ninety- 
six,  and  in  which  more  than  forty  persons  are  employed,  must  be  fur- 
nished with  a certificate  from  the  district  council  of  the  district  in  which 
the  [bakehouse]  is  situate,  that  the  [bakehouse]  is  provided  with  such 
means  of  escape  in  case  of  fire  for  the  persons  employed  therein  as  can 
reasonably  be  required  under  the  circumstances  of  each  case. 

(2)  With  respect  to  all  [bakehouses]  to  which  the  foregoing  pro- 
visions of  this  section  do  not  apply,  and  in  which  more  than  forty  per- 
sons are  employed,  it  shall  be  the  duty  of  the  district  council  from 
time  to  time  to  ascertain  whether  all  such  [bakehouses]  within  their 
district  are  provided  with  such  means  of  escape  as  aforesaid,  and  in 
the  case  of  any  [bakehouse]  which  is  not  so  provided,  to  serve  on  the 
owner  of  the  [bakehouse]  a notice  in  writing,  specifying  the  measures 
necessary  for  providing  such  means  of  escape  as  aforesaid,  and  requiring 
him  to  carry  them  out  before  a specified  date,  and  thereupon  the  owner 
shall,  notwithstanding  any  agreement  with  the  occupier,  have  power 
to  take  such  steps  as  are  necessary  for  complying  with  the  requirements, 
and  unless  the  requirements  are  complied  with,  the  owner  shall  be 
liable  to  a fine  not  exceeding  one  pound  for  every  day  that  the  non- 
compliance  continues. 

(6)  The  means  of  escape  in  case  of  fire  provided  in  any  [bakehouse] 
shall  be  maintained  in  good  condition  and  free  from  obstruction. 

S.  15. — Every  district  council  shall  . . . have  power  to  make  bye- 
laws providing  for  means  of  escape  from  fire  in  the  case  of  any  [bake- 
house]. 

S.  16. — (1)  While  any  person  employed  in  a [bakehouse]  is  within 
the  [bakehouse]  for  the  purpose  of  employment  or  meals,  the  doors  of 
the  [bakehouse]  and  of  any  room  therein  in  which  any  such  person  is, 
must  not  be  locked  or  bolted  or  fastened  in  such  a manner  that  they 
cannot  be  easily  and  immediately  opened  from  the  inside. 

(2 ) In  every  [bakehouse]  the  construction  of  which  was  not  commenced 
before  the  1st  day  of  January,  One  thousand  eight  hundred  and  ninety- 
six,  the  doors  of  each  room  in  which  more  persons  than  ten  are  employed 
shall,  except  in  the  case  of  sliding  doors,  be  constructed  so  as  to  open 
outwards. 

A duty  is  thrown  on  the  district  council  to  see  that  adequate  means  of 


BAKEHOUSE  DESIGN  589 

escape  from  fire  are  provided  apd  kept  in  a state  of  efficiency.  The  owner, 
not  the  occupier,  is  the  person  liable  for  their  provision. 

Provision  for  escape  from  fire  is  generally  in  the  form  of  iron  staircases 
run  outside  the  building.  These  should  be  of  as  easy  gradient  as  possible, 
with  frequent  landings,  and  adequately  protected  by  an  ample  and  strong 
outer  rail.  The  doors  leading  to  these  staircases  should  open  outwards 
and  be  capable  of  immediate  and  ready  unfastening.  Steps  leading  up 
to  them  or  other  possible  forms  of  obstruction  in  case  of  panic  should  be 
carefully  avoided. 

687.  Fencing  of  Machinery. — The  provisions  of  the  Act  also  include 
considerations  of  safety  from  contact  with  machinery  in  motion. 

S.  10. — (1)  With  respect  to  the  fencing  of  machinery  in  a factory  the 
following  provisions  shall  have  effect  : — 

{a)  Every  hoist  or  teagle,  and  every  fiy-wheel  directly  connected 
with  the  steam  or  water  or  other  mechanical  power,  whether  in  the 
engine-house  or  not,  and  every  part  of  any  water-wheel  or  engine 
worked  by  any  such  power,  must  be  securely  fenced  ; and 

(b)  Every  Avheel-race  not  otherwise  secured  must  be  securely 
fenced  close  to  the  edge  of  the  wheel-race  ; and 

(c)  All  dangerous  parts  of  the  machinery,  and  every  part  of  the 
mill-gearing,  must  either  be  securely  fenced,  or  be  in  such  position  or 
of  such  construction  as  to  be  equally  safe  to  every  person  employed 
or  working  in  the  factory  as  it  would  be  if  it  were  securely  fenced  ; 
and 

{d)  All  fencing  must  be  constantly  maintained  in  an  efficient  state 
while  the  parts  required  to  be  fenced  are  in  motion  or  use,  except  where 
they  are  under  repair  or  under  examination  in  connection  with 
repair,  or  are  necessarily  exposed  for  the  purpose  of  cleaning  or 
lubricating,  or  for  altering  the  gearing  or  arrangements  of  the  parts 
of  the  machine. 

Mill-gearing  comprehends  every  shaft,  wheel,  drum  or  pulley  by  which 
the  motion  of  the  first  driving  power  is  communicated  to  any  machine 
appertaining  to  a manufacturing  process.  Machinery  includes  any  driving 
strap  or  band.  These  provisions  are  so  plain  that  little  or  no  explanatory 
comment  is  needed.  Most  of  the  bakery  mill-gearing  where  machinery  is 
employed  is  fixed  overhead,  so  that  it  is  perfectly  safe.  Where  belts  pass 
through  the  floor,  or  come  down  from  the  overhead  shafting  to  the  machine, 
adequate  fencing  must  be  provided. 

The  engine  or  other  source  of  mechanical  power  in  the  bakery  will  usually 
have  a separate  room  provided  for  it,  and  so  is  itself  protected,  and  its  moving 
parts  are  adequately  shut  off  from  contact  with  any  of  the  bakehouse 
workers.  It  may  be  noticed  in  passing  that  the  Factory  Act  provides  for 
the  fencing  in  of  the  fly-wheel  of  an  engine,  “ whether  in  the  engine-room 
or  not.'’  When  a gas  engine  is  employed,  this  regulation  may  become  a 
source  of  positive  danger.  As  is  doubtless  known  to  the  great  majority  of 
readers,  small-sized  gas  engines  are  started  by  pulling  around  the  fly-wheel 
by  hand  until  the  first  working  explosion  occurs.  A wheel  with  temporary 
fencings  is  more  dangerous  than  one  unfenced  ; for,  as  a matter  of  fact,  the 
fence  is  as  often  as  not  left  out  of  position,  and  any  dependence  placed  on 
it  for  security  may  lead  to  false  confidence  and  consequent  accident.  If,  on 
the  other  hand,  the  fence  is  a fixture,  then  in  pulling  round  the  fly-wheel  there 
is  danger  of  getting  entangled  between  it  and  the  fencing.  Fortunately, 
most  of  the  inspectors  under  the  Factory  Act  approach,  with  a liberal  and 
practical  spirit,  the  laws  they  have  to  administer. 

Flour  blending  and  doughing  machines  are  frequently  so  arranged  as 
to  have  an  opening  leading  into  the  machine  from  a floor  above.  In  sueh 


590 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


cases  these  openings  will  require  to  be  fenced  or  otherwise  made  secure. 
This  can  readily  be  done  by  employing  a hopper  standing  some  eighteen 
inches  high,  and  having  at  the  bottom  a strong  grid,  composed  of  stout  iron 
bars,  about  three  inches  apart.  An  arrangement  of  this  kind  is  an  absolute 
protection,  and  has  the  advantage  that  it  need  not  be  removed  for  the  tipping 
in  of  the  contents  of  flour  sacks. 

Probably  one  of  the  most  dangerous  appliances  which  ever  enters  into 
a bakery  is  the  power-lift  for  moving  goods,  and  sometimes  persons,  from  one 
floor  to  another.  Lifts  of  this  kind,  although  mechanical  in  their  nature, 
are  integral  parts  of  the  building  and  its  permanent  fixtures,  and  so  come 
before  us  at  this  stage  for  review.  The  lift  of  a raising  capacity  of  15  to  20 
cwts.  consists  of  a cage  probably  about  6 feet  square,  and  runs  up  and  down 
a well  the  wdiole  height  of  the  building.  Where  hydrauhc  power  is  pro- 
vided, the  cage  is  frequently  supported  on  the  top  of  a long  piston  rod,  for 
which  a pit  has  to  be  sunk  under  the  lowest  part  of  the  cage  travel.  In  cases 
where  a lift  is  driven  by  an  engine,  the  driving  gear  is  most  frequently  over- 
head, but  nowadays  electricity  most  frequently  supplies  the  motive  power, 
and  the  motor  and  gearing  can  be  as  readily  arranged  afc  the  top  of  the  lift 
shaft  as  at  the  bottom  to  suit  local  conditions.  The  great  source  of  danger 
is  that  of  people  falling  down  the  well,  or  attempting  to  get  in  and  out  of  the 
cage  while  in  motion.  The  former  source  of  danger  can  be  easily  met, 
particularly  on  the  top  floor,  by  fixing  an  automatic  gate  to  the  lift, 
so  that  when  the  cage  is  not  at  the  top  floor  there  shall  be  a gate  shutting 
the  opening.  When  the  cage  comes  up  it  automatically  removes  this  gate, 
and  replaces  it  when  it  descends. 

688.  Smoke  Nuisance. — Since  smoke  nuisance  is  partly  at  least  a question 
of  construction,  this  is  a convenient  place  in  which  to  deal  with  the  law 
thereon.  Section  91  of  The  Public  Health  Act,  1875,  provides  that  ; — 

7.  Any  fireplace  or  furnace  which  does  not  as  far  as  practicable 
consume  the  smoke  arising  from  the  combustible  used  therein,  and 
which  is  used  for  working  engines  by  steam,  or  in  any  . . . bakehouse, 
or  in  any  manufacturing  or  trade  process  whatsoever  ; and  . . . 

Any  chimney  (not  being  the  chimney  of  a private  dwelling  house) 
sending  forth  black  smoke  in  such  quantity  as  to  be  a nuisance. 
Shall  be  deemed  to  be  nuisances  liable  to  be  dealt  with  summarily 
in  manner  provided  by  this  Act  ; Provided — 

Secondly.  That  where  a person  is  summoned  before  any  Court  in 
respect  of  a nuisance  arising  from  a fireplace  or  furnace  which  does  not 
consume  the  smoke  arising  from  the  combustible  used  in  such  fireplace 
or  furnace,  the  Court  shall  hold  that  no  nuisance  is  created  within  the 
meaning  of  this  Act  and  dismiss  the  complaint,  if  it  is  satisfied  that 
such  fireplace  or  furnace  is  constructed  in  such  manner  as  to  consume 
as  far  as  practicable,  having  regard  to  the  nature  of  the  manufacture 
or  trade,  all  smoke  arising  therefrom,  and  that  such  fireplace  or  furnace 
has  been  carefully  attended  to  by  the  person  having  the  charge  thereof. 

Sub-section  7,  consisting  of  two  clauses,  is  of  great  importance  to  the 
baker,  and  the  first  clause  should  be  carefully  read  in  conjunction  with  the 
second  proviso  at  the  close  of  the  section.  It  is  important  to  see  where 
these  two  taken  together  lead  us,  when  considered  apart  from  the  latter 
clause  of  Sub-section  7. 

Tliis  clause  does  not  apply  to  any  and  every  fireplace  or  furnace  but 
only  to  those  used  for  certain  specified  purposes,  among  which  are  included 
the  furnaces  of  engine  boilers,  and  those  used  in  any  bakehouse.  They 
must,  as  far  as  practicable,  consume  the  smoke  ; and  considerable  light  is 
thrown  on  tliis  condition  by  tJie  proviso.  First,  such  fireplaces  or  furnaces 


BAKEHOUSE  DESIGN. 


591 


must  be  so  constructed  as  to  consume  all  smoke  as  far  as  practicable.  It  is, 
therefore,  evident  that  if  a furnace  be  ill-constructed  so  that  it  is  impossible 
to  use  it  without  causing  smoke,  the  Act  applies.  In  this  matter  the  Courts 
will  consider  the  state  of  knowledge  in  the  particular  trade.  If  it  be  shown 
that  there  are  well-constructed,  smokeless  furnaces  of  the  same  type  in  exist- 
ence, the  Court  is  not  very  likely  to  accept  the  view  that  a furnace,  necessarily 
emitting  smoke,  is  properly  constructed.  A saving  clause  is  inserted  which 
says,  “ having  regard  to  the  nature  of  the  manufacture  or  trade."'  It  may 
very  well  be  that  in  the  case  of  steam  boilers,  wEere  firing  is  conducted  by 
continuously  adding  small  quantities  of  fuel,  little  or  no  smoke  may  be 
produced.  But  it  does  not  necessarily  follow  that  a baker  can  also  use  a 
similar  furnace  or  similar  modes  of  firing  for  his  oven.  The  continuous 
addition  of  fuel  in  small  quantities  may  not  meet  his  requirements  ; on  the 
contrary,  he  may  require  to  fire  his  oven  very  vigorousiy  between  his  batches 
of  bread.  It  is  further  submitted  that  the  fact,  even  if  proved,  that  certain 
ovens  are  smokeless  in  their  operation  should  not  be  regarded  as  showing 
that  other  ovens  have  furnaces  which  have  not  been  constructed,  so  far  as 
practicable,  to  consume  their  smoke.  Take,  for  example,  the  coke-heated 
steam  oven  ; such  ovens  may  be  fired  continuously  with  a smokeless  fuel. 
By  many  the  work  and  performance  of  this  type  of  oven  is  considered 
eminently  satisfactory  ; but  no  one  can  shut  his  eyes  to  the  fact  that  in 
London,  for  example,  such  ovens  are  by  no  means  accepted  as  universally 
suitable.  As  most  striking  proof  of  this,  various  forms  of  coke-heated  ovens 
have  been  used  by  bakers,  and  yet  subsequently  ordinary  ovens  have  been 
built  and  employed  for  special  kinds  of  work.  This  has  been,  not  because 
the  ovens  in  themselves  are  faulty,  but  because  they  have  not  been 
suited  to  the  particular  requirements  of  certain  sections  of  users.  These 
bakers  have  not  yet  been  convinced  that  in  order  to  turn  out  bread  of 
the  highest  i degree  of  excellence  they  can  yet  safely  dispense  with 
the  intermittent  fiash  heat  of  the  coal  fire  in  a side-flue  oven.  It  is 
submitted  that  this  is  a requirement  which  comes  within  the  nature  of 
their  manufacture  or  trade,  and  that  the  smoke  arising  from  a well-con- 
structed furnace  of  this  type,  properly  used,  should  not  be  regarded  as  a 
nuisance  within  the  meaning  of  this  portion  of  the  Act.  But  to  secure  the 
benefit  of  the  proviso  the  furnace  must  also  have  been  carefully  attended 
to  by  the  person  having  charge  of  it.  Finally,  it  is  necessary  that  the  Court 
must  be  satisfied  by  adequate  proof  of  the  facts  here  laid  down  as  removing 
such  smoke-emitting  furnace  from  the  category  of  nuisances  within  the 
meaning  of  the  Act. 

Let  us  see  exactly  how  far  the  clause  and  proviso  have  taken  us.  Lender 
certain  conditions  laid  down,  and  which  we  have  fully  discussed,  they  to- 
gether permit  a furnace  not  consuming  the  smoke  arising  from  the  com- 
bustible consumed  therein,  to  be  used  without  being  subject  to  the  penalties 
of  the  Act.  There  is  no  limitation  or  restriction  as  to  the  kind  or  quality  of 
the  fuel  that  may  be  burned.  Presumably,  in  the  absence  of  any  such 
restriction,  that  fuel  which  from  before  the  time  of  the  passing  of  the  Act, 
and  continuously  up  to  the  present,  has  been  most  frequently  and  commonly 
used,  namely,  ordinary  coal,  is  and  should  be  included  among  the  permitted 
combustibles.  There  is,  further,  no  stipulation  as  to  the  kind  or  quality  of 
the  smoke  that  such  furnace  may  be  allowed  to  evolve,  and  it  would  seem 
that  certainly  the  kind  of  smoke  naturally  evolved  by  coal,  as  the  most 
ordinary  and  generally  used  fuel,  would  in  any  case  be  regarded  as  fulfilling 
the  conditions  of  the  proviso.  Certainly  the  clause  and  proviso  only  deal 
with  the  furnace,  and  it  may  be  contended  that  their  stipulations  and  exemp- 
tions apply  only  to  the  smoke  of  the  furnace  itself  and  before  it  reaches  the 
chimney. 


592 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


In  the  case  of  Weekes  v.  King,  the  charge  was  that  “ from  the  chimney 
of  the  brewery  used  by  him,  not  being  the  chimney  of  a private  dwelling- 
house,  black  smoke  was  from  time  to  time  sent  forth  in  such  quantities  as 
to  be  a nuisance,  and  that  the  said  nuisance  was  caused  by  the  act  or  default 
of  the  appellant,  the  occupier  of  such  premises.”  These  charges  were  held 
to  be  proved  as  facts,  and  in  reply  “ it  was  contended  on  behalf  of  the  appel- 
lant, that  he  was  protected  by  the  second  proviso  at  the  end  of  the  91st 
Section  of  the  Public  Health  Act,  and  the  appellant’s  stoker  proved  that, 
in  his  opinion,  the  appellant  used  the  best  coal  for  furnaces,  but  that  when 
he  made  up  the  fire  black  smoke  was  necessarily  sent  forth  for  five  or  ten 
minutes.  Evidence  was  also  tendered  on  behalf  of  the  appellant  to  prove 
the  construction  of  the  furnace.”  The  justices,  however,  being  “ of  opinion 
that  such  second  proviso  applies  only  to  the  first  nuisance  defined  by  the 
said  7th  Sub-section  of  the  91st  Section,  while  the  summons  was  in  respect  of 
the  nuisance  defined  by  the  second  paragraph  of  such  sub-section,  refused 
to  receive  evidence  as  to  the  construction  of  the  furnace  ” and  gave  their 
decision  against  the  appellant.  The  questions  of  law  submitted  were  : (1) 
Whether  the  said  second  proviso  at  the  end  of  Section  91  of  the  Public 
Health  Act,  1875,  applies  to  the  offence  charged  against  the  appellant  ? 
(2)  Whether  they  (the  justices)  should  have  received  evidence  to  show  the 
construction  of  the  fireplace  or  furnace. 

On  behalf  of  the  appellant,  Poland  contended  that  the  second  proviso 
applies  to  the  whole  of  the  7th  Sub-section,  and  that  the  justices  ought  to 
have  heard  the  appellant’s  evidence  as  to  the  construction  of  the  furnace. 
If  the  justices  are  right,  then  any  chimney  of  a manufactory  sending  forth 
black  smoke  comes  within  the  section,  and  it  is  no  defence  that  it  is  being 
used  in  carrying  on  a trade  or  manufacture.  The  anomaly  would  therefore 
arise  that,  if  a furnace  is  constructed  to  consume  as  far  as  possible,  having 
regard  to  the  nature  of  the  manufacture,  the  smoke  arising  therefrom,  it 
may  issue  forth  any  amount  of  sulphurous  smoke  so  long  as  it  is  not  black,, 
but  however  scientifically  it  is  constructed  it  must  not  be  allowed  to  send 
forth  even  the  small  quantity  of  the  less  injurious  black  smoke  necessary 
to  start  the  fires. 

Pollock,  B.,  in  giving  judgment  said,  “ I am  of  opinion  this  appeal  must 
be  dismissed.  . . . By  the  7th  Sub -section  (being  that  referred  to)  twO’ 
distinct  offences  are,  in  my  opinion,  contemplated  and  legislated  upon.  . . . 
I find  that  it  is  provided  that  any  chimney  (not  being  the  chimney  of  a private 
dwelling-house)  sending  forth  black  smoke  in  such  quantity  as  to  be  a nuis- 
ance is  to  be  the  subject  of  a penalty.  That,  to  my  mind,  is  a clear  and 
distinct  offence.  Then  the  other  offence  is  the  having  any  fireplace  or  fur- 
nace which  does  not  as  far  as  practicable,  consume  the  smoke  arising  from 
the  combustible  used  therein,  and  which  is  used  for  working  engines  by 
steam,  or  in  any  . . . bakehouse  ...  or  in  any  manufacturing  or  trade 
process  whatsoever.  The  smoke  mentioned  in  this  paragraph  may  be  more 
or  less  injurious  than  the  black  smoke  mentioned  in  the  following  paragraph,, 
but  however  that  may  be,  the  Legislation  provides  with  respect  to  it  that 
it  is  to  be  reduced  to  a minimum.  Wlien  the  sub-section  is  read  in  thia 
manner,  it  is  clear  that  the  second  proviso  at  the  end  of  the  section  refers 
to  the  first  paragraph  of  the  sub-section,  and  not  to  the  second.  The  appel- 
lant, therefore,  cannot,  I think,  avail  himself  of  this  proviso  to  protect  him- 
self against  the  charge  which  is  brought  against  him,  and  the  justices  were,, 
in  my  opinion,  quite  right  in  refusing  to  receive  evidence  of  the  construction 
of  the  furnace.” 

The  appeal  was  accordingly  dismissed,  and  the  decision  of  the  justices 
affirmed. 

The  judge’s  decision  in  this  case  has  far  reaching  effects.  It  in  practice 


BAKEHOUSE  DESIGN. 


593 


limits  the  kind  of  smoke  that  the  furnace  may  produce  to  only  such  kinds 
as  are  not  black,  a restriction  which  altogether  forbids  the  use  of  ordinary 
coal  as  a fuel  and  restricts  the  user  of  such  furnace  to  the  employment  of 
abnormal  combustibles  only.  And  provided  that  such  fuel  gives  a grey  instead 
of  a black  smoke,  there  is  the  further  anomaly  that  it  may  with  impunity 
be  far  more  injurious  in  character.  In  fact,  such  smoke  may  consist  largely 
of  sulphurous  gases  or  even  arsenical  fumes,  both  of  which  are  almost  in- 
visible, and  yet  under  this  Act  at  least  they  may  escape  being  a nuisance. 

Scotch  Law  of  Furnace  Smoke. — The  Public  Health  (Scotland)  Act, 
1867,  contains  the  same  clause  as  Sub -section  7 of  the  English  Act,  and 
the  Scotch  Courts  in  the  case  of  Dumfries  Local  Authority  v.  Murphy,  held 
that  a furnace  must  be  shown  not  to  consume  its  owtl  smoke  by  reason  of 
faulty  construction  or  else  of  systematic  misuse,  and  the  fact  that  a well- 
constructed  furnace  had  on  ten  occasions  in  a period  of  four  months  sent 
out  quantities  of  black  smoke  was  held  not  to  be  evidence  of  such  systematic 
misuse  as  to  bring  it  within  the  terms  of  the  section.  This  decision  is  at 
variance  with  that  of  the  English  Courts.  Evidence  was  clearly  permitted 
to  be  given  as  to  the  construction  of  the  furnace  ; and  the  furnace  being 
well  constructed,  having  regard  to  the  nature  of  the  manufacture  or  trade, 
and  also  properly  used,  the  fact  of  comparatively  frequent  emissions  of 
offensive  black  smoke  was  held  not  to  bring  it  within  the  definition  of  a 
nuisance  as  given  in  the  section  of  the  Act. 

Smoke  Consumption,  Public  Health  (Londoyi)  Act,  1891. — ^London  has 
its  own  Public  Health  Act,  and  this  Act  deals  specially  with  smoke  con- 
sumption. It  provides  that — 

S.  23. — (1)  Every  furnace  employed  in  any  . . . bakehouse  . . . 
shall  be  constructed  so  as  to  consume  or  burn  the  smoke  arising  from 
such  furnace. 

(3)  Every  . . . furnace  used  in  the  worldng  of  any  steam  vessel 
on  the  river  Thames  . . . shall  be  constructed  so  as  to  consume  or 
burn  the  smoke  arising  from  such  . . . furnace. 

(4)  Provided  that  in  this  section  the  words  “ consume  or  burn  the 
smoke  ""  shall  not  be  held  in  all  cases  to  mean  “ consume  or  burn 
all  the  smoke,""  and  the  Court  hearing  an  information  against  a 
person  may  remit  the  fine  if  of  opinion  that  such  person  has  so  con- 
structed his  furnace  as  to  consume  or  burn,  as  far  as  possible,  all  the 
smoke  arising  from  such  furnace,  and  has  carefully  attended  to  the 
same,  and  consumed  or  burned,  as  far  as  possible,  the  smoke  arising 
from  such  furnace. 

In  addition  Section  24  of  the  Act  is  the  same  as  Sub-section  7 and  the 
proviso  of  the  General  Public  Health  Act  now  under  discussion.  It  will 
be  seen  that  these  provisions  extend  much  the  same  kind  of  protection  to 
the  users  of  furnaces  for  trade  purposes  as  does  the  general  Act.  Atten- 
tion is  called  to  the  similar  provision  for  steamboats  as  land  furnaces. 
Notice  first  that  the  wording  of  Sub -sections  1 and  3 is  the  same.  Then 
steam-boat  furnaces  burn  ordinary  coal,  and  their  smoke  must  be  of  the 
usual  type  and  not  an  abnormal  grey  or  practically  invisible  smoke.  Never- 
theless, these  furnaces  are,  subject  to  conditions,  exempted  from  the  penalties 
of  the  Act. 

Effect  of  Coyiflicting  Decisions. — In  view  of  these  conflicting  decisions  it 
is  with  great  deference  submitted  that  the  clause  “ any  chimney  (not  being 
the  chimney  of  a private  dwelling  house)  sending  forth  black  smoke  in 
such  quantity  as  to  be  a nuisance  ""  should  be  interpreted  as  though  it  went 
on  to  except  such  smoke  as  may  be  emitted  by  a furnace  or  fireplace  used 
in  accordance  with  the  first  clause  of  the  sub -section  read  in  conjunction 
v'ith  the  second  proviso.  From  this  it  would  follow  that  the  judgment 

Q Q 


594 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


in  the  case  of  Weehes  v.  King  erroneous,  and  that  the  argument  of 
Koland,  counsel  for  the  appellant,  was  substantially  correct.  This  is  a 
view  wliich  has  been  held  by  eminent  counsel,  and  in  Ex  parte  Schofield, 
1891,  an  attempt  was  made  to  review  the  judgment  in  the  Court  of  Appeal. 
That  Court,  however,  held  that  it  was  bound  by  Weekes  v.  King,  as  being 
in  the  nature  of  criminal  proceedings,  and  therefore  that  it  could  not  hear 
any  appeal  from  the  decision  of  the  Queen’s  Bench. 

Present  Interpretation  of  Law. — The  present  state  of  the  law,  in  the  light 
of  Weekes  v.  King,  may  be  summarised  thus  : — If  proceedings  are  taken 
under  the  first  part  of  Sub-section  7,  Section  91,  of  the  Public  Health  Act, 
the  proviso  of  the  section  applies,  and  if  the  Court  is  satisfied  as  to  the 
construction  and  proper  use  of  the  furnace  it  must  hold  that  there  has  been 
no  nuisance  within  the  meaning  of  the  Act.  But  if  the  proceedings  are 
taken  under  the  second  part  for  sending  forth  black  smoke,  then  the  proviso 
does  not  apply,  and  no  evidence  can  be  given  as  to  the  construction  of 
the  furnace,  or  its  careful  use  in  regard  to  the  nature  of  the  manufacture 
or  trade.  These  are,  in  fact,  no  defence,  and  the  emission  of  black  smoke 
from  whatever  cause  arising,  and  however  it  may  be  justified  by  the  exi- 
gencies of  manufacture,  is  an  offence  under  this  clause  of  the  sub -section. 
Obviously,  if  the  smoke  is  not  black,  however  injurious  it  may  be,  proceed- 
ings will  not  succeed  under  this  latter  clause.  Black  smoke  in  such  quan- 
tities as  to  be  a nuisance  is  not  permitted  at  all,  other  smoke  must  be  reduced 
to  a minimum,  having  regard  to  the  conditions  of  manufacture. 

The  question  as  to  whether  the  quantity  of  black  smoke  is  sufficient 
to  be  a nuisance  is  one  of  fact,  and  as  such  is  decided  by  the  justices.  In 
practice,  the  chimneys  are  kept  under  observation  by  an  Inspector  of 
Nuisances,  and  if  black  smoke  is  emitted  for  too  long  a period  of  time, 
very  commonly  ten  minutes,  such  is  regarded  as  being  a nuisance.  Probably 
in  manufacturing  districts  the  quantity  of  black  smoke  necessary  to  so 
constitute  a nuisance  would  be  interpreted  more  liberally  than  in  a high- 
class  residential  neighbourhood. 

' 689.  Working  Requirements — Compactness. — In  natural  sequence  there 

next  come  forward  for  consideration  the  requirements  of  the  baker  in  using 
the  building,  as  these  must  vitally  affect  the  design.  Among  such  one 
of  the  first  to  occur  is  that  of  compactness  : bakeries  are  not  wanted  to 
be  long  and  straggling,  or  with  the  work  going  on  simultaneously  in  more 
than  one  place.  There  is  otherwiseThe  inevitable  loss  of  time  resulting  from 
inadequate  supervision,  and  also  that  necessarily  following  from  ovens, 
machinery,  tables,  etc.,  being  too  far  away  from  each  other,  and  what  is 
more  important  the  difficulty  of  ensuring  the  correct  temperature  and 
atmosphere.  In  the  next  place,  matters  must  be  so  arranged  that  all 
approaches  and  exits  are  under  control,  so  that  the  delivery  of  flour  and 
raw  material,  and  also  the  packing  up  and  dispatch  of  bread  and  finished 
goods,  may  be  easily  and  efficiently  checked.  Wliere  at  all  practicable, 
all  means  of  egress  and  ingress  should  be  through  the  one  main  entrance, 
or,  if  through  different  entrances,  the  whole  of  these  should  be  under  control 
from  the  office.  In  the  case  of  a retail  trade,  there  must  be  ready  means 
of  delivering  goods  from  the  bakehouse  to  the  shop.  This  necessitates,  in 
the  case  of  bakery  and  shop  being  on  the  same  level,  a direct  passage  from 
one  to  the  other.  With  a bakery  either  under  or  over  the  shop  level,  the 
best  plan  is  a simply  constructed  lift. 

690.  Ventilation. — As  already  explained,  efficient  ventilation  is  com- 
pulsory under  the  Factory  Act,  but  apart  from  that  the  necessities  of  the 
case  would  lead  every  baker  to  ensure  his  ventilation  being  as  perfect  as 
possible.  With  all  hot  work  the  comfort  and  health  of  the  operatives 


BAKEHOUSE  DESIGN. 


595 


require  abundance  of  fresh  and  pure  air.  The  ventilation  of  a bakery  is 
fraught  with  some  difficulty,  as  it  is  extremely  important  that  there  be  no 
draughts  nor  sudden  chills  through  the  admission  of  large  quantities  of 
cold  air  in  a short  space  of  time.  Ventilation  is  usually  effected  by  what 
are  Imown  as  convection  currents,  the  scientific  explanation  of  which  has 
been  given  in  the  introductory  chapter.  Briefly,  air  expands  as  it  gets 
hot,  and  consequently  is  lighter,  bulk  for  bulk,  than  when  cold.  As  a 
result  hot  (light)  air  is  displaced  by  cold  (heavy)  air,  and  it  may  be  said 
that  hot  air  floats  upwards,  and  cold  descends  to  take  its  place.  From 
this  it  follows  that  in  rooms  where  gas  is  burning  or  wdiere  there  is  any 
source  of  heat,  the  upper  part  of  the  room  is  distinctly  the  hotter.  If 
air-flues  are  led  upwards  from  the  upper  portion  of  a room  used  as  a bakery, 
the  hot  air  will  escape  from  these,  while  cold  air  will  stream  in  to  take  its 
place  at  the  lower  levels  if  suitable  openings  are  provided.  This  effect 
is  easily  studied  in  the  accompanying  figure.  No.  44.  Immediately  over 


Fig.  44. — Diagram  Showing  Ventilating  Air-Currents. 


the  ovens  is  an  uptake  to  which  a sliding  door  is  attached  ; j^^this  is  exceed- 
ingly simple,  and  is  readily  worked  by  a cord  from  the  floor  level.  At  the 
sides  in'  various  places  are  inlet  pipes  ; the  tops  of  these  are  so  placed  that 
the  cold  air  cannot  strike  directly  on  troughs  or  other  vessels  containing 
ferments,  sponges  or  doughs. 

A useful  form  of  ventilating  flue  is  constructed  from 
a compound  chimney  pipe  such  as  shown  in  sketch. 

Fig.  45.  This  pipe  is  made  of  earthenware,  in  lengths 
of  from  12  in.  to  18  in.,  with  spigot  and  faucet  joints 
like  those  of  an  ordinary  drain  pipe.  But  on  one  side 
of  the  flue  pipe  is  formed  a chamber  ; this  separate 
chamber  or  flue  is  the  air  flue.  The  heat  of  the  chim- 
ley  portion  warms  the  air  flue,  and  so  creates  a powerful 
fraught  through  it.  Oven  chimneys  may,  as  shown, 
oe  constructed  of  such  piping  ; so  also  in  under- 
ground bakehouses  may  the  flues  for  fires  in  rooms 
ibove,  the  air  flue  being  carried  down  into  the  bak- 
! ^ry.  Windows  may  be  used  for  ventilating  purposes, 

)ut  it  is  then  a good  plan  to  place  a board  on  the 
ower  side,  so  as  to  cut  off  any  direct  indraught. 

691.  Constancy  of  Temperature. — Sudden  changes 
n ^temperature  are  of  course  largely  produced  by 

Iraughts,  but  also  may  be  due  to  the  construction  and  45 Ventilating 

naterials  used  in  the  actual  building  of  the  bakehouse.  Chimney  Pipe. 


596  THE  TECHNOLOGY  OF  BREAD-MAKING. 

Lath  and  plaster  are  not  the  most  suitable  methods  of  building  bakehouse  walls. 
These  should  be  constructed  either  of  stone  or  brick  of  sufficient  thickness, 
and  if  the  latter  be  used  a fairly  solid  brick  is  an  advantage.  Brickwork 
should  be  cemented  on  the  surface,  or  other  steps  taken  to  ensure  its  being 
water-tight.  The  same  reasons  which  militate  against  thin  walls  also 
apply  to  iron.  For  light  sheds  corrugated  iron  may  do  very  well,  but  it 
is  not  the  material  for  bakery  construction.  Its  ready  conductivity  of 
heat  causes  the  bakery  to  be  extremely  cold  in  winter  and  hot  in  summer. 
For  the  same  reasons  open  iron  roofs  are  to  be  condemned.  To  prevent 
fluctuations  in  temperature  there  is  nothing  so  effective  as  having  another 
room  over  your  bakery,  and  the  common  practice  of  having  the  flour  store 
above  is  more  than  justified  by  its  influence  in  maintaining  an  equal  tempera- 
ture in  the  bakery  itself.  Suitable  roofing  is  also  important  and  should 
receive  careful  consideration.  Slated  roofs  are  not  necessarily  the  ^^^st, 
but  the  builder,  architect  or  engineer  should  be  able  to  advise  as  to  the 
best  roofing  to  suit  any  given  locality,  if  his  attention  be  drawn  to  the 
need  for  roofing  such  as  will  be  warm  in  winter  and  cool  in  summer.  Special 
attention  may  be  here  called  to  suitable  specialised  roofing  felts,  which  are 
not  only  excellent  but  durable  and  cheap.  (See  also  paragraph  737.) 

692.  Arrangements  for  Ovens. — It  may  be  taken  as  a cardinal  principle 
of  the  authors  that  ovens  should  be  fired  from  outside  the  portions  of 
the  building  in  which  baking  operations  are  carried  on.  In  conjunction 
with  this,  one  has  of  course  to  bear  in  mind  the  fact  that  internal  firing, 
or  firing  in  some  other  way  from  the  front,  is  much  preferred  by  some 
bakers  ; but  such  reasons  as  once  existed  for  such  preferences  can  hardly 
be  said  to  apply  to-day.  Oven  constructions  are  now  available  which 
enable  any  class  of  work  to  be  perfectly  carried  on,  and  are  yet  arranged 
to  be  fired  from  outside  the  bakery  proper.  Supposed  inapphcabihty  of 
modern  externally  fired  ovens  for  certain  classes  of  work  is  more  imaginary 
than  real,  and  there  are  now  ovens  available  which,  fired  from  outside  the 
bakery,  do  as  good  quality  work  as  others  with  the  fire  manipulated  within 
the  bakehouse  proper.  This  view  leads  the  authors  to  suggest  the  provision 
in  bakeries  of  a separate  stokehole,  with  means  of  access  from  the  bakery, 
and  separate  entrances  for  the  bringing  in  of  fuel  and  the  carting  away  of 
ashes.  Ovens  may  be  built  within  the  bakery  itself,  but  where  practicable 
the  authors  prefer  to  have  them  outside,  with  lean-to  or  other  roof  covering 
over  the  ovens  themselves  only.  This  separate  building  can  then  receive 
independent  ventilation,  so  as  to  avoid  undue  heating  by  the  oven  of  the 
bakery  itself.  Where  there  is  a row  of  ovens,  their  faces  and  doors  should 
be  flush  with,  or  form  part  of,  one  wall,  and  this  wall  should  be  carried  o 
course  right  up  to  the  ceiling.  This  should  be  done  even  if  the  ovens  are 
within  the  main  building,  and  have  the  upper  rooms  extending  over  theni. 
Such  a wall  may  also  assist  to  bear  the  superincumbent  weight,  if  desired 
to  do  so,  but  it  is  well  so  to  arrange  matters  that  independent  pillars  or 
columns  are  provided  between  each  oven  to  carry  the  weight  above.  Ino 
general  work  may  be  faced  up  uniform  with  these,  or  the  ovens  may  be 
slightly  recessed,  so  as  to  give  a somewhat  improved  architectural  effect, 
l)ut  in  either  case  ovens  and  buildings  should  be  separate  and  distinct  from 
each  other. 

The  design  of  the  bakehouse  must  depend  somewhat  on  the  nature  ot 
ovens  selected.  These  resolve  themselves,  so  far  as  British  practice  is 
concerned,  into  several  types,  of  which  the  ordinary  oven  loaded  with  a 
iieel  (usually  a rectangular  chamber)  and  the  drawplate  oven,  which  is 
narrow  and  elongated,  are  the  most  frequent.  The  particular  shape  ot 
this  latter  variety  is  determined  by  the  width  of  plate  over  which  men 


BAKEHOUSE  DESIGN. 


597 


can  set  bread  by  hand,  except  for  close-set  bread  and  other  varieties  which 
lend  themselves  to  the  use  of  setters.  This  consideration  practically  limits 
the  w'idth  of  drawplates  to  six  feet,  which  space  can  be  readily  spanned 
by  reaching  from  either  side. 

693.  Machinery. — The  arrangements  in  this  matter  must  depend  largely 
on  the  space  at  command  and  its  shape  and  other  characteristics.  The 
engine  should  have  a separate  room  provided  for  it.  This  is  not  often  a 
matter  of  great  difficulty,  because  in  even  a small  bakehouse  the  engine 
may  be  screened  off  with  a glass  and  woodwork  partition. 

Naturally,  in  arranging  machinery  and  the  bakery  generally,  provision 
will  be  made  for  running  materials  about  as  little  as  possible.  In  Great 
Britain,  flour  store-rooms  are  generally  at  the  top  of  the  bakery,  and  the 
flour  is  at  once  raised  there  when  brought  into  the  building  owing  to  the 
convenience  of  utilising  the  laws  of  gravity  for  the  conveyance  of  the  flour 
and  dough  to  the  lower  floors.  In  countries  with  more  severe  climates, 
however,  where  extreme  cold  and  heat  is  experienced,  the  flour  is  often 
stored  in  underground  cellars  to  enable  it  to  be  kept  at  a uniform  tempera- 
ture. Elevators  are  then  employed  for  conveying  it  to  the  top  floor  for 
distribution  as  before  referred  to. 

694.  Typical  Bakery  Designs. — Having  dealt  with  general  principles, 
an  effort  will  next  be  made  to  show  how  these  principles  may  be  embodied 
in  everyday  work.  For  that  purpose  the  following  descriptions,  illustrated 
by  plates  VII  to  X are  given.  It  must  be  remembered  that  these  are 
not  to  be  taken  as  complete  working  drawings  ; many  little  details  of 
construction  are  omitted,  because  they  do  not  affect  the  general  principles 
of  the  design. 

695.  Single  Peel  Oven  Bakehouse. — On  Plate  VII  there  is  shown  a 
small  bakehouse  fitted  with  one  peel  oven,  which  may  be  of  the  one-deck 
or  two-deck  type.  The  outside  width  is  18  ft.  6 in.,  windows  all  in 
front,  and  depth  30  ft.  The  choice  as  to  which  of  the  two  types  of  ovens 
mentioned  shall  be  decided  upon,  will  be  governed  by  consideration  of 
size  and  nature  of  trade  as  well  as  cost  ; for  guidance  in  this  respect  refer 
to  paragraphs  749  et  seq.  dealing  with  ovens.  The  firing  arrangement  is 
at  the  side,  giving  a separate  stokehole,  fitted  with  coke  bunker.  The 
assumption  is  that  the  oven  is  not  accessible  at  the  back  ; in  fact,  that  no 
facilities  for  either  light  or  entrance  are  obtainable  from  anywhere  but 
the  front.  Beyond  showing  a kneading  trough  and  tempering  tank 
I (see  paragraph  730)  at  one  side,  no  attempt  has  been  made  to  introduce 
fixtures  and  utensils  ; the  places  for  the  latter  will  suggest  themselves  to 
.the  baker  in  looking  over  the  plan.  The  staircase  leading  to  the  flour  store 
above  is  arranged  so  as  not  to  interfere  with  the  lighting  of  the  bakehouse, 
^and  to  enable  the  Imeading  trough  to  occupy  a position  in  which  it  is  not 
exposed  to  the  draught  from  the  entrance  doorway.  In  the  flour  loft  is 
[.shown  in  outline  the  position  of  a sifting  machine  (see  paragraph  729), 
through  which  flour  is  intended  to  be  delivered  into  the  trough  below.  This 
j machine  is  readily  worked  by  hand,  and  should  be  considered  indispensable 
I'as  all  flour  bags  contain  foreign  matter  such  as  oddments  of  string,  fluff, 

etc.,  which  may  easily  escape  the  dough  maker.  The  oven  portion  of  the 
building  is  covered  by  a lean-to  roof,  one  storey  high,  and  raised  and 
louvred  portions  should  be  fitted  at  the  upper  part  of  the  roof  to  provide 
ventilation.  The  top  of  the  oven  is  separated  from  the  bakehouse  by  a 
j^brick  wall,  but  is  open  to  the  stokehole,  which  is  therefore  also  efficiently 
.ventilated.  A large  amount  of  work  could  be  easily  done  in  a bakehouse 
I of  this  type. 


Plans  of  Bakehouses, 


Plate  VII. 


With  One  Peel  Oven. 


With  Two  Peel  Ovens. 


REFERENCES. 

A.  Open  Yard. 

B.  Flour  Store. 

c.  Sifter  and  Shoot. 

D.  Bakehouse. 

E.  Dougli  Trough. 

F.  Moulding  Table. 

G.  Tempering  Tank. 

H.  Stoke-hole. 

j.  Confectionery  and  Stores. 

K.  Office. 

L.  Furnaces. 


593 


BAKEHOUSE  DESIGN. 


599 


Assuming  a two-deck  oven,  the  lower  chamber  should  preferably  be 
reserved  for  bread  and  the  upper  for  confectionery,  and  with  a modern 
steampipe  oven  in  which  each  chamber  is  fired  independently  of  the  other 
and  capable  of  yielding  a batch  of  2 lb.  crusty  loaves  per  IJ  hours,  a trade 
of  30  to  35  sacks  (280  lbs.)  per  week  is  possible.  In  addition  to  this  a con- 
siderable output  of  confectionery  and  cake  will  be  obtained  by  using  the 
oven  during  the  hours  in  which  the  bread  baking  is  stopped.  The  introduc- 
tion of  proper  drainage  and  sanitary  apphances  would  render  this  bakehouse, 
small  as  it  is,  perfect,  from  a hygienic  point  of  view — so  perfect,  at  least, 
as  hand-making  appliances  wiU  permit. 

696.  Bakehouse  for  Two  Peel  Ovens. — The  next  plan  on  the  same  Plate, 
VH,  is  one  of  a larger  bakehouse,  in  which  both  front  and  side  light 
is  obtainable,  although  it  will  be  seen  the  latter  can  be  easily  dispensed 
with.  This  bakery  is  shown  fitted  with  two  peel  ovens,  which  again  would 
preferably  be  two -deck.  One  of  the  upper  ovens  may  be  arranged  as  a 
steam-retaining  sloped  sole  oven  for  glazed  or  Vienna  bread.  The  sugges- 
tion here  is  that  the  ovens  shall  be  fired  at  the  back,  and  accordingly  a 
stokehole  extends  the  whole  length  of  the  back  ; opening  from  the  passage  to 
the  stokehole  is  a door  leading  to  a small  yard,  in  which  are  built  a lavatory 
and  men’s  offices.  In  order  to  protect  workmen  this  passage  is  roofed  over, 
but  left  open  on  side  nearest  the  yard.  The  bakery  has  a table  in  the 
centre,  while  sufficient  kneading  troughs  would  find  room  against  the 
walls.  A sifting  machine  and  tempering  tank,  as  before  described,  are 
shown  in  a position  to  which  the  troughs  may  be  in  turn  conveniently 
moved.  All  kneading  troughs  should  be  on  castors  to  enable  them  to  be 
readily  moved  to  suit  the  work  as  also  to  enable  thorough  cleaning  of  floors, 
walls  and  corners.  To  the  right  hand  of  the  bakery  is  a small  office,  and 
behind  is  a pastry-room.  Over  the  bakery  is  the  flour  store,  arranged  as 
in  the  previous  sketch.  A bakehouse  such  as  this  would  have  capacity 
for  a large  trade,  and  with  properly  selected  ovens  there  would  be  no  diffi- 
culty in  turning  out  a hundred  sacks  per  week,  and  also  the  corresponding 
amount  of  small  goods,  confectionery,  and  cake.  Of  course,  the  amount 
of  bakehouse  space  might  in  such  a case  be  increased  with  advantage,  or 
the  space  might  be  altered  in  shape  to  meet  exigencies  of  site,  the  sketch 
is  merely  intended  to  indicate  the  minimum  space  required  for  the  amount 
of  work  wanted.  No  provision  has  been  made  here  for  machinery,  but 
such  could  easily  be  adopted  if  desired.  Bread-rooms  and  other  conveniences 
should  be  attached  to  the  bakery  front,  or  side  opposite  ovens. 

697.  Single  Drawplate  Oven  Bakery. — Plate  VIII  shows  plans  of  a 
bakehouse  fitted  with  a split-type  drawplate  oven.  Fig.  81,  over  which 
may  also  with  advantage  be  built  a peel  oven,  see  Fig.  82,  in  the  case  of 
mixed  trades.  This  arrangement  lends  itself  well  to  a site  where  there  is  a> 
very  narrow  frontage  and  plenty  of  depth.  The  sketch  has  been  prepared  on 
this  assumption,  and  shows  a bakery  standing  on  a piece  of  ground  15  ft. 
4 in.  in  width.  This  might  be  still  further  diminished  by  lessening  the 
width  of  the  passage  round  the  stokehole,  which  in  the  plan  is  3 ft.  wide. 
By  resorting  to  the  plan  of  having  the  oven  fired  at  front  and  within  the 
bakehouse.  Fig.  4,  Plate  VIII,  the  total  width  might  still  further  be  reduced 
to  10  ft.  inside  and  12  ft.  4 in.  external  width.  Or  even  in  this  case  the 
oven  might  be  fired  at  the  back  by  arranging  a spiral  staircase  or  step- 
ladder  down  into  the  stokehole  from  over  the  oven  through  the  flour  store 
above.  Such  very  narrow  sites  are  not,  however,  likely  to  often  occur, 
and  the  staircase  arrangement  is  not  recommended.  As  drawn,  it  is  assumed 
that  no  light  is  available  from  the  sides,  and  accordingly  small  windows 


Plate  VIII. 

Plans  of  Single  Drawplate  Oven  Bakery. 


10  a p 


REFERENCES. 

A.  Gas  Engine. 

B.  Dongh  Divider, 
c.  Moulding  Table. 

'E.  “ Single  Blade  ” Kneading  Machine. 

F.  Drawplate  Oven. 

D.  Stoke-hole. 

G.  Flour  Store. 

H.  Blending  Hopper,  Sifter  and  Shoot, 
j.  Drawplate. 

K.  Space  for  Dough  Trucks  and  Proving 

Dough. 

L.  Front-fired  Drawplate  Oven. 

600 


BAKEHOUSE  DESIGN. 


601 


are  placed  over  the  ovens  into  the  bakehouse.  This  plan  shows  the  position 
of  flour-blending,  sifting,  doughing,  and  dividing  machinery,  arranged  in 
the  bakehouse,  and  also  parts  of  the  same  overhead.  The  engine-room 
is  in  front  of  the  bakery,  and  beyond  that  is  the  bread-room.  A bakery 
such  as  this  forms  an  interesting  and  fairly  complete  installation.  With 
this  plant,  especially  where  the  drawplate  has  over  it  a peel  oven,  or  is  of 
the  two-deck  variety,  an  extensive  and  varied  trade  may  be  done,  and  in- 
stances are  known  in  which  over  a hundred  sacks  per  week  have  been  regularly 
turned  out  with  similar  equipment.  The  machine  plant  indicated  could  very 
well  turn  out  sufficient  work  to  warrant  the  erection  of  another  oven  beside 
that  shown,  maldng  of  course  the  bakehouse  correspondingly  wider.  With 


Fig.  46.  Oven  for  Small  Bakery. 


Fig.  47.  Interior  of  Small  Machine  Bakery. 


602 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


increased  width  rearrangement  of  space  would  permit  the  depth  to  be 
reduced.  Fig.  46  shows  an  oven  such  as  this  bakery  might  have  and 
Fig.  47  a view  of  a bakery  fitted  with  two-deck  draw-plate  ovens  and 
machinery  on  a small  scale. 

698.  Shop  and  Overhead  Bakery. — ^The  designs  given  on  Plate  IX  take 
into  consideration  a business  which  is  supposed  to  be  in  the  main  street 
of  a good  neighbourhood  where  the  exigencies  of  the  circumstances  demand 
both  bakehouse  and  shop  to  be  in  close  proximity.  It  is  assumed  thrd 
the  only  access  to  the  premises  is  from  the  front  or  street  side,  there  only 
being  at  the  back  a limited  amount  of  air  and  lighting  space,  which  cannot 
be  utilised  in  any  way  in  connection  with  the  manufacturing  operations 
of  the  business. 

Regarding  the  shop  itself,  much  must  of  necessity  be  left  to  the  nature 
of  the  business  and  the  individual  taste  of  the  proprietor.  It  goes  without 
saying  that  window  space  is  required  for  the  display  of  goods  ; this  is  pro- 
vided by  two  windows,  each  about  10  ft.  in  length.  On  the  one  side  of 
the  shop  is  a counter,  and  the  other  is  fitted  with  a table,  which  may  also 
be  used  for  counter  purposes.  Toward  the  back  of  the  shop  some  small 
tables  are  placed,  for  the  purpose  of  serving  light  refreshment — tea  and  coffee. 
Descending  from  the  back  of  the  shop  is  a staircase  leading  to  lavatories  and 
retiring  rooms  in  the  basement.  These  are  indicated  by  dotted  lines  on 
the  ground-floor  plan.  A passage  from  the  bottom  of  the  staircase  leads 
to  one  set  of  lavatories  and  w.c.'s  on  the  left  hand.  Another  similar  set 
is  reached  through  the  room  shown  under  part  of  the  bread-room.  This 
basement  room,  with  the  adjoining  conveniences,  could  be  retained  for 
the  staff,  the  others  being  reserved  for  the  accommodation  of  customers, 
and  both  kept  separate  and  distinct  from  each  other.  This  basement 
might  also  be  used  for  the  preparation  of  light  refreshment  to  be  sent  up  by 
a small  lift  fixed  by  the  top  of  the  stairs. 

It  being  assumed  that  the  only  approach  to  the  building  is  from  the 
front,  means  of  ingress  and  egress  to  the  bakery  have  been  provided  by  a 
side  passage  on  the  right  hand  of  the  shop  ; this  goes  right  through  to 
the  back  of  the  building,  and  has  doors  leading  into  the  bread- delivery 
room  and  the  office. 

As  it  is  no  longer  possible  to  have  a new  underground  bakehouse,  the 
bakery  is  shown  overhead,  similarly  to  the  not  unusual  plan  of  having  hotel 
kitchens,  etc.,  at  the  top  of  the  building.  Let  us  now  rapidly  run  through 
the  general  arrangements  of  the  bakery.  As  aheady  explained,  the  shop 
is  on  the  ground  floor,  with  lavatories  in  back  part  of  basement,  opening 
out  in  area  behind.  At  the  rear  of  the  shop  is  the  bread  cooling  and  delivery 
room.  On  the  first  floor  is  the  bakery,  containing  the  ovens,  loaf  dough 
divider,  and  moulding  tables.  Other  machinery  and  the  engine  are  arranged 
on  the  second  floor,  while  the  flour  stores  are  on  the  third  floor.  A more 
detailed  examination  of  the  arrangements  may  be  made  by  following  the 
flour  from  its  entry  into  the  place  to  its  departure  as  bread.  Being  situated 
on  a main  and  busy  thoroughfare,  all  flour  will  have  to  be  delivered  either 
early  in  the  morning  or  preferably  late  in  the  evening  when  the  shop  business 
is  over.  The  flour  van  would  be  backed  against  the  side  entrance  and 
the  flour  drawn  up  at  once  to  the  third  floor  by  the  sack  hoist  some  three 
or  four  feet  in  from  the  door.  The  hoist  itself  is  fixed  overhead  in  the 
flour-room,  and  draws  the  sack  up  through  trap  doors  on  each  landing  ; 
in  this  way  flour  or  other  material  may  readily  be  brought  from  a van  at 
the  side  entrance  to  any  desired  floor.  Where  considered  necessary  flour- 
blending machinery  will  be  fixed  underneath  the  third  floor,  and  arranged 
so  as  to  be  worked  from  the  flour  store  (paragraphs  726  to  728) . The  hopper. 


BAKEHOUSE  DESIGN. 


603 


through  which  the  flour  passes  to  the  sifter,  is  also  on  this  floor,  the  sifter 
itself  being  bolted  up  underneath  the  joists,  as  shown  on  the  sectional 
dra\Yings.  From  the  sifter  the  flour  passes  into  the  doughing  machine. 
The  sifted  flour,  together  with  water  from  the  tempering  tank  and  yeast 
or  ferment,  as  the  case  may  be,  is  converted  by  means  of  the  kneading 
machine  into  dough.  For  ferments  and  sponges  a room  has  been  provided 
in  one  corner  of  the  machinery  room,  where  they  may  be  kept  at  an  equable 
temperature  and  free  from  draughts.  The  size  of  this  room  may  of  course 
be  varied  to  suit  particular  requirements.  A cake  machine  and  whisk 
are  shown  on  the  first  floor,  but  these  and  other  machines  required  could 
easily  be  arranged  to  suit  amended  requirements.  The  doughs  are  allowed, 
after  being  made,  to  stay  on  the  second  floor  until  ready,  and  are  then  cut 
out  of  the  troughs  and  discharged  through  a hopper  on  to  the  moulding 
table  or  into  the  dividing  machine  on  the  floor  beneath.  The  machinery  as 
shown  is  driven  by  a gas  engine  fixed  in  the  one  corner,  from  which  runs 
a hne  of  shafting  along  the  wall. 

On  the  first  floor  are  the  divider,  cake  machine,  whisk,  the  moulding 
tables,  and  the  ovens.  Although  the  authors  are  advocates  of  draw- 
plate  ovens,  they  have  here  shown  a series  of  peel  ovens,  as  these  are  still 
largely  used  with  mixed  trades  such  as  this  bakery  would  be  suitable  for, 
but  draw-plate  ovens  could  be  arranged  if  preferred.  The  ovens  shown 
are  tw^o-deck,  fired  from  the  back,  and  should  preferably  have  separately 
fired  baking  chambers  giving  absolute  control  of  temperatures  (see  para- 
graph 756).  The  fuel  for  these  ovens  is  coke,  and  this,  on  being  brought 
as  usual  to  the  bakery  in  sacks,  is  hoisted  direct  to  the  third  floor  and  taken 
into  the  coke  store.  The  ashes  are  put  into  a portable  closed  sanitary* bin 
for  removal  once  every  twenty-four  hours.  This  bin  is  sent  down  bodily 
by  the  sack  hoist,  and  handed  over  to  the  dustman  on  the  occasion  ofpiis 
daily  visit.  At  the  far  end  of  the  stokehole  is  fixed  a small  vertical  boiler 
for  the  production  of  hot  w^ater  for  general  purposes.  The  flue  from  tlie 
ovens  is  carried  into  a chimney  stack  built  against  the  back  wall,  where  it 
cannot  become  a nuisance  to  neighbouring  property.  The  ovens  them- 
selves are  supported  on  girders  carried  between  the  back  wall  and  the  wall 
dividing  the  shop  from  bread  room,  and  resting  with  their  front  ends  upon 
a girder  carried  by  the  pillars  and  side  wall.  The  baked  bread  is  packed 
in  portable  racks,  and  taken  below  by  means  of  a lift  into  the  cooling  and 
delivery  room. 

From  the  cooling-room  one  would  naturally  hke  to  be  able  to  load  barrows 
and  carts  at  the  back,  but  this,  according  to  the  conditions,  is  impossible. 
Arrangements  have  therefore  been  made  for  delivering  through  the  side 
door.  A delivery  clerk  checks  the  bread  as  it  goes  out.  The  bread  racks 
should  not  exceed  2 ft.  in  width,  so  that  they  may  pass  each  other  in  the 
5 ft.  passage.  This  passage  might  be  used  at  night  for  the  purpose  of 
keeping  barrows,  as  some  six  or  eight  could  readily  be  stowed  away  in  it. 
A door  leads  direct  from  the  cooling-room  into  the  shop.  Through  this 
all  shop  goods  would  be  brought,  and,  if  foundjabsolutely  necessary,  bread 
barrows  could  also  be  filled  this  way  in  the  early  hours  of  the  morning,  in 
addition  to  the  use  of  the  side  entrance.  On  this’ floor  is  placed  the  office, 
which,  as  situated,  controls  the  shop,  the  sideTpassage,  cooling-room,  and 
delivery  clerk's  desk.  From  the  cooling-room,  through  a door  leading 
into  the  backyard,  are  reached  the  workmen's  lavatory  and  w.c.  With 
sufficient  space  at  the  rear  this  accommodation  might  well  be  enlarged. 

Such,  in  brief,  is  the  outline  of  the  bakery  and^shop  fitted  for  a large 
and  high-class  family  business  in  a first-rate  locality,  but  on  a"^  severely 
restricted  site.  The  exigencies  and  nature  of  the  business,  together  with 
the  actnal  size  and  proportions  of  the  premises,  must  all  affect  the  precise 


REFERENCES  TO  PLATE  IX. 


A.  Blending  Hoppers. 

B.  Flonr  Sifter. 

c.  Kneading  Machine. 

D.  Tempering  Tank. 

E.  Water  Tank. 

F.  Hoist. 

G.  Dough  Divider. 

H.  Cake  Machine. 

I.  Whisk. 

j.  Engine-room  and  Gas  Engine. 

K.  Lavatory  and  Cloak  Room. 

L.  Basement. 

M.  Men’s  Lavatory. 

Ah  Shoot. 

B^.  Water-heater, 
c^.  Stoke-hole. 

D^.  Two-deck  Peel  Ovens. 


N.  Wall  supporting  Ovens. 

o.  Side  Entrance. 

p.  Open  Yard. 

Q.  Delivery  Checking  Clerk. 

R.  Office. 

s.  Counter. 

T.  Tables. 

u.  Cooling  and  Delivery  Room. 
V.  Down  to  Lavatory, 
w.  Shop. 

X.  Lift. 

Y.  Hoist  Trap  Door. 

z.  Ferments  and  Sponges. 

Eh  Flour  Store. 

F^.  Dough  Room. 

Gh  Column. 


604 


Plate  IX. 


Plan  of  Shop  and  Overhead  Bakery. 


605 


606 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


nature  of  arrangements  in  each  individual  case.  Such  plans  as  are  here 
given  can  only  touch  on  the  general  principles  involved  in  the  arrangements, 
which  in  themselves  lend  themselves  readily  to  considerable  modification. 

699.  Bread  and  Cake  Factory  and  Automatic  Machine  Bakeries  in  General. 

— ^No  attempt  will  be  made  to  describe  the  buildings  and  equipment  suitable 
for  a very  large  business,  particularly  as  the  equipment  is  not  very  different 
to  that  which  forms  the  subject  of  this  paragraph.  The  plant  in  very  large 
bakeries  requires  to  consist  merely  of  more  units  rather  than  units  of  larger 
size  and  capacity.  It  may  be  said  at  once  that  modern  development  in 
Great  Britain  tends  to  replace  small  bakeries  by  others  of  medium  size  rather 
than  with  very  large  ones — the  latter  not  being  necessarily  at  a very  great 
advantage  over  the  former  owing  to  the  difficulty  and  expense  of  delivering 
bread  over  a very  large  area.  In  large  cities  it  would  be  better  policy  to 
erect  several  bakeries  of  medium  size  in  preference  to  one  large  bakery, 
and  with  centralised  office  management,  and  a good  organisation  to  super- 
vise the  various  bakeries,  there  is  the  less  reason  to  fear  ill  effects  from 
decentralisation  in  regard  to  manufacture;  because  with  the  automatic 
machinery  available  to-day  it  is  impossible  for  the  output  to  fall  short  of 
the  standard,  or  for  the  cost  to  exceed  the  same,  owing  to  the  automatic 
machines  acting  as  pacemakers.  It  is  necessary  of  course  to  have  efficient 
foremanship  in  each  bakery,  but  as  this  is  requisite  in  any  case,  there  is  no 
disadvantage  in  this  respect.  For  the  purpose  of  our  present  observations 
it  is  necessary  to  adopt  some  classification,  in  regard  to  the  size  of  bakeries, 
in  order  to  convey  some  idea  of  the  extent  to  which  the  specialisation  of 
machinery  and  equipment  should  be  carried. 

700.  When  Machinery  Pays. — It  is  one  of  the  most  important  questions 
when  designing  a modern  bakery  to  determine  exactly  how  far  the  provision 
of  machinery  should  go.  At  the  time  of  building,  when  a given  trade  has 
to  be  provided  for,  some  machines  may  not  be  worth  installing  which  it  is 
essential  to  have  in  a few  years’  time  when  trade  has  growm  to  proportions 
making  their  employment  highly  remunerative.  If,  however,  no  clear 
idea  of  this  possibility  exists  at  the  time  the  building  is  erected,  it  may  be 
impossible  to  provide  the  necessary  space,  or  to  make  suitable  arrangements, 
owing  to  the  later  wants  not  being  provided  for. 

The  standard  of  trade  for  a medium-sized  bakery  may  to-day  be  set 
at  approximately  500  to  700  sacks  (280  lbs.)  per  week,  because  this  is  the 
maximum  output  of  one  automatic  bread-making  plant  (see  paragraph  746). 
The  size  of  this  unit  is  determined  by  technical  considerations,  but  it  may 
be  accepted  for  our  purposes  that  2,400  2-lb.  loaves  per  hour  is  the  maximum 
output  of  an  automatic  plant  which  has  been  found  practicable.  If  a 
bakery  requires  to  deal  with  more  than  this  output,  more  than  one  plant 
must  be  installed.  The  limit  as  regards  maximum  output  per  week  having 
been  definitely  ascertained  by  multiplying  the  hourly  maximum  by  the 
weekly  working  hours  (examples  ; 2,400  2-lb.  loaves  per  hour=  12  sacks 
per  hour  x 60  hours  Avorking  per  Aveek  ==  720  sacks  ; or  2,400  IJ-lb. 
loaves  = 8 sacks  per  hour  x 50  hours  Avorking  per  Aveek  = 400  sacks  per 
AA'eek,  etc.,  etc.),  it  may  be  asked,  AA'hat  is  the  loAvest  output  per  AA'eek,  on 
Avhich  such  a plant  AA'ould  pay  ? The  ansAver  to  this  question  is  not  a simple 
one — many  considerations  go  to  determine  the  correct  course  in  each  in- 
dividual case,  but  it  can  be  affirmed  that  it  AA^ould  neAmr  be  advisable  to 
attempt  an  ansAA^er  Avithout  the  assistance  of  the  bakery  engineer  Avho 
specialises  in  automatic  machinery.  Taa'o  bakeries  Avith  precisely  similar, 
and  on  the  face  of  matters  perfectly  sufficient  outputs,  may  be  very  differently 
placed  as  regards  the  composition  of  their  respective  trades.  It  may  pay 
brilliantly  to  have  a full  installation  in  the  one  case  and  yet  not  in  the 


BAKEHOUSE  DESIGN. 


607 


other.  Such  matters  can  therefore  only  be  determined  after  full  investiga- 
tion of  the  whole  of  the  circumstances.  It  will  be  appreciated  that  the 
authors  can  only  lay  down  the  general  rules  which  should  be  followed, 
and  that  such  approximate  facts,  as  are  here  quoted,  apply  to  average  cases. 

The  minimum  trade  for  a full  automatic  plant  may  be  taken  at  250 
sacks  (280  lbs.)  per  week  of  reasonably  uniform  loaves.  On  this  output 
no  one  need  hesitate  as  to  the  remunerativeness  of  the  installation,  but 
it  may  be  here  remarked  that  owing  to  the  uniformly  better  bread  which 
would  result  under  tolerably  good  management  in  the  bakehouse,  an  increase 
in  the  sales  may  be  looked  for;  this  increase  will  be  all  the  greater  if  the 
sales  are  smartly  pushed,  although  that  is  not  what  is  here  meant — ^the 
increase  referred  to  is  automatic  and  due  to  a better  article.  To  the  un- 
initiated this  may  sound  “ too  good  to  be  true,’'  but  the  statement  is  never- 
theless based  upon  a well  authenticated  fact.  Any  one  installing  a plant 
on  a trade  of  250  or  300  sacks  will  therefore,  in  all  probability,  soon  have 
a larger  trade  Avitb  which  to  keep  it  employed,  and  all  increases  will  inevitably 
bring  down  the  cost  of  production  per  sack,  because  no  increase  in  the 
number  of  men  working  the  plant  is  required  for  working  it  to  its  fullest 
capacity. 

For  bakeries  with  trades  under  250  sacks  per  week  smaller  plants  are 
made,  both  as  regards  the  actual  machines  as  well  as  in  certain  combina- 
tions, by  reason  of  fewer  machines  being  employed  in  conjunction  with 
intermittent  working.  Thus,  a so-called  semi-automatic  plant  will  pay 
in  the  case  of  a fairly  uniform  trade  of  100  sacks  per  week  and  upwards, 
and  the  cost  per  sack  in  labour  will  be  only  fractionally  less  good  than  that 
obtained  from  full-sized  installations. 

Under  one  hundred  sacks  per  week  the  employment  of  a divider  and 
a “ Flexible  ” moulder  (that  is  a moulder  equally  adapted  for  turning  out 
tin,  cottage  or  coburg  bread  as  well  as  smalls)  will  pay  down  to  weekly 
outputs  of  60  or  70  sacks.  This  is  contrary  to  the  opinion  still  very  generally 
held,  but  as  actual  cases  exist  which  prove  the  statement,  the  authors  do 
not  hesitate  to  give  it  all  the  weight  they  can  command. 

Under  100  (one  hundred)  sacks  per  week  no  up-to-date  bakery  should 
be  without  at  least  a divider,  provided  the  machine  is  designed  on  the 
proper  principles,  and  does  not  fell  or  otherwise  injure  the  dough.  It  is 
no  use  employing  a machine  merely  for  the  sake  of  having  a machine,  and 
many  a user  loses  in  reduced  quality  all  and  more  than  he  can  save  in  labour. 
Good  modern  dividers  are  very  accurate,  much  more  so  than  any  commer- 
cially obtainable  hand-scaling,  they  act  as  pacemakers,  and  are  absolutely 
reliable  machines  if  looked  after  with  reasonable  care  and  kept  clean. 

Bakers  with  trades  no  greater  than  25  sacks  per  week  in  bread  should 
by  no  means  assume  that  a divider  will  not  pay ; even  on  such  comparatively 
small  outputs  as  25  sacks  (280  lbs.)  per  week  these  machines  pay  well  in 
many  instances.  It  may  be  taken  that  a suitable  divider  will  pay  in  any 
business  doing  a reasonably  uniform  bread-trade  and  employing  three  men. 

701.  Large  Bakeries. — Returning  now  to  the  subject  of  large  bakeries, 
and  having  determined  upon  the  nature  of  auto -machinery  to  be  installed, 
the  question  of  ovens  should  next  engage  attention.  The  subject  of  ovens 
is  fully  dealt  with  elsewhere  (paragraphs  749  et  seq.),  and  for  factory  working, 
i.e.  wholesale  production,  no  type  can  to-day  be  really  seriously  considered 
in  Great  Britain  other  than  the  draw-plate  oven — or  perhaps  in  Scotland 
and  some  parts  of  Ireland,  the  “ Coverplate  Oven.”  The  size  of  baking 
plate  must  be  determined  to  suit  the  style  of  loaf.  Cottages,  coburgs  or 
tins,  are  most  conveniently  dealt  with  in  one  sack  batches  and  on  plates 
with  a maximum  width  of  6 ft.  “ Oven-bottom  ” or  close-set  bread,  if  not 


608 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

in  association  with  any  of  the  first-named  varieties,  can  be  handled  perfectly 
with  plates  up  to  8 ft.  6 in.  in  width,  as  can  also  “ Scotch  Bread.'’  Batches 
may  be  taken  to  vary  from  one  sack  cottage  to  sack  “ Scotch  ’’  batches, 
but  to  illustrate  the  procedure,  we  will  adopt  the  former  as  a standard. 
Assuming  a full  size  auto-plant  to  be  decided  upon,  this  will  have  an  output 
in  2-lb.  loaves  of  12  sacks  per  hour.  The  ovens  will  bake  continuously 
one  batch  per  hour — hence  12  one-sack  drawplate  ovens  will  be  required 
in  such  a bakery. 

The  preceding  remarks  (in  paragraph  700)  refer  mainly  to  machines 
dealing  with  the  dough  after  it  has  left  the  kneading  machine.  Naturally, 
hoists,  sack-cleaners,  blenders,  storage  hoppers,  sifters,  tempering  tanks, 
and  kneaders  have  all  to  be  considered  ; but  as  these  have  been  longer 
on  the  market  and  are  better  understood  generally  than  the  automatic 
plants,  and  are  also  fully  referred  to  in  their  respective  chapters,  no  special 
reference  is  here  made  to  them. 

The  authors  have  advisedly  enlarged  upon  the  auto  plants  because 
they  are  to-day  the  key  to  successful  designs  for  large  bakeries,  and  because 
no  architect  can  be  properly  instructed  as  to  the  nature  of  buildings  required, 
before  the  bakery  proprietor  is  quite  clear  as  to  his  requirements  in  regard 
to  machinery.  The  architect  who  has  had  anything  to  do  with  modern 
machine  bakeries,  will  agree  that  his  clients  do  best  first  to  consult  the 
bakery  engineer,  who  will  prepare  such  plans  and  particulars  as  will  alone 
make  it  possible  for  him  to  give  his  client  a perfectly  designed  bakery. 

This  may  be  a new  order  of  things,  but  it  is  undoubtedly  necessary  to 
prominently  advise  the  above  course  if  mistakes  are  to  be  avoided,  and 
the  authors  consider  no  other  apology  necessary  for  introducing  so  lengthy 
a preface  to  the  following  description. 

702.  Modern  Bread  Factory. — The  drawings  on  Plate  X show  a well-de- 
signed modern  bakery  for  bread  and  confectionery,  with  an  output  up  to  7C0 
sacks  (280  lbs.)  in  bread  per  week.  The  site  is  assumed  to  have  been  chosen 
with  due  regard  to  distribution  of  the  output  among  customers.  It  should 
therefore  lie  as  centrally  in  the  district  to  be  served  as  possible,  and  if  in 
a hilly  country,  as  far  as  practicable  above  such  district.  As  it  is  more 
difficult  to  give  a good  plan  with  access  to  a street  on  one  side  only,  such 
a case  has  been  chosen.  Everything  is  kept  as  compact  as  possible,  so 
that  the  design  may  give  some  idea  as  to  the  minimum  space  required. 
The  scheme  is  such  as  also  to  keep  the  cost  of  buildings  low,  because  money 
should  be  spent  on  the  equipment  which  is  the  money  maker,  rather  than 
upon  palatial  buildings,  or  extravagantly  large  or  costly  sites.  The  build- 
ings are  all  of  one  storey,  except  for  a sufficiently  large  flour  store  and  dough- 
ing  room.  Hence  buildings  are  light  and  cheap,  and  supervision  easy. 
As  such  a bakery  will  mostly  be  found  in  a town  of  some  size,  it  is  unnecessary, 
and  indeed  unusual  at  the  present  time  to  provide  for  flour  storage  on  a large 
scale,  unless  a speciality  is  made  of  blending  (see  paragraphs  725  to  728). 
It  is  better  to  have  the  flour  delivered  as  it  is  required  with  only  a few  days’ 
supply  in  hand.  Flour  blending  is  also  the  exception  rather  than  the  rule,  and 
because  adequate  means  for  blending,  storing  and  weighing  off  are  costly  and 
not  necessarily  remunerative,  they  have  not  been  shown  on  the  plan  under 
notice,  but  full  particulars  will  be  found  in  a separate  chapter.  The  flour 
is  shot  into  a hopper  on  the  floor  of  flour  store  from  bags  which  correspond 
to  the  unit  adopted.  For  one  sack  ovens,  two  sack  batches  would  be 
kneaded  and  two  sacks  of  flour  (280  lbs.  each)  would  be  the  quantity  shot 
into  the  hopper  (a).  An  elevator  conveys  the  flour  to  a sifter  ih)  shown 
in  the  doughing  room  and  fixed  above  the  kneader  (c),  or  in  one  with  it. 
The  tempering  tank  [d)  will  be  found  close  at  the  side.  The  dough  when 


BAKEHOUSE  DESIGN. 


609 


ready  is  discharged  into  movable  trucks,  which  remain  in  the  doughing 
room  until  sufficiently  proved.  That  stage  having  been  reached,  the  truck 
is  moved  to  the  hopper  (e)  in  the  dougli-room  floor,  and  the  dough  is  cut  out 
of  the  truck,  into  handy  pieces  not  exceeding  28  lbs.  each,  and  dropped 
directly  down  a shoot  (/)  into  the  hopper  of  the  dough  divider  {g) ; this 
machine  forms  part  of  the  automatic  plant  [h),  and  no  further  labour  is 
entailed  until  the  finished  loaves  emerge  and  are  placed  in  tins  or  upon 
setters  ready  for  the  ovens  after  a further  short  period  of  rest.  The  auto- 
plant will  obviously  require  to  be  run  at  a speed  to  suit  the  oven  capacity. 
On  the  plan  under  notice  6 two-deck  draw-plates  (^)  are  shown — these  will 
therefore  require  a batch  to  be  ready  every  5 minutes  in  order  to  give  the 
required  output  of  12  sacks  per  hour.  After  being  baked,  the  loaves  are 
swept  off  the  plates  on  to  tables  to  facilitate  rapid  handling  and  are  con- 
veyed to  the  bread  room  on  suitable  racks  fitted  with  wheels  and  castors. 

Such  a bakery  would  be  run  at  full  output  with  a staff  of  14  men  exclu- 
sive of  foreman — this  includes  taking  flour  from  flour  store  and  delivering 
the  bread  to  the  bread-room.  With  50  working  hours  per  week  and  includ- 
ing foreman,  this  would  give  40  sacks  per  man,  per  week,  and  is  easily 
possible  with  a uniform  trade,  totalling  600  sacks  per  week.  A simple 
calculation  will  show  that  by  working  the  ovens  and  machinery  longer 
hours  by  the  aid  of  more  men,  the  output  can  be  raised  without  increasing 
the  working  hours  per  man — for  instance  18  men  would  give  720  sacks, 
each  man  still  putting  in  50  hours  only. 

The  confectionery  department  is  shown  as  a separate  room,  fitted 
Avith  4 ovens  (built  in  two-deck  form),  each  with  a separate  furnace.  Cake 
machine  (g)  and  whisk  {k)  are  also  provided.  These  confectionery  ovens 
are  served  from  a stokehole  and  stack,  common  to  the  bread  ovens  as  well. 

Electric  motors  are  shown  for  tlie  purpose  of  providing  power  where 
required,  separate  motors  being  fixed  for  the  flour  hoist  {1),  the  doughing 
room,  the  auto-plant,  and  the  confectionery  department. 

The  other  arrangements  of  the  buildings  call  for  no  extended  comment, 
as  the  plan  will  give  all  information  required.  The  flour  and  doughing 
rooms  and  the  auto-plant  annexe  are  heated  by  hot  water.  The  stable 
yard  and  arrangements  are  adequate  for  a district  not  too  large  (as  is 
intended)  and  the  office  is  well  placed  to  control  all  inward  and  outward 
traffic. 

It  may  be  of  interest  to  add  that  the  plan  is  very  similar  to  that  of 
a midland  bakery,  aa  hich  has  been  in  very  successful  operation  for  nearly 
three  years,  and  to  the  entire  satisfaction  of  its  proprietor. 

The  extension  shown  in  dotted  lines  is  provided  more  Avith  a view  to 
the  possibility  that  the  trade  may  groAV  in  complication  than  to  enable  a 
greater  output  to  be  obtained.  It  Avill  be  clear  that  so  long  as  a 2-lb. 
loaf  trade  only  has  to  be  catered  for  the  calculation  of  oven  accommodation 
required  is  simple,  but  if  a change  to  a greater  number  of  varieties  or  a 
smaller  size  loaf  should  occur  in  tlie  course  of  years  serious  difficulty  might 
arise,  if  space  for  more  ovens  did  not  exist. 


R E 


Plan  of  Modern  Bread  Factory. 


Plate  X 


REFERENCES  TO  PLATE  X. 


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for  Confectionery. 


CHAPTER  XXIV. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT. 

703.  Sanitary  Considerations. — The  operations  of  kneading  and  working 
dough  involve  severe  manual  labour  in  a heated  atmosphere  ; it  is  impossible 
to  conduct  these  processes  without  more  or  less  contamination  of  the  bread 
with  emanations  from  the  skin  of  the  workers.  In  the  best  conducted 
bakeries  this  evil  is  reduced  to  a minimum  by  insistence  on  scrupulous 
cleanliness  on  the  part  of  the  workmen  ; still,  even  the  utmost  care  cannot 
entirely  abolish  the  evil.  For  the  strongest  of  sanitary  reasons,  both  on 
behalf  of  the  public  and  of  the  workmen,  operations  on  dough  demand 
mechanical  appliances  rather  than  manual  labour.  So  forcible  are  these 
reasons,  that  the  expense  of  kneading  machinery  and  its  convenience, 
compared  with  ordinary  manual  [processes,  become  merely  secondary  con- 
siderations. 

704.  Bakehouse  Machinery. — In  describing  the  machines  required  in  a 
bakery,  some  classification  will  be  necessary  ; it  is  therefore  proposed  to 
commence  with  an  account  of  the  various  sources  of  motive  power,  such  as 
steam,  gas,  and  other  engines.  Following  on  this  in  natural  sequence, 
the  means  of  distributing  power,  embodied  under  the  general  term  of  “ gear- 
ing,’' engage  attention.  It  is  then  proposed  to  take  the  flour  as  it  enters 
the  bakery  and  follow  its  history  through  each  mechanical  appliance  em- 
ployed, discussing  and  describing  each  in  detail.  In  this  latter  connection, 
hoists,  blending,  sifting,  kneading,  and  other  machinery,  as  well  as  ovens, 
will  be  included. 

705.  Motive  Power. — One  of  the  great  objects  of  machinery  is  to  spare 
workmen  from  severe  manual  labour.  There  are  comparatively  few 
machines  which  are  profitably  worked  by  hand,  and  a man  must  rightly 
be  regarded  as  by  far  the  most  expensive  source  of  power.  For  flour- 
sifting purposes  machines  may  be  obtained  which  work  well  by  hand 
power,  the  reason  being  that  comparatively  little  force  is  requisite  to  drive 
these  machines.  Various  kneading  machines  are  also  supplied  which  may 
be  driven  by  hand  ; but  it  is  more  than  doubtful  whether  any  hand  machine 
can  make  a mass  of  dough  with  the  total  expenditure  of  less  force,  measured 
in  foot-lbs.,  than  can  the  baker  working  direct  on  the  dough.  The  worker’s 
task  may  be  lightened  by  slowing  down  speed  by  means  of  gearing,  but  in 
such  cases  the  compensation  is  made  by  the  greater  demands  on  time.  In 
civilised  countries  hand-worked  machines  for  the  bakery  cannot  be  recom- 
mended, as  experience  proves  that  operatives  strongly  object  to  w'ork  the 
handle  of  a kneader. 

In  cases  where  steam  power  is  available,  that  of  course  forms  a useful 
and  convenient  mode  of  driving  machines.  Thus,  if  the  bakery  adjoins 
some  other  building,  such  as  a flour  mill,  it  is  economical  and  convenient 
(from  the  baker’s  point  of  view)  to  take  his  power  from  a steam  engine 
there  running,  provided  it  is  always  available  when  he  wants  it.  Or  if  he 
can  similarly  gain  access  to  a boiler  and  draw  off  high-pressure  steam  when- 

612 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  613 


ever  required,  it  will  be  well  to  fix  a small  steam  engine  and  run  it  as  a source 
of  power.  These  conditions  are,  however,  rare  ; and  certainly  the  laying 
down  of  a steam  plant,  consisting  of  boiler  and  engine,  is  bad  economy 
for  the  ordinary  baker’s  requirements.  The  keeping  up  of  a supply  of  steam 
requires  considerable  time  and  attention,  and  also  skill  and  experience  in 
handling  boilers  ; while  neglect  may  cause  serious  damage,  or  even,  in 
extreme  cases,  actual  explosion.  For  these  reasons  steam  engines  are 
comparatively  little  employed  in  bakeries. 

What,  then,  is  wanted  is  a source  of  power  that  can  be  started  at  a 
minute  or  two’s  notice  by  a man  not  necessarily  trained  as  an  engine  driver, 
and  which  can  be  as  quickly  stopped,  the  expense  of  the  source  of  power 
being  arrested  simultaneously.  Further,  the  motor  should  not  be,  even 
in  case  of  neglect,  of  a nature  such  as  would  lead  it  to  be  a source  of  danger 
to  the  employes  or  the  building.  These  requirements  are  met  most  fully 
by  both  gas  and  oil  engines,  and  especially  by  electric  motors. 

706.  Internal  Combustion  Engines. — Approximate  mixtures  of  gas  and 
air  on  being  ignited,  explode  with  considerable  force  and  generate,  in  so 
doing,  a large  amount  of  energy.  This  well-known  fact  underlies  the  prin- 
ciple of  every  explosion  engine,  and  applies  equally  to  any  gas,  from  what 
ever  source  it  may  be  obtained.  The  raw  materials  from  which  gas  for 
commercial  purposes  is  usually  produced  are  as  follows  : coal,  coke,  oil, 
oil  distillates,  and  alcohol.  All  these  are  in  everyday  use  on  a large  scale. 

Coal. — Gas  in  the  form  of  town’s  or  lighting  gas  (for  producer  gas,  see 
under  coke  gas)  was  the  first  to  be  used,  because  it  was  the  one  readily  and 
universally  available  commodity  when  the  internal  combustion  engine 
was  first  introduced.  It  is  still  the  most  convenient  (though  not  necessarily 
the  cheapest)  source  of  power  usually  available  for  the  bakery  where  electric 
power  is  not  obtainable  from  a public  supply.  It  is  of  course  supplied 
under  slight  pressure  from  public  mains  and  at  a charge  per  unit  of  volume. 
The  cost  of  gas  varies  considerably  according  to  locality,  as  a result  of  varia- 
tions in  the  cost  of  raw  material,  production,  and  distribution.  In  certain 
manufacturing  districts  another  form  of  gas  commonly  knovui  as  power  gas 
(Mond  system)  can  be  obtained  ; but  as  it  only  affects  small  areas  and  is 
intended  for  consumption  on  a very  large  scale,  passing  reference  is  made 
to  it  here  merely  for  the  sake  of  giving  a complete  account.  Its  cost  is  only 
a fraction  of  that  of  lighting  or  town  gas. 

Coke  and  Anthracite  Gas. — ^For  gas  produced  from  coke  or  anthracite 
a generating  installation  is  required  by  each  user  as  it  is  not  available  from 
a public  supply.  As  this  “ producer  ” plant  is  of  a simple  nature  and  not 
of  large  dimensions,  and  requires  no  gas  holder  or  storage  reservoir,  it  is  not 
a formidable  addition  to  the  machinery  responsibilities  of  an  establish- 
ment. It  is  also  not  very  costly,  and  as  the  gas  can  be  produced  at  a lower 
rate  than  that  of  a supply  of  town  gas,  its  adoption  is  justified  even  with 
comparatively  small  installations.  It  may  be  said  that  any  coke  gas  pro- 
ducer may  also  be  used  with  an  admixture  of  anthracite  coal,  or  purely  with 
anthracite.  The  only  difference  in  practice  is  that  the  use  of  anthracite 
entails  increased  deposits  of  tarry  matter  and  more  cleaning.  Anthracite 
yields  a richer,  and  therefore  more  powerful  gas,  but  for  use  with  coke  a 
slightly  larger  producer  compensates  for  this  difference.  Coke  is  therefore, 
where  cheaply  obtainable,  rather  the  cleaner  and  more  convenient  fuel  to 
use.  Producers  for  using  bituminous  coal  are  more  complicated  than  either 
of  the  above,  as  still  more  trouble  is  caused  by  tarry  substances — hence 
they  have  to  be  fitted  with  tar  extractors  and  are  suitable  only  for  installa- 
tions rather  larger  than  are  of  interest  to  bakery  proprietors. 

Oil. — ^Engines  using  oil  are  not  sufficiently  more  economical  than  coal 


614 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


or  coke  gas  engines  to  outweigh  the  convenience  of  the  latter.  They  are 
of  interest  in  outlying  districts — in  the  colonies  and  abroad  where  oil  is 
cheap,  and  other  fuels  are  either  dear  or  not  available.  The  explosive 
mixture  is  created  by  vaporisation  of  the  oil,  or  by  mechanically  pro- 
duced atomisation  in  combination  with  sharp  currents  of  air  in  suitable 
proportions.  Oil  engines  are  entirely  successful  and  reliable,  and  can  be 
safely  recommended  for  any  power  units  required  in  bakeries  where  gas  or 
electricity  are  not  available.  The  most  economical  principle  is  the  Diesel 
system,  which  also  dispenses  with  outside  means  for  igniting  the  charge, 
a high  compression  being  used,  the  temperature  of  which  is  sufficient  to 
cause  the  explosion.  This  type  of  engine  is,  however,  only  now  beginning 
to  be  put  generally  upon  the  market. 

Oil  Distillates,  commonly  available  under  the  titles  of  petrol,  benzoline, 
benzol,  etc.,  follow  much  the  same  lines  as  those  employed  in  the  oil  engine, 
but  are  commonly  applied  to  engines  with  very  high  speeds,  i.e.,  800  revolu- 
tions per  minute  and  upwards.  This  results  in  a very  light  and  compact 
engine  for  a given  power,  but  involves  considerable  gearing  down  to  yield 
speeds  suitable  for  bakehouse  shafting.  That  they  have  reached  a high 
state  of  perfection  and  reliability  cannot  be  disputed,  but  they  cannot  com- 
pare with  a good  oil  engine  for  lowness  of  fuel  consumption.  The  explosive 
mixture  is  almost  invariably  obtained  by  a spirit  spray  caused  by  the  suction 
of  the  engine  when  once  started,  and  the  apparatus  used  for  this  purpose 
is  known  as  the  carburettor.  Electric  ignition  is  now  universal  on  spirit 
engines,  and  is  usually  generated  and  governed  by  a “ Magneto."’  It 
is  natural  that  this  type  of  engine  is  used  almost  exclusively  for  power 
vehicles  owing  to  the  fact  that  the  fuel  required  lends  itself  most  readily  to 
vaporisation. 

Alcohol  is  used  precisely  in  the  same  manner  as  the  oil  distillates — in  fact 
any  spirit  engine  needs  but  slight  adjustments,  practically  confined  to  the 
carburettor  to  enable  it  to  be  run  on  alcohol.  Owing  to  the  heavy  excise 
duty,  and  consequent  prohibitive  cost,  alcohol  is  not  at  present  of  practical 
interest  in  Great  Britain  ; it  is,  however,  in  use  abroad  to  a considerable 
extent. 

The  above  introductory  remarks  on  the  fuels  available  for  internal  com- 
bustion engines  are  necessary  to  a proper  appreciation  of  their  importance 
to  the  industrial  world,  and  we  can  now  proceed  to  a short  description  of  their 
general  principles. 

707.  Working  Principle  of  Explosion  Motors. — ^The  only  system  we  need 
here  refer  to  is  that  which  is  universally  adopted  (for  want  of  a better), 
apart  from  engines  of  extreme  size  or  isolated  and  more  or  less  experimental 
exceptions.  It  is  known  as  the  “ Four  Cycle  ” or  “ Otto  ” principle,  so 
called  because  four  complete  stroke  of  the  piston,  which  derives  movement 
from  the  explosion,  are  required  before  another  explosion  can  be  made  use 
of,  i.e.,  in  an  engine  fitted  with  one  cylinder,  or  in  each  cylinder  in  an  engine 
fitted  with  more  than  one.  The  cylinder  is  a strong  metal  tube  with  a 
perfectly  smooth  and  perfectly  cylindrical  interior.  In  it  moves  a piston  not 
fitting  too  closely,  coupled  to  a connecting  rod  which  is  free  to  swivel  on  a 
pin  fixed  in  the  piston.  This  connecting  rod  is  coupled  at  its  outer  end 
direct  to  a crank  on  the  fly-wheel  shaft.  The  piston  has  several  peripheral 
grooves  on  its  outer  cylindrical  surface  ; and  a corresponding  number  of 
metal  rings,  which  in  their  natural  state  are  slightly  larger  than  the  interior 
of  the  cylinder,  lie  in  these  grooves,  on  which  they  form  a good  joint  vdthout 
being  tight.  When  sprung  into  the  cylinder  as  the  piston  is  originally  fitted 
in,  the  rings  press  against  the  cylinder  walls  and  form  agas-tight  joint,  while 
permitting  the  piston  to  reciprocate  in  the  cylinder.  Thus,  one  end  of  tho 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  615 


cylinder  is  closed  only  by  tlie  piston,  while  the  other  has  a solid  cover  or 
wall.  Assuming  the  piston  to  be  at  the  point  nearest  the  closed  end  of  the 
cylinder,  the  first  stroke  of  the  piston,  on  the  fly-wheel  being  turned,  will  be 
outwards,  i.e.,  towards  the  open  end  of  the  cylinder.  Two  valves  are  pro- 
vided in  the  cylinder  head — one  for  the  indrawing  of  explosive  liiixture, 
and  the  other  for  the  discharge  of  waste  gases  or  exhaust ; the  mechan- 
ism operating  these  valves  is  such  that  the  inlet  valve  opens  when  the  piston 
is  nearest  to  the  cylinder  head.  The  first  movement  of  the  piston  will  then 
cause  suction,  and  draws  in  explosive  mixture  until  the  inlet  valve  closes 
just  before  the  piston  comes  to  rest  on  reversing  the  direction  of  its  move- 
ment. Both  valves  then  remain  closed  throughout  the  second  (inward) 
stroke,  causing  the  mixture  imprisoned  in  the  cylinder  to  be  compressed ; 
as  the  piston  starts  on  its  third  (outw^ard)  stroke  the  mixture  is  fired,  prefer- 
ably by  an  electric  spark,  causing  an  explosion  wdiich  pushes  the  piston, 
as  the  only  part  that  will  yield  to  its  force,  violently  outwards  (third  stroke). 
Naturally  both  valves  remain  closed  during  this  third  or  working  stroke, 
but  as  the  piston  again  reverses  the  direction  of  its  movement,  the  outlet 
or  exhaust  valve  opens  and  allows  the  spent,  but  imprisoned,  waste  gases 
to  escape  by  the  exhaust  pipe.  The  energy  or  movement  imparted  by  the 
working  stroke  to  the  fly-wheel  is  sufficient  to  carry  the  piston  back  to  the 
closed  end  of  the  cylinder,  thereby  scavenging  the  interior  and  bringing 
the  piston  again  into  the  position  from  which  it  was  originally  started.  The 
same  cycle  then  repeats  itself  through  the  first,  second,  third  and  fourth 
strokes,  the  fly-w^heel  being  made  heavy  enough  to  overcome  the  resistance 
of  the  engine  between  working  strokes  (once  in  every  four  strokes,  or  two 
revolutions)  without  being  materially  affected  in  its  speed  of  rotation. 

The  above  is  the  principle  common  to  all  usual  types  of  explosion  motors, 
and  should  be  mastered  by  every  owner  and  user  of  such  engines. 

The  detailed  arrangements  vary  with  every  make  of  engine,  but  can  be 
clearly  followed  by  any  one  wdio  cares  to  examine  them  closely,  provided 
that  the  above  working  principle  has  been  thoroughly  grasped  and  is  kept 
in  mind.  Many  stoppages — so-called  breakdowns  and  apparent  whims 
on  the  part  of  engines — are  due  to  some  trifle  for  which  no  mechanic  is 
needed,  provided  the  user  will  don  his  “ thinking  cap  ""  for  a few  moments. 
In  buying  engines,  good  diagrams  and  working  instructions,  w^hich  should 
be  framed  and  hung  in  close  proximity  to  the  engine  when  fixed,  should  be 
insisted  upon.  No  good  purpose  can  be  served  by  singling  out  one  out  of 
the  many  engines  on  the  market  for  full  description  and  illustration  here. 
Progress  is  so  rapid  that  an  up-to-date  illustration  to-day  would  probably 
be  of  little  use  in  twelve  months"  time.  That  which  it  is  important  to  know 
has  been  fully  referred  to,  and  that  which  w^e  have  described  applies  alone 
to  all  makes. 

708.  General  Advice  on  Explosion  Motors. — The  following  points  may 
prove  useful  and  should  be  observed  when  purchasing  or  using  an  internal 
combustion  engine.  The  power  of  an  explosion  engine  is  limited  to  that 
which  is  obtainable  by  the  full  explosion  once  in  every  two  revolutions — 
the  ordinary  maximum  load  should  therefore  be  about  10  to  20  per  cent, 
under  this  maximum,  as  otherwise  there  will  be  no  reserve  whatever.  An 
overloaded  engine  will  pull  up  altogether,  as  if  the  speed  is  reduced  the 
power  given  out  falls  in  proportion.  Foundations  should  be  good,  since  a 
series  of  explosions  or  blows  keep  the  fly-wheel  in  motion  and  react  on  the 
foundations.  Little  extra  cost  is  involved  by  making  foundations  ample 
in  the  first  instance,  but  the  wear  and  tear  on  the  engine  and  its  smooth- 
ness in  running  are  greatly  improved  thereby.  Supply  pipes  for  gas  (if  from 
tovTL  supply)  should  be  larger  than  advised  by  makers  rather  than  smaller. 


616 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


as  gas  pressures  are  apt  to  be  occasionally  inadequate  to  keep  the  engine 
running  at  full  power. 

The  exhaust  should  be  taken  to  the  open  air,  and  if  at  all  likely  to  cause 
annoyance  to  neighbours,  should  be  effectively  silenced,  which  can  be  easily 
done  by  employing  a chamber  or  series  of  chambers  of  more  ample  dimen- 
sions than  the  exhaust  box,* which  alone  forms  part  of  the  makers’  standard 
equipment. 

Water  pipes  should  be  protected  from  frost,  especially  from  the  chance 
of  eold  winds  impinging  upon  them  in  exposed  spots.  The  cylinder  jacket 
should  be  fitted  with  drain  pipes  to  facilitate  the  easy  drawing  off  of  water, 
or  be  kept  heated  by  a gas  flame  under  same  during  frosty  weather,  when 
engine  is  not  at  work.  If  the  water  in  cylinder  jacket  should  freeze,  the 
latter  will  crack  and  will  need  to  be  renewed  at  considerable  cost.  Valves 
should  be  ground  in  regularly,  and  at  sufficiently  short  intervals  to  prevent 
them  from  getting  at  all  badly  worn  ; if  this  precaution  be  adopted  there 
will  never  be  much  trouble  in  keeping  them  gas-tight. 

Only  good  oils  should  be  used  for  lubricating  purposes — especially  on 
the  piston — in  larger  size  engines,  forced  lubrication  for  the  cylinders  should 
be  insisted  upon  when  buying  the  engine,  as  also  should  ring-lubricated 
bearings  in  all  engines.  Buy  only  engines  fitted  with  electric  ignition 
(magneto) . As  any  reader  who  possesses  an  engine,  otherwise  fitted,  already 
possesses  the  necessary  experience,  the  authors  refrain  from  further  reference 
to  the  earlier  and  now  obsolete  tube  ignition.  In  fixing  an  engine  never 
permit  a permanent  belt  drive  to  the  line  shaft,  but  insist  upon  an  engine 
pulley  wide  enough  to  provide  for  a fast  and  loose  pulley  on  the  line  shaft. 
Thus  the  engine  alone  can  be  started,  without  danger  to  any  one  in  the 
bakery.  The  striking  gear  should  be  arranged  to  work  from  outside 
the  engine-room,  as  much  to  ensure  that  whoever  starts  up  the  line  shaft 
can  satisfy  himself  that  no  one  will  thereby  be  endangered,  as  to  enable  the 
shafting  to  be  quickly  stopped  in  case  of  emergency  (see  paragraph  718). 

The  engine  fly-wheel  and  belting  should  be  efficiently  guarded,  but  in 
such  a manner  as  to  enable  the  protection  to  be  readily  removed  for  giving 
access  to  all  parts  when  the  engine  is  at  rest.  If  petrol  or  any  other  spirit 
is  employed  as  fuel,  the  official  regulations  in  regard  to  its  storage  and  hand- 
ling must  be  strictly  adhered  to  in  order  to  ensure  safety,  and  also  the  avoid- 
ance of  responsibility  in  case  of  accident. 

If  at  any  time  a bearing  should  run  warm,  remember  it  is  eheaper  to 
stop  the  engine  and  prevent  a seizure  than  to  risk  serious  damage  to  bearing 
or  shaft. 

All  oil  used  for  lubricating  purposes  must  be  kept  in  properly  covered 
receptacles  to  keep  out  dust  and  grit  ; oil  cans  should  be  kept  clean  for  the 
same  reason,  and  no  caps  should  be  left  off  bearings  or  lubricators  at  any 
time.  If  an  engine  is  not  working  well  find  out  the  cause,  or  call  in  an 
expert,  do  not  run  until  it  stops.  Never  let  the  engine  stop  with  the  main 
belt  on  the  fast  pulley  of  the  line  shaft ; and  never  attempt  to  start  the  j 
engine  unless  the  cylinder  jacket  is  full  of  water,  as  might  not  be  the  case  I 
if  the  cylinder  is  drained  during  frosty  weather.  ; 

The  above  general  observations  have  been  here  introduced  because  | 
they  are  generally  regarded  by  engine  makers  as  understood,  and  may  i 
therefore  not,  or  not  all,  form  part  of  the  instructions  they  issue  for  working  i 
their  engines.  In  other  respects,  and  especially  as  to  directions  for  starting,  | 
stopping  and  maintaining  their  engines,  all  good  makers  supply  a perfectly  j 
satisfactory  set  of  instructions,  and  there  is  therefore  no  need  for  further  | 
details  here.  f 

709.  Gas  Producers. — As  previously  stated,  gas  may  be  produced  on  the 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  617 


premises  for  power  purposes  very  remuneratively  for  large  as  well  as  small 
installations.  The  earliest  commercially  available  apparatus  was  that 
manufactured  under  the  “ Dowson  ''  patents  and  the  gas  produced  was 
stored  in  a gas  holder,  under  slight  pressure,  to  be  fed  to  the  engine  or 
engines,  in  much  the  same  manner  as  might  be  the  case  with  a miniature 
installation,  similar  to  the  large  plants  used  for  public  supplies.  The  gas 
produced  was  mainly  carbon  monoxide  enriched  by  hydrogen  and  possessing 
no  illuminating  power.  Of  late  years,  however,  the  much  more  compact, 
simple,  and  less  expensive  suction  gas  plant  has  been  brought  to  a high 
state  of  perfection,  and  would  be  the  only  kind  of  apparatus  to  come  under 
practical  consideration.  The  principle  underlying  the  gas  producer  is  to 
consume  the  fuel  at  a high  temperature  within  a boiler-shaped  receptacle 
over  a grate  to  which  the  air  supply  is  limited  and  strictly  under  control, 
so  that  only  enough  air  is  admitted  to  support  combustion  to  an  extent 
adequate  for  the  maintenance  of  the  requisite  temperature.  Under  these 
conditions,  that  proportion  of  the  fuel,  which  cannot  actually  burn  in  the 
producer  owing  to  want  of  air,  is  nevertheless  consumed  and  is  converted  into 
gas,  mainly  carbon  monoxide.  This  gas  leaves  the  producer  near  its  upper 
end  at  a high  temperature,  and  is  conducted  to  a vaporiser,  where  its  heat  is 
given  off  to  water,  which  surrounds  tubes  through  which  the  gas  passes.  The 
gas  is  thus  partly  cooled  and  enters  a further  chamber  filled  with  large 
pieces  of  hard  (or  foundry)  coke  through  which  it  percolates  while  under 
the  action  of  a descending  stream  of  water  sprayed  over  the  coke  column 
from  a “ rose  ''  above.  It  emerges  from  this  scrubber  thoroughly  cooled, 
and  freed  from  all  dust  and  many  other  impurities.  The  gas  after  leaving 
the  scrubber  enters  a purifier  in  which  layers  of  wood  chips  are  placed  with 
the  object  of  removing  the  moisture  carried  over  from  the  scrubber.  The  tarry 
matter,  which  is  contained  in  a volatile  condition  in  the  gas,  is  deposited 
to  a great  extent  in  the  scrubber  coke,  and  purifier  chips,  on  which  it  con- 
denses, hence  the  coke  in  the  scrubber  and  chips  in  the  purifier  require  to 
be  renewed  from  time  to  time.  From  the  purifier  the  gas  is  led  by  mains 
direct  to  the  engines.  The  greater  proportion  of  the  heat  carried  over  by 
the  gas  on  leaving  the  producer  or  generator  is  given  off  to  the  water  sur- 
rounding the  vaporiser  tubes  and  is  sufficient  to  generate  steam,  which  is 
injected  under  the  fire  grate  of  the  producer.  This  steam  is  essential  to  the 
good  working  of  the  plant  because  it  serves  the  threefold  purpose  of  cooling 
the  firebars,  preventing  the  formation  of  clinker,  and  enriching  the  gas  by 
the  hydrogen  formed  by  its  decomposition  and  interaction  with  the  carbon 
of  the  coke,  under  the  influence  of  the  intense  heat  of  the  fire. 

The  draught  required  to  support  combustion  in  the  producer,  and  con- 
vey the  gas  through  the  successive  chambers  referred  to  and  their  connec- 
tions, is  provided  by  the  suction  or  “ pull ''  of  the  engines  when  running, 
from  which  circumstance  the  apparatus  derives  its  title  of  “ suction  gas 
producer.”  That  this  working,  once  started,  will  continue  to  be  virtually 
automatic  so  long  as  the  producer  contains  fuel,  will  be  obvious,  as  also 
w'ill  be  the  fact  that  every  portion  of  the  plant  described  from  the  air  inlet 
of  the  producer  to  the  inlet  valve  of  the  engine  must  of  necessity  be  under 
a slight  vacuum.  Thus,  no  leakage  of  gas  outwards  can  possibly  occur 
and  all  danger  of  explosion  or  asphyxiation  is  avoided.  This  is  the  more 
desirable  as  carbon  monoxide  is  an  invisible  and  deadly  gas  which  has  no 
smell,  and  is  especially  dangerous  because  its  presence  cannot  be  readily 
detected.  Moreover  it  gives  no  warning,  as  one  inhalation  causes  instant 
insensibility  and  complete  helplessness.  Although  attention  is  drawn  to 
these  facts,  there  is  no  danger  whatever  from  the  use  of  such  plants  under 
ordinary  working  conditions,  and  it  is  only  necessary  to  use  care  when 
opening  out  portions  of  the  plant  for  cleaning  or  inspection  purposes.  The 


618 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gas  is  heavier  than  air,  and  will  therefore  lie  invisibly  in  the  lower  portions 
of  a plant  which  has  been  opened  out,  or  on  the  floor  of  the  producer  house, 
the  doors  and  windows  of  which  should  be  kept  open  whenever  the  apparatus 
is  taken  apart.  For  starting  up  a producer  plant,  a fire  is  lighted  on  the 
grate  of  the  generator  ; fuel  is  added  until  a good  solid  fire  has  been  obtained, 
when  the  generator  is  filled  to  its  normal  charge.  A fan,  driven  by  hand  or 
power,  is  fitted  to  the  generator  air  inlet,  by  which  the  fire  is  fanned  until 
the  gas  which  is  thus  given  off  has  been  forced  successively  through  the 
various  portions  of  the  plant  right  up  to  the  engines.  Test  burners  are 
provided  at  various  points  and  finally  at  the  engine,  so  that  the  gas  may 
be  lighted  as  soon  as  it  has  become  of  sufficient  strength  or  richness.  The 
test  burners  are  fitted  with  wire  gauze  coverings  which  must  never  be  allowed 
to  be  absent,  as  they  prevent  the  flame  from  being  drawn  into  the  apparatus 
and  causing  the  gas  contained  therein  to  be  ignited.  Once  gas  of  sufficient 
richness  has  been  forced  to  the  engine,  this  may  be  started  in  the  ordinary 
way,  from  which  moment  the  whole  will  continue  at  work  as  above  described. 

When  it  is  desired  to  stop  the  engines  the  gas  is  cut  off  at  the  generator 
and  a byepass  is  simultaneously  opened  to  a short  chimney  up  which  tlie 
gases  which  the  fuel  continues  to  produce  may  escape.  This  chimney  is  of 
sufficient  height  to  enable  the  fire  in  the  generator  to  keep  alight  from  one 
day  to  the  next,  assuming  the  working  to  be  intermittent,  so  that  very 
little  is  required  in  the  way  of  preparation  for  the  starting  up  of  the  engine 
or  engines  on  the  next  day. 

In  conclusion  it  may  be  safely  affirmed  that  suction  producer  plants  are 
quite  reliable  in  working,  require  no  undue  attention  or  skilled  manipula- 
tion, and  are  certainly  very  economical  in  operation.  The  gas-producing 
plant  has  no  moving  parts  apart  from  the  fan  for  starting  the  fire,  and  is 
not  subject  to  breakdown  without  notice.  The  only  parts  requiring  re- 
newal are  firebars  and  the  firebrick  lining  of  the  generator.  The  latter 
is  the  most  serious  item,  but  apart  from  occasional  repairs  of  a slight  nature 
opposite  clinker  doors,  replacement  is  only  necessary  at  long  intervals  ; a 
complete  relining  being,  in  the  case  of  well-designed  plants,  not  necessary 
more  often  than  once  in  about  every  five  or  seven  years.  The  necessity  for 
fresh  coke  in  the  scrubber  and  fresh  chips  in  the  purifier  is  not  treated  as 
a serious  matter,  as  both  renewals  are  inexpensive  and  are  not  necessary 
more  often  than  once  in  three  months. 

710.  Electric  Motors. — Undoubtedly  the  electric  motor  is  the  most 
compact  as  well  as  the  most  convenient  prime  mover.  Wlierever  electric 
current  is  available  at  a reasonable  cost  it  should  be  preferred  to  all  other 
means  of  obtaining  motive  power.  A judicious  arrangement  of  motors  will 
often  prove  at  least  as  cheap  in  running  cost  as  that  of  any  other  method.  The 
need  for  good  judgment  arises  out  of  the  fact  that  although  a motor,  while 
running  at  its  maximum  output,  may  cost  more  than  some  other  source  of 
energy,  yet  it  can  be  so  readily  started  and  stopped  that  it  proves  in  the 
end  cheaper  than  an  explosion  engine,  which  is  necessarily  left  to  run 
throughout  the  working  hours  in  a bakery.  The  electric  motor  should  in 
fact  be  in  motion  only  while  required  to  perform  actually  remunerative  work. 
To  merely  replace  an  engine  by  a motor  to  drive  a line  shaft  would  in  many 
cases  indirectly  involve  the  waste  of  much  current,  as  the  motor  would  be 
left  running  when  there  would  be  no  need  whatever  for  it  to  be  in  motion. 
The  best  plan  is  to  couple  such  machines  as  are  required  to  run  simultaneously 
— say  kneader  and  sifter,  or  divider  and  moulding  plant — and  let  each 
group  be  driven  by  its  own  separate  motor.  As  this  plan  obviates  all 
long  lengths  of  shafting,  it  frequently  does  not  prove  more  costly  to  instal 
than  one  motor  with  a great  deal  of  shafting,  etc. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  619 

Again,  the  hoisting  in  of  flour  frequently  takes  place  at  a time  when  no 
other  machinery  is  required  to  be  in  motion  ; the  same  holds  good  as  regards 
the  fewer  and  much  smaller  machines  required  in  the  confectionery  depart- 
ment, as  compared  to  the  bread  bakery. 

It  will  be  seen  that  if  the  stopping  of  the  machines  is  dependent  upon  the 
stopping  of  the  motor  no  waste  of  current  can  occur  without  mahce — a con- 
tingency which  need  not  be  taken  into  account  in  this  connection.  Illus- 
trations of  machines  with  direct  coupled  electric  motor  drives  are  given 
later  in  this  chapter. 

Some  hesitancy  in  adopting  electric  motors  existed  in  the  earlier  days 
of  public  electric  supplies,  and  not  without  reason,  owing  to  the  apparent 
delicacy  of  much  which  forms  part  of  electrical  machinery ; but  no  reason 
exists  to-day  why  any  one  should  hesitate  to  adopt  electrical  working  from 
any  fear  of  breakdowns.  Electric  motors  and  all  pertaining  thereto  are 
to-day  at  least  as  reliable  as  any  other  machinery,  and  types  of  motors  are 
now  available  (notably  the  totally  enclosed  machines)  which  are  eminently 
suitable  for  bakery  conditions.  As  with  internal  combustion  engines,  it  is 
advisable  to  have  each  motor  of  ample  power  for  its  work,  but  that  is  no 
more  necessary  in  these  cases  than  with  any  kind  of  machinery.  It  is  also 
not  so  very  long  ago  that  certain  alternating  currents  were  the  cause 
of  difficulties  in  motors,  but  any  lingering  suspicions  in  regard  to  these 
troubles  may  be  now  confidently  dismissed.  The  authors  know  of  no  cur- 
rent commercially  available  in  Great  Britain  that  cannot  be  safely  relied 
on  for  bakery  purposes. 

Any  attempt  to  explain  the  principles  of  the  various  electric  motors 
which  may  have  to  come  under  consideration  would  be  of  far  too  technical 
a nature  to  come  within  the  scope  of  this  work ; the  authors  have  therefore 
confined  themselves  to  the  purely  practical  aspects  of  their  application  to 
bakeries,  and  must  leave  all  matters  of  detail  to  the  local  electricity  depart- 
ment or  the  consulting  electrical  engineer. 

711.  Gearing  and  Power  Transmission. — The  problem  of  transmitting 
power  in  a bakery  is  practically  confined  to  the  conveyance  of  rotary  motion 
from  one  shaft  to  another.  This  transmission  of  power  may  require  to 
take  place  from  a prime  mover  to  a machine,  or  group  of  machines,  or  it 
may  involve  distribution  over  a building  covering  considerable  distances. 
In  the  latter  case  electrical  distribution,  as  described  in  the  last  paragraph, 
provides  the  best  solution  of  the  problem,  whether  current  be  available  from 
a public  supply,  or  has  to  be  generated  on  the  premises.  No  knovm  means 
can  compare  for  efficiency  and  convenience  with  electrical  driving,  if  the 
points  at  which  power  is  required  are  numerous  and  at  all  widely  separated 
by  distance.  The  determination  of  the  best  arrangements  for  electrical 
distribution  cannot,  however,  be  laid  dowm  conveniently  within  the  space 
available  in  this  work.  The  power  scheme  must,  moreover,  be  entirely 
adapted  to  the  requirements  of  each  case,  and  this  is  too  complicated  a 
matter  to  be  adequately  undertaken  as  a piece  of  general  advice.  Ti  e 
average  bakery,  however,  does  not  call  for  anything  very  elaborate,  and 
the  authors  propose  to  confine  their  remarks  to  the  forms  of  gearing  usually 
required. 

712.  Shafting. — For  driving  a group  of  machines  from  one  common 
source  of  power,  a sufficient  length  of  shaft  is  employed  to  enable  pulleys 
to  be  fixed  thereon,  opposite  to  the  driving  pulleys  of  the  machines  which 
are  to  be  set  in  motion.  This  shaft  is  commonly  called  a line  shaft.  If 
subsidiary  shafts  are  required,  either  to  enable  a further  group  of  machines 
to  be  supplied  with  power  or  for  other  reasons,  such  shafts  are  called  counter- 
shafts. The  shafting  itself  is  now  usually  of  mild  steel,  it  should  be  true  in 


620 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


diameter  and  perfectly  straight,  and  in  lengths  suited  to  the  actual  require- 
ments. In  determining  the  lengths,  it  should  he  borne  in  mind  that  20  ft. 
forms  the  maximum  which  is  practicable  ; that  the  couplings  used  for  join- 
ing up  the  various  lengths  forming  a line  shaft  should  as  far  as  possible  be 
close  to  bearings,  and  that  as  few  pieces  of  shaft  as  possible  should  be  em- 
ployed to  make  one  line  shaft. 

A shaft  will,  for  a given  size,  transmit  power  proportionately  to  its  speed 
of  revolution,  hence  the  higher  the  speed  the  smaller  the  diameter  required 
to  transmit  a given  power.  There  are,  however,  various  reasons  why  the 
speed  should  be  kept  within  limits,  among  these  it  is  sufficient  to  mention 
the  two  most  important.  The  first  is  that  bakery  machines  require  on  the 
whole  low  speeds,  and  have  therefore  to  be  designed  with  considerable  gear- 
ing in  themselves,  so  that  their  driving  pulleys  shall  be  capable  of  running 
at  a reasonably  high  speed.  Too  high  a line  shaft  speed  would  therefore  call 
for  badly  proportioned  belt  drives.  The  second  reason  is  that  great  care  is 
necessary  in  arranging  high  speed  line  shafts,  especially  because  very  careful 
balancing  of  all  pulleys  fixed  thereon  is  necessary  to  prevent  excessive 
vibration.  It  may  be  taken  that  the  most  suitable  speed  for  line  shafts 
in  bakeries  is  from  140  to  160  revolutions  per  minute.  The  diameter  of  a 
line  shaft  must  therefore  be  proportioned  in  such  a manner  that,  at  this 
speed  it  is  capable  of  safely  transmitting  the  power,  it  is  intended  to  convey, 
to  all  the  machines  that  will  be  driven  from  it. 

713.  Surface  Friction  Bearings. — A good  type  of  bearing  is  one  which 
has  a white  metal  running  surface,  is  fitted  with  an  oil  well,  and  has  ring 
lubrication.  Many  makes  exist  which  possess  these  features,  and  the  task 
of  selecting  the  cheapest  and  most  efficient  should  be  considered  to  belong 
to  the  province  of  the  bakery  engineer.  “ Ring  lubrication  is  a fairly 
modern  innovation  in  spite  of  its  effectiveness  and  simplicity,  and  as  it  is 
the  best  and  most  automatic  device  for  ensuring  the  continuous  lubrication 
of  bearings,  a short  description  must  here  be  given.  The  bearing  is  so  con- 
structed that  under  the  lower  running  surface  a reservoir  or  chamber  is 
formed  which  is  filled  with  oil  up  to  a given  level.  At  each  end  of  the  bearing 
surface,  but  within  the  casing,  an  annular  space  surrounds  the  shaft  for  the 
purpose  of  allowing  a ring,  usually  formed  of  stout  wire  or  fiat  metal  strip, 
to  hang  on  the  shaft.  The  diameter  of  this  ring  is  considerably  greater 
than  that  of  the  shaft,  thus  permitting  the  lower  portion  of  the  ring  to  dip 
into  the  oil  contained  in  the  oil  well  or  reservoir.  As  the  shaft  revolves 
the  ring  revolves  also,  and  in  so  doing  conveys  the  oil  from  the  well  to  the 
shaft  and  over  the  top  in  a continuous  supply.  The  oil  thus  conveyed  is 
much  more  than  is  required  by  the  bearing,  which  therefore  is  always  per- 
fectly lubricated  so  long  as  the  reservoir  contains  oil,  but  as  the  surplus  all 
flows  back  to  the  well,  one  charge  lasts  for  a very  long  time,  and  there  is 
absolutely  no  waste. 

The  bearing  described  is  so  good  and  reliable  and  withal  so  inexpensive 
that  all  older  types  are  now  entirely  obsolete,  and  should  on  no  account  be 
fitted  for  new  installations. 

714.  Rolling  Friction  Bearings. — Even  better  types  of  bearings  are 
provided  by  roller-  and  ball-bearings.  Surface  friction  being  entirely 
absent  in  these,  they  absorb  considerably  less  power,  and  are  therefore  more 
economical.  Several  good  makes  exist  and  are  absolutely  trustworthy,  and 
tliere  can  be  no  question  that  where  first  cost  is  not  a governing  considera- 
tion, their  adoption  in  preference  to  all  others  must  be  recommended,  as 
the  additional  cost  is  undoubtedly  more  than  saved  by  the  economy  effected 
in  power. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  621 


715.  Bearing  Supports. — Bearings  are  carried  in  a variety  of  ways — 
in  a wall  box,  fixed  in  a wall  at  the  end  of  a line  shaft,  or  where  it  passes 
through  a wall  ; in  a wall  bracket  which  is  bolted  to  a wall ; in  a hanger 
suspended  from  a ceiling,  or  in  pedestals  supported  on  a fioor,  pier,  or  girder. 
A detailed  description  of  these  various  fittings  can  scarcely  be  necessary, 
but  one  essential  should  be  insisted  upon  with  all.  That  is,  that  all  bearing 
supports  should  be  of  the  so-called  self-adjusting  type,  which  means  that 
the  actual  bearing  shall  not  be  rigidly  bolted  to  a fixed  surface,  but  should 
be  so  supported  by  adjustable  screws,  that  the  exact  alignment  of  the  shaft 
may  be  readily  obtained  by  the  use  of  the  screws,  which  are  then  secured 
by  lock  nuts.  The  alignment  of  a shaft  should  be  perfect,  otherwise  it  will 
absorb  infinitely  more  power  in  being  driven,  and  may  be  even  subject  to 
breakage,  or  seizing  in  bearings.  It  is  not  sufficient  to  line  up  a shaft  properly 
when  it  is  new — a very  slight  settlement  in  the  building,  or  the  heavy  load- 
ing of  upper  floors  may  destroy  the  original  alignment,  and  ready  means  for 
readjustment  are  therefore  necessary. 

For  similar  reasons,  bearing  supports  should  preferably  be  carried  from 
the  solid  walls  of  a building.  A floor  may  be  of  ample  strength  to  carry 
the  weight  it  has  to  bear  in  everyday  use,  but  it  can  never  be  absolutely 
rigid.  The  floor  of  a flour  store,  for  instance,  may  carry  many  hundreds  of 
tons  of  flour,  and  do  so  with  perfect  safety,  yet  its  deflection  will  vary  accord- 
ing to  the  load — just  in  the  same  way  that  the  best  and  strongest  modern 
bridge  is  designed  to  deflect  under  its  moving  load.  A shaft  supported  in 
hangers  from  such  a floor  vdll  obviously  follow  its  movements,  and  can 
therefore  never  be  in  perfect  alignment,  except  possibly  when  the  load 
corresponds  exactly  to  that  which  existed  when  the  alignment  was  made. 
These  variations  may  not  and  are  not  likely  to  be  serious  enough  to  endanger 
the  actual  working  of  the  shafting,  but  they  must  cause  the  absorption  of 
more  power  than  under  ideal  conditions  would  be  the  case.  It  follows  that 
hangers  and  pedestals  carried  on  upper  floors  should  be  avoided  as  far  as 
possible,  although  they  may  be  used  quite  properly  for  short  lengths  of 
shafting. 

Bearing  supports  should  be  placed  only  after  careful  consideration  ; in 
all  cases,  either  so  that  they  can  be  quite  close  to  the  pulleys,  or  so  that  the 
machines  can  be  fixed  to  bring  the  pulleys  close  to  the  supports.  This  is 
very  important  in  bakeries,  because  owing  to  the  peculiar  nature  of  bakery 
machines,  high  belt  speeds  cannot  be  conveniently  arranged  for,  and  the 
belts  have  consequently  to  be  kept  fairly  tight,  especially  as  space  is  also  of 
great  importance  and  shaft  centres  are  as  a rule  not  as  widely  apart  as  would 
otherAvise  be  desirable.  For  the  same  reasons,  the  bearings  should  not  be 
too  far  apart — it  is  advisable  to  limit  the  distance  of  bearings  from  one 
another  to  6 ft.  in  2 and  2J-in.  shafts,  7 ft.  in  2J  in.,  and  8 ft.  in  3 in.  shafts. 
Smaller  shafts  than  2 in.  should  not  be  employed.  Attention  is  again 
drawn  (see  paragraph  684)  to  the  desirability  of  avoiding  piers  on  the  inside 
walls  of  buildings — so  that  there  should  be  no  hindrance  to  the  fixing  of 
bearing  supports  on  the  plain  wall  surfaces  in  such  a manner  as  to  enable 
unrestricted  compliance  with  the  above  considerations. 

Each  complete  length  of  shaft  should  be  fitted  with  collars  at  each 
end  of  one  bearing  only,  in  order  to  suitably  limit  side  play.  The  collars 
should  have  no  projections,  so  that  the  danger  of  attendants"  clothes  being 
caught  up  may  be  avoided.  The  same  remarks  apply  to  couplings  for  join- 
ing up  the  several  lengths  forming  one  line  shaft.  • 

716.  Pulleys. — All  pulleys,  except  the  fast  and  loose  pair,  from  which 
the  line  shaft  derives  motion,  should  be  split — that  is  to  say  made  in  halves, 
so  that  changes  and  additions  can  be  made  without  having  to  take  down  or 


622 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


disturb  the  shafting.  The  fast  pulley  should  be  keyed  on  and  the  loose 
pulley  should  be  self-oiling  and  slightly  smaller  in  diameter  than  the  fast, 
to  reduce  the  belt-pull  when  running  idle.  Except  the  fast  pulley,  no  pulley 
should  be  keyed  on  to  the  shaft  ; the  use  of  self -gripping  (preferably  “ screw 
boss  ”)  pulleys  ensures  the  shaft  remaining  undamaged  and  avoids  the 
necessity  for  cutting  key  ways.  In  fixing  “ screw  boss  ''  pulleys,  care  should 
be  taken  to  place  these  on  the  shaft  in  the  correct  way,  which  is  of  course 
that  which  ensures  that  the  belt -pull  will  keep  the  screw  boss  tightened. 
For  reversing  shafts,  screw  boss  pulleys  are  useless — other  self -gripping 
pulleys  must  be  used  in  such  cases.  For  the  speeds  above  recommended 
(140  to  160  revolutions  per  minute)  cast-iron  pulleys  may  be  used  through- 
out. All  pulleys  should  be  crowned,  except  loose  pulleys,  and  arranged  to  be  of 
as  large  a diameter  as  circumstances  will  permit.  The  speed  of  shafts  are  in 
inverse  proportion  to  the  diameter  of  the  pulleys  on  each,  hence  the  diameter 
of  pulleys  required  to  drive  one  shaft  from  another  at  a predetermined  speed 
is  readily  ascertained  by  an  ordinary  proportion  or  “ rule  of  three.” 
Example  : an  engine  shaft  runs  at  200  revolutions  per  minute  and  the  line 
shaft  is  required  to  revolve  at  140.  If  an  existing  pulley  of  24  in.  on  the  engine 
has  to  be  taken  into  consideration,  then  as  120  ; 200  : : 24  : 40  = diameter  of 
pulley  on  line-shaft.  If  choice  can  be  made  without  reference  to  an  existing 
pulley,  first  decide  upon  the  maximum  diameter  that  is  possible  (or  desir- 
able) for  that  pulley  which  is  limited  by  its  surroundings,  and  proportion 
the  others  as  before. 

The  reason  why  pulleys  require  to  be  as  large  as  possible  is  that  the 
power,  which  a given  belt  can  transmit,  is  proportionate  to  the  speed  at 
which  it  travels,  and  therefore  the  higher  the  belt  speed  the  greater  is  the 
power  the  belt  can  transmit  ; or  inversely,  to  transmit  a given  power,  the 
higher  the  speed  of  the  belt  the  smaller  is  the  belt  required.  It  is  necessary 
to  bear  in  mind  that  owing  to  the  greater  circumference  of  the  larger  pulley , 
the  belt  speed  is  higher  with  larger  diameters  than  with  small,  in  direct 
proportion  to  the  increase  in  diameter,  the  pulley  or  shaft  speed  remaining 
constant.  It  follows  that,  assuming  a machine  to  have  been  fitted  with  a 
pulley  inadequate  to  absorb  the  necessary  power  for  driving  it  (which  will 
show  itself  by  persistent  tendency  of  the  belt  to  slip  or  run  off  in  spite  of 
machine  and  line  shaft  being  perfectly  lineable),  the  correct  remedy  is  to 
increase  the  size  of  the  pulleys  on  the  machine  and  on  the  line  shaft  in  the 
same  proportions.  This  alteration  Avill  leave  the  speed  of  the  machine 
unchanged,  but  will  at  once  remedy  the  defect,  if  the  increase  in  belt  speed 
is  sufficient.  To  double  the  belt  speed  will  doulble  its  capacity  for  conveying 
power  and  so  on  in  proportion. 

717.  Belting. — For  all  ordinary  purposes  leather  belting  is  recommended 
for  bakeries.  A good  dressing  (such  as  “ Clingsurface  ”)  periodically 
applied  should  be  used  sparingly  and  will  act  as  a dressing  and  keep  the 
belting  in  good  condition.  Resin  and  other  forcible  means  of  increasing 
adhesion  should  be  avoided.  The  best  makes  of  bakery  machines  are 
designed  for  ample  widths  of  belts,  which  therefore  give  no  trouble  from 
slipping,  and  if  reasonably  long  centres  (distance  from  shaft  to  shaft)  are 
allowed,  need  not  be  kept  unduly  tight.  For  joining  up  the  ends  of  belts 
“ Harris  ” fasteners  are  very  convenient  and  hold  excellently,  if  properly 
put  on.  The  ends  of  the  belt  should  be  marked  off  exactly  true  with  a car- 
penter’s square,  and  cut  perfectly  clean  and  at  right  angles.  Next  see  that 
the  belt  is  properly  round  the  pulleys  and  shafts  which  are  to  be  connected. 
Then  turn  the  belt  so  that  the  inside  lies  uppermost,  and  place  the  joint 
down  on  the  fasteners  with  the  teeth  upwards  without  any  twists,  and  place 
the  ends  of  the  belt  in  exactly  their  right  places  on  the  same.  Get  some 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  623 


•assistance  to  hold  the  belt  in  exactly  the  right  position,  and  drive  the  leather 
down  on  to  the  teeth  of  the  fasteners.  With  the  joint  properly  made  there 
is  no  danger  of  the  fastener  tearing  out. 

Do  not  use  the  hammer  direct,  but  employ  two  blocks  of  wood  used 
■endways  to  the  grain — the  one  block  should  form  the  bed,  the  other  should 
be  firmly  pressed  on  to  the  belt  close  to  the  joint.  Thus  the  leather  will  be 
driven  into  the  teeth  by  the  agency  of  the  wood,  under  the  blow  from  the 
hammer,  without  damage  to  the  teeth.  Be  careful  not  to  eliminate  the 
curve  given  to  the  fasteners  by  the  makers.  Drive  the  fasteners  home  with 
as  few  heavy  strokes  of  the  hammer  as  possible  in  preference  to  many  light 
taps,  which  only  cause  the  fangs  of  the  fasteners  to  be  loosened  in  the  leather. 
Another  excellent  means  of  joining  belts  is  to  use  a specially  prepared  flexible 
wire — ^this  is  sold  with  suitable  tools  for  punching  the  necessary  holes  in 
the  belt,  under  the  name  of  “ Malin  ""  outfit.  “ Harris  fasteners  are  use- 
less where  the  belt  is  bent  in  both  directions,  as,  for  instance,  when  taken 
over  guide  or  “ jockey  ""  pulleys  ; in  such  cases  ordinary  lacing  or  wire  lacing 
must  be  employed. 

The  most  common  application  of  a belt  for  the  transmission  of  power 
is  found  in  the  case  of  two  parallel  shafts  running  in  the  same  direction. 
In  mounting  a belt  observe  the  arrangement  of  the  joints,  i.e.,  the  places 
Avhere  the  separate  lengths  of  leather  from  which  the  belt  is  made  are  con- 
nected together.  The  belt  should  be  put  on  so  that  the  trailing  end  of  each 
piece  last  reaches  the  pulley — a moment’s  reflection  while  examining  the 
belt  will  make  the  reason  for  this  plain.  When  joining  up  a belt  with  leather 
lacing,  the  ends  should  be  pared  down  in  order  to  make  a “ scarfed  ” joint 
of  uniform  thickness.  This  should  be  arranged  so  that  the  joint  follows 
the  same  direction  as  others  in  the  same  belt.  If  double  belts  are  used 
it  might  be  difficult  to  obtain  a satisfactory  “ scarfed  ” joint,  and  the  ends 
should  be  butted  and  a separate  piece  of  belt  laced  on,  jointly  to  both  ends 
on  the  outside  of  the  belt,  i.e.,  not  touching  the  pulleys  ; thus  an  even  inner 
surface  will  result.  In  joining  up  the  ends  of  a new  belt  considerable  allow- 
ance must  be  made  for  stretching  : it  is  not  possible  to  give  exact  instructions 
as  to  the  amount  of  such  allowance,  but  a very  little  experience  will  provide 
the  necessary  judgment.  In  any  case  a new  belt  will  stretch  further  than 
can  be  allowed  for  in  first  joining  up,  and  will  need  “ taking  up  ” after  it 
has  been  at  work  for  a little  while  ; with  newly  installed  machinery  it  is 
therefore  as  well  to  go  carefully  round  all  belts  before  starting  up  the  day’s 
work — this  precaution  requires  but  a few  moments  and  will  save  the  incon- 
venience and  loss  of  a stoppage  during  working  hours. 

It  should  be,  but  actually  is  not,  superfluous  to  here  advise  that  sufficient 
belting  should  be  kept  in  stock  (not  kept  in  a hot  place),  together  with 
fasteners,  laces  (wire)  and  tools,  to  enable  repairs  to  be  quickly  executed 
when  necessary. 

If  it  is  desired  to  drive  two  parallel  shafts  in  opposite  directions,  the  belt 
is  put  on  “ crossed,”  i.e.,  it  must  run  from  the  under  side  of  one  pulley  to 
the  upper  of  the  other.  Shafts  at  right  angles  to  one  another  can  be  driven 
by  belting  quite  satisfactorily,  if  the  one  is  above  the  other  at  a sufficient  dis- 
tance to  give  a reasonable  length  of  “ drive.”  The  pulleys  are  arranged  in  such 
a manner  that  the  belt  leaving  the  “ driven  ” pulley  has  a central  lead  to  the 
“driver,”  and  equally  on  leaving  the  “ driver  ” pulley  leads  centrally  on  to 
the  “ driven  ” again.  The  shafts  and  pulleys  must  be  accurately  fitted 
s-nd  can  only  work  in  just  the  one  way  which  ensures  correct  leads  ; but  the 
condemnation  of  such  drives  which  one  occasionally  meets  with  is  not 
justified,  and  arises  out  of  unsatisfactory  experiences  due  to  badly  arranged 
gearing.  Properly  proportioned  and  erected,  the  so-called  “ quarter  twist 
drive  ” may  be  as  satisfactory  as  any  other  belt  drive. 


624 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

To  enable  a machine  to  be  driven  which  has  to  stand  well  away  from 
the  wall,  or  to  get  into  an  adjoining  room,  or  for  other  reasons,  a belt  drive 
may  be  required  to  run  over  guide  or  “ jockey  ” pulleys.  The  plan  is  not 
a good  one  and  is  unsuitable  for  considerable  powers,  but  if  well  arranged 
may  prove  quite  satisfactory  for  light  work.  It  should  only  be  employed 
Avhere  other  means  are  not  available,  and  should  then  be  so  arranged  that 
the  belt  is  not  required  to  be  very  tight  in  order  to  transmit  the  necessary 
power. 

Before  turning  from  the  subject  of  shafting,  bearings  and  pulleys,  it 
may  be  useful  to  call  attention  to  a point  very  commonly  overlooked.  The 
power  absorbed  by  the  shafting  itself,  that  is  to  say,  before  the  brake  horse 
power  or  power  actually  given  off  by  the  prime  mover  can  become  available 
at  tlie  machines,  is  very  considerable.  One  short  length  of  shafting  of  course 
does  not  require  a startling  amount,  but  it  may  be  considered  a safe  rule  not 
to  allow  less  than  2 to  3 h.p.  in  fixing  upon  the  size  of  the  prime  mover, 
when  making  provision  for  the  requirements  of  the  average  bakery  (with, 
say,  20  to  30  ft.  of  shafting).  In  larger  establishments,  however,  involving 
shafting  in  three  or  four  and  even  more  different  places,  the  power  absorbed 
“ on  the  way  ''  to  the  machines  is  much  more  considerable  and  requires  to 
be  carefully  gone  into.  There  are  many  bakeries  where  the  power  required 
for  driving  the  hoist  on  the  top  floor  (for  getting  the  flour  in  during  the  day, 
when  it  is  the  only  machine  for  which  the  engine  is  being  run)  is  three  and 
four  times  as  large  as  the  power  required  by  the  hoist  itself.  A similar 
condition  of  affairs  can  often  be  found  in  bakeries  when  a small  whisk  or 
cake  machine  in  the  confectionery  department  causes  an  engine  and  a great 
deal  of  shafting  to  be  kept  running  for  the  best  part  of  the  day.  Seeing  that 
a better  scheme  might  in  many  cases  avoid  this  considerable  and  continual 
waste  of  power,  it  will  be  clear  that  even  for  matters  of  quite  simple  and 
everyday  practice  it  may  be  wiser  to  be  guided  by  the  advice  of  competent 
])akery  engineers,  rather  than  ostensibly  to  save  a few  pounds  by  merely 
buying  individual  machines  and  having  the  rest  of  the  instalKtion  put  to- 
gether in  an  amateur  fashion. 

Cases  have  been  met  with  where  owners  have  quite  erroneously  blamed 
machines  for  absorbing  a great  deal  more  pownr  than  w'as  possible,  from  no 
other  cause  than  that  stated  above.  It  is  the  fashion  to  inquire  into  horse 
]:>ow'ers  and  wnigh  all  kinds  of  pros  and  cons  wdth  much  care,  but  this  is 
w'orse  than  useless  if  a supposed  saving  of  a little  power  in  a machine  is  to 
be  nullified  by  badly  designed  accessories  or  transmission  arrangements. 
The  fact  is,  that  as  regards  power  absorbed  by  machines,  the  user  may  wnll 
leave  that  subject  to  the  engineers  ; it  will  pay  him  better  to  confine  his 
inquiries,  wdien  selecting  machines,  to  the  question  of  their  efficiency  for 
his  daily  w^ork.  The  machines  that  will  pay  him  best  are  those  which  pro- 
duce the  finest  article — no  matter  wLat  their  price  may  be  or  the  horse  pow'er 
they  absorb — especially  as  it  is  rather  in  the  nature  of  things,  that  the 
machine  w hich  punishes  the  dough  least  is  also  likely  to  use  the  least  horse 
power. 

718.  Striking  Gears. — For  shifting  the  belt  from  a loose  pulley  to  a fast 
pulley,  or  vice  versa,  a fork  is  used,  by  means  of  which  the  belt  is  pushed 
sidew'ays  until  it  has  changed  its  position  on  the  pulleys  as  desired.  The 
fork  should  make  contact  with  the  belt  at  a point  as  near  to  the  pulley  as 
possible,  and  ahvays  so  that  the  belt  runs  from  the  point  of  contact  to  the 
pulley.  The  gear  for  actuating  the  fork  should  be  such  that  it  locks  itself  in 
the  “ on  and  “ off  positions,  and  all  striking  gears  should  be  readily  acces- 
sible, so  that  shafting  or  machines  may  be  stopped  as  quickly  as  possible  in 
case  of  emergency.  Where  the  starting  of  a line  sha-ft  involves  the  starting 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  625 


of  any  running  gear  out  of  sight  of  the  person  operating  the  gear,  a bell 
should  be  fitted  so  that  it  may  be  rung  as  a warning  before  the  shafting  is 
set  in  motion.  Fast  and  loose  pulleys  should,  however,  be  provided  for  each 
sub-section  of  shafting,  so  that  each  may  be  quickly  stopped  in  case  of 
emergency.  This  has  the  further  advantage,  that  very  frequently  much 
running  of  sub -sections  may  be  saved  when  only  a portion  is  required  to 
be  in  motion. 

719.  Rope  Driving. — In  place  of  belts  ropes  are  at  times  employed. 
In  these  cases  the  rope  runs  in  a V-shaped  groove  in  the  pulleys.  The  same 
rule  as  to  relative  speed  applies  to  rope  drives  as  to  leather  belts.  Rope 
possesses  an  advantage  in  that  it  can  be  bent  in  any  direction,  and  thus  a 
drive  may  be  taken  round  corners,  when  power  has  to  be  transmitted  in  a 
direction  other  than  at  right  angles  to  the  line  of  shafting.  With  very 
long  drives  ropes  are  preferable  to  belts  ; when,  for  instance,  a yard  has 
to  be  spanned,  to  carry  power  from  one  building  to  another.  The  rope 
should  then  be  supported  at  intervals  on  “ jockey  pulleys,  and  if  passing 
through  the  open  air  should  be  protec  ted  from  wet.  There  are,  however,  not 
likely  to  be  many  cases  in  connection  with  bakeries  where  a rope  drive  is 
really  necessary,  and  it  must  be  borne  in  mind  that  it  is  not  possible  to 
arrange  for  fast  and  loose  pulleys  with  a strike  gear.  If  a rope  drive  is 
required  to  be  so  arranged  that  it  can  be  stopped,  a clutch  is  necessary,  and 
it  is  better  to  avoid  the  necessity  for  such  complications  if  possible. 

720.  Chain  Driving. — An  excellent  and  quite  modern  development  of 
power  transmission  is  the  chain  drive.  It  is  suitable  for  very  short  centres, 
should  be  of  the  “ silent  chain  type,  and  be  arranged  to  run  in  a casing 
with  an  oil  bath,  and  can  be  relied  upon  absolutely.  It  can  also  transmit 
very  considerable  powers,  and  although  expensive  to  instal,  will  .last  for 
many  years  if  suitably  proportioned.  Needless  to  say,  it  can  only  be  em- 
ployed for  parallel  shafts  running  in  the  same  direction. 

721.  Gear  Wheel  Drives  are  entirely  satisfactory  if  properly  designed 
and  made.  Even  spur  wheels  (for  parallel  shafts)  and  bevel  wheels  (for 
shafts  at  various  angles)  can  now  be  made  virtually  silent,  but  as  these 
devices  are  expensive  and  need  special  designing  to  suit  each  case,  they 
should  be  avoided  as  far  as  possible.  In  any  case,  no  general  data  can  be  of 
sufficient  use  to  justify  the  large  amount  of  space  which  would  be  required 
to  deal  with  this  subject  adequately.  It  is  best  when  apparently  faced 
with  problems  of  this  kind  to  place  the  matter  in  the  hands  of  the  bakery 
engineer. 

722.  Special  Drives. — There  is  one  special  double  crank  gear  contained 


Fig.  48.  “The  Almond”  Right-Akgie  Drive. 


626 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

in  an  oil-tight  casing,  to  enable  the  working  parts  to  run  in  a bath  of  oil, 
which  is  so  compact  and  useful  in  occasional  awkward  cases  that  it  deserves 
special  attention.  It  is  sometimes  imperative  to  place  a machine  in  a posi- 
tion at  right  angles  to  that  in  which  it  was  designed  to  work  ; it  may  be 
impossible  to  drive  it  by  a quarter  twist  belt  or  by  an  arrangement  with 
“ jockey pulleys.  The  “ Almond  right  angle  drive,  of  which  an  illustration 
is  given.  Figure  48,  then  steps  into  the  breach  admirably  by  enabling  an  ordi- 
nal open  belt  drive  to  be  converted  by  its  use  into  a drive  at  right  angles. 
As  it  is  within  the  knowledge  of  the  authors  that  this  gear  works  well, 
without  any  trouble,  for  a number  of  years  it  would  appear  to  be  an 
apparatus  which  can  be  safely  recommended. 

723.  Lubrication  and  Maintenance.— The  modern  device  for  ensuring 
lubrication  has  already  been  fully  dealt  with  as  regards  bearings  and  loose 
pulleys  for  shafting.  The  older  methods  are  not  referred  to,  as  modern 
developments  and  advice  for  future  conduct  alone  form  the  subject  of  this 
chapter  on  machinery.  It  may  be  as  well,  however,  to  say  that  oil  is  con- 
sidered the  only  suitable  lubricant  for  shafting,  at  least  in  the  opinion  of 
the  authors,  as  solid  grease  lubricant,  excellent  as  it  is  for  bakery  machines 
proper,  involves  more  constant  attention  than  can  be  relied  upon  v here 
bearings,  etc.,  are  out  of  reach  and  in  inaccessible  places.  That  no  preju- 
dice exists  against  solid  lubricants,  will  appear  quite  clear  after  a perusal 
of  the  description  of  bakery  machines.  In  connection  with  lubrication, 
special  attention  requires  to  be  drawn  to  the  necessity  for  using  bearings 
from  which  leakage  or  overflow  is  impossible  ; as  this  is  obvious,  nothing 
further  need  be  said. 

As  to  maintenance,  it  cannot  be  sufficiently  insisted  upon  that  the  only 
proper  course  is  to  appoint  two  men  specially,  whose  duty  it  shall  be  to 
carry  out  certain  specified  duties  periodically.  The  bakery  proprietor 
should  keep  a book  in  which  he  enters  these  duties  in  full— set  out  in  un- 
equivocal language — ^he  should  add  further  items,  as  experience  shov  s up 
weak  spots,  so  that  these  may  be  safeguarded  in  future,  and  he  should 
satisfy  himself  that  the  person  appointed  has  attended  to  his  duties  at  the 
specified  times  in  a proper  manner.  The  object  in  appointing  two  men  is 
to  provide  against  emergencies.  There  will  then  always  be  at  least  one 
competent  person  available  to  do  the  work,  if  each  of  the  two  is  made  to 
take  the  duties  referred  to  for  alternate  months. 

The  task  of  preparing  the  book  of  instructions  is  not  so  formidable  as 
might  appear  at  first  sight.  The  manufacturers  of  ovens,  machines  and 
motors  provide  (or  should  provide)  proper  instructions ; and  if  these  are 
taken  as  a basis,  and  common  sense,  assisted  by  the  engineers,  be  used,  com- 
plete rules  will  not  be  difficult  of  compilation.  That  the  maintenance  of 
the  proprietor’s  plant  should  be  properly  organised  by  the  proprietor  must 
be  evident,  because  that  course  is  absolutely  indispensable  in  his  own  interests. 
It  is  no  use  to  blame  the  men  when  something  has  gone  wrong  ; it  would 
be  much  better  for  the  proprietor  to  blame  himself  for  not  having  made 
adequate  provision  against  contingencies.  If  this  sensible  course  is  followed, 
the  proprietor  will  soon  find  a remedy,  which  will  never  be  the  case  if  the 
matter  is  simply  left  in  the  hands  of  the  men. 

As  regards  upkeep  of  shafting  and  gearing  generally,  the  authors  fear 
that  the  majority  of  users  rarely  trouble  themselves  until  defects  force 
themselves  upon  their  notice.  They  have  already  said  that  spares  for  repairs 
of  belts  should  always  be  kept  handy.  It  is  now  suggested  that  shafting 
is  as  much  an  essential  of  an  installation  as  the  engine  or  the  machines,  and 
that  it  and  all  its  appurtenances,  as  well  as  engine  and  machines,  should  be 
kept  absolutely  clean.  If  cleaning  is  properly  done  from  day  to  day  it  is 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  627 

done  in  an  astonishingly  short  time.  If  it  is  neglected  until  gear  has  to  be 
“ dug  out ''  it  is  nearly  a hopeless  task.  No  proprietor  should  be  satisfied 
^^dth  his  bakery  unless  shafting  and  all  machinery  be  left  perfectly  clean 
inside  and  out  at  the  conclusion  of  the  day's  work.  This  is  no  counsel  of 
perfection  ; there  are  plenty  of  bakeries  in  which  this  is  done,  but  there 
are  far  more  in  which  it  is  otherwise.  This  cleanliness  is  not  only  essential 
for  the  proper  upkeep  of  the  machinery,  but  it  is  indispensable  from  a 
hygienic  point  of  view,  as  well  as  from  the  business  standpoint.  Let  each 
bakery  o\^er  throw  his  bakery  open  to  public  inspection  all  day  and  every 
day,  and  if  it  be  kept  in  the  condition  in  which  it  should  be,  this  plan  vdll  not 
only  compel  the  proper  appearance  and  condition  of  the  establishment,  but 
will  prove  the  best  possible  advertisement.  In  such  cases  where  this  plan 
has  been  tried,  it  has  given  excellent  results  and  has  led  to  increase  of  busi- 
ness. 


724.  Flour  Hoisting, — Flour  being,  for  reasons  explained  in  paragraph 
693,  usually  stored  at  the  top  of  the  building,  adequate  means  for  hoisting 
are  among  the  primary  requirements  of  a power-driven  bakery.  In  many 
cases  a covered  cartway  is  formed  in  connection  with  the  bread-room  either 
within  the  four  walls  of  the  main  building  or  as  shovm  at  T,  on  Plate  X. 

In  the  former  case  square  holes  are  cut  vertically  above  one  another 
through  every  intermediate  floor,  in  such  a position  that  the  loaded  flour 
lorry  can  be  conveniently  placed  immediately  under  the  openings.  Each 
floor  opening  should  be  fitted  with  hinged  flaps,  normally  completing  the 
floor  and  preventing  all  danger  from  open  holes.  These  flaps  should  be 
stoutly  constructed  and  made  to  hinge  upwards  ; a hole  is  cut  in  the  centre  of 
the  joint  between  the  two  large  enough  to  allow  the  cast-iron  weight-ball, 
which  serves  for  causing  the  hoisting  chain  or  rope  to  descend,  to  pass  un- 
obstructedly . The  trap-doors  should  be  railed  off,  but  if  this  is  not  per- 
rnanently  possible,  movable  guard  rails  should  be  placed  in  position  each 
time  the  hoist  is  used,  to  prevent  risk  of  injury  to  passers-by.  If  the  flour 
sacks  are  to  be  hoisted  outside  the  main  building,  the  pulley  over  which 
the  hoisting  rope  passes  is  supported  on  a projecting  beam  or  cathead.  To 
prevent  the  flour  from  getting  wet  and  to  avoid  the  admission  of  cold  air 
into  the  flour  store  as  far  as  possible  the  cathead  should  be  enclosed,  and  a 
continuation  of  this  enclosure  should  be  carried  right  down  to  within  a 
convenient  distance  of  the  lorry  ; where  the  lorry  stands  in  a covered  yard, 
this  enclosure  or  trunking  {usually  called  a ‘‘  lucombe  ")  merges  into  the 
roof  of  the  yard  and  is  joined  to  the  same  in  such  a manner  as  to  be  water- 
tight. Wherever  the  lucombe  gives  access  to  a floor,  Le.,  at  each  floor  to 
which  flour  is  intended  to  be  hoisted,  trap-doors  as  described  should  be 
fitted,  thus  practically  avoiding  all  danger  to  operatives  in  “ landing  " the 
sacks  and  detaching  them  from  the  hoisting  rope.  The  centre  of  the  hoisting 
rope  should  be  clear  of  projections  by  about  2 ft.,  and  the  internal  dimensions 
of  a lucombe  should  not  be  less  than  4 ft.  square. 

The  Sack  Hoist  itself,  except  in  such  rare  cases  where  it  may  be  direct 
coupled  to  an  electric  motor,  should  preferably  be  of  a type  employing  a 
friction  drive.  There  are  various  hoists  upon  the  market  which  are  quite 
satisfactory,  but  none  are  simpler,  more  efficient  and  reliable,  free  from 
necessity  of  repair,  or  easier  to  work  than  the  one  here  illustrated.  Fig.  49. 

, The  driving  pulley  will  be  seen  close  to  the  frame  to  the  left  of  the  illus- 
itration,  it^can  be  driven  in  either  direction  by  arranging  an  “open"  or 
. drive.  It  usually  runs  free,  and  is  therefore  a loose  pulley. 

I he  hoisting  drum,  grooved  to  take  the  highly  flexible  steel  wire  rope,  is 
•pressed  to  the  right  into  the  brake  drum  by  a spring  contained  in  the  pro- 
j jection  shown  to  the 'left  of  the  framing.  The  drum  is  therefore  normally 


628 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Fig.  49. — Sack  Hoist. 

and  automatically  “ on  the  brake.^’  A slight  movement  of  the  lever  on 
the  right  disengages  the  drum  from  the  brake  and  allows  any  suspended 
weight  (the  ball  shown  is  sufficiently  heavy)  to  descend.  On  letting  go  the 
lever  the  drum  instantly  returns  to  the  brake  and  comes  to  a stop.  A 
slightly  greater  movement  of  the  lever  than  that  referred  to  engages  the 
other  end  of  the  hoisting  drum  with  the  pulley  and  causes  the  hoisting  rope 
to  be  wound  in,  thus  raising  any  weight  attached  thereto.  The  action  is 
quick,  safe  and  noiseless  and  allows  of  very  delicate  handling.  These 
hoists  have  been  in  constant  use  for  very  many  years  and  are  capable  of 
hoisting  hundreds  of  sacks  of  flour  per  week  each.  They  are  made  in  various 
sizes,  to  suit  the  length  of  lift  and  for  weights  up  to  5 cwts. 

The  fixing  of  the  hoist  is  “uni  versa!’ ’—that  is  to  say  it  may  be  fixed  to 
suit  practically  any  local  requirements.  The  best  plan  is  to  hoist  direct 
from  the  drum,  as  each  pulley  over  which  the  rope  has  to  run  means  wear 
and  tear  to  the  latter.  In  practice  the  lever  is  of  course  worked  from  a hand 
rope  carried  to  a convenient  position.  v j r 

The  hoist  shown  is  fitted  with  a wire  rope,  but  it  can  also  be  supplied  tor 
use  with  a chain.  The  rope  is,  however,  rather  the  safer  appliance  because 
it  will  not  break  without  warning.  The  wear  of  a wire  rope  can  be  readily 
detected  by  the  gradual  breaking  of  the  strands.  As  the  broken  ends  stick 
outwards  and  are  sharp  as  needles,  the  occasional  passing  of  the  bare  l^nd 
along  a wire  rope  will  soon  draw  attention  to  wear.  A rope  is  sound  so 
long  as  tlie  surface  is  smooth  to  the  touch  all  along  its  length.  Chaiiis  do 
not  necessarily  give  any  sign  of  weakness,  as  this  does  not  arise  merely  from 
wear  as  to  thickness  of  links  ; chains  harden  in  use  and  may  snap  from  this  I 
cause  without  notice.  It  is  therefore  necessary  with  all  chains  at  leastj 
once  annually  to  dismantle  the  same  and  send  them  to  be  annealed.  -Yny  j 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  629 


ordinary  smith  or  engineer’s  shop  should  be  able  to  perform  this  very  neces' 
sary  operation,  which  is  not  difficult  but  requires  to  be  conscientiously  done* 
The  rope  pulleys  must  be  properly  designed  to  prevent  damage  to  the 
rope — it  is  best  to  obtain  them  from  the  engineers  who  specialise  in  these 
hoists  ; not  only  is  the  shape  of  groove  important,  but.  also  the  diameter 
of  pulleys — both  must  be  suitable  to  ensure  a reasonable  length  of  life  to  the 
rope.  Hoists  should  be  planned  so  as  to  reduce  the  number  of  rope  pulleys 
employed  to  a minimum.  The  hoist  is  fitted  with  Stauffer  solid  grease 
lubrication,  and  the  same  method  should  be  employed  for  the  pulleys. 

Hoisting  Speeds  must  vary  according  to  circumstances  ; 60  ft.  per  minute 
is  quite  sufficiently  fast  for  short  lifts,  such  as  from  one  flour  to  another,  but 
speads  up  to  200  ft.  per  minute  may  be  employed  for  long  lifts. 

The  Hoisting  Power  varies  of  course  with  the  speed  and  weight,  but  for 
the  average  bakery  it  may  be  taken  that  to  provide  approximately  2-3 
h.p.  will  be  sufficient. 

725.  Flour  Storage  and  Flour  Blending. — There  can  be  no  doubt  that 
the  aeration  of  flour  before  use  in  the  bakehouse  is  beneficial  as  regards 
quality  of  bread  produced,  and  that  if  it  is  carried  out  efficiently  and  in 
conjunction  with  judicious  blending  of  different  grades  of  flour,  an  advantage 
can  be  obtained  in  regard  to  quality  of  the  blend  over  the  market  price,  or 
inversely  a profit  be  made  if  a given  quality  be  taken  as  the  standard. 

To  realise  these  advantages  to  the  full  is,  however,  by  no  means  easy,  and 
involves  a great  deal  of  good  judgment.  It  may  be  taken  that  the  process 
pays  only  with  considerable  outputs  or  exceptional  judgment — or  both. 

Many  so-called  blending  plants  are  not  remunerative,  some  are  even 
directly  harmful.  This  principally  applies  where  use  is  largely  made  of 
worm  conveyors,  which  are  most  objectionable  because  they  create  dust, 
due  to  the  friction  inseparable  from  their  use.  It  must  be  obvious  that  it 
is  absurd  to  spoil  good  flour  in  this  manner  after  the  miller  has  gone  to  end- 
less trouble  and  expense  to  eliminate  dust  and  make  his  flour  as  granular 
as  possible  ! 

With  modern  developments  of  milling,  blending  has  not  the  importance 
in  an  average  bakery  in  this  country  which  once  attached  to  it.  The 
important  exceptions  are  where — 

1.  The  large  bakery,  properly  equipped,  specialises  in  the  matter  of 

blending  and  really  deals  with  the  question  on  scientific  lines. 

2.  The  small  bakery  where  the  proprietor  or  manager  possesses  special 

knowledge  and  experience,  and  by  personal  good  judgment  can 
ensure  that  it  pays  him  to  blend. 

In  all  other  cases,  the  millers  can  be  relied  upon  for  supplies  of  good 
blends,  if  judicious  selection  be  made  in  buying  for  the  requirements  of  the 
business. 

726.  Blending  Plant  for  large  Bakery. — ^There  is  no  compromise  possible 
for  the  large  bakery  that  requires  a blending  plant.  An  elaborate  and 
I somewhat  expensive  installation  alone  will  serve  the  purpose,  and  headroom  is 
! necessary  to  avoid  objectionable  conveyors.  On  Plates  XI  and  XII  two  cases 
! are  dealt  with.  The  first  shows  a plant  for  storing  three  blended  mixtures 
i of  flour  which  can  then  be  used  at  will ; but  owing  to  limited  height  a conveyor 
’is  employed  for  distributing  the  flour  to  the  storage  hoppers.  The  second 
‘ shows  the  same  plant,  but  so  arranged  that  by  the  partial  raising  of  the  roof 
^inclined  shoots  replace  the  conveyors.  This  second  arrangement  reduces 
ithe  use  of  conveyors  to  a minimum  ; they  are  only  employed  for  discharging 
^Ithe  flour  from  the  hoppers  to  the  automatic  weighers,  and  so  do  a minimum 
^of  harm. 


Flour  Blending  Plant. 


Plate  XI 


Flour  Blending  Plant. 

Another  Arrangement. 


Plate  XII. 


631 


632 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


A short  description  of  this  plant  follows  : i • r j x 

The  blender  is  fixed  under  the  floor  of  the  flour  store,  and  is  fed  from 
the  same  It  is  a “ Pfleiderer  ” universal  blender,  and  therefore  a batch— 
and  not  a continuous— machine.  The  batch  machine  is  the  only  one  tliat 
can  give  a true  blend ; continuous  machines  are  only  approxiimte  and  do 
not  give  that  perfect  blending  which  alone  is  of  real  value.  The  various 
grades  of  flour  are  fed  into  the  blender  in  predetermined  proportions,  say 
four  sacks  of  one,  three  of  a second,  and  one  of  a third  quality.  The  machine 
sifts  and  aerates  the  flour  as  it  is  fed  in.  The  plant  shown  would  hare  an 
output  of  about  thirty  sacks  per  hour.  From  the  blender  the  flour  is  ele- 
vated to  the  highest  point,  and  from  there  descends  or  is  conveyed  as  thecase 
may  be  to  one  of  the  three  storage  hoppers.  Valves  control  the  dehr  ep 
as  desired.  The  storage  hoppers  have  a capacity  of  about  eighty  sacks 
each  but  can  of  course  be  varied  in  size  to  suit  requirements. 

The  stirrers  fitted  in  the  base  of  the  hoppers  ensure  uniform  delivery 
and  prevent  packing  or  arching,  the  final  conveyor  shoots  deliver  the  flour 
in  a constant  stream  to  the  automatic  weighers.  These  discharge  into 
sifters  where  the  flour  is  finally  cleaned  and  aerated  before  descending 
into  tiie  kneading  machines  on  the  first  floor.  The  whole  of  the  gear  is 
operated  from  the  first  floor  and  is  handily  accessible  when  using  the  knead- 
ers,  so  far  as  drawing  supplies  from  the  hoppers  - is  concerned  The  blend- 
ing operations  and  all  pertaining  thereto  are  carried  out  on  the  third  fioor^ 
In  this  country,  the  bread  being  made  during  the  night,  there  is  no  one 
then  on  the  second  or  third  floors— the  blending,  hoisting  in  of  the  Ao” 
all  attendant  operations,  are  therefore  carried  out  during  the  day  Mhen  the 

bakery  proper  is  not  at  work.  .oinr 

Photographic  views  of  this  plant,  showing  storage  hoppers,  eleiator 
and  blender  hopper  (Fig.  60).  blender  elevator,  automatic  weighers,  etc.  (Fig. 


Fig.  50.  Flour  Blender  and  storage  LioHHjhH. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  633 


Fig.  51.  Flour  Elevator  and  Automatic  Weigher. 


Fig.  52.  Flour  Sifter,  Kneadeb,  and  Tempering  Tank. 


634 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


51),  and  sifters,  kneaders  and  tempering  tanks  (Fig.  52),  give  a very  com- 
plete idea  of  the  arrangement. 

727.  Blending  Plant  for  Medium  Bakeries— In  cases  where  the  cost  of 
the  above  plant  is  prohibitive,  a very  good  alternative  is  to  employ  the 
blender  only  and  discharge  direct  from  this  into  sacks  placed  on  platform 
scales  ; the  sacks  are  then  re-hoisted  to  the  upper  floor  and  shot  direct  into 
the  hopper  of  the  sifter,  and  thence  the  flour  pursues  its  usual  course  into 
the  kneader. 

As  an  alternative  a smaU  blender  may  be  used,  with  a capacity  equal 
to  that  of  the  kneader ; the  introduction  of  an  elevator  from  the  blender  to 
the  upper  floor,  arranged  to  discharge  direct  into  the  sifter,  then  obviates 
the  necessity  of  sacking  and  hoisting.  In  this  plant  it  is  obviously  neces- 
sary for  each  blend  to  exactly  correspond  to  the  size  of  batch  made  in  the 
kneader. 

728.  Blending  for  SmalllMachine  Bakeries. — An  excellent  plan,  which 
reduces  the  outlay  for  machinery  to  a minimum,  is  to  substitute  a hopper 


Fig.  53. — Special  Flour  Blending  Arrangement. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  635 


feeding  direct  into  the  elevator  for  the  blender  described  in  the  arrange- 
ment last  mentioned.  Pen  boards  placed  in  the  hopper  divide  the  same 
into  compartments  for  receiving  each  one  quality  of  flour.  When  the 
hopper  is  filled  the  pen  boards  are  withdrawn  and  the  elevator  started,  caus- 
ing approximately  equal  proportions  of  the  various  flours  forming  the  blend 
to  be  elevated  to  the  sifter.  If  the  kneader  is  allowed  to  run  for  a few 
moments  previous  to  introducing  the  liquor,  etc.,  a perfect  blend  is  obtained. 
Ample  time  is  allowed  for  obtaining  the  necessary  output  per  hour  of  dough 
if  the  kneader  is  of  a sufficient  size.  It  will  be  seen  that  this  arrangement 
has  the  further  considerable  advantage,  that  an  ideal  working  scheme  can 
be  obtained  with  only  two  floors.  The  ground  floor  will  be  equipped  with 
ovens,  divider,  etc.,  and  the  first  floor  with  kneader,  sifter,  and  elevator. 
The  first  floor  therefore  serves  as  doughing-room  as  w^eU  as  flour  store,  and 
enables  the  cost  of  building  to  be  kept  at  a very  reasonable  figure.  In 
view  of  the  considerable  cost  of  a fully  automatic  plant  and  the  relatively 
small  advantage  obtained  by  the  use  of  the  same,  in  comparison  with  the 
very  simple  arrangement  last  described,  the  authors  recommend  the  latter 
except  for  really  large  installations.  The  photographic  view  (Fig.  53) 
subjoined,  illustrates  this  arrangement  very  well. 

729.  Flour-Sifting  [Machinery. — Although  many  attempts  have  been 
made  to  introduce  a sifter  with  reciprocating  sieve  or  sieves,  the  rotary 
machine  undoubtedly  holds  the  field  and  answers  all  practical  requirements. 
The  fact  is  that  the  reciprocating  sieve,  although  theoretically  the  ideal 
arrangement,  is  in  practice  a nuisance  because  it  cannot  be  made  so  as  to 
be  either  noiseless  or  really  durable.  On  the  other  hand  the  rotary  sifter 
is  not  only  quite  noiseless  and  perfectly  trustworthy,  but  from  a commercial 
point  of  view  does  its  work  perfectly.  The  illustration  (Fig.  54)  shows  a 


Fig.  54. — Rotary  Flour  Sifter. 

machine  (similar  to  that  employed  in  the  blending  plant,  see  Fig.  52)  with 
a spiral  brush  roller  working  against  a semi-circular  sieve,  which  is  contained 
in  the  lower  box- like  extension  of  the  machine.  The  machine  is  fixed  to  the 
underside  of  the  ceiling  by  bolts  through  the  upper  framing,  and  the  half- 
hinges, which  appear  on  the  box-like  extension,  engage  with  the  other  halves, 
which  appear  just  above  the  brush  roller.  The  withdrawal  of  the  hinge 
pins  therefore  enables  the  lower  half  of  the  sifter  to  swing  open,  as  shown 
in  the  illustration,  giving  immediate  and  complete  access  to  the  brush  roller, 
sieve  and  interior  of  the  machine.  The  bearings  of  the  roller  are  adjustable, 
so  that  wear  of  the  bristles  can  be  compensated  for,  and  are  fitted  with 


■636 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Stauffer  solid  grease  lubricators.  The  spout  on  the  right-hand  side  serves 
for  discharging  the  tailings,  and  a canvas  bag  should  be  kept  tied  to  this,  to 
receive  the  same  ; it  should  be  emptied  daily  and  replaced  ready  for  the 
next  day’s  work. 

The  same  machine  is  supplied  fitted  with  a fiy- wheel  and  chain  drive  for 
use  in  bakeries  not  employing  mechanical  power  (see  paragraph  695  and 
following).  In  some  cases  this  sifter  is  also  fitted  on  the  kneading  machine 
itself,  in  which  case  its  construction  dispenses  entirely  with  wood,  except 
for  the  roller.  Reference  to  Fig.  62  will  show'  this  arrangement. 

730.  Tempering  and  Measuring  Water. — ^The  introduction  of  machinery 
in  general,  and  of  automatic  bread-making  plants  in  particular,  calls  for 
more  accurate  methods  in  the  bakery  than  were  formerly  considered  neces- 
sary. So  long  as  doughs  were  made  by  hand  the  operative  was  more  or 
less  a craftsman,  who  could  judge  by  touch  and  appearance  as  to  whether 
the  dough  was  of  the  correct  consistency  or  not.  The  craftsmen  are  getting 
fewer  every  year,  and  in  any  case  cannot  be  relied  upon  for  sufficiently 
accurate  judgment  to  suit  modern  requirements.  In  addition,  however 
sldlful  the  workman,  he  has  in  modern  machinery  no  opportunity  of  con- 
trolling the  consistency  of  his  dough,  other  than  by  accurately  weighing 
and  measuring  the  materials ; therefore  if  bread  is  to  be  satisfactory  and 
uniform,  if  automatic  dividers,  provers,  and  moulders,  are  to  yield  the  best 
results,  and  ovens  are  to  soak  the  bread  properly  in  a given  number  of 
minutes  at  a predetermined  temperature,  it  follows  that  the  doughs  must 
be  perfectly  uniform.  If  they  are  not  so,  the  results  are  either  not  of  the 
best,  or  the  smooth  working  of  the  bakery  must  be  disturbed  by  allowing 
batches  to  have  different  periods  for  proving  and  baking.  Clearly,  then, 

too  much  care  cannot  be  exer- 
cised in  the  making  of  dough. 
This  subject  will  subsequently 
receive  further  consideration 
(see  paragraphs  731-4)  ; it  is 
sufficient  for  the  present  pur- 
pose to  say  that  an  appliance 
is  necessary,  which  will  enable 
an  exact  quantity  of  water  at 
a pre-arranged  temperature  to 
be  accurately  and  readily  ob- 
tained. Needless  to  say,  the 
arrangements  should  also  be 
such  as  to  enable  this  result  to 
be  obtained  without  unneces- 
sary waste  of  water  in  adjust- 
ing the  temperature  desired. 
Theoretically,  much  might  be 
said  in  favour  of  w'eighing  the 
water,  as  the  most  accurate 
way  to  obtain  a given  quantity. 
In  practice,  appliances  for 
weighing  introduce  many  com- 
plications of  an  undesirable 
nature,  and  are  liable  to  de- 
rangement, leading  to  greater 
inaccuracies  than  simpler  ap- 
paratus involves.  The  best 
Measuring  Tank,  and  most  practical  arrangement 


Fig.  55. — Tempering  and 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  637 


is  the  tempering  or  attemperating  and  measuring  tank  here  illustrated 
(Fig.  55).  It  is  a tank  formed  of  steel  sheets,  tinned  inside,  and  supported 
on  the  wall  adjacent  to  the  kneader,  or  on  the  latter  itself.  Hot  and 
cold  water  are  conveyed  thereto  in  large  bore  pipes  to  prevent  delay.  The 
hot- water  pipe  is  internally  taken  to  the  bottom  of  the  tank,  and  the  cold- 
water  pipe  discharges  at  the  top.  Thus  an  excellent  mixing  is  obtained  by 
the  aid  of  natural  laws,  but,  as  an  extra,  a mixing  paddle  can  be  fixed  with 
a vertical  spindle — this  hastens  and  perfects  the  process  of  obtaining  a 
tank  full  of  water  at  a uniform  temperature,  as  ascertained  by  a thermo- 
meter which  is  immersed,  completely  and  readily  visible  through  the  plate- 
glass  front  of  the  tank. 

An  internal  overflow  pipe  is  fitted  and  wherever  possible  (in  all  new 
bakeries,  for  instance)  a sink  or  gully  should  be  provided  immediately  below 
the  position  which  a tank  is  to  occupy.  This  gully  will  not  only  take  such 
overflow  from  the  tank  as  occurs,  but  is  useful  for  washing  down  the  floor, 
the  kneader,  and  for  emptying  pails,  etc.  The  specially  useful  feature 
about  the  tank  illustrated  is  the  sliding  scale  (Williams’  patent)  seen  through 
the  glass  front,  and  readily  raised  and  lowered  by  means  of  the  hand- wheel 
on  the  left.  This  scale  is  plainly  marked  in  gallons,  as  seen  in  the  illustra- 
tion, and  facilitates  the  drawing  off  of  the  exact  quantity  of  water  required. 
In  any  ordinary  tank  it  is  practically  impossible  to  obtain  a pre-arranged 
level  of  the  water,  while  tempering  the  same  to  say  96°  F.,  without  per- 
mitting an  overflow,  and  thereby  incurring  a waste  of  water.  The  tank 
illustrated,  however,  is  larger  than  the  maximum  capacity  registered  on  the 
scale,  and  therefore  allows  sufficient  margin  for  obtaining  the  correct  degree 
of  heat  without  overflow  or  waste.  As  soon  as  the  water  is  at  the  right 
temperature  and  thoroughly  mixed,  which  is  indicated  by  the  thermometer 
reading  remaining  stationary,  the  scale  is  moved  to  the  position  in  which  the 
zero  mark  exactly  corresponds  to  the  level  of  the  water.  The  universally- 
jointed  pipe,  shown  in  an  upright  position  in  the  illustration,  is  next  placed 
in  position  to  discharge  the  water  into  the  kneader,  and  then  the  large  draw- 
off shown  is  opened.  As  the  water  runs  out  of  the  tank  and  the  level  sinks, 
it  is  clear  that  the  cock  merely  requires  to  be  closed  sharply  when  the  water 
level  has  sunk  to  the  mark  indicating  the  desired  number  of  gallons,  to 
ensure  that  the  right  quantity  of  water,  at  the  correct  temperature,  has  been 
delivered  into  the  kneader.  These  tanks  are  made  in  various  sizes  to  corre- 
spond to  the  capacity  of  the  kneader. 

Attention  is  here  drawn  to  the  fact  that  certain  waters  (notably  some 
moor  waters)  corrode  iron  and  steel,  even  when  protected  by  galvanising. 
To  meet  such  cases  these  tanks  are  also  made  of  copper  and  gun-metal 
throughout,  coated  with  tin  internally.  These  tanks  are  so  cleanly  and 
useful  in  saving  time  and  ensuring  better  and  more  uniform  results,  that 
their  employment,  even  in  hand-w'orked  bakeries,  must  be  recommended. 
It  is  quite  a common  error  to  suppose  that  they  are  useful  only  in  connec- 
tion with  machinery. 

731.  Dough  Mixers  and  Kneading  Machines. — Of  modem  dough-making 
machines  there  are  three  principal  types  which  require  to  be  considered 
in  detail  and  which  practically  cover  the  entire  field.  The  first  group  em- 
braces machines  constructed  upon  the  principle  of  a revolving  drum,  the 
second  employs  a stationary  trough  with  blades  revolving  around  their  ow  n 
axes,  and  the  third,  arms  moving  in  fixed  planes  in  a revolving  pan. 

732.  Rotary  Mixers. — The  idea  underlying  a rotary  mixer  is  extremely 
simple.  A drum,  of  a volume  considerably  greater  than  the  size  of  the 
batch  to  be  made,  is  revolved  around  a horizontal  axle,  wliich  runs  through 
the  drum.  Parallel  to  the  axle  are  placed  a number  of  metal  rods  which 


638 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

pass  from  one  side  of  tlie  drum  to  the  other.  A square  opening  is  cut  in  the 
cylindrical  sheet,  which  forms  the  drum  and  joins  up  the  two  circular  cast- 
ings, which  constitute  the  sides  ; the  opening  is  closed  by  a removable 
door.  In  revolving,  the  flour,  water,  etc.,  are  tumbled  about  and  over  the 
bars  until  the  dough  is  made.  The  door  is  then  removed  and  the  drum  is 
revolved,  until  the  opening  is  at  the  lowest  point  and  the  dough  allowed 
to  discharge  itself.  It  will  be  seen  that  the  machine  is  of  a simple  nature, 
does  not  require  much  power,  and  can  be  made  very  cheaply.  But  there 
its  advantages  end,  and  it  is  necessary  to  say  that  while  its  simplicity  and 
inexpensiveness  are  attractive,  the  dough  it  makes  is  not  kneaded  at  all  in 
the  proper  sense,  and  lacks  texture,  volume  and  colour,  while  being  wet, 
sticky  and  inclined  to  be  lumpy  when  discharged.  It  follows  that  while 
the  machine  may  answer  for  slack  doughs,  it  cannot  be  recommended  for 
those  of  a stiffer  nature  or  for  high-class  work,  or  for  obtaining  a maximum 
yield.  An  impartial  trial,  with  precisely  similar  flour  and  other  types  of 
machine,  will  prove  this. 

The  rotary  kneader  was  first  put  upon  the  market  under  the  “ Adair 
patents. 


733.  Kneading  Machines  with  Revolving  Blades. — ^The  construction  of 
these  machines  is  based  upon  the  employment  of  a cylindrical  trough  which 
encases  a revolving  blade,  with  the  axes  of  the  two  coinciding.  The  sheet 
which  forms  the  trough  does  not  ^complete  the  circumference,  but  merges 
above  into  a rectangular  hopper,  open  at  the  top.  In  most  machines  two 
cylinders  are  employed  with  parallel  axes,  apart  from  one  another  by  a 
distance  rather  less  than  the  diameter  of  each  cylinder.  In  exceptional 
cases  three  blades  are  employed,  but  the  arrangement  introduces  undesirable 
complications  and  possesses  no  advantages  per  se.  In  the  earliest  machines, 
and]many  others,  the  blades  were  of  a haphazard  and  of  a more  or  less  fanciful 
design,  and  although  they  all  made  and  make  dough,  yet  the  problem  of 
the  shape  of  the  blades  does  not  seem  to  have  been  worked  out  on  scientific 
lines. 

The  Two  - hladed 
Kneader  may  be  safely 
considered  the  most  typ- 
ical and  widely  - used 
dough-making  machine 
employed  in  bakeries,  and 
as  such  requires  to  be 
dealt  with  more  fully. 
The  best  example  of  these 
is  that  known  as  the 
“Universal’'  (Pfleiderer’s 
patent).  In  its  original 
form,  this  was  the  first 
machine  to  be  efficiently 
manufactured  and  intro- 
duced to  the  bakery 
trade.  It  is  also  generally 
acknowledged  to  be  the 
most  successful,excepting 
only  for  certain  special 
types  of  dough.  Of  this 
machine  an  illustration  is 

Fio.  5(i.  “I’NIVKRSAL”  Kneaihng  Machink,  given  in  Fig.  56,  showing 
PrLEi])p:RER’s  Patient.  the  machine  nearly  tilted 


[ THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  639 

over  for  discharging  the  dough.  The  main  secret  of  the  success  of  this 
machine  lies  in  the  form  of  the  blades,  which  are  constructed  on  highly 
scientific  lines,  and  ensure  that  every  particle  of  the  contents  of  the  trough 
is  brought  within  their  action  with  absolute  thoroughness.  A small  model 
machine  on  the  same  lines  is  sold  by  the  makers,  which  constitutes  a most 
useful  addition  to  laboratories  generally,  where  it  is  invaluable  in  many 
ways,  apart  from  its  utility  as  adough-maker  for  small  test  batches.  This 
little  machine  demonstrates  the  perfect  mixing  action  very  effectively,  if  it 
be  charged  with  dry  flour,  and  a pinch  of  red  lead.  With  a stated  num- 
ber of  revolutions  it  will  so  thoroughly  incorporate  the  two  ingredients, 
which  by  other  means  are  not  at  all  easy  to  mix  intimately  on  account  of 
the  great  difference  in  specific  gravity,  that  a small  part  of  the  mixture, 
jDlaced  on  a sheet  of  paper,  will  successfully  stand  the  severe  test  of  being 
“ smeared  with  a palette  knife  to  prove  the  uniformity  of  mixing  obtained. 

Returning  to  the  dough  kneader,  the  next  point  to  be  mentioned  lies 
in  the  arrangements  for  preventing  the  escape  of  liquid  from  the  trough  and 
for  making  the  entering  of  grease  or  dirt  impossible.  The  problem  is  not 
an  easy  one,  but  has  been  solved  very  simply  and  effectively.  There  are 
only  six  bearings  in  this  machine,  apart  from  the  tw^o  loose  pulleys  in  connec- 
tion with  the  driving  gear,  and  all  are  fitted  with  Stauffer  solid  grease  lubri- 
cators. The  drive  is  arranged  to  be  reversible  by  means  of  friction  clutches 
formed  between  each  of  the  two  pulleys  and  the  central  driving  disc,  which 
is  enlarged  in  diameter  and  fitted  with  a handy  rim  to  enable  the  machine 
to  be  pulled  round  by  hand  when  being  cleaned.  The  control  is  from  the 
hand- wheel  overhanging  the  pulleys,  which  are  driven  in  opposite  directions 


Fig.  58.  “Universal”  Kneading  Machine,  Single  Blade,  Fitted  with 

Electric  Motor. 

by  belts  from  the  line  shaft,  one  “ open  and  one  “ crossed,^’  thus  enabling 
the  blades  to  be  driven  in  either  direction.  The  weight  of  the  trough  is 
balanced  by  counterweights,  and  the  raising  or  lowering  may  be  by  hand  or 
power  as  desired.  The  interior  of  the  trough  as  well  as  the  surface  of  the 


640 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


blades  are  ground  and  polished,  and  the  dough  leaves  these  surfaces  per- 
fectly clean,  on  being  turned  out,  except  with  very  slack  doughs. 

The  machine  is  fitted,  if  desired,  for  driving  direct  by  electric  motor,, 
which  is  then  supplied  with  a reversing  controller  to  enable  the  machine 
to  be  reversed.  Fig.  58  shows  a single-blade  “ Universal fitted  with  a 
motor  direct.  This  machine  is  made  with  pulley  drive  also,  or  the  machine 
shown  in  Fig.  56  can  also  be  fitted,  self-contained,  with  electric  motor  as. 
here  shown  (Fig.  59).  To  prevent  the  raising  of  flour  dust,  which  would 


Fig.  59. — “Universal”  Kneading  Machine  fitted  with  Electric  Motor. 

result  from  working  the  machines  without  a lid,  these  kneaders  are  either 
fitted  as  shown  in  Fig.  52  and  connected  direct  to  the  sifter,  or  they  can  be 
supplied  with  a “ safety  ''  lid,  which  is  so  interlocked  with  the  driving  gear 
that  it  is  impossible  to  raise  the  lid  while  the  machine  is  in  operation.  In 
certain  countries  these  “ safety  ''  lids  are  made  compulsory,  as  a preven- 
tion for  accidents  to  operatives. 

With  regard  to  the  dough  made  by  these  machines,  it  may  be  said  that 
it  is  of  a very  high  quality,  perfectly  uniform,  and,  if  not  overworked,  far 
better  than  can  be  obtained  by  hand  under  commercial  conditions.  Hy- 
gienically  also  the  machine  is  perfect,  as  it  lends  itself  readily  to  being  cleaned 
with  great  thoroughness,  and  no  contamination  of  the  dough  can  occur. 

As  to  durability,  a subject  on  which  it  is  only  possible  to  speak  authorita- 
tively after  many  years,  there  are  machines  still  in  hardest  everyday  use 
which  were  installed  from  twenty-six  to  thirty  years  ago,  and  no  renewals 
of  a serious  nature,  or  repairs,  have  been  necessary  in  this  long  time. 

734.  Kneaders  with  Rotating  Pans. — These  are  a comparatively  modern 
product ; many  are  of  too  light  a construction  to  be  serviceable,  and  have 
the  .serious  defect  that  working  parts  requiring  lubrication  are  to  be  found 
over  the  dough,  on  which  grounds  their  use  cannot  be  recommended.  These 
machines  employ  a different  principle  altogether  to  those  already  described, 
and  rely  upon  the  stickiness  and  plastic  and  tenacious  qualities  of  dough 
for  tlieir  action,  which  may  perhaps  be  described  as  more  akin  to  sugar 
“ pulling  than  anything  else. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  641 


Fig.  61  shows  a diagram  of  the  ‘‘ Viennara kneader  (“  Poin ton's '' 
patent).  The  arm  is  fitted  with  double  horns,  as  shown  in  Figs.  62  and 


Fig.  61. 


“Viennara”  Kneading  Machine.  Sectional  Diagram. 


Ip 

ii 

j-rm— j— TT^a 

63,  and  describes  a curve,  which  compels  the  horns  to  move  in  a path 
shown  in  dotted  lines  (Fig.  61).  The  gearing  is  so  arranged  that  the  speed 
throughout  this  curve  is  not  constant  ; it  is  slowest  when  the  horns  are 
descending  and  increases  rapidly  as  the  horns  sweep  the  radius  between 
the  bottom  and  side  of  the  pan,  being  at  its  greatest  during  the  upward 
movement.  The  pan  slowly  revolves  (about  4J  revolutions  per  minute), 
and  being  filled  with  flour  to  the  line  indicated,  brings  fresh  material 
under  the  influence  of  the  arm  at  each  stroke  (26  per  minute).  The  effect 
is  to  subject  the  dough,  when  incorporated,  to  a combined  aerating  stretch- 
ing and  folding  action,  most  admirably  adapted  to  develop  it  under  ideal 
conditions  and  to  an  extent  quite  impossible  by  manual  labour.  The 
operation  of  the  arm  is  of  the  gentlest  kind,  and  owing  to  the  perfectly 
combined  aerating  folding  and  stretching  which  the  dough  receives,  it  is 
of  a remarkably  fine  texture,  toughness,  colour,  and  volume.  Many  claims 
have  been  made  for  devices  for  increasing  the  yield,  a point  on  which  bakers 
have  become  rightly  sceptical  ; but  certainly  the  “ Viennara  " has  remark- 
able properties  in  the  direction  of  causing  the  flour  to  absorb  its  proper 
proportion  of  water  without  loss  of  stiffness  or  elasticity.  Consequently, 
the  dough  produced  shows  a decided  improvement  in  colour. 

Fig.  62  shows  the  complete  machine  with  sifter  and  tempering  tank 
self-contained.  As  will  be  seen,  a door  is  fitted  in  the  pan,  which  can  only 
be  stopped  in  the  correct  position  for  discharging.  This  door  is  interlocked 

T T 


642 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


with  the  driving  control  in  such  a manner  as  to  make  any  mistake  impossible. 
The  dough  truck  runs  under  the  pan,  and  the  dough  is  discharged  automatic- 
ally by  the  arm  alone  being  worked,  while  the  pan  remains  stationary. 
The  domed  lid  is  a fixture,  but  the  front  portion  is  hinged  and  can  be  raised 
so  that  the  dough  can  be  inspected.  The  pan,  having  no  blades,  bearings  or 
axles,  has  a perfectly  smooth  interior  ; it  is  therefore  hygienically  perfect  and 
practically  keeps  itself  clean.  The  door  gives  no  trouble  from  leakage  or 
any  other  cause.  The  power  required  for  the  machine  is  very  little  and 
not  more  than  one-half  that  absorbed  by  the  “ Universal.’" 


Fig.  62.  “Viennara”  Kneading  Machine. 

Another  form  of  this  machine  is  that  illustrated  in  Fig.  63,  and  known 
as  the  “ Kempter  ” patent.  The  general  principle  is  exactly  the  same  as  that 
described  above,  the  essential  difference  being  that  whereas  the  machine  first 
described  has  a pan  which  is  an  integral  part  of  the  machine,  the  Kempter 
modification  is  fitted  with  a removable  pan.  The  idea  is  to  use  the  pans  as 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  643 


dough  trucks,  and  as  all  are  interchangeable,  one  machine  serves  for  them 
all.  One  advantage  is  that  for  “ cutting  back the  pans  are  simply  brought 
back  to  the  machine,  which  does  the  work  admirably.  This  type  is  used 
more  especially  on  the  Continent,  whereas  the  self-discharging  machine  has 
found  preference  in  this  country.  The  dough  made  is  of  equal  excellence  in 
either. 


Fig.  63.  Kneading  Machine,  Kempter  Patent. 

In  conclusion  two  important  subsidiary  advantages  in  the  “ Viennara 
machine  must  be  referred  to.  The  first  is  that  owing  to  the  extremely  gentle 
action  of  the  machine,  the  arm  of  wdiich  can  in  no  wise  damage  the  dough 
more  than  a man’s  arm  does  in  kneading,  it  is  practically  impossible  to 
overwork  a batch.  Men  will  leave  their  jobs  and  cannot  be  relied  upon 
to  do  exactly  as  they  are  told ; it  is  therefore  distinctly  an  advantage  in  this 
machine  that  by  being  left  longer  at  work  than  is  necessary  it  cannot  damage 


644 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


— but  will,  in  fact,  rather  improve,  the  dough.  The  second  point  needing  a 
special  reference  is  that,  unlike  other  machines,  this  is  a very  safe  appliance, 
in  using  which  it  is  scarcely  possible  for  a man  to  receive  injury.  The  arm 
on  its  upward  stroke  will  push  out  a man’s  hand,  and  can  never  pull  him  in 
if  he  attempts  to  feel  the  dough,  as  is  only  too  frequently  done. 

735.  Sponge-making  Machines. — Before  leaving  the  subject  of  kneaders 
it  is  necessary  to  describe  the  application  of  such  machines  to  the  making 
of  “ sponges.”  Although  the  tendency  in  machine  bakeries  has  been  for 
many  years  to  adopt  the  “ straight  dough  ” system,  dispensing  with  sponges 
and  kneading  the  flour  with  yeast  and  salt  into  a dough  direct,  yet  the  older 
process  holds  its  own  in  many  countries,  and  also  in  portions  of  the  United 
Kingdom,  notably  in  Scotland  and  Ireland.  A very  convenient  combina- 
tion is  provided  by  the  “ Universal  ” machine  already  described,  when  such 
a machine  is  fitted  with  two  speeds  to  be  used  at  will.  It  will  be  clear  that 
this  enables  a high  speed  action  to  be  used  for  making  light  sponges,  which 
when  made  are  turned  out  into  dough  trucks  and  left  to  prove.  These 
sponges  when  ready  are  then  utilised  for  making  the  dough,  for  which  the 
second  or  normal  slow  speed  of  the  kneader  is  used. 

736.  Sponge-Stirrer. — Another  form  of  machine  frequently  used  is  the 
sponge-stirrer,  of  which  an  illustration  is  given  in  Fig.  64,  A cast-iron 


Fig.  64.  Sponge- Stirring  Machines. 


standard  carries  the  driving  gear  as  well  as  the  upright  spindle  fitted  with 
suitable  blades,  which  being  balanced  and  arranged  to  be  conveniently 
raised,  permits  the  tub,  fitted  with  castors,  to  be  readily  placed  in  position. 
The  sliding  casting,  shown  in  the  illustration  above  the  stirrer  proper,  rises 
and  fallsVith  the  latter,  and  acts  as  a self-centring  guide  to  the  tub,  which 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  645 


is  automatically  locked  in  position  as  soon  as  the  spindle  lias  been  lowered. 
A sifter  is  fixed  above  the  stirrer  (as  shown)  and,  by  means  of  a canvas  shoot 
enables  the  flour  to  pass  direct  into  the  tub.  The  illustration  also  shows  the 
kneader,  with  sifter  and  tempering  tank  and  the  tub  lift,  with  a tub  lifted 
ready  for  discharging  its  contents  into  the  kneader,  thus  giving  a very  clear 
idea  of  the  whole  installation  for  suitably  dealing  with  doughs  in  such 
bakeries  as  employ  the  “ sponging  ''  process. 

737.  Dough  Trucks  and  Dough  Proving. — As  has  been  already  pointed 
out  in  paragraphs  683  and  696  dough  trucks  should  always  be  movable. 
They  should  therefore  be  of  a “ handy  ” size,  never  exceeding  a capacity  for 
two  sacks.  They  should  be  fitted  with  castors,  or  if  preferred  with  one 
castor  at  each  end  and  an  axle  in  the  centre,  with  two  loose  wheels,  designed 
to  take  the  whole  load  and  keep  the  castors  just  off  the  floor.  In  this 
country  the  dough  trucks  are  almost  universally  of  wood.  It  is  difficult 
to  account  for  the  prejudice,  which  tenaciously  clings  to  British  practice, 
against  the  employment  of  metal  in  this  connection,  despite  the  fact  that 


Fig.  65.  Steel  Dough  Truck. 

in  all  other  matters  pertaining  to  bakery  equipment,  especially  as  regards 
large  establishments,  this  country  is  undoubtedly  ahead  of  all  others.  The 
common  idea  is  that  the  metal  trough  must  chill  the  dough,  but  as  the  dough 
will  be  chilled  in  any  case  if  the  bakehouse  is  cold — and  the  truck  cannot  be 
cold  if  the  bakery  is  not — the  conclusion  is  not  very  logical.  Further,  the 
specific  heat  of  iron  is  low,  and  the  trough  cannot  under  any  ordinary  circum- 
stances, affect  the  temperature  of  the  dough  to  a material  extent.  As  a 
matter  of  fact  the  wooden  dough  truck  has  practically  disappeared  from  all 
modern  plants  on  the  Continent,  and  as  the  Continental  baker  appreciates 
the  importance  of  not  chilling  his  dough,  at  least  as  much  as  his  British  con- 
frere, the  statement  that  there  is  no  objection  to  the  use  of  iron  or  steel  in 
dough  trucks,  any  more  than  in  kneaders,  dividers  or  moulders,  must  be 
held  to  be  proved  correct.  Of  course  every  baker  will  please  his  own  tastes 
in  such  a matter  as  this,  but  it  is  at  least  worth  while  to  point  out  that  the 


646 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


not  inconsiderable  wear  and  tear,  with  consequent  renewals,  occasioned  by 
the  use  of  wooden  trucks,  may  be  eliminated  by  the  employment  of  the 
very  much  more  hygienic  and  durable  steel  truck,  with  bright  ground  interior 
surface,  similar  to  that  of  a kneader.  A good  plan  is  to  use  steel  troughs 
tinned  inside,  as  being  the  most  suitable  surface.  An  illustration  (Fig.  65) 
is  given  of  such  a trough  showing  its  general  construction. 

The  dimensions  of  trucks  should  be  suitable  for  the  machines  with  which 
they  are  to  be  used,  a point  sometimes  overlooked,  and  both  width  and 
depth  should  not  be  too  great,  as  unduly  heavy  work  is  otherwise  thrown 
upon  the  operative.  Inside  dimensions  of  about  2 ft.  in  width  and  1 ft.  6 in. 
in  depth  should  not  be  exceeded. 

738.  Proving-Rooms. — When  bread  was  almost  universally  made  by 
the  long  sponge  system,  the  employment  of  separate  rooms,  kept  at  an  even 
temperature,  for  the  storage  of  sponges  during  fermentation,  was  always 
regarded  as  a great  advantage.  With  the  advent  of  automatic  plants,  the 
subject  requires  consideration  in  a new  light.  The  fact  is  that  separate 
proving-rooms  may  be  responsible  for  bad  results,  where  automatic  plants 
are  in  use,  unless  steps  are  taken  to  ensure  that  the  temperature  of  such 
rooms  does  not  vary  from  that  of  the  machines.  Now  it  cannot  be  suffi- 
ciently insisted  upon  that  dough  must  not  be  subjected  to  changes  of  tem- 
perature throughout  its  different  phases  ; and,  when  ready  for  dividing 
(scaling),  should  not  be  brought  into  rooms,  or  fed  into  machines,  which 
are  at  a different  temperature  than  the  dough  itself.  It  follows  that  the 
arrangement  of  the  bakery  should  be  such  as  to  make  this  automatic  if 
possible,  because  the  more  it  is  left  to  the  men  to  observe  such  matters  and 
regulate  temperatures  the  more  trouble  will  ensue.  The  machine-room, 
and  therefore  the  machines  contained  therein,  should  be  kept  at  a uniform 
temperature,  equal  to  that  of  the  doughing  and  proving-room,  and  all  should 
of  course  be  arranged  so  that  they  are  free  from  draughts.  If  this  cardinal 
principle  is  adopted  and  never  lost  sight  of,  and  if  new  bakeries  are  designed 
with  this  clearly  in  view,  much  trouble  and  constant  watching  will  be  saved. 
Assuming  a bakery  perfect  in  this  respect  and  equipped  with  automatic 
plant  of  the  best  type,  a wonderfully  high  and  uniform  standard  of  bread 
will  be  obtained,  if  reasonable  care  be  used  in  preparing  the  doughs  at  the 
proper  and  uniform  temperature. 

739.  Dough  Dividers. — ^These  were  first  placed  upon  the  market  in  a 
commercially  practicable  form  about  the  year  1896.  The  introduction 
of  loaf  dough-dividing  machinery  marks  a distinct  and  very  far-reaching 
development  in  the  mechanical  equipment  of  bakeries.  All  subsequent 
stages  of  dough-making  and  machine- working,  however  difficult  of  solution 
in  themselves,  are  dependent  upon,  and  secondary  to,  the  problem  of  satis- 
factorily weighing  off  pieces  of  dough  of  given  weights  from  the  bulk.  In 
the  course  of  the  last  fifteen  years  three  main  principles  have  been  employed 
in  the  construction  of  dividers.  Cylinders  or  boxes  with  close-fitting  rams, 
the  latter  adjustable  to  give  variable  volumes  provided  to  receive  the  dough 
necessary  to  form  one  piece  or  loaf,  are  common  to  all  three  types  referred 
to.  It  is  in  the  means  employed  for  charging  these  cylinders  or  boxes  with 
dough  that  the  three  types  principally  and  materially  differ.  A worm, 
acting  as  a conveyor  at  the  base  of  a dough  hopper — fluted  or  roughened 
rollers  running  in  opposite  directions,  charging  a chamber,  communicating 
with  the  cylinders — and  a weighted  ram  acting  upon  the  dough  confined  in 
a closed  chamber,  are  the  three  different  means  referred  to.  All  three  prin- 
ciples lend  themselves  to  the  construction  of  machines  capable  of  cutting 
dough  pieces,  with  sufficient  accuracy  for  all  commercial  purposes  ; in 
fact  to  the  production  of  loaves  of  much  more  uniform  and  accurate  weight 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  647 


than  is  commercially  obtainable  by  hand.  The  effect  of  such  machines 
upon  the  dough,  and  upon  the  process  of  fermentation,  is,  however,  the  chief 
consideration  and  requires  to  be  most  carefully  taken  into  account.  Dough 
is  not  a material  which  may  be  ill-treated  with  impunity  ; it  is,  or  should 
be,  a living  mass  which  may  suffer  irretrievable  damage  if  handled  with  a 
trifling  excess  over  the  permissible  severity.  This  aspect  of  the  matter  is 
often  dismissed  with  unpardonable  levity,  on  the  plea  that  “ a little  more 
yeast  will  soon  put  that  right,'’  or  that  “ it  can  be  left  a little  longer  to 
recover  ” ! There  is  no  such  thing  as  artificially  counteracting  actual 
damage,  either  by  an  extra  allowance  of  yeast  or  reviving  fermentation. 


Fig.  66.  Two-Cylinder  Dough  Dividing  Machine. 

which  has  unduly  suffered,  by  allowing  extra  proof.  These  are  palhatives 
and  may  mend,  to  some  extent,  the  worst  effects  of  undue  severity,  but 
cannot  and  do  not  allow  a healthy  growth  or  perfect  development  to  take 
place. 


648 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


In  two  of  the  systems  quoted  above  there  is  the  inherent  drawback  that 
the  force  put  into  the  dough  (or  force  with  which  the  dough  is  handled) 
cannot  be  definitely  hmited  in  such  a manner  as  to  preclude  damage.  The 
action  is  not  positive,  and  therefore  always  employs  a surplus  of  feeding 
capacity  to  ensure  the  filling  of  the  cylinders,  which  by  their  regulated 
volume  give  the  weights  required.  On  the  other  hand,  the  third  type 
absolutely  limits  the  force  employed  and  is  positive  in  its  action.  The 
pressure  to  which  the  dough  is  subjected  by  the  ram  which  causes  it  to  enter 
the  division  boxes  can  never  exceed  a safe  and  predetermined  maximum, 
since  it  is  due  to  a weight  which  in  working  remains  constant  but  can  be 
varied  to  suit  the  requirements  of  the  class  of  dough  used,  and  never  forces 
forw^ard  a greater  quantity  than  the  measuring  cylinders  absorb.  It  follows 
that  the  maximum  advantage,  when  using  a machine  of  this  type,  will  ^be 
obtained  by  employing  a minimum  weight  to  give  sufficiently  accurate  loaves. 


Fig.  67.  Larger  Dough  Dividing  Machine. 

Correct  Weights. — It  will  be  opportune,  at  this  point,  to  call  attention 
to  the  relative  value  of  weighings,  more  or  less  accurate.  It  is  a fact  that 
it  is  possible  to  insist  upon  too  much  accuracy,  especially  in  view  of  the 
very  natural  tendency  to  scale  as  closely  as  possible  and  obtain  the  maximum 
saving  in  dough.  Everything,  however,  may  be  carried  to  excess,  and  a 
baker  may  easily  lose  more  in  quality,  and  therefore  in  texture,  bulk,  and 
general  attractiveness  of  loaf,  than  he  gains  in  dough  by  very  close  weighing. 

Extreme  accuracy  is  inseparable  from  punishment,  and  in  turn  punish- 
ment is  inseparable  from  loss  in  legitimate  selling  qualities  of  the  loaf.  So 
long  as  a divider  gives  more  accurate  weighings  than  can  be  commercially 
obtained  by  hand-scaling,  a business  will  be  more  benefited  by  good  quality. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  649 


due  to  avoidance  of  punishment,  than  from  an  insistence  on  the  maximum 
economy  in  dough. 

The  sound  plan  therefore  is  to  choose  the  divider  which  is  limited  in  its 
punishing  effects,  and  then  adjust  the  machine  to  work  with  the  minimum 
weight  required  to  ensure  sufficient  accuracy  for  commercial  purposes. 

The  illustration  (Fig.  66)  shows  a two -cylinder  deadweight  divider, 
suitable  for  small  bakeries,  which  has  a maximum  output  of  1,400  pieces  per 
hour.  For  guidance  as  to  the  proper  proportioning  of  output,  remunerative- 
ness, etc.,  see  paragraphs  697  and  699.  A larger  machine  with  outputs  up 
to  2,400  pieces  per  hour  is  sliovTi  in  Fig.  67  and  referred  to  in  paragraph  746 
under  Automatic  Plants.  Both  machines  are  made  right  and  left  handed 
for  belt,  or  direct  electrical,  driving. 

740.  Moulding  Machines. — When  the  newly-kneaded  dough  is  turned 
out  into  the  dough  truck,  it  requires  to  be  left  undisturbed  at  a proper 
temperature  in  order  to  ferment,  and  as  a result  of  the  generation  of  gases 
the  original  volume  of  the  dough  is  much  increased.  It  is  here  that  the 
value  of  a good  kneading  machine  becomes  apparent,  because  if  thorough 
aeration  has  been  combined  with  a maximum  of  stretching  and  folding, 
the  result  will  be  a dough  which  excels  in  bulk,  toughness,  fineness  of 
texture,  and  good  colour. 

To  obtain  the  best  results  it  is  essential  for  the  development  of  fermenta- 
tion to  be  as  uniform  throughout  the  whole  mass  of  dough  as  possible,  and 
for  the  gluten  to  be  toughened,  so  as  to  resist  the  gases  uniformly,  causing 
an  evenness  and  silkiness  of  texture  not  otherwise  obtainable.  Judicious 
and  efficient  “cutting  back’"  assists  uniformity  for  the  same  reason,^ and 
when  finally  ready  for  scaling  or  dividing  a good  dough  must  be  uniform  all 
over.  It  will  be  apparent  that  in  cutting  the  dough,  when  scaling  or  dividing 
into  pieces  of  a size  suitable  for  loaves,  these  conditions  are  disturbed,  inas- 
much as  fermentation  will,  from  that  moment,  take  place  under  totally 
different  circumstances.  Apart  from  this,  the  cutting  produces  wounds, 
which  form  portions  of  the  surfaces  of  the  piece  intended  to  become  a 
loaf.  It  is  therefore  necessary  to  re-work  each  piece,  with  the  two-fold 
object  of  closing  the  wound  by  forming  a complete  skin  all  over  the  dough- 
piece,  and  of  working  the  interior,  so  as  to  cause  fermentation  to  continue 
under  conditions  which  will  be  uniform  and  suitable  throughout  the  newly 
detached  piece  of  dough  intended  to  become  a loaf.  This  process  is  called 
moulding. 

Hand  Moulding  has  hitherto  been  performed  in  such  a manner  that  the 
piece  was  rolled  on  a table,  against  the  palm  of  the  hand,  as  a more  or  less 
pear-shaped  mass,  causing  the  central  portions  to  be  worked  outwards,  and 
vice  versa.  It  was  essential  to  preserve  the  skin,  which  was  formed  in  this 
process,  from  rupture  while  tightening  up  the  interior,  which  of  course  had  the 
effect  of  stretching  the  skin  simultaneously.  The  tail  of  the  loaf,  similar  to  the 
gradually  contracting  and  tube-like  lower  extremity  of  an  inflated  balloon, 
sealed  the  skin  and  was  worked  into  the  loaf -piece  at  the  conclusion  of  the 
operation,  when  each  piece  should  become  as  nearly  spherical  as  possible. 
The  loaf  was  placed  tail  downwards  on  boards  or  in  drawers  to  undergo  a 
further  period  of  proving,  protected  from  chills.  It  is  needless  to  say  that 
good  moulding  could  only  be  performed  by  a craftsman,  and  that  the  quality 
of  workmanship  varied  to  a very  great  extent.  The  labour  was  monoton- 
ous, and  also  arduous,  if  carried  on  indefinitely,  while  effective  supervision 
and  a maximum  speed  were  not  easily  obtained.  From  a hygienic  point 
of  view  also  it  was  objectionable. 

Machine  Moulding. — To  find  a satisfactory  solution  of  the  difficult 
problem  of  moulding  dough  by  mechanical  methods  proved  by  no  means 


650 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


easy.  The  experience  of  several  years’  working,  however,  conclusively  shows 
that  the  task  has  been  accomplished.  The  principle  adopted  is  to  impart 
to  the  dough-piece  a continuous,  rotatory,  and  screw-like  motion  (“  Poin- 
ton’s  ” patent)  by  feeding  it  into  a spirally  shaped  trough  arranged  upon 
a revolving  cone-shaped  table  (see  Fig.  68). 


Fig.  68.  Dough  Moulding  Machine. 

The  spiral  trough  is  stationary,  with  its  finished  (ground)  surface  on 
its  under  or  working  side  ; it  is  supported  by  arm-rods,  and  brackets  from 
above  by  means  of  the  column,  around  which  the  table  revolves.  The 
table  is  grooved  to  afford  grip  to  the  dough.  It  is  obvious  that  if  the  trough 
were  merely  arranged  to  encircle  the  table  horizontally  a pure  rolling 
motion  would  be  imparted  to  the  loaf.  A skin  might  thus  be  formed, 
although  it  would  be  wrinkled  and  not  in  any  way  stretched,  but  the  dough 
itself  would  only  be  squeezed  about  and  in  no  sense  truly  moulded.  The 
illustration,  however,  shows  that  the  trough,  after  a short  horizontal  length, 
to  enable  the  dough-piece  to  start  rolling,  gradually  ascends  the  cone  table, 
causing  the  loaf  to  be  forced  against  it.  The  result  is  that  the  dough-mass 
does,  in  fact,  undergo  a screw-like  motion,  systematically  displacing  and 
methodically  rearranging  the  whole  of  its  bulk,  while  stretching  the  skin 
continuously  from  the  head  of  the  loaf  tailwards  in  every  direction.  At  its 
upper  or  delivery  end  the  trough  again  “ eases  off  ” its  rate  of  mounting  the 
conical  table,  and  thus  ceases  to  form  the  tail,  which  is  “ tucked  in,”  and 
enables  the  finished  loaf  to  roll  off  the  table  in  as  nearly  a spherical  con- 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  651 


dition  as  is  necessary  for  all  practical  purposes.  The  proper  accomplish- 
ment of  this  process  is  essential  to  the  obtainment  of  “ build”  ensuring 
not  only  a tough  and  highly  stretched  skin  and  a thoroughly  worked  interior 
to  the  loaf,  but  also  that  orderly  and  regular  rearrangement  of  the  cellular 
structure  which,  by  means  of  proper  subsequent  proving,  compels  the 
growth  of  that  much  desired  and  beautiful  texture  of  the  perfectly  developed 
loaf  of  bread. 

From  the  description  given,  it  will  be  seen  that  the  “ pitch  of  the  trough, 
which  governs  the  rate  at  which  it  ascends  the  table,  will  regulate  the  degree 
of  “ working  imparted  to  the  dough.  If  too  much  “ working  ’’  is  put 
into  the  dough,  the  skin  of  the  loaf  will  be  overstretched  and  yield  under  the 
strain  ; and  if  too  little,  then  the  “ build  will  not  be  sufficient.  It  is  neces- 
sary also  to  point  out  that  the  capacity  of  the  trough  must  be  suitable 


Fig.  69.  Flexible  Moulding  Machine. 

approximately  to  the  size  of  the  loaf  to  be  moulded.  In  consequence  of 
these  two  important  considerations  a number  of  troughs  are  required  for 
each  such  moulder,  if  various  sizes  of  loaves — or  if  bread  made  from  doughs 
of  widely  differing  consistency — are  required  to  be  moulded.  In  practice 
the  cone-table  or  “ umbrella  moulder  is  now  only  employed  in  businesses 
with  uniform  outputs. 

741.  Flexible  Moulder. — In  order  to  provide  a moulder  which  shall  be 
capable  of  ready  and  instantaneous  adaptation  to  all  the  varying  require- 
ments of  average  bakeries,  the  inventors  of  the  previously-described  machine 
have  recently  put  upon  the  market  an  improved  and  perfected  form,  illus- 
trated in  Fig.  69,  which  they  term  the  flexible  moulder.  The  principle 
underlying  the  construction  of  this  machine  is  exactly  the  same  as  that  of 
the  “ umbrella  ''  type.  A flat  moving  table  is  formed  by  close-fitting  metal 
laths  connected  by  chains  which  constitutes  an  endless  iron  belt  running  over 
axles,  whose  axes  are  steeply  inclined  from  the  horizontal.  The  moulding 


652 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


troughs  are  thus  enabled  to  be  made  perfectly  straight  and  therefore  adjust- 
able for  capacity  by  the  simple  and  instantaneous  movement  of  a single  lever  ; 
they  can  consequently  mould  dough-pieces  of  widely  differing  weights,  found 
in  practice  to  vary  from  J lb.  to  4 lb.  pieces.  Being  suitably  supported  by 
bridges  spanning  the  entire  width  of  the  moulding  surface,  the  angularity 
of  the  troughs  upon  the  table  can  also  be  adjusted  at  will,  so  that  doughs  of 
widely  differing  consistencies  can  be  dealt  with.  This  machine  is  provided 
with  the  following  fittings — two  parallel  troughs,  a “ splitter,'’  which  cuts 
the  2 lb.  piece  of  dough  into  suitably  proportioned  pieces  for  forming  the 
“ tops  " and  “ bottoms  " of  cottage  loaves,  and  a tin  shaper  for  suitably 
shaping  tin  loaves  to  fit  the  particular  “ pans  " in  use.  It  may  therefore 
be  fairly  claimed  for  this  machine  that  it  is  universal  in  its  scope,  and  solves 
all  the  requirements  connected  with  the  “ balling  up  ” type  of  moulding. 

742,  Quality  of  Machine-Moulding. — It  is  perhaps  natural  that  sceptic- 

ism should  be  felt  in  regard  to  the  degree  of  good  workmanship  attainable 
by  such  machinery  as  has  been  described,  when  the  difficulty  of  getting 
good  moulding  by  hand  is  borne  in  mind.  Flexible  moulders  are  of  such 
recent  introduction  that  the  number  of  bakers  who  have  as  yet  had  the 
opportunity  of  seeing  such  machines  at  work  is  comparatively  limited. 
For  the  guidance  of  those  who  may  remain  unconvinced,  the  authors’  per- 
sonal experience  is  that  the  machine  above  described  will  mould  as  well  as 
the  journeyman,  with  this  important  point  in  its  favour — that  it  reaches 
the  same  standard  of  perfection  with  every  single  one  of  the  3,000  loaves 
which  it  is  capable  of  turning  out  per  hour.  The  journeyman’s  average 
workmanship  will  be  much  below  the  best  he  can  do,  but  the  flexible  moulder 
will  never  fall  below  its  best.  Hence,  moulding  machinery  should  be  care- 
fully investigated  on  behalf  of  every  progressive  machine  bakery.  , 

743.  Handing-Up  and  Proving. — If  a loaf  is  moulded  directly  after 
having  been  scaled  off  it  will  lack  development  and  cannot  possibly  be 
either  of  as  good  texture  or  bulk  as  it  should  be.  It  is  therefore  necessary 
to  give  each  dough-piece  a preliminary  moulding  after  being  scaled  off,  so 
that  it  may  have  a period  of  rest  in  which  to  recover  or  prove  before  being 
finally  moulded  into  shape  ready  for  baking.  This  preliminary  process  is 
called  “ handing-up  ” or  “ balling-up.”  The  above  remarks  apply  to 
ordinary  hand-made  bread,  notwithstanding  the  fact  that  there  are  a good 
many  bakeries,  especially  in  certain  districts,  where  the  loaf  is  finally  moulded 
directly  after  having  been  scaled  or  divided.  When  considering  the  ques- 
tion of  machine-moulding,  it  is  very  necessary  to  appreciate  accurately  the 
different  conditions  under  which  the  dough  is  then  handled.  When  hand- 
moulding is  employed  there  is  always  a considerable  number  of  dough -pieces 
on  the  table  which  have  been  scaled  or  divided  ; which  means  that  there 
is  always  a short  period  of  rest  before  moulding  actually  takes  place.  Slight 
as  this  rest  may  be,  it  is  essential,  and  gives  the  dough  an  opportunity  of 
recovery  before  being  moulded.  This  it  cannot  possibly  have  if  fed  auto- 
matically from  a divider  into  a moulder,  as  under  such  conditions  the  mould- 
ing takes  place  the  instant  the  piece  has  been  divided.  In  hand-w^orking 
there  is  no  reason  why  this  accumulation  of  loaves  and  consequent  rest 
should  not  be  allowed  to  take  place,  as  it  involves  no  extra  labour  and  is 
beneficial  to  the  dough.  With  machinery,  however,  unless  the  divider  feeds 
directly  into  the  moulder,  an  additional  man  would  be  required  to  feed  into 
that  machine.  The  necessity  for  handing-up,  although  ahvays  present 
if  a good  loaf  is  required,  is  all  the  more  pronounced  in  the  case  of  machinery; 
excepting  only  in  special  cases  such  as  with  very  slack  tin  doughs,  which 
may  go  direct  from  the  divider  to  the  moulder  with  reasonably  satisfactory 
results.  It  w'ill  be  understood,  how^ever,  that  these  remarks  apply  only  to 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  653 


cases  in  which  the  aim  is  only  an  average  quality  of  workmanship  ; there 
can  be  no  doubt  that,  where  a really  good  loaf  is  desired,  handing-up  is 
indispensable  and  remunerative.  Assuming  then  that  handing-up  must  be 
included  as  an  essential  operation  in  the  process  of  making  a good  loaf,  it 
becomes  necessary,  for  businesses  with  an  output  sufficiently  large  to  necessi- 
tate continuous  running  of  machines  during  working  hours,  to  instal  two 
moulding  machines  for  every  divider. 

744.  Hander-Up. — The  first  of  these  machines  is  coupled  direct  to 
the  divider  and  is  called  a hander-up.  In  principle,  the  hander-up  is 
exactly  similar  to  the  moulder ; but  as  the  newly  divided  loaf  is  of 
smaller  bulk  than  when  it  comes  to  be  finally  moulded  and  also  requires 
less  action  put  into  it,  the  hander-up  is  a smaller  machine  than  the  finishing 
moulder.  Businesses  with  outputs  up  to  one-half  the  capacity  of  the 
divider  installed, "need  not  instal  two  moulders,  but  by  employing  a finishing 
moulder  only  may,  by  arranging  for  the  machines  to  be  worked  inter- 
mittently, get  as  good  and  as  economical  work  as  the  full  equipment  yields 
to  the  business  with  a large  output.  In  either  event,  that  is  to  say  whether 
handing-up  and  moulding  are  done  in  separate  machines  or  on  a finish- 
ing moulder  only,  a period  of  rest,  averaging  about  20  minutes,  is  necessary 
between  the  two  operations,  and  provision  has  to  be  made  for  proving  the 
loaves  under  suitable  conditions  as  to  temperature  and  protection  from 
draughts.  To  use  any  of  the  older  devices  in  this  connection,  such  as 
drawers  or  proving  racks,  etc.,  entails  the  separate  handling  of  each  loaf 
into  and  out  of  the  accommodation  provided,  apart  from  the  labour  in 
feeding  the  loaves  into  the  final  moulder.  It  also  involves  possibilities 
of  bad  organisation  and  careless  marshalling  of  the  racks,  while  the  men 
may  not  take  the  batches  in  their  proper  consecutive  order  and  may  thus 
give  some  less  and  others  more  than  their  proper  period  of  proof.  Consider- 
able space  for  racks,  etc.,  and  for  moving  them  about  would  be  required. 

745.  Automatic  Prover. — To  obviate  the  foregoing  objections  and  dis- 
pense with  all  labour  between  the  hander-up  and  moulder,  and  ensure  the 
best  possible  development  of  the  loaf,  the  automatic  prover  has  been  intro- 
duced. This  machine  receives  the  loaves  from  the  hander-up,  and  dis- 
charges them,  fully  proved,  in  perfect  condition  to  the  moulder  ; the  whole 
process,  from  the  feeding  of  the  divider  to  the  discharge  of  the  finished  loaf 
ready  for  the  oven,  thereby  becomes  perfectly  automatic.  The  auto  prover 
(“  Pointon’s  ” patent)  is  essentially  a conveyor  suitably  regulated  as  to 
speed  (with  provision  to  vary  the  latter  if  required  and  thoroughly  enclosed 
to  exclude  draughts.  Further,  it  is  capable  of  being  heated,  and  in  any  event 
is  supplied  with  moist  vapour  so  as  to  prevent  a dry  skin  from  forming  on 
the  loaves,  which  are  consequently  proved  under  perfect  conditions. 

746.  Auto-Dividing,  Proving,  and  Moulding  Plant. — Fig.  70  shows  dia- 
grammatic representations  of  ,two  modifications  of  an  entire  plant  of  this 
description,  and  Fig.  71  a photographic  view  of  the  upper  one.  The 
loaves  coming  from  the  divider  fall  direct  into  troughs  on  the  hander-up 
and,  having  been  “ balled  up,"’  are  deposited  on  trays  (eight  pieces  on  each 
tray,  in  the  full  size  machine),  which  are  carried  on  chains,  traversing  the 
interior  of  the  prover  by  a circuitous  course  in  such  a manner  as  to  effect  as 
great  a saving  of  floor  space  as  height  of  ceiling  and  other  circumstances 
permit.  The  trays  move  intermittently,  and  of  course  at  a speed  suitable 
to  give  the  length  of  proof  required,  which  normally  is  from  15  to  20  minutes. 
Stepped  pulleys  are  provided  for  running  these  trays,  so  that  the  rate 
of  speed  can  be  controlled  within  certain  limits.  By  the  time  a tray  has 


654 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Fig.  70.  Diagrams  of  Automatic  Plants. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  655 


travelled  round  the  prover  and  has  allowed  the  loaves  deposited  upon  it 
from  the  hander-up  to  undergo  the  correct  period  of  proof,  it  reaches  a 
position  directly  over  the  delivery  band  and  by  engaging  with  a suitable 
gear  is  turned  upside  down,  depositing  its  load  of  eight  loaves  on  the  delivery 
band.  The  latter,  travelling  out  sideways,  delivers  the  loaves  singly  on 
to  a further  conveyor  which  feeds  them  (in  the  case  of  cottage  loaves  through 
the  splitter  already  referred  to)  into  the  finishing  moulder. 

The  lower  diagram  in  Fig.  70  shows  a form  of  prover  in  which  much 
greater  variations  in  length  of  proof  can  be  obtained  at  will.  By  con- 
venient mechanical  arrangements  the  long  conveying  band  can  be  “short 
circuited  ” at  desired  points  and  the  loaves  at  once  passed  direct  to  the 
finishing  moulder. 

The  prover  is  so  designed  that  it  can  be  arranged  in  a variety  of  ways  in 
order  to  suit  varying  local  conditions.  It  normally  occupies  a fioor  space  of 


Fig.  71.  View  of  Automatic  Plant. 

about  12  ft.  X 10  ft.,  but  can  be  suspended  under  the  ceiling  to  partly  over- 
hang the  moulder  ; or  it  may  be  fixed,  together  with  the  hander-up  and 
divider,  on  an  upper  floor  and  deliver  to  the  moulder  below.  The  best 
arrangement,  however,  to  suit  any  given  place  must  of  necessity  be  decided 
in  consultation  with  the  engineers.  On  the  face  of  matters  it  might  be 
thought  that  a prover  arranged  under  the  ceiling  would  be  best  with  a view 
to  the  saving  of  floor  space  thus  effected,  but  as  a matter  of  fact  there  are  a 
number  of  serious  objections  to  this  plan,  which  should  only  be  adopted  if 
exigencies  of  space  compel  this  course.  Every  one,  with  experience  of 
bakery  working,  well  knows  the  difficulty  of  ensuring  cleanliness  in  odd 
corners  and  inaccessible  places.  A prover,  with  its  damp  heat,  is  peculiarly 
liable  to  get  into  an  insanitary  condition,  and  thus  calls  for  rigid  cleanliness 
and  scrupulous  attention.  .Being,  therefore,  of  all  the  machines  employed 
in  the  bakery  to-day  the  one  most  needing  conscientious  inspection,  it  is  the 
last  which  should  be  so  placed  as  to  render  efficient  daily  examination  diffi- 
cult. 


656 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  prover,  illustrated  and  described,  thoroughly  meets  these  require- 
ments ; it  is  fitted  with  large  doors,  so  that  it  can  be  opened  out  every  day, 
and  thoroughly  ventilated.  Readily  removable  cloths  are  fitted  to  the 
trays,  so  that  their  frequent  washing  is  facilitated.  A permanently  fitted 
light  in  the  interior  is  recommended,  so  that  it  may  be  impossible  for  any 
part  of  it  to  get  into  an  unhygienic  and  objectionable  condition  without  instant 
detection. 

The  whole  of  the  trays  in  the  prover  can  be  easily  removed  (they  are 
only  hung  upon  pegs)  and  should  be  periodically  scrubbed.  V^Tien  the 
trays  are  removed,  the  interior  of  the  prover  can  be  entered  and  examined 
without  difficulty — the  reader  may  imagine  himself  standing  in  it,  as  in  a 
small  room.  The  result  of  five  or  six  years’  continuous  working,  in  actual 
bakehouse  use,  is  entirely  satisfactory  ; it  may  therefore  be  safely  stated 
that  the  apparatus  is  now  entirely  beyond  the  experimental  stage.  The 
prover  is  really  free  from  any  wear  and  tear,  as  the  speed  of  the  running 
parts  is  low,  and  the  load  on  the  trays  is  practically  balanced. 


Fig.  72.  Semi-Automatic  Plant. 


The  power  required  for  driving  the  complete  installation,  consisting  of 
dough  divider,  hander-up,  auto  prover  and  finishing  moulder,  is  only  about 
8 h.p.  The  plant,  when  once  installed,  is  therefore  not  expensive  to  run, 
since  the  whole  of  the  operations  indicated  are  carried  out  with  one  man  for 
feeding  the  dough  into  the  divider.  When  the  dough  has  been  thus  fed,  a 
maximum  output  of  finished  loaves  from  the  moulder  is  obtained  at  the 
rate  of  2,400  pieces  per  hour.  For  bakeries  requiring  intermittent  working 
a semi-auto  plant  is  available,  of  which  a view  is  shown  in  Fig.  72. 

747.  “ Setters.” — The  appliances  hitherto  in  use  in  modern  bakeries  for 
receiving  the  moulded  loaves,  and  for  conveying  them  to  the  ovens,  in  so 
far  as  they  have  been  specially  adapted  at  all,  have  all  been  modifications 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  657 


more  or  less  of  the  type  introduced  in  the  early  days  of  drawplate  ovens 
under  “ Price’s  ” patent.  An  upright  framing,  mounted  centrally  upon  a 
bogie  fitted  with  castors,  carries  rods  or  brackets  projecting  on  either  side. 
Upon  these  brackets  rest  trays,  open  upon  one  of  the  longer  sides  only.  The 
loaves  are  set  upon  these  trays,  which  fit  the  width  of  the  drawplate,  and 
are  slid  off  upon  the  latter,  as  shown  in  the  illustration.  Fig.  73. 


Fig.  73.  Loading  Drawplate  from  Setter. 


Fig.  74.  Improved  Setter. 


U F 


658 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Cloths,  fixed  to  the  central  upright  of  the  setter  rack,  are  spread  over 
the  loaves  while  proving.  On  another  plan,  the  setter  boards  come  close 
together,  and  with  closed  sides  to  the  rack,  are  kept  protected  from  draughts  ; 
the  trays  are  then  placed  upon  the  rack  with  their  open  side  inwards  (see 
Fig.  74). 

748.  Final  Prover. — Something  more  than  the  above  is  required,  especi- 
ally for  dealing  quite  satisfactorily  with  cottage  or  other  loaves  that  are 
made  from  two  pieces,  which  are  “ topped,'"  i.e.,  placed  on  top  of  one  an- 
other. It  is  necessary,  in  order  to  get  the  best  results,  to  give  the  two  pieces 
w'hich  are  to  form  the  loaf  a further  rest,  after  coming  from  the  finishing 
moulder,  and  to  meet  this  requirement  a secondary  or  final  prover  is 
now  being  placed  upon  the  market.  Fig.  75  shows  a longitudinal  section  of 


s -f  s e y s reeT» 


Fig.  75.  Final  Prover. 

this  machine,  from  which  it  will  be  seen  that  the  dough-pieces  are  placed 
upon  trays  similar  to  those  used  in  the  first  automatic  prover,  and  moving 
intermittently.  The  loaves  are  given  a maximum  proof  of  10  minutes, 
while  the  capacity  of  the’machine  is  equal  to  the  output  of  the  full  automatic 
plant.  The  loaves  are  removed  from  the  prover  by  hand,  ready  to  be 
placed 'on  the  setters. 

The  Fully  Automatic  Bakery  is  not  yet  in  operation  in  this  country  (if 
anywhere),  but  will  before  long  in  all  probability  become  an  accomplished 
fact  ; the  subject  is  dealt  with  in  paragraph  762  because  it  is  necessary  to 
first^consider  the  question  of  ovens  in  all  its  bearings. 

749.  Ovens. — This  subject  is  still  one  of  the  most  vital  importance  to 
the  baker,  and  although  the  oven  is  obviously  the  oldest  item  in  the  equip- 
ment of  his  business,  yet  it  has  undergone  greater  developments  during  the 
present  generation  than  in  all  the  previous  history  of  the  baking  trade. 

Rif  dealt  with  exhaustively,  the  subject  of  ovens  would  occupy  a large 
volume  by  itself,  and  therefore  only  so  much  of  it  can  be  freated  here,  as 
applies  to  the  average  modern  requirements  and  as  specially  affects  large 
separate  interests  in  this  country.  Among  general  types  it  is  necessary 
to  discriminate  between  ovens  heated  (1st.)  internally,  (2nd.)  in  part  in- 
directly, and  (3rd.)  by  purely  mechanical  means,  Le.,  quite  externally. 

750.  Internally  Heated  Ovens. — These  may  be  dismissed  very  shortly. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  659 


They  consist  merely  of  a masonry  or  brickwork  chamber,  communicating 
with  a chimney  and  heated  by  fire  direct,  applied  in  various  ways.  The 
heat  thus  stored  is  utilised,  after  the  oven  has  been  swept  out,  for  baking 
the  bread.  During  all  known  history  until  modern  times  this  was  practi- 
cally the  only  principle  applied  to  ovens  for  bread-baking  purposes,  and 
it  is  undeniable  that  if  the  manipulation  of  such  an  oven  is  properly  under- 
stood and  attended  to,  perfect  results  as  regards  baking  can  be  obtained. 
The  principal  objections  are  want  of  fuel  economy,  loss  of  time  in  re-heating, 
utter  dependence  upon  skill,  and  absence  of  hygiene. 

751.  Hot  Air  Ovens. — These  are  subject,  more  or  Jess,  to  the  same  objec- 
tions. Their  construction  differs  from  that  of  internally  heated  ovens  by  the 
furnace  or  fireplace  being  independent  of  the  baking  chamber.  The  heated 
gases  from  the  fire  are  conducted  through  flues  placed,  as  far  as  possible, 
in  such  a manner  as  to  enable  the  baking  chamber  to  be  heated  by  the  tiles, 
which  form  the  covering  or  walls  of  these  flues.  The  waste  gases  are,  or 
may  be,  also  admitted  eventually  to  the  baking  chamber  itself.  Dampers 
are  introduced  with  the  object  of  regulating  the  heat,  but  are  not  invariably 
successful.  Provided  that  such  ovens  are  well  designed,  they  bake  well, 
and  are  more  nearly  continuous  than  internally  fired  ovens.  Against  this 
must  be  set  the  drawback  that  most  ovens  of  this  kind  consume  considerable 
amounts  of  fuel.  Unless  exceedingly  well  built,  the  obviously  numerous 
flues  render  frequent  repairs  of  this  type  of  oven  necessary. 

752.  Mechanically  Heated  and  Electric  Ovens. — ^These  represent  the 
modern  development,  and  lend  themselves  to  specialisation  in  astonishing 
variety,  of  which  the  leading  examples  will  be  reviewed  after  a short  general 
survey  of  the  “ mechanical  means  available  for  heating  the  ovens.  This 
class  of  oven  may  be  fairly  described  as  externally  fired,  but  internally 
heated,  the  significance  of  which  charactisation  will  in  due  course  become 
clear. 

Ovens  heated  electrically  would  certainly  fulfil  the  most  exacting  require- 
ments in  every  respect,  were  it  not  for  the  fact  that  the  electrical  generation 
of  heat  absorbs  far  too  much  energy  to  allow  of  working  costs  which  are 
commercially  practicable.  Apart  from  miniature  ovens,  for  laboratory 
work,  a few  electrically  heated  ovens  have  been  built,  but  the  amount  of 
current  consumed,  about  80  kilowatts  per  one  sack  batch,  is  so  enormous 
that,  however  low  a price  per  B.T.  unit  be  assumed,  the  cost  will  be  seen  to 
be  quite  prohibitive. 

Some  startling  revolution  of  the  means  for  producing  electrical  current, 
or  some  equally  wonderful  invention  for  the  conversion  of  electrical  energy 
into  heat,  must  therefore  be  awaited,  before  electrical  heating  of  ovens  can 
become  a question  of  practical  politics. 

753.  Perkins’  Tube  or  Steam  Pipe  Ovens. — As  a matter  of  fact,  Perkins’ 
invention  of  the  closed  circuit  system,  and  the  subsequent  improvement 
thereon  embodied  in  the  “ Perkins  ” sealed-end  tube,  was  the  epoch-making 
departure  from  the  accepted  notions  of  his  day,  which  has  brought  about 
the  revolution  in  ovens  effected  in  recent  years.  It  is  an  interesting  testi- 
mony of  the  value  of  Perkins’  invention  that  the  first  man  to  employ  ovens 
of  his  make,  Mr.  H.  W.  Nevill,  built  up  in  comparatively  few  years  an  enor- 
mous business.  The  Perkins’  invention  is  based  upon  scientifically  correct 
principles.  The  boiling  point  of  all  liquids  bears  a definite  relationship  to 
the  pressure  to  which  the  liquid  is  at  the  time  subjected.  The  higher  the 
pressure  the  higher  is  the  temperature.  The  following  is  the  principle  of 
Perkins’  apparatus  : — A system  of  hermetically  sealed  pipes,  completely 
filled  with  water,  is  provided,  and  at  its  highest  point  an  expansion  vessel 


r 


660 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


is  attached  in  order  to  accommodate  the  extra  volume  of  the  water  when 
heated.  By  exposing  a suitable  proportion  of  this  system  of  piping  to  the 
action  of  a fire  the  pressure  in  the  apparatus  was  enabled  to  rise  to  the 
point  corresponding  to  a temperature  adequate  for  the  baking  of  bread. 
Obviously  the  greater  portion  of  this  apparatus  was  arranged  to  be  within 
the  oven  chamber,  while  the  portion  exposed  to  the  fire,  arranged  as  a coil 
in  a brick-lined  iron  furnace,  was  placed  at  any  convenient  point,  as  in  a 
stokehole  or  room  adjoining  the  bakehouse.  Many  ovens  were  constructed 
in  this  manner,  and  remained  successfully  at  work  for  many  years.  Perkins, 
however,  soon  concluded  that  it  would  be  better  to  dispense  with  any  form 
of  joints  for  connecting  up  the  various  lengths  of  pipe,  from  which  his 
apparatus  was  constructed.  (The  joint  which  he  invented  was  neverthe- 
less remarkably  efficient,  and  is  the  only  one  used  to  this  day  for  this  class 
of  work,  including  the  “ loop-tube  ""  ovens  referred  to  later  on.)  He  therefore 
adopted  the  plan  of  using  a large  number  of  single  straight  tubes,  welded  at  each 
end,  and  with  a portion  of  each  tube  projecting  into  a furnace  constructed  at 
the  back  of  the  oven  and  fired  from  a stokehole  separate  from  the  bakehouse. 
These  tubes  were  set  in  two  rows,  the  lowest  of  which  acted  as  firebars,  and 
upon  them  the  fire  rested.  To  this  day  this  oven  is  the  prototype,  and 
apart  from  improvements  in  details  and  adaptations  to  particular  require- 
ments remains  unaltered.  These  single  sealed  tubes  possess  a practically 
unlimited  life — they  have  been  tested  carefully  after  forty  years  of  hard 
continuous  service,  and  have  been  found  absolutely  intact  and  fit  to  con- 
tinue their  work  indefinitely.  They  obviously  avoid  the  risk  inseparable 
from  joints,  and,  unlike  tubes  arranged  in  complicated  coils  and  intricate 
loopings,  are  readily  and  inexpensively  replaced,  should  occasion  arise, 
without  interruption  or  disturbance  of  working.  The  so-called  loop-tube 
ovens  are  a half-way  stage  between  Perkins’  earlier  and  later  systems. 
The  tubes,  instead  of  being  sealed  at  either  end,  are  endless ; that  is  to  say, 
have  their  ends  jointed  up  to  form  a continuous  tube,  just  as  is  the  case  in 
Perkins’  first  construction.  Wliile  each  loop-tube  is  therefore  much  longer 
and  more  complicated  in  shape  than  Perkins’  later  straight  tube,  it  is  shorter 
than  the  circuit  employed  in  Perkins’  first  oven.  The  loop-tube  has  nearly 
all  the  faults  of  the  first  Perkins’  oven,  but  lacks  the  best  points  in  the 
straight  tube  ; yet  experience  proves  that  the  Perkins’  sealed-end  tube 
accomplishes  everything  required  of  it  by  the  baker,  and  is  not  excelled 
by  the  loop-tube  in  any  single  direction.  Claims  have  been  made  on  behalf 
of  the  loop-tube,  in  that  ovens  employing  it  are  more  economical  in  fuel  than 
are  ovens  fitted  with  sealed-end  pipes.  This  is  not  borne  out  by  facts,  if 
ovens  of  modern  construction  are  compared  under  equal  conditions  ; what 
gave  a certain  amount  of  colour  to  these  statements  is  that  the  long  narrow' 
furnaces  peculiar  to  earlier  Perkins’  construction  need  considerable  care  to 
ensure  that  the  consumption  of  fuel  be  kept  to  a minimum.  As  w'orkmen 
are  careless,  and  mostly  fire  in  the  manner  involving  least  trouble  to  them- 
selves, the  fuel  consumed  in  ovens  with  these  long  narrow  furnaces  usually 
exceeded  considerably  the  amount  actually  required.  The  “ Perkins  ” 
ovens  have,  how'ever,  for  some  years  been  equipped  wffih  furnaces  which 
make  this  impossible,  and  practically  restrict  the  consumption  of  fuel  to  the 
amount  actually  required. 

It  follow'S  that  the  sealed-end  tube  is  considered  preferable,  and  the 
reasons,  in  so  far  as  they  affect  the  baker,  may  be  shortly  stated  thus  : it 
lends  itself  to  constructions  which  are  as  economical,  as  uniform  in  baking,^and 
as  continuous  as  any  that  are  possible  with  any  other  system.  In  addition, 
it  is  more  durable,  involves  less  risk,  avoids  all  possibility  of  an  oven  being 
put  temporarily  out  of  use,  and  if  replacements  are  required,  enables  these 
to  be  carried  out  at  a nominal  expense.  As  the  original  patents  for  these 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  661 


various  systems  referred  to  have  now  expired,  they  are  all  equally  avail- 
able for  oven  manufacture. 

754.  Producer  Gas  Firing. — This  has  proved  the  subject  of  an  interesting 
development  during  the  last  ten  years.  The  firing  of  individual  furnaces  to 
each  oven  naturally  calls  for  considerable  labour  in  a bakery  with  a number 
of  ovens,  and  to  a certain  extent  makes  the  maintenance  of  suitable  tempera- 
tures dependent  upon  the  care  of  the  stoker.  With  gas  firing  these  draw- 
backs are  dispensed  with  and  the  oven  temperatures  are  controlled  from 
the  front  of  the  oven  and  can  be  readily  supervised  by  the  foreman.  A gas 
producer  similar  to  that  described  in  paragraph  706,  but  without  arrange- 
ments for  cooling,  scrubbing  and  “ purifying  ” the  gas,  is  employed,  and 
the  hot  gas  is  conveyed  to  the  oven  furnaces,  there  to  be  burned,  by  the 
aid  of  a secondary  air  supply,  in  such  a manner  that  the  flames  play  upon 
the  ends  of  the  steam  tubes.  This  air  supply  is  pre-heated  by  the  waste 


Fig.  77.  Stokehole  of  Producer  Gas-Fired  Ovens. 


gases  from  the  furnaces.  This  system  has  been  applied  to  a large  number 
of  ovens  in  this  country,  is  quite  successful,  and  is  certainly  most  cleanly 
and  convenient  in  working.  There  is  no  fear  of  danger  from  any  source  or 
of  breakdown,  and  the  only  point  needing  to  be  carefully  watched  is  that 
the  periodical  cleaning  of  the  gas  mains,  valves,  and  burners,  from  which  the 
dust  that  gradually  accumulates  has  to  be  removed,  is  done  conscientiously. 
It  is  obvious  that  although  99  per  cent,  of  the  gas  and  air  passages  may  be 
perfectly  clear,  if  only  at  one  point  an  accumulation  is  left,  the  whole  of,  or 
such  part  of  the  ovens  as  happen  to  be  on  the  chimney  side  of  the  obstruc- 
tion, may  work  sluggishly.  This  cannot  be  considered  a fault  in  the  system, 
it  is  only  mentioned  as  a point  that  calls  for  attention,  and  is  similar  to  the 
dependence  upon  proper  lubrication  of  the  best  running  bearing  ever  made. 
From  these  remarks  it  will  be  seen  that  easy  access  to  all  gas  and  air  mains, 
valves,  and  passages,  is  a matter  calling  for  the  engineer’s  careful  attention. 
Any  one  intending  the  erection  of  a new  bakery,  with  not  less  than  six 


662  THE  TECHNOLOGY  OF  BREAD-MAKING. 

ovens,  should  certainly  give  the  question  of  gas  firing  his  careful  consider- 
ation. 

Fig.  77  shows  a view  in  the  stokehole  of  a large  bakery,  with  rows  of 
ovens,  each  fired  from  a separate  producer  ; the  absence  of  fire-doors  and 
the  generally  “ clean  ""  appearance  of  the  oven-backs,  is  very  striking.  The 
small  circular  manholes  are  the  sighting  doors,  through  which  the  flames 
can  be  seen  playing  upon  the  pipes  ; the  square  patches  close  to  are  open- 
ings giving  access  to  gas  mains,  burners,  etc.,  for  cleaning  purposes.  The 
coke  is  kept  on  the  top  of  the  ovens  and  is  trolleyed  to  the  producers  as 
convenient  ; the  producers  are  large  enough  to  require  filling  up  only  once 
in  12  hours. 

755.  Setting  Bread, — The  system  of  setting  bread  in  a peel  oven,  by 
means  of  the  ordinary  peel,  is  too  well  kno™  to  need  description.  An 
attempt  has  been  made  to  provide  mechanical  means  of  performing  this 
operation  (Dempsey’s  patent),  and  so  far  as  the  working  of  this  ingenious 
apparatus  is  concerned  it  performs  the  task  well.  Nevertheless  the  idea 
is  not  likely  to  meet  with  general  adoption,  because  it  fails  to  meet  the  con- 
ditions, which  are  necessary  to-day,  for  producing  a generally  saleable 
loaf.  As  regards  drawplate  ovens  the  question  of  setting  has  been  dealt 
with  under  paragraph  747  (see  Fig.  73). 

756.  Oven  Types. — The  withdrawable  baking  plate  was  the  subject  of 
practicable  proposals  by  Perkins.  At  a later  period  “ Wieghorst’s  ” early 
productions  made  their  appearance  ; following  upon  these  the  dravq)late 
proper  (Pfleiderer’s  patent)  was  introduced  largely  into  this  country  towards 
the  end  of  the  last  century,  and  has  since  spread  all  over  the  civilised  world. 
The  dra'wq)late  proper,  with  plate  travelling  independently  upon  the  draw- 
plate  carriage,  employing  only  rolling  bearings  inside  the  oven,  and  leaving 
the  bakehouse  floor  entirely  unobstructed  when  not  drawn  out,  has  since 
the  beginning  of  this  century  certainly  become  the  standard  bread  oven. 


Fig.  78.  One-Deck  Drawplate  Ovens. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  663 


Fig.  79.  Two-Deck  Drawplate  Ovens. 


Fig.  80.  Stokehole  of  Coke-Fired  Ovens. 


664 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Replacing  old  ovens  in  existing  bakeries,  and  nearly  always  being  installed 
in  aU  new  bakeries  with  any  pretence  to  being  abreast  of  modern  ideas  the 
drawplate  has  long  ago  demonstrated  the  fact  of  its  entire  suitabihty  for  all 
baking  requirements.  Fig.  78  shows  a battery  of  one-deck  drawplate  ovens, 
which  it  may  be  remarked  incidentally  are  producer  gas -fired,  although  the 
only  distmguishing  feature  as  regards  this  will  be  noticed  in  the  small  valves 
fitted  above  each  oven  close  to  the  “ dummy  ''  clock.  Fig.  79  shows  a 
battery  of  two-deck  ovens,  coke  fired.  Fig.  80  gives  a view  in  the  stoke- 
hole of  a coke-fired  battery,  from  which  the  smallness  of  the  modern  furnace 
will  be  noticeable.  Drawplates  are  made  in  many  different  sizes,  to  suit 
requirements  of  trade  as  well  as  to  conform  to  restrictions  in  regard  to 
space.  It  may  be  taken  that  the  plate  should  not  exceed  6 ft.  in  width 
in  all  cases  where  setting  has  to  be  done  by  hand  (conf.  paragraph  699), 
but  when  only  bread  is  baked  which  may  be  handled  with  setters,  the 
width  may  be  as  much  as  8 ft.  4 in.  Greater  widths  should  be  avoided,  as 
leading  to  difficulties  in  setting,  on  account  of  the  heavy  weights  to  be 
handled. 

S^lit  Drawplates. — Fig.  81  shows  a very  useful  modification  (Pointon’s 


Tig.  81.  Oven  with  Split  Drawplate. 

patent)  of  the  standard  arrangement,  enabling  a drawplate  oven  to  be 
adopted  in  bakeries  possessing  only  a very  limited  floor  space.  The  plate 
is  cut  transversely  into  two  equal  halves,  and  when  drawn  out,  the  special 
gearing  shown  enables  the  first  half  to  be  lowered,  so  that  the  back  half  can  be 
drawn  forward  over  it.  After  setting  the  batch  on  the  back  half  the  process 
is  reversed.  These  ovens  are  in  actual  use  and  answer  admirably  ; it  will 
be  seen  that  they  not  only  enable  a drawplate  to  be  used  where  it  would 
be  otherwise  impossible  to  do  so,  but  that  a plate,  about  11  ft.  long,  can 
be  used  in  a 6 ft.  space  : in  less  space  therefore  than  a similar  size  peel 
oven  could  be  worked  in. 

Combined  Drawplate  Peel  Oven. — Fig.  82  shows  this  very  useful  combina- 
tion. The  carriage  of  the  drawplate  carries  a chequered  iron  plate  platform 
(barely  visible  in  the  illustration  because  almost  entirely  hidden  by  the 
drawplate  itself)  from  which  the  peel  oven  is  conveniently  worked.  The 
step  just  above  the  car  wheel  gives  easy  access  to  this  platform.  With 
regard  to  the  firing  of  this  oven  refer  to  “ furnace  arrangements  ""  further  on. 

Portable  Drawplate  Ovens. — A useful  small  oven,  very  suitable  for  caterers, 
is  shown  in  Fig.  83  (Ihlee's  patent).  The  fact  that  the  special  design  of 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  665 


Fig.  82.  Combined  Drawplate  and  Peel  Oven. 


Fig.  83.  Portable  Drawplate  Oven. 

running  gear  employed  dispenses  with  all  outer  supports,  makes  this  oven 
quite  self-contained  and  truly  transportable. 

Oven  Types  : Peel  Oven. — The  standard  peel  oven,  although  made  in 
any  size  to  suit  requirements,  does  not  call  for  lengthy  description.  Figs. 


666 


THE  TECHNOLOGY  OF  BREAD-MAKING 


Fig.  84.  Single-Deck  Peel  Oven. 


Fig.  85.  Double-Deck  Peel  Ovens. 


84  and  85  show  typical  arrangements  of  one-  and  two-deck  varieties,  the 
former  fitted  with  pro  vers  under,  the  latter  with  pits  for  working  the  bottom 
ovens. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  667 


Portable  Ovens. — Fig.  86 
shows  a very  excellent  two- 
deck  specimen,  with  prover 
and  hot-water  tank.  p-  | 
Field  Ovens,  as  shown  in 
Fig.  87,  are  mounted  on 
platform  waggons  and  en- 
able baking  of  the  very  best 
type  to  be  carried  on  for 
troops  in  camp  or  on  the 
march.  This  two-deck  oven, 
although  only  weighing  22 
cwt.,  bakes  rations  for  over 
2,000  men  per  day  : a very 
good  indication  of  the  effi- 
ciency of  the  steam-pipe 
principle.  It  may  be  fired 
with  coke  or  can  be  heated 
with  wood  : even  green 
wood  cut  on  the  march 
answers  the  purpose.  The 
insulation  on  these  ovens, 
despite  their  elegance  and 
lightness,  is  so  excellent 


Fig.  86.  Portable  Oven. 


Fig.  87.  Field  Oven. 


668  THE  TECHNOLOGY  OF  BREAD-MAKING. 

that  baking  has  been  carried  on  with  3 in.  of  unmelted  snow  lying  on  the  top 
of  the  oven. 

Shi'p  Ovens. — War  ships  and  merchantmen  are  now  as  well  equipped 
as  any  establishment  ashore,  and  carry  fully  equipped  bakeries  with  knead 
ing  machines,  mostly  driven  by  electric  motor  direct,  and  steam-pipe  ovens. 
Fig.  88  shows  one  of  the  large  size  and  substantial  two-deck  ovens  carried 
by  our  large  liners. 


& 'Jerkins 


yfTffiSOMUSS 


Fig.  88.  Ship  Oven. 

Hotel  Ovens. — Large  hotels  and  businesses  with  dining  accommodation 
for  large  staffs  frequently  provide  themselves  with  modern  equipment, 
and  Fig.  89  shows  a typical  case  of  this  kind.  In  this  the  oven  seen  on  the 
left-hand  side  is  a “ Vienna  oven  with  sloping  sole,  powerful  steam  generat- 
ing apparatus,  steam  valve  for  drawing  ofi  vapour,  and  patent  oven-light 
to  protect  the  gas  jet  from  the  effects  of  steam.  This  type  of  oven  is  fitted 
with  the  Monier  sole,  referred  to  in  a subsequent  paragraph,  and  admirably 
bakes  rolls  of  the  true  Vienna  style — that  is  to  say,  rolls  with  a thin  “ egg- 
shell crust  and  perfect  bloom  and  gloss  for  consumption  within  a few 
hours  of  baking.  Vienna  rolls,  as  more  often  required  in  this  country,  require 
an  oven  somewhat  differently  arranged,  and  are  better  produced  by  the  aid 
of  steam  from  a boiler  as  they  must  be  soaked  more  thoroughly  and  require 
a heavier  crust  so  as  to  keep  brittle  for  a longer  period. 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  669 


Fig.  89.  Hotel  Oven. 


Fig.  90.  Coverplate  Oven. 


670 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Coverplate  Oven. — A very  special  type  of  oven  has  been  quite  lately  pro- 
duced, which  cannot  be  classified  either  as  a peel  or  drawplate,  and  to 
which  the  name  of  “ Coverplate  ’’  oven  (Ihlee’s  patent)  has  been  given. 
It  is  essentially  a hot  plate,  fitted  with  a removable  lid  or  cover,  in  which 
is  arranged  a system  of  pipes  to  give  top  heat.  The  idea  is  to  give  a large 
batch  capacity  (40  dozen  2 1b.  loaves)  in  a minimum  of  working  space,  with 
the  least  possible  weight  and  expense.  The  oven  is  designed  to  deal  with 
Scotch  batch  bread,  but  might  also  suit  similar  classes  of  goods  much  made 
in  Ireland.  The  furnace  gases  can  be  taken  over  the  tops  of  the  loaves  to 
give  the  “ flashing  ''  effect  required  in  Scotland.  Figs.  90  and  91  show  tlie 


Fig.  91.  Coverplate  Oven  with  Cover  Lifted. 

oven  as  fitted  in  a Glasgow  bakery,  where  the  work  done  appears  to  be 
excellent  and  to  meet  the  high  standard  demanded  there.  It  remains  to 
be  seen  if  the  oven  will  find  anything  like  general  favour ; but  it  has  done  so 
well  hitherto,  that  any  one  contemplating  ovens  for  work  of  this  class  should 
certainly  make  every  inquiry  into  its  capabilities.  When  the  cover  is  lifted, 
as  shown  in  Fig.  91,  the  method  of  procedure  is  of  course  exactly  the  same 
for  setting  and  drawing  a batch  as  would  be  the  case  with  a drawplate. 
For  the  many  existing  bakeries  in  Scotland,  with  flats  on  upper  floors,  the 
scheme,  if  practicable,  would  appear  to  possess  marked  advantages  because  of 
tlie  great  saving  in  weight,  combined  with  economy  in  floor  space. 

Arrangement  of  Furnaces. — All  the  ovens  referred  to  can  be  built  to  be 
fired  from  the  front,  back,  or  at  either  side,  but  of  course  preference  must  be 
given  to  back  firing  in  all  cases  where  exigencies  of  space  do  not  make  this 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  671 


impossible.  One  furnace  to  two  baking  chambers,  as  in  two-deck  ovens, 
should  be  avoided  because,  notwithstanding  any  claims  to  the  contrary, 
effective  control  of  each  chamber  is  only  possible  when  each  chamber  has 
its  own  furnace.  The  drawback  to  having  a furnace  to  each,  in  two-deck 
ovens,  has  hitherto  been  that  this  construction  entailed  having  the  sole  of  the 


Fig  92.  Beanes’  Furnace  Construction. 


upper  oven  at  an  inconveniently  great  distance  from  that  of  the  lower 
one.  Beanes’  patent  construction.  Fig.  92,  avoids  this  difficulty,  and 
enables  the  soles  to  be  kept  at  the  same  minimum  distance  apart  as  in  the 
two -deck  oven  with  one  furnace.  For  the  purpose  of  these  observations 


672 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


it  is  assumed  that  each  chamber  has  at  least  two  rows  of  tubes,  as  in  some* 
cases  ovens  are  built  with  two  decks  and  only  three  rows  altogether.  This 
is  bad  practice,  and  does  not  lead  to  a saving  at  all  commensurate  with  the 
loss  in  efficiency,  durability,  and  continuity  of  the  oven. 

757.  Oven  Fittings. — Drawplate  ovens  are  commonly  equipped  with  a 
“ dummy  clock  to  each  chamber  for  marking  up  the  time  at  which  the 
batch  should  be  drawn.  There  is  also  a mercurial  thermometer  and  means 
for  injecting  steam,  while  efficient  steam  generators  may  be  arranged  for 
if  required.  Peel  ovens  are  fitted  with  a thermometer,  and  either  a gas 
bracket  or  patent  oven-light  as  may  be  desired.  The  latter  has  the  advan- 
tage of  fighting  up  the  oven  without  being  effected  by  the  steam,  and  is 
certainly  to  be  strongly  recommended  on  that  account  ; oil  lamps  are  sup- 
plied where  gas  is  not  available.  Doors,  arranged  to  slide  vertically,  should 
be  fitted  for  Vienna  ovens,  or  where  small  goods  require  setting  in  a bath 
of  steam,  as  the  doors  may  then  be  readily  adjusted  to  a convenient  height,, 
while  retaining  the  steam  at  a lower  level  than  would  otherwise  be  the  case. 

Pyrometers  are  quite  out  of  date  in  steam-pipe  ovens,  as  the  temperature 
can  never  rise  to  a point  wffiich  would  endanger  a thermometer,  which  is,, 
if  of  good  make,  absolutely  reliable  and  will  always  read  accurately.  Good 
working  instructions  should  be  insisted  upon  with  new  ovens,  and  kept  in 
a conspicuous  place  in  the  stokehole.  Their  observance  should  be  rigidly 
insisted  upon  by  the  proprietor  or  manager.  i 

As  regards  oven  soles,  all  ordinary  styles  of  bread  current  in  this 
country  will  be  baked  satisfactorily  on  iron  soles.  A very  useful  method 
of  indelibly  marking  each  loaf  with  the  name  or  trademark  of  its 
maker  is  possible  with  drawplates,  by  having  the  plate  divided  into 
suitable  squares,  in  each  of  which  the  desired  mark  is  cast,  so  that  it  is 
positively  baked  into  the  loaf.  The  plan  is  in  use  in  many  places  and  answers 
admirably.  For  slab  cakes,  sponge  cakes,  fingers,  and  similar  goods,  as 
well  as  for  Vienna  rolls,  etc.,  a sole  of  earthenware  material  is  often  preferred. 
“ Monier  ""  soles,  as  manufactured  by  Werners,  have  proved  entirely  satis- 
factory in  these  cases,  and  can  be  strongly  recommended  as  having  now  stood 
the  test  of  over  ten  years’  continuous  working.  Tiles,  unless  sufficiently 
tliin,  must  be  condemned,  as  otherwise  they  interpose  too  great  a resistance 
to  the  transmission  of  heat  from  the  tubes,  the  safety  of  which  is  thereby 
endangered. 

The  cases  where  iron  soles  do  not  fully  cover  all  requirements  are,  how- 
ever, comparatively  few  and  far  between. 

758.  Automatic  Ovens. — Travelling  ovens  of  the  type  used  in  biscuit 
manufacture  are  not  suitable  for  bread-making  ; at  least  they  do  not  lend 
themselves  to  the  production  of  modern  thin-crusted  loaves  with  a rich 
bloom,  adequate  bulk,  and  baking  with  a minimum  loss  of  weight  in  the  loaf. 
As  no  bakery  exists  in  this  country  as  yet  employing  an  automatic  bread 
oven,  no  detailed  reference  can  be  made  to  it  here,  as  the  authors  have 
throughout  confined  themselves  to  dealing  with  constructions,  the  practical 
working  of  which  has  come  within  their  personal  experience.  The  subject 
is,  however,  of  sufficient  interest  to  warrant  the  announcement  that  a fully 
detailed  scheme  has  been  patented.  This  has  been  carefully  examined 
and  appears  to  be  perfectly  practicable,  so  far  as  such  a conclusion  can  be 
arrived  at  without  the  experience  of  actual  practice  to  confirm  its  value. 
It  will  be  interesting  to  see  what  the  next  few  years  will  bring  forth  in  this 
direction.  The  chief  barrier  to  progress  in  this  matter  is  the  diversity  of 
styles  in  loaves  produced  in  the  average  bakery  in  this  country,  and  probably 
if  an  oven  of  the  auto  type  could  be  tried  upon  an  absolutely  uniform  trade 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  673 


of  sufficient  dimensions,  such  technical  points  as  still  require  to  be  proved 
practicable  would  soon  be  established  beyond  doubt. 

759.  Oven  Firing. — It  is  not  possible  to  give  any  detailed  instructions 
on  this  subject,  as  the  treatment  must  necessarily  vary  considerably  for 
different  makes  of  ovens.  It  may,  however,  be  said  that  where  possible 
in  regard  to  cost,  coke  is  much  the  cleanest  and  most  satisfactory  fuel  to  use. 
It  saves  much  trouble  and  dirt  and  avoids  all  risk  of  creating  a nuisance 
by  the  emission  of  smoke.  With  every  kind  of  fire,  and  especially  with 
ovens,  “ little  and  often  should  be  the  golden  rule  in  adding  fuel.  The 
saving  of  trouble  by  filling  furnaces  to  their  fullest  capacity,  and  often 
beyond  that,  is  pernicious  : it  literally  wastes  an  enormous  percentage  of 
the  fuel  and  leads  to  exceedingly  bad  results  in  the  bargain.  Avoid 
burning  rubbish,  an  oven  furnace  is  not  a destructor,  and  avoid  offal — egg 
shells,  remains  of  meat,  etc.,  especially  if  an  oven  be  fitted  with  a copper 
boiler,  as  gases  are  formed  which  are  detrimental  to  the  copper.  Do  not 
use  coke  in  large  unbroken  lumps — ^pieces  about  the  size  of  a duck^s  egg  are 
quite  the  maximum  that  should  be  allowed.  Keep  the  flues  clean  by  regular 
periodical  sweeping,  and  remember  that  the  tube  ends  should  also  be  kept 
clear  of  dust.  For  the  rest  it  is  necessary  to  follow  the  directions  supplied 
by  the  oven  builders. 

760.  Nature  of  Coke  Combustion. — This  subject  is  of  great  practical 
importance  in  connection  with  the  whole  question  of  the  firing  of  oven  fur- 
naces, and  so  merits  a somewhat  careful  examination.  First  of  all,  coke 
has  the  advantage  of  producing  an  absolutely  smokeless  fire,  and  so  soot 
deposits  and  their  inconveniences  are  practically  obviated.  On  the  other 
hand,  the  flameless  combustion  of  carbon  produces  heat  which  is  not 
only  intense  but  also  very  local,  so  that  the  furnace  itself  is  very  hot,  in 
comparison  with  flues  at  some  little  distance.  This  necessitates  careful 
designing,  so  that  due  provision  shall  be  made  for  the  ready  transmission 
of  this  local  heat  ; granted  proper  arrangements,  however,  this  localisation 
of  heat  in  no  way  interferes  with  the  perfectly  efficient  working  of  coke- 
fired  ovens,  it  in  fact  constitutes  an  advantage. 

Although  coke  itself  burns  flamelessly,  yet  one  usually  sees  more  or 
less  pale  blue  flame  over  the  surface  of  a coke  fire.  This  is  due  to  a process 
similar  to  that  which  is  utilised  in  a producer  (see  paragraph  706)  and  arises 
from  the  formation  and  subsequent  combustion  of  carbon  monoxide,  accord- 
ing to  the  following  equations.  The  air,  in  passing  up  through  the  red-hot 
coke  of  the  fire,  forms  carbon  monoxide  thus  : — 

2C  -f  O2  = 2CO. 

Carbon.  Oxygen.  Carbon  Monoxide. 

The  gas  rises  to  the  surface,  and  there,  on  meeting  with  excess  of  air, 
undergoes  combustion,  thus  : — 

2CO  +02  = 2CO2. 

Carbon  Monoxide.  Oxygen.  Carbon  Dioxide. 

In  this  way  the  production  of  carbon  monoxide  indirectly  causes  a flame 
combustion  from  coke,  and  thus  produces  heat  in  such  a form  as  to  be  more 
readily  conveyed  away,  so  far  as  the  flames  will  reach,  from  the  furnace  into 
the  flues.  But  unless  complete  combustion  of  the  carbon  monoxide  occurs, 
there  is  a very  serious  loss  of  heat.  This  is  readily  seen  by  studying  the 
thermal  effect  of  the  burning  of  carbon  and  carbon  monoxide  respectively. 
One  gram  of  the  former  evolves  during  combustion  8,080  heat  units,  while  the 
same  quantity  of  the  latter  produces  2,634  heat  units.  From  the  equations 
above  given  it  is  readily  calculated  that  I gram  of  carbon  produces  2-33 

XX 


674 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


grams  of  carbon  monoxide.  And  further,  this  quantity  of  carbon  monoxide 
must  produce  in  burning 

2*33  X 2,634  = 6,146  heat  units. 

But  as  the  gram  of  carbon  only  evolves  8,080  heat  units,  we  have  8,080 
— 6,146  = 1,934  heat  units  produced  in  the  burning  of  1 gram  of  carbon  to 
monoxide. 

Heat  Units. 

Summing  up  : — 

Heat  produced  by  1 gram  of  carbon  burning  to  monoxide  . . 1,934 

Heat  produced  by  the  combustion  of  the  carbon  monoxide 

yielded  by  1 gram  of  carbon  . . . . . . ..  6,146 

Total 8,080 

Wliatever  quantity  of  carbon  monoxide,  therefore,  that  escapes  combustion, 
means  a loss  of  over  three-quarters  of  the  heat -producing  power  of  the  carbon 
it  contains.  To  prevent  this  loss,  air  should  gain  access  to  the  coke  gases 
after  they  leave  the  coke.  In  practice  this  end  is  sometimes  attained  by 
letting  the  furnace  doors  be  slightly  open — it  is  possible,  however,  by  having 
the  opening  too  large,  not  only  to  cut  oh  the  draught  from  the  fire,  but  also 
to  absolutely  cool  the  oven  by  the  admission  of  excess  of  cold  air  into  the 
fiues.  Theoretically,  the  right  thing  might  appear  to  be  to  keep  the  furnace 
closely  shut,  and  thus  favour  the  production  of  carbon  monoxide,  providing 
for  its  combustion,  beyond  the  fire,  by  admitting  air  on  the  flue  side  of  the 
“ bridge  ” or  back  wall  of  the  furnace.  Such  an  opening  would  need  to  be 
regulated  so  as  to  admit  the  exact  quantity  of  air  with  the  utmost  nicety,  as 
too  little  would  mean  imperfect  combustion,  and  too  much  a direct  cooling 
of  the  oven.  In  practice  there  would  be  considerable  difficulty  in  carrying 
out  this  idea. 

Not  only  among  those  in  charge  of  ovens,  but  also  furnace  men  generally, 
there  is  a widely-spread  opinion  that  the  admission  of  steam  between  the 
firebars  into  the  fire  is  greatly  advantageous.  To  such  an  extent  is  this 
view  held,  that  firebars  have  been  patented  and  used  in  boilers,  which  are 
made  hollow  and  perforated  for  the  admission  of  steam  upwards  into  the 
furnace.  From  extensive  experiments  that  have  been  made  by  large  steam 
users,  and  which  have  come  under  the  authors’  notice,  they  are  assured  that 
a distinct  saving  of  fuel  is  gained  when  measured  by  that  most  crucial  of 
all  tests,  a three  months’  fuel  bill.  In  these  tests  the  only  difference  made 
was  that  steam-admitting  bars  were  substituted  for  the  ordinary  solid  fire- 
bars. Furnace  men  obtain,  roughly,  the  same  effect  by  placing  vessels 
of  water  in  the  ashpit,  by  the  evaporation  of  which  a supply  of  steam  is 
produced. 

The  advantages  claimed  are  (1)  comparative  absence  of  clinker  forma- 
tion, (2)  longer  life  of  firebars,  (3)  saving  in  fuel.  Undoubtedly  claims 
1 and  2 are  correct,  especially  in  cases  where  the  fire  is  required  to  be 
maintained  at  very  bright  or  white  heat. 

Clinkers  are  due  to  oxidation  of  the  iron  of  the  bars,  and  subsequent  fusion 
of  such  oxide  into  a slag,  by  combination  with  siliceous  matter  from  the 
coke.  So  far  as  steam  helps  to  avoid  clinkering,  it  is  probably  due  to  its 
exercising  a local  cooling  effect  on  the  bars.  If  clinkers  are  avoided,  there 
is  necessarily  a clearer  fire,  and  as  a necessary  consequence  a better  draught, 
as  the  air  finds  its  way  through  more  readily.  Evenly  distributed  draught 
tends  to  prevent  the  formation  of  clinkers,  and  the  absence  of  clinkers  helps 
the  draught,  so  that  each  of  these  reacts  favourably  on  the  other. 

The  third  claim  of  saving  of  fuel  requires  careful  examination.  It  will 
be  best  first  to  deal  with  the  chemical  changes  produced  by  the  passage  of 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  675 


steam  over  red-hot  coke  : carbon  monoxide  and  liydrogen  are  evolved  in 
abundance  according  to  the  following  equation  : — 

C + H2O  = CO  + H2. 

Carbon.  Water.  Carbon  Monoxide.  Hydrogen. 

Subsequently,  with  excess  of  air  we  have  : — 

CO  -f-  H2  -[-  O2  — CO2  H2O. 

Carbon  Monoxide.  Hydrogen.  Oxygen.  Carbon  Dioxide.  Water. 

It  will  be  noticed  that  the  same  quantity  of  steam  which  passes  into 
the  fire  escapes  as  such  at  the  close  of  the  combustion  processes  ; therefore 
the  steam  neither  increases  nor  diminishes  the  number  of  units  of  heat 
produced  by  the  ultimate  combustion  of  carbon  to  its  dioxide.  Any 
saving  can  only  be  due  to  the  combustion  being  to  a much  greater  extent  a 
gaseous  one  ; and,  as  has  been  before  explained,  gaseous  combustion  means 
more  ready  and  even  heat  transmission,  and  therefore  economy.  Absence 
of  clinker  and  evenly  distributed  draught  are  in  themselves  of  course  indirect 
sources  of  economy  of  fuel.  It  is  a somewhat  popular  error  that  a gain 
due  to  an  absolutely  increased  amount  of  heat  is  effected  in  this  case  by 
the  combustion  of  the  hydrogen  produced  : it  must  be  remembered,  however, 
that  precisely  the  same  quantity  of  heat  is  required  for  the  dissociation  of 
water  into  its  component  gases  as  is  set  free  by  their  subsequent  combina- 
tion. Consequently,  no  outside  heat  is  liberated  by  this  decomposition  and 
recombination  of  the  constituents  of  water. 

761.  Water  Heating. — The  problem  of  heating  water  for  a bakery 
requires  more  careful  consideration  than  it  usually  receives.  The  widely 
current  notion  that  nothing  could  be  simpler  or  better  than  a boiler  over 
the  oven  furnace  is  perhaps  not  unnatural  ; especially  bearing  in  mind  that 
such  an  arrangement  ensures  a good  supply  of  warm  water  directly  on 
commencing  work  after  a period  of  rest.  As  a matter  of  fact,  however, 
there  are  serious  objections  to  this  plan,  and  an  independent  apparatus 
must  be  recommended  as  preferable.  In  the  first  place,  it  is  vTong  to  sup- 
pose that  there  is  any  saving  in  fuel  by  having  a boiler  over  the  furnace  ; 
assuming  of  course  that  in  comparing  such  an  arrangement  with  an  inde- 
pendent heater  both  are  properly  constructed.  Nature  never  gives  anything 
for  nothing,  and  water  cannot  be  heated  in  an  oven  boiler  without  a corre- 
sponding amount  of  fuel.  There  are  of  course  ovens  which  part  with  their 
waste  products  of  combustion  at  so  high  a temperature  that  they  can  be 
utilised  for  heating  water  in  adequate  quantities  ; but  these  cannot  be  here 
considered  as  we  are  dealing  with  modern  ovens,  which,  if  properly  con- 
structed, do  not  waste  heat  to  this  extent.  In  the  second  place,  it  must 
always  be  remembered  that  a boiler  constitutes  a local  demand  for  heat,  at 
such  times  especially  when  much  hot  water  is  drawn  ofi,  and  this  necessarily 
tends  to  rob  the  oven  of  heat  in  an  uneven  manner,  besides  checking  the 
temperature  generally  at  times  which  bear  no  relation  whatever  to  the 
legitimate  functions  of  an  oven.  Further,  a boiler  buried  in  brickwork 
is  much  subject  to  deterioration,  while  being  at  the  game  time  inaccessible 
to  inspection  ; the  result  is  therefore  usually  that  the  time  comes  when 
it  gives  out  without  warning,  drowns  the  fire  and  spoils  the  bread  by  interfer- 
ing with  the  baking,  to  say  nothing  of  the  inconvenience  caused  and  the 
probable  disturbance  of  work  while  repairs  and  renewals  are  effected. 

Excellent  independent  heaters  are  now  available,  and  a very  good  type 
is  illustrated  in  Fig.  93  (Perkins’  patent).  The  boiler  proper,  consisting  of 
a cylindrical  vessel,  wuth  a domed  lid  which  is  removable,  will  be  seen  to  be 
mounted  upon  a cyhndrical  furnace.  Perkins’  tubes,  arranged  in  a circle, 
pierce  the  bottom  or  tube  plate  of  the  boiler,  and  convey  the  heat  from  the 


676 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


fire,  which  lies  within  the  basket  of  pipes  formed  by  the  tubes,  to  the  water 
above.  The  fire  therefore  lies  on  a small  circular  fire-grate,  and  is  walled 

in  on  all  sides  by  the  vertical 
tubes.  Thus  no  fii^ebrick  lining 
is  necessary,  and  renewals  are 
confined  to  the  fire-grate,  a very 
small  affair  ; whereas  the  boiler 
top  can  be  readily  lifted  for  the 
removal  of  scale.  This  scale  can 
only  form  on  the  tubes  as  these 
constitute  the  only  heating  sur- 
face for  the  water,  and  owing  to 
the  fact  that  expansion  and  con- 
traction of  the  tubes  takes  place, 
the  brittle  scale  automatically 
chips  off  as  soon  as  it  has  accu- 
mulated to  any  appreciable 
thickness  and  collects  at  the 
bottom  of  the  boiler  ready  for 
removal. 

The  boiler  must  always  be 
kept  full  of  water,  and  this  is 
readily  assured  by  a supply  being 
provided  by  means  of  a ball- 
cock  supply  tank  (as  shown  in 
illustration)  under  a sufficient 
head  to  drive  the  water  to  the 
highest  point  at  which  it  is  de- 
sired to  draw  off. 

Before  leaving  this  subject 
it  is  necessary  to  point  out  the 
importance  of  always  selecting 
materials  suitable  to  the  nature 
of  the  local  water  supply.  Hard 
waters  are  usually  neutral  to 
galvanised  surfaces,  and  in  all 
such  cases  therefore  galvanised 
pipes  and  boilers  meet  all  prac- 
tical requirements.  Naturally, 
Fig.  93.  Water  Heater.  hard  waters  deposit  the  greatest 

amount  of  scale,  and  the  appara- 
tus described  above  is  then  the  best,  as  no  trouble  will  ensue  so  long  as  the 
scale  deposited  at  the  bottom  of  the  boiler  is  periodically  cleaned  out.  Soft 
waters,  especially  moor  waters  derived  from  areas  with  large  deposits  of 
peat,  corrode  iron  and  steel  very  rapidly,  especially  when  hot  ; and  gal- 
vanising also  proves  no  protection  in  such  cases.  To  meet  these  conditions, 
the  independent  heaters  are  supplied  in  copper,  as  regards  all  surfaces  which 
come  in  contact  with  the  water,  or  to  avoid  undue  expense,  with  copper- 
coated  surfaces.  As  entire  destruction  through  pitting  and  corrosion  may 
take  place  in  so  short  a time  as  12  or  15  months  where  galvanised  iron  or 
steel  are  used,  the  importance  of  this  point  will  be  appreciated. 


762.  Complete  Automatic  Bread  Bakeries. — Before  leaving  the  subject 
of  bakery  equipment  it  may  be  of  interest  shortly  to  refer  to  bakeries  which 
dispense  entirely  with  skilled  labour  ; excepting  always,  of  course,  the 
need  for  good  judgment  and  expert  knowledge  required  in  making  doughs 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  677 


by  the  aid  of  the  machines  and  regulating  properly  its  subsequent  growth 
and  development.  Such  bakeries  are  by  no  means  beyond  the  range  of 
practical  politics ; there  is,  in  fact,  no  reason  why  they  should  not  at  once 
come  into  everyday  use,  provided  that  the  output  required  is  sufficiently 
large  (say  500  sacks  per  week  and  upwards),  and  above  all  of  a uniform 
kind.  Assuming  a trade  of  500  sacks  per  week  consisting  of  nothing  but 
2 lb.  tin  bread  (or  of  the  cottage  or  coburg  varieties),  eight  men  would  be 
sufficient  to  take  the  flour  from  the  flour  store  and  deliver  the  finished  bread 
on  to  trucks  in  the  bread-room,  and  of  these  only  three  men  would  need  to 
be  bakers.  It  will  be  clear  that  the  cost  of  production  would  thus  be  brought 
down  to  a minimum,  and  as  the  baked  bread  is  discharged  into  the  bread- 
room  by  the  automatic  oven,  transportation  throughout  the  whole  process 
is  carried  out  by  mechanical  means.  The  authors  have  studied  this  scheme 
carefully  and  believe  in  its  entire  practicability. 

763.  Bashing  Machine  for  Irish  Loaves. — This  appliance  is  employed 
for  automatically  dealing  with  the  loaves  as  they  come  from  the  finishing 
moulder  (paragraph  741)  in  the  case  of  Irish  batch  bread.  As  a useful 
appliance  suitable  for  the  considerable  portion  of  Ireland,  in  which  the 
local  loaf  is  of  the  type  known  as  “ close  set  or  “ batch  bread,  a 
description  of  this  machine  (Parkinson’s  patent,  Messrs.  Joseph  Baker 
& Sons,  Ltd.)  follows.  Although  not  applicable  to  bakeries  in  general, 
the  machine  is  typical  of  the  modern  development  in  the  direction 
of  j replacing  manual  labour  involving  personal  contact  with  the  bread 
as  far  as  at  all  possible.  The  illustration.  Fig.  94,  shows  the  feeding  end 


Fig.  94.  Bashing  Machine  for  Irish  Loaves. 

'of  the  machine  to  the  left.  A conveyor  from  the  finishing  moulder  is 
arranged  to  run  across  the  feeding  end  of  the  basher,  parallel  to  the  axis 
of  the  roller  supporting  the  travelling  band  A.  The  attendant  takes 
the  loaves  from  the  conveyor  and  places  them  against  the  spacer  B, 
which  is  timed  to  operate  intermittently  at  a speed  corresponding  to  that 
of  the  moulder.  After  the  row  of  loaves  has  been  deposited  against  the 
■spacer,  this  latter  rises  vertically  to  clear  the  loaves  and  permit  them 
to  be  carried  along  by  the  travelling  band  A,  which  also  moves  intermit- 
tently. The  loaves  travel  through  the  enclosed  space  or  tunnel  C,  thus 
being  allowed  time  to  “ recover,”  and  on  emerging  from  the  tunnel  are  sub- 


678 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


jected  to  a slight  bashing  and  centring  operation  under  the  preliminary 
basher  D.  On  reaching  the  final  basher  E the  loaves  undergo  the  final 
bashing  process,  and  are  simultaneously  stamped  with  the  name  of  the  maker 
or  his  trade-mark.  On  reaching  the  end  of  the  travelling  band  at  F, 
they  are  removed  and  set  on  the  setter  boards  ready  for  the  ovens. 

764.  Scotch  “ Chaffing  ” or  Moulding  Machine. — Another  special  adapta- 
tion to  local  requirements  is  represented  by  a machine  for  performing  the 
final  operations  required  in  “Scotch''  batch  bread  (Pointon's  patent). 
In  the  manufacture  of  Scotch  bread,  although  the  dough-making  process 
foUows  entirely  different  lines  to  those  generally  adopted  in  England,  the 
machines  used,  as  far  as  dividing,  handing-up,  and  proving  are  concerned, 
are  exactly  similar  to  those  described  in  paragraph  740  et  seq.  But  the 
final  operation  of  moulding  the  loaf  is  on  an  entirely  different  principle  to 
that  of  the  balling-up  type  so  far  referred  to.  Instead  of  working  the  dough- 
piece  up  into  a ball  shape  as  described  in  paragraph  740,  the  Scotch  practice 
demands  that  the  piece  be  pressed  out  into  a fiat  sheet,  stretched,  folded 


Fig.  95.  Scotch  Chaffing  Machine. 

over,  pressed  again,  and  finally  folded  into  an  oblong  packet  ready  to  be 
placed  on  the  setter.  These  operations  are  very  difficult  to  accomplish 
mechanically,  especially  as  they  are  of  a non-consecutive  nature,  but  would 
appear  to  be  perfectly  accomplished  by  the  machine  illustrated  in  Fig.  95. 
The  dough-pieces  upon  emerging  from  the  prover  are  fed  automatically  into 
rolls,  from  which  they  emerge  as  flat  sheets.  These  sheets  of  dough  are  picked 
up  by  the  operative  and  placed  upon  one  of  the  pallets  (A)  of  the  “ chaf- 
fer," and  carried  by  intermittently  moving  chains  over  the  “ flappers," 
shown  at  (B).  Here  the  two  ends  of  the  dough  sheet  are  turned  over  upon 
themselves,  and  upon  reaching  the  next  stage  are  pressed  and  flattened 
down  firmly.  The  next  movement  causes  the  sides  of  the  fiexible  pallet  to 
be  gradually  brought  up  and  towards  each  other,  causing  a fold  in  the  dough- 
piece  at  right  angles  to  the  last  folds  made.  Finally  the  pallet  is  drawn 


THE  MACHINE  BAKERY  AND  ITS  MANAGEMENT.  679 

through  between  two  closely  spaced  walls,  causing  the  now  uppermost 
edges  of  the  dough-piece  to  be  firmly  joined  and  pressed  together,  giving 
just  the  square-ended  oblong  packet  desired. 

It  will  be  seen  that  the  working  of  the  machine  is  ingenious,  and  although 
it  has  only  been  just  put  upon  the  market  in  time  to  be  referred  to  here,  the 
authors  believe  that  it  will  be  found  to  answer  the  requirements  which  it 
was  designed  to  meet. 

765.  Bakery  Registers. — An  almost  integral  part  of  the  economy  of  a 
machine  bakery,  and  in  fact  any  bakery  of  modern  pretensions,  is  a register  of 
particulars  of  the  making  of  each  batch  of  the  day's  work.  This  should  be 
in  book  form,  and  affords,  when  properly  kept,  a most  valuable  record  of 
work  done,  and  also  gives  the  means  of  checking  same  from  day  to  day. 
The  authors  have  had  printed  a register  in  which  the  following  is  the  heading 
of  the  day’s  work  : — 

BAKEHOUSE  REGISTER.  Temperatuee. 

Day.  Night. 

19. . . . Highest  ....  ....  . . , . 

Lowest  ....  ....  .... 

Temperature  of  bakehouse  at  time  of  setting  1st  sponge  or  dough 

There  then  follow  the  various  column  headings,  arranged  right  across 
two  pages  of  the  book,  in  the  following  order  : — Number  and  kind.  Water 
(quantity).  Temperature.  Yeast,  kind  and  quantity.  Salt.  Flour. 
Flour  temperature.  Sponge  when  set.  Temperature  when  set.  When 
taken.  Remarks.  Time  when  taken.  Water.  Temperature.  Salt. 
Flour.  Dough  temperature.  Oventime.  No.  of  Loaves.  Remarks. 

Such  a register  may  be  amplified,  simplified,  or  modified,  according  to 
the  requirements  of  any  particular  mode  of  working.  The  system  of  testing 
the  temperature  of  a sponge  when  set,  and  when  taken,  often  gives  useful 
information  as  to  its  condition.  With  any  uniform  method  of  working,  the 
amount  of  rise  in  temperature  is  very  nearly  a constant  quantity.  When 
the  rise  is  excessively  low,  the  sponge  is  likely  to  have  been  starved  or  the 
yeast  to  have  been  weak.  If,  on  the  other  hand,  there  is  an  abnormally 
high  rise,  the  fermentation  will  have  been  too  vigorous,  and  have  proceeded 
beyond  its  proper  limit.  In  either  case  a useful  diagnosis  of  the  condition 
of  the  sponge  is  afforded  at  a time  when  it  is  possible  to  take  steps  toward 
remedying  either  evil.  Subject  to  certain  limitations,  the  same  remarks 
apply  to  straight  doughs. 


CHAPTER  XXV. 


ANALYTIC  APPARATUS. 

766.  Commercial  Testing  and  Chemical  Analysis  of  Wheats  and  Flours. — 

As  a matter  of  convenience,  the  various  analytic  operations  involved  in 
the  testing  and  examination  of  wheats  and  flours  are  divided  into  two 
classes  : first,  those  which  are  more  readily  performed,  and  which  afford 
information  having  the  most  immediate  bearing  on  the  actual  value  of 
these  bodies  ; and  second,  those  determinations  which  are  more  purely 
chemical  in  their  nature.  The  operations  of  the  first  class  are  comprised 
under  the  heading  of  “ Commercial  Testing  of  Wlieats  and  Flours  ” ; their 
nature  is  such  that  they  may  be  performed  personally  either  by  the  miller 
or  baker.  The  second  series  of  tests  requires  rather  more  chemical  know- 
ledge and  experience  : they  consequently  appeal  more  particularly  to  the 
students  of  milling  and  balong  who  have  had  the  advantage  of  a course  of 
chemical  training  in  a properly  appointed  laboratory. 

A description  of  the  laboratory,  and  of  the  principal  analytic  apparatus 
used  in  weighing  and  measuring,  will  now  be  given  as  an  introduction  to 
analysis. 

767.  The  Laboratory. — ^For  the  benefit  of  any  millers  and  bakers  who 
may  wish  to  fit  up  a laboratory  for  themselves,  the  following  few  hints  as 
to  utilising  a room  for  the  purpose  are  here  inserted.  If  any  work  is  to  be 
done  beyond  the  roughest  experiments,  a balance  and  microscope  will  be 
requisite  ; these  delicate  instruments  must  be  kept  free  from  dust,  and  so 
cannot  be  exposed  to  the  ordinary  atmosphere  of  the  mill  ; they  should 
therefore  be  placed  in  either  a private  office  or  study,  and  covered  over 
when  not  in  use.  For  the  other  purposes  of  a chemical  laboratory,  almost 
an}^  room,  or  part  of  a room,  can  be  made  to  answer.  A working  bench  or 
table  should  be  fitted  in  as  good  a light  as  possible,  at  a convenient  height. 
Gas,  when  obtainable,  should  be  laid  on  to  this  bench  by  means  of  a pipe 
terminating  in  a nozzle,  over  which  a piece  of  india-rubber  tubing  can  be 
slipped.  There  should  be  near  at  hand  a drain,  over  which  is  fixed  a tap, 
with  a good  water  supply.  This  tap  should  also  have  a small  side  tap, 
Avith  nozzle  for  india-rubber  tubing,  in  order  to  lead  water  into  any  apparatus 
in  which  it  is  required.  These  are  almost  the  whole  of  the  necessary  fixings. 
There  must  of  course  be  a few  shelves  on  which  bottles  and  the  various 
apparatus  may  be  kept.  With  time  and  money  to  spare,  many  additional 
fittings  might  be  suggested.  These  can,  if  wished,  be  added  afterward. 

768.  The  Analytical  Balance. — It  is  presumed  that  the  student  before 
attempting  the  following  work,  will  have  made  himself  famihar  with  the 
simpler  chemical  apparatus  by  their  actual  use  in  the  laboratory.  Quanti- 
tative analysis,  as  its  name  implies,  is  that  species  of  analysis  by  means  of 
which  the  quantity  or  amount  of  each  ingredient  in  any  particular  body  is 
determined.  For  purposes  of  analysis,  quantity  is  measured  and  expressed 
either  by  weight  or  by  volume.  Accordingly,  the  chemist  first  of  all  requires 
some  accurate  means  of  determining  with  exactness  both  weight  and  volume. 

For  purposes  of  weighing,  an^accurate  balance  and  set  of  weights  are 

680 


ANALYTIC  APPARATUS 


681 


necessary.  Of  these  there  should  be  in  a laboratory  at  least  three  of  dif- 
ferent degrees  of  sensibility.  Taking  the  most  delicate  first,  let  us  describe 
what  may  be  termed  the  “analytic  balance  proper.''  This  instrument 
requires  to  be  made  with  the  utmost  care  and  accuracy,  and  is  illustrated 
in  Fig.  96.  The  speciality  of  this  particular  variety  is  that  the  beam  is 
very  short  ; it  is  claimed  for  it  that,  as  a result,  the  delicacy  of  the  balance 
is  increased,  while  the  time  in  which  a weighing  is  performed  is  lessened. 
On  referring  to  the  figure  it  will  be  noticed  that  the  balance  is  enclosed 


in  a case  ; the  bottom  of  this  consists  of  a stout  slab  of  glass,  fixed  on  levelling 
screws.  The  front,  back,  and  sides  of  the  case  are  glazed  ; and  all  open, 
the  front  and  back  by  shding  up,  the  two  sides  on  hinges,  as  doors.  The 
beam  is  suspended  on  a pillar,  which  in  turn  is  screwed  down  to  the  bottom 
of  the  case.  The  beam  carries  at  its  centre  a knife-edge  made  of  agate  ; 
this  rests  on  a plane  of  the  same  material  ; on  each  end  of  the  beam  there 
are  similar  knife-edges,  and  from  these  depend  the  scale  pans.  Wlien  the 
balance  is  not  in  use,  the  beam,  instead  of  bearing  its  weight  on  the^knife- 


682 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


edge,  rests  on  a sort  of  cradle  ; so,  too,  the  end  hooks  carrying  the  pans- 
are  likewise  supported  by  the  cradle.  Underneath  each  pan  there  is  also  a 
small  support  on  which  the  pan  rests  until  it  is  required  to  set  the  balance 
in  action.  In  the  centre  of  the  front  of  the  balance,  and  immediately  under- 
neath the  glass  base,  is  fixed  a large  brass  milled  head  ; this,  on  being  slowly 
turned  by  the  operator,  first  lowers  the  supports  from  beneath  the  pans, 
then  drops  one  portion  of  the  cradle,  and  so  suspends  each  scale  pan  from 
the  terminal  knife-edges  of  the  beam,  and  next  lowers  the  central  knife-edge 
on  to  its  agate  plane,  and  permits  the  balance  to  swing.  On  turning  the 
milled  head  back  again,  the  opposite  of  these  movements  takes  place  in 
reverse  order,  and  each  knife-edge  is  gently  lifted  from  the  agate  plane. 
The  object  of  this  is  to  prevent  wear  of  the  edges  by  their  being  continually 
in  contact,  particularly  as  a balance  would  soon  be  seriously  injured  by  the 
jarring  caused  to  knife-edges  and  planes  by  putting  on  and  removing  weights 
while  these  were  in  contact.  It  must  be  borne  in  mind,  as  a golden  rule  of 
weighing,  that  nothing  must  be  added  to  or  removed  from  either  pan  of  the  balance 
when  the  instrument  is  in  motion.  In  order  to  show  the  movement  of  the  beam, 
there  is  a long  index  finger  descending  from  its  centre  and  moving  in  front 
of  an  ivory  scale  at  the  bottom  of  the  pillar.  A description  of  the  mechan- 
ism employed  to  effect  these  various  movements  is  unnecessary,  as  they  can 
readily  be  understood  by  a few  minutes’  careful  inspection  of  the  instrument 
itseK.  Some  other  attachments  of  the  balance  will  be  better  understood  when 
we  come  to  describe  the  operation  of  weighing.  If  a student  is  working  in 
laboratory  under  the  direction  of  a teacher,  he  will  find  balances  there,  and 
already  properly  adjusted  ; in  case  that  he  happens  to  have  purchased  one  for 
his  private  use,  all  the  adjustments  will  have  been  made  by  the  maker,  and 
should  not  be  interfered  with  by  him  unless  he  is  thoroughly  acquainted 
with  the  mechanism  of  a balance.  It  should  always  be  borne  in  mind  that 
a balance  must  on  no  account  be  altered  or  re-adjusted  except  by  some 
responsible  person  ; there  may  be  several  persons  working  with  the  balance, 
and  the  one,  by  altering  it,  and  possibly  setting  it  wTong,  may  upset  the 
work  of  all  the  others.  Suppose  a student  has  procured  a balance  for  his 
o^vn  private  use,  let  him  place  it  in  its  permanent  position,  which  should  be 
on  a stout  bench  or  table  in  a dry  room,  and  at  a height  convenient  for 
weighing  when  sitting  down.  The  light  should,  if  possible,  be  from  a window 
behind  the  balance  ; that  is,  the  balance  should  be  so  placed  that  the  opera- 
tor is  facing  the  light,  which  should  not  be  glaring,  while  it  should  be  good. 
Occasionally,  in  a balance  so  placed,  the  ivory  scale  at  the  base  of  the  pillar 
is  in  such  deep  shadow  as  to  be  scarcely  readable.  This  may  be  remedied 
by  folding  a piece  of  white  cardboard  at  right  angles  and  placing  it  in  front 
of  the  scale.  It  will  be  below  the  range  of  the  eye,  and  acting  as  a reflector 
will  sufficiently  illuminate  the  scale.  A light  coming  from  a high  window 
behind  the  operator  also  answers,  but  a strong  light  from  either  side  is  not 
suitable  for  weighing.  The  first  thing  to  do  is  to  get  the  pillar  of  the  balance 
vertical.  In  the  balance,  a plummet  hangs  from  the  back  of  the  pilUr, 
immediately  over  a corresponding  index  point  on  the  base  ; the  two  levelling 
screws  in  front  of  the  balance  must  be  turned  in  one  direction  or  the  other 
until  the  plummet  is  directly  over  the  index  point  ; the  base  of  the  balance 
will  then  be  horizontal.  In  the  next  place  carefully  dust  the  beam  and 
the  pans  with  a camel’s  hair  brush.  Then  turn  the  milled  head  which 
actuates  the  balance,  and  allow  the  beam  to  vibrate  ; it  will  most  likely 
swing  one  way  or  the  other  immediately  the  beam  is  liberated,  but  if  not, 
open  the  right-hand  side  door  and  waft  a very  gentle  current  of  air  down  on 
the  one  pan  with  the  hand.  Close  the  door  again,  and  watch  the  vibrations 
of  the  index  finger  ; it  should  be  explained  that  all  the  sides  of  the  case 
must  be  kept  closed  as  much  as  possible  during  the  operation  of  weighing. 


ANALYTIC  APPARATUS. 


683 


The  little  ivory  scale  has  its  zero  in  the  centre,  the  divisions  count  each  way 
from  it,  and  are  usually  ten  in  number  on  each  side.  Should  the  balance  be 
correctly  adjusted,  the  index  finger  will  swing  the  same  number  of  degrees 
each  side  of  the  zero,  and  after  a time,  as  each  vibration  becomes  shorter, 
will  come  to  rest  over  the  middle  of  the  scale.  Strictly  speaking,  the  dis- 
tance travelled  on  each  side  must  be  slightly  less  than  that  of  the  other  ; 
thus,  supposing  the  index  travelled  to  9 on  the  left  hand,  it  would,  when  the 
balance  is  correct,  swing  slightly  less  than  9 to  the  right,  say  8-9,  and  then 
back  to  8-8  on  the  left.  With  a good  balance  this  diminution  is  so  little 
for  one  or  two  vibrations  that  practically  we  may  say  that  it  should  swing 
equally  on  both  sides. 

Such  a balance  as  that  described  is  capable  of  weighing  to  the  tenth  of 
a milligram,  with  a weight  of  two  hundred  grams  in  the  pan.  In  addition 
to  this  instrument  a coarser  balance  is  also  necessary  ; this  should  be  capable 
of  carrying  a kilogram,  and  weighing  to  the  hundredth  of  a gram.  Bal- 
ances of  this  latter  kind  cost  from  thirty  shillings  to  two  pounds,  and  are 
similar  in  principle  to  that  already  described. 

769.  Adjustment  of  Balance. — In  case  when  testing  the  balance  the 
index  does  not  swing  to  the  same  distance  on  either  side  of  the  zero  of  the 
scale,  first  of  all  again  dust  the  balance  most  carefully,  and  test  once  more. 
In  the  event  of  this  not  removing  the  error,  the  beam  must  be  re-adjusted  ; 
there  will  be  seen  two  little  balls,  one  on  either  side  of  the  top  of  the  beam, 
and  running  on  two  slender  horizontal  screws  attached  to  the  beam — on  the 
side  which  is  the  lighter,  screw  the  ball  very  slightly  from  the  centre  of  the 
beam,  and  again  test.  Repeat  this  until  the  two  sides  of  the  beam  exactly 
counterpoise  each  other.  Wlien  once  adjusted,  a balance,  if  kept  clean, 
needs  no  alteration  for  a considerable  time,  providing  always  that  it  be 
carefully  and  delicately  handled.  In  different  makes  of  balance  the  modes 
of  adjustment  vary  ; the  maker  will,  however,  in  every  case  either  give 
directions  or  see  to  the  proper  adjustment  of  the  instrument  before  it  leaves 
his  hands  in  case  of  its  being  a new  one.  For  a very  clearly  vTitten  and 
most  interesting  chapter  on  the  mechanical  principles  and  management 
of  the  balance,  the  student  is  referred  to  Thorpe’s  Quantitative  Analysis, 
published  by  Longmans  & Co. 

770.  Analytic  Weights. — After  the  balance,  the  next  thing  required  by 
the  chemical  student  is  an  accurate  set  of  weights.  As  a rule  the  chemist 
returns  his  results  in  pereentages  ; it  is  not  therefore  of  very  great  impor- 
tance to  him,  from  that  point  of  view,  what  unit  of  weight  he  adopts.  In 
England,  ehemists  either  use  grain  weights  or  else  those  of  the  French  metric 
system.  Wlien  grain  weights  are  employed,  the  set  contains  pieces  varying 
from  the  hundredth  of  a grain  to  1,000  grains.  From  its  much  greater 
simplicity,  weights  of  the  metric  system  are  now  used  to  a much  greater 
extent  than  grain  weights.  Not  only  is  there  this  advantage  of  greater 
simplicity,  but,  in  addition,  they  have  become  the  international  system 
for  scientific  purposes  ; for  this  reason,  as  well,  it  is  highly  advisable  that 
all  chemists  and  students  of  chemistry  should  learn  to  work  with  these 
weights.  Whatever  weights  are  employed  a few  very  simple  factors  suffice 
to  convert  those  of  the  one  denomination  into  those  of  the  other.  In 
Chapter  I.  is  given  a table  of  the  most  important  metric  weights  and 
measures,  together  with  their  English  equivalents. 

The  set  of  weights  employed  for  analytical  purposes  must  be  of  the 
greatest  possible  accuracy.  They  usually  range  from  50  grams  to  a milli- 
gram. The  heavier  weights  are  made  of  brass  and  then  electro -gilded  ; 
the  fractions  of  a gram  are  made  of  stout  platinum  foil.  In  shape,  the  brass 
weights  are  made  slightly  conical,  and  are  each  fitted  with  a small  handle 


684 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


at  the  top,  by  which  they  must  be  lifted  ; for  the  same  purpose  each  of  the 
platinum  weights  has  the  top  right-hand  corner  bent  at  right  angles  to  the 
weight.  These  weights  are  arranged  in  a box,  each  being  placed  in  a 
separate  compartment,  those  for  the  gram  weights  being  lined  with  velvet  ; 
the  smaller  weights  are  further  protected  by  an  accurately  fitting  cover  of 
glass.  For  the  purpose  of  lifting  the  weights  a pair  of  forceps  is  provided  ; 
this  has  its  place  in  the  box.  Analytic  weights  must  on  no  account  be  touched 
with  the  fingers.  Most  sets  of  analytic  weights  contain  the  following  pieces 
arranged  in  the  box  in  the  order  shown  below  ; — 


50 

20 

10 

10 

5 

1 

1 

1 

2 

0-5 

0 001) 

0-2 

0-1 

0-1 

005 

Rider. 

0-001 1 
0-001  j 

0-005 

0-01 

0-01 

0-02 

The  student  will  require  to  learn,  not  only  the  denomination  of  each 
weight,  but  also  its  place  in  the  box.  He  must  be  quite  as  well  able  to  read 
the  weights  he  has  placed  in  the  balance  pan  from  the  empty  spaces  as 
from  the  weights  themselves.  As  soon  as  the  weights  are  done  with  they 
should  always  be  returned  to  the  box  ; this  should  be  further  protected 
by  being  kept  in  a case  made  for  it  of  wash-leather.  The  accuracy  of  all 
analysis  depends  on  that  of  the  weights  ; too  great  care  cannot,  therefore, 
be  taken  to  preserve  them  from  injury. 

In  giving  the  denominations  of  the  weights  above  there  is  a place  marked 
“ Rider  ''  ; the  nature  and  use  of  this  particular  w'eight  remains  to  be 
explained. 

The  arrangement  of  the  weights,  as  shown  in  Fig.  97,  corresponds  with 
the  table  just  given  of  their  value.  Special  attention  must  be  directed  to 
the  “ Rider,''  which  is  drawn  to  its  full  size  at  A. 

The  student  must  now 
refer  again  for  a moment 
to  the  figure  of  the  balance 
previously  given  ; he  wdll 
there  notice,  at  the  top  right- 
hand  corner,  a milled  head  ; 
this  actuates  a rod,  at  the 
other  end  of  which,  from  a 
little  hook,  depends  the 
rider,  as  showTi  just  over  the 
left-hand  pan.  From  end 
to  end  of  the  beam  itself 
there  also  runs  a graduated 
scale  ; this  scale  is  divided 
into  twenty  equal  parts,  the  centre  is  marked  zero,  and  the  other 
graduations  numbered  I— 10  from  the  centre  towards  each  end.  Each  ok 
these  units  is  still  further  subdivided  into  5 or  10  equal  parts.  This  scale 
is  the  exact  length  of  the  beam,  measured  from  one  to  the  other  of  the 
terminal  knife-edges.  An  inspection  of  the  balance  itself  shows  immediately 
that  by  means  of  the  milled  head  and  rod  attached  thereto,  the  rider  can 
be  placed  astride  the  scale  at  any  part  of  its  length.  The  weight  of  the  rider 
is  one  centigram,  consequently,  if  placed  in  the  pan  of  the  balance,  or  at  10, 
the  extremity  of  the  scale,  the  effective  weight  of  the  rider  is  the  same  as 
its  absolute  weight.  But  if  it  be  placed  somewhere  intermediate  between 
the  centre  and  end  of  the  beam,  its  effective  weight  is  between  0 and  1 centi- 
gram. The  effective  weight  is  governed  by  the  well-known  principle  of 


Fig.  97. — Box  of  Analytic  Weights. 


ANALYTIC  APPARATUS. 


685 


the  lever,  namely,  that  the  force  exerted  by  any  weight  is  directly  pro- 
portional to  its  distance  from  the  fulcrum.  As  each  side  of  the  beam  is 
divided  into  10  equal  parts,  the  weight  of  the  rider  at  each  division  is  the 
number  of  tenths  it  is  from  the  centre  : thus,  at  5,  its  weight  is  equal  to 
of  a centigram,  or  5 milligrams,  and  so  for  each  graduation  and  intermediate 
fraction.  The  employment  of  the  rider  in  actual  weighing  will  be  gathered 
from  the  next  paragraph. 


771.  Operation  of  Weighing. — In  performing  this  operation,  let  it  be 
supposed  that  the  student  has  balance  and  weights  in  readiness,  and  requires 
to  obtain  the  weight  of  some  particular  piece  of  apparatus  ; this,  whatever 
it  is,  must  be  thoroughly  cleaned  and  dried,  and  then  placed  on  the  left- 
hand  pan  of  the  balance.  For  this  purpose  the  front  of  the  case  of  the 
balance  may  be  raised,  or  if  working  with  a balance  with  side-doors,  that  on 
the  left  hand  may  be  opened.  Two  rules  of  weighing  are  : 1st,  always  place 
substance  in  left-hand  pan,  and  weights  in  the  right  ; 2nd,  keep  the  doors  of  the 
balance  case  closed  whenever  possible.  Let  the  weight  of  the  piece  of  apparatus 
in  question,  say  a crucible,  be  17*8954  grams  ; by  the  following  method 
this  figure  will  have  been  ascertained.  First  take  the  20  gram  weight  from 
the  box  by  means  of  the  forceps,  and  place  it  in  the  right-hand  pan,  release 
the  beam  from  its  support  by  turning  the  milled  head  : notice  whether 
the  left  or  right-hand  pan  of  the  balance  is  the  heavier.  In  this  case  the 
weight  will  be  too  much,  and  the^index  finger  will  swing  to  the  left.  Bring 
the  balance  to  rest  by  turning  the  milled  head,  and  take  out  the  20  gram 
weight,  and  replace  it  by  the  10  gram,  try  whether  sufficient — not  enough, 
add  5 grams — still  too  little,  add  2 — too  little,  add  I — too  much.  Do  not 
forget  that  every  time  before  a weight  is  added  or  removed  the  beam  must 
be  brought  to  rest  on  its  supports  ; this  is  always  to  be  done  gently  and 
carefully.  After  the  addition  of  each  weight  the  beam  will  have  swung 
over  more  slowly  ; with  the  18  grams  in  the  pan  the  swing  of  the  index  to  the 
left  will  have  been  much  slower  than  any  preceding  it,  showing  that  the 
actual  weight  of  the  crucible  is  being  closely  approached.  Return  the  1 
gram  weight  to  its  place  in  the  box,  and  next  try  0*5  gram — not  enough, 
add  0*2 — not  enough,  add  0*1 — not  enough,  add  0*1 — too  much.  Replace 
the  0*1  and  try  0*05 — not  enough,  add  0*02 — not  enough,  add  0*01 — not 
enough,  add  0*01 — not  enough.  The  weight  has  now  been  ascertained 
within  a centigram,  because  the  addition  of  another  centigram  would  bring 
the  weight  up  to  the  0*1  gram,  which  has  already  been  tried  and  found  too 
much.  The  conclusion  of  the  weighing  should  now  be  done  with  the  rider. 
Place  the  rider  on  the  5 on  the  right-hand  end  of  the  beam,  lower  the  sup- 
ports, cause  the  beam  to  vibrate,  and  shut  the  door  of  the  case.  If  necessary, 
waft  with  the  hand^a  gentle  current  of  air  on  to  one  of  the  pans  in  order  to 
set  the  beam  in  motion.  Count  the  number  of  graduations  which  the  index 
moves  on  either  side  of  the  zero  ; it  will  be  found  to  vibrate  slightly  more 
to  the  right  than  to  the  left.  Next  try  the  rider  on  the  6th  division  ; this 
is  found  too  much.  Try  the  rider  at  intermediate  distances  until  it  is  found 
that  the  beam  swings  through  an  equal  number  of  graduations  on  either  side 
of  the  zero  scale  ; the  weight  in  each  pan  is  then  the  same.  Let  us  now  see 
how  the  weights  are  to  be  read  ; this  should  be  done  from  the  box,  reading 
the  empty  spaces.  In  the  case  in  point  these  are  10  + 5 + 2 = 17. 
Against  “ weight  of  crucible,""  write  this  number  in  the  note  book.  Next 
read  off  the  decigram  weights  ; there  are  empty,  0*5  + 0*2  + 0*1  = 0*8  ; 
write  *8  after  the  17.  The  centigrams  come  next,  they  are  0*05  + 0*02  + 
0*01  + 0*01  =0*09  ; WTite  9 after  the  8.  The  milligrams  and  fractions 
of  a milligram  are  to  read  off  from  the  rider  ; in  the  present  instance  the 


686 


THE  TECHNOLOGY  OF  BREAD-MAKING 


rider  stands  at  0*0054  grams,  54  must  therefore  be  written  after  the  9. 
The  whole  figure  will  then  read  : — 

“Weight  of  crucible  = 17*8954  grams.” 

Having  thus  read  the  weight  from  the  empty  spaces  in  the  box,  next 
take  the  weights  out  and  check  the  reading  off  as  they  are  returned  to  their 
places.  This  double  reading  greatly  reduces  the  chances  of  error  in  record- 
ing the  weight  of  the  substance.  After  a little  experience  in  weighing,  and 
thus  getting  to  know  the  capacity  of  the  particular  balance  used,  the  student 
should  test  his  balance  in  order  to  ascertain  the  value  of  each  graduation 
of  the  index  scale.  To  do  this  put  the  rider  on  the  5 milligram  mark,  cause 
the  beam  to  vibrate,  and  notice  how  far  on  either  side  of  the  zero  it  swings. 
Alter  the  position  of  the  rider  until  the  beam  swings  from  the  zero  to  the 
10  on  the  one  side  ; note  the  position  of  the  rider.  Suppose  it  to  be  on  the 

5,  then  10  divisions  of  the 
index  scale  = 5 milligrams, 
and  1 division  = 0*5  milli- 
gram. This  value  will  only 
b be  approximately  the  same 

when  the  pans  are  loaded, 
but  still  sufficiently  near  to 
save  time  in  the  weighing. 
Thus,  suppose  3*5  grams 
have  been  placed  in  the'pan, 
and  the  index  vibrate  10  to 
the  right  and  8 to  the  left, 
there  is  no  need  to  success- 
ively try  the  0*2  and  other 
weights  down  to  the  0*01, 
but  the  rider  may  at  once 
be  put  on  the  1 milligram 
mark,  and  will  be  found  to 
be  very  nearly  in  its  right 
place.  One  or  two  trials 
v'ill  then  find  the  exact 
weight.  The  1 is  found 
in  this  case  by  taking  half 
the  difference  between  the 
vibrations  on  each  side  ; 
this  will  often  apply,  even 

Fig.  98. — Vabious  Measubing  Appabatus.  tnougn  the  balance  does 

not  swing  quite  to  the 
ten  ; thus,  the  distances  indicated  might  be  9 and  7.  The  beam  should, 
however,  be  always  caused  to  swing  freely,  as  it  makes  a long  oscillation 
in  the  same  time  as  a short  one.  It  will  be  noticed  that,  so  far,  the  right- 
hand  side  only  of  the  rider  scale  has  been  referred  to  ; the  left  is  also  fre- 
quently convenient.  Supposing  that,  with  the  3*5  grams  just  mentioned, 
tlie  index  had  vibrated  the  tw'o  extra  degrees  to  the  left,  this  would  have 
indicated  that  the  substance  weighed  about  1 milligram  less  than  3*5  ; to 
])ut  this  weight  in  w'ould  require  the  removal  of  the  0*5,  and  the  placing  of 
tlie  0*2,  0*1, 0*1,  0*05,  0*02,  0*01,  0*01,  on  the  pan,  and  the  rider  at  the  9 milli- 
gram mark.  The  same  result  is  produced  by  placing  the  rider  on  the  1 milli- 
gram mark  to  the  left.  When  the  rider  is  on  the  left  side  of  the  beam,  the 
weight  it  represents  must  be  subtracted  from  that  in  the  right-hand  pan. 

Tlie  operation  of  weighing  has  been  described  at  full  length,  because 
it  is  the  foundation  of  all  quantitative  analysis  ; these  operations  are,  how- 


ANALYTIC  APPARATUS. 


687 


ever,  mucli  shorter  in  practice  than  they  appear  on  paper.  The  genuine 
chemical  student  will  never  forget  that  his  balance  should  be  carefully, 
intelligently,  and  even  lovingly  used. 

In  addition  to  the  two  balances  and  set  of  weights  already  described, 
the  student  will  need  another  set  of  weights,  ranging  from  10  milligrams  to 
200  grams. 

772.  Apparatus  Employed  for  Measuring  Purposes. — These  include 
measuring  flasks,  burettes,  and  other  appliances. 


773.  Burettes  and  Floats. — Fig.  98,  on  page  686,  is  an  illustration  of 
various  forms  of  measuring  apparatus.  The  instrument  marked  a is  termed 
a burette,  and  is  used  for  the  purpose  of  accurately  measuring  small  quan- 
tities of  liquid  when  delivered.  There  is  at  the  bottom  a glass  stop-cock  ; 
the  tube  is  graduated  throughout.  The  most  useful  size  of  burette  is  that 
holding  50  c.c.  ; such  an  instrument  is  graduated  in  500  divisions  ; these 
are  numbered  at  each  c.c.,  from  the  top  downwards.  In  using  the  burette 
it  is  first  cleaned,  and  then  rinsed  with  a little  of  the  solution  with  which 
it  is  to  be  filled,  then  filled  up  almost  to  the  top.  When  a long  and  na,rrow 
tube,  such  as  a burette,  con- 
tains a liquid,  the  top  is  not 
exactly  level,  but  is  always 
shghtly  curved,  with,  in  the 
case  of  water  and  aqueous 
solutions,  the  concave  surface 
upwards.  It  is  customary,  in 
comparing  the  height  of  a 
liquid  with  the  graduation 
marks,  to  read  from  the  bottom 
of  this  curve,  or  “ meniscus,’" 
as  it  is  termed.  The  next 
thing  is  to  run  the  liquid  out 
through  the  stop -cock  until 
the  zero  mark  is  reached.  Fix 
the  burette  upright  in  the 
burette  stand,  and  place  the 
eye  level  with  the  zero  gradua- 
tion, then  turn  the  stop-cock 
carefully,  and  let  the  liquid 
run  out  until  the  bottom  of 
the  meniscus  exactly  coincides 
with  the  zero  line.  The  bur- 
ette is  generally  used  for  the 
purpose  of  running  a liquid 
change  takes  place,  then  the 
is  again  read  ofi,  and  the 


Erdmann’s 

Float. 


Burette,  with  Spring 
Clip. 


into  a solution  until  some  particular 
height  of  the  reagent  in  the  burette 
quantity  that  has  been  used  determined. 
So  when  the  change,  whatever  it  may  be,  is  complete,  again  bring  the  eye 
level  with  the  bottom  of  the  meniscus,  and  read  ofi  the  graduation  with 
which  it  coincides.  Accurate  reading  of  the  burette  is  much  assisted  by 
the  use  of  “ Erdmann’s  Float  ” ; this  little  piece  of  apparatus,  which  is 
shewn  on  this  page  (Fig.  99),  consists  of  a piece  of  glass  tubing  of  such  a 
size  as  to  be  able  to  slide  readily  up  and  down  within  the  burette.  The  tube 
is  closed  at  both  ends,  so  as  to  form  an  elongated  glass  bulb,  which  contains 
a small  quantity  of  mercury.  Around  the  float  a single  line,  a,  is  marked 
with  a diamond.  When  using  the  float  it  is  dropped  in  the  burette,  and  the 
line  around  it  brought  to  agree  with  the  zero  mark  at  starting,  and  after- 
wards the  height  is  read  from  the  line  on  the  float.  A form  of  burette  very 


688 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


convenient  for  general  use  is  that  known  as  Mohr’s  ; it  differs  slightly  in 
shape  from  that  figured  in  the  preceding  illustration.  Mohr’s  burette  is 
made  either  with  a glass  stop-cock,  or  else  with  a glass  jet  fastened  on  with 
a piece  of  india-rubber  tubing,  as  shown  in  Fig.  100.  A strong  spring  com- 
presses the  tubing,  and  so  stops  the  burette.  The  flow  of  the  hquid  is  regu- 
lated by  means  of  pressing  the  two  buttons,  shown,  between  the  finger  and 
thumb.  The  figure  shows  only  just  the  lower  end  of  the  burette.  The 
glass  stop-cocks  of  burettes  and  other  instruments  should  always  be  slightly 
greased,  so  as  to  prevent  their  sticking.  If  a burette  is  likely  to  be  put  aside 
for  some  time,  it  is  well  to  withdraw  the  stop-cock  altogether,  and  put  it 
away  separately,  or  a small  slip  of  paper  may  be  inserted  between  the  plug 
of  the  stop-cock  and  its  casing. 

774.  Pipettes. — Turning  once  more  to  Fig.  98,  there  are  two  instru- 
ments marked  h,  h ; these  are  pipettes,  and  are  used  for  delivering  a definite 
volume  of  any  liquid  ; the  capacity  of  the  two  figured  is  respectively  50 
and  100  c.c.  In  the  tube  just  above  the  bulb  there  is  a mark  (not  shown 
in  the  figure),  which  indicates  the  point  to  which  the  pipette  must  be  filled. 
When  using  the  instrument,  place  the  lower  end  in  the  liquid  to  be  meas- 
ured, and  suck  at  the  upper  until  the  liquid  rises  above  the  graduation 
mark,  then  stop  the  upper  end  with  the  tongue  ; next  quickly  substitute 
the  tip  of  the  finger  for  the  tongue,  without  allowing  the  liquid  to  run  out. 
This  requires  some  little  practice,  but  repeated  trials  overcome  any  difficulty 
at  first  experienced.  Next  raise  the  finger  very  slightly  until  the  liquid 
begins  to  run  from  the  lower  end  ; let  it  do  so  until  the  bottom  of  the  menis- 
cus coincides  with  the  graduation  mark,  then  hold  the  end  of  the  pipette 
over  the  vessel  into  which  the  liquid  is  to  be  poured,  take  away  the  finger 
and  let  the  tube  drain.  When  the  highest  degree  of  accuracy  is  required, 
the  pipette  should  always  be  emptied  in  precisely  the  same  manner.  A 
good  uniform  method  consists  in  holding  the  pipette  vertical  and  allowing 
it  to  discharge  its  contents  by  gravity.  When  the  main  stream  has  stopped, 
hold  the  instrument  in  the  same  position  until  three  drops  have  fallen,  and 
then  remove  it.  The  pipette,  if  correctly  graduated,  will  thus  deliver  the 
exact  amount  of  liquid  marked  on  it.  The  following  are  convenient  sizes 
for  pipettes  : 2,  5,  10,  20,  25,  50,  and  100  c.c.  One  10  c.c.  pipette  will  be 
required  graduated  throughout  its  whole  length,  somewhat  like  a burette  ; 
it  is,  in  fact,  used  for  very  much  the  same  purpose. 

775.  Measuring  Flasks. — The  only  other  piece  of  apparatus  that  need 
be  explained  at  present  is  the  graduated  flask,  d,  Fig.  98  ; this  has  also 
a mark  round  the  neck  showing  the  graduation  line.  The  same  remarks 
apply  to  its  use  as  those  already  made  in  reference  to  the  other  pieces  of 
measuring  apparatus. 

Other  pieces  of  apparatus  required,  with  the  methods  of  using  them,  will 
be  described  as  occasion  for  their  employment  arises. 


CHAPTER  XXVI. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS. 

776.  Wheat  Testing. — ^The  simplest  and  most  direct  commercial  tests 
that  can  be  made  on  whole  wheat  are  its  weight  per  bushel,  weight  of 
100  grains  of  average  size,  and  percentage  of  foreign  seeds,  dirt  or  other 
extraneous  matter.  Other  tests  are  best  made  on  the  finely-powdered 
whole  meal  of  the  grain. 

777.  Weight  per  Bushel. — ^This  operation  is  so  famihar  to  all  millers 
that  an  explanation  of  it  is  scarcely  necessary.  As  is  well  known,  there 
is  a special  piece  of  apparatus  sold  that  is  made  for  the  purpose.  A cheap 
and  efficient  substitute  for  this  may  easily  be  prepared  and  used  where 
a student  has  such  a balance  as  the  coarser  one  previously  described.  Get 
a coppersmith  to  make  a cylindrical  measure  about  3 in.  in  diameter 
and  3 in.  deep.  Procure  from  a dealer  in  chemical  apparatus  a counter- 
poise box  ; these  are  brass  boxes  with  lids  which  screw  on.  Put  the  empty 
measure  on  the  one  side  of  the  balance  and  the  counterpoise  on  the  other, 
fill  with  shot  until  it  exactly  balances  the  measure.  Next  fill  the  measure 
exactly  full  of  distilled  water,  level  with  the  brim,  and  again  weigh,  always 
placing  the  counterpoise  on  the  weight  pan.  The  weight  in  grams  of  the 
water  held  by  the  measure  represents  its  capacity  in  c.c.  Now  the  weight 
of  a bushel  of  water  (=  80  lbs.),  and  that  of  the  water  contained  in  the 
little  vessel,  are  always  constant ; and,  as  the  weight  of  the  water  the 
vessel  contains  is  to  the  weight  of  the  wheat  that  is  being  tested,  so  is  the 
weight  in  pounds  of  a bushel  of  water  to  that  in  pounds  of  a bushel  of  the 
wheat.  Expressing  this  in  the  usual  way  we  have — 

As  weight  of  water  held  by  vessel  : weight  of  wheat  held  : ; 80  : lbs.  per 

bushel ; 

or  X weight  of  wheat  held  weight  of  wheat  in 

weight  of  water  held  pounds  per  bushel. 

Now  for  any  particular  vessel  the  weight  of  water  it  holds  is  always  constant, 
so  that  80  in  the  upper  line,  and  the  weight  of  water  in  the  lower,  may 
be  reduced  to  a single  factor,  and  the  weight  in  pounds  per  bushel  at  once 
determined  by  multiplying  the  weight  of  grain,  held  in  the  measure,  by 
that  factor.  Suppose  that  the  capacity  of  the  vessel  is  200  c.c.,  then 
80 

=0-4  is  the  factor,  and  the  weight  of  wheat  in  grams  held  by  the 

vessel  would  simply  have  to  be  multiplied  by  that  figure.  In  taking  weights 
per  bushel  the  little  measure  should  be  carefully  filled,  and  then  struck 
level  by  means  of  a pencil  or  other  round  piece  of  wood. 

778.  Weight  of  100  Grains  . — For  this  estimation  it  is  important  that 
the  grains  selected  shall  represent  the  average  sample  : if  they  are  simply 
picked  up  one  by  one  out  of  a heap,  the  weight  is  almost  certain  to  be  in 
excess  of  the  true  average  ; for  a person  under  these  circumstances  almost 
invariably  unconsciously  selects  the  largest  grains.  To  obviate  this,  fold 
a strip  of  paper  so  as  to  form  a V-shaped  gutter  ; take  a handful  of  the 


690 


THE  TECHNOLOGY  OF  BREAD-MAKING 


wheat  and  let  it  pour  in  a small  stream  along  the  length  of  this  gutter. 
Then  commence  at  the  one  end  and  count  off  the  100  grains,  taking  each 
as  it  comes.  Weigh  on  the  pan  of  the  balance  and  enter  the  weight  in 
the  note-book. 

779.  Percentage  of  Foreign  Matter. — The  foreign  matter  in  a sample 
of  wheat  may  consist  of  other  seeds,  or  possibly  dirt  or  stony  substances. 
Wliere  it  is  only  the  former,  a portion  of  the  grain  may  be  weighed  off, 
and  foreign  seeds  separated  by  hand-picking,  and  again  weighing.  The 
methods  adopted  for  the  removal  of  dirt  must  depend  on  the  character 
of  that  present  in  the  particular  sample.  Light,  dusty,  non-adherent  matter 
may  be  removed  by  sifting  or  winnowing  by  means  of  an  air  current,  and 
then  weighing  the  residual  grain.  Adherent  dirt  will  probably  require 
washing  of  the  wheat,  and  with  this  operation,  the  absorption  of  water 
by  the  grain  comes  in  as  a disturbing  factor,  for  which  provision  must  be 
made.  The  following  is  a convenient  method  of  estimating  dirt  by  the 
process  of  washing.  From  a fair  sample  of  the  wheat  a convenient  quantity 
is  weighed  off  for  the  estimation  ; 20  grams  is  usually  a good  workable 
quantity.  A duplicate  20  grams  is  weighed  off  and  placed  in  the  hot- 
water  oven  in  order  to  determine  moisture  (see  subsequent  paragraph  782). 
The  lot  to  be  washed  is  put  in  a wide-mouthed  bottle,  and  shaken  up  with 
water  ; the  water  is  then  poured  on  a fine  sieve.  This  operation  is  repeated 
until  the  grain  is  clean.  The  wheat  is  then  poured  on  to  the  sieve  and 
examined  in  order  to  see  whether  there  are  any  pieces  of  stone  or  other 
matter  which  ought  to  be  picked  out.  Finally  the  drained  wheat  is  trans- 
ferred to  a dish  and  also  placed  in  the  hot-water  oven.  Both  it  and  the 
portion  for  moisture  determination  are  allowed  to  remain  until  the  weight 
is  constant  (say  over  the  night),  which  is  then  noted.  The  difference 
between  the  two  figures  is  the  amount  of  dirt  removed  by  washing.  An 
example  will  make  this  clear. 

Wheat  taken  for  moisture,  20  grams; 


Weight  after  drying 

. . 17-54  grams. 

Wheat  taken  for  washing,  20  grams ; 

Weight  after  washing  and  drying 

..  16-06  „ 

Weight  of  dirt  removed 

..  1-48  „ 

Multiply  by  . . 

5 

Amount  of  dirt  in  samples  . . 

7-40  per  cent, 

780.  Grinding  of  Samples. — The  fine  whole  meal  for  other  determina- 
tions is  best  obtained  by  passing  the  wheat  through  a combined  grinding 
and  cutting  mill,  of  which  a very  convenient  form  is  that  known  as  the 
“ Enterprise  drug  mill.  An  ordinary  coffee  mill  might  answer  the  purpose, 
but  most  likely  would  not  cut  up  the  bran  sufficiently  fine.  The  process 
adopted  is  as  follows  : — The  mill  is  set  as  fine  as  it  will  run  without  clogging. 
(It  need  scarcely  be  mentioned  that  every  part  must  first  be  thoroughly 
cleaned.)  The  wheat  is  then  poured  in  the  hopper  and  run  through  as 
rapidly  as  possible.  The  grist  is  next  put  into  a fine  sieve,  about  20  or  24 
meshes  to  the  inch,  and  sifted.  The  bran  is  returned  to  the  mill,  and  run 
through  and  again  sifted  ; this  operation  is  repeated  on  the  coarser  particles 
until  the  whole  of  the  meal  has  been  thus  sifted.  Care  must  again  be 
taken  at  the  end  to  clean  every  particle  out  of  the  mill  and  add  it  to  the 
meal  ; this  is  essential,  because  the  latter  particles  are  more  branny  than 
the  former.  The  meal  is  next  stirred  up  thoroughly,  and  then  stored  in 
a tightly  corked  or  stoppered  bottle.  In  this  way  a whole  meal  is  obtained. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  691 


which  of  necessity  is  an  exact  representative  of  the  grain.  It  may  be  asked 
whether  the  wheat  should  be  cleaned  in  any  way  previous  to  grinding  for 
analysis.  The  answer  to  such  a question  is  that  this  must  depend  on  the 
purpose  for  which  the  analysis  is  required.  An  analysis  made  for  the 
purpose  of  buying  or  selling  by  should  be  performed  on  a sample  representing 
the  bulk  of  the  parcel  of  grain  in  question  ; it  should  therefore  be  in  no 
way  cleaned  or  washed.  When  a miller  requires  to  know  the  analytic 
character  of  a variety  of  wheat  in  the  cleaned  state,  the  analysis  would 
obviously  be  made  on  the  sample  after  cleaning.  Undoubtedly  the  safest 
plan  is  to  analyse  the  sample  exactly  as  collected,  unless  the  analysis  is 
made  for  some  special  purpose.  If  a clean  wheat  is  analysed  the  weight 
of  cleaned  wheat  obtained  from  a definite  weight  of  the  uncleaned  wheat 
should  first  be  ascertained. 

781.  Experimental  Test  Mills. — The  best  general  mode  of  testing  wheats 
is  that  of  first  reducing  the  same  to  flour,  and  then  testing  the  flour.  With 
this  end  in  view,  the  larger  mills  are  frequently  fitted  with  small  reduction 
plants  by  which  an  experimental  quantity  of  wheat  may  be  reduced  to 
flour,  and  this  tested  before  the  whole  of  the  wheat  is  ground.  The  plant 
for  this  purpose  may  be  of  various  sizes,  from  a fairly  complete  small  roller 
mill  installation  to  a specially  made  machine  for  reducing  purposes,  the 
different  separations  being  made  by  hand.  In  this  connexion  see  the 
description  of  Tattersall’s  special  milling  plant  in  Chapter  XX  XII  on  Routine 
Mill  Tests.  On  the  flour  thus  obtained,  determinations  may  be  made  of 
such  kinds  as  are  employed  on  flour  produced  during  the  ordinary  course  of 
manufacture.  It  does  not  follow  that  the  experimentally-made  flour  will 
be  equal  in  every  respect  to  that  obtained  in  practice  on  the  larger  scale; 
but  usually  the  results  are  sufficiently  nearly  comparative  with  each 
other  to  afford  valuable  information.  The  practical  miller  will  naturally 
make  allowances  for  the  milling  peculiarities  of  the  wheats  he  may  be 
thus  examining. 

With  a mill  of  this  kind,  the  percentage  yield  of  straight  flour,  bran, 
and  other  offal,  obtainable  from  each  particular  sample  of  wheat  may  be 
determined. 

782.  Moisture  Determinations.— These  may  be  made  either  on  the  ground 
meal  from  grain  or  the  dressed  flour.  They  are  sometimes  made  on  the 
whole  wheat,  but  with  this  there  is  the  objection  that  the  unbroken 
grains  lose  moisture  somewhat  slowly.  In  view  of  the  wide  extension  of 
the  use  of  conditioning  and  analogous  appliances  and  processes  in  modern 
milling,  a check  on  the  moisture  of  the  wheat  and  also  on  the  flour,  bran, 
and  other  products  has  become  of  considerable  importance.  The  percentage 
of  water  or  moisture  is  usually  found  by  weighing  out  a definite  quantity 
of  the  flour  or  meal  in  a small  dish,  and  then  drying  in  the  water  oven 
until  it  no  longer  loses  weight.  When  a number  of  samples  have  to  be 
assayed,  some  regular  method  of  procedure  is  necessary.  The  following 
method  may  be  adopted  : — 

Procure  from  the  apparatus  dealer  one  dozen  selected  glass  dishes, 
2^  in.  diameter.  Mark  these  with  the  numbers  1 to  12  on  the  sides 
with  a vTiting  diamond.  Have  a little  box  made  in  which  to  keep  these 
dishes.  The  box  should  have  a shelf,  supported  a little  way  from  the 
bottom,  containing  a series  of  separate  holes,  one  for  each  dish,  so  that 
they  may  be  kept  without  danger  of  breakage.  Clean  and  dry  each  dish, 
and  then  weigh  it  carefully  ; enter  the  weights  in  the  note-book,  and, 
previous  to  using  each  dish,  test  its  weight.  This  may  be  done  very  quickly, 
as  the  weights  are  already  approximately  known.  It  will  be  found  that, 
if  msed  with  care,  the  weight  of  the  dishes  will  remain  constant,  within 


692 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


some  four  or  five  milligrams,  for  a considerable  time.  Time  may  be  still 
further  economised  by  having  a series  of  counterpoises  made  for  the  set 
of  dishes.  These  consist  of  little  brass  boxes  in  the  shape  of  weights,  the 
tops  of  which  can  be  unscrewed.  Brass  counterpoises  of  this  description 
can  be  readily  obtained.  Have  engraved  on  the  top  of  the  counterpoises 
a series  of  numbers  corresponding  to  those  on  the  dishes ; clean  the  counter- 
poises and  dishes  thoroughly,  and  balance  the  one  against  the  other  in  the 
following  manner  : — Place  No.  1 dish  in  the  left-hand  balance  pan,  and  the 
corresponding  counterpoise  in  the  other,  together  with  its  cover.  Fill  up 
the  counterpoise  with  shot  until  it  is  as  nearly  as  possible  of  the  same  weight 
as  the  dish,  then  add  little  shreds  of  tinfoil  until  the  two  exactly  counter- 
balance each  other  ; finally  screw  the  lid  and  box  part  of  the  counterpoise 
together.  Proceed  in  exactly  the  same  way  with  all  the  dishes.  In  this 
case  the  shelf  of  the  box  for  the  dishes  should  also  have  little  holes  cut  in 
it  for  the  counterpoises,  so  that  each  may  be  kept  immediately  in  front 
of  its  particular  dish.  Having  a set  of  counterpoises,  before  using  each 
dish  test  it  on  the  balance  against  its  counterpoise,  and  if  necessary  adjust 
the  weight  with  the  rider.  As  the  dishes  gradually  become  lighter  through 
use,  the  rider  will  have  to  be  placed  on  the  left-hand  or  dish  side  of  the 
balance.  In  case  the  balance  is  one  which  is  only  fitted, with  the  rider 
arrangement  on  the  right-hand  side,  the  dish  may,  if  wished,  be  placed 
on  that  side,  and  the  weights  on  the  left  in  weighing  ; this,  however,  is 
liable  to  lead  to  confusion  and  mistakes  in  reading  the  weights.  As  the 
dishes  grow  lighter,  their  weight  against  the  counterpoise  is  really  a minus 
quantity,  and  should  be  entered  as  such  in  the  note-book.  For  a long  time 
the  difference  between  the  two  is  inappreciable,  but  still,  for  the  sake  of 
accuracy,  the  test  should  always  be  made.  When  the  dish  and  counterpoise 
differ  more  than  -005  gram,  the  latter  should  be  readjusted.  Having  a 
number  of  determinations  to  make,  weigh  out  exactly  10  grams  of  each 
flour  in  a dish,  then  place  them  in  the  hot-water  oven  and  allow  them  to 
dry  for  24  hours  ; at  the  end  of  that  time  the  water  will  be  expelled.  Take 
out  the  dishes,  allow  them  to  cool  in  a desiccator,  and  weigh  as  quickly  as 
possible.  As  the  weight  of  each  is  approximately  known,  put  the  larger 
weights  on  the  balance  pan  before  taking  the  dish  from  the  desiccator. 
After  weighing,  return  the  dishes  to  the  oven  for  another  hour,  and  again 
weigh  ; the  two  weighings  should  agree  within  a milligram.  Dry  flour 
is  very  hygroscopic  ; that  is,  it  absorbs  moisture  with  great  rapidity.  This 
is  noticeable  during  weighing,  for  a sample  will  often  gain  while  in  the 
balance  as  much  as  five  milligrams.  The  student  will  at  first,  for  this 
reason,  get  his  weights  too  high.  The  best  plan  is  to  put  on  the  rider  at 
a point  judged  to  be  too  high,  and  then  at  each  trial  bring  it  to  a lower 
number  until  it  is  found  to  be  at  one  at  which  the  dish  is  the  heavier.  Then 
take  the  lowest  figure  known  to  be  above  the  weight  of  the  dish,  for  if  the 
rider  now  be  moved  upwards,  the  dish  will  often  be  found  to  gain  in  weight 
just  as  rapidly  as  the  rider  is  moved  upward.  Before  the  dish  is  removed  from 
the  desiccator  for  the  second  weighing,  put  in  the  pan  the  lowest  weights 
before  found  to  be  too  heavy.  After  a time  the  student  will  find  that  he 
can  get  his  two  weighings  to  always  practically  agree  ; he  may  then,  but 
not  till  then,  dispense  with  the  second  weighing.  It  is  evident  that  the 
flour  after  being  deprived  of  its  moisture  will  weigh  less  ; the  weight  taken, 
therefore,  less  the  weight  of  dried  flour,  equals  the  moisture  ; this,  when 
10  grams  are  employed,  multiplied  by  10  gives  the  percentage. 

There  are  now  made  flat  porcelain  numbered  dishes  for  milk  analysis, 
and  these  may  if  wished  be  used  instead  of  glass  dishes  for  moisture  deter- 
minations. Another  convenient  form  of  dish  is  that  of  pohshed  nickel  made 
in  tlie  flat  shape  ; these  latter  possess  the  advantage  of  being  unbreakable. 


CO]\LMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  693 


Fig.  101. — Hot-Water  Oven. 


783.  Hot-Water  Oven. — These  ovens  are  usually  made  of  copper,  and 
are  of  the  appearance  and  shape  shown  in  Fig.  101.  The  oven  consists 
of  an  inner  and  outer  casing,  with  a space  between  them  about  an  inch  in 
thickness  ; the  top,  bottom,  two  sides,  and  back,  are  therefore  double. 
This  space  for  about  half  the 
height  of  the  oven  is,  when  in 
use,  filled  with  water,  which  is 
kept  boiling  by  a bunsen  flame 
placed  underneath.  Anything 
placed  in  the  oven  is  thus  kept  at 
a temperature  of  from  96-100  ° C., 
but,  while  there  is  any  water 
within  the  casing,  never  above 
the  latter  temperature.  In  order 
to  prevent  the  oven  boiling  dry, 
a little  feed  apparatus  is  a con- 
venient attachment.  This  usually 
consists  of  a copper  vessel  open 
at  the  top,  and  communicating 
by  means  of  a pipe  with  the 
water  space  of  the  oven.  Through 
the  bottom  of  this  vessel  is  passed  a piece  of  glass  tubing,  the  top  of 
which  reaches  to  the  height  at  which  it  is  desired  that  the  water  shall  re- 
main in  the  oven.  This  glass  tubing  is  kept  in  its  place  by  a piece  of 
india-rubber  tubing,  which,  while  making  a water-tight  joint,  allows  the 
tube  to  be  slidden  up  or  down  as  wished.  A small  stream  of  water  is  led 
into  the  feed  apparatus  ; this  feeds  the  oven,  and  the  overflow  passes  out 
through  the  glass  tube,  which  should  either  stand  over,  or  be  led  into,  a 
drain. 

Another  very  good  plan  is  to  have  fitted  to  the  top  of  the  water  oven 
an  inverted  Liebig’s  condenser,  through  the  outer  casing  of  which  a stream 
of  cold  water  is  passed.  The  steam  from  the  boiling  water  in  the  casing 
is  then  condensed  by  the  condenser,  and  returned  to  the  oven.  The  oven, 
having  been  once  filled,  will  not  need  replenishing  for  a considerable  time, 
as  the  loss  of  water  is  very  little.  The  condenser  should  be  made  of  brass 
or  copper  tubing  ; the  inner  tube  about  f in.  in  diameter,  and  the  outer 
IJ  in.  : the  length  should  be  from  24  to  30  in.  The  cold  water  should 
enter  the  jacket  at  the  bottom.  When  a condenser  is  used,  the  oven  should 
also  be  fitted  with  a glass  water  guage,  to  indicate  the  height  of  the  water 
as  shown  in  the  figure.  With  this  arrangement  the  oven  may  be  filled 
with  distilled  water,  and  so  loss  of  heat  by  the  formation  of  crust  be  pre- 
vented. 

Where  time  is  an  object,  it  is  convenient  to  use  an  oil  oven  instead 
of  one  filled  with  hot  water.  The  oven  is  similar  in  construction,  but 
the  jacket  is  filled  with  oil,  and  the  temperature  raised  for  wheat  or  flour 
drying  to  105-110°  C.,  being  regulatedlby  adjusting  the  burner,  or  by  means 
of  an  automatic  regulator. 


^784.  Vacuum  Oven. — In  estimations  of  moisture  for  milling  purposes, 
speed  is  almost  always  of  the  utmost  importance  ; the  authors  have  there- 
fore designed  and  used  with  success  a special  form  of  vacuum  oven  for  such 
determinations.  The  oven.  Fig.  102,  is  of  circular  shape  with  fiat  bottom, 
and  consists  of  an  inner  casing,  a,  a,  and  an  outer  jacket  6,  h,  of  copper. 
The  diameter  of  a,  a,  may  be  from  10  to  12  in.,  and  the  internal  height 
about  5 in.  The  space  between  the  casing  and  jacket  should  be  not 
less  than  1 in.  At  c is  attached  a small  water  guage.  A return 


694 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


condenser  is  fixed  as  shown  at  d,  d.  By  means  of  a burner  fixed  under 
the  oven  the  temperature  of  the  water  in  the  jacket  is  maintained  at  100°  C. 
Or  if  wished,  a solution  of  potassium  carbonate  may  be  employed  ; this 
boils  at  a temperature  above  100°  C.  and  depending  on  the  degree  of  con- 
centration of  the  solution.  A drawback  is  that  the  salt  slowly  attacks  the 
metal  of  the  oven.  Or  an  organic  liquid  such  as  toluol,  boiling  at  107°  C., 
may  be  used.  With  this,  however,  care  must  be  taken  as  the  boiling 
liquid  is  inflammable.  The  advantage  of  the  higher  temperature  is  the 
more  rapid  drying  capacity  of  the  oven.  At  e is  fixed  a pipe  leading  to  a 
Korting  or  other  efficient  vacuum  pump.  The  open  end  at  e is  turned  up 


so  as  to  prevent  the  inrush  of  air  from  impinging  on  the  contents  of  dishes 
in  the  oven.  At  / a tap  is  placed,  by  which  air  can  be  admitted  into  the 
oven  ; on  the  opposite  side  / is  shown  a small  Bourdon  vacuum  gauge. 
The  upper  part  of  the  oven  is  drawn  into  an  opening  about  6 in.  internal 
diameter,  terminating  in  a flange  the  face  of  which  is  turned  and  ground 
perfectly  true  at  h.  On  this  rests  a gun-metal  lid,  i,  also  faced  true.  At 
j,  j,  are  hinged  screw  clamps  by  which  the  lid  is  securely  screwed  down 
to  make  an  air-tight  joint  with  the  upper  flange  of  the  oven.  In  use  the 
oven  is  made  hot  by  a burner  arranged  underneath,  preferably  of  the  ring 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  • 695 


type.  Flat  nickel  dishes  are  most  suitable  for  the  flours  or  meals.  These 
are  placed  in  the  oven  and  then  the  lid  is  fixed  in  position.  In  order  to 
make  the  joint,  the  faces  of  the  flanges  are  smeared  with  a luting  mixture 
of  asphalt um  and  paraffin,  or  a rubber  ring  may  be  used.  In  this  latter 
case  the  ring  and  the  faces  of  the  flanges  should  be  well  blackleaded.  The 
top  at  / is  closed  and  the  vacuum  pump  started,  and  kept  at  work  so  as  to 
maintain  a good  vacuum  as  shown  by  the  gauge.  Drying  is  exceedingly 
rapid  and  thorough  with  the  flat  dishes  in  immediate  contact  with  the  flat 
bottom  of  the  oven.  The  minimum  time  for  complete  drying  should  be 
ascertained  by  an  actual  test  ; after  which,  provided  the  vacuum  is  kept 
up,  the  dishes  with  their  contents  may  simply  be  dried  for  the  requisite 
time  and  then  weighed.  To  reopen  the  oven  the  pump  is  turned  off,  and 
then  the  tap  / carefully  opened  to  admit  air.  The  clamps  are  then  unscrewed 
and  the  lid  slid  off. 

785.  Rapid  Determinations  of  Moisture. — The  following  method  has  been 
recommended  by  Parsons  for  obtaining  rapid  determinations  of  moisture. 
The  principal  requisite  is  a perfectly  neutral  petroleum  oil,  free  from  animal 
or  vegetable  oils  and  mineral  substances,  and  having  the  following  constant — 
Sp.  gr.,  0-920 ; flash  test,  224° ; boiling  point,  about  288°.  This  oil  is  heated 
to  about  120°  for  some  time  and  then  kept  in  a well- stoppered  bottle.  The 
object  of  this  treatment  is  to  secure  a liquid  of  neutral  character  and  free 
from  any  matter  which  is  volatile  up  to  the  temperature  of  120°.  In  making 
an  estimation,  a quantity  of  oil  about  six  times  the  weight  of  the  substance  to 
be  dried  is  heated  in  a basin  or  dish  in  a drying  oven  at  a temperature  of 
115°  and  then  weighed.  In  meal  and  flour  determinations,  convenient 
quantities  would  be  5 grams  of  the  meal  and  about  30  grams  of  the  oil. 
A small  glass  rod  may  also  be  conveniently  weighed  with  the  dish  and  oil. 
The  weighed  portion  of  the  substance  is  then  added  to  the  oil  and  stirred 
in.  There  will  be  usually  a slight  effervescence ; when  this  is  over  the  dish 
should  be  placed  in  the  drying  oven  for  a short  time  and  weighed  ; the 
loss  is  moisture.  It  is  stated  that  the  whole  operation  may  be  completed 
in  less  than  half  an  hour, 

786.  Moisture  by  Distillation  Processes. — Apparatus  has  been  devised 
by  which  the  water  driven  off  from  grain  or  its  products  by  means  of  a hot 
oil  bath  is  collected  and  measured,  thus  serving  as  a means  of  determination 
of  moisture.  A weighed  quantity  of  the  wheat  or  other  grain  is  placed  in 
a proper  receptacle,  and  covered  with  moisture-free  oil.  This  vessel  has 
a tube  leading  therefrom  to  a condenser,  from  which  any  liquid  escaping 
is  received  in  a tall  graduated  measure.  The  vessel  is  enclosed  in  a jacket 
and  is  fitted  with  thermometers  so  as  to  measure  the  temperature  to  which 
it  is  to  be  subjected.  On  heating  to  about  110°  C.  the  whole  of  the  moisture 
of  the  grain  is  driven  off,  condensed  by  the  condenser,  and  collected  in  the 
measuring  vessel.  This  latter  is  so  graduated  as  to  allow  the  amount  of 
condensed  water  to  be  at  once  read  off  in  percentages  without  any  calcula- 
tion. The  estimations  can  be  rapidly  made,  and  a fairly  large  quantity  of 
material  is  taken  for  each  test  ; both  these  are  of  advantage  in  an  apparatus 
commercially  worked  in  a mill. 

787.  Effect  of  Humidity  of  Air  on  Moisture  of  Flour. — Flour  is  exceedingly 
hygroscopic  and  absorbs  or  loses  moisture,  according  to  whether  the  atmo- 
sphere is  damp  or  dry,  with  great  readiness.  Richardson  examined  a series 
of  flours  immediately  on  coming  from  the  mill,  and  again  after  being  exposed 
to  the  atmosphere  for  a day,  with  the  following  results  : — 


696 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No. 


Original 

Moisture. 

9-48 

7-80 

7-85 

7-97 

13-69 


Gain 
or  Loss. 

+0-65 

+2-15 

+2-30 

+2-15 

-3-28 


Second 

Day. 

10-13 

9-95 

10-15 

10-12 

10-41 


It  wdU  be  seen  that,  notwithstanding  the  wide  differences  in  percentage 
of  moisture  on  the  first  day,  they  had,  at  the  end  of  the  second,  become 
practically  equalised.  Richardson  next  allowed  these  fiours  to  remain 
exposed  to  the  atmosphere  for  16  days,  making  during  that  period  15  deter- 
minations of  moisture.  In  one  and  the  same  flour  during  that  time  varia- 
tions of  nearly  5 per  cent,  were  observed.  In  the  following  table  the  results 
are  expressed  in  weight  in  lbs.,  which  100  lbs.  of  the  original  flour  would 
have  assumed  under  the  conditions  ; — 


Xo. 


». 

1. 

Original 

Weight. 

100  lbs. 

Original 

Moisture. 

9-48 

Highest  Weight 
during  16  Days. 

102-88  lbs. 

Lowest  Weight 
during  16  Days. 

99-53  lbs. 

Amount'of 

Variation. 

3-35  lbs. 

2. 

100  „ 

7-80 

104-87  „ 

100-00  „ 

4-87  „ 

3. 

100  „ 

7-85 

105-20  „ 

100-00  „ 

5-20  „ 

4. 

100  „ 

7-97 

105-95  „ 

100-00  „ 

5-95  „ 

5. 

100  „ 

13-69 

100-00  „ 

95-35  „ 

4-65  „ 

No.  1 of  these  flours  was  the  well-known  brand,  Pillsbury’s  Best  ; it 
will  be  of  interest  to  give  the  weight  of  this  each  time  determined,  and  also 
the  relative  humidity  of  the  air  each  day. 


Date. 

March  7 . . 

Weight  of 

Flour. 

100-00  lbs. 

Relative 
Humidity 
of  Air. 

Date. 

March  17 

Weight  of 

Flour. 

100-38  lbs. 

Relative 
Humidity 
of  Air. 

42-2 

„ 8 .. 

100-65  „ 

46-4 

„ 18  .. 

101-88  „ 

59-5 

„ 10  . . 

99-53  „ 

35-0 

„ 19  .. 

102-03  „ 

60-1 

„ 11  .. 

101-73  „ 

59-0 

„ 20  .. 

102-48  „ 

55-6 

„ 12  .. 

102-68  „ 

60-1 

„ 21  .. 

101-43  „ 

51-8 

„ 13  .. 

99-88  „ 

34-0 

„ 22  . . 

101-68  „ 

51-1 

„ 14  . . 

101-08  „ 

— 

„ 24  . . 

102-88  „ 

66-9 

„ 15  .. 

101-53  „ 

48-2 

It  will  be  observed  that  with  an  increased  dampness  of  the  air,  the 
weight  of  the  flour  is  also  increased.  Of  course,  in  strictness,  the  weight 
of  the  flour  is  governed  by  the  degree  of  humidity  prior  to  the  moisture 
determination,  rather  than  that  at  the  time  the  determination  is  actually 
made. 

On  exposing  a sample  of  patent  flour  to  an  atmosphere  kept  absolutely 
saturated  with  water,  it  absorbed  more  than  26  per  cent,  of  its  original 
'weight  in  64  hours.  The  following  table  gives  the  weight  at  different 
intervals  : — 

Weight  of  flour  taken  . . . . . . . . 1-0000  grams, 

after  35  minutes  . . . . . . 1-0285  ,, 


18  hours. . 
22  „ . . 
42  „ . . 
64  „ 


1-0930 

1-2005 

1-2405 

1-2670 


These  variations  in  weight  of  which  flour  is  capable  go  far  toward  explain- 
ing discrepancies  in  water-absorbing  power,  and  yield,  of  laboratory  samples. 

788.  Gluten  Determinations. — The  strength  of  flour  has  been  amply  dis- 
cussed in  a previous  chapter,  in  which  it  is  shown  that  it  largely  depends 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  697 


on  the  quantity  and  character  of  the  insoluble  proteins  contained  in  the 
flour.  In  a crude  form  these  are  obtained  in  the  well-known  washing  pro- 
cess for  gluten.  One  great  objection  to  the  gluten  test  is  the  difficulty  of 
knowing  precisely  when  the  whole  of  the  starch  has  been  removed,  and 
then  stopping  short  of  washing  away  any  of  the  gluten  itself.  In  many  flours 
the  gluten  begins  to  disintegrate  and  wash  away  before  the  whole  of  the 
starch  disappears.  With  some  little  experience  the  same  worker  can  get 
concordant  results,  but  this  is  not  invariably  the  case  with  two  workers 
testing  against  each  other  ; one  will  then  frequently  throughout  a whole 
series  uniformly  get  higher  results  than  the  other.  As,  therefore,  consider- 
able differences  may  exist  in  the  percentages  of  crude  gluten  obtained,  both 
in  the  wet  and  dry  state,  it  is  recommended  that  in  addition  the  “ true 
gluten  or  protein  matter  be  also  determined  by  a direct  nitrogen  estima- 
tion, Even  when  there  are  marked  discrepancies  in  the  crude  gluten  as 
obtained  by  washing,  the  true  gluten  varies  only  within  comparatively 
narrow  limits.  J 

As  an  index  of  strength,  it  is  recommended  that  the  following  estimations 
be  made  ; — Percentage  of  gluten  wet  and  dry  by  the  washing-out  process, 
and  of  true  gluten  by  nitrogen  determination  on  the  dry  gluten  ; all  of  these 
to  be  calculated  on  the  whole  flour.  Appearance  and  physical  character  of 
the  gluten  to  be  noted.  Percentage  of  total  proteins  in  the  whole  flour. 

789.  Gluten  Extraction. — One  of  the  most  important  points  is  that  a 
uniform  method  is  always  adopted.  The  following  is  a very  convenient 
mode  of  working.  Thirty  grams  of  the  flour  should  be  accurately  weighed 
and  transferred  to  one  of  Pfleiderer’s  small  doughing  machines  (made 
especially  for  the  purpose).  To  this  should  be  added  in  the  machine  15 
cubic  centimetres  (=15  grams)  of  water  from  a graduated  pipette.  The 
whole  should  then  be  thoroughly  kneaded,  receiving  100  revolutions  by 
the  counter  after  the  flour  and  water  are  first  roughly  mixed.  (While  the 
machine  is  exceedingly  convenient,  the  dough  may  as  an  alternative  be 
made  by  hand.)  From  the  resultant  dough  one  or  two  portions  of  exactly 
15  grams  each  should  be  accurately  weighed  and  then  transferred  to  a 
small  glass  containing  sufficient  cold  water  to  keep  them  entirely  submerged 
in  which  they  must  be  fetllowed  to  remain  for  exactly  an  hour  (The  second 
piece  is  only  to  be  weighed  off  in  event  of  a duplicate  being  required.)  The 
weighed  portion  of  dough  contains  exactly  10  grams  of  flour,  and  should  be 
washed  in  the  following  manner  : — Prepare  some  water  at  a temperature 
between  70°  and  80°  F.,  and  partially  fill  a clean  bowl  with  same.  For 
reasons  before  given  the  water  must  be  ordinary  tap  water,  and  not  distilled 
water.  Wash  the  lump  of  dough  by  kneading  it  gently  between  the  fingers 
in  the  water,  using  no  muslin  or  other  enclosing  substance.  The  starch  is 
gradually  washed  away,  and  the  remaining  dough  acquires  the  consistency 
and  characteristic  feel  of  gluten.  Take  care  that  no  fragments  are  washed 
ofl  the  main  lump  ; and  after  the  gluten  is  approximately  freed  from  starch, 
place  it  aside  on  a clean  surface  of  glass  or  porcelain  : let  the  washing  water 
settle,  and  decant  it  very  carefully  through  a fine  hair  sieve.  Should  there 
be  any  fragments  of  gluten  on  the  sieve,  pick  them  up  with  the  main  piece 
and  do  the  same  with  any  remaining  in  the  basin.  Take  some  more  of  the 
tepid  water  and  repeat  the  washing  some  little  time  longer  ; change  the 
water  about  two  or  three  times,  with  the  same  precaution  against  loss  as 
before.  The  last  washing  water  should  remain  almost  clean.  The  gluten 
may  now  be  taken  as  pure,  freed  as  far  as  possible  from  adherent  moisture 
and  weighed. 

In  the  case  of  Hungarian  and  certain  other  flours  of  very  high  water- 
absorbing power,  it  is  sometimes  advisable  to  make  a slacker  dough  for 


698 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gluten  extraction  than  that  just  described.  For  this  purpose  add  20  c.c.  of 
water  to  the  30  grams  of  flour,  and  take  16-66  grams  of  the  dough  for  each 
estimation.  This  weight  contains,  as  before,  exactly  10  grams  of  flour. 
If  preferred,  10  or  20  grams  of  flour  may  be  weighed  off  and  made  up  into 
a dough  with  water  direct  for  this  estimation.) 

When  it  is  intended  to  determine  the  gliadin  in  the  gluten,  30  or  33-33 
grams  of  dough  should  be  taken  for  washing  purposes  instead  of  15  or  16-66 
grams.  The  washing  operation  should  be  conducted  as  before.  The  whole 
mass  of  gluten  is  then  weighed  and  registered  as  wet  gluten,  after  which  it  is 
separated  into  two  halves  by  weight.  One  is  dried  for  dry  gluten,  and  the 
other  is  used  for  the  gliadin  estimation  (see  paragraph  854.) 

For  the  drying  of  the  gluten,  pieces  of  paper  should  be  prepared  before- 
hand in  the  following  manner  : — Take  a sheet  of  cartridge  or  other  stout 
paper  and  cut  it  up  into  small  pieces  3 inches  square.  Place  these  in 
the  hot- water  oven  and  dry  at  212°  F.  for  two  days.  Take  them  out  and 
allow  to  cool  in  a desiccator,  and  weigh  them  off  rapidly  to  within  a decigram. 
Mark  the  weight  in  pencil  on  the  top  left-hand  corner  of  the  paper.  Keep  a 
store  of  these  in  a clean  box.  If  preferred,  these  may  be  obtained  ready 
cut  from  a printer.  They  will  then  be  found  to  be  of  just  the  same  weight  ; 
and  if  two  pieces  be  equally  dried  in  the  hot-water  oven  they  mil  still  counter- 
balance each  other.  This  should  be  verified  by  an  actual  trial.  Wlien  any 
number  of  glutens  are  being  simultaneously  determined,  a blank  piece  of 
paper  may  be  put  in  the  oven  with  the  glutens,  and  used  throughout  as  a 
counterpoise  when  weighing  them.  If  for  any  reason  special  accuracy  is 
required,  the  paper  should  in  each  case  be  dried  and  weighed  for  each  estima- 
tion. 

Having  weighed  the  gluten  as  above  described,  mould  it  between  the 
fingers  and  notice  its  physical  condition,  whether  tough  and  elastic,  soft  and 
flabby,  or  “ short  ” and  friable.  Make  a note  of  same.  Mould  it  into  a 
ball  and  place  it  on  the  centre  of  one  of  the  weighed  papers.  On  the  one 
corner  mark  the  date,  and  below,  the  name  or  number  of  the  flour,  with  the 
v'eight  of  the  wet  gluten.  Next  place  the  gluten  in  the  hot-water  oven  and 
dry  at  212°  F.  until  the  weight  is  constant  ; then  weigh  to  the  decigram, 
subtract  the  weight  of  the  paper,  or  weigh  against  the  counterpoise  piece, 
and  express  the  result  in  percentages.  The  gluten  adheres  to  the  paper,  and 
thus  may  be  kept  as  a record  of  the  flour. 

To  determine  the  true  gluten,  break  up  the  crude  dry  gluten  into  coarse 
fragments,  and  estimate  nitrogen  by  the  Kjeldahl  method,  as  described  in 
Chapter  XXVIII.  The  percentage  of  true  gluten  should  be  returned  on 
the  whole  flour,  and  should  be  at  least  80  per  cent,  of  the  crude  gluten. 

By  means  of  the  same  process  (Kjeldahl)  determine  the  total  proteins 
in  the  flour. 

790.  Extraction  of  Gluten  from  Wheat-Meal. — The  meal  may  be  weighed 
and  made  into  a dough  precisely  as  with  flour  ; or  if  wished,  10  or  20  grams 
only  may  be  weighed  off  and  transferred  to  a basin,  and  then  mixed  with 
sufficient  water  to  make  a somewhat  slack  dough.  This  is  allowed  to  stand 
as  before  for  one  hour  under  water.  Instead  of  washing  the  dough  direct 
in  the  bowl,  it  is  preferable  to  first  enclose  it  in  a piece  of  either  fine  muslin 
or,  preferably,  millers’  bolting  silk.  This  must  be  held  securely  in  order 
to  prevent  any  loss  of  the  dough,  which  must  be  held  under  water  in  the 
bowl  and  kneaded  between  the  fingers  until  a fresh  lot  of  water  is  no  longer 
caused  to  become  milky  by  the  escaping  starch.  On  opening  the  silk,  it 
. will  be  found  not  only  to  contain  the  gluten,  but  also  the  bran  of  the  wheat, 
and  these  have  to  be  separated  from  each  other.  With  the  harder  wheats 
tliis  is  done  without  much  difficulty,  but  in  the  case  of  those  that  are  softer 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  699 


it’is  sometimes  almost  impossible  to  recover  the  whole  of  the  gluten.  After 
having  washed  out  the  starch,  squeeze  the  water  from  the  silk,  and  then 
open  it  out  on  a piece  of  glass.  There  will  usually  be  one  fairly  sized  lump 
of  gluten  ; take  this  out  and  rinse  it  moderately  free  from  bran  in  a basin  of 
clean  water,  next  squeeze  it  well  together,  then  pick  off  any  tolerably  large 
pieces  of  gluten  that  remain  on  the  silk,  and  add  them  to  the  main  lump. 
After  each  addition  again  squeeze  the  piece  together  and  rinse  off  any  loose 
bran.  The  difficulty  is  now  to  gather  together  any  particles  remaining  in 
the  bran — these  are  often  so  small  as  to  be  scarcely  visible.  Take  the  mass 
of  tolerably  clean  gluten  and  add  to  it  a portion  of  the  bran,  roll  them  together 
with  considerable  force  between  the  palms,  and  then  wash  off  the  bran. 
Tills  process  of  rubbing  together  the  main  lump  of  gluten  and  the  bran 
effects  the  removal  of  any  little  fragments  of  gluten  by  their  sticking  to  the 
larger  piece  ; which,  in  virtue  of  its  adhesive  property,  picks  them  out 
from  the  bran,  just  as  a magnet  picks  out  iron  filings  from  among  those  of 
brass.  Treat  the  whole  of  the  bran  remaining  on  the  silk  in  this  manner  ; 
the  result  will  be  a lump  of  gluten  still  containing  a little  bran.  With  a hard 
wheat,  however,  the  whole  of  the  gluten  will  have  been  thus  recovered  ; with 
the  softer  ones  it  is  sometimes  advisable  to  drain  the  water  off  the  bran  and 
again  rub  it  all  up  with  the  gluten.  In  every  case  inspect  the  bran  most 
carefully  before  throwing  it  away  ; the  bran  should  also  be  rubbed  between 
the  fingers  ; this  will  often  detect  fragments  of  gluten  that  escape  the  eye. 
Having  got  the  whole  of  the  gluten  together,  wash  it  time  after  time  until 
free  from  bran.  This  is  a tedious  operation,  but  one  that  can  be  performed 
by  vigorous  and  careful  treatment.  Pour  every  lot  of  water  on  to  the  muslin 
in  order  to  see  that  no  gluten  is  lost.  The  washing  must  be  continued 
until  the  gluten  yields  no  turbidity  to  clean  water. 

The  subsequent  processes  are  performed  on  the  wheat  gluten  precisely 
as  with  that  from  flours. 

791.  Water- Absorbing  Capacity. — One  of  the  best  methods  of  deter- 
mining the  water-absorbing  capacity  of  a sample  of  flour  is  by  doughing  it, 
and  then  judging  by  the  consistency  of  the  dough.  The  dough  may  be 
tested  in  this  manner  shortly  after  being  made  up,  and  again  after  an  interval 
of  some  hours.  A more  or  less  accurate  judgment  is  thus  formed  of  the 
water-absorbing  power  of  the  flour  when  first  made  into  dough,  and  also 
its  capacity  for  resistance  to  the  changes  which  take  place  in  the  constitu- 
ents of  flour  while  standing  for  some  time  in  a moist  condition.  The 
unfortunate  point  about  such  determinations  is,  that  judging  by  the  appear- 
ance and  stiffness  of  a dough  is  exceedingly  uncertain  : one  person’s  own 
judgment  is  not  at  all  times  alike,  and  the  difficulty  is  multiplied  infinitely 
when  an  attempt  is  made  to  compare  that  of  several  persons.  Again,  there  is 
the  fact  that  for  all  purposes  of  exactitude  it  is  essential  that  some  means 
shall  exist  for  expressing  results  in  actual  figures. 

Finding  the  problem  in  this  state,  one  of  the  authors  devised  apparatus, 
which  had  as  its  object  the  determination  of  water-absorptive  power,  and 
giving  a numerical  expression  of  the  result.  The  starting  point  was  to 
decide  on  some  mode  of  expressing  yield  : the  first  idea  was  to  make  use 
of  the  number  of  quartern  loaves  of  bread  that  could  be  produced  from  a 
sack  of  flour.  But  here  the  difficulty  occurred  that  different  bakers  are 
in  the  habit  of  weighing  their  bread  into  the  oven  at  different  weights,  to 
say  nothing  about  the  possibilities  of  different  weights  when  the  bread 
leaves  the  oven.  Further,  the  use  or  non-use  of  “ fruit  ” renders  this 
method  of  considerable  uncertainty.  There  is  again  the  fact  that  some 
bakers  work  with  slacker  doughs  than  do  others. 

After  considering  several  possible  modes  of  expression,  the  decision 


700 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


arrived  at  by  the  authors  was  to  give  the  quantity  of  water  that  a specific 
weight  of  the  flour  took,  in  order  to  produce  a dough  of  definite  and  stand- 
ard consistency.  By  almost  universal  consent  the  standard  of  weight 
of  flour  would,  in  this  country,  be  the  sack  of  280  lbs.,  while  water  can  be 
conveniently  expressed  in  quarts.  The  quart  being  the  quarter  of  a gallon, 
and  the  gallon  weighing  10  lbs.,  render  it  easy  to  convert  quarts  into  either 
gallons  or  lbs.  It  will  be  noticed  that  the  adoption  of  this  standard  does 
not  touch  on  the  contested  question  of  loss  of  water  in  the  oven.  If 
preferred  the  tests  may  be  made,  and  the  results  expressed  in  c.c.  per  100 
grams,  i.e.  parts  per  hundred. 


792.  Water-Absorption  Burette. — The  operation  of  doughing  resolves 
itself  into  taking  any  convenient  quantity  of  flour  and  adding  sufficient  water 
to  it  to  make  a dough  of  normal  stiffness  and  then  calculating  out  the  water 
employed  into  the  proportion  of  quarts  per  sack.  The  simplest  way  of  doing 

this  is  to  fix  on  the  quantity  of  flour,  and  then 
make  a measuring  instrument  for  the  water 
(“  burette  ""  or  “ pipette  ”),  wffiich  shall  be 
graduated  so  that  each  division  represents 
a quart  of  water  per  sack.  Such  a mea- 
suring instrument  is  the  first  part  of  the 
apparatus  described  ; in  using  it,  the  flour 
is  weighed  out,  and  the  quantity  of  water 
run  in  is  at  once  read  off,  without  any  cal- 
culation whatever,  as  quarts  per  sack.  The 
practical  advantages  of  this  method  are  evi- 
dent, as  from  a small  doughing  test  a baker 
can  at  once  direct  how  much  water  is  to  be 
added  per  sack  of  any  particular  flour.  The 
strength  burette,  together  with  the  visco- 
meter, is  shown  in  Fig.  104  : at  the  top  of 
the  instrument  is  the  zero  mark,  between 
wiiich  and  “ 40  there  are  no  graduations  ; 
the  tube  is  then  graduated  in  single  quarts 
down  to  80  at  the  lower  end.  At  the  bottom 
a glass  jet  is  attached  by  means  of  a piece 
of  india-rubber  tubing  ; this  is  normally 
kept  closed  by  the  spring-clip,  but  may  be 
opened  at  will  by  pressing  the  twn  buttons 
shown,  one  on  either  side.  In  use,  the  bur- 
ette may  be  held  in  the  hand,  but  is  prefer- 
ably fixed  in  a burette  stand.  It  may  be 
filled  either  by  pouring  in  w^ater  at  the  top, 
or  by  opening  the  clip  and  sucking  it  up 
through  the  jet. 

It  is  important  to  bear  in  mind  that 
if  great  exactness  is  required  in  doughing 
tests,  the  dougli,  wiien  made,  should  have  a definite  temperature.  It 
is  recommended  that  for  this  purpose  that  of  70°  F.  be  adopted.  If  pos- 
sible, a flour- testing  laboratory  should  stand  permanently  at  as  nearly  as 
possible  that  temperature.  Before  starting  a series  of  tests,  the  w^ater 
should  be  adjusted  to  70°  F.  ; and  the  flours,  if  cold,  allowed  to  stand  in  a 
warm  room  sufficiently  long  to  give  the  same  temperature  wffien  tested  by 


Fig.  103. — Burette,  Arranged 
WITH  Reservoir. 


the  tliermometer. 

Wliere  a number  of  flours  are  being  tested, 


it  is  an  exceedingly  con- 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  701 


venient  plan  to  have  a water  reservoir  attached  to  the  burette  ; the  whole 
apparatus  will  then  appear  as  shown  in  Fig.  103. 

In  the  lower  part  of  the  figure  the  burette  is  seen  fixed  in  a stand.  At 
a is  a second  tube  opening  into  the  burette  above  the  clip  : by  means  of 
india-rubber  tubing,  this  second  tube,  a,  is  attached  to  a glass  reservoir.  A, 
which  stands  on  a shelf  above  the  level  of  the  top  of  the  burette.  By  means 
of  a spring-clip  at  a the  liquid  in  the  reservoir  is  shut  off  from  the  burette. 
The  burette  being  empty,  open  the  clip  a ; the  water  flows  from  A upward 
into  the  burette  ; when  the  level  coincides  with  the  zero  mark  close  this 
clip,  and  proceed  to  deliver  the  desired  quantity  of  water  by  pressing  the 
clip  at  the  bottom  of  the  burette.  In  this  manner  the  instrument  may  be 
filled  with  great  convenience  and  rapidity. 

To  test  a flour,  weigh  out  as  exactly  as  possible  one  and  a half  ounces 
of  the  sample,  and  transfer  it  to  a small  cup  or  basin.  Next  fill  the  burette 
with  water  until  the  level  exactly  stands  at  the  top  graduation  mark.  Then 
place  the  cup  containing  the  flour  under  the  burette,  and  press  the  clip, 
allowing  the  water  to  run  out  until  down  to  as  many  quarts  as  it  is  thought 
likely  the  flour  will  require.  Then,  by  means  of  a stirring  rod,  or  bone  spa- 
tula, work  the  flour  and  water  into  a perfectly  even  dough  ; try,  by  mould- 
ing it  between  the  fingers,  whether  it  is  too  stiff  or  too  slack  : if  so,  dough 
up  a fresh  sample,  using  either  more  or  less  water  as  the  case  may  be.  Hav- 
ing thus  made  a dough  of  a similar  consistency  to  that  usually  employed, 
read  off  from  the  burette  how  much  water  has  been  used.  The  figures 
will  express,  without  any  further  calculation  whatever,  how  many  quarts  of 
water  the  flour  will  take  to  the  sack.  It  is  well  before  judging  the  stiffness 
of  the  dough  to  allow  it  to  stand  for  some  time.  The  authors  allow  their 
doughs  to  remain  an  hour  before  testing  them. 

It  is  not  safe  to  state  from  the  doughing  test  alone  how  many  loaves  a 
certain  flour  is  capable  of  yielding  per  sack,  because  different  bakers,  by 
working  in  different  manners,  do  not  get  the  same  bread  yield  from  one  and 
the  same  flour.  Each  baker  should  therefore  ascertain  for  himself  by  means 
of  a baking  test,  working  according  to  his  own  methods,  how  many  loaves 
he  obtains  from  a sack  of  any  particular  flour.  He  can  then  in  the  following 
manner  arrange  for  himself  a table  showing  the  bread  equivalent  of  the 
“ quarts  per  sack  ” readings  of  the  burette.  To  make  this  test,  take  a 
sack  of  flour  and  measure  the  quantity  of  water  requisite  to  make  a dough 
of  the  proper  consistency.  Then  count  the  number  of  2-lb.  or  4-lb.  loaves 
it  yields  on  being  baked.  Suppose  that  the  flour  takes  70  quarts  of  water  : 
then  dough  up  a sample  with  the  burette,  using  water  to  the  70  quart  mark, 
and  take  dough  of  that  stiffness  as  the  standard.  Any  other  flour  of  the 
same  character  which  takes  the  same  quantity  of  water  to  make  a dough 
of  similar  consistency  will  turn  out  about  the  same  yield  of  bread.  Suppose 
another  sample  of  flour  takes  72  quarts  of  water,  then  it  will  make,  neglect- 
ing the  slight  loss  in  working,  5 lbs.  more  dough  (one  quart  of  water  weighs 
2J  lbs.).  Weighing  the  bread  into  the  oven  at  4 lb.  6 oz.  per  the  4-lb.  loaf, 
every  two  quarts  more  water  per  sack  means  rather  over  another  4-lb.  loaf 
produced.  In  exact  figures  the  additional  5 lbs.  of  dough  yield  4 lbs.  9 oz. 
of  baked  bread,  or  practically  4J  lbs. 

In  this  easy  manner,  by  this  instrument,  a baker  may  determine  for 
himself,  without  any  but  the  simplest  mental  calculation,  and  working 
according  to  his  own  processes,  how  much  bread  a particular  flour  yields. 
It  is  advised  that  every  baker  should  for  himself  construct  a table  of  results, 
based  on  his  own  method  of  working.  To  do  this,  let  him,  as  suggested, 
make  a trial  baking,  and  find  out  how  many  quarts  of  water  a sack  of 
any  one  flour  takes,  and  how  many  loaves  it  produces.  Enter  those 
figures  in  the  table,  then  for  every  two  quarts  more  add  on  4J  lbs.  of 


702  THE  TECHNOLOGY  OF  BREAD-MAKING. 

bread  or  1|  4-lb.  loaves  : for- every  two  quarts  less  subtract  the  same 
amount. 


793.  The  Viscometer. — In  order  to  carry  the  water  absorption  problem 
a step  further,  it  is  necessary,  not  only  to  have  made  the  dough,  but  also 
to  devise  means  for  mechanically  determining  its  consistency.  This  is  the 

more  difficult,  as  different  kinds  of  flour  pro- 
duce doughs  of  different  character.  Thus,  a 
spring  American  flour  will  yield  a dough 
whose  essential  characteristic  is  rigidity  ; a 
Hungarian  flour  yields  a soft  dough,  but  one 
which,  nevertheless,  possesses  most  remark- 
able tenacity.  Any  instrument  for  measuring 
the  consistency  of  dough  must  take  into  ac- 
count these  two  somewhat  opposite  characters, 
giving  each  its  proper  value.  The  resistance 
of  the  dough  to  being  squeezed,  and  its  resist- 
ance to  being  pulled  asunder,  must  both  be 
taken  into  account.  The  second  part  of  the 
flour-testing  apparatus  consists  of  an  instru- 
ment for  definitely  measuring  the  viscosity  of 
dough.  This  is  effected  by  forcing  a definite 
quantity  of  dough  through  a small  aperture, 
and  measuring  the  time  taken  in  so  doing,  the 
force  being  constant.  The  machine  for  mak- 
ing this  measurement  is  termed  a “ Visco- 
meter,” literally,  a measurer  of  viscosity.  It 
is  so  arranged  that,  in  doing  the  work  of  for- 
cing the  dough  through  the  aperture,  both  the 
stiffness  and  tenacity  of  the  dough  are  called 
into  play  as  resisting  agents.  The  conse- 
quence is  that  a very  soft  and  tenacious 
dough  may  prove  its  viscosity  to  be  as  great 
as  that  of  a stiff  dough  with  comparatively 
little  tenacity.  Undoubtedly  this  is  in  keeping 
with  the  observed  facts  of  baking,  for,  as  is 
often  said,  certain  flours  will  bear  being  made 
much  slacker  than  others  ; that  is,  their  tena- 
city as  dough  more  than  makes  up  for  their 
comparatively  little  stiffness  or  rigidity. 

The  viscometer  consists  essentially  of  a 
cylinder,  having  a weighted  and  graduated 
piston,  and  an  aperture  through  the  bottom 
for  the  exit  of  the  dough  ; the  stiffer  the 
dough,  the  more  slowly  does  the  piston  de- 
scend. Since  the  first  instrument  was  made  a 
number  of  alterations  and  refinements  have 
been  introduced  with  the  object  of  diminishing 
certain  causes  of  error  which  were  revealed  on 
experiment.  In  its  present  form  the  instru- 
ment is  affected  in  its  worldng  by  the 
condition  of  the  dough,  and  that  only  ; 
further,  it  takes  cognizance  both  of  the  tenacity  and  the  rigidity  of  the 
dough.  It  is  claimed  for  the  viscometer  that  it  affords  a means  of  absolute 
measure  of  these  two  qualities  of  stiffness  and  tenacity.  In  certain  cases 
where  two  doughs  have  been  submitted  to  the  judgment  of  bakers,  and 


Fig.  104. — Viscometer  and 
Strength  Burette. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  703 


then  tested  by  the  viscometer,  that  judged  the  softer  to  the  touch  has  been 
registered  by  the  viscometer  as  the  dough  of  greater  consistency.  The 
very  simple  explanation  is  that  it  is  difficult  to  form  an  accurate  judgment 
of  tenacity  by  handling  a small  piece  of  dough.  Flours  which  exhibit  this 
particular  combination  of  softness  and  tenacity  are  just  those  which  bakers 
would  say  require  to  be  worked  slacker  than  others.  Consequently,  even  in 
these  instances,  the  viscometric  measurement  affords  a valuable  indication 
of  the  working  water-absorbing  capacity  of  the  flour.  Millers  and  bakers 
who  have  seen  the  apparatus  at  work  endorse  this  opinion.  In  using  the 
instrument,  the  dough  is  first  put  into  the  viscometer,  and  the  time  which 
the  piston  takes  to  travel  between  two  of  its  graduations  is  noticed. 

Fig.  104  is  a sectional  drawing  of  the  viscometer,  about  one-tliird  the 
actual  size  of  the  instrument.  The  lower  part,  marked  u &,  is  a cylindrical 
base,  through  which  are  two  lightening  holes,  marked  y z.  The  cylinder, 
e /,  and  flange,  c d,  are  cast  in  one  piece  ; c d has  a collar  turned  down 
to  fit  inside  a b,  the  edge  of  c d is  milled.  Through  the  bottom  of  the 
cylinder  is  a hole,  marked  t ; the  upper  edge  of  this  hole  is  rounded  off,  in 
order  that  no  cutting  edge  shall  be  presented.  This  aperture  may  be  opened 
or  closed  at  will  by  the  cover,  u,  which  slides  between  a pair  of  guides,  and 
may  be  drawn  in  or  out  by  the  rod  and  milled  head,  v.  The  piston,  m n, 
consists  of  a disc  of  gun-metal,  the  lower  edge  of  which  is  rounded  : this 
piston  is  attached  to  the  bottom  of  a trunk,  m o,  the  diameter  of  whicli  is 
about  one-sixteenth  of  an  inch  less  than  that  of  the  piston.  This  piston 
trunk  passes  through  the  cylinder  cover,  g h ; in  the  top  of  this  cover  is 
screwed  a tube,  i j,  carrying  at  its  upper  end  a collar,  k 1.  Both  this  collar 
and  the  cylinder  cover,  g h,  are  bored  to  exactly  fit  the  trunk  of  the  piston. 
The  cylinder  cover  tube,  i j,  and  collar,  k I,  therefore  together  act  as  a guide 
for  the  piston,  allowing  it  to  slide  steadily  up  and  down  with  the  minimum 
of  friction.  The  bottom  of  the  cylinder  cover  fits  over  the  top  of  the  cylinder, 
and  is  secured  in  its  place  by  a pair  of  studs  and  bayonet  catches,  s h.  On 
the  upper  part  of  the  trunk  are  three  lines,  pgr,  the'distance  between  each 
pair  being  three-eighths  of  an  inch.  This  trunk  is  loaded  inside  in  order 
to  give  it  the  requisite  weight.  With  the  exception  of  the  piston,  m ii,  the 
instrument  is  throughout  constructed  of  brass. 

794.  Method  Employed^  in  using  the  Viscometer. — It  is'  first  necessary 
to  fix  on  a standard  of  stiffness  for  doughs  : that  adopted,  by  the  authors 
is  such  as  allows  the  piston  of  the  viscometer  to  fall  from  mark  p to  mark  r 
in  60  seconds.  As  such  doughs  are  slacker  than  those  employed  for  many 
purposes,  a stiffer  standard  may,  if  wished,  be  selected ; in  such  a case  the 
readings  may  be  taken,  if  desired,  when  the  piston  has  made  half  its  stroke, 
that  is,  has  travelled  from  r to  q instead  of  the  whole  distance,  r to  p.  Each 
individual  user  of  the  instrument  may  thus  determine  on  a standard  for 
himself. 

Wliatever  standard  is  selected,  whether  the  60 -seconds"  standard 
employed  by  the  authors,  or  another,  weigh  out  one  and  a half  ounces  of 
flour,  add  water  from  the  strength  burette,  and  dough  up  the  sample  as 
before  described,  using  a quantity  of  water,  which,  as  well  as  can  be  judged, 
shall  give  a dough  of  standard  consistency.  The  dough  may  be  mixed  by 
hand  in  a basin,  but  the  authors  strongly  recommend  the  use  of  one  of 
Pfleiderer’s  small  doughing  machines  made  specially  for  testing  purposes  : 
these  have  the  great  advantage  that  they  mix  the  dough  thoroughly,  and  with 
absolute  uniformity.  The  machine  is  made  with  water-tight  bearings, 
and  is  fitted  with  a revolution  indicator  by  which  the  number  of  turns  given 
to  the  handle  are  registered.  Place  the  flour  and  water  direct  in  the  machine, 
and  turn  the  handle  so  that  the  upper  edges  of  the  blades  approach  each 


704 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


other.  When  the  flour  and  water  are  roughly  mixed,  scrape  down  the 
sides  of  the  machine  by  means  of  a small  spatula  : note  the  position  of  the 
revolution  indicator,  and  give  the  dough  fifty  revolutions.  When  suffi- 
ciently mixed,  take  the  dough  from  the  machine  and  set  it  aside  in  a small 
glass  tumbler,  or  other  vessel,  for  one  hour.  Cover  over  with  a glass  plate 
in  order  to  prevent  evaporation.  When  examining  a number  of  samples, 
dough  them  up  one  after  the  other  for  an  hour,  and  then  come  back  to  the 
further  testing  of  the  first  one,  and  take  them  in  rotation. 

Having  thoroughly  cleaned  the  cylinder  and  piston  of  the  viscometer, 
fill  the  cylinder  with  the  dough  to  be  tested  ; to  do  this,  slightly  open  the 
bottom  aperture  and  push  in  the  dough  through  the  top,  by  means  of  a 
stout  spatula.  In  this  way  fill  the  cylinder  completely,  taking  care  that 
there  are  no  air  spaces  ; shut  the  aperture,  t,  and  then,  holding  the  cylinder 
horizontally  in  the  left  hand,  put  on  the  cylinder  cover,  the  piston  being 
at  the  top  of  its  stroke.  Secure  it  by  means  of  the  bayonet  catches,  and 
stand  the  cylinder  squarely  on  the  base,  a h.  Arrange  a vessel,  w x,  to  receive 
the  dough  as  forced  through  the  instrument.  Next  have  ready  a watch 
with  seconds’  hand  (a  chronograph  is  the  most  convenient  thing,  if  one 
happens  to  be  in  possession  of  the  worker)  ; pull  out  the  milled  head,  v, 
the  piston  begins  to  descend.  As  soon  as  the  line  r coincides  with  the  top  of 
k I,  note  the  time,  or  start  the  chronograph  : note  again  when  the  hne  p 
descends  to  k I,  and  observe  how  long  the  piston  has  taken  to  travel  this 
distance.  If  exactly  sixty  seconds,  or  whatever  other  standard  has  been 
selected,  the  dough  is  of  the  standard  consistency,  and  the  quantity  of  water 
used  is  that  required  by  the  particular  flour  to  make  a dough  of  the  standard 
stiffness.  Feel  the  dough  with  the  fingers  and  see,  especially,  whether  it 
seems  hard  or  soft.  A soft  dough,  which  nevertheless  goes  through  the 
machine  slowly,  must  possess  great  tenacity.  Such  flours  have  almost 
invariably  high  water-retaining  power.  The  test  having  been  made,  turn 
back  the  bayonet  catches,  and  withdraw  the  cylinder  cover,  piston,  and 
guide  from  the  cylinder.  Remove  the  dough  from  the  piston,  and  clean 
out  the  cyhnder  by  means  of  a spatula.  In  handling  the  piston  be  careful 
not  to  hold  it  with  the  cover  end  uppermost,  as  the  piston  rod  then  slides 
backwards,  and  is  stopped  by  the  piston  coming  violently  in  contact  with 
the  cover.  The  piston  being  thin  is  liable  by  rough  usage  in  this  way  to  be 
forced  off  the  rod.  When  the  instrument  is  done  with,  the  cylinder  should 
be  soaked  in  water,  so  as  to  remove  any  traces  of  dough  that  might  clog  the 
valve  at  the  bottom. 

Having  described  the  mode  of  using  the  instrument,  its  action  on  the 
dough  may  now  be  examined.  In  the  first  place,  the  lower  edge  of  the 
piston  and  the  upper  one  of  the  aperture  through  the  cylinder  bottom  are 
both  rounded,  therefore  the  dough  is  not  subjected  to  any  cutting  action. 
In  the  next  place,  the  piston  during  its  descent  meets  with  no  resistance 
wliatever  except  that  due  to  the  dough  itself  ; as  it  passes  down  through 
the  hole  in  the  cylinder  cover  it  is  impossible  for  the  dough  to  find  its  way 
up  through  that  opening  against  the  downward  movement  of  the  piston  ; 
consequently,  there  is  no  clogging  whatever  of  the  moving  parts  of  the 
apparatus.  The  dough,  in  order  to  make  its  way  out,  has  to  alter  its  shape 
so  as  to  pass  through  the  small  hole  at  the  bottom,  consequently  its  rigidity 
is  here  taken  into  account.  At  the  end  of  the  stroke,  the  piston  is  found 
to  have  pushed  out  a plug  of  dough  from  the  centre  of  the  cylinder,  leaving 
a ring  of  dough  standing  round  its  outside.  To  force  out  this  plug,  the  piston 
must  liave  torn  away  these  particles  of  dough  from  the  annulus  (ring)  of 
dough  left  standing.  Hence  it  is  that  this  apparatus  registers  so  thoroughly 
the  tenacity  of  the  dough  as  well  as  its  rigidity.  By  shading  the  dough  in 
tlie  figure  an  attempt  has  been  made  to  indicate  the  probable  lines  of  move- 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  705 


merit  of  the  dough  as  the  piston  passes  downwards.  An  inspection  of  the 
drawing  of  the  viscometer,  and  a study  of  its  principles,  show  that  it  is  the 
condition  of  the  dough,  and  that  only,  which  can  possibly  affect  the  speed 
at  which  the  piston  descends. 

In  practice  it  is  well  to  have  at  least  two  tests  made  on  the  same  flour 
with  the  viscometer.  When  the  approximate  water-absorbing  power  is 
knovTi,  these  may  well  be  taken  at  2 quarts  below  and  2 quarts  above  this 
point  respectively.  Having  obtained  a pair  of  piston  readings,  one  above 
and  the  other  below  the  sixty  seconds  (or  other  predetermined)  standard, 
the  actual  quantity  of  water  corresponding  to  the  standard  may  be  calcu- 
lated in  the  following  manner  For  entering  the  tests  it  is  recommended 
that  a book  be  procured  ruled  both  ways  of  the  pe.ge  : the  water-absorption 
results  should  then  be  entered  as  showTi  in  Fig.  105,  pa,ge  708.  Supposing 
70  quarts  to  have  run  through  in  90  seconds,  and  72  quarts  in  50  seconds, 
then  on  drawing  a line  connecting  these  two  points,  the  place  where  it  crosses 
the  horizontal  line  marked  60  in  seconds,  will  give  the  wa.ter  absorption  in 
quarts.  Thus  referring  to  Flour  No.  2,  Fig.  105,  the  72  quart  dough  ran 
through  in  86  seconds,  and  the  74  quart  dough  in  43  seconds  : on  these 
l^oints  being  joined  by  a line,  it  cut  the  60  seconds  line  at  very  nearly  mid- 
way between  the  72  and  the  74  quart  lines,  therefore  the  water-absorbing 
capacity  was  taken  as  being  73  quarts.  In  this  way,  the  absorptive  power 
of  various  flours  for  intermediate  points  between  two  readings  was  arrived 
at.  An  inspection  of  Fig.  105  shows  that  the  upper  portions  of  these  lines, 
graphically  representing  absorbing  capacity,  are  very  nearly  parallel  to 
each  other.  The  authors  find  if  the  first  test  made  gives  a viscometer 
reading  between  45  and  90,  that  the  water  absorption  may  be  deduced  vith 
sufficient  correctness  for  most  purposes  in  the  following  manner  : — On  a 
page,  properly  ruled  both  ways,  set  out  two  or  three  lines  similar  to  those 
in  Fig.  105  representing  the  water-absorbing  power  of  different  flours.  Then, 
supposing  a flour  under  examination  has  run  through  the  viscometer  in 
87  seconds,  with  68  quarts  of  water,  make  a mark  at  that  point,  and  draw 
from  it  a line  across  the  60  seconds  line,  and  pa^rallel  to  the  lines  of 
other  flours  previously  set  out.  Reckon  the  water  absorption  from 
the  point  where  it  cuts  the  60  seconds  line.  Such  a flour  would  probably 
absorb  about  69-5  quarts  of  water.  Judging  from  a number  of  flours 
that  have  been  tested  in  this  manner,  the  single  test  gives  results 
that  very  seldom  are  more  than  0-5  quart  off  from  those  obtained 
by  doughing  the  flour  with  two  different  quantities  of  water. 

Examples  of  a few  detailed  viscometer  tests  are  given  in  the  table  on 
page  706.  The  heavier  figures  are  the  calculated  quarts  per  sack  for  60 
seconds. 

795.  Stability  Tests. — As  the  name  implies,  these  are  tests  made  in  order 
to  determine  the  rate  at  which  a softening  down  of  the  flour  occurs  during 
the  time  it  remains  in  the  dough.  An  old-fashioned  millers’  method  of 
testing  flours  consisted  in  doughing  them,  allowing  them  to  stand  for  some 
twenty-four  hours,  and  then  examining  the  stiffness  of  the  dough.  Sound 
flours  would  stand  fairly  well,  while  those  which  were  unsound  yielded 
doughs  which  “ ran  to  water.”  The  stability  tests,  made  by  the  author 
with  the  viscometer,  were  simply  modifications  of  these.  Samples  of  doughs 
were  kept  for  different  periods  of  time  in  tumblers  with  glass  covers,  which 
fitted  air-tight  in  order  to  prevent  evaporation  ; at  the  end  of  which  time 
they  were  tested  with  the  viscometer.  The  results  of  a number  of  such 
tests  are  given  in  the  table  on  page  707,  and  are  also  represented  in  Fig.  105. 

The  stiffness  of  dough  is,  as  before  remarked,  affected  to  a very  marked 
degree  by  its  temperature,  and  this  particularly  applies  to  any  tests  allowed 


706 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Results  of  Viscometer  Tests  on  Flours. 


No.  Names  and  Description  of  Flours. 

1.  Patent  Flour,  from  American  Hard  Fyfe  Wheat. 

2.  Bakers’  Flour  ,,  „ ,, 

3.  Hungarian  Flour,  First  Patent. 

4.  English  Wheat  Flour. 


TIME  ALLOWED  TO  REMAIN  IN  DOUGH— ONE  HOUR. 


No. 

Quarts  per  i 
Sack.  1 

Seconds. 

No. 

Quarts  per 
Sack. 

Seconds. 

1 

66 

215 

66 

223 

1 

i 

68 

193 

68 

200 

1 

70 

74 

70 

107 

71 

60 

72 

86 

1 

52 

73 

60 

' 74  ’ 

44 

74 

43 

76 

24 

76 

29 

78 

i 10 

78 

16 

i 

1 

1 - 

I 80 

12 

74 

255 

58 

183 

76 

170 

60 

120  1 

78 

60 

62 

82 

3 

80 

38 

4 

63 

60 

82 

25 

64 

27 

84 

18 

66 

19 

86 

10 

— 

to  stand  for  a length  of  time  : it  is  well  therefore  in  such  tests  to  employ 
means  of  keeping  the  doughs  at  a uniform  temperature  during  the  whole 
time  of  standing. 


796.  Effect  of  Temperature. — In  order  to  measure  the  effect  of  variations 
of  temperature  on  water-absorbing  power,  the  following  tests  w'ere  made  : — 
Water  w^as  taken  at  32°,  40°,  etc.,  F.,  up  to  110°  F.  In  order  to  keep  them 
at  the  desired  temperature,  the  doughs  were  placed  in  small  glasses  covered 
with  air-tight  plates,  and  these  immersed  in  a vessel  containing  w^ater  at 
the  same  temperature,  in  which  they  were  kept  for  an  hour.  Three  tests 
w^ere  made  with  each  flour  at  each  temperature,  and  from  these  the  dough 
of  the  standard  consistency  w as  deduced  in  the  manner  previously  described. 
The  results  of  the  tests  are  given  on  page  708. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  707 


Water-absorbing  Power  of  Flours  after  Standing  Different 
Lengths  of  Time  in  the  Dough. 

NOv  Names  and  Description  of  Flours. 

5.  Straight  Grade,  from  No.  2 Calcutta  Wlieat. 

6.  ,,  ,,  ,,  Saxonska  Wheat. 

7.  Town  Households,  No.  I. 

8.  Town  Households,  No.  2. 


TIME  ALLOWED  TO  REMAIN  IN  DOUGH. 

No. 

IMMEDIATE. 

HALF-HOUR. 

THREE  HOURS. 

TWENTY-FOUR  ! 

HOURS  ] 

Quarts 

per 

Sack. 

Seconds. 

Quarts 

per 

Sack. 

Seconds. 

Quarts 

per 

Sack. 

Seconds. 

Quarts 

per 

Sack. 

Seconds. 

70 

114 

70 

93 

68 

92 

62 

77 

72 

60 

71  5 

60 

1 70 

! 60 

64-5 

60 

5 

72 

53 

72 

50 

70 

‘ 56 

66 

49 

— 

— 

74 

29 

72 

40 

68 

30 

— 

— 

— 

— 

74 

j 24 

72 

16 

68 

90 

62 

! 104 

60 

19 

! 70 

66 

— 

— 

65-5 

60 

62 

11 

6 

70-5 

60 

— 

— 

66 

48 

64 

7 

72 

45 

— 

— 

68 

33 

66 

1 5 

— 

— 

— 

— 

70 

14 

— 

— ! 

: j 

i 

68 

116 

64 

120 

56 

1 

.1 

125 

70 

76 

— 

— 

66 

60 

58 

63 

7 

72 

63 

— - 

— 

66 

53 

59 

60 

72 

60 

— 

— 

68 

47 

60  ! 

55 

1 

74 

38 

— 

— 

— 

— 

62  I 



40 

64 

160 

64 

132 

62 

64 

55 

60 

i 

66 

76 

65*5 

60 

62  i 

60 

56 

35 

8 ! 

66-5 

60 

66 

47 

64 

37 

58 

21 

— 

— 

68 

25  1 

66 

30 

60 

18 

— 

— 

— 

— 

— 

— 

62 

11 

1 

1 

! 

64 

8 

Water-absorbing  Power  of  Flours  at  Different  Dough 
Temperatures. 

No.  Names  and  Description  of  Flours. 

1.  A High-Class  Brand  of  Hungarian  Patent  Flour. 

2.  A Patent  Flour  from  Duluth  Wheat. 

3.  A High-Class  Patent  Flour  from  all  English  Wheat. 


708 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Quarts  p3r  Sack. 


Temperature. 

No.  1. 

No.  2. 

No.  3. 

32°  F. 

84-5 

720 

640 

40°  „ 

81*5 

72-5 

640 

50°  „ 

77*5 

700 

610 

60°  „ 

76-5 

69-0 

60-5 

70°  „ 

70-5 

66-0 

550 

80°  „ 

69-0 

62-5 

540 

90°  „ 

670 

61  0 

520 

100°  „ 

66-5 

58-5 

47-5 

110°  „ 

610 

56-5 

44-5 

From  this  table  it  will  be 

seen  that 

in  every 

case  there  is  a falling 

water-absorbing  power  wdth  the  increase  of  temperature. 

In  the  diagram  below,  Fig.  105,  the  results  of  the  water-absorption 
tests  on  the  table  of  flours,  page  706,  headed  “ Results  of  Viscometer  Tests 
on  Flours,’^  have  been  drawn  as  a series  of  curves.  On  the  horizonted  lines 
(co-ordinates)  are  set  oflthe  number  of  seconds  of  time  taken  in  each  visco- 
meter test,  while  the  numbers  representing  the  quarts  of  water  taken  are 
given  on  the  vertical  lines  (abscissae).  The  higher  the  water- a,bsorptive 
capacity,  the  further  to  the  right  does  the  curve  of  the  flour  appear  ; and 
the  more  the  rigidity  of  the  dough  is  lessened  by  an  equal  increment  of 
water,  the  more  nearly  vertical  is  the  line  of  the  curve.  The  results  of 
tests  on  the  loss  of  rigidity  of  dough  of  No.  8 Flour,  a.s  a consequence  of 
standing,  are  also  given  on  in  this  figure.  They  are  marked  S,  a,  h,  c,  d ; S a 
being  the  “ immediate  ’’  test,  and  8 d that  after  twenty-four  hours.  The 
softening  down,  as  the  result  of  standing,  is  well  illustrated  in  the  diagram. 


Fig.  105. — Diagram  of  Water- Absorption 
Results. 


Fig.  106. — Diagram  of  Variations 
OF  Temperature  Results. 


Fig.  106  above  gives  a graphic  representation  of  the  efle^  of  varia- 
tions in  temperature,  as  expressed  above  on  this  page.  The  quarts 


COMMERCIAL  TESTING  OE  WHEATS  AND  FLOURS.  709 


per  sack  are  given  on  the  horizontal  lines,  and  the  various  temperatures 
on  the  abscissae.  The  greater  the  falling  off  in  water-absorbing  power  with 
increase  of  temperature,  or,  in  other  words,  the  greater  the  softening  of  the 
dough,  the  more  rapid  is  the  descent  of  the  curve. 

797.  Colour. — This  is  probably  at  the  same  time  one  of  the  most  diffi- 
cult and  most  important  tests  to  be  made  on  flour.  The  great  difficulty 
is  that  the  colour  of  the  flour  itself  is  not  necessarily  a criterion  of  that  of 
the  bread  produced.  For  example,  some  lower  grade  winter  wheat  flours 
look  very  white  and  even  better  coloured  than  harder  spring  wheat  flours, 
whereas  the  bread  made  therefrom  is  exceedingly  dark  and  ill-coloured. 
Further,  the  colour  of  the  bread  is  dependent  not  only  on  that  of  the  flour, 
but  on  the  mode  of  working,  and  other  factors  which  vary  in  themselves. 

Unless  tests  are  made  for  no  other  purpose  than  the  comparison  of 
flours  placed  side  by  side,  it  is  absolutely  necessary  to  have  some  means  of 
measuring  and  registering  colour.  The  most  familiar,  and  on  the  whole 
the  most  successful,  instrument  for  this  purpose  is  that  known  as  Lovi- 
bond’s  Tintometer  or  colour-measurer.  As  this  appliance  has  been  exten- 
sively employed  in  the  following  investigations,  a description  of  it  at  this 
stage  is  necessary. 

798.  Lovibond’s  Tintometer. — The  instrument  itself  is  an  optical  device. 
Fig.  107,  by  means  of  which  a sample  of  flour,  bread,  or  other  body  may 
be  viewed  side  by  side  with  a prepared  surface  of  the  purest  white  obtain- 
able. With  the  instrument  is  furnished  a set  of  transparent  standard  tinted 
glasses.  These  are  numbered  from 
0-01  upwards  to  5-0,  or  higher  if 
wished,  so  that  any  degree  of 
depth  of  tint  may  be  built  up 
from  these  glasses,  proceeding 
upwards  by  intervals  of  0-01  at  a 
time.  For  flour- testing  purposes 
three  series  of  such  tinted  glasses 
are  employed.  One  of  these  is  a 
Yellow,  the  second  a Red,  and  a 
third  Blue. 

The  base.  A,  carries  a stand, 

A^,  which  is  supported  in  an 
oblique  position  by  the  strut,  A^. 

On  this  stand  is  placed  the  opti-  Fig.  107. — Lovibond’s  Tintometer. 
cal  instrument  itself,  B.  This 
consists  of  a tube,  blackened  on  the  inside,  and  having  apertures  on 
the  upper  end,  G,  through  which  one  looks  in  using  the  instrument.  These 
openings  are  three  in  number,  the  outer  ones  being  intended  for  use  with 
both  the  eyes  simultaneously,  while  that  in  the  middle  is  for  the  purpose  of 
one-eye  examination.  At  the  lower  end  of  the  tube,  H,  provision  is  made 
for  the  reception  of  two  small  cells,  fitted  with  slits  into  which  the  standard 
glasses,  J,  are  to  be  inserted.  At  F the  coloured  slabs  under  examination 
are  placed  for  purposes  of  measurement. 

The  spongy  texture  of  bread  gives  it  a mottled  appearance  when  viewed 
through  this  instrument,  and  so  a special  device  is  necessary  by  which  the 
sponginess  may  be  transformed  into  an  even  and  uniform  tint.  This  is 
shown  in  Fig.  108,  which  is  a plan  of  the  tintometer  arranged  for  this  purpose. 
K M is  a flat  stand,  on  which  the  tintometer,  B,  is  fixed.  At  L L,  between  the 
cells  for  standard  glasses,  and  H,  are  placed  two  lenses  such  as  those  employed 
for  spectacles.  At  W the  standard  white  comparing  surface  is  arranged, 


710 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  the  slice  of  bread  under  examination  is  fixed  at  Y.  On  looking  through 
the  eye-pieces  at  G,  the  lenses  throw  both  the  white  surface,  W,  and  the  bread, 
Y,  out  of  focus,  so  that  they  appear  as  even  coloured,  structureless  surfaces. 


Fig.  108. — Tintometeb  Fitted  for  Use  with  Bread. 


To  use  the  tintometer,  the  standard  white  comparing  surface  must  first 
be  prepared.  Fill  one  of  the  little  trays  supplied  with  the  instrument  with 
some  speciedly  prepared  plaster  of  Paris,  also  supplied  : press  down  with  a 
piece  of  clean  glass  until  a smooth  uniform  surface  is  obtained  : if  for  bread, 
fill  the  cavity  in  the  stand  at  W in  the  same  way. 

When  using  the  first  arrangement  of  the  instrument,  stand  it  in  a con- 
venient position  facing  a window  looking  toward  the  north,  and,  if  possible, 
so  that  the  light  is  from  a white,  cloudy  sky,  rather  than  when  the  sky  is 
perfectly  blue.  In  this  latter  case  it  is  well  to  place  a piece  of  white  paper 
or  white  opal  glass  between  the  light  and  the  surfaces  being  examined. 
On  the  one  side  of  the  field,  F,  place  the  tray  of  white,  and  the  flour  on  the 
other.  On  looking  down  through  the  tintometer  the  flour  will  look  much 
the  darker.  In  the  cell  over  the  white  surface  put  in  some  of  the  standard 
colour  glasses  already  referred  to — say,  for  example,  1-0  Y.  (yellow)  and 
0*50  R.  (red).  The  white  light  from  the  prepared  surface  passes  up  to  the 
eye  through  these,  and  gives  that  surface  an  apparent  yellowish  red  tint. 
Note  whether  the  tint  as  a whole  is  lighter  or  darker  than  the  flour,  also 
whether  too  red  or  too  yellow.  If  too  dark  and  too  red,  remove  the  red 
glass  and  substitute  a lighter  one,  and  again  compare.  If  too  light  and  too 
red,  add  a little  more  yellow,  leaving  the  red  undisturbed.  Very  quickly 
it  is  possible  to  get  the  tint  matched  approximately  : it  is  in  getting  an 
exact  match  that  the  difficulty  occurs.  It  is  well  to  try  one  or  tw^o  modifica- 
tions of  the  standard  glasses,  and  see  which  comes  the  nearest.  If  the  eye 
is  uncertain,  it  is  often  an  assistance  to  place  a dark  glass,  say  5-0  Y.,  in 
front  of  the  eye-piece,  and  look  through  the  middle  aperture  at  both  the 
flours  ; they  appear  much  darker,  but  minute  shades  of  colour  are  thus 
more  readily  distinguished.  Having  got  the  tint  which  so  closely  as  possible 
matches  the  flour,  a register  should  b^e  made  of  the  numbers  of  the  glasses 
composing  it. 

The  bread  form  of  the  instrument  should  be  arranged  horizontally  on 
a stand,  so  that  it  is  at  a comfortable  height  for  the  eyes  of  the  observer 
when  sitting,  and  so  that  the  light  comes  from  a window,  over  the  shoulder, 
as  shown  by  the  arrow,  P,  Fig.  108.  (If  necessary,  the  instrument  may  of 
course  be  arranged  for  the  light  to  fall  from  the  right  instead  of  the  left.) 
Care  must  be  taken  that  neither  the  surface,  W,  nor  that  of  the  bread  has 
tlie  shadow  cast  on  it  of  any  part  of  the  apparatus.  The  use  of  the  standard 
glasses  in  measuring  is  the  same  as  before. 

It  is  scarcely  necessary  to  say  that  colour  judgments  are  difficult,  and 
to  point  out  that  different  persons’  eyes  appreciate  colours  differently. 
One  difficulty  with  the  tintometer  is,  the  comparison  is  being  made  between 
an  opaque  coloured  surface  in  the  case  of  the  flour,  and  a tint  imparted 
to  a beam  of  light  in  the  case  of  the  test-surface — there  is  a difference  in 
quality  which  makes  comparison  difficult.  A desideratum  is  some  form  of 
permanent,  graduated,  tinted  surface  which  can  be  compared  with  the  flour. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  711 


The  great  value  of  the  tintometer  is  for  from  time  to  time  permanently 
measuring  and  checking  the  colour  of  standard  flour  samples  : this  is  well 
worth  any  trouble  taken  in  so  doing.  The  standards  being  thus  kept  veri- 
fied, it  will  be  sufficient  for  ordinary  purposes  to  check  and  compare  flours 
side  by  side  with  the  standards. 


799.  Colour  Investigations. — In  obtaining  the  readings  made  in  con- 
nection with  the  following  research,  the  judgment  of  four  persons  was,  in 
many  instances,  utilised,  while  every  reading  was  checked  by  at  least  two 
persons,  and  always,  where  the  slightest  doubt  was  felt,  by  three. 

Among  methods  of  judging  the  colour  of  flour  the  most  obvious  is  that 
of  testing  the  flour  itself  in  the  normal  dry  condition.  To  this  there  is  the 
objection  that  the  colour  of  dry  flour  depends  not  merely  on  the  nature  of 
the  wheat  and  the  flour  constituents,  but  also  on  the  comparative  coarse- 
ness or  fineness  of  the  particles  of  the  flour.  Further,  on  exposure  to  air 
flour  very  quickly  bleaches,  although  this  of  course  does  not  affect  the 
validity  of  a test  made  on  a sample  taken  from  bulk.  The  bleaching  of 
flour  is  commonly  ascribed  to  light,  but  this  is  not  essential,  for  in  the  follow- 
ing experiment  the  samples  were  kept  during  the  intervcA  between  readings 
in  a dark  cupboard.  The  following  three  dry  samples  gave  tintometer 
readings  as  under,  being  simply  pressed  into  smooth  slabs  and  examined  : — 


Immediate. 
Yellow.  Red. 


After  standing  one  Day. 
Yellow.  Red. 


American  Spring  Bakers  . . 0-27 

Ditto,  another  sample  . . 0*34 

American  Winter  Bakers  . . 0-20 


0*06 

0-25 

004 

on 

0-30 

009 

002 

on 

002 

Pekar^s  Test. — A second  and  well-known  method  of  testing  colour  is  to 
dip  the  compressed  slabs  into  water,  so  as  to  wet  the  surface,  then  allow 
the  same  to  dry  off,  and  read  or  compare  the  colours.  The  tint  is  in  this 
instance  darkened  considerably  as  a result  of  the  action  of  oxydase  in  the 
presence  of  air,  coloured  oxidative  products  being  formed.  In  this  case, 
again,  the  degree  of  granulation  of  the  flour  affects  the  depth  of  colour — a 
coarse  flour  absorbs  more  water,  and  becomes  darker  through  taking  longer 
to  dry,  while  the  surface  has  more  or  less  “ grain  as  a result  of  rough- 
ness of  the  surface  before  wetting. 

A third  method  consists  of  making  the  flour  into  dough,  working  it 
until  perfectly  smooth,  and  then  examining  and  comparing.  One  objection 
to  this  method  is  that  the  colour  of  the  dough  darkens  rapidly  on  the  out- 
side, and  hence,  if  an  attempt  be  made  to  read  off  the  colour,  or  even  com- 
pare a series  of  three  or  more  at  a time,  a new  dough  surface  darkens  visibly 
while  the  comparison  is  being  made.  To  obviate  this,  the  pellet  of  dough 
may  be  placed  on  a sheet  of  colourless  glass,  and  the  colour  of  the  dough 
observed  through  the  glass — in  this  way  the  colour  of  the  dough  proper  is 
seen  as  distinct  from  that  of  the  outer  skin.  It  is  no  uncommon  occurrence 
to  take  two  flours  from  the  same  variety  of  wheat,  the  one  very  fine  and 
the  other  granular,  and  compare  them  either  dry  or  wetted  in  compressed 
slabs.  The  granular  flour  under  both  tests  looks  the  darker , but  on  working 
them  into  dough,  as  just  described,  the  coarser  flour  often  produces  the 
more  “ bloomy  ""  dough  ; bakers  will  at  once  form  their  own  judgment  as 
to  which  of  the  two  will  under  similar  conditions  make  the  best  loaf.  Also, 
of  course,  the  outer  skin  of  the  same  samples  may  be  compared  and  read  if 
necessary. 

Investigation  shows  that  the  colour  of  dough  is  influenced  by  its  degree 
of  stiffness.  Thus,  a spring  bakers’  flour  was  made  into  dough  with  different 
quantities  of  water,  and  the  following  readings  taken  at  the  expiration  of 
one  hour.  At  the  end  of  eighteen  hours,  in  which  the  doughs  were  kept 


712  THE  TECHNOLOGY  OF  BREAD-MAKING. 

in  a water-saturated  atmosphere,  the  colour  of  the  outer  skins  was  also 
read 

Colour  of  Dough.  Colour  of  Skin. 

Yellow.  Reel.  Blue.  Yellow.  Red.  Blue. 

1.  Doughed  with  50  per  cent,  of  water  1-50  0-68  0-08  3-55  2T0  0*86 

2.  Doughed  with  55  per  cent,  of  water  1*42  0-63  — 3-75  2T0  0-56 

3.  Doughed  with  60  per  cent,  of  water  M9  0-54  — 3-15  1-90  0-48 

The  colour  both  of  dough  and  skin  is  darker  in  the  tighter  doughs  ; also 
this  relation  of  colour  holds  good  for  some  time,  for  at  the  end  of  eighteen 
hours  the  order  of  colour  of  the  dough  was  the  same  as  at  the  end  of  one  hour. 

In  order  to  eliminate  so  far  as  possible  the  differences  due  to  variations 
in  tightness  of  doughs,  the  whole  of  the  Hours  were  in  the  subsequent  tests 
treated  with  the  quantity  of  water  sufficient  to  make  doughs  of  uniform 
stifiness.  For  this  purpose  each  flour  was  tested  by  the  viscometer  in  the 
manner  previously  described.  The  next  step  was  to  investigate  the  influence 
of  the  length  of  time  the  dough  had  stood  on  the  depth  of  colour  ; this,  be  it 
remembered,  always  being  read  through  colourless  glass.  The  following 
results  were  obtained  : — 


Winter 

Winter 

Spring 

Spring 

American 

American 

American 

American 

Time. 

Patent. 

Bakers. 

Patent. 

Bakers. 

Y. 

R. 

Y. 

R. 

Y. 

R. 

Y. 

R. 

1 hour  after  mixing 

0-92 

0-29 

F37 

0-94 

102 

0-64 

1-34 

110 

2 hours  after  mixing 

102 

0*36 

1-49 

0*97 

109 

0-64 

1-49 

100 

3 hours  after  mixing 

108 

0*40 

L50 

100 

1-25 

0-75 

1-52 

107 

4 hours  after  mixing  1 TO 

0-43 

1-51 

TOO 

1-20 

0-65 

1-47 

0-97 

22  hours  after  mixing 

108 

0-58 

1-50 

102 

1-20 

0-75 

1-46 

107 

It  may  be  well  here  to  explain  the  precautions  taken  in 

order  to  get 

as  exact  readings  as  possible.  First  of  all,  every  series  of  tests  to  be  read 
were  arranged  in  order  of  colour  as  apparent  to  the  eye  ; then  they  were 
read  in  succession,  commencing  with  the  lightest.  After  matching  No.  I, 
No.  2 was  placed  against  its  (No.  I’s)  standard  tint  glasses  and  seen  to  be 
darker,  then  measured.  In  all  cases  where  there  was  any  apparent  discrep- 
ancy the  reading  received  a checking  by  three  persons.  When  making 
time  measurements  the  following  method  was  adopted  : — First  of  all,  at 
the  expiration  of  the  time,  the  colour  glasses  of  the  preceding  reading  were 
again  placed  in  the  instrument,  thus  taking,  for  example,  the  two  hours’ 
reading  on  the  first  flour  just  given,  the  one  hour  glasses,  Y.  0-92  ; R.  0-29 
were  inserted,  and  the  dough  compared  with  them.  It  was  thus  definitely 
ascertained  that  a distinct  darkening  had  occurred  ; its  measurement  then 
followed.  Each  reading  was  thus  compared  with  that  preceding  throughout 
the  whole  series.  It  will  be  observed  that  a slight  but  steady  darkening 
occurs  throughout  the  whole  series,  the  increasing  red  or  foxy  tint  “ sadden- 
ing ” the  bloom  of  the  yellow.  Unless  otherwise  stated,  future  readings 
were  made  on  doughs  after  standing  one  hour. 

The  authors  have  also  adopted  another  method  of  preparing  the  flour 
for  examination,  which  is  really  a modification  of  the  Pekarised  slab  method. 
The  testing  Pfleiderer  doughing  machine  is  thoroughly  cleaned  by  making 
a stiff  dough  in  it,  and  thus  removing  anything  that  would  injure  the  colour. 
A dough  is  made  by  taking  30  grams  of  flour  and  15  grams  of  water,  and 
then  pinning  it  out  into  a tliin  sheet — say  three-sixteenths  of  an  inch  thick 
— on  a piece  of  glass.  This  is  allowed  to  dry  off  in  a dark  place  and  then 
read  just  like  the  Pekar  slab.  It  has  the  advantage  of  giving  a smooth 
surface  with  all  errors  due  to  tlie  “ grain  ” of  the  flour  eliminated  ; but  has 
the  disadvantage  that  tlie  degree  of  darkening  depends  somewhat  on  the 
thickness  of  the  slieet. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  713 

The  next  and  final  test  is  that  made  by  baking  the  loaf  and  then  observing 
the  colour  of  the  bread.  It  is  scarcely  necessary  to  point  out  to  bakers  that 
colour  is  influenced  by  the  kind  of  yeast  used  and  mode  of  working  ; but 
using  the  same  yeast,  it  was  thought  well  to  register  the  effect  produced  by 
the  mode  of  fermenting  employed,  and  especially  the  time  of  fermentation. 
A spring  American  bakers’  flour  was  first  made  into  an  off-hand  dough  in 
the  following  manner  : — 

10  lbs.  flour, 

5 lbs.  water  at  90°  F., 

IJ  oz.  compressed  yeast  (Delft  Pure),  and 
IJ  oz.  salt, 

were  taken  and  made  into  dough  at  5 p.m.  The  dough  was  then  maintained 
at  a temperature  of  80-82°  F.  during  the  whole  time  of  the  experiment. 
At  intervals  a 2 lb.  piece  was  taken,  moulded,  and  baked.  On  the  next 
morning  the  loaves  were  cut,  the  colour  examined,  and  also  the  total  acidity, 
reckoned  as  lactic  acid,  determined.  On  the  second  day  also  the  colour 
was  read,  a freshly-cut  surface  being  used  for  that  purpose.  The  following 
table  gives  the  results  obtained.  The  first  column  gives  the  number  of 
hours  after  setting  the  dough  until  the  loaf  was  placed  in  the  oven  ; the 
first  day’s  colour  readings  follow  in  the  second  column,  the  next  day’s  in  the 
third,  and  the  acidities  in  the  last  : — 


Tests  Bakers’  Flour — Off-hand  Dough. 


No. 

Houra. 

First  Day’s  Colour. 

Y.  R.  B. 

Second  Day’s  Colour. 

Y.  R.  B. 

Acidity 
per  cent. 

1 

4 

211 

L41 

0-30 

1-85 

L25 

0-16 

0-57 

2 

6 

L75 

L25 

018 

1-91 

MO 

0-26 

0-63 

3 

8 

L75 

100 

010 

1-85 

MO 

0-26 

0-66 

4 

10 

L75 

L20 

0-10 

L75 

L30 

0-26 

0-69 

5 

12 

1-70 

M5 

005 

1-66 

L20 

0-24 

0-73 

6 

131 

1-70 

L20 

0-30 

L75 

1-40 

0-30 

0-79 

Fermentation  had  not  proceeded  sufficiently  far  to  properly  raise  the 
first  loaf,  which  was  somewhat  close  and  heavy,  and  also  dark  in  colour  ; 
but  it  should  be  borne  in  mind  its  texture  could  scarcely  be  in  fairness  com- 
pared with  that  of  the  other  numbers  of  the  series.  The  last  showed  signs, 
but  only  slight,  of  darkening — due  doubtless  to  the  commencement  of 
those  changes  which  accompany  sourness.  The  loaves  Nos.  2 to  5 do  not 
vary  greatly  in  colour,  but  there  is  a slight  diminution  of  the  depth  of  tint. 
Taken  as  a whole,  this  series  darkened  before  the  second  day. 

In  another  series  of  tests  two  doughs  were  worked  with  a flour  ferment. 
The  one  was  from  a spring  American  patent  flour  ; the  second  from  a bakers’ 
grade  from  the  same  wheat.  The  following  quantities  were  in  each  case 
employed  : — 


J lb.  flour 

3 oz.  compressed  yeast  > Ferment. 

5 lbs.  (2  quarts)  water  at  102°  F.j 

9i  lbs.  flour  Dough. 

The  ferment  was  allowed  to  work  45  minutes  from  the  time  of  being 
set  ; then  the  dough  was  made,  and  one  loaf  immediately  taken.  This 
was  allowed  to  prove,  and  at  once  baked.  Loaves  were  taken  at  intervals 
as  shown  in  the  following  table,  in  which  is  also  given  the  colour  and  acidity 
both  on  the  first  and  second  day  after  baking.  It  should  be  added  that  the 
first  loaf  was  baked  at  about  9.15  p.m. 


714 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Tests  on  Bakers’  Flour — Flour  Ferment  and  Dough. 
{Same  sample  as  used  in  previous  series.) 


No. 

Hours. 

First  Day’s  Colour. 

Y.  R.  B. 

Acidity 
per  cent. 

Second  Day’s 

Y.  R. 

Colour. 

B. 

Acidity 
per  cent. 

1 

Immediate 

1-80 

115 

0-50 

0-65 

1-40 

0-96 

006 

0-59 

2 

2 hours 

1*65 

1*20 

0-40 

0-73 

1-48 

100 

004 

0-71 

3 

4 „ 

1-65 

1-30 

0-40 

0-72 

1-42 

100 

004 

0-90 

4 

6 

L90 

1-80 

0-60 

105 

1-60 

1-40 

005 

M2 

5 

71 

* 2 5’ 

2-20 

2-08 

0-75 

M7 

1-60 

1-45 

0-08 

1-27 

6 

94  „ 

2-22 

215 

0-75 

MO 

1-65 

1-40 

0-08 

1-34 

Remarks. 

No.  1.  Very  close  and  heavy. 

No.  2.  Sweet,  good  loaf. 

No.  3.  Colour  slightly  worse,  odour  faulty. 

No.  4.  Decidedly  sour,  rapid  darkening  in  colour  commenced. 

No.  5.  These  changes  intensified. 

No.  6.  These  changes  still  more  marked. 

The  colour  here  distinctly  fell  off,  with  increase  of  acidity,  a distinct 
difference  being  observed  even  between  Nos.  2 and  3.  The  off-hand  doughs 
were,  as  a series,  whiter  than  those  prepared  with  a ferment,  but  this  is 
probably  due  to  the  excessive  fermentation  in  the  latter  series,  which  was 
intentionally  pushed  to  an  extreme.  Taken  as  a whole  these  loaves  were 
distinctly  less  coloured  on  the  second  day. 

The  foUovdng  are  the  results  of  the  corresponding  series  of  tests  on  patent 
flour  : — 

Tests  on  Patent  Flour. 


No. 

Hours. 

First  Day’s  Colour. 

Y.  R.  B. 

Acidity 
per  cent. 

Second  Day’s  Colour. 

Y.  R.  B. 

Acidity 
per  cent. 

1 

Immediate 

1-45 

0-70  — 

0-29 

1-40 

0-72 

— 

0-32 

2 

2 hours 

1*40 

0-62  — 

0-35 

1-60 

0-73 

005 

0-37 

3 

4 „ 

1-30 

0-60  — 

0-50 

L32 

0-65 

006 

0-52 

4 

6 „ 

1-75 

0-98  — 

0-63 

1-60 

101 

— 

0-68 

5 

71 

'2 

1-70 

101  — 

0-70 

1-40 

0-90 

— 

0-73 

6 

9|  ,, 

1-70 

102  — 

0-75 

1-48 

0-93 

— 

0*82 

Remarks. 


No. 

First  Day. 

Second  Day. 

1. 

Close  and  heavy — Sweet 

Sweet. 

2. 

Bright  and  good  bloom — Sweet 

Sweet. 

3. 

Greyer,  very  little  different — Sweet, 
and  3 good  volume  . . 

Both  2]  j . . , 

1 Incipient  sourness. 

4. 

Smaller,  darker,  slightly  sour  . . 

. . Sour. 

5. 

Smaller,  darker,  sourer  . . 

. . Sour. 

6. 

Very  small,  dark,  very  sour 

. . Very  sour. 

Again,  with  an  increase  of  acidity,  there  is  also  a darkening  of  colour ; 
and  in  the  earlier  numbers  of  the  series  also  a darkening  on  the  second  day’s 
reading  as  compared  with  the  first.  There  is  a property  of  bread  colour  to 
which  attention  has  already  been  drawn  by  Abercromby,  which  property 
renders  comparison  difficult  both  to  the  eye  and  also  the  tintometer.  That 
property  is  “ a silky  texture  in  the  bread,  which,  by  reflecting  the  light, 
gives  an  appearance  of  better  colour.”  To  this  characteristic  the  author 
ventures  to  apply  and  appropriate  the  term  “ sheen.”  The  difficulty  is 
that  a loaf  looks  more  “ sheeny  ” in  one  position  than  another  ; not  only  may 


Tests  by  Various  Methods  on  the  Colour  of  Flour. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  715 


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716 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


two  observers,  tlie  one  looking  over  the  other’s  shoulder,  get  a different  im- 
pression, but  the  sheen  may  be  affected  even  by  slightly  turning  or  altering 
the  position  of  the  loaf.  One  reason  why  the  patent  flour  breads  suffer  in 
colour  on  the  second  day  is  the  loss  of  brilliance  or  sheen. 

The  table  on  page  715  gives  the  results  of  examining  a number  of  flours 
for  colour  by  the  various  methods  described. 

In  every  case  the  order  of  the  substances  as  they  appeared  to  sight  is 
given,  as  well  as  the  reading  by  the  tintometer  ; between  these  there  are 
but  few  discrepancies,  and  these  mostly  occur  in  the  case  of  bread,  where  the 
disturbing  influence  of  irregular  surface  and  scattered  reflection  of  light 
acts  most  powerfully.  But  even  in  these  the  divergence  is  not  great.  The 
tintometer  reading  is  probably  the  truer  register  of  absolute  colour,  the  dis- 
turbing effect  of  side  reflections,  etc.,  being  practically  entirely  counter- 
acted. But  the  public  does  not  view  bread  through  a tintometer  as  a pre- 
liminary to  purchase,  and  hence  a doubt  arises  as  to  which  is  the  most 
trustworthy  baker’s  reading,  that,  or  the  general  effect  on  the  eye.  A point 
of  more  importance  is  the  relationship  existing  between  the  various  modes 
of  judging  colour  of  flour,  and  the  colour  of  the  resulting  bread.  In  the 
series  of  results  just  tabulated,  the  colour  of  the  dry  flour  agrees  most  closely 
with  that  of  the  baked  loaves  ; while,  contrary  to  expectation,  there  is 
considerable  discrepancy  between  the  colour  of  the  dough  and  that  of  the 
bread.  It  should  be  noted  that  if  the  flours  (which  were  all  American)  be 
divided  into  the  two  classes  of  spring  and  winter,  many  of  the  differences 
disappear.  Although  a good  many  results  are  here  accumulated,  they  do 
not  afford  sufficient  data  on  which  to  generalise,  but  they  do  show  the  extent 
of  agreement  and  disagreement  between  various  methods  of  testing  flour 
for  colour  in  common  employment. 


800.  Effect  of  Age  on  Flours. — The  experiments  set  forth  in  the  table  on 
page  717  were  made  in  order  to  determine  the  effect  of  age  on  American 
flours.  All  the  tests  were  made  at  various  times  on  14-lb.  samples,  stocked 
meantime  in  close  textured  canvas  bags.  The  flrst  tests  were  made  on  the 
arrival  of  the  flours  in  this  country  in  October  ; the  second  series  after  the 
lapse  of  three  months,  in  January  ; and  the  third  after  the  expiration  of 
another  two  months,  in  March.  The  colour  on  dry  flour,  wet  gluten,  and 
water  absorption  by  viscometer  were  in  each  case  determined. 

With  increase  of  age  a slight,  but  only  a slight,  amount  of  bleaching 
is  observed.  In  connexion  with  this,  it  will  be  of  interest  to  note  the  dif- 
ference in  colour  between  a sample  of  flour  by  which  purchase  was  made  on 
Mark  Lane,  and  the  colour  of  bulk  when  delivered  some  weeks  later.  The 
seller  alleged  that  the  difference  in  colour  between  bulk  sample  and  selling 
sample  was  due  to  bleaching  of  the  latter  in  the  interval  between  date  of 
purchase  and  arrival  of  the  flour 


Colour  of  Sample. 

Dry  Flour  . . . . 010  Y.  -f  0 01  R. 

Pekarised  Flour  . . 1’32  Y.  -f-  0*50  R. 

Dough,  through  glass  . . 1-10  Y.  + 0-60  R. 


Bulk. 

0-32  Y.  -f  0 09R. 
2-20  Y.  -f  0-90  R. 
L50  Y.  -f-0-90R. 


Comparing  the  above  results  with  the  amount  of  bleaching  on  authentic 
samples,  comment  is  unnecessary. 

Tlie  amount  of  gluten  and  also  water-absorbing  power  by  viscometer 
show  generally  signs  of  slight  diminution. 

801.  Changes  undergone  by  Flour  Samples  during  Storage,  Jago  and 

Ellis. With  the  view  of  obtaining  definite  information  as  to  the  changes 

which  flour  samples  undergo  during  keeping,  the  following  investigation 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  717 


No.  1. 

Effect  of  Age  on  Flours. 

Bakers’  Flour  from  Duluth  Wheat. 

„ 2. 

Patent 

„ 3. 

Bakers’ 

,,  Manitoban  Wheat. 

„ 4. 

Patent 

„ 5. 

Bakers’ 

,,  Indiana  Winter  Wheat. 

„ 6. 

Patent 

55  55 

„ 7. 

Bakers’ 

,,  Ohio  Winter  Wheat. 

„ 8. 

Patent 

55  55  55 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

1 

Colour. 

New  ..  .. 

0-30 

0-21 

0-27 

1 0-22 

0-20  1 

0-07 

0-18 

0-06 

0-07 

0 04 

0-06 

: 0-06 

0-03  j 

0-02 

003 

0-02 

Three  months  old 

0-29 

0-07 

0-22 

0-02 

0-27 

0-06 

, 0-22 

1 0-04 

0-16 
0-03  1 

0-06 

0-02 

0-16 

0-02 

0.08 

0-01 

Five  months  old  -j  ^ 

0-28 

0-07 

0-21 

002 

0-26 
0-04  1 

0-22 

0-04 

0-16  ; 
0-03 

0-06 

0-02 

0-14 

0-02 

0-06 

0-01 

Wet  Gluten. 

1 

Xew  . . . . . . 

44-0 

42-0 

44-5 

39-0 

37-0  f 

28-9 

33-7 

31-8 

Three  months  old 

43-7 

41-7 

37-4 

36-2 

30-6 

291 

33-3 

30-2 

Five  months  old 

43-2 

41-2 

35-7 

35-0 

30-1 

28-9 

32-7 

30-3 

Water  Absorption. 

Xew 

69-5 

68-0 

66-0 

63-5 

59-0 

530 

56-0 

57-5 

Three  months  old 

68 -5 

67-0 

67-5 

66-0 

60 -0  i 

55-0 

56-0 

55-5 

Five  months  old 

66-0  ’ 

62-0 

1 

66-0 

63-0 

55-0 

51-0 

56-0  1 

55-0 

was  made  by  one  of  the  authors  in  conjunction  with  Mr.  Ellis,  a student  in 
his  laboratory,  and  a practical  baker  of  long  experience.  In  the  month  of 
February  sample  half-sacks  of  new  flour  were  kindly  furnished  by  a number 
of  millers. 

The  various  flours  received  the  following  numbers,  a short  description  of 
each  being  given  : — 

1.  Top  Grade  Soft  Coloury  Flour. 

2.  Household  Grade  Soft  Coloury  Flour. 

3.  Top  Grade  Hungarian  Flour. 

4.  Low  Grade  Hungarian  Flour. 

5.  Top  Grade  Strong  Flour. 

6.  Medium  Grade  Strong  Flour. 

7.  Household  Grade  Strong  Flour. 

8.  Top  Grade  Medium  Strength  Flour. 

9.  Medium  Gra,de  Medium  Strength  Flour. 

Each  bag  of  flour  was  weighed  off  into  7 lb.  sample  bags,  made  of  double 
thickness  of  fine  cotton  material.  One-half  the  number  was  stored  in  a 
cold  room  subjected  to  the  ordinary  changes  of  climate  in  the  matters  of 
temperature  and  moisture.  The  remainder  Avere  stored  in  a flour  loft  over 
a.  bakery,  where  the  temperature  ranged  somewhat  high.  Beyond  the 
protection  afforded  by  the  bags  themselves,  the  flours  were  not  screened  from 
the  action  of  light,  but  were  not  exposed  to  direct  sunshine.  In  addition 
to  the  7 lb.  samples,  a 1 lb.  sample  of  each  flour  was  placed  in  a double 
thickness  bag,  and  this  in  turn  stored  in  a tin  canister,  with  tightly-fitting 
lid.  On  March  2 these  arrangements  were  completed,  and  the  flours  Avere 


718 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


then  systematically  examined,  and  afterwards  periodically  tested  on  the 
dates  given  in  subsequent  tables. 

The  following  determinations  were  made  on  each  flour  : — 

Percentage  of  moisture. 

Percentage  of  wet  and  dry  gluten. 

Water  absorption  by  the  viscometer. 

Colour  on  dry  flour,  and  wetted  and  dried  (Pekarised)  flour,  by  tinto- 
meter and  by  comparison  with  standard  slabs. 

Baking  tests  on  560  grams  (approximately  20  ounces)  of  flour. 

The  moisture  was  determined  in  the  usual  manner.  The  glutens  were 
determined  in  duplicate,  and  checked  by  a fresh  test  in  any  cases  of  dis- 
crepancy. The  water  absorption  is  in  each  case  the  mean  of  several  deter- 
minations, and  the  results  as  gained  by  the  viscometer,  checked  by  careful 
hand  examination  of  the  dough  itself.  The  colour  of  flours,  and  also  breads, 
was  read  as  accurately  as  possible  by  the  tintometer  ; in  each  case  the  colour 
was  checked  by  comparing  it  with  a tint  which  was  decidedly  lighter,  and 
also  with  one  which  was  perceptibly  darker,  thus  getting  not  only  a reading 
which  appeared  to  match  the  flour,  but  also  one  which  was  too  dark  and 
another  which  was  too  light.  These  readings  were  usually  about  OT  lighter 
or  darker  than  the  matching  tint. 

Thus  in  one  case  0*75  yellow  -f  0-60  red. — Too  light. 

0*90  yellow  + 0-75  red. — Match. 

0-95  yellow  + 0*80  red. — Too  dark. 

In  the  baking  tests  the  weight  of  the  dough,  yield  of  bread,  colour, 
general  appearance,  and  working  characteristics,  are  in  each  case  noted. 
The  yield  of  bread  is  that  judged  to  result  when  cottage  dough  is  made, 
and  is  calculated  from  the  actual  weight  of  fermented  dough.  It  may  be 
mentioned  that  in  all  small  tests  the  apparent  yield  is  greater  than  the  same 
flour  gives  on  the  commercial  scale. 

In  the  following  tables  are  given  the  results  of  the  various  tests  made  on 
each  flour. 

The  viscometer  results  are  given  in  quarts  per  sack.  The  moisture,  wet, 
dry,  and  true,  gluten  are  in  percentages  of  the  flour. 

The  water  used  in  dough-making  is  calculated  to  quarts  per  sack.  The 
weight  of  fermented  dough  is  calculated  to  lbs.  per  sack,  and  from  this  is 
calculated  the  number  of  quarterns  per  sack,  dough  being  weighed  off 
at  4 lbs.  6 oz. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  719 


No.  1 Flour. 


Cold  Storage. 


Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weiglit  of 
Fermented 
Dough. 
Lbs. 

Quarterns 

per 

Sack. 

Arrival. 

57 

15-33 

38-5 

13-2 

51 

420-0 

96-6 

2nd.  week 

58 

14-75 

35-7 

12-2 

10-7 

54 

425-0 

97-7 

4th.  ,, 

57 

15-34 

38-7 

13-0 

— 

56 

425-0 

97-7 

6th.  ,, 

55 

15-30 

38-0 

13-1 

— 

57 

430-0 

98-9 

10th. 

52 

15-5 

35-9 

12-2 

— 

52 

410-0 

94-3* 

13th.  „ 

55 

15-4 

35-8 

12-3 

— 

52 

407-5 

93-7 

Hot 

' Storage. 

Arrival  . . 

57 

15-33 

38-5 

13-2 

51 

420-0 

96-6 

1st.  week 

69 

12-91 

37-0 

12-9 

— 

53 

417-5 

95-9 

3rd.  „ 

70 

11-80 

39-0 

13-0 

10-2 

55 

422-5 

97-1 

5th. 

73 

10-25 

38-0 

13-7 

— 

59 

430-0 

98-9 

7th.  „ 

75 

9-8 

38-0 

13-7 

— 

66 

450-0 

103-5 

11th.  „ 

75 

8-9 

38-0 

12-33 

— 

66 

470-0 

108-1 

14th.  „ 

69 

8-95 

38-0 

1 

12-32 

1 

65 

1 

447-5 

102-9 

Colour  by  Tintometer. 


Cold  Storage. 


Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Arrival 

0-28 

0-21 

0-80 

0-81 

1-7 

0-81 

2nd.  week  . . 

0-18 

0-03 

0-90 

0-80 

1-6 

0-85 

4th.  ,, 

0-12 

0-06 

0-50 

0-40 

1-4 

0-74 

6th.  „ . . 

0-14 

0-05 

0-80 

0-50 

1-3 

0-71 

10th.  „ 

0-20 

0-19 

0-30 

0-55 

1-2 

0-84 

13th.  ,, 

0-20 

0-17 

0-80 

0-58 

1-1 

0-86 

Hot  Storage. 


Arrival 

0-28 

0-21 

0-80 

0-81 

1-7 

0-81 

1st.  week  . . 

0-22 

0-12 

0-73 

0-80 

1-4 

0-81 

3rd.  „ 

1 0-29 

0-07 

0-90 

0-80 

1-3 

0-76 

5th.  „ 

0-22 

0-06 

0-80 

0-70 

1-2 

0-74 

7th.  „ 

0-23 

0-07 

0-60 

0-54 

1-4 

0-80 

11th.  „ 

0-20 

0-10 

0-80 

0-59 

1-4 

0-90 

14th.  „ 

0-20 

0-14 

0-85 

0-58 

1-4 

1-00 

* This  one  gone  musty. 


720 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


■No.  2 Flour. 


Cold  Storage. 


Visco- 

meter, 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Fermented 
Dough. 
Lbs. 

1 

Quarterns  j 
per 
Sack. 

Arrival  . . 

59 

' 14-73 

43-7 

14-3 

! _ 

53 

417-5 

96-0 

2nd.  week 

59 

14-15 

38-5 

13-7 

11-8 

55 

4240 

9'7-5  ' 

4th.  „ 

59 

15-03 

45-3 

15-3 

— 

56 

430  0 

98-9  ! 

6th.  „ 

59 

15-10 

45-0 

15-4 

— 

56 

427-5 

98-3  1 

10th.  ,, 

57 

14-9 

44-3 

14-0 

— 

56 

425  0 

97-7  ' 

13th.  „ 

57 

1 13-95 

1 

47-8 

14-5 

1 

50 

415-0 

95-4  ! 

Hoi 

' Storage. 

i 

Arrival  . . 

59 

14-73 

43-7 

14-3 

53 

417-5 

96-0 

1st.  week 

60 

12-28 

42-0 

14-4 

— 

55 

422-5 

97-1  ^ 

3rd.  „ 

64 

11-45 

43-0 

15-4 

12-6 

58 

4250 

97-7  : 

5th.  ,, 

67 

10-20 

43-2 

14-7 

— 

60 

432-5 

99-4 

7th.  ,, 

68 

10-0 

46-2 

15-0 

■ — 

60 

4320 

99-4 

I 11th.  „ 

68 

9-5 

43-0 

15-1 

■ — - 

64 

457-5 

105-2 

14th.  „ 

70 

7-85 

39-35 

14-2 

- — ■ 

64 

440  0 

101-2 

i 

Colour  by  Tintometer. 

Coll 

1 Storage. 

Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

1 Arrival 

0-30 

0-22 

0-80 

0-83 

1-4 

i 

0-82 

1 2nd.  week  . . 

0-22 

0-10 

0-80 

0-60 

1-5 

0-88  i 

! 4th.  „ 

0-11 

0-08 

0-80 

0-62 

1-6 

0-91  ; 

1 6th.  „ . . 

0-17 

0-07 

0-89 

0-69 

1-3 

0-83  ' 

10th.  ,, 

0-21 

0-08 

0-90 

0-70 

1-3 

0-82 

13th.  „ 

0-21 

0-09 

0-90 

0-80 

1-2 

1-0  ! 

1 

[ 

Hot  Storage. 


Arrival 

0-30 

0-22  ' 

0-80 

0-83 

1-4 

0-82  I 

1st.  week  . . 

0-22 

0-18  ' 

0-71 

0-80  ! 

1-4 

0-82  1 

3rd.  „ 

0-25 

0-10  1 

0-80 

0-81 

1-7 

0-79  ! 

5th.  ,, 

0-25 

0-08 

0-89 

0-74 

1-6 

0-78  1 

7th.  ,, 

0-26 

, 0-08 

0-80 

0-59 

1-5 

0-92  1 

11th.  „ 

0-22 

0-12 

j 0-93 

0-65 

1-5 

0-98  ! 

14th.  „ 

0-20 

0-16 

1 0-90 

0-60 

1-3 

1-0 

COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  721 


No.  3 Flouk. 


Cold  Storage, 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Fermented 
Dough. 
Lbs. 

Quarterns 

per 

Sack. 

Arrival  . . 

63 

12-81 

34-8 

12-3 

1 

61 

4350 

100-0 

2nd.  week 

65 

11-92 

31-5 

10-2 

9-5 

63 

442-5 

101-7 

4th.  „ 

63 

13-75 

36-6 

11-9 

— 

67 

452-5 

104-0 

6th.  ,, 

63 

14-40 

35-0 

11-9 

— 

67 

452-5 

104-0 

lOth.  „ 

60 

12-6 

34-9 

11-0 

■ — 

60 

431  0 

99-1 

13th.  „ 

63 

13-2 

35-0 

10-75 

■ — 

56 

4250 

97-7 

Hot  Storage. 

Arrival  . . 

63 

12-81 

34-8 

12-3 

61 

435 

100-0 

1st.  week 

70 

11-40 

32-5 

11-3 

■ — 

65 

446 

102-5 

3rd.  ,, 

71 

11-30 

32-0 

10-5 

9-0 

65 

447 

106-9 

5th.  „ 

72 

9-16 

36-0 

12-1 

■ — 

71 

462 

106-3 

7th.  „ 

72 

9-05 

37-1 

12-8 

— 

73 

469 

107-8 

11th.  ,, 

73 

8-9 

36-2 

11-6 

— 

73 

469 

107-8 

14th.  ,, 

74 

8-07 

34-5 

11-09 

— 

73 

472 

108-6 

Colour  by  Tintometer. 

Cold  Storage. 

Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

! 

Red, 

Arrival 

0-30 

0-10 

1-0 

0-80 

1-4 

1-0 

2nd.  week 

0-11 

0-10 

0-70 

0-53 

1-5 

0-89 

4th.  ,, 

0-10 

0-06 

0-70 

0-50 

1-6 

0-90 

6 th.  „ 

0-14 

0-05 

0-80 

0-45 

1-3 

0-56 

10th.  „ 

0-14 

0-08 

0-80 

0-60 

1-3 

0-80 

13th.  „ 

0-12 

0-09 

0-80 

0-60 

1-35 

0-82 

Hot 

Storage. 

Arrival 

0-30 

0-10 

1-0 

0-80 

1-4 

1-0 

1st.  week 

0-20 

0-11 

0-80 

0-63 

1-4 

0-90 

3rd.  ,, 

0-20 

0-04 

0-88 

0-50 

1-5 

0-72 

5th.  ,, 

0-20 

0-08 

0-90 

0-50 

1-4 

0-73 

7th.  „ 

0-20 

0-08 

1-1 

0-92 

1-46 

0-60 

11th.  „ 

0-20 

0-09 

0-75 

0-54 

1-3 

0-81 

14th.  ,, 

0-20 

0-09 

0-80 

0-56 

1-3 

0-81 

722 


THE  TECHNOLOGY  OF  BREAD-MAKING. 
No.  4 Flour. 


Cold  Storage. 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Fermented 
Dough. 
Lbs. 

Quarterns 

1 per 
Sack. 

Arrival  . . 

72 

12-65 

30-3 

11-6 

70 

460 

i 

105-8 

2nd.  week 

74 

12-56 

32-2 

11-0 

10-6 

70 

460 

105-8 

4th.  „ 

73 

14-77 

35-4 

11-9 

— 

72 

462 

106-2 

! 6th, 

72 

14-60 

34-0 

11-8 

— 

72 

- 466 

107-1 

10th, 

71 

14-9 

34-5 

11-8 

— 

69 

451 

103-7 

13th  ., 

* 

Hot  Storage. 

Arrival  . . 

72 

12-65 

30-3 

11-6 

700 

460  0 

105-8 

3rd.  week 

75 

10-0 

34-0 

11-7 

— 

720 

471-5 

108-4 

5 th.  , 

78 

11-0 

33-0 

11-9 

11-1 

720 

471  0 

108-2 

7th.  „ 

80 

9-15 

34-9 

12-6 

. — 

72-75 

4660 

107-1 

nth.  „ 

81 

8-9 

35-0 

12-9 

— 

730 

4690 

107-8 

14th  , 

81 

8-5 

34-0 

12-5 

• — 

770 

4750 

109.2 

Colour  by  Tintometer. 


Cold  Storage. 


Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Arrival 

0-29 

0-20 

1-0 

0-99 

1-3 

1-0 

2nd.  week  . . 

; 0-10 

0-11 

0-92 

0-71 

1-5 

1-2 

4th.  ,, 

0-10 

0-07 

0-90 

0-76 

1-4 

0-90 

6th.  „ 

0-14 

0-08 

1-0 

0-84 

1-4 

0-60 

lOtli.  „ 

0-24 

0-23 

1-0 

0-70 

1-4 

0-80 

13th.  „ . . 

* 

— 

— 

— 



— 

' Hot  Storage. 

1 

Arrival 

0-29 

0-20 

1-0 

0-99 

1-3 

1-0 

1st.  week  . . 

1 0-25 

0-20 

1-0 

0-80 

1-3 

1-0 

3rd.  „ 

! 0-29 

0-10 

0-96 

0-70 

1-5 

1-0 

5th.  „ 

0-29 

0-09 

0-98 

0-89 

1-4 

1-0 

7th.  „ 

1 0-21 

0-09 

1-0 

0-92 

1-4 

0-60 

11th.  „ 

1 0-22 

0-23 

0-85 

0-55 

1-5 

1-0 

14th 



— 

Too  musty  and  dark  for  baking  purposes. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  723 


No.  5 Flour. 


Cold  Storage. 


Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Fermented 
Dough. 
Lbs. 

Quarterns 

per 

Sack. 

Arrival  . . 

68 

1306 

40-2 

13-3 

63 

442-5 

101-7 

2nd.  week 

69 

130 

37-8 

14-5 

12-9 

64 

442-5 

101-7 

4th.  „ 

68 

1410 

46-2 

14-8 

■ — 

65 

4470 

102-8 

6th.  „ 

67 

13-65 

46-0 

14-8 

— 

65 

4510 

103-7 

10th.  ,, 

63 

13-9 

45-0 

13-35 

— 

61 

4390 

100-9 

13th.  „ 

65 

13-8 

45-7 

13-25 

— 

59 

427-5 

98.3 

Hot  Storage. 

Arrival  . . 

68 

13-06 

40-2 

13-3 

630 

442-5 

101-7 

1st.  week 

68 

11-70 

41-0 

14-0 

— 

650 

448-5 

103-6 

3rd.  „ 

70 

11-65 

44-0 

15-5 

12-1 

68-0 

4550 

104-6 

5th.  ,, 

73 

9-75 

44-5 

15-4 

— 

69-5 

461  0 

107-8 

7th.  „ 

73 

8-2 

47-3 

15-7 

— 

70-0 

4560 

104-8 

11th.  „ 

75 

8-0 

44-5 

14-7 

— 

710 

4660 

107-1 

14th.  „ 

75 

8-5 

44-45 

14-4 

— 

710 

4650 

107-0 

Colour  by  Tintometer. 


Cold  Storage. 


Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

! Red. 

1 

Arrival 

0-30 

0-21 

0-87 

0-70  1 

2-0 

0-81 

2nd.  week  . . 

0-27 

0-09 

0-90 

0-80  ! 

1-3 

0-80 

4th.  ,, 

0-12 

0-06 

0-50 

0-40 

2-0 

1-2 

6th.  ,, 

0-14 

0-06 

0-99 

0-75 

1-4 

0-73 

10th.  „ . . 

0-20 

0-81 

1-0 

0-80 

1-4 

0-88 

13th.  ,, 

0-27 

1-0 

0-98 

0-80 

1-38 

0-86 

Hot  Storage. 


Arrival 

0-30 

0-21 

0-87 

0-70 

2-0 

0-81 

1st.  week 

0-29 

0-12 

1-3 

0-91 

1-5 

0-88 

3rd.  „ 

0-28 

0-08 

1-2 

0-85 

1-4 

0-74 

5th.  ,, 

0-21 

0-10 

1-1 

0-70 

1-2 

0-70 

7th.  „ 

0-20 

0-09 

1-04 

0-56 

1-4 

0-59 

nth.  „ 

0-23 

0-10 

0-91 

0-68 

1-4 

0-85 

14th.  „ 

0-20 

0-10 

0-93 

0-64 

1-3 

0-85 

724 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  6 Flour. 


Cold  Storage. 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Dough 
Lbs. 

per  Sack. 

Quarterns 

per 

Sack. 

Arrival  . ; 

70 

12-67 

42-3 

13-5 

64 

441-5 

101-5 

2nd.  week 

70 

13-2 

40-5 

14-5 

12-5 

64 

4450 

102-3 

4th.  „ 

66 

13-75 

40-1 

12-8 

— 

64 

440  0 

101-2 

6th.  ,, 

67 

14-28 

41-0 

12-9 

— 

64 

4400 

101-2 

10th.  „ 

68 

14-0 

41-5 

12-7 

— 

59 

4330 

. 99-5 

13th.  „ 

65 

13-5 

42-5 

12-8 

— 

61 

437-5 

100-6 

Hot  Storage. 


Arrival  . . 

70 

12-67 

42-3 

13-5 

64 

441-5 

101-5 

1st.  week 

70 

10-72 

44-5 

13-1 

— 

64 

445.0 

102-3 

3rd.  „ 

71 

13-21 

43-0 

15-0 

12-0 

68 

4560 

104-8 

5th.  ,, 

74 

10-26 

43-0 

14-0 

— 

69 

4580 

105-3 

7th.  „ 

76 

9-34 

46-0 

14-0 

— 

69 

457-5 

105-2 

nth.  „ 

76 

9-15 

45-3 

14-8 

■ — 

74 

4750 

109-2 

14th.  „ 

76 

8-60 

44-1 

14-26 

— 

76 

480-0 

110-4 

Colour  by  Tintometer. 


Cold  Storage. 


! 

Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

1 

Yellow. 

Red. 

Arrival 

0-30 

• 0-22 

0-92 

0-70 

1-7 

0-81 

2nd.  week  . . 

0-30 

0-06 

0-90 

0-81 

1-4 

0-90 

4th.  ,, 

0-22 

0-06 

0-84 

0-66 

1-4 

0-80 

6th.  „ . . 

0-17 

0-06 

0-90 

0-64 

1-38 

0-88 

10th.  „ . . 

0-26 

0-08 

1-01 

0-60 

1-35 

0-87 

13th. 

0-26 

0-08 

1 0-95 

0-70 

1-34 

0-80 

Hot  Storage. 

Arrival 

0-30 

0-24 

0-92 

0-70 

1-7 

0-81 

1st.  week  . . 

0-30 

0-14 

1-2 

0-99 

1-4 

0-76 

.3rd.  „ 

0-34 

0-10 

1-2 

0-90 

1-4 

0-76 

5th.  ,, 

0-.30 

0-10 

1-1 

0-70 

1-3 

0-71 

7th.  „ 

0-22 

0-09 

1-1 

0-70 

1-5 

0-59 

nth.  „ 

0-22 

0-09 

0-94 

0-88 

1-42 

0-80 

14th.  ,. 

0-22 

0-09 

1 0-90 

0-65 

1-43 

0-80 

COMMERCIAL  TESTING  OP  WHEATS  AND  PLOURS.  725 


No.  7 Ploue. 


Cold  Storage. 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Fermented 
Dough. 
Lbs. 

Quarterns 

per 

Sack. 

Arrival  . . 

69 

12-61 

45-1 

14-6 

67 

446-5 

102-6 

2nd.  week 

69 

13-05 

44-0 

15-0 

13-4 

67 

469-5 

104-0 

4th.  ,, 

69 

14-11 

47-2 

15-1. 

• — 

65 

4500 

103-5 

6th.  ,, 

70 

14-56 

47-0 

15-1 

— 

63 

442-5 

101-7 

loth.-  „ 

66 

14-2 

46-1 

15-0 

■ — 

63 

442-5 

101-7 

l-3th.  „ 

68 

13-82 

45-0 

14-8 

— 

64 

4450 

101-9 

Hot  Storage. 

Arrival  . . 

69 

12-61 

45-1 

14-6 

670 

446-5 

102-6 

1st.  week 

69 

10-72 

43-0 

14-6 

• — 

670 

454-5 

104-5 

3rd.  „ 

70 

13-21 

43-8 

14-7 

14-0 

710 

465  0 

106-9 

5th.  ,, 

73 

10-26 

46-1 

15-3 

— 

71-5 

464  0 

106-7 

7th.  „ 

75 

9-34 

48-2 

15-4 

• — 

720 

465  0 

106-9 

11th.  „ 

75 

9-0 

47-3 

15-0 

— 

710 

460  0 

105-8 

14th.  ,, 

76 

8-20 

44- 1 

15-75 

— 

74-0 

472-5 

108-6 

Colour  by  Tintometer. 

Cold  Storage. 

Dry  Flour. 

P6karised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Arrival 

0-38 

0-30 

1-07 

0-90 

1-6 

1-1 

2nd.  week  . . 

0-31 

0-26 

0-90 

0-80 

1-8 

0-82 

4th.  ,, 

0-30 

0-20 

1-0 

0-80 

1-6 

0-91 

6th.  ,, 

0-30 

0-20 

1-01 

0-90 

1-5 

0-96 

10  th.  ,, 

0-27 

0-22 

1-03 

0-80 

1-4 

0-88 

13th.  „ 

0-28 

0-20 

1-1 

0-80 

1*7 

1-2 

Hot  Storage. 

Arrival 

0-38 

0-30 

1-07 

0-90 

1-6 

1-1 

1st.  week 

0-31 

0-20 

1-3 

1-0 

1-8 

1-1 

3rd.  „ 

0-30 

0-19 

1-5 

1-0 

1-9 

0-79 

5th.  ,, 

0-30 

0-19 

1-2 

0-70 

1-4 

0-75 

7th.  „ 

0-28 

0-10 

1-0 

0-76 

1-5 

0-60 

11th.  „ 

0-21 

0-12 

1-0 

0-70 

1-53 

0-80 

14th.  „ 

0-27 

0-10 

1-0 

0-76 

1-5 

0-90 

726 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  8 Floue. 


Cold  Storage. 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Dough. 
Lbs.  per 
Sack. 

1 

1 

Quarterns  i 
per 

Sack.  I 

1 

Arrival  . . 

62 

1440 

40-2 

13-4 

56 

426-0 

97-8 

2nd.  week 

64 

13-70 

35-1 

13-1 

12-9 

58 

430-0 

98-9  j 

4th.  „ 

62 

1408 

40-3 

14-2 

— 

58 

437-5 

100-6  ! 

6th.  ,, 

63 

13-56 

40-0 

14-5 

— 

60 

435-0 

100-5  ; 

10th.  ,, 

59 

14-0 

39-5 

14-0 

— 

69 

435-0 

100-5  1 

13th.  „ 

61 

14-0 

37-4 

13-2 

— 

56 

425-0 

97-7 ; 

Hoi 

' Storage. 

i 

Arrival  . . 

62 

14-40 

40-2 

13-4 

56 

426 

97-8 

1st.  week 

65 

10-65 

40-5 

14-5 

12-47 

58 

434 

99-8 

3rd.  „ 

68 

11-65 

39-0 

13-3 

— 

57 

*426 

98-9 

5th.  ,, 

71 

9-10 

40-0 

14-7 

— 

58 

449 

103-3 

7th.  „ 

72 

9-1 

40-0 

14-5 

— 

66 

451 

103-7 

nth.  „ 

73 

9-05 

40-2 

14-1 

— 

69 

469 

107-8  ; 

14th.  ,, 

73 

7-25 

41-0 

13-85 

— 

69 

455 

104-6 

COLOUE  BY 

Tintometee. 

Cold  Storage.  ’ 

Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Eed. 

Yellow. 

Eed. 

Yellow. 

Eed.  ! 

Arrival 

0-34 

0-20 

0-80 

0-70 

1-9 

1-1 

2nd.  week  . . 

0-20 

0-11 

0-71 

0-60 

1-6 

0-90  ; 

4 th. 

0-18 

0-08 

0-60 

0-53 

1-4 

0-71 

6 th.  ,, 

0-20 

0-09 

0-84 

0-51 

1-5 

0-60  i 

10  th. 

0-28 

0-10 

0-84 

0-70 

1-4 

0-85  S 

13th. 

0-21 

0-10 

0-80 

0-69 

1-2 

0-80  i 

Hot  Storage.  i 

Arrival 

0-34 

0-20 

0-80 

0-70 

1-9 

1-1  : 

1st.  week 

0-30 

0-17 

1-5 

0-99 

1-6 

0-89 

3rd.  ,, 

0-20 

0-12 

1-3 

0-90 

1-3 

0-80  • 

5 th.  ,, 

0-21 

0-11 

0-90 

0-72 

1-3 

0-77 

7th.  ,, 

0-28 

0-10 

0-74 

0-50 

1-4 

0-68 

11th.  „ 

0-21 

0-11 

0-70 

0-55 

1-4 

0-67  ' 

14th.  ,, 

0-21 

0-10 

0-75 

0-55 

1-15 

0-75  1 

* This  dough  was  too  tight. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  727 


No.  9 Flour. 


Cold  Storage. 

Visco- 

meter. 

Moisture. 

Wet 

Gluten. 

Dry 

Gluten. 

True 

Gluten. 

Water  used 
in  Doughing. 
Quarts 
per  Sack. 

Weight  of 
Dough. 
Lbs.  per 
Sack. 

1 

Quarterns 

per 

Sack. 

Arrival  . . 

61 

14-52 

41-5 

14-3 

t 

550 

424-0 

97-5 

2nd.  week 

62 

14-03 

39-0 

14-6 

12-8 

570 

426-0 

97-9 

4th.  „ 

1 63 

14-82 

45-1 

15-6 

— 

60  0 

435-0 

100-0 

6th.  ,, 

64 

14-81 

45-0 

15-7 

■ — 

56-5 

412-5 

94-8 

10th.  „ 

61 

14-7 

43-2 

14-6 

— • 

560 

425-0 

97-7 

13th.  „ 

62 

13-63 

38-55 

14-65 

— 

56-0 

427-5 

98-3 

Hot  Storage. 

Arrival  . . 

61 

14-52 

41-5 

14-3 

55 

424-0 

97-5 

1st.  week 

68 

11-02 

40-5 

14-0 

13-50 

57 

434-0 

99-8 

3rd.  ,, 

70 

11-07 

40-0 

14-0 

— 

59 

439-0 

100-9 

5th.  ,, 

73 

9-20 

42-5 

15-2 

— 

63 

435-0 

100-5 

7th.  „ 

72 

8-0 

41-1 

15-2 

— 

66 

451-0 

103-7 

11th.  „ 

72 

7-9 

41-7 

15-0 

— 

68 

477-0 

109-7 

14th.  „ 

72 

8-8 

42-75 

15-03 

— 

68 

452-5 

104-7 

Colour  by  Tintometer. 


Cold  Storage. 


Dry  Flour. 

Pekarised. 

Crumb. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Arrival 

0-30 

0-18 

0-90 

0-70 

1-3 

0-90 

2nd.  week  . . 

0-24 

0-12 

0-90 

0-72 

1-4 

0-91 

4th. 

0-20 

0-10 

0-90 

0-71 

1-4 

0-70 

6th.  ,, 

0-21 

0-10 

0-90 

0-70 

1-5 

0-90 

10th.  ,, 

0-29 

0-08 

0-86 

0-70 

1-5 

0-86 

13th.  „ . . 

0-20 

0-09 

! 

0-86 

0-68 

1-3 

0-95 

Hot  Storage. 

Arrival 

0-30 

0-18 

0-90 

0-70 

1-3 

0-90 

1st.  week  . . 

0-34 

0-20 

1-4 

1-0 

1-6 

1-0 

3rd.  ,, 

0-22 

0-20 

1-2 

0-90 

1-5 

0-72 

5th.  ,, 

0-20 

0-10 

0-90 

0-70 

1-5 

0-76 

7th.  „ 

0-28 

0-10 

0-78 

0-52 

1-5 

0-59 

nth.  „ 

0-23 

0-10 

0-86 

0-70 

1-5 

0-84 

14th.  ,, 

0-24 

0-13 

0-80 

0-69 

1-3 

0-95 

I 


728 


THEiTECHNOLOGY^OF  BREAB-MAKING. 

The  lb.  samples  stored  in  tins  were  examined  on  June  29. 

In  the  following  tables  are  given  the  percentages  of  gluten  and  moisture, 
water-absorption  by  viscometer,  and  colour  of  dry  and  Pekarised  flour  respec- 
tively, on  arrival,  at  end  of  first  week  and  last  w^eek  (approximately  four 
m onths). 


Comparison  of  Flours  on  Arrival,  First,  and  Last  Week. 


Glutens. 


Hot  Storage. 

Cold  Storage. 

Tinned  Store. 

Arrival. 

First  Week. 

Last  Week. 

First  Week. 

Last  Week. 

Last  Week. 

Wet. 

Dry. 

Wet. 

Dry. 

Wet. 

Dry. 

Wet. 

Dry. 

Wet. 

Dry. 

Wet. 

Dry. 

38-5 

13-2 

37-0 

12-9 

*30-4 

11-3 

35-7 

12-2 

35*9 

12*2 

*19-9 

6-5 

43-7 

14-3 

42-0 

14-4 

*31-3 

12-3 

38-5 

13-7 

47-8 

14-5 

*30-0 

10-5 

34-8 

12-3 

32-5 

11-3 

34-5 

1109 

31-5 

10-2 

33-0 

10-7 

37-5 

12-5 

30-3 

1L6 

340 

11*7 

30-0 

11-4 

32-2 

11-8 

3M 

10-5 

30-0 

10-9 

40-2 

13-3 

41-0 

140 

42-4 

14-4 

37-8 

14-5 

45-7 

13-2 

42-5 

13-9 

42-3 

13-5 

44-5 

131 

441 

14-2 

40-5 

14-5 

42-5 

12-8 

450 

13-6 

45-1 

14-6 

43-0 

14-6 

44- 1 

15-7 

44-0 

15-0 

450 

14-8 

41-0 

14*6 

40-2 

13-4 

40-5 

14-5 

41-0 

13-8 

351 

131 

37-4 

13-2 

42-7 

15*6 

41-5 

14-3 

40-5 

140 

42-7 

15-0 

39-0 

14-6 

38-5 

14-6 

38-5 

13-2 

* These  Glutens  were  decomposed  and  very  difficult  to  wash. 


Water  Absorption  and  Moisture,  on  Arrival,  First,  and 

Last  Week. 


Viscometer  in  Quarts  per  Sack. 

Moistures. 

Hot  Store. 

Cold 

Store. 

Tinned 

Store. 

Hot  Store. 

Cold  Store. 

Tinned 

Store. 

Arriv- 

al. 

First 

Week. 

Last 

Week. 

First 

Week. 

Last 

Week. 

Last 

Week. 

Arrival. 

First 

Week. 

Last 

Week. 

First 

Week. 

Last 

Week. 

Last 

Week. 

No.  1 

57 

58 

69 

58 

55 

52 

15-33 

12-91 

8-95 

14-7 

15-4 

*14-5 

2 

59 

60 

70 

59 

57 

52 

14-73 

12-28 

7-85 

14-15 

13-95 

*14-5 

3 

63 

70 

74 

65 

63 

63 

12-81 

14-40 

8-07 

11-92 

13-2 

*16-4 

4 

72 

75 

81 

74 

72 

68 

12-65 

10-00 

* 

12-56 

* 

*12-8 

5 

68 

68 

75 

69 

65 

62 

13-06 

11-70 

8-5 

13-0 

13-08 

*13-0 

6 

70 

70 

76 

70 

65 

62 

12-67 

11-75 

8-60 

13-2 

13-51 

*12-9 

i ” 

1 

7 

69 

69 

76 

69 

68 

60 

12-61 

10-72 

8-20 

13-05 

13-82 

*12-8 

1 

8 

62 

65 

73 

64 

61 

59 

14-40 

10-65 

7-25 

13-70 

14-0 

*14-2 

)» 

9 

61 

68 

72 

62 

62 

62 

14-52 

11-02 

8-80 

14-03 

13-63 

*14-7 

* These  were  all  more  or  less  musty. 


COMMERCIAL  TESTING  OE  WHEATS  AND  ELOURS.  729 


Comparison  of  Colour  Readings,  Eirst,  and  Last  Week’s  Dry 

Elours. 


Hot  Storage. 

1 

Cold  Storage. 

1 

Tix.xed  Store.  ; 

! 

Arrival. 

First  Week. 

Last  Week. 

First  Week. 

Last  Week. 

Last  Week. 

1 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

1 

No.  1 

0-28 

0-21 

0-22 

1 

0-12 

0-20 

014 

0*18 

002 

0-20 

0*17 

0-30 

0-20 

„ 2 

0-30 

0-22 

0-20 

018 

0-21 

016 

0-20 

0-09 

0-21 

010 

0-30 

0-22 

„ 3 

0*30 

010 

0-20 

Oil 

0*19 

0-09 

Oil 

009 

0-10 

0-09 

0-28 

0-20 

„ 4 

0-29 

0-20 

0-25 

0-20 

0-22 

0-23 

010 

010 

0-24 

0-25 

0-30 

0-20 

„ 5 

0-30 

0-21 

0-29 

012 

0-20 

010 

0-27 

0-09 

0-27 

010 

0-34 

0-20 

„ 6 

0-30 

0-22 

0-30 

014 

0-22 

0-09 

0-30 

0-05 

0-26 

0-88 

0-36 

0-26 

„ 7 

0-38 

0-30 

0-31 

0-20 

0-27 

010 

0-31 

016 

0-28 

0-22 

0-39 

0-30 

„ 8 

0*34 

0-20 

0-30 

017 

0-22 

0-09 

0-20 

0-10 

0-20 

0-09 

0-31 

0*20 

„ 9 

0-32 

0-21 

0-34 

0-22 

0-21 

0-13 

0-24 

012 

0-20 

010 

0-30 

0-21 

1 

Colour  Comparison,  Pekarised  Elour. 


Hot  Storage. 

i 

Cold  Storage. 

Tixned  Store. 

Arrival. 

First  Week. 

Last  Week. 

First  Week. 

Last  Week,  i 

Last  ' 

\Yeek. 

Yellow. 

Red. 

Yellow. 

Red. 

Yellow.' 

Red. 

Yellow. 

Red. 

Yellow. 

Red. 

i 

Yellow. 

Red. 

No.  1 

0-81 

0-82 

0-73 

0-80 

0*80 

0-65 

0-91 

0-80 

0-80 

0-50 

0*80 

0-60 

. 2 

0-82 

0-84 

0*71 

0-80 

0-90 

0*60 

0-80 

0-62 

0-90 

0-80 

0-80 

0-83 

„ 3 

10 

0-81 

0-80 

0-63 

0-80 

0-56 

0-70 

0-53 

0-80 

0-60 

0*76 

0-61 

„ 4 

10 

10 

10 

0*80 

0*91 

0*70 

iO-92 

0-71 

0-89 

0-70 

0-84 

0-72 

,,  5 

0-88 

0-71 

1-3 

0-91 

0-90 

0-60 

0-90 

0-80 

0-90 

0-75 

0-90 

0-61 

„ 6 

0-94 

0*71 

1-2 

0-99 

0-90 

0-65 

0-90 

0-81 

0-90 

0-70 

10 

0-70 

„ 7 

109 

0-91 

1-3 

10 

10 

0-70 

0-90 

0-80 

10 

0-80 

M 

0*90 

„ 8 

0-80 

0-71 

1-5 

0-99 

0-75 

0-56 

0*71 

0-60 

0*80 

0-69 

0-80 

0-70 

„ 9 

0-90 

0-71 

1-4 

10 

0-80 

0-69 

0-90 

0-74 

0-86 

0-70 

0-87 

0*70 

Yield  of  Eermented  Dough,  Lbs.  per  Sack. 


Cold  Storage. 

Hot  Storage. 

Arrival. 

First  Week. 

Last  Week. 

First  Week. 

Last  Week. 

No.  1 

420  0 

425-0 

407-5 

422-5 

447-5 

„ 2 

4170 

424-0 

415-0 

422-5 

440-0 

„ 3 

435  0 

442-5 

425-0 

446-0 

472-5 

„ 4 

460-0 

460-0 

451-0 

471-5 

475-0 

„ 5 

442-5 

442-0 

427-5 

448-5 

465-0 

” ^ 

441-5 

445-0 

437-5 

445-0 

480-0 

„ 7 

446-5 

469-5 

445-0 

454-5 

472-5 

„ 8 

426-0 

430-0 

425-0 

434-0 

455-0 

„ 9 

424-0 

426-0 

427-5 

434-0 

452-5 

730  THE  TECHNOLOGY  OF  BREAD-MAKING. 


Yield  in  Qdakterns  per  Sack. 


Cold  Storage. 

1 

! Hot  Storage.  | 

1 

Arrival. 

First  Week. 

Last  Week. 

First  Week. 

Last  Week. 

No.  1 

96-6 

97-7 

93-7 

95-9 

102-9 

„ 2 

960 

97-5 

95-4 

97-1 

101-2 

1 1000 

101-7 

1 97-7 

102-5 

108-6 

„ 4 

105-8 

105-8 

i 103-7 

108-4 

109-2  1 

„ 5 

101-7 

101-7 

98-3 

103-1 

107-0  1 

„ 6 

101-5 

102-3 

lCO-6 

102-3 

110-4  1 

„ 7 

102-6 

104-0 

101-9 

1C4-5 

108-6  I 

„ 8 

97-8 

98-9 

97-7 

99-8 

104.6 

9 

97-5 

97-9 

98-3 

99-8 

1C4-7 

In  all  cases  the  hot  stored  flour  worked  best  and  produced  the  better  loaf,  and  the 
yield  was  much  greater. 


Record  of  Baking  Characters  of  Flours. 

No.  1.  Cold  stored  flour  : Showed  signs  of  newness  ; nice  feeling  dough, 
but  weak  ; producing  loaf  of  poor  volume  ; gradually  improved  till  April  2, 
when  it  stood  well,  producing  fair  volume  loaf  ; about  May  18  showed  signs 
of  deterioration,  not  standing  so  well  ; also  produced  loaf  of  inferior  flavour  ; 
in  June  did  not  work  so  well  ; poor  volume,  bad  colour. 

No.  1.  Hot  stored  : Showed  newness  of  flour,  runny  and  small.  March 
25,  greatly  improved  in  stability  and  water  absorption,  produc’ng  loaf  of 
good  volume  and  texture.  May  18,  still  improved,  worked  well,  producing 
fair  volume,  good  texture,  and  nice  colour  loaf.  June  9,  deteriorating  ; does 
not  work  so  well  ; poor  volume. 

No.  2.  Cold  storage  : Rather  weak,  but  good  colour.  March  17,  stands 
better,  worked  well,  rather  small,  fair  texture  in  crumb.  May  18,  much 
deteriorated  ; worked  fairly  ; produced  loaf  of  bad  flavour.  June,  not  so 
good  as  previous  baking  ; poor  volume,  close  dead  colour  in  crust,  musty 
flavour. 

No.  2.  Hot  storage  : March  11,  dead  feeling  dough,  a little  soft  ; loaf 
was  close  ; small  volume.  March  25,  greatly  improved,  worked  well,  pro- 
ducing loaf  of  good  volume  and  texture.  April  5,  still  improved  ; stands  well, 
better  volume.  May  20,  not  so  good,  going  back  in  quality.  June  9,  does 
not  work  or  stand  well  ; poor  volume  loaf,  bad  colour  and  texture. 

No.  3.  Cold  storage  ; Makes  a good  dough,  stands  well,  good-shaped 
loaf,  even  texture  ; keeps  good  character  throughout.  April  2,  worked 
well,  but  not  so  good  as  hot-stored  flour.  May  18,  losing  its  good  properties  ; 
poorer  in  volume,  rather  redder  in  crust.  June,  worked  only  fairly  ; slightly 
musty. 

No.  3.  Hot  storage  : Worked  well,  nice  and  springy  ; produces  nice  loaf 
in  texture,  and  colour  of  crumb  and  crust.  April,  works  well,  but  gluten 
seems  a little  short.  May  20,  worked  well  ; not  quite  so  springy,  fair  volume, 
good  texture  loaf.  June,  gluten  seems  brittle  in  moulding,  fair  volume,  good 
colour  loaf. 

No.  4.  Cold  storage  : Heavy  working,  no  spring.  April,  worked  better  ; 
no  improvement,  slightly  musty,  close.  May  18,  dark  and  musty. 

No.  4.  Flot  storage  : Bad  working,  no  life  ; close,  poor  volume  loaf.  March 
25,  worked  better  ; little  spring,  poor  volume.  April  5,  bad  colour,  no 
spring,  close  ; poor  volume  and  musty. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  731 


Nos.  5,  6,  7.  Cold  storage  : These  are  all  hard  flours  and  worked  very 
similarly,  behaving  well  throughout.  March  11,  worked  well  ; good  lively 
dough,  produced  good  volume,  a little  holey  ; good  colour  loaf.  April  2, 
worked  well  ; good  volume  and  texture  loaf.  May  18,  first-rate  working, 
stood  well  ; good  volume  and  colour.  June,  not  quite  so  good  as  previously. 

Nos.  5,  6,  7.  Hot  storage  ; These  worked  well  throughout,  and  improved 
by  storage  up  to  the  last,  producing  good-flavoured  and  bold  loaves. 

No.  8.  Cold  storage  : Nice  springy  dough,  showed  signs  of  newmess  by 
not  standing  well  ; fair  volume.  March  17,  still  shows  newness.  April  2, 
much  improved  ; nice  looking  loaf,  fair  texture.  May  18,  works  well  ; stands 
well,  good  volume,  texture,  and  nice  colour  loaf.  June,  not  so  good. 

No.  8.  Hot  storage  : March  11,  good  springy  dough,  worked  well  ; hot 
storage  much  improved  it.  March  25,  greatly  improved  ; good  volume  and 
texture  loaf.  April,  works  well  ; stands  well,  good  texture,  volume,  and 
flavour.  May  18,  quite  as  good  as  previous  baking.  June,  is  losing  its 
elasticity  ; not  so  good  volume. 

No.  9.  Cold  storage  : Good  dough,  but  little  soft  from  newness.  March 
17,  seems  more  runny.  April  2,  stands  better  ; fair  volume  loaf.  May  18, 
improved  ; good  volume,  fair  texture.  June,  worked  heavily,  much  inferior 
to  hot-stored  flour  ; rather  a close  loaf. 

No.  9.  Hot  storage  : Good  springy  dough,  nice  and  silky.  March  25, 
much  improved  ; stands  well.  April,  stands  well,  produced  good  texture 
and  volume  loaf.  May  20,  not  quite  so  good.  June,  worked  lifeless  ; gluten 
seems  to  be  decomposing ; poor  volume  loaf. 

For  the  whole  of  the  more  minute  details  the  reader  is  referred  to  the 
tables  themselves.  The  following  is  a summary  of  the  general  lessons  fur- 
nished by  these  experiments  ; — 

For  each  flour  there  are  three  distinct  series  of  observations,  viz., 
those  on  the  cold  stored,  hot  stored,  and  tinned  samples.  The  tem- 
perature of  the  cold  stored  flour  ranged  between  47°  F.  and  60°  F., 
with  a mean  closely  approaching  55°  F.  The  hot  stored  flours  ranged 
between  72°  F.  and  98°  F.  in  temperature,  with  a mean  temperature 
approaching  to  84°  F.  The  tinned  samples  were  kept  subject  to  the  same 
temperatures  as  those  which  were  cold  stored. 

Taking  the  various  determinations  in  the  order  given  we  find  that  the — 

Water -absorption  by  Viscometer  fell  off  slightly  in  the  case  of  the  cold 
stored  flours,  the  amount  of  such  falling  off  being  most  marked  with  the 
softer  flours.  With  those  that  were  hot  stored  there  was  in  each  case  a 
very  decided  increase.  In  the  tinned  samples  there  is  a decided  falling  off. 

Moistures. — In  the  cold  storage  there  is  no  regular  change  ; what  change 
there  is  is  not  great,  but  some  flours  have  slightly  gained  and  others  slightly 
lost  in  moisture.  These  changes  are  undoubtedly  governed  by  changes  in 
the  humidity  of  the  atmosphere.  The  hot  stored  flours  have  all  lost  very 
largely.  As  might  be  expected,  the  tinned  samples  show  very  little  variation. 

Glutens. — There  is  here  a very  marked  difference  betw^een  the  behaviour 
of  the  soft  and  the  harder  flours.  Taking  first  the  cold  stored  flours,  the 
softer  ones  show  a falling  off,  while  the  harder  ones  remain  stationary.  With 
the  hot  stored  flours,  notwithstanding  a loss  of  moisture,  the  soft  flours 
show  a falling  off,  wLile  the  harder  ones  exhibit  a decided  increase.  With 
those  stored  in  tins  the  soft  flours  have  changed  considerably  in  character, 
and  have  lost  a very  large  proportion  of  gluten. 

Bailing  behaviour. — With  regard  to  baking  behaviour,  a comparative  record 
is  given  of  the  quarts  of  water  taken  and  quarterns  yielded  per  sack.  It  will 
be  seen  that  with  the  cold  storage  there  is  in  most  cases  a diminution,  wiiereas 
with  hot  storage,  owing  to  the  diminishing  quantity  of  w'ater  present,  there  is 
in  all  cases  a greater  absorption  of  w^ater  in  doughing,  and  consequently  a 


732 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


greater  yield  of  bread.  The  extra  water  thus  taken  up  is,  in  most  cases, 
greater  than  the  actual  percentage  of  water  lost  as  a result  of  drying. 

In  another  table  is  given  a record  of  the  general  baking  behaviour  and 
character  of  the  flours  throughout  the  whole  period  of  storage.  Both  in 
cold  and  hot  storage,  there  is  a general  improvement  of  all  the  flours  for  the 
first  six  or  eight  wrecks,  after  which,  in  the  case  of  the  softer  flours,  there  is 
a falling  ofl  in  quality  in  the  case  of  those  stored  in  the  cold  ; but  vdth  regard 
to  those  kept  hotter  and  drier,  there  is  a steady  improvement  for  quite  three 
months,  at  the  end  of  which  the  softer  flours  commence  to  deteriorate, 
while  the  harder  flours  show  improvement  quite  to  the  end  of  four  months. 

Colour  Readings. — In  the  case  of  the  readings  on  the  dry  flours,  cold  stored, 
there  is  a decided  bleaching  action  for  about  the  first  fortnight,  after  which, 
for  the  next  four  weeks,  there  is,  as  a rule,  comparatively  little  change,  but  such 
as  there  is  is  in  the  way  of  darkening.  After  the  expiry  of  six  weeks  the 
darkening  is  more  marked,  but  the  last  readings  run  lighter  than  the  first. 
The  soft  flours  are  much  the  most  erratic  in  colour  changes. 

The  hot  stored  dry  flours  have,  as  a rule,  showed  a steady  bleaching. 

The  tinned  dry  flours  remained  almost  stationary,  but  in  some  cases 
showed  a slight  darkening. 

Taking  next  the  Pekar  test  results,  these  do  not  show  such  wide  variations 
as  those  on  the  dry  flours.  The  cold  stored  samples  remain  practically  the  same 
after  about  the  first  or  second  week,  during  which  there  is  some  bleaching. 
The  tinned  samples  show  but  little  change,  and  probably,  if  they  had  been 
read  every  week,  there  would  have  been  no  practicable  change,  say,  after  the 
first  ten  days. 

Best  Mode  of  Storing  Samples. — These  experiments  show  that  great 
changes  may  be  produced  in  flour  by  the  actual  conditions  under  which 
samples  are  stored  ; to  form  any  judgment  whatever  it  would  be  necessary 
that  storage  be  arranged  for  under  definite  and  regular  conditions.  Among 
conditions  which  seem  most  likely  to  serve  this  purpose  the  following  seem 
essential.  The  store  should  be  warm  and  dry,  say,  at  as  steady  a tempera- 
ture as  possible  of  80°  F.  A portion  of  the  flour  should  be  placed  in  a small 
bag,  and  then  this  stored  in  an  air-tight  tin  for  purposes  of  colour  testing.  A 
larger  portion  for  baking  and  other  tests  should  simply  be  kept  in  a close 
textured  bag. 

Sale  hy  Sample. — The  important  question  which  this  report  raises  is 
whether  or  not  stored  samples  can  in  fairness  to  buyer  and  seller  be  taken 
with  eonfidence  as  an  absolute  test  of  the  identity  or  otherwise  of  delivered 
bulk  of  flour.  Speaking  generally,  with  hard  flours,  properly  stored,  there 
is  very  little  change,  and  practically  such  flours  could  without  much  risk 
be  checked  against  sample,  particularly  if  a sample  of  the  bulk  flour  be  drawn 
and  stored  under  same  conditions  as  the  original  sample,  for,  say,  ten  days, 
and  then  the  comparison  made.  But  with  softer  flour  the  changes  wiiich 
go  on  cannot  be  measured  with  sufficient  accuracy  to  warrant  any  very  exact 
judgment  being  given. 

If  forward  sales  are  to  be  made  by  sample,  then,  in  the  opinion  of  the 
authors,  such  samples  should  be  stored  as  previously  suggested,  and  then 
within  from  ten  days  to  a fortnight  determinations  should  be  made  of  gluten 
and  colour.  If  necessary  to  check  bulk  against  original  sample,  a properly- 
drawn  bulk  sample  should  be  taken,  stored  for  ten  days  so  as  to  be  certain 
in  such  case  that  the  flour  lias  become  stable,  and  then  the  two  tested  against 
each  other.  In  most  instances  the  two  samples  could,  under  these  con- 
ditions, be  compared  against  each  other,  and  a reference  to  the  first  testing 
made  on  the  original  sample  would  at  once  show  whether  it  had  undergone 
serious  change.  If  there  were  no  such  change  then  the  comparative  test 
would  give  definite  information  and  data  as  to  quality  of  bulk  against  sample. 


COMMERCIAL  TESTING  OP  WHEATS  AND  FLOURS.  733 


If  the  sample  had  altered,  it  would  be  necessary  to  decide  each  case  on  its 
own  merits  as  to  whether  any  judgment  could  be  formed  from  the  sample. 
{N.  A.  Review,  p.  408,  1897.) 

802.  Effect  of  Keeping  Flour  on  Moisture  Content,  Snyder. — When 
samples  of  flour  are  preserved  three  to  six  months,  there  appears  to  be  a 
pronounced  change  in  the  moisture  content.  After  samples  of  flours  and 
milling  products  had  been  kept  in  sealed  bottles  in  a cool  place  for  six  months 
the  determined  moisture  content  of  all  of  them  averaged  about  2*5  per  cent, 
less  than  the  figures  for  water  in  the  fresh  samples.  If  so  great  a change  in 
moisture  had  actually  occurred,  the  calculated  and  the  determined  heats  of 
combustion,  as  obtained  by  the  calorimeter,  would  differ  from  the  heats  of 
combustion  determined  for  the  preserved  samples.  But  the  difference  be- 
tween the  determinations  made  on  samples  that  had  been  kept  three  months 
and  those  made  on  the  fresh  samples  was  no  greater  than  the  difference 
between  duplicate  determinations  made  on  the  same  sample.  It  would  seem, 
therefore,  that  the  apparent  loss  of  water  in  the  sample  preserved  is  simply 
due  to  the  hydration  of  the  gluten  proteins  ; that  is,  to  the  fact  that  the 
water  is  held  in  such  a way  that  it  is  not  driven  off  by  the  ordinary  method — 
^.e.,  drying  at  100°  C.  The . experiments  suggest  that  in  the  mixing  and 
other  stages  of  bread-making  the  hydration  of  the  gluten  proteins  is  one  of 
many  important  changes  which  take  place  in  flour,  and  that  water  plays  a 
chemical  as  well  as  a physical  part  in  bread-making. 

Snyder’s  observations  do  not  agree  with  those  recorded  in  the  preceding 
paragraph.  In  the  case  of  samples  preserved  in  tightly  fitting  tins,  the 
moisture  varied  but  slightly  from  the  commencement^  of  the  tests  therein 
recorded  to  the  conclusion.  [Bull.  101,  U.S.  Dept,  of  Agric.) 

803.  Baking  Tests. — In  comparing  the  relative  value  of  baking  tests 
with  those  made  by  analytic  methods,  it  should  be  borne  in  mind  that  the 
latter  are  obtained  by  processes  in  which  all  disturbing  influences  are  so  far 
as  possible  eliminated,  whereas  in  baking  tests  the  quality  of  the  yeast, 
temperature  of  working,  etc.,  are  all  disturbing  elements.  As  seen  by  pre- 
ceding results  quoted,  the  colour  and  other  characteristics  of  the  bread  are 
affected  by  differences  in  the  mode  of  performing  backing  tests.  In  baking 
tests,  again,  the  individuality  of  the  baker  must  largely  come  into  play, 
as  he  will  naturally  treat  the  flour  in  the  manner  most  nearly  comparable 
with  his  own  general  mode  of  working.  As  no  tw^o  bakers  work  exactly  alike, 
one  set  of  results  may  not  quite  agree  with  those  obtained  by  another  baker 
w'orking  in  a somew  hat  different  manner,  and  with  not  altogether  the  same 
objects  in  view'. 

There  follow'  a number  of  series  of  important  baking  and  other  tests 
made  at  different  times,  together  with  a description  of  the  mode  of  w'orking 
employed.  They  are  useful,  not  merely  for  the  data  they  afford,  but  also 
as  illustrations  of  different  experimental  methods. 

804.  M‘Dougairs  Tests. — In  Chapter  XIV.,  paragraph  424,  an  account 
of  various  milling  tests  by  M‘Dougall  Brothers  is  given  ; the  table  on  page 
734  embodies  the  results  of  baking  tests  made  by  them  on  the  flours  ob- 
tained. The  quantities  used  were  in  each  case  1 sack  (280  lbs.)  of  flour  ; 30 
lbs.  of  liquid  potato  ferment  ; 1 lb.  distillers’  yeast  ; and  3^  lbs.  of  salt.  The 
colour,  flavour,  and  texture,  are  expressed  by  a series  of  numbers,  the  highest 
quality  being  represented  by  the  highest  number.  This  system  of  giving 
“ marks  ” for  qualities  such  as  these  is  now  w'idely  adopted.  In  judging 
bread  for  various  competitions,  as  w'ell  as  for  flour  testing  purposes,  scales 
of  marks  are  used  for  the  valuation  of  those  qualities  which  cannot  otherw'ise 
be  expressed  numerically.  From  these  experiments,  M‘Dougall  Brothers 


734 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


conclude  that  yield  of  bread  does  not  mainly  depend  on  the  quantity  of 
gluten  contained  by  the  flour,  but  principally  on  its  degree  of  dryness. 
A feature  of  these  experiments,  which  has  caused  considerable  contro- 
versy, is  the  very  high  position  they  give  to  Indian  wheats,  particularly  as 
the  Report  was  prepared  at  the  request  of  the  Secretary  of  State  for  India. 


Baking  Tests  on  Single  Wheat  Flours^ — M‘Dougall  Bros. 


Yield 

of 

Bread 

when 

cold. 

Percentages. 

Colour,  Taste,  and  Texture. 

Wheat. 

Water 

used. 

Per- 

centage 

of 

Bread 

to 

Flour. 

Per- 

centage 

of 

Water 

to 

Flour. 

Colour, 

Exterior. 

Colour, 

Intel  ior. 

Texture. 

5 

S 

General  Char- 
acteiistics. 

Indian  (fine  soft  white) 

Lbs. 

141-4 

Lbs. 

364-0 

130-0 

50-5 

10 

11 

8 

7 

11 

Do. 

149-6 

367-5 

131-2 

53-4 

13 

13 

9 

9 

12 

Indian  (superfine  soft  white) 

141-6 

372-0 

133-0 

50-6 

8 

10 

9 

7 

10 

Do. 

148-0 

362-0 

129-3 

52-3 

12 

13 

10 

9 

11 

Indian  (average  hard  white) 

141-0 

370-5 

132-4 

50-8 

6 

7 

10 

7 

7 

Do. 

149-6 

365-0 

130-3 

53-4 

10 

9 

10 

9 

9 

Indian  (average  hard  red)  . . 

145-2 

376-6 

134-5 

51-8 

5 

7 

10 

7 

6 

Do. 

147-4 

365-0 

130-3 

52-2 

9 

9 

10 

8 

8 

English 

130-0 

352-0 

125-7 

46-4 

13 

12 

10 

13 

10 

Australian 

134-2 

355-4 

126-9 

48-0 

12 

12 

10 

12 

11 

New  Zealand . . 

132-0 

349-0 

124-6 

47-1 

12 

12 

9 

12 

10 

Californian 

136-8 

364-0 

130-0 

48-9 

12 

12 

9 

12 

10 

American  (Winter)  . . 

130-0 

346-0 

123-5 

46-4 

13 

12 

10 

12 

11 

American  (Spring)  . . 

130-0 

354-0 

126-4 

46-4 

8 

10 

12 

10 

9 

Russian  (Saxonska)  . . 

130-0 

356-0 

127-1 

46-4 

8 

9 

13 

9 

9 

Russian  (Taganrog)  . . 

145-4 

354-5 

126-6 

51-9 

10 

11 

12 

9 

9 

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805.  Clifford  Richardson’s  Baking  Tests. — In  1884  Clifford  Richardson 
presented  to  the  American  Government  a report  of  the  results  of  baking 
tests  made  of  American  flours.  The  objects  of  these  tests  was  largely  to 
investigate  M‘Dougairs  results  on  flours  from  American  wheats.  Richard- 
son prefaces  his  results  by  stating  that  “ using  flour  under  various  condi- 
tions, it  was  found  possible  to  vary  the  yield  of  bread  per  100  lbs.  of  flour 
as  much  as  15  lbs.  The  conditions  upon  which  this  variation  depends  are 
largely  physical,  and  include — 

Percentage  of  water  used  in  the  dough. 

Size  of  the  loaves. 

Temperature  of  the  oven. 

Time  of  Baking.” 

In  further  illustration  of  this  point,  Richardson  gives  a table  (page  735), 
showing  the  extent  to  which  the  variation  in  yield  is  dependent  on  the  per- 
centage of  water  (other  conditions  remaining  the  same),  the  size  of  the  loaves, 
difference  of  temperature,  and  on  the  time  of  baking. 

Richardson  further  points  out  that  “ a dough  made  with  any  American 
flours,  and  as  small  a percentage  of  water  as  was  used  by  the  M‘Dougalls, 
Avould  be  altogetlier  too  stiff  for  successful  results.”  Richardson  may  very 
possibly  have  overlooked  the  30  lbs.  of  potato  ferment  used  bv  the  M‘Dou- 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  735 


galls  ; adding  this  on  to  the  water  taken  for  American  flours,  the  total  is 
160  lbs.  or  16  gallons  of  liquid  per  sack.  This  quantity  is  quite  sufficient 
for  crusty  cottage  loaves  such  as  were  made  by  the  M‘Dougalls  ; whereas  in 
Richardson’s  experiments  a slack  tin  or  pan  dough  is  throughout  used.  The 
difference  is  largely  due  to  difference  in  the  character  of  the  bread  commonly 
made  in  America  and  England  respectively.  This  point  should  always  be 
borne  in  mind  when  comparing  results  obtained  by  observers  in  the  two 
countries.  A further  important  bearing  it  has  is  this — the  flour,  which  will 
take  a relatively  high  proportion  of  water  for  slack  or  tin  dough,  is  not  neces- 
sarily that  which  will  also  take  a relatively  high  proportion  when  used  for 
crusty  cottage  bread.  Flours  A\dth  soft  ductile  glutens  will  often  take  a 
very  large  quantity  of  water,  provided  the  dough  is  supported  in  a pan  for 
baffing,  while  they  may  in  the  stiffer  dough  be  comparatively  unable  to 
stand  vithout  support,  and  so  make  a flat,  runny  loaf. 


Variations  in  Bread  Yield — Richardson. 


Dependent  on 
Percentage  of  Water 
used  (other  conditions 
being  the  same). 

Dependent  on  Size 
of  Loaves. 

Dependent 
on  Difference  of 
Temperature. 

Dependent  on  Time 
of  Baking. 

Per  cent. 

Yield  of 

No.  of 

Yield  of 

Tem- 

Yield of 

Time, 

Yield  of 

of  Water. 

Bread. 

Loaves. 

Bread. 

perature. 

Bread. 

Minutes. 

Bread. 

54-5 

134-0 

1 loaf 

138-6 

249° 

136-9 

50 

134-6 

58-4 

136-9 

10  rolls 

129-6 

230° 

140-8 

30 

140-2 

62-1 

144-9 

— 

— 

— 

— 

— 

— 

62-1 

145-5 

— 

— 

— 

— 

— 

— 

In  all  American  systems  of  flour-testing  which  have  come  under  the 
authors’  personal  notice,  the  baking  tests  are  made  on  tinned  bread.  This, 
doubtless,  gives  the  best  results  for  flour  as  used  in  America.  It  is  suggested 
that  American  millers,  who  export  to  this  country,  should  also  have  their 
flours  tested  by  methods  based  on  the  production  of  crusty  bread  such  as 
is  most  generally  made  in  England. 

Richardson  made  a dough  with  the  whole  of  the  water,  allowed  it  to 
rise  till  the  outer  pellicle  was  just  cracking,  then  re-kneaded  it  into  loaves, 
which  were  put  in  tins  or  pans  and  then  baked.  The  table  on  pages  736 
and  737  gives  the  results  of  his  experiments. 

806.  Flours  collected  in  America. — In  1893  one  of  the  authors  made  an 
extended  tour  through  the  United  States  and  Canada,  collecting  personally 
a number  of  typical  flours,  and  subjecting  them  to  commercial  analysis  and 
baking  tests,  particulars  of  which  are  given  on  page  739.  The  various  analytic 
tests  need  no  further  explanation,  but  it  may  be  mentioned  that  in  the  baking 
tests  the  method  employed  was  the  making  of  an  off-hand  dough  of  tight- 
ness sufficient  for  crusty  cottage  loaves.  The  quantities  taken  were  one 
kilogram  of  water  and  sufficient  flour  to  make  a dough  of  requisite  con- 
sistency. The  water  has  been  calculated  to  quarts  per  sack  ; other  data 
are  also  given.  Subjoined  is  a list  of  the  flours,  together  with  particulars 
of  the  variety  of  wheat  from  which  each  was  produced. 


Baking  Tests  on  Various  American  Flours. — Clifford  Richardson. 

Ill  the  following  series  of  baking  tests,  in  each  experiment  there  were  taken  of  water  G50  grams,  milk  500  grams,  salt  25  grams,  yeast  10 
:''ams,  with  the  weight  of  flonr  as  under : — 


736 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Baking  Tests  on  Various  American  Flours. — Clifford  Richardson — continued. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  737 


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738 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  1.  Spring  wheat,  bakers’  grade,  made  from  selected  grades  of  hard 
or  Fife  spring  wheat  grown  in  North  Dakota  and  Northern  Minnesota. 

No.  2.  Patent  flour  from  same  wheat. 

No.  3.  Spring  wheat,  bakers’  grade,  made  from  selected  hard  wheats 
from  Northern  Minnesota. 

No.  4.  Patent  flour  from  same  wheat. 

No.  5.  Spring  wheat,  bakers’  grade,  made  from  hard  wheats  exclusively, 
grown  in  North  Dakota  and  Northern  Minnesota. 

No.  -6.  Patent  flour  from  same  wheat. 

No.  7.  Spring  wheat,  bakers’  grade,  made  from  hard  Fife  wheat  grown 
in  Manitoba,  etc.,  in  North-West  Canada. 

No.  8.  Patent  flour  from  same  wheat. 

No.  9.  Winter  wheat,  bakers’  grade,  made  from  wheat  grown  in  Central 
and  Southern  Indiana  and  Southern  Illinois,  principally  of  the  long  berry 
red  variety. 

No.  10.  Patent  flour  from  same  wheat. 

No.  11.  Winter  wheat,  bakers’  grade,  made  from  a blend  of  about  65 
per  cent,  long  berried  hard  red  Mediterranean,  and  35  per  cent,  small 
plump  oval  berried  Fultz  wheats,  indigenous  to  the  valleys  of  Southern 
Indiana  and  Illinois. 

No.  12.  Second  patent  flour  from  same  wheat. 

No.  13.  First  patent  flour  from  same  wheat. 

No.  14.  Winter  wheat,  bakers’  grade,  made  from  best  winter  wheat 
grown  entirely  in  Southern  Illinois. 

No.  15.  Patent  flour  from  same  wheat. 

No.  16.  Winter  wheat,  bakers’  grade,  made  from  Indiana  red  winter 
wheat. 

No.  17.  Patent  flour  from  same  wheat. 

No.  18.  Winter  wheat,  bakers’  grade,  made  from  wheat  grown  in  Indiana 
and  Eastern  Illinois. 

No.  19.  Patent  flour  from  same  wheat. 

No.  20.  Winter  wheat,  bakers’  grade,  made  from  red,  soft,  milling  wheat, 
Fultz  and  Mediterranean  varieties  growui  in  Ohio. 

No.  21.  Patent  flour  from  same  wheat. 

807.  Report  on  American  Flours,  Jago  and  Briant. — Briant  and  one  of 

the  authors  were  in  1893  requested  to  report  to  the  National  Association 
of  Master  Bakers  and  Confectioners  of  the  United  Kingdom  on  the  ques- 
tion of  the  grading  of  American  flour.  They  prepared  a Report  which  was 
presented  to  the  Association  in  1894,  in  which  it  was  recommended  that 
flour  standards  be  formulated  of  which  bakers  might  avail  themselves  in 
purchasing  flour,  and  use  them  for  comparing  their  bulk  delivery  with  the 
quality  of  flour  actually  bought.  The  following  were  among  its  principal 
recommendations  : — 

Division  into  Classes. — For  purposes  of  grading,  it  is  advised  that  American  flours 
be  divided  into  the  following  three  classes  : — I.  Spring  wheat  flours,  milled  from  hard 
wheats  grown  principally  in  the  Dakotas,  Minnesota,  and  Manitoba,  Canada.  II. 
Winter  wheat  flours,  milled  from  wheats  of  medium  hardness,  grown  principally  in 
Missouri,  Illinois,  Indiana,  and  Ohio.  III.  Kansas  wheat  floms,  milled  from  hard 
winter  wheats,  grown  principally  in  Kansas. 

Typical  Grades  or  Standards. — In  each  class  there  should  be  three  typical  grades 
or  standards  : — No.  1 Standard  should  consist  entirely  of  the  best  patent  flour  of  the 
grain,  and  should  not  exceed  in  quantity  more  than  about  40  per  cent,  of  the  entire 
flour  product  of  the  wheat.  The  dressing  of  this  flour  should,  of  course,  be  perfect. 
This  standard  should  be  reached  by  all  “first  patents.”  No.  2 Standard  should  be 
a veritable  straight  grade  flour,  containing  the  w'hole  flour  product  of  the  wheat,  except 
the  Red  Dog  low  grade,  whose  proper  place  is  the  offal  department.  These  flours 
should  be  well  dressed  and  free  from  specks.  This  standard  should  be  at  least  reached 


Results  of  Analytic  and  other  Tests  on  American  Flour  Samples. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  739 


Remarks  on  Doughs. 

|Firm  and  elastic,  dry  and  Miry. 

Fair  stiffness. 

Biscuit  rather  than  bread  flour. 

A little  tight,  nice  firm  dough. 

Fair  stiffness. 

Fair  stiffness. 

A little  slack. 

Fairly  strong  and  wiry. 

Nice  firm  dough. 

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740 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


by  all  so  called  “ second  patents.”  No.  3 Standard  should  consist  of  the  whole  of  the 
remaining  flour,  not  Red  Dog  or  offal,  after  the  removal  of  the  40  per  cent,  of  patent 
flour  constituting  the  No.  1 Standard.  These  flours  should  be  clear  and  well  dressed. 
This  standard  should  be  reached  by  so  called  “ First  bakers’  grades.” 

Suggestions  follow  (in  the  Report)  as  to  the  obtaining  of  samples  of  flour 
from  which  to  formulate  standards,  and  also  as  to  the  methods  of  examina- 
tion to  be  adopted  : these  agree  very  closely  with  those  already  described. 
Various  flours  were  collected  on  the  London  market,  and  supplied  to  the 
authors  of  this  report  for  examination.  The  following  is  a list  of  the  flours, 
together  with  Mark  Lane  prices  at  time  of  collection  ; — 


No.  Description.  Price. 

s.  d. 

1.  Minneapolis  First  Patent  . . . . . . . . 24  0 

2.  Minneapolis  First  Patent  . . . . . . . . 24  0 

_ 3.  Duluth  First  Patent  . . . . . . . . . . 24  0 

4.  Kansas  First  Patent  . . . . . . . . . . 21  0 

5.  Minneapolis  First  Patent  . . . . . . . . 24  0 

6.  Minneapolis  Second  Patent  . . . . . . . . 22  0 

7.  Duluth  Second  Patent  . . . . . . . . 21  6 

8.  Minneapolis  First  Bakers  . . . . . . . . 16  6 

9.  Minneapolis  First  Bakers  . . . . . . . . 16  6 

10.  Duluth  First  Bakers  . . . . . . . . . . 16  6 

11.  Kansas  First  Bakers  . . . . . . . . . . 17  0 

12.  Minneapolis  Low  Grade  . . . . . . . . 15  0 


Nos.  1,  8,  and  12 — Nos.  2,  6,  and  9 — Nos.  3,  7,  and  10 — and  Nos.  4 and 
11  — are  in  each  case  series  from  the  same  mill.  The  results  of  various  tests 
are  given  on  pages  741-743. 

As  an  example  of  the  formulation  of  standards  from  these  flours,  equal 
parts  of  Nos.  1,  2,  and  5 were  mixed  and  used  as  standard  No.  I.,  while 
equal  parts  of  Nos.  8 and  9 were  taken  as  No.  III.  standard.  These  gave  the 
following  analytical  results  ; — 

No.  I.  Standard. 

Wet  gluten  . . . . . . 40*8  per  cent. 

Dry  „ 12-5  „ 

True  ,,  . . . . . . 10*96  ,, 

Water  absorption  by  Viscometer  65’3  quarts. 

Colour,  Pekarised  I ;;  ” 

With  accurately  adjusted  standards  it  is  possible  to  assign  to  an  inter- 
mediate flour,  by  calculations  made  on  the  results  obtained  by  testing, 
a position  which  shows  its  relative  value  compared  with  the  standards  above 
and  below.  But  while  the  method  serves  to  indicate  • closely  the  value 
of  flours  of  the  same  type,  yet  obviously  no  proper  comparison  can  be  made 
between  flours  of  different  character. 

808.  American  Flour-Testing  Methods. — It  is  the  practice  of  leading 
American  millers  to  have  baking  tests  made  daily  on  their  flours  by  pro- 
fessional specialists,  who  report  not  only  on  the  flour  of  the  particular  mill, 
but  also  include  the  results  of  tests  on  other  flours  made  the  same  day.  Each 
individual  mill  knows  the  identity  of  its  own  flours,  but  is  not  acquainted 
with  that  of  any  others  of  the  series.  On  page  744  is  a copy  of  the 
daily  schedule  of  the  Howard  Wheat  and  Flour  Testing  Laboratory  of  Minne- 
apolis, Minn.,  U.S.A.,  which  was  the  originator  and  pioneer  of  this  organised 
system  of  testing  in  America. 


No.  III.  Standard. 

47*0  per  cent. 
16*2 

12*88  „ 
65*5  quarts. 
1-75  „ 

1*44  „ 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS. 


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(а)  These  glutens  were  extracted  by  a student  comparatively  inexperienced  in  gluten  testing,  and  differ  considerably  in  percentage  from  their  dupli- 

cates when  wet.  The  principal  reason  for  their  insertion  is  that  they  show  that  the  “true  gluten”  (calculated  from  the  percentage  of 
nitrogen  in  the  dry  gluten)  in  the  duplicates  differs  but  slightly  in  percentage  from  that  in  the  original  series. 

(б)  The  crude  gluten  extracted  from  this  flour  was  obviously  composed  largely  of  cellulose  ; in  appearance  it  was  very  fibrous,  and  undoubtedly 

contained  a very  low  percentage  of  albuminous  matter. 


Jago  and  Briant’s  Report  on  Flours— 


742 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Baking  Tests  on  Jago  and  Briant  Flours. 


COMMERCIAL  TESTIXG  OE  WHEATS  AND  FLOURS.  743 


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The  Howard  Wheat  and  Flour  Testing  Laboratory.  Established  1836. 
GENERAL  COMPARATIVE  BAKING  RESULTS. 


744 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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COMMERCIAL  TESTING  OP  WHEATS  AND  FLOURS.  745 


“ Explanation  of  Report. 

CoLOUH  Marking. — Patents  : Maximum,  1 ; Medium,  1 -5  ; Minimum,  2.  Straights  : 
Maximum,  2-5  ; Medium,  3 ; Minimum,  3-5.  Clears  : Maximum,  4 ; Medium,  5 ; 

Minimum,  6.  2nd.  Clears  : Good,  7 ; Poor,  8.  Low  Grades  and  Red  Dogs  : 9 and  10. 

The  general  characteristics  of  the  flour  such  as  Colour  quality.  Elasticity,  etc.,  are 
described  under  the  headings  “ Doughing  Test  ” and  “ Remarks  on  Loaf.” 

For  convenience  colour  is  marked  numerically  as  shown,  but  full  straights  will 
usually  run  one  or  two  figures  better  than  indicated  by  the  nomenclature  used. 

Volume  (expressed  in  cubic  inches)  indicates  elasticity  or  rising  power,  showing 
whether  the  sample  is  in  proper  baking  condition  or  has  the  ability  to  produce  a good 
sized  loaf. 

Twelve  ounces  flour  used  in  each  loaf.  Weight  of  loaf  when  taken  from  oven 
(bread  yield)  expressed  in  ounces  decimally.  Amount  of  water  used  (absorption) 
indicated  decimally. 

Each  loaf  is  made  according  to  our  standard  formula  with  identical  amounts  of 
all  ingredients  except  water,  and  kneaded  exactly  alike  by  automatic  machinery,  sponge 
boxes  and  ovens  being  controlled  at  uniform  temperature  and  the  following  items 
being  recorded  : Ounces  of  flour.  Ounces  of  water,  Grains  of  yeast.  Grains  of  salt, 
Grains  of  sugar.  Grains  of  lard.  Temperature  of  flour.  Temperature  of  water  sponge, 
Temperature  of  sponge  box.  Time  for  sponge  to  rise.  Amount  of  kneading.  Time  for 
first  rising  of  dough.  Time  for  second  rising  of  dough.  Time  for  third  rising  in  oven, 
Temperature  of  oven  when  put  in.  Temperature  of  oven  when  finished.  Time  for  baking. 

Under  “ Additional  Data,”  such  data  or  special  tests  as  Ash,  Acidity,  Crude  Wet 
and  Dry  Gluten,  True  Gluten,  Gliadin,  Glutenin,  Moisture,  Starch,  Soluble  Carbo- 
hydrates, Fibre,  Oil,  Soundness,  Odour,  Miscroscopic  Tests,  Granulation,  Minutes  of 
Fermentation,  etc.,  are  entered.” 


809.  Baking  Tests,  Thatcher. — Thatcher  has  recently  summarised  the 
various  methods  proposed  for  the  testing  of  flour,  and  describes  those  recom- 
mended and  adopted  by  him  in  the  laboratory  of  The  Washington  Agricul- 
tural Experiment  Station,  U.S.A.  The  following  is  a description  of  his 
mode  of  making  baking  tests  ; — 


Flour 

Yeast 

Sugar 

Salt 

Water 


Quantities  taken. 


340  grams. 
10  „ 

12  „ 


A sufficiency. 


These  were  then  kneaded  in  a special  machine  for  twenty  minutes,  so 
arranged  as  to  maintain  the  dough  at  a temperature  of  90°  F.  for  that  time. 
The  dough  was  then  transferred  to  a greased  tin,  and  placed  in  a proving 
box  or  cupboard  maintained  at  90°.  Here  it  was  allowed  to  rise  until  it 
just  touched  a tin  strip  laid  across  the  top  of  the  tin.  The  tin  was  then 
transferred  to  an  electric  oven  heated  to  400°  F.,  and  baked  for  forty  min- 
utes. The  bread  was  allowed  to  cool  for  thirty  minutes,  after  which  the 
weight  and  volume  were  determined.  The  latter  was  effected  by  measuring 
in  a cylindrical  box  with  seeds.  Thatcher  concludes  that  it  is  impossible 
to  form  final  conclusions  as  to  the  baking  quality  of  a flour  from  the  results 
of  a chemical  analysis  alone!  Further,  he  is  of  opinion  that  no  single  test 
which  was  tried  is  capable  of  giving  conclusive  evidence  as  to  the  baking 
quality  of  flour.  Any  such  processes  as  have  yet  been  suggested  must  be 
supplemented  by  a baking  test  if  final  and  accurate  conclusions  are  to  be 
reached.  [Jour.  Amer.  Chem.  Soc.,  1997,  910.) 

810.  Baking  Tests,  Method  employed  by  the  Authors. — The  quantity  of 
flour  taken  for  a baking  test  may  vary  according  to  the  custom  and  require- 
ments in  any  particular  district.  Usually,  however,  it  is  desirable  to  keep 
the  quantity  as  low  as  practicable,  so  that  a test  may  be  made  on  a small 
sample  : at  the  same  time  the  loaf  should  be  of  a fair  size,  so  as  to  compare 


746  THE  TECHNOLOGY  OF  BREAD-MAKING. 

as  well  as  possible  with  the  bread  made  for  commercial  purposes.  The 
authors  employ  the  following  quantities,  which  answer  well  for  general 
purposes. 

Quantities. — Flour  . . . . . . 560  grams  = 19*71  oz. 

Water  as  per  Viscometric  Absorption,  or  otherwise  deter- 
mined. 

Salt  . . . . . . 6 grams. 

Compressed  Yeast  . . 10  grams. 

The  metric  system  of  weights  is  adopted  because  of  its  greater  simplicity 
and  the  readiness  with  which  exact  weights  can  be  determined.  The  quan- 
tity, 560  grams,  is  2 grams  for  every  lb.  of  flour  in  the  sack,  so  that  one  half 
the  weight  of  any  constituent  or  product  is  without  any  further  calculations 
the  weight  in  lbs.  that  would  be  obtained  proportionately  by  treatment 
of  the  sack  of  flour. 

The  resultant  loaf  of  bread  usually  weighs  from  1 J lbs.  to  If  lbs.,  and 
although  less  than  the  weight  of  a 2-lb.  loaf,  is  yet  sufficiently  near  to  enable 
a comparison  to  be  instituted. 

Bearing  in  mind  that  the  proportions  of  water  used  vary  very  considerably 
in  different  parts  of  the  United  Edngdom,  the  authors,  for  general  tests,  have 
adopted  the  plan  of  making  where  possible  three  separate  bakings  on  each 
flour,  distinguished  respectively  as  a,  b,  c.  For  b,  what  is  believed  to  be 
the  best  quantity  of  water  is  employed.  This  may  be  determined  by  a 
water-absorption  test,  controlled  by  the  viscometer  or  otherwise.  It  will 
be  remembered  that  that  instrument  gives  results  in  quarts  per  sack  ; and 
as  a quart  weighs  2J  lbs.,  the  number  of  quarts  X 5 gives  the  weight  in 
grams  or  volume  in  cubic  centimetres  of  water  that  must  be  taken  to  the  560 
grams  of  flour.  Fora,  20  grams  (equivalent  to  4 quarts)  less  water  is  taken 
than  in  b : while  in  c,  20  grams  more  water  is  added  than  used  in  b.  The  three 
tests,  therefore,  represent  quantities  of  water  with  differences  of  a gallon  to  the 
sack  between  each,  and  cover  all  variations  in  quantities  for  ordinary  bread- 
making. Another  advantage  of  testing  in  this  manner  is  that  it  provides  for 
those  flours  which  fall  off  very  much  during  fermentation.  In  other  words, 
some  flours  will  not  in  reality  take  as  much  water  as  might  be  judged  from 
the  tightness  of  the  dough  when  first  made.  Conversely,  other  flours  fall  off 
less  than  the  normal  in  fermentation,  and  evidently  require  more  water  than  is 
indicated  by  the  character  of  the  dough  at  the  moment  of  preparation.  Where 
one  test  only  is  made,  a very  frequent  comment  is — this  flour  would  have 
been  better  with  a quart  or  two  quarts  more  [or  less]  water.'  If  a series  of 
tests  is  made,  one  of  them  is  likely  to  closely  agree  with  the  quantity  of 
water  best  suited  to  the  flour  throughout  its  whole  fermentation.  If  thought 
preferable  the  difference  between  each  test  may  be  taken  at  some  other 
figure  than  the  gallon. 

Mode  of  Fermentation. — First  weigh  out  the  flour,  and  put  it  in  a pan 
of  sufficient  size  (for  whieh  purpose  an  ordinary  white  pudding-basin,  8 
or  9 inches  internal  diameter,  answers  well).  Next  take  the  temperature 
of  the  flour,  and  if  anything  below  70°  F.,  carefully  warm  it  until  that  tem- 
perature is  reached.  A convenient  method  in  the  testing  laboratory  of 
doing  this  is  to  stand  the  basin  eontaining  the  flour  in  hot  water,  and  stir 
the  flour  continually  with  a spatula  until  sufficiently  warm.  A “ ferment 
is  next  made  with  the  whole  of  the  water  to  be  used.  This  water  may  be 
either  measured  or  weighed  ; if  the  former  course  be  adopted,  the  measures 
should  be  specially  graduated  to  deliver  grams  of  water  at  100°  F.  It  has 
been  found  convenient  to  have  the  ferment,  when  set,  at  90°  F.  ; the  initial 
temperature  of  the  water  should  be  so  adjusted  by  experiment  as  to  give 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  747 


this  temperature  at  the  finish  ; usually  about  10°  is  lost  in  this  operation, 
and  therefore  the  water  may  be  taken  at  100°  F.  Make  a hole  in  the  middle 
of  the  flour  (bay),  and  having  the  water  in  a measure,  break  down  the  pre- 
viously weighed  yeast  into  the  water,  and  pour  the  whole  into  the  bay. 
Work  carefully  a little  of  the  flour  into  the  liquor  so  as  to  form  a ferment 
of  the  consistency  of  a thin  batter  : this  ferment,  as  above  stated,  should 
have  a temperature  of  90°  F.  For  the  fermentation  there  should,  when 
practicable,  be  provided  a proving  cupboard,  so  arranged  as  to  just  take, 
on  a series  of  shelves,  a number  of  these  basins,  all  of  which  must  be  labelled 
and  marked.  By  some  convenient  means  the  temperature  of  this  cupboard 
should  be  maintained  at  about  85°  F.  ; this  may  be  done  either  by  the 
injection  of  a jet  of  steam,  or  the  well-known  plan  of  a small  atmospheric 
burner  at  the  bottom  of  the  cupboard,  with  a vessel  of  water  over  it.  The 
temperature  of  this  cupboard  should  be  under  control,  and  must  be  kept 
uniformly  at  the  desired  degree. 

Cover  the  basin  containing  the  ferment  with  a light  linen  cloth,  and 
place  it  in  the  proving  cupboard  for  one  hour  ; at  the  end  of  that  time  the 
ferment  will  be  “ ready,”  and  should  have  nicely  dropped.  Add  the  finely- 
powdered  salt,  and  stir  in  the  flour  and  salt  into  the  ferment  with  a bone 
spatula.  Knead  thoroughly  either  by  hand,  or  preferably  in  one  of  Werner 
and  Pfleiderer’s  small  doughing  machines,  taking  care  that  no  loss  occurs 
during  the  operation,  and  that  the  dough  is  made  perfectly  smooth.  Return 
to  the  proving  cupboard,  and  after  one  hour  well  “ knock  down  ” the  dough  ; 
place  again  in  the  cupboard  for  half  an  hour,  and  then  weigh  the  dough 
accurately.  The  bread  may  be  baked  in  a tin,  or  for  most  purposes,  pre- 
ferably, as  a cottage  loaf.  Mould,  and  allow  to  sta-nd  for  a few  minutes 
if  necessary.  Moulding  should,  if  possible,  be  done  vithout  dusting  flour  ; 
when  any  is  used,  a quantity  should  be  weighed,  a.nd  that  remaining  after 
the  moulding  of  each  loaf  again  weighed,  and  note  made  of  the  quantity 
used.  This  should  not  exceed  2 grams  per  loaf.  Bake  in  an  oven,  the 
temperature  and  behaviour  of  which  is  knovTi,  and,  if  possible,  together 
with  loaves  of  a familiar  flour,  so  as  to  be  able  to  judge  the  comparative 
tendency  of  the  flour  to  take  the  fire.  When  baked,  allow  the  bread  to 
stand  twelve  hours — say  over  night — and  then  weigh.  Notice  whether 
the  bread  happens  to  be  burned  at  the  bottom,  and  if  so  make  a note,  as  the 
weight  will  thereby  be  affected. 

Note  the  character  of  the  loaf,  compared  vflth  a standard  or  known 
sample  ; whether  of  good  volume,  bold  and  well  shaped,  twisted  or  flat  ; 
also  the  colour  of  the  outer  crust,  and  likewise  in  the  partings  between  the 
top  and  bottom  of  the  cottage. 

If  wished,  the  volume  of  the  loaf  may  be  determined  by  means  of  a, 
cylindrical  measure  sufficiently  large  to  hold  it  completely.  The  loaf  is 
placed  in  this,  and  rape  seed  or  other  small  seed  added  to  fill  the  measure, 
the  upper  surface  of  which  is  then  “ struck.”  The  quantity  of  seed  used 
is  then  measured,  preferably  in  a vessel  graduated  in  cubic  centimeters,, 
and  also  the  quantity  of  seed  similarly  required  to  fill  the  measure  without 
the  loaf.  The  difference  gives  the  volume  of  the  loaf. 

Compare  the  appearance  of  the  three  loaves  side  by  side,  and  decide 
which  represents  the  bread  from  the  best  size  or  stiffness  of  dough.  Note 
also  whether  there  is  a great  difference  betw'een  each,  as  some  flours  stand 
an  excess  of  w'ater  over  the  normal  far  better  than  others. 

Next  cut  the  loaf  in  the  direction  of  greatest  outline,  and  observe  the 
colour,  texture,  pile,  and  sheen  of  crumb  ; also  moistness  odour,  and  flavour 
of  crumb.  (It  should  be  borne  in  mind  that  the  flavour  of  a small  baking 
test  is  not  an  absolute  criterion  of  that  of  bread  regularly  made  in  full-sized 
batches.)  The  colour  may  be  measured  and  registered  when  thought 


748  THE  TECHNOLOGY  OF  BREAD-MAKING. 

desirable  by  means  of  the  tintometer  modified  by  the  addition  of  de-focussing 
lenses. 

If  wished,  a system  of  giving  marks  for  colour,  texture,  fiavour  and 
other  characteristics  may  be  adopted.  In  fixing  these  a maximum  and 
minimum  should  be  decided  on,  and  then  the  loaf  being  tested  should  have 
its  intermediate  position  indicated  as  accurately  as  possible  by  the  number  of 
marks  given. 

If  it  is  desired  to  keep  a permanent  record  of  its  size,  the  cut  loaf  may 
be  placed  on  a sheet  of  paper,  and  marked  round  with  a pencil.  This  may 
be  done  on  a leaf  of  a note-book,  and  the  other  data  placed  on  the  opposite 
page.  (See  Fig.  109.) 

The  following  are  given  as  an  example  of  how  baking  tests  may  be  entered 
in  the  note-book,  together  with  deductions  made  therefrom  ; — 

Description  of  Flour— High-Class  English  Patent. 

Water  absorption  by  Viscometer — 60  quarts  per  sack. 


a.  b.  c. 


Flour  in  grams 

560 

560 

560 

Water  ,, 

280 

300 

320 

Yeast  ,, 

10 

10 

10 

Salt  ,, 

6 

6 

6 

— 





Unfermented  Dough  in  grams 

856 

876 

896 

,,  ,,  lbs.  per  sack 

428 

438 

448 

Fermented  Dough  in  grams . . 

827 

850 

860 

,,  ,,  lbs.  per  sack.  . 

Fermented  Dough  calculated  into  loaves 

413*5 

425 

430 

of  4 lbs.  6 oz.  per  sack  . . 

94*5 

97*1 

98*3 

Weight  of  Bread,  12  hours  old,  in  grams  . . 
Weight  of  Bread,  12  hours  old,  in  lbs.  per 

707 

737 

760 

sack 

353*5 

368*5 

380 

Loaves  of  4 lbs.  each  per  sack 

88*4 

92*1 

95*0 

Colour  of  bread  by  Tintometer — -Yellow  . . 

1*35 

1*35 

1*35 

„ „ ,,  Red  .. 

0*70 

0*75 

0*75 

In  the  above  results  the  mode  of  determining  lbs.  per  sack  is  self-evident  : 
quantities  in  grams  are  simply  divided  by  2.  Calculated  loaves  per  sack 
from  dough  are  obtained  from  lbs.  per  sack  by  reducing  to  ounces  and 
dividing  by  70  (ounces  = 4 lbs.  6 oz.).  The  readiest  way  of  performing  this 
calculation  is  to  multiply  weight  in  grams  by  8 and  divide  by  70,  thus  : 

^ ^ = 94-5  loaves  per  sack. 

70  ^ 

The  results  obtained  as  yield  in  bread  by  calculating  at  4 lbs.  6 oz.  on 
the  dough  are  more  trustworthy  than  those  by  direct  weighing  of  the  bread 
itself,  as  single  sample  loaves  will  vary  more  in  weight  from  the  normal  than 
does  a full  batch  calculated  on  the  weight  of  dough. 

811.  Special  Apparatus  for  Baking  Tests. — When  baking  tests  are  being 
conducted  on  a large  scale,  certain  special  appliances  enable  results  to  be 
obtained  not  only  with  greater  speed,  but  with  more  exactitude. 

For  water  measuring  purposes  it  is  very  convenient  to  employ  a large 
burette  and  reservoir  similar  in  character  to  that  figured  No.  103  for  making 
viscometric  determinations.  The  burette  should  have  a capacity  of  400 
C.C.,  and  sliould  be  provided  with  a large  way  tap.  The  reservoir  should 
be  open  at  the  top,  but  provided  with  a cover  : a number  of  tests  having 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  749 


to  be  made,  sufficient  water  should  be  in  one  operation  adjusted  to  the  right 
temperature,  and  used  for  the  whole  series  that  are  started  off  together. 

Wliere  it  is  possible  to  bake  sample  loaves  with  a batch  of  ordinary 
bread,  that  forms  one  of  the  best  modes  of  procedure.  It  has  the  great 
advantage  for  crusty  bread  that  a better  shaped  loaf  is  produced  than 
when  single  loaves,  or  some  two  or  three  only,  are  baked  in  a small  oven. 
For  laboratory  work,  however,  a special  oven  is  usually  necessary.  For 
this  purpose  the  authors  have  for  some  time  used,  and  with  very  satisfactory 
results,  a special  type  of  gas  oven.  The  oven  is  fitted  with  a tiled  sole,  and 
a baking  chamber  entirely  shut  off  from  the  gas  flame  and  products  of  com- 
bustion. At  the  front,  immediately  underneath  the  oven  doors,  four  lines 
of  gas  burners  enter  beneath  the  sole  ; from  this  hot  air  chamber  a series 
of  iron  pipes  convey  the  heat  up  around  the  sides  to  the  crown  of  the  oven, 
the  whole  of  the  oven  is  lined  on  the  outside  with  slagwool,  reducing  the 
escape  of  heat  to  a minimum.  Each  line  of  burners  can  be  regulated  separ- 
ately ; those  in  the  middle  give  an  increased  bottom  heat,  while  those  on 
the  outside  raise  the  heat  of  the  crown.  For  baking  tests  it  is  well  to  line 
the  sides  and  back  of  the  oven  with  tiles  to  act  as  upsets,  as  the  bread  is 
better  baked  with  top  and  bottom  heat  only.  The  oven  bakes  very  evenly, 
is  very  steam-tight,  and  clean  and  inexpensive  to  use  : in  fact,  is  well  adapted 
all  round  for  this  purpose. 

Another  useful  form  of  testing  oven  is  one  heated  by  electricity.  The 
temperature  is  well  under  control,  and  the  bread  is  well  and  evenly  baked. 

812.  Special  Series  of  Baking  Tests  on  British  Flours.— Following  are  the 
results  of  examination  of  a number  of  British  milled  flours,  the  quality  of 
which  is  indicated  by  the  names  attached.  They  are  set  out  in  the  tables 
on  pages  751  et  seq.  In  Fig.  109  are  given  the  sectional  outlines  of  a few 
loaves,  mostly  selected  from  this  series  and  drawn  to  a reduced  scale 
(compare  page  748).  The  sections  marked  a contain  least  water,  b another 
4 quarts,  and  c 8 quarts  more  than  a. 

The  following  are  particulars  of  each  loaf  : — 

Water  taken 
for  b Test. 

Quarts  per  Sack. 


No.  1.  Strong  British  Milled  Patent  Flour  . . . . 60 

,,  2.  Minnesota  Straight  . . . . . . . . 70 

,,  3.  Spring  American  Second  Patent  . . . . 63*5 

,,  4.  Number  2 Winter  Wheat  Patent  . . . . 56*5 

,,  5.  British  Milled  Household  Bread  Flour  . . 58*0 

,,  6.  Straight-Run  British  Bread-Making  Flour  . . 60*0 

,,  7.  British  Milled  Bakers’  Grade  Flour  . . . . 62*0 

,,  8.  English  Wheat  Flour  . . . . . . . . 56*0 


813.  Alternative  Scheme  for  Baking  Tests. — For  the  convenience  of 
those  who  prefer  to  work  entirely  with  English  weights  the  following  direct- 
ions for  making  a baking  test  are  given  : the  quantity  of  flour  used,  3 lbs., 
produces  from  4 lbs.  to  4J  lbs.  of  bread.  This  may  be  baked  either  in  tin 
or  cottage  loaves. 

First  determine  the  water-absorbing  capacity  of  the  flour  either  with 
burette  alone,  or  in  conjunction  with  the  viscometer.  Make  a dough  either 
of  full  viscometric  strength,  or  as  much  tighter  as  may  be  necessary  to  suit 
the  requirements  of  the  district.  This  can  readily  be  done  by  deciding 
once  for  all  on  a constant  deduction  from  the  water-absorbing  capacity 
according  to  the  sixty-seconds  standard. 


750 


THE  TECHNOLOGY  OF  BREAD -MAKING. 


Fig.  109. — Sectional  Outlines  through  various  Loaves. 


With  7 lbs.  of  flour,  each  ounce  of  water  used  is  equivalent  to  one  quart 
per  sack.  For  tests  on  3 lbs.  of  flour  the  water  in  ounces,  equivalent  to 
quarts  per  sack,  is  obtained  by  multiplying  by  i : thus  50  quarts  per  sack 


Analytical  and  Physical  Tests  on  Special  British  T’lours. 


COMMERCIAL  TESTING  OF  M'HEATS  AND  FLOURS. 


751 


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Baking  Te^s  on  Special  Floors. 


752 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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Baking  Tests  on  Special  Flours — continued. 


COMMERCIAL  TESTING  OF  WHEATS  AND  FLOURS.  753 


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Baking  Tests  on  Special  British  Flours — continued. 


754 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


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COMMERCIAL  TESTING  OE  WHEATS  AND  ELOURS.  755 


equal  21-4  ounces  per  3 lbs.  of  flour.  The  following  table  gives  the  pro- 
portionate quantity  of  water  for  3 lbs.  of  flour,  from  50  to  81  quarts  per 
sack  ; — 

50  quarts  = 21-4  ounces.  i 66  quarts  = 28-3  ounces. 


51 

? ? 

2L8 

9 9 

67 

99 

28-7 

99 

52 

? 5 

22*3 

9 9 

68 

99 

291 

99 

53 

? ? 

22-7 

9 9 

69 

99 

29-6 

99 

54 

?? 

231 

99 

70 

9 9 

30  0 

99 

55 

? ? 

23-5 

99 

71 

9 9 

30-4 

99 

56 

? ? 

24  0 

9 9 

72 

99 

30-8 

99 

57 

? 9 

24-4 

9 9 

73 

31-3 

99 

58 

9 9 

24-8 

99 

74 

99 

31-7 

99 

59 

9 9 

25-3 

75 

99 

321 

99 

60 

9 9 

25-7 

55 

76 

99 

32-6 

99 

61 

9 9 

261 

99 

77 

99 

33  0 

99 

62 

9 9 

26-6 

9 9 

78 

99 

33-4 

99 

63 

9 9 

27-0 

99 

79 

99 

33-8 

99 

64 

99 

27-4 

99 

80 

99 

34-3 

99 

65 

99 

27-8 

99 

81 

99 

34-7 

99 

Quantities.- 

—Flour  3 lbs.,  water  as  per  table,  salt  J 

oz.,  yeast  f 

OZ. 

all  ingredients  as  accurately  as  possible. 

Eirst,  weigh  out  the  flour,  and  put  it  in  a pan  of  sufficient  size  ; take 
out  about  an  ounce  of  the  flour,  and  put  it  aside  in  a small  cup.  Counter- 
poise a jug  on  the  balance,  and  weigh  out  the  requisite  quantity  of  water, 
warmed  to  a temperature  of  about  85°  E.  Weigh  the  salt  and  rub  it  with 
the  hands  into  the  flour  ; add  the  weighed  yeast  to  the  water  and  mix  it 
thoroughly,  taking  care  to  break  down  any  lumps  with  the  fingers.  Make 
a hole  in  the  middle  of  the  flour,  and  pour  in  the  yeast  and  water  ; stir  it 
sufficiently  to  work  enough  of  the  flour  into  the  water  to  form  a thin  sponge  : 
cover  this  over  by  drawing  up  a little  of  the  flour  from  the  sides.  Let  this 
stand  for  an  hour  in  a warm  place,  covered  over  vdtli  flannel.  Then  knead 
the  whole  into  a dough.  Clean  all  fragments  of  dough  from  the  hands, 
and  rinse  them  in  a little  of  the  reserved  flour  ; let  the  rinsings  go  into  the 
dough.  Let  the  dough  ferment  for  from  3 to  4 hours.  In  the  meantime, 
grease  and  weigh  a 4-lb.  baking  tin.  Dust  a perfectly  clean  kneading-board 
with  a little  of  the  reserved  flour,  and  turn  out  the  dough  from  the  basin, 
cleaning  it  as  thoroughly  as  possible  with  the  fingers.  Mould  the  dough 
into  a loaf,  using  up  in  so  doing  the  remainder  of  the  reserved  flour.  Trans- 
fer the  loaf  to  the  tin,  taking  care 'that  as  little  as  possible  is  lost.  Notice 
to  what  extent  the  dough  has  become  slacker  during  fermentation,  also 
whether  elastic  or  possessing  very  little  tenacity.  Let  the  dough  prove 
in  the  tin  for  about  an  hour,  then  weigh.  Next  bake  for  an  hour,  or  a,n 
hour  and  ten  minutes,  according  to  the  heat  of  the  oven.  Remove  the 
loaf  from  the  tin  and  allow  it  to  cool  ; in  an  hour  weigh  the  loaf.  Note  the 
colour  of  the  crust,  odour  of  the  bread  when  warm,  etc.  Next,  with  a 
sharp  knife,  cut  the  loaf  across  its  highest  part  ; note  the  colour,  texture, 
flavour,  and  degree  of  moisture  of  the  interior.  Keep  for  a day  or  two  and 
repeat  these  observations. 

If  it  is  desired  to  keep  a permanent  record  of  the  test,  a good  plan  is  to 
place  the  cut  loaf  on  a sheet  of  paper,  and  mark  its  size  round  with  a pencil. 
A large-sized  exercise  book,  wdthout  lines,  answers  this  purpose  very  well. 
The  other  data  may  be  so  arranged  as  to  come  inside  the  outline  of  the  loaf. 

Another  convenient  method  of  making  a baking  test  is  by  taking  a 
definite  quantity  of  water,  and  adding  flour  to  the  same  until  a dough  of 
the  right  consistency  is  obtained.  The  dough  is  then  weighed  : the  weight 


756 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  water,  yeast,  and  salt  used  always  being  a constant,  that  of  the  flour  is 
simply  obtained  by  difference  from  the  weight  of  the  dough.  A table  is 
easily  calculated  giving  equivalent  yields  per  sack  from  weight  of  dough  in 
each  case. 

General  Interpretation  of  Results. — This  it  is  hoped  has  been  rendered 
sufficiently  clear  by  the  explanatory  remarks  on  the  different  constituents 
and  properties  of  flour,  by  which  the  description  of  each  is  accompanied. 
It  must  be  remembered  that  baking  tests  on  small  quantities  of  flour  are 
only  to  be  viewed  as  comparative  ; because,  as  in  all  operations  conducted 
on  a commercial  scale,  the  results  obtained  in  practice  fall  below  those 
yielded  by  direct  tests  on  small  amounts  of  material.  Consequently,  it 
must  not  be  assumed,  because  7 lbs.  of  flour  yield  a certain  weight  of 
bread  when  baked  with  every  precaution  taken  against  loss,  that  the 
sack  of  280  lbs.  will  yield  40  times  that  weight  of  bread.  Still  it  is  well, 
from  time  to  time,  to  gauge  the  theoretical  yield  by  a small  test,  as  informa- 
tion is  thus  obtained  as  to  how  closely  the  practical  and  theoretical  yields 
agree  with  each  other.  By  keeping  a closer  watch  on  this  point,  many 
bakers  could  lessen  considerably  various  sources  of  loss  which  now  occur, 
and  are  almost  unnoticed.  In  case  it  is  wished  to  make  the  baking  test  a 
means  of  estimating  how  much  the  actual  working  yield  of  flours  is,  a careful 
comparison  must  first  be  made  between  the  results  obtained  by  a small 
baking  test,  and  one  on  a sack  of  the  same  flour.  Divide  the  yield  of  bread 
from  the  sack  by  that  from  the  quantity  used  for  small  test ; then  the  quo- 
tient may  be  used  as  a multiplier  in  order  to  convert  the  small  test  yield 
into  working  yield  per  sack.  Thus,  suppose  that  this  quotient  is,  in  the  case 
of  a 7 lb.  test,  39  : then  whatever  weight  of  bread  is  yielded  by  a 7 lb.  baking 
test,  that  quantity  multiplied  by  39  gives  the  approximate  yield  per  sack. 
But  the  figures  thus  obtained  must  not  be  relied  on  too  absolutely,  as  dis- 
turbing elements  occur  when  working  on  the  large  scale  which  are  avoided 
when  making  experimental  tests.  It  is  on  the  whole  safer  to  view  experi- 
mental tests  as  affording  information  on  the  comparative  merits  of  flours, 
rather  than  as  an  indication  of  absolute  yield  by  the  flours  when  baked 
in  large  quantities. 


CHAPTER  XXVII. 


DETERMINATION  OF  MINERAL  AND  FATTY  MATTERS  AND  HEAT  OF 
COMBUSTION  OF  WHEATS  AND  FLOURS. 

814.  Determination  of  Ash. — To  determine  ash,  weigh  a small  platinum 
dish,  and  then  add  five  grams  of  the  flour  or  meal  ; place  the  dish  on  a 
pipeclay  triangle  resting  on  the  ring  of  a retort  or  tripod  stand,  and  burn 
the  flour  by  gently  heating  with  the  bunsen.  The  volatile  matter  burns  off 
readily,  and  leaves  behind  a cake  of  ash  mixed  vrith  carbon  ; the  heat 
must  be  continued  until  the  carbon  has  disappeared,  leaving  only  the  ash, 
which  must  be  white,  or  of  a greyish  tint.  The  heat  must  not  be  raised 
too  high  ; the  burning  off  of  the  carbon  may  be  facilitated  by  occasionally 
stirring  it  with  a fine  platinum  wire.  Take  care  that  when  this  is  done 
none  of  the  ash  is  lost  by  being  removed  with  the  wire.  When  the  burning 
is  complete  allow  the  dish  to  cool  in  the  desiccator,  and  weigh.  Wlien 
wheat  or  flour  is  burned  in  this  manner,  the  resultant  ash  is  generally  infus- 
ible at  the  temperature  employed.  The  more  than  usually  ready  fusibility 
of  the  ash  is  an  indication  of  the  addition  to  flour  of  some  readily  fusible 
salt.  With  a very  fusible  ash  there  is  a difficulty  in  burning  the  flour  or 
other  substance  completely,  since  the  fused  salts  enclose  particles  of  carbon 
and  protect  them  from  the  oxygen  of  the  air.  In  the  case  of  such  an  ash, 
the  carbonaceous  mass  may  be  extracted  with  successive  quantities  of  hot 
distilled  water.  This  may  be  done  either  in  the  dish,  or  the  partly  burnt 
ash  may  be  transferred  to  a clean  mortar  and  first  reduced  to  a fine  powder 
and  then  treated  with  the  water.  The  solution  is  filtered,  and  the  carbon 
returned  to  the  platinum  dish  and  carefully  dried,  after  which  it  is  again 
heated  with  the  bunsen.  The  carbon  will  then  usually  burn  off  freely. 
The  filtrate  is  next  evaporated  to  dryness  in  the  same  dish  and  heated.  A 
carbon-free  ash  is  thus  obtained.  It  sometimes  happens  that  an  ash  encloses 
just  a few  particles  of  carbon  somewhat  obstinately.  A small  quantity  of 
hot  water  to  dissolve  soluble  matter  should  then  be  added,  and  the  solution 
distributed  by  giving  a circular  movement  to  the  dish.  The  contents  are 
evaporated  to  dryness  and  again  ignited.  This  very  simple  treatment  will 
frequently  secure  the  elimination  of  the  last  traces  of  carbon. 

Instead  of  heating  over  a bunsen  flame,  a muffle  may  be  employed  with 
advantage  in  ash  determinations.  This  piece  of  apparatus  consists  of  what 
is  really  a very  small  oven  made  of  fire-clay  and  contained  in  a muffle-furnace. 
By  means  of  a powerful  gas  burner  the  whole  muffle  is  heated  to  dull  red- 
ness, and  in  a current  of  air,  flour  and  similar  substances  burn  readily  to  a 
carbon-free  ash.  If  wished,  the  muffle  may  be  arranged  for  heating  by 
means  of  a specially  applied  electric  current. 

A very  useful  piece  of  apparatus  for  ash  determinations  consists  of 
Davies’  Crucible  Furnace,  supplied  by  Gallenkamp  & Co.,  of  which  illus- 
trations are  given  in  Fig.  110.  It  consists  of  a fire-clay  body  a,  fitted 
with  asbestos  packing  into  a sheet  iron  jacket  standing  on  3 feet.  To 
the  interior  of  the  body  are  attached  three  fire-clay  ears  or  supports,  B,  B, 


758 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


shown  in  small  right-hand  diagram ; and  on  these  the  dish  c containing 
the  substance  to  be  incinerated  is  placed.  The  heat  is  provided  by  a 
powerful  “ mekker  burner,  d,  which  passes  through  the  bottom  of  the 
furnace,  and  should  be  blocked  up  so  as  to  bring  the  top  of  the  burner  to 
within  half  an  inch  of  the  underneath  surface  of  the  dish,  c.  The  burner 
having  been  lighted  and  the  dish  placed  in  position,  the  conical  chimney 
is  placed  on  the  top  of  the  furnace.  The  whole  dish  is  thus  enclosed  and 
equally  heated,  while  the  temperature  is  under  absolute  control  and  mav 


Fig.  110. — Davies’  Furnace  with  Mekker  Burner. 


be  raised  from  the  dullest  red  heat  to  over  1000°  C.  The  use  of  the  chim- 
ney creates  a good  draught,  and  rapid  incineration  occurs.  The  new  silica 
dishes  are  very  convenient  for  use  in  determinations  of  ash.  They  are 
supplied  about  2 J inches  in  diameter  by  half  an  inch  in  height  for  special 
use  Avith  this  furnace.  When  these  dishes  are  employed  they  should  never 
be  allow'ed  to  cool  in  the  furnace,  as  the  rate  of  contraction  of  the  fire-clay  is 
greater  than  that  of  the  dish,  and  so  may  readily  lead  to  the  fracture  of 
the  latter. 

815.  Ash  Estimations,  Snyder. — Snyder  attaches  great  importance  to 
the  determinations  of  ash  in  fiour.  He  finds  that  the  percentage  amount 
of  ash  in  different  wheat  crops  varies  but  little  from  year  to  year.  The 
asli  determination  is  of  value  in  establishing  the  grade  of  a flour.  The  more 
completely  the  bran,  shorts,  and  germ  particles  are  removed,  the  smaller 
is  the  ash  content.  There  is  a definite  relationship  between  the  ash  content 
and  the  grade  of  the  flour.  The  ash  is  more  constant  in  amount  and  com- 
position than  any  other  class  of  compounds  found  in  wheat,  consequently 
tlie  ash  content  of  the  different  grades  of  flour  is  quite  uniform.  The 
patent  grades  of  flour  almost  invariably  contain  less  than  0*50  per  cent. 


DETERMINATION  OP  MINERAL  AND  PATTY  MATTERS.  759 


ash.  The  range  in  ash  content  of  the  different  grades  of  spring  wheat  flour 
is  approximately  as  follows  : — 

Per  cent.  Ash. 


Pirst  Patent 
Second  Patent 
Straight  Grade 
Pirst  Clear 
Second  Clear 


0-35  to  0-40 
0-40  to  048 
048  to  0-55 
0-60  to  0-90 
0-90  to  1-80 


Flour  made  from  fully  matured  wheat  has  the  minimum  ash  content, 
because  high  maturity  is  usually  accompanied  by  a low  ash.  The  ash 
determination  cannot  be  used  to  establish  the  comparative  value  of  two 
samples  of  flour  belonging  to  the  same  grade ; for  example,  if  two  samples 
of  flour  contain  respectively  0*36  and  040  per  cent,  ash,  the  one  with 
the  lower  per  cent,  is  not  necessarily  the  better  flour.  If,  however,  two 
samples  of  flour  contain  respectively  042  and  0-55  per  cent,  ash,  the  former 
is  a patent  grade  and  the  latter  a straight  grade  flour.  In  grading  Hun- 
garian flours,  the  ash  determination  has  been  used  successfully  by  Virodi. 
When  making  comparisons,  however,  too  strict  an  application  of  the 
results  is  not  admissible,  particularly  when  the  ash  determinations  are  made 
in  different  laboratories  and  by  different  analysts,  as  the  results  then  are 
not  always  strictly  comparable.  When  the  ash  determinations  are  made 
under  similar  conditions,  the  results  are  of  much  value  in  determining  the 
grade  of  a flour.  (Bull.  No.  85,  Agric.  Expt.  Station,  Univ.  of  Minnesota, 
1904.) 

Should  the  ash  of-  any  flour  be  higher  than  would  be  expected  from 
comparison  with  that  of  a flour  of  corresponding  colour  of  the  same  character, 
the  addition  of  mineral  substances  may  be  expected.  An  analysis  of  the 
ash  would  then  show  whether  or  not  its  composition  was  normal  for  flour, 
or  whether  some  foreign  ingredient  was  present. 

816.  Determination  of  Phosphoric  Acid,  P2O5,  and  Potash,  K2O,  in  Ash.— 

When  it  is  desired  to  estimate  both  these  constituents,  take  50  grams  of 
flour,  and  heat  in  a platinum  dish  until  the  whole  of  the  volatile  matter, 
and  most  of  the  carbon,  is  burned  off,  then  moisten  with  concentrated 
hydrochloric  acid  without  removal  from  the  dish.  Evaporate  to  complete 
dryness,  first  over  the  water-bath  and  then  by  gentle  ignition  with  the 
bunsen.  This  operation  renders  the  silica  present  insoluble  ; add  warm 
dilute  nitric  acid  to  the  ash,  and  filter  from  silica  and  any  unburnt  carbon  : 
wash  the  filtrate  with  the  warm  acid.  The  solution  thus  obtained  contains 
the  phosphoric  acid,  together  with  the  iron,  lime,  and  other  bases.  This 
solution  must  now  be  made  up  to  a definite  volume  in  a measuring  flask, 
say  250  c.c.  ; 100  c.c.  may  then  be  taken  for  the  phosphoric  acid  estima- 
tion, and  a similar  quantity  for  the  determination  of  potassium. 

817.  Phosphoric  Acid  Estimation. — ^For  the  purposes  of  this  estimation 
two  special  reagents  are  required,  known  respectively  as  “ Molybdic  solu- 
tion ’’  and  “ Magnesia  mixture.” 

818.  Molyhdic  Solution. — ^Dissolve  150  grams  of  ammonium  molybdate, 
AtuoMoOi,  in  a litre  of  water.  Make  up  a litre  of  nitric  acid  of  about  1*20 
specific  gravity  ; this  may  be  obtained  sufflciently  near  by  taking  500  c.c. 
of  commercially  pure  acid  of  14  sp.  gr.,  and  adding  thereto  an  equal  quan- 
tity of  water.  Pour  the  molybdate  solution  into  the  nitric  acid  (the  mixture 
must  not  be  reversed).  The  solution  thus  obtained  must  be  kept  in  the 
dark. 


819.  Magnesia  Mixture. — Dissolve  110  grams  of  magnesium  ehloride, 


760 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


MgCl2,  and  140  grams  of  ammonium  chloride,  AmCl,  in  1300  c.c.  of  water  ; 
dilute  this  mixture  down  to  two  litres  with  the  strongest  liquid  ammonia. 

820.  Mode  of  Analysis. — ^By  means  of  a pipette  draw  off  100  c.c.  of  the 
solution  of  ash  (made  up  as  before  directed),  and  pour  it  into  an  evaporating 
basin.  Concentrate  by  evaporation  over  a water-bath  until  the  volume  is 
reduced  to  about  30-40  c.c.,  transfer  to  a beaker,  carefully  rinsing  the  basin 
with  distilled  water  in  small  quantity.  Add  to  the  solution  thus  obtained 
about  100  c.c.  of  molybdic  solution,  and  allow  the  mixture  to  stand  for 
at  least  three  hours  at  a temperature  of  about  50°  C.  The  top  of  the  hot- 
water  oven  is  a very  good  place  on  which  to  put  the  beakers  during  this 
time  ; the  solution  may,  if  it  happens  to  be  convenient,  be  allowed  to  stand 
a longer  time — all  night,  for  instance — without  injury.  A bright  yellow 
precipitate  forms,  which  contains  all  the  phosphoric  acid,  together  with 
molybdic  acid  ; but  as  the  composition  of  the  precipitate  is  not  constant, 
it  cannot  be  weighed  for  the  purpose  of  determining  phosphoric  acid.  The 
bases  remain  in  the  filtrate.  Bring  the  precipitate  on  to  a small  filter,  and 
there  wash  with  a solution  of  ammonium  nitrate  until  the  washings  no 
longer  redden  litmus  paper.  Test  the  first  portion  of  the  filtrate  by  adding 
a drop  of  sodium  phosphate  solution  to  a very  small  quantity,  and  warm 
gently — a yellow  precipitate  shows  that  the  molybdate  has  been  added  in 
excess.  Should  there  be  no  precipitate,  some  more  molybdic  solution 
must  be  added  to  the  main  portion  of  the  solution,  which  must  then  be 
allowed  to  stand  as  before  in  a warm  place.  Next  dissolve  the  precipitate 
in  the  least  possible  quantity  of  warm  ammonia  solution  (one  part  strong 
ammonia  to  three  parts  of  water).  This  operation  is  best  performed  by 
pouring  the  warm  ammonia  on  to  the  filter.  When  this  has  passed  through, 
if  any  more  of  the  precipitate  remain  on  the  filter,  return  the  filtrate  to  the 
filter,  and  repeat  this  operation  until  the  whole  of  the  precipitate  is  dissolved. 
While  pouring  the  filtrate  back  on  the  filter,  place  another  beaker  in  order 
to  catch  any  drops  of  the  filtrate.  Wash  out  one  of  the  beakers,  and  also 
the  filter,  with  the  warm  ammonia  solution.  This  solution  contains  the 
phosphoric  acid  as  ammonium  phosphate  ; to  it  add  about  10  c.c.  of  mag- 
nesia mixture,  and  one-third  of  the  total  volume  of  strong  ammonia,  set 
aside  in  the  cold  for  three  hours,  or  a longer  time  if  wished.  Test  a small 
portion  of  the  filtrate  for  excess  of  magnesia  mixture  by  adding  a drop  of 
sodium  phosphate  solution  ; in  the  event  of  there  being  no  precipitate 
formed,  some  more  magnesia  mixture  must  be  added  to  the  solution  in 
order  to  completely  precipitate  the  phosphoric  acid.  Filter  and  wash  the 
precipitate  with  dilute  ammonia,  dry,  and  then  ignite  in  a weighed  platinum 
crucible,  and  weigh.  Before  ignition  separate  the  precipitate  as  thoroughly 
as  possible  from  the  paper  ; burn  the  latter  separately,  and  let  the  ash 
drop  into  the  cover  of  the  crucible.  The  precipitate,  after  ignition,  con- 
sists of  magnesium  pyrophosphate,  Mg2F207.  The  magnesia  mixture 
precipitates  ammonium  magnesium  phosphate,  thus  : — 

Am3P04  + MgCl2  = MgAmP04  + 2AmCl. 

Ammonium  Magnesium  Magnesium  Ammonium 

phosphate.  chloride.  ammonium  chloride. 

phosphate. 

On  ignition  the  precipitate  is  decomposed,  undergoing  the  following 
change": — 

2MgAmPO.  = Mg2P207  + 2NH3  + H2O. 

Magnesium  Magnesium  Ammonia.  i Water. 

ammonium  pyrophosphate. 

phosphate. 

The  reason  for  eompletely  detaching  the  precipitate  from  the  filter 


DETERMINATION  OF  MINERAL  AND  FATTY  MATTERS.  761 

paper  is  that  the  carbon  of  the  paper  reduces  the  phosphate  to  phosphide, 
thus  lessening  its  weight. 

Magnesium  pyrophosphate,  Mg2P207,  contains  anhydrous  phosphoric 
acid,  P2O5,  combined  with  two  molecules  of  magnesia,  MgO.  The  mole- 
cular weight  of  the  salt,  compared  with  that  of  the  acid,  is 

Mg2  P2  O2  P2  Os 

48  + 62  -1-  112  = 222.  62  + 80  = U2. 

As  222  by  weight  of  the  pyrophosphate  contain  142  by  weight  of  phos- 
phoric acid,  the  weight  of  the  precipitate,  whatever  it  may  be,  must  be 
multiphed  by  iff  = 0-64  ; this  gives  the  phosphoric  acid  in  the  quantity 
taken,  and  when  that  quantity  has  been  two-fifths  the  total  solution  from 
50  grams,  the  result,  on  being  multiplied  by  5,  gives  the  percentage  of 
phosphoric  acid. 

821.  Washing  and  Ignition  of  Precipitates.— In  all  quantitative  estima- 
tions it  must  be  remembered  that  none  of  the  substance  being  worked  on 
must  be  lost  ; therefore  when  transferring  a solution  or  precipitate  from  one 
vessel  to  another,  rinse  out  all  remaining  traces  of  the  body.  Thus,  with 
the  yellow  precipitate  produced  by  the  molybdate,  first  carefully  pour  the 
supernatant  solution  down  a glass  rod,  as 
showTO  in  Fig.  Ill,  without  disturbing  the 
precipitate.  Then  fill  the  beaker  with 
the  washing  solution  and  commence  fil- 
tering. In  order  to  remove  the  preci- 
pitate from  the  beaker,  a small  brush 
made  of  a quill  is  very  useful.  Cut  the 
stem  of  a quill  across  near  the  bottom  of 
the  feather  end,  so  as  to  leave  the  fibres 
of  the  feather  projecting  beyond  the  stump. 

Next  cut  off  all  the  feather  except  about  an 
inch  at  the  bottom  ; then  with  one  cut  of 
a sharp  scissors  or  knife  cut  the  remaining 
feather  part  to  a width  of  about  a quarter 
inch.  In  this  way  a little  brush  is  made, 
which  readily  finds  its  way  round  the  edge 
of  the  bottom  of  the  beaker.  For  wash- 
ing purposes  the  chemist  uses  a “ wash- 
bottle,'"  as  shown  in  Fig.  112. 

To  make  a wash-bottle,  fit  a good  cork 
(india-rubber  is  preferable)  to  a 20  or  24- 

ounce  flask.  Bore  through  it  two  holes,  through  which 
pass  pieces  of  glass  tubing  bent,  as  shown  in  the  figure  ; 
the  ends  of  these  tubes  must  be  rounded  off  ; to  the 
left-hand  one  is  attached,  by  means  of  india-rubber  tub- 
ing, a fine  glass  jet.  The  length  of  the  tubes  must  be 
so  arranged  that  the  direction  of  this  jet  can  be  con- 
trolled by  the  forefinger  of  the  hand  holding  the  wash- 
bottle.  To  obtain  a large  stream  of  w^ater,  pour  it  from 
the  shorter  tube  ; on  blowing  through  the  shorter  tube 
a fine  stream  of  water  is  projected  from  the  jet  on  the 
end  of  the  other  tube. 

The  precipitate  is  usually  dried  by  placing  it  to- 
gether with  the  funnel  in  the  oven.  The  operation 
of  transferring  the  precipitate  from  the  paper  to 
the  crucible  requires  great  care.  First  thoroughly  clean,  and  ignite,  the 


BOTTLE. 


Fig.  111. — Precipitate  Washlng. 


762 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


crucible  and  cover  ; allow  them  to  cool  in  the  desiccator,  and  weigh.  Cru- 
cible and  cover  must  always  be  weighed  together.  While  the  crucible  is  cooling 
get  ready  a sheet  of  glazed  paper  ; this  should  be  black  for  light -coloured 
precipitates,  and  yellow  for  any  black  precipitates.  Trim  this  paper  with 
either  a sharp  pair  of  scissors  or  knife,  so  as  to  produce  clean  cut  edges. 
Also  have  in  readiness  a piece  of  platinum  wire  about  a foot  in  length. 
Clean  the  bench  and  spread  out  the  sheet  of  paper,  place  on  it  the  crucible 
and  cover.  Take  the  filter  paper  out  of  the  funnel,  fold  it  together  at 
the  top,  and  very  gently  rub  the  sides  together  so  as  to  detach  the  precipi- 
tate. Hold  the  paper  all  this  while  over  the  glazed  sheet  ; next  open  the 
filter  and  pour  its  loose  contents  into  the  crucible.  Having  cleaned  the 
paper  as  thoroughly  as  possible,  fold  it  into  a strip  about  three-quarters  of 
an  inch  wide  ; then  roll  it  up  into  a coil,  and  wind  the  platinum  wire  tightly 
round  it.  Hold  the  bunsen  burner  at  an  angle  of  45  degrees  over  the  crucible 
cover,  and  burn  the  paper  to  an  ash  in  it  : the  paper  will  readily  leave  the 
wire  when  burned. 

In  order  to  ignite  crucibles,  they  are  suspended  in  what  are  called  “ pipe- 
clay triangles  ; these  consist  of  pieces  of  common  clay  pipe,  threaded  on 
iron  wire,  the  ends  of  which  are  twisted  together.  A c^ea?^  pipe-clay  triangle 
is  placed  on  the  ring  of  the  retort  stand,  and  then  the  crucible  placed  on  it  : 
the  crucible  is  first  gently  heated  by  the  bunsen,  and  then  more  strongly  by 
the  foot  blowpipe.  (For  most  purposes,  a mekker  burner  may  be  substituted 
for  the  foot-blowpipe).  After  ignition  the  crucible  is  allowed  to  cool  in  the 
desiccator,  and  then  weighed.  The  weight  of  the  precipitate  is  obtained 
by  deducting  from  the  gross  weight  that  of  the  crucible  and  the  filter  ash. 

822.  Weight  of  Filter  Ash  . — ^This  determination  is  usually  one  of  the 
first  made  by  the  chemical  student.  The  best  filters  hitherto  have  been 
those  of  Swedish  make,  but  now  certain  German  houses  supply  filters  almost 
if  not  quite  as  good.  The  most  convenient  sizes  for  quantitative  work  at 
2 1,  3J,  and  4J  inches  diameter.  Several  packets  should  be  ordered  at  a 
time,  and  it  should  be  stipulated  that  they  shall  be  from  the  same  parcel 
of  paper.  To  determine  the  weight  of  the  ash,  take  twenty  filters,  fold  and 
burn  them  one  or  two  at  a time,  allowing  the  ash  to  drop  in  a weighed 
crucible  ; ignite  until  a perfectly  white  ash  remains,  and  again  weigh.  One 
twentieth  of  the  weight  is  taken  as  that  of  the  ash  of  a single  filter.  Pro- 
vided the  various  sized  filters  are  of  the  same  paper,  the  ash  of  one  size  may 
be  calculated  from  that  of  another.  The  areas  of  circles  are  as  the  squares 
of  their  diameters,  consequently  the  ash  of  a 4-inch  paper  would  weigh 
four  times  as  much  as  that  of  a 2-inch  paper  ; other  diameters  could  be 
calculated  in  the  same  manner.  The  weight  of  ash  of  filter  papers  of  the 
better  quality  is  now  generally  declared  on  the  package.  Such  weight  is 
usually  so  small  that  it  may  be  neglected  in  ordinary  analyses. 

823.  Potash  Estimation. — -To  a second  portion  of  100  c.c.  of  the  solution 
already  prepared,  add  ammonia  and  'pure  ammonium  oxalate  in  slight 
excels  ; filter  off  the  precipitated  iron  and  lime  compounds.  Evaporate 
the  filtrate  to  dryness,  and  ignite  gently  in  order  to  expel  ammonium  salts. 
Dissolve  the  residue  in  a small  quantity  of  hot  water,  filter  if  necessary,  add 
liydrochloric  acid  in  slight  excess,  and  evaporate  to  dryness.  Dissolve 
the  residue  in  a very  small  quantity  of  water,  add  some  platinum  chloride 
solution  and  a drop  of  hydrochloric  acid,  and  evaporate  to  a sirupy  consis- 
tency. If  the  solution  lose  its  orange  tint  during  evaporation,  more  of  the 
platinum  chloride  solution  must  be  added.  Treat  the  moist  residue  with 
strong  alcoliol,  of  a strength  of  at  least  80  per  cent.,  filter  off  the  precipitate 
on  a small  counterpoised  or  weighed  filter  ; wash  with  alcohol  until  the 


DETERMINATION  OE  MINERAL  AND  FATTY  MATTERS.  763 


Avasliings  are  colourless.  Dry  at  100°  C.  and  weigh.  The  precipitate  con- 
sists of  KoPtCle  : 487-7  parts  by  weight  of  this  body  are  equivalent  to  94 
parts  of  K2O  (potassium  oxide). 

824.  Counterpoised  and  Weighed  Filters. — ^When  working  on  precipi- 
tates that  are  decomposed  by  a red  heat,  it  becomes  necessary  to  adopt 
some  method  other  than  ignition  in  a crucible  before  weighing.  It  is  usual 
under  these  circumstances  to  either  weigh  or  counterpoise  the  filter  before- 
hand. If  the  filter  is  to  be  weighed,  prepare  first  of  all  a test-tube  shaped 
stoppered  weighing  bottle  (these  can  be  procured  of  the  apparatus  dealer). 
Dry  this  in  the  hot-water  oven,  cool  and  weigh.  Fold  the  filter,  insert  it 
in  the  bottle,  and  dry  in  the  hot- water  oven  until  the  weight  is  constant. 
The  best  plan  is  to  set  the  filter  drying  over  night  ; the  bottle  must,  of 
course,  be  open  while  in  the  oven  ; in  the  morning  stopper  it,  allow  it  to 
cool  in  the  desiccator  and  weigh.  Return  to  the  oven  for  an  hour,  and  then 
again  weigh  ; the  two  weights  should  agree  within  a milligram  ; if  not,  the 
drying  must  be  continued  until  they  do.  The  washed  filter  and  precipitate 
must  first  be  dried  in  the  oven  in  the  ordinary  manner,  then  transferred 
to  the  w'eighing  bottle,  and  treated  exactly  as  was  the  original  filter.  The 
w'eight  of  filter  and  precipitate,  less  that  of  the  filter,  gives  the  w-eight  of 
precipitate.  Where  the  greatest  possible  accuracy  is  required  this  method 
is  to  be  preferred. 

But  when  speed  is  an  object,  a counterpoised  filter  may  be  used.  Take 
tw'o  Sw'edish  filters,  and  trim  one  of  the  pair  until  they  exactly  counterpoise 
each  other  w4ien  tested  on  the  analytic  balance.  In  this  case  they  are 
simply  to  be  weighed  direct  on  the  pans.  Place  the  one  of  the  papers,  folded 
but  unopened,  on  one  side  of  the  funnel,  and  then  put  in  the  other,  opened 
in  the  usual  w^ay.  Filter  and  wash,  then  dry  both  filters,  and  when  w^eigh- 
ing,  again  use  the  empty  paper  as  a counterpoise,  placing  it  on  the  w-eight  side 
of  the  balance.  In  this  method  of  working,  the  assumption  is  that  the 
tw'o  papers  being  of  the  same  weight  to  start  with,  and  taken  from  the  same 
lot  of  filters,  will  contain  the  same  weight  of  moisture.  Further,  that  as 
they  are  subjected  to  the  same  treatment,  they  will  also  counterpoise  each 
other  at  the  final  w^eighing.  The  use  of  counterpoised  filters  effects  a great 
saving  of  time,  and  yields  results  of  sufficient  accuracy  for  most  technical 
purposes.  t • 

825.  Determination  of  Fat. — ^The  fat  of  meal  and  flour  is  estimated  by 
treatment  with  either  ether  or  rectified  light  petroleum  spirit.  Either  of 
these  reagents,  especially  if  warm,  dissolves  fat,  together  wdth  any 
traces  of  resinous  matter,  with  readiness,  while  none  of  the  other  constitu- 
ents of  w heat  is  soluble  in  these  compounds.  In  order  to  effect  the  estima- 
tion, a w^eighed  quantity  of  the  sample  is  first  dried  in  the  hot-water  oven, 
and  then  treated  with  repeated  quantities  of  ether  or  petroleum  spirit  until 
a small  quantity  of  the  reagent  leaves  no  greasy  stain  on  being  evaporated 
on  a piece  of  white  filter  paper.  If  ether  be  used,  that  known  as  “ methy- 
lated may  be  employed.  Rectified  light  petroleum  spirit,  distilling 
entirely  below  80°  C.,  and  leaving  no  weighable  residue,  can  be  purchased 
from  dealers  in  ehemicals  for  analysis.  Both  ether  and  petroleum  spirit 
are  extremely  volatile  and  inflammable  ; both  give  off  at  ordinary  tem- 
peratures an  inflammable  and  explosive  vapour.  The  greatest  care  must 
therefore  be  observed  in  working  wdth  these  substances. 

826.  Soxhlett’s  Extraction  Apparatus. — ^As  ether  and  petroleum  spirit 
are  so  volatile  and  inflammable,  special  forms  of  fat  extraction  apparatus 
have  been  devised  for  this  estimation.  Their  object  is  to  keep  the  liquids 
out  of  contact  wdth  the  air  of  the  room,  and  also  to  make  a small  quantity  of 


764  THE  TECHNOLOGY  OF  BREAD-MAKING. 

the  reagent  suffice  by  repeatedly  doing  duty  Among  the  most  effective 
of  these  apparatus  is  that  devised  by  Soxhlett,  and  illustrated  in  Fig.  113, 
in  which  the  complete  apparatus  is  shown  in  section. 

Directions  will  first  be  given  for  the  fitting  up  of  the  apparatus,  and  then 
its  use  and  the  principles  involved  therein  will  be  described.  The  apparatus 
proper,  known  familiarly  as  a “ Soxhlett,”  is  that  portion  a c ; this  is  to 
be  procured  from  the  apparatus  dealer.  Fit  the  lower  end  by  means  of  a 
well-fitting  cork  into  a good  Bohemian  flask,  n,  preferably  one  vdth  a rounded 
bottom,  and  about  four  or  six  ounces  capacity.  To  the  top  of  the  Soxhlett, 

a,  fit  another  cork,  and  through  it  bore  a 
hole  for  the  tube  of  a Liebig’s  condenser,  j k. 
The  body  of  this  condenser  should  be  from 
18  inches  to  2 feet  in  length  ; the  inner  tube 
must  have  an  internal  diameter  of  half  an 
inch, and  must  not  be  constricted  at  the  end — 
these  directions  are  of  considerable  import- 
ance. Fit  a cork  and  bent  leading  tube  to 
k.  Fit  up  a four  ounce  flask,  m,  with  a cork 
through  which  passes  a leading  tube  and 
two-bulbed  thistle  funnel,  1.  Pour  sufficient 
mercury  in  this  funnel  to  just  All  the  space 
between  the  two  bulbs.  Instead  of  this  flask 
and  funnel,  mZ,  a small  U-tube,  about  f inch 
diameter,  and  with  limbs  5 inches  long,  may 
be  employed.  By  means  of  a piece  of  glass 
tubing  bent  to  shape,  this  U-tube  may  be 
corked  direct  to  the  top  of  the  condenser, 
k,  and  then  sufficient  mercury  added  to  just 
cover  the  bend.  The  whole  apparatus  is  then 
self-contained,  which  is  a decided  advan- 
tage. With  a condenser  of  ample  length 
this  mercury  arrangement  may  be  entirely 
dispensed  with,  and  the  top  of  the  condenser 
tube  simply  covered  with  a test-tube  or  small 
beaker.  The  more  modern  spiral  worm  con- 
denser may  wdth  advantage  be  substituted  for  the  older  straight  tube 
Liebig.  A small  water  bath,  o,  is  also  required. 

Dry  10  or  20  grams  of  the  meal  or  flour  for  one  or  two  hours  in  the  hot- 
water  oven,  taking  as  much  as  can  conveniently  be  placed  in  the  apparatus. 
Take  a square  piece  of  Swedish  Alter  paper,  big  enough  to  fold  up  into  a 
little  cylindrical  case,  i h.  Fold  this  so  that  no  liquid  can  escape  through 
the  case  except  through  the  pores  of  the  paper,  even  when  full.  This  speci- 
ally folded  Alter  is  easily  prepared  by  taking  the  end  of  a ruler,  or  other 
flat-ended  cylinder,  placing  the  end  in  the  middle  of  the  paper,  then  doubling 
it  across  the  diagonals,  and  folding  the  corners  round  the  ruler.  Transfer 
the  meal  to  the  Alter,  and  drop  this  into  the  Soxhlett. 

For  flours,  instead  of  this  folded  filter,  it  is  convenient  to  use  a small 
glass  percolator  : this  is  easily  made  by  taking  a piece  of  glass  tubing  of 
such  a size  as  to  drop  easily  into  the  Soxhlett,  and  cutting  it  to  about  the 
same  length  as  the  case,  i h.  A piece  of  filter  paper  is  then  tied  securely  to 
the  lower  end.  Ether  percolates  through  flours  with  extreme  slowness  ; 
and  consequently,  when  a paper  case  is  used,  much  of  the  ether  simply  finds 
its  way  through  the  sides  of  the  case,  without  penetrating  the  interior  of 
the  mass  of  flour.  Attach  the  Soxhlett  to  the  flask,  n,  and  place  it  on  the 
batli.  Next  see  that  all  lights  are  extinguished  within  10  or  12  feet  of  the 


Fig.  113. — Soxhlett’s 
Extraction  Apparatus. 


DETERMINATION  OF  MINERAL  AND  FATTY  MATTERS.  765 


apparatus.  Bring  the  ether  or  petroleum  spirit  from  an  outer  store-room, 
and  pour  it  in  the  Soxhlett  through  a funnel  until  the  level  of  the  liquid 
rises  to  g ; it  will  then  syphon  over  into  the  flask,  n.  Next  pour  in  about 
an  ounce  more  of  the  liquid,  and  at  once,  before  doing  anything  else,  carry 
the  ether  or  spirit  back  to  the  store-room.  Next  attach  the  condenser,  j Jc, 
and  push  in  the  corks  as  tightly  as  possible.  Support  the  apparatus  by 
means  of  a retort  stand,  p q r,  and  ring.  If  using  the  flask,  m,  place  it  on 
a shelf  conveniently  near  and  connect  the  leading  tube  at  k to  that  of  the 
flask  by  means  of  a piece  of  india-rubber  tubing.  Connect  the  lower  end 
of  the  condenser  to  a water  tap  by  means  of  india-rubber  tubing,  and  ar- 
range another  piece  to  the  upper  end  to  take  the  waste  water  to  the  drain. 
Bring  a water  supply  to  the  bath,  and  also  fix  an  india-rubber  tube  leading  to 
the  drain.  Arrange  a bunsen  underneath  the  bath.  Before  going  further, 
once  more  examine  each  cork  and  joint,  to  see  that  all  are  air-tight.  Turn 
on  a stream  of  water  through  the  condenser.  Next  light  the  bunsen,  and 
keep  it  going  with  a gentle  flame.  The  ether  will  soon  boil  ; when  it  does 
so,  arrange  the  flame  so  as  to  keep  it  boiling  steadily,  but  not  too  violently. 
The  ether  vapour  ascends  through  d e,  and  drives  the  air  before  it  up  through 
the  condenser,  and  out  of  the  flask,  m,  through  the  mercury  in  the  funnel,  1. 
As  soon  as  the  ether  vapour  reaches  the  condenser,  it  is  condensed  and 
runs  back  in  a small  stream,  dropping  into  the  filter,  i h.  The  complete 
condensation  is  furthered  by  the  use  of  the  mercury  funnel,  which  offers  a 
slight  resistance,  and  thus  prevents  the  escape  of  ether  while  still  allowing 
a passage  for  air.  As  the  condensed  ether  drops,  the  body  of  the  Soxhlett 
fills  up  to  the  level  of  g ; the  ether  then  returns  to  the  flask  by  means  of  the 
syphon,  fgh.  It  carries  back  with  it  the  fat  it  has  dissolved  out  of  the  meal ; 
as  the  ether  continues  boiling  in  n,  pure  ether  is  continuously  distilled  over 
the  fat  remaining  in  the  flask.  By  this  treatment  one  quantity  of  ether 
can  be  made  to  act  on  the  same  meal  an  indefinite  number  of  times.  If  all 
the  joints  are  in  good  condition,  no  odour  of  ether  will  be  observed  during 
the  whole  of  the  time  the  apparatus  is  in  work.  The  apparatus  may  be 
allowed  to  remain  in  action  for  an  hour  or  more.  Turn  out  the  bunsen 
underneath  the  bath,  and  also  all  other  lights  in  the  vicinity.  Take  the 
apparatus  to  pieces,  cork  up  the  lower  flask  ; test  a drop  of  the  ether  remain- 
ing in  the  Soxhlett,  in  order  to  see  if  it  contains  any  fat  by  allowing  it  to 
fall  on  a piece  of  white  filter  paper,  when  it  should  produce  no  stain. 

The  ether  solution  requires  next  to  be  evaporated  to  dryness  and  the 
fat  weighed. 

827.  Treatment  of  [Ethereal  Solution. — ^Having  obtained  an  ethereal  or 
petroleum  spirit  solution,  containing  all  the  fat  in  the  sample  being  analysed, 
filter  if  not  perfectly  clear.  It  will  be  next  necessary  to  drive  off  the  solvent, 
and  thus  procure  the  fat  in  a suitable  state  for  weighing.  Take,  for  the 
purpose  of  evaporation,  one  of  the  counterpoised  glass  dishes,  and  tare  it 
in  the  balance,  making  a note  of  its  weight  against  the  counterpoise.  It 
must  here  again  be  mentioned  that  ether  vapour  is  not  only  inflammable, 
but  also  highly  explosive  when  mixed  with  air.  In  default  of  special  appara- 
tus for  the  purpose,  heat  the  water-bath  to  boiling,  and  then  take  it  into 
a room  in  which  there  are  no  lights.  Partly  fill  the  dish  with  the  ether  solu- 
tion, place  it  in  the  bath,  and  allow  it  to  evaporate  spontaneously,  refill 
from  time  to  time  from  the  flask,  and  finally  rinse  the  flask  with  a little 
pure  ether,  pouring  the  rinsings  into  the  dish.  If  necessary,  heat  some 
more  water  and  replace  that  in  the  bath  as  it  becomes  cool.  When  most 
of  the  solvent,  whether  ether  or  petroleum  spirit,  has  been  thus  driven  off, 
place  the  dish  in  the  oven,  heat  for  two  or  three  hours,  and  then  weigh 
until  constant.  Well  ventilate  the  room  before  any  lights  are  brought  in. 


766 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


By  this  method  the  whole  of  the  ether  used  is  lost  ; but  if  wished  the  greater 
part  may  be  recovered  by  connecting  the  flask  by  means  of  a cork  and 
leading  tube  to  a condenser  and  distilling  off  most  of  the  ether,  after  which 
the  concentrated  fatty  solution  may  be  poured  from  the  flask  into  the  dish, 
and  then  the  flask  rinsed  out  wdth  successive  very  small  quantities  of  ether. 
Some  operators  prefer  to  use  instead  of  the  flask  n,  a small  conical  flask, 
which  is  itself  weighed.  The  whole  of  the  ether  is  then  distilled  off,  and 
the  residue  dried  off  to  constant  weight  in  the  flask  itself. 

828.  Heat  of  Combustion. — 'In  view  of  the  bearing  which  the  heat  of 
combustion  has  on  the  nutritive  value  of  bread  and  other  bodies  as  ex- 
plained in  paragraph  641,  the  following  description  of  the  apparatus  em- 
ployed for  its  estimation  will  be  of  service.  The  principle  involved  con- 
sists of  burning  a weighed  quantity  of  the  substance  in  an  atmosphere  of 
compressed  oxygen  and  determining  the  quantity  of  heat  thus  evolved. 


A 


Fig.  114. — Berthelot-Mahler  Bomb  Calorimeter. 


DETERMINATION  OP  MINERAL  AND  PATTY  MATTERS.  767 


The  apparatus  was  originally  designed  by  Bertlielot,  and  has  been  improved 
by  Mahler.  The  following  is  a description  of  what  is  known  as  the  Berthe- 
lot-Mahler  Bomb  Calorimeter,  supplied  by  Gallenkamp  & Go.  It  consists 
first  of  a bomb  or  cylinder,  a,  Pig.  113,  made  of  fine  steel  and  enamelled 
or  lined  with  platinum.  This  cylinder  has  a tightly  fitting  cover,  h,  and 
a collar  by  which  it  can  be  securely  screwed  down  to  the  vessel  by  the  double 
armed  key,  c.  The  material  to  be  burned  is  compressed  into  a pellet  by 
means  of  a press,  d,  and  then  weighed.  The  pellet  is  then  placed  in  a small 
platinum  capsule  which  is  suspended  by  platinum  wires,  the  terminals 
of  which  pass  through  the  cover  of  the  bomb,  e e.  A coil  of  fine  iron  wire 
is  stretched  between  the  two  platinum  wires,  and  on  passing  an  electric 
current  through  this,  it  becomes  sufficiently  hot  to  ignite  the  substance, 
on  which  the  coil  rests.  The  bomb  having  been  charged,  the  cover  is  fas- 
tened do’wn  and  oxygen  is  introduced  through  a valve,  /,  in  the  cover  until 
a pressure  of  twenty  atmospheres  is  attained  as  registered  by  the  pressure 
gauge,  g.  The  valve  is  then  closed  and  the  bomb  placed  in  a metal  recep- 
tacle, h h,  containing  a definite  quantity  of  water  at  a known  temperature 
in  which  it  is  submerged.  A metal  stirrer  is  attached  to  the  spindle,  z,  and 
operated  by  a small  motor  geared  to  the  pulley,  j ; this  keeps  the  water 
in  the  receptacle  in  motion  during  the  whole  operation.  A carefully  cali- 
brated thermometer,  k,  graduated  in  hundredths  of  a degree,  is  immersed 
in  the  water  and  the  temperature  accurately  read  by  the  small  telescope,  1. 
On  passing  an  electric  current  through  the  coil  of  wire,  the  substance  con- 
tained in  the  bomb  is  ignited,  and  immediately  burns.  The  resultant  heat 
passes  through  the  metal  of  the  bomb  and  is  absorbed  by  the  water. 
When  the  temperature  of  the  water  as  registered  by  the  thermometer  has 
attained  its  maximum,  the  number  of  grams  of  water  multiplied  by  the 
rise  in  degrees  of  temperature  gives  the  number  of  heat  units  evolved,  and 
from  this  the  heat  of  combustion  per  gram  of  substance  being  tested  is 
calculated.  As  the  passage  of  the  electric  current  in  itself  evolves  a certain 
amount  of  heat,  a blank  experiment  is  made  and  the  rise  of  temperature 
thus  caused  is  deducted  from  that  obtained  in  the  actual  test.  The  amount 
of  heat  required  to  raise  a kilogram  of  water  through  1°  C.  is  termed  a 
Calorie,  and  the  number  of  Calories  evolved  by  the  combustion  of  1 gram 
of  the  substance  is  the  measure  of  its  heat,  or  energy-producing,  value. 
The  following  are  numbers  of  Calories  evolved  by  1 gram  of  each  of  the 
undermentioned  substances,  according  to  Hutchison  and  Snyder  respec- 
tively : — 


"■'1 

Hutchison. 

Snyder. 

Protein 

..  41 

5-9 

Fat 

. . 9-3 

9-3 

Carbohydrate 

..  41 

4-2 

CHAPTER  XXVIII. 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 

829.  Soluble  Extract. — ^The  proportion  of  a meal  or  flour  soluble  in  cold 
water  is  of  importance  in  judging  of  the  character  of  a sample.  This  sol- 
uble portion  is  termed  the  “soluble  extract/’  or  “cold  aqueous  extract,” 
and  consists  of  the  soluble  proteins,  sugars  (maltose  and  sucrose),  gum 
(dextrin),  soluble  starch,  and  soluble  inorganic  constituents  of  the  grain, 
principally  potassium  phosphate.  The  solution  made  for  the  purpose  of  this 
estimation  is  also  available  for  the  determination  of  the  acidity  and  soluble 
proteins.  On  the  addition  of  even  cold  water  to  a flour  or  meal,  chemical 
action  immediately  commences,  the  soluble  starch  being  dissolved  out  of 
any  abraded  or  ruptured  starch  granules,  and  acted  on  by  any  diastase 
present.  As  a consequence,  the  soluble  extract  varies  with  the  time  the 
solution  is  allowed  to  stand  in  contact  with  the  flour  or  meal  ; absolute 
uniformity  must  therefore  be  adopted  in  the  method  employed  for  making 
this  soluble  extract.  The  following  is  a convenient  standard  method  : — 
Weigh  out  25  grams  of  the  flour,  and  transfer  to  a clean  dry  flask  of  from  500 
-700  c.c.  capacity,  add  250  c.c.  of  cold  distilled  water,  cork  the  flask  with 
a clean  cork,  and  shake  up  vigorously  for  five  minutes  by  the  clock.  One 
or  two  minutes’  shaking  is  sufficient  to  break  up  any  little  balls  of  flour, 
but  in  order  to  ensure  perfect  solution  the  longer  time  is  recommended. 
Xext,  let  the  flask  stand  for  25  minutes,  making  half-an-hour  from  the 
time  of  commencement.  In  the  meantime  arrange  a 10 -inch  coarse  Alter 
paper,  in  a funnel  5 inches  in  diameter,  both  being  quite  dry,  and  place 
a clean  dry  beaker  or  flask  to  receive  the  filtrate.  At  the  end  of  the  half- 
hour  most  of  the  insoluble  portion  of  the  flour  will  have  subsided  ; remove 
the  cork  and  carefully  decant  as  much  as  possible  of  the  supernatant  liquid 
on  to  the  Alter  without  disturbing  the  sediment.  The  filtrate  will  at  first 
be  cloudy  ; return  it  to  the  filter  until  quite  clear,  then  collect  for  analysis. 
By  working  in  this  way,  there  being  practically  none  of  the  solid  matter 
of  the  flour  on  the  filter,  any  subsequent  changes  in  the  wet  flour  do  not 
affect  the  results.  As  the  speed  of  filtering  varies  with  different  filter  papers, 
it  was  often  found,  when  both  flour  and  water  were  placed  on  the  filter 
together,  that  a higher  extract  was  yielded  by  the  same  flour,  simply  as  a 
result  of  a slower  filtering  paper  ; there  is  a further  disadvantage  in  that, 
when  any  of  the  solid  matter  of  the  flour  was  allowed  to  get  on  the  filter,  it 
greatly  impeded  the  rapidity  of  filtering.  Twenty-five  c.c.  of  this  clear 
filtrate  must  next  be  evaporated  to  dryness  in  order  to  ascertain  the  amount 
of  matter  it  holds  in  solution.  The  glass  dishes  that  were  used  for  the 
moistures  are  also  well  adapted  for  this  purpose.  Having  tared  a clean 
dish  against  its  counterpoise,  and  noted  any  difference  in  weight,  pour  25 
c.c.  of  the  filtrate  into  the  dish,  and  evaporate  to  dryness  over  the  water- 
bath. 

For  all  practical  purposes,  any  soluble  extract  obtained  by  the  above 
process  may  be  regarded  as  pre-existing  in  the  soluble  state  in  the  flour, 
as  in  baking  operations  there  can  be  no  difference  between  matter  already 

768 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  769 

soluble  and  matter  rendered  soluble  by  other  agents  present  in  the  flour 
during  the  period  elapsing  before  filtration. 

In  case  it  is  required  to  differentiate  between  the  soluble  and  readily 
rendered  soluble  matters  of  flour,  the  diastase  of  the  flour  may  first  be 
destroyed  by  boiling  the  flour  with  95  per  cent,  alcohol.  The  moisture  in 
the  flour  must  first  be  determined,  as  it  has  to  be  allowed  for  in  arranging 
the  strength  of  the  alcohol  employed.  The  operation  may  be  carried  out 
in  the  following  manner  : — Weigh  out  25  grams  of  the  flour,  containing  say 
12  per  cent,  of  moisture  ; 25  grams  must  obviously  contain  3 grams  of 
water.  As  5 c.c.  of  water  will  reduce  95  c.c.  of  absolute  alcohol  to  95  per 
cent,  strength,  then  the  water  present  in  25  grams  of  flour  will  reduce  a 
proportionate  quantity. 

As  5 : 3 : : 95  : 57  c.c.  absolute  alcohol. 

In  a clean  dry  flask  add  57  c.c.  of  absolute  alcohol  to  the  flour,  or  other 
quantity  as  calculated  from  the  moisture.  This  alcohol  will  then  be  of 
95  per  cent,  strength.  Next  add  a further  100  c.c.  of  previously  prepared 
95  per  cent,  alcohol,  and  boil  for  an  hour,  after  fitting  to  the  flask  a return 
condenser  so  as  to  restore  the  alcohol,.  Next  filter  and  air-dry  the  flour, 
then  transfer  to  a flask  cmd  determine  soluble  extract  as  previously  directed. 

830.  Water-Bath. — 'This  consists  of  a vessel,  usually  of  copper,  about 
4 inches  deep,  and  of  other  dimensions  varying  with  the  number  of  dishes 
for  which  it  is  made.  In  case  of  a bath  specially  prepared  for  flour  extracts 
amd  similar  work,  one  to  hold  12  dishes  is  a convenient  size  ; its  actuad 
dimensions  would  then  be  12  in.  X 15  in.  X 4 in.  The  top  contains  a 
series  of  holes  about  2J  ins.  diameter,  one  for  each  dish  ; to  each  of  these 
is  fitted  a cover.  A water  supply  apparatus,  similar  to  that  used  with  the 
hot-water  oven,  is  a.ttached  to  the  side  of  the  h&tli.  It  is  very  convenient 
to  have  a series  of  flanged  glass  rings  to  drop  into  these  holes,  on  which  the 
dishes  are  placed  ; they  are  thus  prevented  from  coming  in  actual  contact 
with  the  metal.  These  rings  are  similar  in  shape  to  the  top  of  a beaker,  and 
are  about  an  inch  deep  ; in  fact,  the  tops  of  broken  beakers  a.re  often  cut 
off  and  utilised  for  this  purpose.  They  must  be  of  such  a diameter  that 
they  just  fit  in  the  holes  of  the  bath,  being  supported  by  their  flanges.  The 
reason  for  their  use  is  that  the  outsides  of  the  dishes  are  liable  to  pick  up 
foreign  matter  from  the  metal  of  the  bath,  and  so  have  their  weight  increased. 
When  the  dishes  are  allowed  to  come  in  contact  with  the  metal  of  the  bath, 
they  must  be  carefully  wiped  clea.n  before  being  dried.  In  use,  the  hot- 
water  bath  should  have  its  feed  apparatus  so  regulated  as  to  maintain  the 
water  in  the  bath  at  a.  depth  of  about  half  a,n  inch  ; the  water  must  be  kept 
boiling  at  a moderate  ra,te  by  mea.ns  of  a bunsen  burner.  The  eva,poration 
of  the  fluid  in  the  dishes  then  proceeds  by  the  auction  of  the  steam. 

831.  Soluble  Extract,  continued. — -On  the  contents  of  the  dish  having 
evaporated  to  dryness,  place  it  in  the  hot-water  oven  for  24  hours,  and  then 
weigh.  In  order  to  calculaote  the  percentage  of  soluble  extract,  it  must  be 
remembered  that  by  adding  250  c.c.  of  water  to  25  grams  of  flour  a 10  per 
cent,  filtered  solution  has  been  prepared.  It  follows  that  25  c.c.  of  the 
solution  contains  the  soluble  extract  of  2-5  grams  of  flour  ; the  weight 
must  therefore  be  multiplied  by  40  in  order  to  give  the  percentage.  It 
ought  to  be  mentioned  that  in  strictness  this  is  not  quite  correct,  as  no  allow- 
ance is  made  for  the  moisture  of  the  flour,  so  that,  as  25  grams  of  flour 
contain  about  3 grams  of  water,  we  rea.lly  have  more  nearly  253  c.c.  than  250 
of  water  present.  As,  however,  the  results  are  only  used  for  comparcAive 
purposes,  this  is  not  of  practical  importemce.  If  wished,  the  soluble  extract 

3 D 


770 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


may  be  calculated  out  to  the  exact  quantity,  when  the  percentage  of  moisture 
has  been  ascertained. 

832.  Acidimetry  and  Alkalimetry. — ^The  measurement  of  the  amount  of 
either  free  acid  or  free  alkali  in  a solution  is  often  an  operation  of  consider- 
able chemical  importance.  Thus,  in  flours  or  meals,  the  acidity  is  occa- 
sionally determined  ; the  measure  of  acidity  being  often  a useful  help  in 
deciding  whether  or  not  a sample  of  flour  or  wheat  is  unsound.  Flours 
which  contain  bran  or  germ  develop  acidity  much  more  rapidly  than  those 
thoroughly  purified  from  the  offal.  This  acidity  is  caused  usually  by  the 
presence  of  lactic  acid,  and  is  produced,  as  has  been  previously  stated,  by 
the  action  of  the  lactic  ferment.  This  organism  is  always  found  in  greater 
or  less  numbers  on  the  bran  and  germ  of  the  grain,  and  acts  by  converting 
the  sugar  into  lactic  acid.  This  action  is  much  favoured  by  damp  and 
varmth. 

833.  Normal  Solutions  : Sodium  Carbonate. — ^The  process  of  acidimetry 
(acid  measuring)  belongs  to  the  department  of  volumetric  analysis,  and 
hence  it  becomes  necessary  to  explain  some  of  the  terms  used  in  that  branch 
of  analytic  work.  There  is  required  a set  of  standard  acids  and  alkalies  ; 
that  is,  solutions  of  known  and  definite  strengths,  and  an  indicator.  The 
standard  solutions  are  usually  made  up  to  normal  strength.  It  is  requisite 
that  the  exact  meaning  of  this  term  normal  should  be  understood.  Normal 
solutions  are  prepared  so  that  one  litre  at  16°  C.  shall  contain  the  hydrogen 
equivalent  of  the  active  reagent,  weighed  in  grams.  It  follows  that  normal 
solutions  of  acids  and  alkalies  are  all  of  the  same  strength,  and  that  equal 
quantities  exactly  neutralise  each  other.  Decinormal  solutions  are  pre- 
pared by  diluting  normal  solutions  to  one -tenth  their  original  strength,  and 
are  shortly  designated  at  N/10  solutions.  The  acid  a.nd  alkali  most 
commonly  used  are  sulphuric  acid,  H2SO4,  and  sodium  hydroxide  (caustic 
soda),  NaHO.  Both  these  substances  are  extremely  deliquescent,  and  so 
cannot  be  easily  weighed  with  accuracy.  It  is  customary,  therefore,  first 
to  make  up  as  a starting  point  a normal  solution  of  sodium  carbonate, 
Na2C03.  Directions  follow  for  starting  from  this  point  and  making  up  the 
necessary  solutions. 

Normal  sodium  carbonate  contains  53  grams  of  the  dry  salt  to  the  litre  ; 
as  this  solution  is  seldom  employed  for  any  other  purpose  than  that  of  pre- 
paring other  solutions,  a quarter  of  a litre  only  need  be  made.  Take  about 
18  to  20  grams  of  the  pure  dry  salt,  heat  to  dull  redness  in  a platinum  dish 
or  crucible  for  about  15  minutes,  allow  to  cool  under  the  desiccator,  and 
then  weigh  out  exactly  13-25  grams.  Transfer  this  weight  to  a 250  c.c.  flask, 
and  two -thirds  fill  with  water,  shake  up  until  the  whole  of  the  salt  is  dissolved, 
and  then  fill  up  the  flask  to  the  graduation  mark.  Keep  the  solution  in  a 
clean  dry  stoppered  bottle. 

834.  Indicators. — ^The  next  step  is,  with  the  aid  of  this  solution,  to 
make  up  a soluton  of  normal  sulphuric  acid.  From  a study  of  elementary 
chemistry,  the  student  already  knows  that  it  is  usual  to  determine  whether 
or  not  a substance  is  acid  or  alkaline  by  observing  its  action  on  litmus. 
Acids  turn  a solution  of  that  body  red,  the  blue  colour  being  restored  by 
excess  of  alkali  ; when  the  solution  is  neutral  its  colour  is  violet.  Bodies 
such  as  litmus,  wliich  are  used  in  order  to  determine  the  completion  of  any 
particular  action,  are  termed  “ indicators.'’ 

Litmus. — To  prepare  the  litmus  solution,  take  some  litmus  grains  and 
boil  with  distilled  water  ; let  the  liquid  stand  for  some  hours,  and  decant 
off  the  clear  supernatant  solution.  Let  this  solution  again  boil,  and  add 
nitric  acid,  drop  by  drop,  until  it  assumes  a reddish-violet  colour  ; boil  for 


771 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 

a time,  and  the  colour  once  more  becomes  blue.  Continue  this  treatment 
with  nitric  acid  until  a violet  tint  is  obtained  that  remains  permanent  after 
boiling.  The  reason  for  this  boiling  is  that  the  litmus  contains  some  earthy 
and  alkaline  carbonates  ; the  carbon  dioxide  liberated,  on  addition  of  an 
acid,  gives  the  litmus  a reddish  tint,  and  so  requires  to  be  expelled  by  boiling. 
The  litmus  solution  should  be  kept  in  an  open  bottle  supplied  with  a small 
dropping  pipette,  by  which  a small  quantity  can  be  removed  when  wanted. 
If  tins  litmus  solution  be  kept  in  a closed  bottle,  it  is  apt  to  become  colour- 
less ; the  colour  may  be  restored  by  pouring  the  solution  in  an  evaporating 
dish,  and  thus  exposing  it  for  a short  time  to  the  action  of  the  atmosphere. 

Phenolphthalein. — Another  indicator,  much  more  delicate  than  litmus, 
is  phenolphthalein  ; this  body,  however,  possesses  the  disadvantage  of 
being  unsuitable  in  the  presence  of  carbon  dioxide  or  ammonia.  Phenol- 
phthalein is  a white  or  broAvnish  powder,  of  which  one  part  is  dissolved 
in  30  parts  of  90  per  cent,  alcohol,  and  one  or  two  drops  of  the  solution 
employed  for  each  estimation.  The  addition  of  phenolphthalein  to  an 
acid  solution  produces  no  colour,  but  with  the  slightest  excess  of  alkali  an 
intense  magenta  red  is  produced. 

Methyl  Orange. — Under  this  name  is  prepared  another  body,  also  most 
useful  as  an  indicator.  It  is  a yellowish  brown  powder,  one  part  of 
which  may  be  dissolved  in  30  parts  of  90  per  cent,  alcohol,  and  two  or 
three  drops  employed  for  each  estimation.  In  alkaline  solutions  methyl 
orange  has  a yellow  tint,  which  changes  to  pink  or  red  with  the  slightest 
excess  of  acid.  Methyl  orange  is  absolutely  unaffected  by  carbonic  acid, 
and  also  by  organic  acids.  On  the  other  hand,  it  is  sensitive  to  the 
action  of  ammonia,  and  is  well  adapted  for  titrating  that  body.  A curious 
result  of  the  action  of  these  last  two  indicators  is  that  water  from  chalk  or 
limestone  formations  containing  calcium  carbonate  in  solution  reacts  alka- 
line to  methyl  orange  and  acid  to  phenolphthalein.  The  dissolved  carbonate 
affects  the  methyl  orange,  which  is  insensible  to  the  carbonic  acid,  Avhile 
the  phenolphthalein  is  caused  to  give  an  acid  reaction  by  the  excess  of 
carbonic  acid  present.  , 

835.  Normal  Sulphuric  Acid. — -Of  normal  and  decinormal  acids  and 
alkalies,  two  litres  of  each  is  a convenient  quantity  to  prepare  ; these  solu- 
tions are  best  kept  in  stoppered  Winchester  quarts,  which  hold  just  over 
the  two  litres.  Normal  sulphuric  acid  contains  49  grams  of  H2SO4  to  the 
litre.  Take  about  65  to  70  c.c.  of  pure  sulphuric  acid  of  1-840  specific  gravity 
(Le.,  strongest  acid  of  commerce),  mix  this  with  four  or  five  times  its  volume 
of  water,  allow  to  cool,  and  then  make  up  to  exactly  tw'o  litres  with  distilled 
w'ater.  With  acid  of  full  strength  the  solution  will  now"  be  too  strong  ; it 
must  next  be  tested  against  the  normal  sodium  carbonate.  Fill  a 50  c.c. 
burette  with  the  acid  solution  ; with  a pipette  pour  20  c.c.  of  the  normal 
sodium  carbonate  into  a porcelain  evaporating  basin,  and  add  tw  o or  three 
drops  of  methyl  orange.  Note  the  height  of  the  acid  in  the  burette,  and 
proceed  to  add  it  cautiously,  little  by  little,  to  the  carbonate  in  the  dish. 
Wait  between  each  addition  until  the  effervescence  is  over.  Continue 
adding  the  acid  until  the  neutral  tint  betw^een  yellow"  and  pink  is  rea-ched. 
Read  the  height  of  the  acid  in  the  burette,  deduct  the  first  reading  ; the 
difference  is  the  amount  of  acid  required  to  neutralise  the  20  c.c.  of  normal 
sodium  carbonate.  Let  us  suppose  that  this  amount  is  18-65  c.c.,  then  as 
with  normal  solutions  equal  quantities  should  exactly  neutralise  each  other, 
it  is  evident  that  the  18-65  c.c.  require  to  be  made  up  with  distilled  wader  to 
20  c.c.  ; that  is,  20  — 18-65  = 1-35  c.c.  of  water  must  be  added.  Measure 
the  total  quantity  of  acid  solution  there  is,  and  add  w"ater  to  it  in  the  above 
proportion.  Suppose  that  there  remain  1950  c.c.,  then  as  18-65  : 1950 


772 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


; : 1-35  to  the  quantity  of  water  that  must  be  added.  Add  the  proper 
amount  of  water  to  the  solution,  shake  up  thoroughly,  and  once  more 
test  by  filling  the  burette  and  titrating  against  20  c.c.  of  the  normal  sodium 
carbonate,  exactly  as  before  described  : 20  c.c.  of  the  one  solution  should 
exactly  neutralise  20  c.c.  of  the  other.  It  should  be  explained  that  the 
term  titrating  is  applied  to  the  operation  of  testing  a solution  by  adding  to  it 
a volumetric  reagent. 

836.  Normal  Sodium  Hydroxide. — ^The  next  step  is  to  prepare  a solu- 
tion of  normal  sodium  hydroxide  ; this  solution  contains  40  grams  of  pure 
NaHO  to  the  litre.  Weigh  out  about  120  grams  of  pure  caustic  soda  of 
commerce,  and  dissolve  up  in  a beaker  in  the  smallest  possible  quantity  of 
hot  water.  Allow  the  solution  to  stand  for  some  time,  in  order  that  any 
sediment  present  may  subside  ; cover  the  beaker  during  this  time  with  a 
glass  plate.  By  means  of  a pipette,  draw  off  as  much  as  possible  of  the 
clear  solution,  and  dilute  it  down  to  two  litres.  Run  in  this  solution  from 
a burette  into  20  c.c.  of  the  normal  sulphuric  acid  using  phenolphthalein 
as  an  indicator.  With  the  quantity  directed  the  solution  will  be  too  strong. 
Calculate  the  amount  of  water  that  must  be  added  to  bring  the  solution  to 
its  normal  strength,  and  proceed  exactly  as  was  directed  with  the  normal 
acid.  After  dilution,  again  titrate  acid  against  alkali,  when  20  c.c.  of  the 
one  must  exactly  neutralise  20  c.c.  of  the  other. 

837.  Decinormal  and  Centinormal  Solutions. — ^Having  succeeded  in 
preparing  with  accuracy  the  normal  sulphuric  acid  and  sodium  hydroxide, 
decinormal  solutions  of  these  reagents  must  be  made.  Measure  out  by 
means  of  a 100  c.c.  pipette,  200  c.c.  of  the  normal  acid,  and  pour  it  into  the 
litre  flask  ; fill  up  to  the  graduation  mark  with  distilled  water,  and  pour  into 
a clean  dry  “ Winchester  quart,’"  next  add  another  litre  of  distilled  water, 
and  two  litres  of  decinormal  acid  are  prepared.  In  the  same  manner  make 
up  two  litres  of  decinormal  soda.  Titrate  20  c.c.  of  one  of  these  against 
the  other  ; these,  too,  should  become  exactly  neutral  when  mixed  in  equal 
quantities. 

Centinormal  solutions  are  occasionally  required  for  certain  purposes  of 
analysis.  They  may  be  readily  prepared  by  taking  100  c.c.  of  decinormal 
solutions,  and  diluting  down  to  a litre  with  distilled  water  free  from  carbon 
dioxide. 

838.  Water  Free  from  Carbon  Dioxide. — In  addition  to  the  reagents 
already  described,  it  is  necessary  to  have,  for  determinations  of  acidity  in 
flours  or  meals,  some  distilled  water  free  from  carbon  dioxide.  This  is 
readily  obtained  by  first  rendering  some  water  alkaline  with  caustic  soda,  and 
then  distilling  ; the  first  portion  of  the  distillate  should  be  rejected.  The 
caustic  soda  combines  with  the  carbon  dioxide  that  may  be  dissolved  in 
the  water  ; and  so  by  this  treatment  the  gas  is  prevented  from  coming 
over  with  the  condensed  steam.  The  water  should  be  tested  in  order  to 
see  that  no  soda  has  been  carried  over  mecha.nica,lly  by  too  violent  boiling. 
The  water  must  give  no  colouration  on  the  cMdition  of  two  or  three  drops  of 
]:)henolplithalein  to  100  c.c.,  but  should  strike  a distinct  and  permanent  pink 
on  the  addition  of  a drop  of  N /lO  soda. 

For  many  purposes  it  is  sufficient  to  boil  ordinary  distilled  water  for 
some  ten  or  fifteen  minutes  before  use,  by  which  most  of  the  carbon  dioxide 
is  expelled. 

839.  Acidity  of  Meals  or  Flours. — ^When  it  is  desired  to  make  this 
estimation,  the  aqueous  infusion  should  be  made  with  the  water  free  from 
carbon  dioxide.  Pour  100  c.c.  of  aqueous  infusion  into  a white  porcelain 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


773 


disli,  add  two  or  three  drops  of  plienolphthalein  solution,  and  proceed  to 
titrate  with  N/10  soda.  The  burette  must  be  read  before  the  soda  is  run 
out,  and  then  again  at  the  completion  of  the  reaction.  After  the  addition 
of  each  drop  of  soda,  stir  the  liquid  thoroughly  ; the  reaction  is  complete 
when  the  slightest  pink  shade  remains  permanent  after  stirring.  It  need 
scarcely  be  said  that  the  dishes  and  other  apparatus  must  be  perfectly 
clean  ; the  burette  should  first  be  rinsed  with  clean  water,  and  then  with  a 
few  c.c.  of  the  soda  solution  ; this  should  be  allowed  to  run  away,  and  then 
the  instrument  should  be  filled.  Soda  solutions  tend  to  cause  glass  stop- 
cocks to  set  fast  ; the  burette  must  therefore  be  washed  after  use,  and 
before  being  put  away  the  stopcock  should  be  withdrawm  and  wrapped 
round  with  a small  piece  of  paper,  and  again  put  in  its  place  ; this  prevents 
its  sticking  It  must  of  course  be  seen  that  it  is  not  so  placed  as  to  drop 
out  by  an  accident  and  get  broken.  For  soda  solutions  it  is  preferable, 
however,  to  use  a burette  with  an  india-rubber  tube  and  spring  clip.  Assum- 
ing that  the  acidity  of  meal  or  flour  is  due  to  lactic  acid  (as  undoubtedly 
it  is  in  whole  or  great  part),  then  as  1 c.c.  of  Y/IO  NalTO  is  neutralised  by 
0-009  gram  of  lactic  acid,  the  No.  of  c.c.  used  X 0-009  gives  the  weight  of 
lactic  acid  in  100  c.c.  of  the  infusion.  This  quantity  of  infusion  contains 
the  acid  of  10  grams  of  the  meal  or  flour,  therefore  No.  of  c.c.  of  Y/IO  soda 
X 0-009  X 10  = percentage  of  acid  in  the  sample — in  other  words,  vith 
the  quantities  directed  the  percentage  equals  0-09  times  the  No.  of  c.c.  of 
Y/IO  soda  used. 

Balland,  who  has  devoted  much  attention  to  the  acidity  of  flours,  finds 
that,  on  exhausting  a good  flour  with  alcohol  and  titrating  the  solution  with 
turmeric  paper  as  an  indicator,  the  normal  acidity  represented  as  sulphuric 
acid  varies  between  0-015  and  0-040  per  cent.  But  Avorking  with  the  whole 
flour  a higher  percentage  of  acidity  is  obtained.  Planchon  took  5 grams 
of  the  flour  and  gradually  mixed  same  with  50  c.c.  of  cold  distilled  w^ater, 
and  added,  wiien  perfectly  homogeneous,  tw^o  or  three  drops  of  alcoholic 
plienolphthalein  solution  and  titrated  w ith  N /20  solution  of  sodium  hydrate. 
He  used  0-0245  as  a factor,  and  multiplying  the  number  of  c.c.  of  soda  by 
that  figure,  got  wiiat  w^as  in  his  opinion  the  actual  acidity  of  the  flour. 
He  finds  that  this  does  not  increase  during  the  time  necessary  for  the  esti- 
mation ; but  on  the  contrary,  that  no  variation  occurs  during  the  first 
tw^o  hours.  Taking  the  same  flour,  and  maintaining  it  in  contact  with 
Avater  for  varying  times,  he  got  the  results  A\4iich  are  appended.  A corre- 
sponding series  of  tests  AA'as  made  AAuth  the  filtered  aqueous  extract  of  such 
flours  : the  results  obtained  are  given  in  the  folloAA’ing  table  as  soluble 
acidity. 


Titrated 

immediately 

Percentage  of  acidity  reckoned  as  H2SO4. 
Total.  Soluble. 

. . 0-110  0-0107 

? ? 

after  I hour 

. . 0-110 

0-0225 

? ? 

,,  2 hours  . . 

. . 0-110 

0-0230 

? > 

„ 4 „ .. 

. . 0-113 

0-0250 

?? 

„ 7 „ .. 

..  0-115 

0-0275 

5 ? 

„ 24  „ .. 

. . 0-126 

0-0425 

„ 48  „ .. 

. . 0-145 

0-0830 

The  same  flour,  Aifiien  extracted  AAuth  alcohol  (rectified  spirit)  for  24 
four  hours,  shoAA'cd  after  filtration  the  presence  of  0-03  per  cent,  of  acidity 
soluble  therein.  Flour  does  not  give  up  the  Avhole  of  its  acidity  immediately 
to  either  Avater  or  alcohol.  Planchon,  therefore,  recommends  instead  the 
titration  of  the  Avhole  flour  in  the  presence  of  Avater,  and  gives  the  folloAAing 
as  the  results  of  such  tests,  still  reckoning  total  acidity  as  sulphuric  acid  : — 


774 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Nine  Roller  Milled  samples  of  fresh  flour 
Stone  Milled  sample  of  fresh  flour 
Second  sample  of  do. 

Damaged  flour  unfit  for  use 
Second  sample  of  do. 


Acidity  per  cent. 

from  0-105  to  0-122 
..  0-119 

. . 0-133 

. . 0-160 

. . 0-565 


The  authors  may  state  that  they  have  for  some  time  independently 
adopted  the  method  of  titration  of  the  whole  substance  for  both  flour 
and  bread  testing,  and  confirm  the  conclusions  arrived  at  by  Planchon. 

The  mode  of  titration  of  the  mixed  flour  and  water  is  performed  in  just 
the  same  way  as  with  the  filtered  aqueous  extract. 


840.  Analysis  of  Old  Flours. — ^Balland  and  Planchon  state  that  old 
flour  which  has  reached  |its  extreme  limit  of  possible  preservation,  and 
thereby  lost  its  commercial  value,  is  being  rejuvenated  by  passing  through 
the  mill  with  a proportion  of  fresh  flour.  Such  mixed  flour  escapes  detec- 
tion by  trade  experts,  and  passes  as  genuine  new  flour.  Very  shortly,  how- 
ever, the  newness  passes  ofl,  and  the  whole  flour  becomes  stale.  On  exam- 
ination such  flours  are  found  to  have  both  ash  and  water  normal,  but  the 
fat  will  have  decreased  and  the  acidity  increased.  The  gluten  also  shows 
signs  of  change,  being  less  coherent,  and  having  a tendency  to  produce 
frothiness  in  the  water  employed  for  washing  it.  This  latter  characteristic 
is  specially  noticeable  in  the  case  of  the  gluten  being  allowed  to  remain 
under  water  for  24  hours  after  being  extracted.  Fresh  washing  at  the  end 
of  this  period  causes,  in  addition  to  frothing,  much  loss  of  weight.  The 
following  figures  give  the  results  of  examination  of  three  such  samples  of 
mixed  flour  compared  with  genuine  new  flours  : — 


Sample  No.  1 

Original 
Gluten. 
Per  cent. 

. . 29-6 

Gluten  re-washed 
after  24  hours 
in  water. 

Per  cent. 
18-0 

„ 2 

. . 36-4 

27-2 

55  55  ^ 

. . 36-0 

26-4 

New  Flour  A 

. . 38-8 

34-8 

5 5 5 5 B 

. . 36-0  ■ 

32-4 

55  ,5  C 

. . 36-0 

31-2 

841.  Separation  and  Identification  of  Acids  of  Sour  Bread. — ^The  acids 
occurring  in  either  sour  bread  or  dough  may  be  divided  into  the  two  groups 
of  fixed  and  volatile  acids.  The  former  consist  almost  entirely  of  lactic 
acid,  while  the  latter  may  contain  acetic  or  butyric  acids.  An  approximate 
determination  of  the  fixed  and  volatile  acids  may  be  made  in  the  following 
manner  : — Take  100  c.c.  of  the  solution  as  directed  to  be  prepared  for 
determination  of  acidity,  and  evaporate  to  dryness  in  a platinum  basin 
over  a water  bath,  dilute  again  wdth  pure  distilled  water,  and  repeat  the 
process  of  evaporation.  Titrate  the  residue  vdth  decinormal  or  centinormal 
acid,  and  calculate  the  acidity  as  lactic  acid.  Subtract  the  number  of  c.c. 
used  for  the  titration  from  the  total  quantity  required  for  the  100  c.c.  of  the 
soluble  extract  ; the  difference  is  the  amount  of  volatile  acidity,  and  may 
be  calculated  as  acetic  acid.  It  is  important  to  make  this  determination 
in  a platinum  vessel,  as  glass  imparts  sufficient  alkalinity  to  the  liquid  to 
partly,  if  not  entirely,  vitiate  the  results.  Another  objection  is  that  an 
aqueous  extract  of  either  flour  or  bread,  as  shown  by  Balland,  does  not 
give  up  the  whole  of  its  acidity  to  its  filtered  aqueous  extract.  It  is  difficult 
on  the  other  hand  to  work  on  the  whole  flour,  because  on  boiling  vdth  water 
the  starch  would  gelatinise,  and  thus  produce  an  unworkable  mass. 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  775 

The  same  method  may  be  employed  on  bread,  in  whicli  case  take  10 
grams  of  bread,  and  measure  out  100  c.c.  of  water  ; rub  the  bread  into  a 
paste  in  a mortar,  witli  a little  of  the  water,  and  finally  add  the  whole. 
Transfer  to  a flask,  and  add  I c.c.  of  chloroform  (having  a neutral  reaction 
to  phenolphthalein),  shake  up  vigorously,  and  allow  to  stand  over  night. 
In  the  morning,  decant  off  the  clear  supernatant  liquid,  and  filter.  Take 
a measured  quantity  of  the  filtrate,  and  evaporate  as  before  in  a platinum 
basin  ; calculating  volatile  and  fixed  acids  respectively  as  acetic  and  lactic 
acid. 

A more  accurate  method  of  determining  the  volatile  acids  in  bread  is 
based  on  distillation  in  vacuo.  For  this  purpose  the  following  apparatus 
may  be  employed.  Select  a good  round-bottom  Bohemian  flask  of  about 
1 litre  capacity,  a,  Fig.  115,  fit  to  it  a sound  cork,  through  which  three  holes 
have  been  bored.  Through  one  pass  a tube,  b,  leading  to  the  bottom  of 
the  flask,  through  another,  the  thermometer,  c,  registering  to  200°  C.,  and 
through  the  third,  the  leading  tube,  d.  The  thermometer  must  be  so 
arranged  that  its  bulb  shall  be  about  the  middle  of  the  flask.  By 'means 
of  a cork  connect  up  d to  the  Liebig’s  condenser,  e,  and  attach  the  lower 


end  of  the  condenser  by  means  of  tubing  and  corks  to  the  bulbs,  m n,  the 
capacity  of  which  should  be  about  250  c.c.  Connect  up  the  further  bulb,  m, 
by  corks  and  tubing,  o p,  to  a powerful  water  or  mercury  vacuum  pump, 
preferably  the  former.  Arrange  the  whole  apparatus  so  that  the  flask,  a, 
is  fixed  by  means  of  a retort  stand  and  clamp  in  the  bath,  q,  which  in  its 
turn  is  carried  on  a small  heating  burner.  Close  the  open  end  of  the  tube, 
b,  by  means  of  a piece  of  india-rubber  tubing  and  pinch  cock,  and  set  the 
vacuum  pump  in  motion.  Wait  until  a vacuum  is  obtained  ; stop  the 
pump,  and  watch  the  vacuum  gauge  to  see  whether  the  apparatus  is 
air-tight.  A vertical  spiral  worm  condenser  may  with  advantage  be  sub- 
stituted for  the  Liebig’s  condenser,  e. 

Cut  the  bread  to  be  tested  into  small  dice,  not  more  than  three-eighths 
of  an  inch  square  ; weigh  off  250  grams,  and  transfer  to  the  flask,  a,  and 
replace  the  cork,  taking  care  that  the  end  of  the  tube,  b,  does  not  get  choked. 
Close  b with  the  pinch  cock,  pour  sufficient  distilled  water  into  m ^ to  seal 
the  connecting  tube  at  the  bottom,  and  connect  up  the  whole  apparatus. 


776 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Fill  the  bath,  q,  with  glycerin  to  very  nearly  the  top,  and  arrange  a ther- 
mometer, r,  to  take  the  temperature  of  the  bath.  Set  the  vacuum  pump 
going,  and  turn  the  water  on  to  the  condenser.  Then  light  the  burner,  and 
raise  the  temperature  of  the  glycerin  bath  to  150-160°  C.,  and  maintain  it 
at  that  point.  The  moisture  of  the  bread  is  volatilised,  condensed  in  passing 
through  the  condenser,  and  collected  in  the  bulbs,  m n.  The  escape  of 
glycerin  vapour  from  the  bath  may  be  largely  prevented  by  covering  over 
the  top  with  pieces  of  cardboard.  When  the  distillation  slackens,  turn  olf 
the  pump  ; admit  air  slowly  through  the  tube,  h,  until  the  whole  apparatus 
is  filled,  and  then  again  exhaust.  “ Wash  the  flask  out  with  air  in  this 
way  repeatedly.  At  the  expiration  of  about  40  minutes,  stop  the  pump, 
admit  air  through  h,  and  disconnect  the  flask,  a,  from  the  condenser.  Re- 
move from  the  bath,  and  shake  up,  so  as  to  thoroughly  mix  the  bread. 
Again,  connect  up  the  apparatus,  and  recommence  the  process  of  distilla- 
tion ; at  intervals  of  about  half  an  hour,  repeat  the  operation  of  discon- 
necting the  flask  and  shaking  up  the  contents,  doing  this  altogether  three 
times.  In  about  two  hours  from  the  commencement,  the  whole  of  the 
moisture  will  have  come  over,  and  the  thermometer  inside  the  flask  will 
register  about  125°  C.  Weigh  the  residual  dry  bread,  and  thus  determine 
the  percentage  of  moisture  lost  : measure  also  the  total  volume  of  distil- 
late. Determine  acidity  in  the  original  bread,  dry  residue,  and  distillate, 
using  for  the  two  former,  tests  on  the  whole  substance  without  filtration. 
As  before,  the  volatile  acidity  may  be  calculated  as  acetic,  and  the  fixed  as 
lactic  acid. 

842.  Duclaux’s  Method  of  Estimating  Volatile  Acids. — ^Duclaux  finds 
that  of  the  volatile  acids  of  the  acetic  series,  each  has  its  own  definite  rate 
of  distillation  under  certain  fixed  conditions.  Thus,  if  110  c.c.  of  a mixture 
of  acetic  acid  and  water  be  taken  and  distilled  in  a 300  c.c.  flask  or  retort 
until  I f or  100  c.c.  have  distilled  over,  it  will  be  found  that  the  quantity  of 
acid  in  the  distillate  is  very  nearly  80  per  cent,  of  the  whole,  independently 
of  the  strength  of  the  original  solution  of  acid.  Further,  if  the  distillate 
be  collected  in  successive  fractions  of  10  c.c.,  and  each  titrated  separately, 
the  proportion  of  acid  passing  over  in  these  equal  volumes  will  in  all  cases 
be  the  same  for  each  successive  volume  provided  the  acid  is  pure,  but  will 
vary  appreciably  in  the  presence  of  even  traces  of  the  other  fatty  acids. 
Foreign  matters  other  than  acids  do  not  seem  to  have  any  very  great  influence 
on  the  course  of  the  distillation.  The  table  on  page  777  gives  the  percentage 
of  acid  which  distils  over  in  each  successive  10  c.c.  for  acetic  and  butyric 
acid  respectively.  The  columns  A show  the  percentage  of  the  total  acid  in 
the  distillate  which  passes  over  with  each  fraction  : while  in  columns  B 
the  percentages  of  the  total  acid  in  the  whole  liquid  operated  on  are  given. 

Taking  acetic  acid  solution  of  whatever  strength,  5-9  per  cent,  of  the 
whole  of  the  acid  will  come  over  in  the  first  10  c.c.,  6-2  per  cent,  in  the 
second,  and  so  on.  The  quantity  of  acid,  which  comes  over,  gradually 
increases  until  in  the  tenth  10  c.c.  12-1  per  cent,  is  found,  making  altogether 
79-8  of  the  total  acid,  and  leaving  20-2  per  cent,  in  the  remaining  10  c.c. 
in  tlie  flask.  With  butyric  acid,  on  the  other  hand,  although  the  boiling 
point  is  higher,  the  acid  comes  over  more  rapidly  in  the  earlier  part  of  the 
distillation.  Tims,  the  first  10  c.c.  contain  16-4  per  cent,  of  the  whole  of 
tlie  acid,  the  last  10  c.c.  3-5  per  cent,  of  the  whole,  while  only  2-5  per  cent, 
remain  behind  in  the  10  c.c.  contained  in  the  flask.  When  a mixture  of 
acids  is  distilled,  each  maintains  its  own  rate  of  distillation  independently 
of  tlie  otliers.  It  is  thus  possible,  by  fractionally  distilling  a solution  of 
volatile  acid,  not  only  to  identify  the  acid,  but  also  to  estimate  the  propor- 
tion of  each  which  is  present  in  a mixture.  To  do  this  exactly  a somewhat 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  777 


Fractional  Distillation  of  Acids — Luclaux. 


Acetic. 

Butyric. 

A. 

Per  cent. 

B. 

Per  cent. 

A. 

Per  cent. 

B. 

Per  cent. 

1st.  fraction  of  10  c.c.  . . 

7-5 

5-9 

16-8 

16-4 

2nd,  ,, 

7-9 

6-2  , 

15-1 

14-7 

3rd.  ,, 

8-2 

6-7 

13-5 

13-2 

4th.  ,,  ,, 

8-6 

6-9 

12-3 

11-8 

5th.  ,, 

9-1 

7-3 

10-2 

10-1 

6th. 

9-6 

7.6 

9-3 

9-1 

7th.  „ 

10-2 

8-2 

7-8 

7-6 

8th. 

11*5 

9-2 

j 64 

6-3 

9th. 

124 

9-8 

1 5-0 

4-8 

10th.  ,,  ,, 

15-1 

12-1 

' 3-6 

3-5 

Total  distillate  = 100  c.c. 

100-0 

79-8 

! 100-0 

97-5 

Remaining  in  retort  = 10  c.c. 

20-2 

2-5 

complicated  calculation  is  necessary,  but  when  only  the  two  acids,  acetic 
and  butyric,  are  present,  the  accompanying  table,  page  778,  of  rates  of 
distillation  of  mixtures  of  the  two  in  certain  definite  proportions,  will  serve 
as  a guide  in  approximately  estimating  the  quantity  of  each  which  is  present. 

The  accurate  estimation  of  volatile  acids  in  dough  and  bread  is  fraught 
with  special  difficulties,  some  of  which  have  been  already  recounted.  It  is 
impossible  to  proceed  by  working  down  the  dough  into  a thin  “ cream 
with  water,  and  subjecting  that  to  distillation,  because  the  starch  would 
gelatinise  and  the  resultant  paste  would  boil  over  into  the  condenser.  An 
aqueous  extract  may  be  made  with  chloroform  water,  but,  as  shown  by  Bal- 
land,  a large  proportion  of  the  acid  does  not  yield  itself  to  the  filtered  ex- 
tract. (Out  of  0T26  per  cent.  Balland  found  only  0-042  per  cent.,  or 
exactly  J,  in  a filtered  solution  after  water  and  flour  had  stood  together 
for  24  hours.)  Further,  when  working  with  this  solution,  a portion  of  the 
lactic  acid  it  contains  distils  over.  Bread  presents  less  difficulties  than 
dough,  because  it  can  be  more  readily  submitted  to  distillation  in  vacuo. 
The  best  method  of  estimating  will  be  to  obtain  the  distillate  of  two  lots 
of  250  grams  each  of  bread,  and  work  on  that,  which  will  give  altogether 
about  200  c.c.  of  distillate.  Experiment  shows  that  by  this  process  none 
of  the  volatile  acias  is  lost  ; for  on  adding  a second  pair  of  bulbs  between 
m n and  the  pump  in  Fig.  1 15,  and  placing  20  c.c.  of  centinormal  soda  in 
these,  it  was  found  by  titration  at  the  close  of  the  experiment  that  none 
of  the  soda  had  been  neutralised  by  acid  passing  over  from  m n.  On  the 
other  hand,  the  distillate  obtained  in  this  manner  apparently  contains 
traces  of  lactic  acid.  In  a special  experiment  500  c.c.  of  distillate  were 
taken,  a little  zinc  oxide  added,  and  evaporated  down.  The  concentrated 
solution  was  filtered  from  excess  of  the  oxide,  and  evaporation  continued 
until  about  1 c.c.  only  remained — on  cooling  crystals  of  zinc  lactate  separated 
out.  These  erystals  were  specially  tested  for  acetic  acid,  and  gave  no 
reaction. 

Measure  first  the  total  quantity  of  distillate,  and  determine  its  acidity 
in  10  or  20  c.c.  Then  prior  to  starting  on  the  estimation  the  following 
reagents  are  necessary  ; — Prepare  distilled  water  free  from  carbon  dioxide 
and  neutral  to  phenolphthalein,  and  with  this  make  up  some  centinormal 


Distillation  of  Mixtures  of  Acetic  {a)  and  Butyric  Acid  (&)— Duclaux. 


778 


THE  TECHNOLOGY  OF  BREAD-MAKING 


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No.  11  is  the  10  c.c.  remaitiingjn  the  retort  after  the  distillation. 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  779 

sulphuric  acid  and  soda.  Titrate  these  against  each  other — they  must 
exactly  agree.  Test  a clean  glass  Wurtz  flask  for  alkalinity  by  boiling  110 
c.c.  of  pure  distilled  water  down  to  10  c.c.  in  it,  and  titrating  the  residue — 
this  should  still  be  neutral  to  phenolphthalein.  If  the  flask  gives  an  alka- 
line reaction,  it  must  be  discarded.  The  authors  find  flasks  of  “Jena  ” 
toughened  glass  very  free  from  alkalinity,  and  so  specially  adapted  for  this 
work. 

Working  with  such  dilute  solutions,  the  loss  through  imperfect  conden- 
sation is  sufficient  to  materially  affect  results,  particularly  when  the  rate 
of  distillation  is  irregular  through  bumping.  The  following  arrangement 
of  apparatus.  Fig.  116,  is  recommended  for  the  distillation:  a is  the  side- 
tube  (Wurtz)  flask  of  300  c.c.  capacity,  attached  to  the  condenser,  h.  (For 
this  a spiral  condenser 
may  be  substituted  witli 
advantage. ) Pro  cure 
some  colourless  glass 
tubes,  c,  about  3 inches 
high  and  1 inch  diameter, 
and  graduated  with  a 10 
c.c.  mark,  as  shown.  Fit 
up  three  of  these  with 
corks  and  leading  tubes, 
cl,  and  bulbs,  e f (like 
small  nitrogen  bulbs).  To 
commence  the  experi- 
ment, place  5 c.c.  of  cen- 
tinormal  soda  in  the 
bulbs,  e /,  and  connect  up 
the  apparatus.  Turn  on 
the  water  through  the 
condenser,  and  start  the 
distillation.  Meantime 
get  another  tube,  c,  with 
its  bulbs  charged  with  soda  in  readiness.  Watch  till  10  c.c.  have  come  over, 
and  replace  the  filled  c tube  with  the  empty  one.  Transfer  the  contents 
of  both  tube  and  bulbs  to  a beaker,  rinsing  out  with  a little  pure  distilled 
water,  and  immediately  titrate  with  centinormal  soda  or  acid,  according 
to  whether  the  solution  be  acid  or  alkaline.  If  acid,  5 c.c.  -f  quantity 
taken  for  titration  = the  acidity.  If  alkaline,  5 c.c.  — quantity  for  titra- 
tion = acidity  of  the  distillate.  Remove  the  second  distillate,  and  replace 
by  another  receiver,  c,  and  charged  bulbs.  Titrate  each  in  precisely  the 
same  manner,  and  continue  until  the  ten  distillates  have  been  collected. 
Finally,  titrate  the  10  c.c.  which  remain  in  the  flask.  The  arrangement  of 
receivers  fitted  with  charged  bulbs  appears  complicated  ; but  a number  of 
experiments  have  shown  that  with  open  condensation  there  is  a very  con- 
siderable loss  of  acid.  Having  obtained  by  titration  the  amount  of  acid 
reckoned  as  centinormal  in  each  fraction,  calculate  out  what  percentage 
of  the  whole  acid  in  the  110  c.c.  it  represents  in  each  case  : in  fact,  work  out 
column  B as  per  table  for  the  particular  experiment.  In  order  to  explain 
this  calculation,  let  us  assume  the  following  to  be  the  results  of  an  analysis' : — 

Bread  taken  . . . . . . 500  grams. 

Weight  of  Dried  Bread  . . 324  ,,  = 64*8  per  cent. 

Volume  of  distillate  . . . . 180  c.c. 

Acidity  of  10  c.c.  — 12T  c.c.  A/lOO  acid  = 217-8  on  total  distillate. 

Took  for  fractional  distillation,  ! 10  c.c.  = 133-1  acidity. 


Fig.  116. — Appakatus  for  Duclaux  Distillations. 


780 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


1st.  fraction 
2nd.  „ 

3rd.  ., 

4th.  „ 

5th.  „ 

6th. 

7th.  ,, 

8th.  „ 

9th.  „ 

10th.  ,, 

11th.  residuum 


Acidity 


Observed 
Acidity  in 
c.c.  N /lOO  acid. 

9-4 

calculated  in 
percentages  of 
total  in  110  c.c. 

7-0 

9-6 

7-2 

9-7 

7-2 

9-8 

74 

10-0 

- 7-5 

10-5 

7-8 

10-9 

8-2 

11-6 

8-8 

12-7 

9-5 

14-8 

11-1 

24-1 

18-1 

The  figures  in  the  second  column  are  simply  calculated  in  percentages 
9-4  X 100  ^ , 

1331  = ' 


Turning  next  to  the  table  (page  778)  of  distillation  of  mixtures  of  acetic 
and  butyric  acids,  we  find  that  these  figures  closely  agree  with  those  yielded 
by  ten  parts  of  acetie  to  one  of  butyrie  acid  : consequently  the  assump- 
tion is  that  the  volatile  acids  exist  in  these  proportions  to  each  other.  Of 

917, Q y 1(1 

the  total  acidity,  therefore = 198  c.c.  N/lOO  aeid  are  due  to 


acetic  acid,  and 


217-8 

11 


= 19-8  c.c.  A/100  acid  to  butyric  acid. 


The  factors 


for  A/100  acetic  and  butyric  acids  respectively  are  0-0006  and  0-00088  ; 
and  as  500  grams  of  bread  were  taken,  Ave  have  198  x 0-0006  x 0-2  = 
0-023  per  cent,  of  acetic  acid,  and  19-8  x 0-00088  x 0-2  = 0-003  per  cent, 
of  butyrie  acid. 

This  example,  Avith  hypothetical  quantities,  is  simply  given  as  an  illus- 
tration of  the  mode  of  ealeulation. 


843.  Estimation  of  Proteins. — ^For  technieal  purposes,- proteins  are  noAv 
determined  by  AAliat  is  knoAAm,  after  the  name  of  the  inventor,  as  Kjeldalihs 
process,  (or  some  modification  thereof).  This  method  depends  on  the  fact 
that,  Avhen  an  organic  substance  is  heated  AA'ith  a mixture  of  concen- 
trated sulphurie  acid  and  potassium  sulphate,  its  nitrogen,  if  any,  is  (Avith 
A^ery  feAV  exeeptions)  converted  into  ammonia,  and  retained  by  the  aeid 
as  ammonium  sulphate.  The  residuum  is  subsequently  rendered  alkaline 
by  excess  of  soda,  and  distilled.  The  ammonia  comes  over  and  is  collected 
in  a knoAAm  volume  of  deeinormal  aeid,  Avliich  is  titrated,  and  then  the 
amount  of  ammonia  'determined.  From  this  the  percentage  of  protein 
matter  is  readily  calculated.  A detailed  description  folio aa^s  of  the  mode 
of  performing  an  organie  nitrogen  estimation  by  Kjeldahl’s  method. 

Reagents  and  solutions  required. — Pure  eoncentrated  sulphurie  acid,  as 
free  as  possible  from  nitrogen  compounds. 

Concentrated  solution  of  caustic  soda.  Take  3 lbs.  of  commereial  sodium 
liydroxide,  either  in  poAA^der  or  sticks,  and  dissolve  in  as  small  a quantity 
of  Avater  as  possible  ; let  the  solution  eool,  and  make  up  to  suffieient  to  fill 
a Wineliester  quart  (about  tAVO  Imperial  quarts).  Store  in  a Winchester 
fitted  Avith  india-rubber  stopper. 

PoAvdered  potassium  sulphate.  Heat  this  for  some  time  in  an  iron 
A^essel,  and  store  in  a stoppered  bottle. 

Deeinormal  sulphuric  acid  and  sodium  hydroxide. 

Methyl  orange  solution. 

Apparatus. — Speeial  long-neeked  heating  flasks  of  Jena  toughened  glass, 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


781 


of  300  or  500  c.c.  capacity.  Wrought-iron  stand  to  hold  four  of  tliese  flasks 
for  heating  purposes.  This  stand  should  consist  of  a stout  sheet  iron  plate, 
15  inches  long  by  4 J inches  wide,  supported  on  four  legs  for  ordinary  bunsen 
burners,  and  with  four  holes,  each  2 inches  diameter,  through  the  plate.  On 
the  one  long  edge  of  the  plate  an  upright  back  should  be  fixed  about  4 
inches  high,  and  with  round  notches  cut  out  so  that  when  the  flasks  are 
resting  in  the  holes  in  the  plate,  the  necks  may  lie  in  the  notches  in  the  back. 
The  flasks  are  thus  supported  when  in  use  in  an  oblique  position. 

Distilling  Apparatus. — If  500  c.c.  flasks  are  used,  these  may  be  employed 
direct  for  the  distillation.  If  not,  a 500  c.c.  flask  of  the  same  kind  should 
be  used  for  this  operation.  To  this  flask,  a,  in  Fig.  117,  fit  a rubber  cork 
and  splash-head,  b.  This  latter  is  attached  in  turn  to  a condenser,  c,  fitted 
with  a condensing  tube  of  pure  tin.  The  lower  end  of  the  condenser,  d,  is 
passed  through  a rubber  cork,  and  thus  fixed  to  the  Kjeldahl  bulbs,  e /. 


Mode  of  Analysis. — To  estimate  total  proteins  on  flours  or  meals,  weigh 
off  1 gram  of  the  sample  and  transfer  it  to  a clean,  dry,  heating  flask.  The 
weighing  is  best  done  with  a pair  of  counterpoised  horn  dishes  for  the  bal- 
ance. Obtain  a wide- mouthed  glass  funnel  that  will  just  fit  the  flask,  and 
pour  into  it  the  flour  or  meal,  carefully  brushing  every  particle  in  by  means 
of  a brush  kept  for  the  purpose.  Or  if  preferred,  make  a V-shaped  gutter 
out  of  glazed  paper  that  will  pass  right  into  the  neck  of  the  flask  and  down 


782 


THE  TECHNOLOGY  OF  BREAH-MAKING. 


into  the  bulb,  and  introduce  the  substance  by  means  of  this.  In  any  case 
all  particles  must  be  brushed  right  down  into  the  flask.  By  means  of  a 
pipette  add  20  c.c.  of  the  concentrated  sulphuric  acid  and  about  10  grams 
of  the  potassium  sulphate.  This  latter  may  be  conveniently  measured, 
using  for  that  purpose  the  end  of  a test  tube,  or  what  answers  very  well, 
a sewing  thimble  of  the  right  size.  (This  may  be  obtained  once  for  all  by 
weighing  out  the  quantity.)  Rinse  the  acid  gently  round  inside  the  flask 
so  as  to  thoroughly  wet  it,  taking  care  that  there  are  no  dry  patches  of  flour 
between  the  acid  and  the  flask.  Occasionally  one  gets  a small  patch  which 
obstinately  refuses  to  mix  with  the  acid,  which  must  then  be  provided  for 
in  the  heating.  Arrange  the  flask  stand  in  a stink  cupboard  designed  so  as 
to  carry  ofl  the  fumes  produced,  and  stand  the  flask  obliquely  in  one  of  the 
holes,  with  its  neck  lying  in  the  notch.  Should  there  be  any  adherent  dry 
patches  of  flour,  turn  the  flask  so  that  they  are  out  of  the  liquid  and  on  the 
upper  side  of  the  flask.  Turn  on  a very  small  bunsen  flame  ; as  the  acid 
gets  hot  it  carbonises  the  flour,  which  froths  up  and  gradually  subsides  into 
a tarry  looking  liquid.  The  steam  of  the  boiling  acid  attacks  any  flour 
patches  on  the  upper  part  of  the  flask,  and  speedily  brings  them  down  into 
the  solution.  Continue  to  apply  heat  so  that  the  acid  is  just  below  the 
point  of  ebullition,  a bubble  of  steam  escaping  only  occasionally  : the 
black  liquid  gradually  loses  its  colour,  and  in  about  45  minutes  has  usually 
become  colourless.  As  soon  as  this  stage  is  reached  it  is  allowed  to  cool. 

When  perfectly  cold  the  next  step  is  to  arrange  for  the  distillation  ; this, 
however,  must  be  preceded  by  a blank  experiment,  made  in  order  to  deter- 
mine the  amount  of  ammonia  present  as  impurity  in  the  reagents  used. 
Add  20  c.c.  of  the  concentrated  sulphuric  acid  to  the  contents  of  the  10 
gram  measure  of  potassium  sulphate  in  a round-bottomed  flask  precisely 
as  before  : heat  so  as  to  melt  the  sulphate,  and  allow  to  cool.  Measure 
off  200  c.c.  of  water  in  a graduated  jar,  and  pour  it  into  the  flask  containing 
the  acid  and  sulphate — the  liquid  becomes  very  hot,  but  does  not  spurt  if 
sufficient  water  is  added.  Next  add  a drop  of  methyl  orange,  and  give  the 
flask  a shake  round  so  as  to  mix  the  contents.  Then  by  means  of  a funnel 
pour  some  of  the  strong  soda  solution  from  a 100  c.c.  graduated  measure 
into  the  flask  until  the  acid  is  neutralised,  and  add  an  extra  5 c.c.  Make  a 
note  on  the  label  of  the  bottle  of  the  total  quantity  thus  used.  (The  object 
of  adding  methyl  orange  is  to  determine  once  for  all  how  much  soda  is  neces- 
sary ; this  quantity  is  then  used  in  the  estimations  until  a fresh  quantity 
is  made  up,  when  it  should  be  again  titrated.)  Introduce  a few  fragments 
of  coarsely  granulated  zinc  in  order  to  prevent  bumping,  and  cork  up  the 
flask  to  the  splash-head,  h.  By  means  of  a pipette,  introduce  25  c.c.  of 
decinormal  sulphuric  acid  into  the  bulbs,  e /,  and  connect  to  the  condenser. 
Turn  a current  of  cold  water  through  the  condenser,  and  light  a bunsen 
underneath  the  flask  ; its  contents  speedily  come  to  the  boil,  and  the  steam 
and  ammonia  together  are  condensed,  and  retained  in  the  Kjeldahl  bulbs, 
m n.  Continue  the  distillation  until  about  200  c.c.  have  come  over  ; turn 
out  the  lights,  disconnect  the  bulbs,  and  pour  their  contents  into  an  evaporat- 
ing basin,  and  titrate  with  decinormal  soda  and  methyl  orange.  In  the 
blank  experiment,  the  quantity  of  ammonia  eyolved  amounts  usually  from 
0-3  to  0-5  c.c.  of  decinormal  ammonia  : make  a note  of  this  quantity,  and 
repeat  the  blank  with  each  new  lot  of  concentrated  acid  and  soda.  So 
far  as  possible  make  these  up  each  time  in  about  equivalent  quantities. 

Returning  to  the  clear  solution  obtained  by  treatment  of  the  flour  or 
meal  witli  acid  and  sulphate  as  previously  described,  if  a 500  c.c.  flask  has 
been  used,  add  water  to  it  in  the  same  way  as  to  the  blank,  and  then  the 
quantity  of  strong  soda  solution  as  ascertained,  then  the  granulated  zinc 
and  distil  as  before.  If  the  burning  down  with  acid  and  sulphate  has  been 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


783 


carried  out  in  a 300  c.c.  flask,  the  eold  eontents  must  first  have  150  e.c.  of 
water  added  to  them,  and  then  be  transferred  to  a 500  c.c.  flask.  Witli  the 
remaining  50  c.c.  of  water  give  the  300  c.c.  flask  several  rinsings,  whieh 
must  be  added  to  the  main  portion  in  the  larger  flask,  after  which  the 
requisite  quantity  of  soda  is  poured  in.  As  soon  as  the  soda  is  added,  the 
ammonia  is  set  free  and  therefore  no  time  should  be  lost  in  corking  the  flask 
to  the  splash-head  in  order  to  prevent  any  escape.  At  the  close  of  the 
experiment  thoroughly  wash  out  the  distillation  flask,  and  place  it  bottom 
upwards  in  a rack  so  as  to  drain.  Preserve  the  washed  zinc  in  a small  bottle 
or  flask  of  water  for  use  in  the  next  test. 

Calculation. — As  25  c.c.  of  acid  are  taken  for  the  determination  in  the 
bulbs,  that  quantity,  less  the  amount  required  for  its  titration,  represents 
the  amount  of  decinormal  ammonia  evolved,  thus  : — 

25  c.c.  - 13-3  c.c.  A/10  soda  = 11-7  c.c.  A/10  NH3. 

(According  to  blank  experiment,  the  correction  is  0*4  c.c.) 
then  11-7  — 0-4  = 11-3  c.c.  from  nitrogen  of  flour. 

As  1 c.c.  of  A/10  NH3  equals  0’0014  of  nitrogen  as  ammonia,  then  11*3 
X 0-0014  = 0-01582  of  nitrogen. 

Osborne  and  Voorhees  And  that  gliadin  contains  17-66  per  cent,  of 
nitrogen,  and  glutenin  17-49  per  cent.  As  these  two  proteins  constitute 
the  main  portion  of  the  proteins  of  flour,  they  assume  wheat  proteins  to 

contain  17-60  per  cent,  of  nitrogen.  As  5-68,  they  multiply  the 

quantity  of  nitrogen  found  by  5-68,  as  a constant  factor  in  order  to  convert 
the  percentage  of  nitrogen  into  that  of  proteins.  Proteins  as  commonly  separ- 
ated eontain  a quantity  of  water  of  hydration  which  is  not  driven  off  at 
100°  C.,  and  therefore  multiplication  by  5-68  does  not  give  the  quantity  of 
hydrated  proteins.  The  flgure  formerly  employed  for  calculation  of  nitrogen 
into  hydrated  proteins  was  6-33,  but  this  is  now  regarded  as  being  more 

eorrectly  expressed  by  6-25.  As  this  last  factor,  6-25,  has  been  very  ex- 

tensively employed,  it  is  still  most  commonly  used  so  as  to  make  results 
comparable  with  those  already  on  record.  In  returning  analytic  results, 
the  actual  quantity  of  nitrogen  found,  and  also  the  factor  used  for  calcula- 
tion into  proteins,  should  be  stated. 

Returning  to  the  0-01582  gram  of  nitrogen  obtained  in  the  experiment, 
then 

0-01582  X 5-68  = 0-0898  gram  of  true  proteins. 

0-01582  X 6-25  = 0-0989  gram  of  hydrated  proteins. 

These  are  the  quantities  in  1 gram  of  flour,  and  therefore  these  quantities 
X 100  = 8-98  per  cent,  of  true  proteins,  and  9-89  per  cent,  of  hydrated 
proteins  respectively. 

As  0-0014  and  5-68,  and  6-25,  respectively  are  constants,  their  respective 
products,  0-00795  and  0-00875,  may  be  used  as  factors.  Therefore  the 
number  of  c.c.  of  decinormal  acid  neutralised  by  the  evolved  ammonia 
xO-00795  gives  the  weight  of  true  proteins,  and  x 0-00875  gives  the  weight 
of  hydrated  proteins,  in  the  quantity  taken  for  analysis. 

844.  True  Gluten  Estimation. — ^For  jthis  purpose  take  about  0.15  gram 
of  dry  gluten,  weigh  it  accurately,  and  treat  with  acid  and  sulphate  as  with 
the  whole  flour.  Conduct  the  whole  estimation  precisely  as  before  ; then, 
number  of  c.c.  of  NH3  evolved  x 0-00875  = weight  of  true  gluten  (hydrated 
proteins)  in  the  quantity  of  dry  gluten  taken.  The  following  data  show 
the  mode  of  calculation  : — 

Flour  yields  13-10  per  cent,  of  dry  crude  gluten. 

Taken  for  true  gluten  estimation  — 0-152  gram. 


784 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Ammonia  evolved,  less  correction,  14-6  c.c. 

14-6  X 0*00875  = 0*12775  gram  true  gluten. 

As  the  whole  flour  contained  13*10  per  cent,  of  true  gluten,  then  : 

As  0*152  : 13*10  : : 0*12775  = 11*01  per  cent,  of  true  gluten. 
Therefore  : 

Percentage  of  crude  gluten  x true  gluten  found  in  estimation 
Crude  gluten  used  for  estimation  ~ 

percentage  of  true  gluten  in  whole  flour. 

In  order  to  test  the  “ True  Gluten  ” determinations  the  folio vdng 
experiment  was  made  : — Four  glutens  were  extracted  from  the  same  flour, 
one  being  washed,  as  well  as  could  be  judged,  to  the  right  degree  of  purity  ; 
two  of  the  others  were  purposely  underwashed,  and  the  fourth  overwashed. 
The  following  were  the  results  in  wet  and  dry  glutens  : — 


No.  1.  Washed  correctly  . . 
No.  2.  Insufflciently  washed 
No.  3.  Would  pass  for  being 
washed  sufficiently 
No.  4.  Lost  weight  beyond 
No.  1 with  very 
great  difficulty 


Wet  Gluten. 

53*0  per  cent. 
63-0 

56-7 

48-5 


Dry  Gluten. 

16*1  percent. 
20-0 

16-8 


15-1 


True  Gluten. 

15*0  per  cent. 
15*1 

15-1 

14-7  „ 


Note  No.  4 was  weighed  when  at  51  per  cent.,  and  again  washed  in 
clean  water  ; this  water  on  testing  gave  starch  colouration  with  iodine  solu- 
tion, showing  that  even  at  51  per  cent,  starch  was  still  present.  Notwith- 
standing the  wide  differences  in  crude  gluten  between  Nos.  1,  2,  and  3,  the 
true  gluten  is  practically  identical  in  all.  In  No.  4,  however,  the  protein 
itself  is  being  lost.  This  was  an  exceptionally  tough,  hard,  glutenous 
flour,  or  doubtless  there  would  have  been  an  appreciable  difference  in  true 
gluten  between  Nos.  1 and  2.  In  true  gluten  estimations  it  is  recommended 
that  where  the  true  gluten  does  not  amount  to  80  per  cent,  of  the  crude 
gluten,  another  estimation  be  made  of  the  crude  gluten  and  the  first  one 
rejected. 


845.  Modification  of  Process  for  Estimation  of  True  Proteins  only.— 

The  determination  of  proteins  by  the  Kjeldahl  process  is  open  to  the  objec- 
tion that  other  nitrogenous  products  which  existed  in  the  grain  or  flour 
are  also  reckoned  as  nitrogen  from  proteins.  It  is  at  times  of  service  to 
estimate  the  percentage  of  nitrogen  existing  as  proteins  or  flesh  formers, 
as  distinguished  from  other  compounds  of  nitrogen. 

Carbolic  acid  possesses  the  property  of  coagulating  the  soluble  pro- 
teins, and  thus  rendering  their  separation  from  nitrates,  etc.,  comparatively 
easy.  Take  one  gram  of  the  flour  or  meal  and  cover  it  in  a beaker  with 
a warm  4 per  cent,  alcoholic  solution  of  carbolic  acid  : this  may  be  pre- 
pared by  taking  4 grams  of  the  pure  acid,  and  adding  thereto  sufficient 
alcohol  (re-distilled  methylated  spirits)  to  make  up  the  volume  of  100  c.c. 
Let  tliis  stand  for  a quarter  of  an  hour,  then  add  a little  boiling  aqueous 
4 per  cent,  solution  of  carbolic  acid,  stirring  the  mixture  for  about  a 
minute,  and  then  allowing  it  to  cool.  Wash  the  solid  residue  several  times 
})y  decantation  with  the  cold  aqueous  carbolic  acid  solution,  pouring  the 
washings  on  to  a small  Alter,  and  finally  transfer  to  it  the  residue  itself  ; 
thoroughly  dry  tlie  filter  and  residue.  Make  a Kjeldahl  estimation  on  both 
the  residue  and  filter,  cutting  the  latter  up  into  shreds,  and  treating  both 
with  the  acid  and  sulphate  in  the  usual  manner.  The  percentage  of  nitrogen 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  7S5 

thus  obtained,  multiplied  by  6-25,  gives  the  quantity  of  true  hydrated 
proteins. 

846.  Estimation  of  Soluble  Proteins. — ^To  make  this  estimation,  take 
50  c.c.  of  the  filtered  solution  as  prepared  for  soluble  extract,  and  evaporate 
to  dryness  in  one  of  the  acid  flasks.  For  this  purpose  the  flask  should  be 
placed  in  the  hot-water  oven,  as,  unless  the  whole  flask  is  kept  hot,  recon- 
densation occurs.  Even  in  the  hot-water  oven  evaporation  proceeds  but 
slowly ; it  may  be  considerably  hastened  by  immersing  the  flask  in  a bath 
composed  of  water  with  a large  excess  of  potassium  carbonate.  This 
easily  maintains  a temperature  of  110-115°  C.  Treat  the  dry  residue  in 
the  flask  with  acid  and  sulphate,  and  proceed  in  the  usual  manner.  It 
should  be  remembered  that  50  c.c.  contain  the  soluble  proteins  of  5 grams 
of  the  flour. 

847.  Gliadin  Estimations;  Classification  of  Methods. — ^Serious  objec- 
tions have  been  taken  to  gluten  estimations  on  the  ground  that  they  cannot 
afford  a true  determination  of  the  total  protein  content  of  the  flour  ; and 
therefore  it  is  urged  that  they  should  be  dispensed  with  and  instead  a deter- 
mination made  of  the  nitrogen  of  the  flour  and  the  percentage  of  protein  ob- 
tained by  calculation.  Most  of  the  investigations  on  this  matter  have  been 
conducted  with  reference  to  the  strength  of  flour,  and  accordingly  the  various 
researches  and  conclusions  based  thereon  have  been  fully  described  in  Chapter 
XV.  dealing  with  that  subject.  That  chapter  should  be  carefully  read  as  an 
introduction  to  the  whole  question  of  gliadin  determinations.  In  particular, 
the  results  and  conclusions  of  Norton  and  Chamberlain,  paragraphs  450  and 
452,  should  be  studied  in  connection  with  the  point  just  raised.  If  gluten 
determinations  cannot  yield  a true  indication  of  the  protein  content  of  flour,, 
it  follows  that  the  protein  content  cannot  yield  a true  indication  of  the 
gluten  content  of  the  flour.  From  what  has  preceded,  it  will  be  seen  that 
the  authors  regard  that  agglomerate  of  various  flour  constituents,  which 
is  called  gluten,  as  being  the  factor  which  in  virtue  of  its  quantity  and 
quality  largely  dominates  the  properties  of  a flour.  That  body  can  be  de- 
termined with  considerable  accuracy  by  a simple  physical  operation,  and 
possesses  well-marked  physical  characteristics.  They  therefore  attach 
importance  to  its  estimation.  It  being  known  that  gluten  is  largely  com- 
posed of  glutenin  and  gliadin,  and  that  these  bodies  may  roughly  be 
compared  to  the  sand  and  lime  in  a sample  of  mortar,  one  being  the 
component  which  gives  substance  and  the  other  the  constituent  which  acts 
as  a binding  agent,  it  would  seem  that  the  relative  proportions  of  each  must 
exert  a considerable  effect  on  the  qualities  of  gluten.  Accordingly,  the 
effect  of  such  relative  proportions  has  received  most  careful  examination. 
Certain  earlier  observers,  as  for  example  Guthrie  and  Fleurent,  attached 
considerable  importance  to  the  proportions  of  each,  and  have  suggested 
the  bearing  which  they  have  on  the  character  of  flour.  Others,  among 
whom  are  included  Snyder  and  Wood,  have  arrived  at  the  conclusion  that 
flours  cannot  be  differentiated  in  quality  according  to  the  proportions  of 
gliadin  and  glutenin.  Thus  Snyder  finds  that  gliadin  may  range  from  45 
to  70  per  cent,  of  the  total  protein,  without  the  flour  being  affected  in  any 
but  a minor  degree.  Almost  every  one  of  those  who  have  investigated  the 
problem  has  adopted  a different  method  of  determination,  and  therefore 
no  very  direct  comparisons  can  be  made.  Further,  from  time  to  time,  each 
operator  has  modified  his  own  methods  as  possible  improvements  have 
suggested  themselves.  The  methods  adopted  divide  themselves  into  (1) 
direct  estimations  on  the  flour,  and  (2)  estimations  made  on  the  washed  out 
gluten.  Each  of  these  merits  some  little  examination  in  detail. 

.3  E 


786 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


848.  Gliadin  Estimations  on  Flour. — ^On  treating  flour  with  70  per  cent, 
alcohol,  the  gliadin,  together  with  some  portion  of  the  water-soluble  pro- 
teins, as  well  as  the  soluble  carbohydrates  and  soluble  ash,  is  dissolved  out. 
It  is  therefore  not  possible  to  estimate  gliadin  by  direct  w'eighing  of  the 
residue  from  the  evaporated  filtered  solution,  but  instead,  recourse  must  be 
had  to  a nitrogen  determination  on  the  filtrate  by  the  Kjeldahl  process. 
Chamberlain  has  carefully  investigated  the  extraction  of  gliadin,  paragraph 
452,  and  recommends  that  the  estimation  be  made  in  the  following  manner  : 
— Cold  70  per  cent,  alcohol  should  be  used  directly  on  the  air-dry  flour, 
and  100  c.c.  of  the  solvent  should  be  taken  to  either  2 or  4 grams  of  the 
flour,  the  extraction  being  continued  for  24  hours  with  frequent  or 
continuous  shaking.  These  suggestions  are  now  apparently  adopted  by 
most  American  chemists,  thus  Teller  finds  the  most  convenient  means  of 
determining  the  gliadin  in  wheat  flours  to  be  as  follows  : — ‘‘  Two  grams  of 
the  flour  are  put  in  a flask  of  about  150  c.c.  capacity,  100  c.c.  of  dilute  alcohol, 
specific  gravity  0-90,  are  then  added  to  the  flour,  care  being  taken  to  mix 
the  flour  well  with  a small  quantity  of  the  alcohol  before  the  entire  amount 
is  added.  The  flask  is  then  set  aside  at  room  temperature  for  24  hours, 
shaking  occasionally  to  assure  thorough  extraction  of  the  gliadin.  The 
liquid  is  then  filtered  and  50  c.c.  of  the  clear  filtrate  taken  for  determina- 
tion of  nitrogen.  The  alcohol  should  be  evaporated  off  on  the  steam  bath 
before  the  sulphuric  acid  is  added  to  avoid  charring  of  the  alcohol.  The 
nitrogen  obtained  is  then  multiplied  by  the  factor  5-7,  or,  as  we  find  it  more 
convenient  in  our  laboratories  here,  the  number  of  c.c.  of  decinormal  acid 
obtained  for  each  gram  of  flour  is  multiplied  by  the  factor  0-8.  This  gives 
the  per  cent,  of  gluten  or  gliadin  direct.  In  our  commercial  work  here  we 
determine  the  gluten  by  the  Kjeldahl  method,  using  1 gram  of  flour  and 
multiplying  the  titration  of  ammonia  obtained  by  the  factor  0-8  as  given 
above.  We  find  this  to  give  as  nearly  the  true  amount  of  gluten  in  the 
flour  as  can  be  done  by  the  most  careful  hand  washing,  and  it  is  much  more 
reliable  when  the  work  is  done  by  different  operators  on  different  days.” 
[Personal  communication,  May,  1910.) 

In  a paper,  previously  quoted.  Teller  has  shown  that  alcohol  of  0-90 
specific  gravity,  i.e.,  57  per  cent,  strength,  dissolves  more  nitrogenous 
matter  from  flour  than  does  70  per  cent,  spirit.  This  points  to  the  fact 
that  the  dilute  alcohol  takes  up  some  of  the  water-soluble  proteins  in  addi- 
tion to  gliadin  proper.  Chamberlain  also  states  that  hot  alcohol  dissolves 
out  less  protein  than  does  cold,  and  therefore  recommends  the  latter.  This 
again  is  an  indication  that  other  protein  than  gliadin  is  being  dissolved, 
since  gliadin  is  more  readily  dissolved  on  the  application  of  heat  than  in  the 
cold  : on  the  other  hand  proteins  of  the  albumin  type  become  less  soluble 
because  of  coagulation.  It  is  important  also  to  consider  the  bearing  of  the 
length  of  time  of  extraction  in  view  of  the  nature  of  the  solvent,  a dilute 
solution  of  alcohol  not  being  capable  of  inhibiting  proteolytic  action.  Air- 
dried  gliadin  is  “ very  soluble  ” in  70  per  cent,  alcohol,  and  must  be  at  least 
equally  soluble  in  the  finely  divided  condition  in  which  it  naturally  occurs 
in  flour.  With  the  use  of  a very  large  excess  of  the  solvent,  it  would  seem 
that  the  increase  of  protein  dissolved  by  greatly  prolonged  extraction  is 
not  merely  gliadin,  but  contains  in  addition  alcohol  soluble  protein  produced 
by  proteolytic  action  on  protein  matter,  which  at  the  outset  is  insoluble 
in  the  dilute  alcohol.  Corroboration  of  this  is  afforded  by  the  fact  that 
when  dough  is  allowed  to  stand  under  conditions  which  favour  proteolytic 
action,  there  is  a marked  increase  in  the  quantity  of  dilute  alcohol  soluble 
l^rotein.  The  method  employed  must  be  regarded  as  a measure  of  the 
amount  of  protein  dissolved  in  dilute  alcohol  under  certain  definite  con- 
ditions, but  evidently  is  not  a measure  of  gliadin  only.  Another  point 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


787 


which  has  to  be  considered  is  that  according  to  Chamberlain,  of  the  total 
gliadin  and  glutenin  contained  in  the  wheat  and  flour,  only  about  85  per 
cent,  can  be  obtained  as  gluten  by  the  washing  process.  On  this  the  question 
arises  whether  this  balance  of  15  per  cent,  is  a loss  due  to  inherent  faultiness 
of  the  gluten  washing  process,  or  whether  it  is  the  result  of  some  of  the  gliadin 
and  glutenin  being  in  a non-adhesive  condition  and  therefore  not  function- 
ing as  gluten.  This  matter  has  been  already  discussed  (see  paragraph 
469),  and  if  the  authors’  view  be  correct,  then  flour  contains  some  gliadin 
which  would  be  determined  as  such  in  a direct  estimation  on  the  flour,  and 
yet  is  not  contributing  to  its  strength. 

The  method  adopted  by  the  authors  is  substantially  the  same  as  that 
of  Teller,  except  that,  following  more  closely  on  the  lines  of  Chamberlain, 
they  use  hot  70  per  cent,  alcohol,  and  take  400  c.c.  to  4 grams  of  flour, 
(a  quantity  which  may  be  somewhat  in  excess  of  that  absolutely  necessary.) 
They  shake  frequently  during  the  24  hours,  or  preferably  shake  con- 
tinuously in  a shaking  machine,  a description  of  which  is  subsequently 
given  in  paragraph  854.  After  filtration,  200  c.c.  of  the  clear  filtrate  are 
placed  in  a 500  c.c.  long  necked  Jena  flask.  This  is  immersed  in  a bath  of 
potassium  carbonate  and  water,  and  connected  to  a spiral  condenser.  The 
alcohol  is  distilled  off,  and  then  the  flask  is  disconnected  and  the  heating 
continued  until  the  solution  is  evaporated  to  dryness.  This  takes  place 
rapidly  with  the  bath  at  110-115°  C.  The  Kjeldahl  determination  is  then 
made  on  the  residue,  and  the  results  calculated  in  the  usual  way. 

849.  Gliadin  Estimations  on  Wet  Gluten. — The  foregoing  considerations 
have  caused  the  authors  to  incline  to  determinations  made  on  the  wet 
gluten  itself  as  being  more  likely  to  have  a direct  bearing  on  the  problem  of 
the  quality  of  gluten  and  its  effect  on  the  strength  of  flour.  In  gluten- 
washing those  bodies  which  do  not  go  to  the  building  up  of  that  india-rubber 
like  body  are  eliminated.  The  soluble  carbohydrates  and  ash  have  been  more 
or  less  removed,  and  also  such  soluble  proteins  as  are  not  retained  by  the 
absorptive  power  of  the  gluten  proteins.  If  therefore  the  alcohol  solvent  be 
applied  to  this  body  it  can  only  extract  what  is  practically  soluble  protein 
and  the  small  amount  of  mineral  bodies  which  is  inherently  associated 
with  this  substance. 

From  its  physical  nature,  gluten  is  a difficult  body  to  treat  with  a sol- 
vent. Guthrie  extracted  the  wet  gluten  with  successive  small  quantities 
of  70  per  cent,  alcohol,  the  operation  extending  over  four  and  a half  days. 
He  thus  obtained  from  22  to  41  per  cent,  of  the  gluten  proteins  as  gliadin. 
There  is  always  the  uncertainty  that  in  so  long  a time  some  of  the  gluten 
which  at  first  was  insoluble  in  dilute  alcohol  becomes  soluble  by  a process 
of  degradation  due  to  proteolytic  enzymes.  For  this  reason  some  quicken- 
ing of  the  dissolving  operation  is  eminently  desirable. 

Fleurent  adopted  another  method  and  dissolved  the  whole  of  the  gluten 
in  alcoholic  potash  solution,  and  then  converted  the  hydroxide  into  car- 
bonate by  passing  carbon  dioxide  gas  through  the  solution,  thus  re-precipi- 
tating the  glutenin  and  leaving  gliadin  in  solution.  As  potassium  carbonate 
is  somewhat  soluble  in  70  per  cent,  alcohol,  there  was  still  an  active  glutenin 
solvent  present,  and  therefore  it  might  well  be  expected  that  the  whole  of 
the  glutenin  would  not  be  re -precipitated.  By  this  process  he  obtained 
from  the  best  flours  about  75  per  cent,  of  the  gluten  proteins  as  gliadin, 
an  amount  which  is  much  in  excess  of  the  usual  estimate. 

850.  Gliadin  Estimations  by  Calcium  Carbonate. — ^The  authors  devised 
and  adopted  a method  which  was  intended  to  avoid  the  difficulties  associated 
with  both  Guthrie’s  and  Fleurent’s  processes,  of  which  the  following  is  an 
outline.  Twenty  grams  of  flour  were  washed  for  gluten,  and  the  wet  gluten 


788 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


weighed.  This  was  divided  into  two  equal  parts,  one  of  which  was  dried 
and  weighed,  and  a portion  used  for  the  determination  of  true  gluten.  The 
remaining  moiety  was  placed  in  a mortar  and  20  grams  of  washed  and  dried 
precipitated  chalk  (calcium  carbonate)  added.  (This  chalk  was  washed 
until  it  gave  no  alkaline  reaction  to  the  washing  water  after  filtration.) 
One  hundred  c.c.  of  70  per  cent,  alcohol  were  measured  off,  and  about  6 c.c. 
poured  into  the  mortar.  This  mixture  was  then  thoroughly  triturated 
with  the  pestle,  and  more  alcohol  added  as  required  until  it  had  been  ground 
down  into  a perfectly  uniform  slack  dough.  The  whole  of  the  gluten  was 
thus  perfectly  comminuted.  This  was  done  with  the  greatest  care.  The 
piece  of  dough  was  then  transferred  to  a flask,  the  remainder  of  the  alcohol 
added,  and  the  whole  vigorously  shaken.  The  dough  was  thus  broken 
down  into  an  impalpable  powder,  which  was  examined  through  the  glass 
of  the  flask  to  see  that  no  perceptible  particles  of  gluten  were  present.  (At 
first,  some  such  particles  were  occasionally  detected  and  the  test  rejected  ; 
but  after  a little  experience  this  never  happened.)  The  flask  was  next 
immersed  in  hot  water,  and  the  alcohol  brought  quickly  to  the  boiling  point. 
As  soon  as  this  was  reached,  the  flask  was  corked  and  shaken.  The  shaking 
was  repeated  several  times  while  the  mixture  was  warm.  It  was  then 
allowed  to  stand  over  night  at  room  temperature.  In  the  morning,  there 
was  usually  a slight  deposit  of  protein  matter  on  the  sides  of  the  flask,  which 
was  assumed  to  consist  of  glutenin  that  had  been  dissolved  by  the  hot  alcohol 
and  re-deposited  as  it  cooled.  The  conditions  of  treatment  were  such  as 
should  lead  to  the  perfect  solution  of  the  very  soluble  gliadin  in  the  solvent, 
while  there  was  comparatively  a very  short  time  during  which  any  actual 
change  in  the  gluten  could  take  place.  With  the  gluten  so  finely  divided, 
it  was  all  immediately  subjected  to  the  action  of  the  alcohol,  and  the  tem- 
perature having  been  raised  to  about  70°  C.,  enzymes  must  have  been  prac- 
tically destroyed.  On  first  employing  this  process  the  alcohol  solution 
was  immediately  filtered  hot,  and  the  gliadin  obtained  by  evaporating  50 
c.c.  of  the  filtrate  and  drying  and  weighing  the  residue.  In  this  way  about 
50  to  60  per  cent,  of  the  gluten  proteins  were  obtained  as  gliadin.  After- 
ward the  solution  was  allowed  to  cool  as  described,  with  the  result  that  much 
less  gliadin  was  obtained. 

851.  Further  Investigation  of  Trituration  Methods. — ^For  the  purposes 
of  this  work,  the  authors  have  recently  re-investigated  the  method,  being 
guided  in  so  doing  by  Chamberlain's  conclusions  on  extraction  of  gliadin 
from  flour.  The  following  experiments  were  made.  Sixty  grams  were 
taken  of  millennium  flour,  made  into  a dough  with  40  c.c.  of  water,  and 
the  gluten  carefully  washed  out  at  tlie  end  of  an  hour.  The  wet  gluten 
weighed  21-426  grams  = 35-71  per  cent.  A portion,  3 grams,  was  dried 
and  weighed;  it  was  thus  found  that  the  dry  gluten  amounted  to  12-22 
per  cent,  of  the  whole  flour.  The  70  per  cent,  alcohol  was  tested  and 
found  to  leave  on  evaporation  0-002  gram  per  100  c.c.  Portions  of  2 
grams  each  were  at  once  weighed  off,  as  soon  as  the  whole  mass  of  wet 
gluten  had  been  weighed,  and  were  treated  as  follows  : — 

No.  1.  Ground  up  with  20  grams  of  chalk,  and  500  c.c.  of  cold  alcohol, 
shaken  frequently  and  filtered  at  the  end  of  2 hours  ; 250 
c.c.  evaporated  for  gliadin,  dried  and  weighed. 

No.  2.  Taken,  20  grams  of  chalk,  100  c.c.  of  alcohol,  shaken  frequently 
and  filtered  at  the  end  of  24  hours  ; 50  c.c.  evaporated  for 
gliadin. 

No.  3.  Twenty  grams  of  chalk,  200  c.c.  of  alcohol,  shaken  as  before 
and  filtered  at  24  hours  ; 100  c.c.  evaporated  for  gliadin. 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  789 

No.  4.  Twenty  grams  of  chalk,  300  c.c.  of  alcohol,  treated  for  24  hours  ; 
150  c.c.  of  filtrate  evaporated  for  gliadin. 

No.  5.  Twenty  grains  of  chalk,  400  c.c.  of  alcohol,  treated  for  24  hours  ; 
200  c.c.  of  filtrate  evaporated  for  gliadin. 

No.  6.  Twenty  grams  of  chalk,  500  c.c.  of  alcohol,  treated  for  24  hours  ; 
250  c.c.  of  filtrate  evaporated  for  gliadin. 

No.  7.  Ten  grams  of  thoroughly  washed  and  dried  kieselguhr,  500 
c.c.  of  alcohol,  treated  for  24  hours  ; 250  c.c.  of  filtrate  eva- 
porated for  gliadin. 

As  kieselguhr  is  more  bulky  than  chalk  a less  volume  of  it  was  deemed 
sufficient.  Blank  tests  were  made  both  with  the  chalk  and  the  kieselguhr, 
and  the  weight  of  residue  deducted  as  a correction  from  that  found  with 
the  tests  on  gluten.  The  following  were  the  quantities  of  gliadin  thus 
obtained  : — 

No.  1.  1*89  per  cent,  of  the  whole  flour. 

2.  D68 

.,  3.  214 

„ 4.  2-21 

„ 5.  2-21 

„ 6.  2-68 

„ 7.  3-29 

The  quantities  of  200,  300  and  400  c.c.  yielded  practically  the  same 
amounts  with  chalk,  while  more  was  obtained  with  500  c.c.  With  kiesel- 
guhr, -the  amount  was  considerably  higher. 

Some  more  wet  gluten  was  prepared  from  the  same  flour,  and  portions 
of  2 grams  each  were  subjected  to  the  following  further  tests.  Some  kiesel- 
guhr was  broken  down  in  water,  and  poured  through  a fine  sieve  in  order 
to  remove  all  lumps,  then  allowed  to  settle  and  the  fine  kieselguhr,  in  a state 
of  suspension,  decanted  off  from  the  sandy  sediment.  The  kieselguhr 
was  repeatedly  washed  with  water,  and  then  several  times  with  90  per  cent, 
alcohol,  and  dried.  As  thus  obtained  it  is  a very  bulky  powder  : — 

No.  8.  Ground  up  the  gluten  in  mortar  with  successive  small  quan- 
tities of  cold  alcohol,  and  liquid  transferred  to  flask,  using 
altogether  400  c.c.  This  operation  lasted  48  hours  ; then 
filtered,  evaporated  200  c.c.  for  gliadin,  dried  and  weighed. 

No.  9.  Cut  gluten  into  small  pieces,  boiled  with  about  25  c.c.  of  alcohol, 
then  ground  up  in  mortar  as  before,  using  altogether  400  c.c. 
Time,  48  hours.  Filtered,  evaporated  200  c.c.  for  gliadin. 

No.  10.  Three  grams  specially  prepared  kieselguhr,  400  c.c.  of  cold 
alcohol,  treated  for  24  hours  ; 200  c.c.  evaporated  for  gliadin. 

No.  11.  Three  grams  kieselguhr,  400  c.c.  of  alcohol,  raised  to  boiling 
point,  shook  repeatedly  for  24  hours  ; evaporated  200  c.c.  for 
gliadin. 

No.  12.  Blank  with  3 grams  of  kieselguhr,  and  400  c.c.  of  alcohol, 
treated  for  24  hours,  and  evaporated  200  c.c.  of  filtrate. 

The  blank  gave  a residue  of  0-004  gram,  which  was  deducted  from  the 
weight  of  gliadin  in  Nos.  10  and  11.  The  following  quantities  of  gliadin 
were  obtained  : — 

No.  8.  5-99  per  cent,  of  the  whole  flour. 

5,  9.  4-21  ,,  ,,  ,, 

„ 10.  4-07 

,,11.  4-/1  ,,  ,,  ,, 

Under  these  conditions,  cold  alcohol,  only,  extracted  more  than  the  hot ; 
while  when  kieselguhr  also  was  employed  more  gliadin  was  obtained  as  a 
result  of  heating. 


? ? ? ? ? ? 

??  J? 

?5  ??  ?? 

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?? 

55  55  55 


790 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Adsorptive  Properties  of  Re-agents. — By  adsorption  ” is  here  meant  the 
removal  of  a body  from  its  solution,  by  the  adherence  of  its  particles  to 
those  of  some  solid  substance  which  has  been  introduced. 

Experiments  were  next  made  in  order  to  determine  whether  the  filter 
papers  or  the  kieselguhr  exercised  any  adsorptive  effect  on  the  gliadin  in 
solution.  Twenty  grams  of  wet  gluten  from  the  same  flour  were  ground 
up  with  successive  small  quantities  of  spirit,  the  operation  lasting  about  16 
hours,  and  altogether  378  c.c.  of  filtrate  were  obtained.  This  volume  does 
not  represent  the  whole  of  the  alcohol  used,  since  a portion,  together  with 
some  gliadin,  remained  on  the  filter.  On  this,  the  following  tests  were  made : — 

a.  100  c.c.  evaporated,  weight  of  dry  residue,  0-515  gram. 

h.  100  c.c.  mixed  with  3 grams  special  kieselguhr,  allowed  to  stand 
24  hours  and  filtered,  70  c.c.  of  filtrate  evaporated,  weight  of  dry  residue, 
0-272  = 0-389  in  100  c.c. 

c.  100  c.c.  mixed  with  7 grams  of  starch  from  same  flour.  (The  starch 
was  washed  first  with  water,  and  then  several  times  with  90  per  cent,  alcohol, 
and  dried  at  about  60°  C.)  Gliadin  solution  allowed  to  stand  24  hours  and 
filtered,  85-5  c.c.  of  filtrate  evaporated,  weight  of  dry  residue,  0-440  =0-514 
gram  in  100  c.c. 

d.  78  c.c.  re-filtered  through  a fresh  dry  paper,  74-5  c.c.  of  filtrate  eva- 
porated, weight  of  dry  residue,  0-380  = 0-510  in  100  c.c. 

The  kieselguhr  exerts  a very  considerable  adsorptive  action,  about  24 
per  cent,  of  the  gliadin  present  in  the  solution  being  retained  in  the  kiesel- 
guhr. Wheat  starch,  on  the  other  hand,  is  absolutely  free  from  any  such 
adsorptive  power.  The  filter  paper  also  is  without  action.  As  kieselguhr 
extracts  more  gliadin  from  gluten  than  does  chalk,  no  tests  were  made  on 
the  adsorptive  power  of  the  latter,  which  in  the  quantity  used  would  pre- 
sumably retain  yet  more  gliadin. 

The  residual  gluten  from  the  treated  20  grams  was  yet  again  subjected 
to  further  treatment  with  more  alcohol,  extending  over  another  24  hours ; 
this  removed  yet  more  gliadin,  the  amounts  of  dry  gliadin  being  : — 

From  1st.  extraction  ..  ..  ..  ..  1-9467  grams. 

„ 2nd.  „ 0-3590 


Total 2-3057 

Twenty  grams  of  wet  gluten  (about  6-6  grams  of  dry  gluten),  had  there- 
fore yielded  2-306  grams  of  gliadin.  The  residual  wet  glutenin  weighed 
10  grams  ; a portion  of  this  was  treated  as  subsequently  described.  No.  16. 

852.  Solution  and  Re-precipitation  Methods. — ^Experiments  were  next 
made  in  the  direction  of  dissolving  the  whole  of  the  gluten  in  weak  alcoholic 
soda  solution,  then  re-precipitating  the  glutenin,  and  determining  the  gliadin 
in  the  filtrate. 

No.  13.  For  the  first  test,  1-59  grams  of  wet  gluten  were  taken,  and 
triturated  with  3 grams  of  special  kieselguhr,  and  400  c.c.  of 
cold  70  per  cent,  alcohol  containing  approximately  0-5  gram 
of  stick  sodium  hydroxide.  This  was  frequently  shaken  and 
allowed  to  stand  over  night  (about  18  hours).  Two  hundred 
c.c.  were  then  taken  and  filtered,  the  volume  of  the  filtrate 
being  194  c.c.  Tliis  was  rendered  faintly  acid  by  the  addition 
of  hydrochloric  acid  in  slight  excess,  using  phenolphthalein 
as  an  indicator,  and  evaporated  to  dryness  in  a weighed 
platinum  dish,  after  weighing  which  the  ash  was  determined. 
Tlie  organic  matter  was  calculated  into  percentage  on  the 
whole  flour,  and  returned  as  dry  gluten.  To  the  remaining 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  791 

alkaline  200  c.c.,  10  per  cent,  sulphuric  acid  was  added  in 
measured  quantity,  until  the  solution  was  faintly  acid  to 
phenolphthalein.  A very  small  quantity  of  chalk  was  then 
added  to  neutralise  the  excess  of  sulphuric  acid.  The  solu- 
tion was  frequently  well  shaken,  and  then  allowed  to  stand 
over  night.  In  the  morning  there  was  a coj)ious  precipitate 
of  glutenin  which  was  filtered  off.  The  filtrate  was  measured, 
and  the  total  residue  and  ash  determined  as  before.  Allow- 
ing for  the  volume  of  sulphuric  acid,  the  organic  matter  was 
calculated  into  percentage  on  the  whole  flour,  and  returned  as 
gliadin. 

No.  14.  Two  grams  wet  gluten  taken,  pulled  into  very  small  fragments, 
400  c.c.  of  OT  per  cent,  sodium  hydroxide  in  70  per  cent, 
alcohol,  taken  cold.  Was  shaken  up  frequently,  took  24 
hours  to  dissolve.  Filtered  200  c.c.,  treated  with  hydrochloric 
acid,  evaporated  filtrate,  and  determined  residue  and  ash  as 
before  for  dry  gluten.  Remaining  200  c.c.  rendered  acid 
by  measured  10  per  cent,  sulphuric  acid,  neutralised  by  very 
slight  excess  of  chalk,  stood  over  night.  Filtered  off  glutenin, 
determined  residue  and  ash  in  filtrate  as  before  for  gliadin. 

No.  15.  Same  quantities  and  process  as  No.  14,  except  that  the  gluten 
and  alkaline  alcohol  were  raised  to  boiling  point,  and  shaken 
hot.  The  gluten  quickly  dissolved  (within  an  hour),  the 
solution  was  at  once  filtered  and  dry  gluten  and  gliadin  esti- 
mated as  before. 

No.  16.  Two  grams  of  wet  glutenin,  being  a portion  of  the  residual 
mass  of  10  grams  obtained  in  the  previously  described  experi- 
ment of  extraction  of  gliadin  from  20  grams  of  wet  gluten. 
Treated  as  in  No.  14  with  alkaline  alcohol.  Dissolved  fairly 
quickly  in  cold  ; after  two  hours,  decanted  solution,  and  tri- 
turated the  remaining  solid  in  mortar  till  dissolved.  Filtered 
and  estimated  dry  gluten  and  gliadin  as  before. 

The  following  are  the  quantities  of  gliadin  obtained,  expressed  as  before : — 

No.  13.  7*86  per  cent,  of  the  whole  flour. 

„ 14.  8*87 
„ 15.  9-21 


The  next  table  contains  further  details  of  the  last  four  tests  : — 


Constituents. 

13. 

14. 

15. 

1 16. 

1 

Percentages. 

Wet  Gluten  on  whole  flour 

35-71 

35-71 

35-71 

35-71 

Dry  Gluten,  by  direct  weighing,  on  whole  flour 

12-22 

12-22 

12-22 

12-22 

Dry  Gluten,  by  evaporation  of  solution,  on  whole  flour 

11-76 

11-88 

11-81 

— 

Gliadin,  by  evaporation  of  solution,  on  whole  flour  . . 

7-86 

8-87 

9-21 

— 

Crude  Glutenin,  by  difference  . . 

3-90 

3-01 

2-60 

— 

Components  of  the  2 Grams  of  Wet  Gluten  and  Wet  “ Glutenin,” 
Xo.  16. 

Grams. 

Water,  with  small  quantity  of  Cellulose 

1-341 

1-335 

1-339 

1-227 

Dry  Gluten 

0-659 

0-665 

0-661 

0-773 

Gliadin 

0-440 

0-492 

0-521 

0-271 

Crude  Glutenin 

i 

0-219 

0-173 

0-140 

0-502 

792 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  gliadin  obtained  by  solution  of  the  whole  of  the  wet  gluten,  and 
subsequent  re-precipitation  of  the  glutenin,  is  much  more  than  that  yielded 
by  any  of  the  processes  of  direct  extraction  of  the  gluten  that  have  been 
described.  For  this  there  may  be  two  reasons,  either  that  none  of  the 
direct  solution  processes  succeeds  in  extracting  the  whole  of  the  gliadin, 
or  that  the  glutenin  once  entirely  dissolved  is  not  completely  re-precipitated 
on  rendering  the  solution  neutral.  Some  little  light  is  thrown  on  this  by 
test  No.  16.  As  a result  of  direct  treatment  of  20  grams  of  wet  gluten  in 
the  manner  described,  2-3057  grams  of  gliadin  were  extracted.  From  the 
residual  10  grams  of  gluten  not  dissolved  by  the  alcohol,  0-271  x 5 = 1-355 
grams  of  gliadin  were  obtained  by  solution  in  alkaline  alcohol  and  re-precipi- 
tation, making  a total  of  2-3057  + 1-355  = 0-36607  grams  of  gliadin,  being 
equal  to  6-53  per  cent,  of  the  whole  flour.  It  will  be  seen  therefore  that 
after  a very  thorough  exhaustion  of  wet  gluten  by  alcohol,  a further  quantity 
of  gliadin  is  yielded  by  solution  and  re-precipitation. 

853.  Further  Tests  on  Starch  Treatment  of  Gluten. — In  view  of  the  fact 
that  grinding  with  wheaten  starch  successfully  comminutes  gluten,  and 
that  unlike  chalk  or  kieselguhr,  the  starch  exercises  no  adsorptive  effect  on 
the  gliadin  in  solution,  further  experiments  were  made  with  this  reagent. 
Using  wet  gluten  from  the  same  flour,  mixtures,  as  below,  were  made  up  : — 

No.  1.  Wet  gluten,  2 grams  ; wheat  starch,  10  grams  ; 70  per  cent. 

alcohol,  400  c.c.  used  cold.  The  gluten  and  starch  were 
rubbed  down  with  a few  c.c.  of  the  spirit  into  a smooth  creamy 
dough,  which  was  then  placed  in  a bottle  with  the  remainder 
of  the  spirit,  and  shaken  in  the  shaking  machine  over  night, 
(about  15  hours). 

No.  2.  Starch  and  cold  alcohol  only.  Treated  as  No.  1. 

No.  3.  Same  quantities  as  No.  1,  but  alcohol  used  hot.  Treated  as 
No.  1. 

No.  4.  Starch  and  hot  alcohol  only.  Treated  as  No.  1. 

The  solids  of  all  had  completely  broken  down  when  examined  in  the 
morning.  The  solutions  were  then  filtered.  They  filtered  very  quickly 
and  perfectly  bright.  Of  the  filtrates,  200  c.c.  were  taken,  evaporated  to 


dryness,  and  the  residues  weighed 

: — 

0-206 

Weight  in  grams 

0-183 

0-021 

0-023 

0-021 

0-023 

Net  weight  of  Nos.  1 and  3.  . 

0-162 

0-183 

It  will  be  noticed  that  extraction  with  hot  spirit  gave  a higher  result 
than  with  cold.  The  soluble  matter,  yielded  by  the  starch  only,  agreed 
closely  in  Nos.  2 and  4.  It  was  thought  desirable,  however,  to  further 
purify  some  starch  ; and  1,000  grams  were  taken  and  washed  with  about 
4 litres  of  hot  70  per  cent,  alcohol  in  the  shaking  machine  for  24  hours. 
The  starch  was  filtered  from  the  spirit,  pressed  fairly  dry,  and  again  washed 
with  a similar  quantity  of  hot  70  per  cent,  alcohol  for  another  24  hours 
in  the  machine,  and  filtered  and  pressed.  A third  washing  was  then  given 
with  95  per  cent,  alcohol  in  the  same  way,  after  which  the  pressed  starch 
was  carefully  air-dried  in  a warm  room.  This  is  termed  spirit-washed 
starch. 

Time  Test. — In  order  to  determine  the  time  necessary  for  extraction, 
five  tests  of  2 grams  of  wet  gluten,  10  grams  of  starch,  and  400  c.c.  of  hot 
70  per  cent,  alcohol  were  treated  as  before  by  making  a dough  and  shaking 
with  the  spirit  in  the  shaking  machine.  A sixth  consisted  of  the  spirit- 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


793 


1. 

6 

0*180 

2. 

12 

0*187 

3. 

24 

0*189 

4. 

48 

0*182 

.5. 

72 

0*185 

6. 

48 

0*007 

0*173 

0*180 

0*182 

0*182 

0*185 

— 

6*18 

6*43 

6*44 

6*25 

6*36 

— 

5*12 

5*31 

5*19 

5*25 

5*31 

Nil. 

washed  starch  and  alcohol  only.  Gliadin  by  weight  was  determined 
in  200  c.c.  of  the  filtrate,  and  organic  nitrogen  in  100  c.c.  by  the  Kjeldahl 
method.  The  following  are  the  results  : — 

Shaken  for  hours 
Gliadin  by  weight,  grams 
Less,  0*007  for  Starch  cor- 
rection . . 

Gliadin  by  weight,  per 
cent.,  on  Flour 
Gliadin  from  Organic 
Nitrogen,  per  cent.  . . 

The  results  agree  very  closely,  and  indicate  that  anything  from  12  to 
24  hours  is  a sufficient  time  for  extraction.  The  organic  nitrogen  deter- 
minations also  closely  agreed,  but  using  the  6-25  factor  for  proteins,  the 
results  run  below  the  figures  obtained  by  direct  weighing. 

Quantity  Test. — With  the  best  time  from  last  test,  24  hours,  a number  of 
experiments  was  made  with  varying  quantities  of  wet  gluten  and  starch. 
In  all  cases,  400  c.c.  of  hot  alcohol  Avas  used  for  dough-making  and  extract- 
ion. The  shaking  was  done  in  the  shaking  machine.  The  following  are 
the  particulars  : — 

2 grams  ; spirit-washed  starch,  10  grams. 

3 55  5 5 5 5 lb  ,, 

4 „ „ „ 20  „ 

5 „ „ „ 25  „ 


No.  1.  Wet  gluten, 
55  2.  „ 

55  3.  ,,  ,, 

4. 


necessary  starch  correction  was  made  in  each 


Gliadin  by  AA  cight  in  grams 
Gliadin  from  2 grams  of  Gluten 
Gliadin  by  AA'eight  per  cent,  on  Flour  . 


0-i86 

0186 

6-64 


of  the  bright  filtrate.  The 
case. 

2. 

3.  4. 

0-275 

0-355  0-459 

0-183 

0-177  0-184 

6-55 

6-34  6-55 

Again,  there  is  very  elose  agreement  betAA^een  the  results  obtained  on 
AA’idely  differing  quantities,  shoAAung  that  the  solvent  poAA'er  of  the  spirit 
is  Avell  in  excess  of  the  amount  required.  But  AAith  the  larger  quantities 
of  gluten,  the  grinding  operation  became  very  tedious,  and  the  difficulty 
of  avoiding  the  escape  of  comparatively  large  fragments  from  grinding  Avas 
materially  increased. 


854.  Standard  Starch  Method  for  Estimation  of  Gliadin. — ^The  folloAving 
quantities,  times,  and  method  of  AA’orking  A\  ere  ultimately  adopted  : 

Quantities,  2-2  grams  AA  et  gluten,  11  grams  of  spirit-AA'ashed  starch,  400  c.c. 
of  70  per  cent,  alcohol.  After  measuring  the  alcohol,  10  c.c.  A\'ere  reserved, 
and  the  remainder  raised  to  the  boiling  point.  In  practice,  this  AA^as  done 
by  connecting  the  flask  to  a return  spiral  condenser,  so  that  there  AA^as  no 
loss  on  the  spirit  commencing  to  boil.  The  AA^eighed  gluten  and  about  half 
the  starch  Avere  then  placed  in  the  mortar  and  ground  up  Avith  a feAV  drops 
of  the  reserved  alcohol  into  a thin  dough.  This  AA^as  stiffened  by  the  addition 
of  a little  more  starch,  and  tlie  grinding  continued,  a little  more  alcohol  AA^as 
then  added,  and  so  as  again  to  make  a thin  dough,  and  then  a little  more 
starch.  By  this  alternate  addition  of  starch  and  alcohol,  the  gluten  AA^as 
rapidly  disintegrated,  and  finally  aa  ^s  obtained  as  a perfectly  smooth  dough. 
This  AA'as  carefully  transferred  into  a shaking  bottle  of  1 litre  capacity. 
Any  cold  alcohol  remaining  AA^as  added,  and  then  the  alcohol  from  the  flask, 
AA'hich  by  that  time  Avill  have  got  to  the  boil.  The  bottle  AA'as  then  at  once 
introduced  into  the  shaking  machine,  aa  here  in  practice  it  remained  about 
eighteen  hours. 


794 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  following  is  a description  and  illustration,  Fig.  118,  of  an  installa- 
tion of  shaking  apparatus  supplied  to  the  authors  by  Gallenkamp  & Co 
Ydien  electricity  is  available,  the  most  convenient  source  of  power  is  a 
small  electric  motor  A.  This  is  started  and  regulated  by  the  graduated 
switch,  B.  In  order  to  slow  down  the  speed,  the  motor  is  geared  up  with  a 
countershaft,  C ; which  in  turn  drives  the  main  pulley,  D,  of  the  shaking 
machine.  The  machine  is  made  to  hold  six  or  ten  bottles,  each  of  which 
stands  in  a socket,  E,  of  the  right  size.  The  sliding  cap,  F,  is  then  placed 
dovTi  to  hold  the  bottle  securely,  and  screwed  in  position  by  the  screw,  G. 
The  svutch  must  be  turned  on  so  as  to  give  the  machine  about  sixty  revolu- 
tions per  minute.  As  the  machine  revolves,  the  contents  of  the  bottle  fall 
from  the  bottom  to  the  top,  and  back  again,  about  once  a second. 


Fig.  118.  Shaking  Apparatus. 


At  the  close  of  the  shaking  period,  the  bottle  is  removed,  and  the  liquid 
poured  on  to  a dry  10  inch  filter.  It  filters  very  quickly  and  runs  through 
quite  bright.  If  364  c.c.  of  the  filtrate  be  taken,  that  quantity  is  equivalent 
to  2 grams  of  wet  gluten.  In  order  to  save  the  spirit,  the  filtrate  is  boiled 
down  in  a flask  connected  to  a condenser  until  the  whole  of  the  alcohol 
has  distilled  off.  For  this  purpose  the  flask  should  be  immersed  in  a hot 
bath  of  potassium  carbonate  solution  ; in  this  the  spirit  boils  rapidly,  and 
the  gliadin  does  not  stick  to  the  flask.  The  remainder  in  the  flask  is  then 
transferred  to  a weighed  glass  basin  and  evaporated  to  dryness.  The  neces- 
sary starch  correction  is  made  and  the  results  calculated  as  gliadin  ex  gluten. 
The  weight  of  residuum  thus  obtained  is  a very  convenient  one  (about  0-30 
to  0-35  gram),  but  lesser  quantities  may  be  taken  if  wished.  For  example, 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS. 


795 


I -I  gram  of  gluten,  5*5  grams  of  starch,  and  100  c.c.  of  alcohol  may  be  used 
for  each  test.  Then,  on  evaporation  of  91  c.c.  of  the  filtrate,  the  gliadin 
ex  1*0  gram  of  gluten  is  obtained. 

855.  Application  of  Gluten  and  Gliadin  Tests  to  Commercial  Flours. — 

In  order  to  illustrate  the  application  of  the  various  gluten  and  other  tests  to 
modern  flours,  the  authors  obtained  a range  of  commercial  samples  from 
Messrs.  W.  Vernon  & Sons,  Ltd.,  millers,  of  which  the  following  are  the 
names,  together  with  a description  of  the  working  properties  of  the  flours  as 
ascertained  by  baking  tests  : — 

1.  Millennium  gave  a loaf  of  rich  bloom  in  crust,  with  a delicate  creamy 
colour  in  crumb,  and  fine  silky  pile.  Loaf  was  of  fair  volume,  and  gives 
best  results  in  a hot  oven.  The  bread  keeps  moist,  and  is  of  exceedingly 
good  flavour. 

2.  To'p  price.  Slightly  lower  grade.  Good  bloom  on  crust,  texture 
and  colour  of  crumb  very  good.  Slightly  bolder  loaf,  of  good  flavour. 

3.  Town  whites.  Bright  colour  and  good  pile.  Flavour  good.  Flour 
worked  rather  stronger  than  those  preceding,  and  yielded  rather  larger  loaf. 

4.  C.C.C.  A good  flour  for  second  quality  bread  ; fair  all-round  pro- 

perties including  colour.  Strength  good,  without  harshness  in  resultant 
bread.  'd 

5.  Town  Households.  A darker  type  of  flour  ; makes  a good  loaf,  and 
suits  in  country  and  other  districts  where  high  colour  is  not  a desideratum. 

The  following  are  the  results  of  analysis 


Protein  and  other  Estimations  of  various  Commercial  Flours. 


Numbers — . 

1. 

2. 

3. 

4. 

5. 

Percentages  on  Flour. 

Wet  Gluten 

32-83 

34-36 

35-47 

34-67 

34-77 

Ratio  of  Wet  to  Dry  Gluten 

3-0 

3-0 

3-0 

3-1 

'3-0 

Dry  Gluten 

10-72 

1 1 -28 

11-72 

11-09 

11-56 

Non- Protein  Matter  in  Dry  Gluten 

2-19 

3-12 

3-39 

3-20 

3-26 

True  Gluten 

8-53 

1 8-16 

8-33 

7-89 

8-30 

Gliadin  ex  Gluten 

5-30 

5-45 

5-41 

5-41 

5-54 

Glutenin  ex  Gluten 

Percentages  on  Dry  Gluten. 

3-23 

2-71 

2-92 

2-48 

2-76 

Non-Protein  Matter  in  Dry  Gluten 

20-43 

27-66 

28-92 

29-76 

28-20 

Gliadin 

49-44 

! 48-31 

46-16 

48-78 

47-92 

Glutenin  . . 

Percentages  on  Flour. 

30-13 

24-03 

24-92 

21-46 

23-88 

Total  Proteins 

9-53 

: 9-80 

10-06 

9-71 

10-58 

Gliadin  ex  Flour  . . 

5-29 

5-20 

5-38 

5-25 

5-40 

Non-Gliadin  Proteins  (Glutenin,  Albumin,  etc.) 
Percentages  on  Total  Proteins. 

4-24 

4-60 

4-68 

4-46 

5-18 

Gliadin  ex  Flour 

55-51 

53-06 

53-48 

54-07 

51-04 

Non-Gliadin  Proteins 

44-49 

46-94 

46-52 

45-93 

48-96 

Recovered  as  True  Gluten 

89-51 

83-26 

82-80 

81-25 

78-45 

Not  recovered  as  True  Gluten  . . 

10-49 

16-74 

17-20 

18-75 

21-55 

Percentages  on  Flour. 

14-56 

14-52 

14-38 

14-40 

14-06  ! 

Moisture  . . 

0-38 

0-36 

0-42 

0-44 

0-52 

Ash 

Water  absorption,  Quarts  per  Sack 

60 

62 

62 

63 

1 

63 

i 

In  these  flours  the  total  gluten  increases  as  the  colour  goes  down,  and 
keeps  pace  with  their  strength,  but  in  true  gluten  No.  1 is  slightly  higher 
than  any  of  the  others.  The  gliadin  in  No.  1 is  rather  a higher  proportion  of 
the  dry  gluten  than  in  any  of  the  other  flours.  Looking  at  the  total  pro- 
teins as  determined  direct  on  the  flour  they  run  closely  parallel  to  the  dry 


796 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


glutens.  The  gliadins  as  obtained  from  the  flour  run  very  closely  to  each 
other,  being  highest  in  No.  1 and  lowest  in  No.  5.  The  percentage  of  proteins 
not  recovered  as  true  gluten  steadily  increases  as  the  flours  diminish  in 
quality.  It  would  seem  therefore  that  a comparison  of  the  total  proteins 
with  the  proportion  thereof  recoverable  as  true  gluten  has  a close  connection 
with  the  grade  of  the  flour.  The  ash  in  all  the  flours  is  low,  and  precludes 
the  possibility  of  mineral  additions  to  the  flour.  The  flours  likewise  gave 
no  reaction  when  tested  for  the  presence  of  bleaching  agents.  As  might 
be  expected  with  flours  from  the  one  mill,  there  is  a close  general  resemblance 
between  the  whole  of  the  grades. 

856.  Gluten  and  Gliadin  Tests  on  Special  Flours  and  Wheats. — The 

various  gluten  and  allied  tests  were  also  applied  to  a series  of  single  wheat 
flours,  and  typical  wheats,  with  the  following  results.  The  wheat  deter- 
minations were  made  on  the  finely  ground  meal  of  the  whole  grain,  but  in 
order  to  make  the  data  obtained  somewhat  more  comparable  with 
those  on  flours,  they  have  also  been  calculated  to  amounts  present  in  70  per 
cent,  straight-run  flours  from  such  wheats. 

Single  Wheat  Flours. 

6.  From  strong  spring  American  wheat. 

7.  ,,  French  wheat,  grovm  in  England,  1910  crop. 

8.  ,,  Karachi  wheat,  1910  crop. 

9.  ,,  Taganrog  wheat,  1909  crop. 

10.  ,,  Bar-russo  wheat,  1910  crop. 

11.  ,,  New  Russian  wheat,  1910  crop. 

12.  Fourteen  years  old  strong  American  flour. 


Protein  and  other  Estimations  on  Single  Wheat  Flours. 


' Numbers — . 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

Percentages  on  Flour. 

Wet  Gluten 

42-30 

29-90 

23-47 

25-73 

37-70 

32-90 

47-27 

Ratio  of  Wet  to  Dry  Gluten  . . 

2-8 

3-0 

3-4 

3-0 

3-3 

3-3 

1 5-1 

Dry  Gluten 

15-02 

9-75 

6-77 

8-52 

11-34 

9-98 

9-20 

1 Non-Protein  Matter  in  Dry  Gluten 

4-25 

1-95 

1-40 

0-90 

2-07 

1-63 

6-13 

True  Gluten 

10-77 

7-80 

5-37 

7-62 

9-27 

8-35 

3-07 

Gliadin  ex  Gluten 

7-36 

4-98 

3-75 

3-49 

6-91 

5-75 

2-84 

Glutenin  ex  Gluten 

3-41 

2-82 

1-62 

4-13 

2-36 

2-60 

0-23 

Percentages  on  Dry  Gluten. 
Xon-Protein  Matter  in  Dry  Gluten 

28-29 

20-00 

20-68 

10-56 

18-25 

16-33 

66-63 

Gliadin  . . 

49-00 

51-07 

55-38 

40-96 

60-93 

57-61 

30-87 

Glutenin  . . 

22-71 

28-93 

23-94 

48-48 

20-82 

26-06 

2-50 

Percentages  on  Flour. 

Total  Proteins  . . 

12-95 

10-19 

8-14 

13-78 

11-46 

12-12 

13-15 

Gliadin  ex  Flour 

6-43 

5-25 

3-82 

7-63 

5-64 

6-34 

5-75 

Xon-Gliadin  Proteins  . . 

6-52 

4-94 

4-32 

6-15 

5-82 

5-38 

7-40 

Percentages  on  Total  Proteins. 

Gliadin  ex  Flour 

49-65 

51-52 

46-93 

55-37 

49-21 

52-31 

43-72 

Xon-Gliadin  Proteins  . . 

50-35 

48-48 

53-07 

44-63 

50-79 

47-69 

56-28 

Recovered  as  True  Gluten 

83-16 

76-54 

65-97 

55-30 

80-89 

68-89 

23-34 

Xot  recovered  as  True  Gluten 

16-84 

23-46 

34-03 

44-70 

19-11 

31-11 

76-66 

iMoisture,  per  cent,  of  flour 



12-86 

12-14 

12-00 

12-70 

12-60 

12-46 

Water  Absorption,  Quarts  per  Sack' 

70 

67-0 

71-0  1 

69-5 

70-0 

1 

68-5 

— 

Wheats. 

13.  Old  Odessa,  1909  crop. 

14.  New  Odessa,  1910  crop. 

15.  Manitoba. 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  797 

16.  Northern  Plate  (Rosario  Santa  Ee). 

17.  American  Durum. 

18.  English  Rivetts. 

19.  “ Azima (Russian). 

20.  ‘‘Ulka’^  (Russian). 


Protein  and  other  Estimations  on  Typical  Wheats. 


X'umbere — . 

13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

Percentages  on  Meal. 

Wet  Gluten  . . 

33-27 

25-50 

.34-65 

35-70 

28-85 

18 -.50 

31-35 

40-50 

Ratio  of  Wet  to  Dry  Gluten 

3-0 

2-7 

2-9 

3-0 

^ 2-9 

3-0 

3-1 

3-1 

Dry  Gluten  . . 

10-96 

9-49 

11-88 

11-86 

10-00 

6-21 

10-07 

12-98 

Non-Protein  Matter  in  Dry 
Gluten 

1-96 

2-04 

2-54 

2-23 

2-40 

1-26 

1-94 

3-30 

True  Gluten . . 

9-00 

7-45 

9-34 

9-63 

7-60 

4-95 

8-13 

9-68 

Gliadin  ejc  Gluten  . . 

4-64 

3-68 

5-54 

5-73 

4-68 

2-81 

4-98 

6-07 

Glutenin  ex  Gluten  . . , 

4-36 

3-77 

3-80 

3-90 

2-92 

2-14 

3-15 

3-61 

Percentages  on  Dry  Gluten. 
Non-Protein  Matter  in  Dry 
Gluten  . . . . . . 

17-88 

21-49 

21-38 

18-80 

24-00 

20-29 

19-26 

25-42 

Gliadin 

42-33 

38-78 

46-63 

48-31 

46-80 

45-25 

49-45 

46-76 

Glutenin 

39-79 

39-73 

31-99 

.32-89 

29-20 

34-46 

31-29 

27-92 

Percentages  on  Meal. 

Total  Protein 

13-24 

12-11 

13-41 

13-73 

13-70 

8-81 

11-22 

13-86 

Gliadin  ex  Meal 

5-07 

4-11 

5-60 

5-99 

4-15 

2-97 

4-76 

5-38 

Non-Gliadin  Proteins 

8-17 

8-00 

7-81 

7-74 

! 9-65 

5-84 

6-46 

8-48 

Percentages  on  Total  Proteins. 
Gliadin  ex  Meal 

38-29 

33-94 

41-76 

43-63 

1 

j 30-29 

33-71 

42-42 

38-82 

Non-Gliadin  Proteins 

61-71 

66-06 

58-24 

56-37 

! 69-71 

66-29 

57-58 

61-18  1 

Recovered  as  True  Gluten 

67-97 

61-52 

69-65 

70-21 

1 55-47 

56-18 

72-46 

69-69 

Not  recovered  as  True  Gluten 

32-03 

38-48 

30-35 

29-79 

44-53 

43-82 

27-54 

30-31 

Calculated  on  70  per  cent. 
Straight  Flours. 

Wet  Gluten  , . 

47-53 

36-43 

49-50 

51-00 

41-21 

26-43 

45-00 

57-86 

Dry  Gluten  . . 

15-66 

13-56 

16-97 

16-94 

14-28 

8-87 

14-38 

18-54 

Non-Protein  Matter  in  Dry 
Gluten 

2-80 

2-91 

3-63 

3-18 

* 3-43 

1-80 

2-77 

4-71 

True  Gluten . . 

12-86 

10-64 

13-63 

1.3-76 

10-86 

7-07 

11-61 

13-83 

Gliadin  ex  Gluten  . . 

6-63 

5-26 

7-91 

8-18 

6-68 

4-01 

7-11 

8-67 

Glutenin  ex  Gluten 

6-23 

5-38 

5-72 

5-58 

4-18 

3-06 

4-50 

5-16 

On  examining  the  results  on  single  wheat  flours,  excluding  No.  12  for 
the  moment,  No.  6 gave  the  highest  percentage  of  wet  gluten,  while  Bar- 
russo,  No.  10,  was  the  next  highest.  The  spring  American  was  also  highest 
in  dry  gluten,  while  No.  8,  Karachi,  was  the  lowest.  In  this  particular  flour 
the  ratio  of  wet  to  dry  gluten  is  very  high  ; Wood’s  researches  (paragraphs 
455  et  seq.)  go  to  show  that  the  more  water  there  is  in  the  gluten  the  nearer 
it  is  to  actual  disintegration.  The  absolute  amount  of  gliadin  ex  gluten 
was  high  in  both  Nos.  6 and  10,  while  low  in  No.  8.  But  the  relative  pro- 
portion of  the  whole  dry  gluten  which  consisted  of  gliadin  was  comparatively 
liigh  in  No.  8.  Comparing  the  total  proteins  with  the  dry  gluten.  No.  9 was 
the  highest  in  the  former  and  almost  the  lowest  in  the  latter.  Taganrog, 
No.  9,  was  very  difficult  to  wash  for  gluten  ; there  was  considerable  frothing, 
and  the  wet  gluten  was  very  friable  throughout  the  whole  operation  of 
separation.  This  flour  is  from  a very  hard  wheat,  and  one  which  alone 
does  not  m.ake  a good  loaf.  The  gliadin  ex  gluten  content  was  very  low. 
On  the  other  hand  the  gliadin  ex  flour  was  high.  Taking  Nos.  6 and  9, 
protein  and  gliadin  determinations  on  the  flour  would  place  No.  9 the 
higher  ; but  gluten  and  gliadin  ex  gluten  estimations  at  once  show  the 
marked  superiority  of  the  spring  American  flour. 


798 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  12  sample,  called  “ Fourteen  Years  Old  Strong  American  Flour/’ 
is  of  rather  special  interest.  Rather  over  that  length  of  time  ago,  one  of 
the  authors  made  some  experiments  on  the  feasibility  of  compressing  flour 
into  solid  blocks  by  hydraulic  pressure  of  several  tons  to  the  square  inch. 
Among  flours  thus  tested  was  a sample  of  strong  American  flour,  of  which 
several  blocks  were  preserved.  These  were  quite  free  from  any  mould  or 
visible  signs  of  decomposition,  and  a portion  was  accordingly  subjected 
to  this  series  of  tests.  On  washing  for  gluten  the  dough  broke  down  into 
a flocculent  non-coherent  deposit,  and  evidently  was  physically  quite  un- 
fitted for  bread-making.  By  repeated  washings  on  a hair  sieve,  and  squeez- 
ing and  coaxing  the  particles  together,  a flabby  and  scarcely  coherent  mass 
of  wet  gluten  was  obtained,  which  gave  the  unusually  high  percentage  of 
47-27.  However  most  of  this  was  evidently  water,  the  ratio  being  5-1, 
and  the  total  quantity  of  dry  gluten  9-20  per  cent.  Pursuing  the  investi- 
gation of  the  dry  gluten  a step  further,  it  contained  only  3-07  per  cent,  of 
true  gluten,  6-13  per  cent,  consisting  of  non-separated  starch.  Nearly 
all  the  true  gluten  was  composed  of  gliadin,  the  whole  of  the  glutenin 
having  disappeared.  On  turning  to  the  direct  determinations  on  flour, 
the  proteins  are  high  and  are  very  nearly  the  same  as  in  the  strong 
American  flour.  No.  6 ; 13-15  against  12-95  per  cent.  The  gliadin  ex  flour 
is  very  nearly  as  much  as  that  of  No.  6,  5-75  against  6-43  per  cent.,  and 
would  in  ordinary  analysis  call  for  no  very  special  remark.  It  shows  up 
rather  more  in  percentages  on  total  proteins,  where  the  figure  is  43-72  against 
49-65  in  the  No.  6 flour.  But,  according  to  Snyder  (paragraph  448)  this 
difference  lies  almost  within  the  normal  range  since  the  same  type  of  flour 
may  have  variations  of  proteins  soluble  in  alcohol  from  45  to  as  high  as  70 
per  cent,  with  only  minor  variations  in  the  bread-making  value  of  the  flour. 
The  importance  of  these  comparisons  lies  in  the  fact  that  the  ordinary 
protein  and  gliadin  ex  flour  tests  scarcely  serve  to  differentiate  a spring 
American  flour  of  the  highest  quality  from  a flour  of  the  same  origin,  but  so 
profoundly  altered  by  fourteen  years  age  as  to  have  completely  lost  the 
physical  properties  so  essentially  characteristic  of  wheaten  flour.  On  the 
other  hand  the  abnormal  character  of  this  fourteen  year  old  flour  is  at  once 
revealed  by  an  ordinary  gluten  test,  and  is  in  evidence  throughout  the 
whole  series  of  subsidiary  tests  on  the  wet  gluten.  This  is  in  striking  con- 
trast with  Chamberlain’s  conclusion  (page  311)  that  “the  determination 
of  gluten  is  not  able  to  yield  any  information  that  cannot  be  gained  either 
from  the  determination  of  total  proteins  or  that  of  the  alcohol-soluble 
and  insoluble  proteins.”  It  is  submitted  that  if  what  may  be  called  the 
purely  chemical  tests  (Le.,  protein  and  gliadin  determinations  on  the  flour 
direct)  fail  so  signally  to  indicate  such  remarkable  differences  as  there  are 
between  these  two  flours,  then  they  can  be  even  less  depended  on  as  a 
means  of  gauging  and  estimating  minor  differences  in  character  and  quality. 
The  gluten  tests  and  their  developments,  on  the  contrary,  afford  exceed- 
ingly valuable  information  as  to  the  general  baking  properties  of  the  flour. 

Tlie  wheats  range  from  the  strongest  Manitoban  to  one  of  the  weakest  of 
English  wheats,  Rivetts.  The  first  pair.  Nos.  13  and  14,  consist  of  Odessa 
of  two  successive  years’  crops.  The  old  was  very  satisfactory,  but  the 
new  wheat  was  the  reverse.  The  former  was  higher  in  wet,  dry,  and  true 
gluten.  Also  the  relative  proportion  of  gliadin  ex  gluten  was  higher  in  the 
older  wheat.  The  total  proteins  and  gliadin  ex  meal  were  in  general  accord- 
ance with  the  gluten  series  of  tests.  The  calculated  percentages  on  70 
i:)er  cent,  straight  flours  are  introduced  with  the  object  of  showing  approxi- 
mately the  composition  of  the  flours  from  the  wheats,  and  permitting  same 
to  be  compared  with  other  flours.  The  Manitoba  wheat.  No.  15,  is  high  in 
wet  and  dry  gluten,  and  also  in  true  gluten.  The  gliadin  is  high  both  abso- 


SOLUBLE  EXTRACT,  ACIDITY,  AND  PROTEINS.  799 

lately,  5*54  per  cent.,  and  relatively,  46-63  per  cent.,  of  the  dry  gluten. 
On  the  meal,  the  total  proteins,  13-41,  and  gliadin,  5-60  per  cent.,  are  also 
high.  Throughout  the  whole  series  of  tests  the  Rosario  Santa  Ee  very 
closely  resembles  Manitoba  wheats.  (The  American  Durum,  No.  17,  refuses 
to  come  into  line  with  any  of  the  others.  The  wet  and  dry  glutens  are  low, 
so  also  is  the  true  gluten,  7-60  per  cent.  But  the  gliadin  ex  gluten  is  rela- 
tively high,  being  46-80  per  cent,  of  the  dry  gluten.  Gluten  testing  would 
reveal  the  fact  that  this  wheat  was  extremely  hard  ; and  this,  coupled 
with  the  low  gluten,  would  indicate  thorough  conditioning  of  same  before 
grinding.  The  total  proteins  of  this  wheat  are  high,  13-70.,  while  the  pro- 
portion recovered  as  true  gluten  was  low,  being  only  55-47  per  cent.  The 
gliadin  ex  meal  is  very  low.  ^The  extreme  hardness  of  the  grain  very  materi- 
ally affects  all  estimations  made  by  solvents  direct  on  the  meal,  and  there- 
fore gluten  and  gliadin  ex  meal  are  both  abnormally  low.  If  the  wheat  be 
softened  by  standing  some  time  after  the  addition  of  water,  these  soluble  con- 
stituents would  show  an  increase.  Similarly,  the  great  hardness  of  the  wheat 
would  react  adversely  on  the  flour  if  untreated,  whereas  effective  condition- 
ing would  very  materially  improve  the  flour.  The  English  Rivetts,  No.  18, 
is  almost  the  antithesis  of  the  preceding  flour.  Its  gluten  throughout  is 
low,  18-50  per  cent,  wet,  but  contains  a fairly  high  proportion  of  gliadin, 

45- 25  per  cent.  The  total  proteins  agree,  being  so  low  as  8-81  per  cent., 
while  the  gliadin  ex  meal  is  do\m  to  33-71  per  cent,  of  the  total  proteins. 
The  Azima,  No.  19,  has  a fair  gluten,  with  a relatively  high  percentage  of 
gliadin  ex  gluten.  The  total  proteins  occupy  a medium  position,  wdiile 
the  gliadin  ex  meal  is  also  fairly  high.  The  Ulka  wheat.  No.  20,  is  distin- 
guished by  a very  high  percentage  of  wet  gluten,  of  a soft  and  what  is  some- 
times called  “ pappy  character.  The  ratio  of  w^et  to  dry  gluten  is  high, 
3-1,  but  the  dry  gluten  is  nevertheless  the  highest  of  the  series,  12-98  per 
cent.  The  true  gluten,  9-68,  is  also  the  highest  of  those  in  the  table.  The 
gliadin  ex  gluten  is  high  absolutely,  6-07,  and  medium  relatively,  being 

46- 76  per  cent,  of  the  dry  gluten.  In  total  proteins  this  wLeat  is  also  the 
highest  of  the  series  wdth  13-86  per  cent.,  wLile  relatively  the  gliadin  ex 
meal  is  rather  above  the  average  wdth  38-82  per  cent. 

857.  Amide  Nitrogen. — ^A  method  for  the  determination  of  amides  in 
flour  is  described  by  Guess,  and  is  given  in  paragraph  442. 

858.  Detection  of  Proteolytic  Enzymes  in  Flour. — A process  for  the 
detection  of  protease,  or  proteolytic  enzymes  in  flour,  has  been  described 
by  Ford  and  Guthrie,  and  is  quoted  in  paragraph  461,  page  326. 


CHAPTER  XXIX. 


ESTIMATION  OF  CARBOHYDRATES,  AND  ANALYSIS  OF  BODIES  CON- 
TAINING SAME. 

859.  Estimation  of  Sugar  by  Fehling’s  Solution. — ^The  composition  and 
properties  of  the  sugars  are  fully  described  in  Chapter  VI.  It  is  there 
shown  that  maltose  is  capable  of  forming  a red  precipitate  of  copper  sub -oxide 
in  the  reagent  termed  Fehling’s  solution,  while  dextrin  and  starch  cause  no 
precipitate.  (See,  however,  Brown  and  Millar’s  conclusion  that  dextrin 
has  a reducing  power  of  about  R.  5-8,  paragraphs  179,  and  262,  page 
133.)  This  reaction  is  not  only  of  service  in  testing  for  maltose  and  certain 
other  sugars,  but  also  serves  the  purpose  of  quantitatively  determining 
the  amount  of  sugar  present  in  a solution. 

As  before,  directions  are  first  given  for  the  preparation  of  the  reagents, 
and  then  for  the  performance  of  the  analytic  operation. 

860.  Fehling’s  Standard  Copper  Solution. — ^Powder  a sufficient  quantity 
of  pure  re-crystallised  copper  sulphate,  and  dry  it  by  pressure  between  folds 
of  filter  paper.  Weigh  out  69*28  grams,  dissolve  in  water,  add  I c.c.  of 
pure  sul^Dhuric  acid,  and  make  up  the  solution  to  I litre. 

861.  Alkaline  Tartrate  Solution. — ^Weigh  out  350  grams  of  pure  Rochelle 
Salt  (potassium  sodium  tartrate),  and  dissolve  so  as  to  make  about  700  c.c. 
of  solution.  Filter  if  necessary.  Next  dissolve  100  grams  of  sticks  of 
pure  caustic  soda  in  200  c.c.  of  water.  If  the  solution  is  not  clear,  it  must 
be  filtered  through  a funnel  fitted  with  a plug  of  glass  wool.  Mix  the  two 
solutions  together,  and  make  up  the  volume  to  1 litre. 

When  required  for  use,  these  solutions  must  be  mixed  together  in  equal 
proportions  ; they  then  form  the  original  Fehling’s  solution.  This  solu- 
tion possessed  the  disadvantage  of  changing  in  character  by  being  kept  ; 
and  hence  the  modification  in  which  the  Rochelle  salt  is  only  added  to  the 
copper  sulphate  immediately  before  the  solution  is  required  for  use.  Each 
c.c.  of  the  mixed  solution  contains  0*03464  grams  of  copper  sulphate,  and 
was  formerly  considered  equivalent  to  exactly  0*005  grams  of  pure  dry 
glucose. 

862.  Action  of  Sugars  on  Fehling’s  Solution. — ^A  careful  investigation 
has  been  made  by  Soxhlett  of  the  action  on  Fehling’s  solution  of  specially 
pure  specimens  of  the  various  types  of  sugars  : he  finds  as  a result  that  the 
amount  of  precipitate  formed  depends  not  only  on  the  quantity  of  sugar 
present,  but  also  on  the  degree  of  concentration  of  the  solution,  the  tem- 
perature at  which  the  determination  is  made,  and  other  conditions.  Hence 
great  care  must  be  taken  to  work  always  in  precisely  the  same  manner,  as 
it  is  only  by  so  doing  that  comparative  results  are  obtained. 

Sugar  may  be  determined  by  Fehling’s  solution  either  gravimetrically 
or  volu metrically.  A description  of  the  gravimetric  method  is  first  given. 
The  student  should  commence  by  practising  the  estimation  on  cane  sugar, 
as  this  substance  is  easily  obtained  in  a condition  of  purity.  Cane  sugar 
has  no  action  on  Fehling’s  solution,  but  when  heated  gently  with  dilute 

800 


ESTIMATION  OF  CARBOHYDRATES.  801 

acid  is  changed,  by  hydrolysis,  into  a mixture  of  glucose  and  fructose  in 
equal  quantities,  viz.  : — 

C12H22OH  -f“  H2O  = C6H12O6  “h  C6H12O6. 

Cane  Sugar.  Water.  Glucose.  Fructose. 

Glucose  and  fructose  both  act  on  Fehling’s  solution,  precipitating  copper 
sub-oxide,  CU2O,  in  definite  quantity. 

[ 863.  Gravimetric  Method  on  Cane  Sugar. — ^Procure  some  of  the  sugar 
known  as  coffee  crystals  ; this  is  the  variety  of  sugar  sold  by  the  grocer  for 
use  with  coffee,  and  consists  of  large,  colourless,  well-defined  crystals  of 
almost  pure  cane  sugar.  Select  some  of  these  free  from  extraneous  matter, 
powder  them,  and  dry  for  a short  time  in  the  hot- water  oven.  Make  up  a 
one  per  cent,  solution  by  weighing  out  I gram  of  the  pure  dry  sugar,  dis- 
solving it  in  water,  and  making  up  the  volume  to  100  c.c.  Take  50  c.c.  of 
this  solution,  and  add  to  it  5 c.c.  of  pure  fuming  hydrochloric  acid.  For 
this  purpose  it  is  best  to  use  a fiask  graduated  at  50  and  55  c.c.  Place  the 
fiask  in  a water  bath,  and  heat  until  it  reaches  the  temperature  of  68°  C.  ; 
this  operation  should  be  arranged  so  as  to  occupy  about  10  minutes.  Next 
pour  the  contents  of  the  flask  into  a 100  c.c.  flask,  and  dissolve  in  it  dry 
sodium  hydroxide  in  small  quantities  at  a time  until  the  solution  is  slightly 
alkaline,  testing  after  each  addition  with  a small  strip  of  litmus  paper. 
Cool  the  flask  and  make  up  the  contents  to  100  c.c.  with  w^ater.  The  flask 
now  contains  a 0-5  per  cent,  alkaline  solution  of  cane  sugar  converted  into 
glucose  and  fructose.  Add  25  c.c.  of  Fehling’s  standard  copper  solution 
to  the  same  quantity  of  alkaline  tartrate  solution,  and  mix  the  two  thor- 
oughly. Take  two  beakers  of  about  6 ounces  capacity,  and  pour  into  each 
25  c.c.  of  the  mixed  Fehling’s  solution.  Next  add  to  each  50  c.c.  of  boiling 
distilled  water  that  has  been  boiling  for  about  haff  an  hour.  Stand  the 
beakers  in  a water  bath,  the  water  of  which  is  kept  boiling  by  a bunsen  ; 
allow  them  to  stand  for  7 minutes,  and  then  look  to  see  that  no  pre- 
cipitate has  formed.  Should  a precipitate  occur,  the  Fehling’s  solution  is 
impure,  and  is  consequently  no  longer  fit  for  use.  Next  add  to  each  beaker 
20  c.c.  of  the  0*5  per  cent,  sugar  solution  and  replace  in  the  water  bath  for 
12  minutes.  The  precipitated  cuprous  oxide  is  best  weighed  on  a counter- 
poised filter  ; prepare,  therefore,  beforehand,  two  pairs  of  small  Swedish 
filters,  trimmed  until  each  one  of  the  pair  exactly  counterpoises  the  other, 
when  tested  in  the  analytic  balance.  Fold  one  of  the  pair  of  counterpoised 
filters,  and  filter  the  copper  oxide  rapidly  from  the  solution  ; the  filtrate 
should  still  be  of  a deep  blue  colour.  Collect  the  filtrate  in  a porcelain 
evaporating  basin,  and  examine  carefully  in  order  to  see  if  any  traces  of 
the  precipitate  have  found  their  way  through  the  paper  ; if  so,  pour  away 
the  supernatant  liquid  from  the  basin,  and  wash  any  precipitate  back  on 
to  the  filter.  Moisten  the  other  of  the  pair  of  counterpoised  filters  with 
some  of  the  filtrate,  and  wash  both  the  filters  rapidly  with  boiling  water, 
and  dry  both  in  the  hot-water  oven.  Tlie  reason  for  treating  the  second 
paper  with  some  of  the  filtrate  is  to  cause  each  to  be  in  as  nearly  as  possible 
the  same  condition,  so  that  it  (the  second)  shall  still  counterpoise  the  first 
paper  after  being  washed  and  dried.  The  filters  should  be  dried  for  12 
hours  and  then  weighed,  the  counterpoise  paper  being  placed  on  the  weight 
side. 

If  wished,  the  cuprous  oxide  may  be  converted  into  cupric  oxide  and 
weighed  as  such.  Or  the  oxide  may  be  reduced  to  copper,  either  by  the 
action  of  hydrogen  or  by  electrolytic  processes,  and  weighed  in  the  metallic, 
form.  For  these  and  other  methods,  consult  Allen’s  Commercial  Organic 
Analysis,  vol.  i. 

In  order  to  understand  the  calculations  involved  in  the  estimation  of 

3f 


802 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


sugar  by  Eehling’s  solutions,  it  will  be  necessary  for  the  student  to  make 
himself  thoroughly  acquainted  with  the  properties  of  the  sugars  as  already 
described. 

The  glucose  and  fructose  produced  by  the  action  of  dilute  acid  on  cane 
sugar,  as  shown  in  the  equation  in  a preceding  paragraph,  are  sometimes 
grouped  together  as  glucose,  or  grape  sugar  ; it  is  then  said  that  one  molecule 
of  cane  sugar  (sucrose)  produces,  when  inverted,  two  molecules  of  glucose. 
From  the  equation  it  will  be  seen  that  the  molecular  weight  of  cane  sugar 
is  342,  while  that  of  the  glucose  formed  is  360.  It  was  formerly  supposed 
that  an  exact  number  of  molecules  of  CuO  of  the  copper  sulphate  was  re- 
duced to  CU2O  by  the  sugar  ; hence  we  find  the  statement  that  two  mole- 
cules of  glucose  reduce  10  CuO  to  5 CU2O.  Soxhlett’s  researches,  however, 
show  that  the  reaction  is  not  so  simple,  but,  as  before  stated,  varies,  being 
dependent  on  the  degree  of  the  dilution  of  the  reagent  and  other  conditions. 
Different  kinds  of  sugar,  too,  under  the  same  conditions,  reduce,  weight 
for  weight,  different  quantities  of  CuO  to  CU2O.  Working  in  the  manner 
directed,  the  reducing  power  of  sugar  on  Eehling’s  solution  is,  according  to 
determinations  by  O’Sullivan  and  others  ; — 


Cane  Sugar  has  no  reducing  action.  1 gram  produces and  reduces. 

Glucose  . . . . . . . . 1*983  grams  of  CuaO  2*205  of  CuO. 

Cane  Sugar  after  inversion  . . 2*087  ,,  ,,  2*315  ,, 

Maltose  . . . . . . . . 1*238  ,,  ,,  1*378  ,, 


The  reason  why  the  inverted  cane  sugar  produces  more  CU2O,  than 
does  glucose  is,  that  1 gram  of  cane  sugar,  on  inversion,  yields  more  than  a 
gram  of  glucose,  the  exact  quantity  being  1-052  grams.  When  only  the 
one  variety  of  sugar  is  present  in  a solution,  the  following  factors  may  be 
used  for  calculating  the  amount  of  sugar  from  the  weight  of  precipitated 
CU2O. 

Glucose  . . . . . . . . . . . . y.-Jsa  =0*5042 

Cane  Sugar  after  inversion  ..  ..  ..  2-^X7=0*4791 

Maltose  . . . . . . . . . . . . 8=0*8077 

Thus,  suppose  that  in  the  analysis  made  with  the  0-5  per  cent,  solution, 
the  weight  of  the  precipitated  CU2O  was  0-2075  grams,  then  ' 

0-2075  X 0-4791  = 0-0994  of  cane  sugar. 

Theoretically,  in  20  c.c.  of  the  0-5  per  cent,  solution  there  is  0-1  gram  of 
sugar  ; the  results  of  the  analysis  give  99-43  per  cent,  of  chemically  pure 
sugar.  If  the  estimation  were  made  with  perfect  accuracy,  this  would 
show  that  the  sugar  contained  0-57  per  cent,  of  moisture  or  other  impurity  ; 
the  deficiency  is  doubtless  in  part  due  to  error  of  analysis.  The  duplicate 
estimations  made  should  agree  closely. 

When  making  an  analysis  of  a substance,  the  composition  of  which  is 
known  approximately,  a quantity  should  be  taken  that  contains  as  nearly 
as  can  be  calculated  0-1  gram  of  inverted  cane  sugar,  or  0-2  gram  of  maltose. 
In  case  the  estimation  shows  that  the  amount  of  sugar  differs  widely  from 
these  quantities,  a second  determination  must  be  made  in  which  more  or 
less  of  the  substance  is  taken. 

In  the  presence  of  other  carbohydrates  capable  of  inversion  by  liydro- 
chloric  acid,  O’Sullivan  recommends  that  cane  sugar  be  inverted  by  means 
of  invertase,  which  is  without  action  on  the  other  sugars,  etc.,  which  may 
j^ossibly  be  present.  The  method  is  described  in  detail  in  connection  with 
the  analysis  of  malt  extract. 

864.  Volumetric  Method  on  Cane  Sugar. — ^When  Fehling’s  solution  is 
intended  only  to  be  used  gravimetrically,  its  exact  strength  is  not  a matter 


ESTIMATION  OF  CARBOHYDRATES. 


803 


of  great  importance,  but  when  employed  for  volumetric  estimations,  its 
strength  must  first  be  accurately  determined  by  titration  with  a standard 
solution  of  sugar.  For  this  purpose  the  0-5  per  cent,  solution  of  inverted 
cane  sugar  already  described  may  be  used.  The  sugar  must  be  added  to 
the  Fehling’s  solution,  and  not  the  Fehling’s  solution  to  the  sugar.  The 
sugar  solution  is  therefore  placed  in  a burette,  and  in  order  that  its  contents 
may  not  get  heated  during  the  operation,  the  glass  jet  is  attached  by  means 
of  a piece  of  india-rubber  tubing  about  8 or  10  inches  long.  The  burette 
may  then  be  placed  so  as  not  to  be  vertically  over  the  basin  in  which  the 
Fehling’s  solution  is  being  heated. 

Measure  out  5 c.c.  each  of  the  standard  copper  and  alkaline  tartrate 
solutions  into  a white  porcelain  evaporating  basin  ; add  40  c.c.  of  well- 
boiled  boiling  water,  and  heat  the  liquid  quickly  to  the  boiling  point  by 
means  of  a small  bunsen  flame.  In  order  to  test  the  purity  of  the  Fehling’s 
solution,  boil  for  2 minutes  ; there  should  neither  be  a precipitate  nor 
any  alteration  of  colour.  Next  add  the  sugar  solution  in  small  quantities 
at  a time,  boiling  between  each  addition.  As  the  operation  proceeds,  the 
deep  blue  colour  of  the  solution  disappears  ; towards  the  end,  add  the 
sugar  rnore  cautiously,  and  after  each  boiling  allow  the  precipitate  to  sub- 
side. Tilt  the  dish  slightly  over,  note  whether  the  clear  supernatant  liquid 
is  still  of  a blue  tint  by  observing  the  white  sides  of  the  dish  through  it. 
When  the  colour  has  entirely  disappeared,  the  reaction  is  complete.  The 
exact  point  may  be  determined  with  more  exactitude  by  means  of  a dilute 
solution  of  potassium  ferrocyanide,  acidulated  Avith  acetic  acid.  With  a 
glass  rod  put  a series  of  drops  of  this  reagent  on  a white  porcelain  tile  ; 
wash  the  rod,  take  out  a drop  of  the  clear  liquid  from  the  dish  with  it,  and 
add  it  to  one  of  the  drops  of  the  ferrocyanide  ; the  slightest  trace  of  copper 
produces  a reddish-brown  colouration. 

The  results  of  the  first  estimation  must  only  be  looked  on  as  approxi- 
mate, but  having  thus  gained  an  idea  of  about  how  much  sugar  is  required, 
the  succeeding  ones  may  be  made  more  quickly,  as  almost  all  the  sugar 
may  be  added  at  one  time.  Thus,  if  9-6  c.c.  of  sugar  solution  Avere  required 
in  the  first  trial,  then  in  the  second  from  8-5  to  9-0  c.c.  may  be  run  in  at 
once,  and  then  the  solution  added  more  carefully  as  the  end  of  the  reaction 
is  reached. 

Provided  the  Fehling’s  solution  is  of  normal  strength,  then 
10  c.c.  = 0-0500  grams  of  glucose  or  invert  sugar. 

10  c.c.  = 0-0475  ,,  ,,  cane  sugar  (after  inversion). 

10  c.c.  = 0-0801  ,,  ,,  maltose. 

The  difference  betAA^een  the  cane  sugar  and  glucose  is  here  again  ex- 

plained by  the  fact  that  cane  sugar  produces  on  inversion  more  than  its 
AA'eight  of  glucose  ; 0-0475  gram  of  cane  sugar  yields  0-05  gram  of  glucose. 
Working  with  a 0-5  per  cent,  solution  of  cane  sugar,  each  c.c.  contains 
0-005  gram,  and  9-5  c.c.  contain  0-0475  gram  of  sugar  ; 10  c.c.  of  the  Feh- 
ling’s solution  should  therefore  require  for  its  complete  reduction  9-5 c.c.  of 
the  sugar  solution. 

As  the  Fehling’s  solution  is  rarely  of  the  exact  strength,  its  equivalent 
in  cane  sugar  must  be  noted  so  as  to  be  used  in  each  determination.  Sup- 
pose the  10  c.c.  of  Fehling’s  solution  required  9-3  c.c.  of  the  sugar  solution, 
then  AA^e  knoAV  that  10  c.c.  is  equivalent  to  only  ff  = 0-9789  of  the  re- 
spective quantities  of  different  sugars  given  above.  The  exact  strength  of 
the  Fehling’s  solution  should  be  noted  on  the  bottle,  together  AAuth  the  date 
AA'hen  the  titration  Aras  made  ; the  solution  should  be  frequently  tested 
against  the  solution  of  pure  sugar.  The  quantity  of  sugar  found  must 
therefore  be  multiplied  by  0-9789.  An  example  AAill  make  this  clear.  A 


804 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

0-5  per  cent,  solution  of  a commercial  sugar  was  tested  volu metrically, 
when  11-4  c.c.  of  the  sugar  solution  were  required  to  completely  reduce 
10  c.c.  of  the  Fehling’s  solution.  By  titration  10  c.c.  of  the  Fehling’s  solu- 
tion are  known  to  be  equivalent  to  0-9789  of  0-0475  = 0-0465  of  pure  cane 
sugar  ; that  quantity  is  therefore  present  in  11-4  c.c.  of  the  0-5  per  cent, 
solution.  A 0-5  per  cent,  solution  contains  0-005  gram  of  sugar,  so  that 

11- 4  c.c.  contains  0-0570  gram  of  the  sugar.  As  0-0570  gram  of  the  sample 
contains  0-0465  gram  of  sugar,  the  percentage  of  pure  sugar  in  the  speci- 
men is  81-58.  The  analysis  would  appear  in  the  note-book  thus  : 

Volumetric  determination  of  pure  sugar  in  a commercial  sample  of 
cane  sugar. 

Inverted  and  made  up  to  0-5  per  cent,  solution. 

11-4  c.c.  required  to  reduce  10  c.c.  of  Fehling's  solution, 
which  = 0-0465  gram  of  pure  cane  sugar. 

0-0465x100 

11*4  xO  005  ^ cent,  of  pure  sugar.'’ 

865.  Estimation  of  Maltose  in  Wheats  or  Flours. — The  method  of  pro- 
cedure is  much  the  same  as  with  cane  sugar.  The  principal  point  is  to  obtain 
a solution  of  the  right  strength.  Assuming  that  an  aqueous  infusion  of 
wheat  contains  an  average  amount  of  2-5  per  cent,  of  maltose,  then  100  c.c. 
of  a 10  per  cent,  solution  of  the  meal  or  flour  contains  0-25  gram  of  maltose, 
so  that  80  c.c.  of  the  10  per  cent,  solution  are  required  in  order  to  furnish 
an  approximate  amount  of  0-2  gram  of  maltose.  For  each  quantitative 
estimation,  take  25  c.c.  of  Fehling's  solution,  10  c.c.  of  Avater,  and  80  c.c. 
of  the  clear  10  per  cent,  solution  of  the  meal  or  flour.  These  quantities  give 
the  same  degree  of  dilution  as  those  directed  to  be  used  in  the  estimation  of 
cane  sugar  ; proceed  exactly  as  in  the  determination  of  that  substance. 
Having  weighed  the  precipitate  of  CU2O,  multiply  by  the  factor  0-8077  ; 
the  result  is  the  quantity  of  maltose  in  80  c.c.  of  a 10  per  cent,  solution  of 
the  meal  or  flour.  As  80  c.c.  of  such  a solution  contains  the  soluble  portion 
of  8 grams  of  the  meal,  the  percentage  is  obtained  by  multiplying  by 

12- 5. 

In  making  this  estimation  the  soluble  proteins  of  the  grain  are  kept  in 
solution  by  the  alkali  of  the  Fehling’o  solution.  They  may  if  wished  be 
removed  by  boiling  and  Altering  the  10  per  cent,  solution.  Put  about 
100  c.c.  of  the  solution  in  a beaker,  take  the  weight,  and  then  boil  for  about 
five  minutes  ; replace  on  the  balance  and  make  up  to  the  original  weight 
with  distilled  water.  Filter  off  the  coagulated  proteins  by  passing  the 
liquid  through  a dry  filter  ; the  filtrate  is  a 10  per  cent,  solution,  minus 
the  proteins  coagulated  by  boiling. 

If  maltose  is  to  be  determined  volumetrically,  the  solution  should  always 
be  first  freed  from  coagulable  proteins  in  the  manner  just  described.  Take 
10  c.c.  of  the  mixed  Fehling’s  solution,  add  20  c.c.  of  Avater,  and  run  in  the 
clear  10  per  cent,  solution  of  the  meal  or  flour  until  the  reaction  is  complete, 
exactly  as  Avas  done  AAuth  the  inverted  cane  sugar.  The  less  quantity  of 
Avater  is  added  because  of  the  maltose  solution  from  the  meal  or  flour  being 
so  A^ery  dilute. 

In  case  the  estimation  of  maltose  is  being  made  in  a much  stronger 
solution  than  that  obtained  by  treating  a meal  AA'ith  10  times  its  AA'eight 
of  AA'ater,  dilute  the  solution  doA\m  until  it  contains  approximately  about 
one  per  cent,  of  maltose,  and  then  AV'ork  AA'ith  exactly  the  same  quantities 
as  Avere  directed  for  the  inverted  cane  sugar  0-5  per  cent,  solution. 

The  estimation  of  maltose  in  AA'heats  and  flours  is  principally  of  value 
as  a means  of  judging  the  amount  of  alteration  AA'hich  the  starch  has  under- 
gone : that  a sugar  analagous  to  cane  sugar  is  also  present  is  demonstrated 


ESTIMATION  OE  CARBOHYDRATES. 


805 


by  the  experiment  quoted  in  paragraph  370,  page  £08,  in  which  an  addi- 
tional precipitate  is  obtained  as  a result  of  treatment  with  hydrochloric  acid. 
It  must  be  remembered  that  with  such  an  aqueous  infusion  there  is  always 
some  change  due  to  enzymic  action  on  the  starch  of  the  wheat.  If  neces- 
sary, this  action  is  obviated  by  destruction  of  the  enzymes  as  a preliminary 
to  the  test.  (See  paragraph  461,  page  326.) 

866.  Estimation  of  Dextrin. — ^Most  substances  which  contain  maltose 
contain  also  dextrin  ; thus  the  two  are  both  found  in  wort  produced  from  malt, 
and  also  in  starch  solutions  that  have  been  subjected  to  diastasis.  Dextrin 
has  no  action  (or  but  little)  on  Fehling’s  solution,  but  by  prolonged  treatment 
with  an  acid  is  converted  into  maltose,  and  ultimately  into  glucose.  When 
maltose  and  dextrin  are  simultaneously  present  in  a liquid,  other  carbo- 
hydrates being  absent,  the  maltose  is  estimated  in  a portion  as  already 
described  ; another  portion  is  treated  with  acid,  by  which  both  dextrin 
and  maltose  are  converted  into  glucose.  A second  estimation  of  the  copper 
oxide  reducing  power  is  then  made.  The  weight  of  precipitate  will  be  found 
to  be  considerably  more  than  in  the  first  estimation.  This  is  due,  in  the 
first  place,  to  the  fact  that  glucose  precipitates  more  CU2O  than  does  maltose. 
The  maltose  originally  present  must  be  calculated  into  glucose,  and  the 
amount  of  precipitate  due  to  it  subtracted  from  the  weight  found  in  the 
second  estimation  : the  remainder  is  reckoned  as  glucose  produced  by  the 
hydrolysis  of  the  dextrin  ; the  percentage  may  be  then  obtained  by  calcu- 
lation. Unfortunately,  it  is  difficult  to  determine  the  exact  point  when 
the  whole  of  the  dextrin  has  been  changed  into  glucose.  When  carefully 
worked  the  process  is,  however,  sufficiently  accurate  for  most  technical 
purposes,  and  yields  comparative  results.  The  method  is  largely  employed 
for  the  determination  of  dextrin  in  the  worts  made  for  malt  essays.  There 
follows  a modification  of  the  process  adapted  to  the  determination  of  dextrin 
in  meals  and  flours.  Having  made  a solution  for  the  determination  of 
maltose,  take  the  same  quantity  of  the  solution  as  required  for  that  estima- 
tion, viz.,  80  C.C.,  and  add  to  it  2 c.c.  of  dilute  sulphuric  acid  (1  part  concen- 
trated acid  to  8 of  water),  stand  the  mixture  in  a water  bath,  and  heat 
to  boiling  for  4 hours.  At  the  end  of  that  time  neutralise  carefully  with 
■caustic  potash  solution  (KHO),  and  proceed  to  estimate  glucose  by  Feh- 
ling’s  solution  precisely  as  before.  The  excess  of  glucose  in  the  second 
solution  over  that  produced  by  the  maltose  in  the  first  requires  to  be  calcu- 
lated back  to  dextrin.  It  must  be  remembered  that  glucose  is  produced 
from  dextrin  according  to  the  following  equation  ; — 

Ci2H2oOio  2H2O  = 2C6H12O0 

Dextrin.  Water.  Glucose. 

Molecular  weight =324.  Molecular  weight =360. 

Tlierefore,  every  360  parts  of  glucose  thus  produced  represent  324  parts 
of  dextrin  in  the  original  solution,  or  10  of  glucose  = 9 parts  of  dextrin, 
so  that  glucose  formed  from  dextrin  X y^o  = dextrin.  As  already  stated, 
this  method  must  only  be  looked  on  as  giving  results  sufficiently  accurate 
for  technical  purposes. 

A useful  alternative  method  of  estimating  dextrin  depends  on  the  fact 
that  it  is  only  very  slightly  soluble  in  alcohol  of  the  strength  of  ordinary 
methylated  spirits,  whereas  maltose,  glucose,  etc.,  are  fairly  soluble  under 
the  same  conditions.  The  method  is  applicable  to  the  soluble  extracts  of 
bread  and  flour,  malt  extracts,  and  similar  preparations.  When  there  are 
many  such  estimations  to  be  made,  a fairly  large  quantity  of  methylated 
.spirits,  say  a gallon,  should  be  redistilled  (see  paragraph  878),  tested  against 
purified  dextrin,  and  reserved  for  this  purpose.  To  purify  dextrin,  take  some 


806 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


of  the  best  light -coloured  dextrin  of  commerce,  and  dissolve  in  water  to 
about  a 15  per  cent,  solution.  Pour  some  of  this,  in  small  quantities  at  a 
time,  in  about  a litre  of  redistilled  spirit  in  a large  flask,  shaking  vigorously 
between  each  addition.  Dextrin  will  be  precipitated,  and  should  be  finely 
divided,  if  in  sticky  clots  the  solution  has  been  used  too  strong,  and  must 
be  diluted.  Filter  off  this  precipitate,  wash  with  alcohol,  redissolve  in  water, 
and  again  precipitate  with  a large  quantity  of  alcohol  as  before.  Wash 
and  carefully  dry  ; the  resultant  purified  dextiin  should  be  colourless  and 
tasteless  (save  for  a slight  flavour  from  the  spirit).  Dissolve  OT  gram  of 
the  dextrin,  and  make  up  to  10  c.c.  in  water  ; add  this  quantity  to  125  c.c. 
of  the  redistilled  spirit,  and  shake  well  : there  should  be  a slight  precipitate. 
Filter  and  evaporate  50  c.c.  to  dryness  in  a weighed  dish,  and  thus  deter- 
mine the  amount  of  dextrin  dissolved  by  the  particular  sample  of  spirit. 
Note  same  in  calculated  weight  of  dextrin  held  in  solution  per  270  c.c. 

In  making  a determination,  prepare,  if  possible,  a solution  of  such  a 
strength  that  20  c.c.  shall  contain  approximately  0-2  gram  of  dextrin.  Add 
this  to  250  c.c.  of  redistilled  spirit  in  a flask,  cork,  and  shake  up  : allow 
to  stand  a few  hours,  then  pour  off  the  clear,  supernatant  liquid  on  to  a 
counterpoised  filter,  disturbing  the  precipitate  as  little  as  possible.  Add 
100  c.c.  more  of  redistilled  spirit  to  the  precipitate,  and  shake  vigorously, 
then  transfer  the  dextrin  to  the  filter,  washing  out  the  paper  with  the  clear 
spirit  filtrate  ; dry  and  weigh  against  the  counterpoise,  which  must  be 
washed  successively  with  the  first  and  second  spirit  filtrates.  Add  on  to 
the  Aveight  thus  found  the  270  c.c.  solubihty  correction  (The  100  c.c. 
of  spirit  used  for  washing  does  not  redissolve  any  weighable  quantity  of 
the  precipitated  dextrin.)  At  times  the  dextrin  precipitate  sticks  some- 
what to  the  flask  : . in  such  cases  rinse  first  with  a little  alcohol,  and  then 
dissolve  out  with  a small  quantity  of  water,  and  evaporate  to  dryness  in  a 
weighed  dish.  Add  the  quantity  thus  found  to  the  total. 

As  in  some  cases  the  spirits  may  precipitate  proteins  as  well  as  dextrin, 
it  is  advisable,  where  special  accuracy  is  required,  to  make  a nitrogen  deter- 
mination in  the  dry  precipitate.  For  this  purpose  fold  up  the  filter  paper, 
and  Kjeldahlise  it  together  with  the  precipitate  in  the  usual  manner. 
Deduct  the  weight  of  protein  from  the  total  weight  of  precipitate. 

Occasionally  the  proteins  present  will  not  separate,  and  produce  an 
opalescent  liquid  which  filters  badly  and  extremely  slowly.  In  this  case 
make  a fresh  estimation,  using  stronger  spirit,  say  92-94  per  cent.,  for 
precipitation.  Let  it  stand  at  least  12  hours,  or  till  clear,  then  wash  the 
precipitate  three  times  by  decantation  in  the  flask,  shaking  vigorously,  and 
allowing  to  subside  each  time,  using  for  this  purpose  the  weaker  spirit. 
Collect  and  weigh  as  before.  In  this  case  make  a special  test  for  the 
correction  Avith  some  purified  dextrin,  operating  in  the  same  manner,  and 
evaporating  down  knoAAm  fractions  of  the  lots  of  spirit  used. 

It  should  be  added  that  alcohol  precipitates  in  this  manner  not  only 
dextrin,  but  also  other  gum-like  bodies  present,  Avhich  are  frequently 
returned  in  analysis  as  “ indeterminate  matters.'" 

867.  Polarimetric  Estimations. — ^In  addition  to  the  method  already 
described  of  estimating  maltose  and  dextrin  by  means  of  Fehling's  solution, 
there  is  a second  process  in  which  certain  optical  properties  of  these  bodies 
are  employed  in  the  determination  of  dextrin,  instead  of  hydrolysing  that 
substance  into  glucose  by  means  of  dilute  acid.  This  particular  modifica- 
tion is  of  special  value  as  a part  of  the  process,  to  be  hereafter  described,  of 
the  estimation  of  starch,  consequently  it  requires  careful  explanation. 

As  has  been  already  stated,  the  sugars,  in  common  Avith  several  other 
bodies,  are  capable  of  rotating  the  plane  of  polarisation  of  a ray  of  light.. 


ESTIMATION  OF  CARBOHYDRATES. 


807 


They  possess  this  property  not  only  in  the  solid  state,  but  also  when  in 
solution  ; further,  the  amount  of  rotation  is  very  nearly  proportional  to  the 
degree  of  concentration  of  the  solution. 


868.  Specific  Rotatory  Power. — ^The  angular  rotation  of  a ray  of  polarised 
light  by  a plate  of  any  optically  active  substance,  I decimetre  (3-937  inches) 
in  thickness,  is  termed  its  “ specific  rotatory  power.""  In  most  substances 
this  has  to  be  obtained  by  calculation,  because  of  the  difficulty  of  getting 
transparent  plates  of  a sufficient  thickness.  A solution  of  known  strength 
is  prepared,  and  from  tlie  rotatory  power  of  this  solution  the  specific  rota- 
tory power  may  be  calculated.  The  rotatory  power  of  solutions  of  the 
same  strength  may  vary  with  the  temperature,  and  also  with  the  solvent 
employed,  hence  it  is  necessary  to  note  the  strength  of  the  solution  at  the 
time  of  the  estimation,  and  also  the  solvent  used.  The  apparent  or  sensible 
specific  rotatory  power  of  a substance  is  found  by  dividing  the  angular 
rotation  observed  in  the  polarimeter  (a)  by  the  length  of  the  tube  in  deci- 
metres (/,  usually  = 2)  in  which  the  liquid  is  observed,  and  by  the  degree 
of  concentration  (c),  that  is  the  number  of  grams  in  100  c.c.  of  the  liquid. 
S being  the  specific  rotatory  power,  then  the  above  is  represented  by  the 
formula — 

g ^ a ^ lOOt* 

I ~l  X c 

The  rotatory  power  of  a substance  depends  on  the  nature  of  the  light  used  ; 
as  the  instrument  to  be  described  is  one  in  which  the  yellow  monochromatic 
light  of  the  sodium  flame  is  employed,  all  numbers  given  will  be  for  light 
of  that  description,  which  is  often  indicated  by  the  symbol  Sd. 

In  measuring  rotatory  powers  of  sugars  it  has  been  found  convenient 
to  take  a plate  of  quartz,  I millimetre  in  thickness,  as  the  standard  of  com- 
parison. According  to  the  latest  and  most  accurate  measurements,  such 
a plate  produces  an  angular  rotation  of  21°  44'  = 21-73°  for  the  sodium 
flame  (Sd).  The  strength  of  the  cane  sugar  solution  which,  in  a tube 
2 decimetres  in  length,  shall  exercise  the  same  rotary  power,  is  that  equal 
to  16-350  grams  of  sugar  in  each  100  c.c.  of  the  solution. 


Sd 


100  X 21-73 
2 X 16-350 


66-45° 


as  the  specific  rotatory  power  of  cane  sugar. 


All  sugars  do  not  rotate  the  plane  of  polarisation  in  the  same  direction  : 
thus,  some  twist  it  to  the  right,  or  in  the  direction  of  the  hands  of  the  clock, 
others  twist  it  towards  the  left.  The  terms  dextro-  and  Isevo -rotation 
are  applied  to  the  right-handed  and  left-handed  rotation  respectively. 
Also  the  symbol  + is  used  to  represent  dextro-  and  — to  represent  laevo- 
rotation.  The  specific  rotatory  power  of  substances  varies  somewhat 
with  the  degree  of  concentration  of  the  solution.  For  a solution  of  approxi- 
mately 10  per  cent,  strength,  that  of  substances  of  importance  in  conjiec- 
tion  with  the  chemistry  of  wheat  and  flour  is  appended  •. — 

Specific 


Substance. 

Cane  Sugar 

Formula. 

C12II22G11 

Rotary  Power. 

+ 66-5° 

Maltose 

Ci2H220ii 

+138-3° 

Glucose,  Dextrose 

C6H12O6 

+ 52-5° 

Fructose,  Laevulose 

C6H12O6 

- 98°  at  15°  C. 

Invert  Sugar 

2C6H12O6 

- 22-7°  at  15°  C 

Dextrin 

GeHioGe 

+200-4° 

869.  The  Polarimeter. — In  order  to  measure  the  amount  of  rotatory 
power  possessed  by  various  bodies,  an  instrument  known  as  a polarimeter 


808 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


is  employed  (sometimes  spoken  of  incorrectly  as  a “ polariscope  There 
are  various  forms  of  this  instrument,  but  one  of  the  simplest  is  that  known 
as  the  half -shadow  polarimeter  or  “ saccharimetre  a penombres."'  A well- 
known  make  of  this  instrument  is  that  manufactured  by  Schmidt  & 
Haensch  of  Berlin,  and  supplied  by  C.  Baker,  Holborn,  which  is  illustrated 
in  Fig.  119. 


Fig.  119. — Half-shadow  Polarimeter  and  Vernier. 


By  means  of  a specially  constructed  bunsen  lamp,  a sodium  flame  is 
produced,  and  toward  this  the  end,  S,  of  the  polarimeter  is  directed  while 
employing  the  same.  When  using  the  polarimeter  it  is  well  to  work  in  a 
room  from  which  all  light  other  than  that  of  the  sodium  flame  is  excluded. 
The  instrument  consists  essentially  of  a tripod  support,  carrying  a hori- 
zontal frame,  in  which  is  placed  the  tube  filled  with  the  solution  under 
examination,  and  having  at  the  one  end,  P,  the  polarising  prism,  and  at 
the  other  the  analyser.  A,  together  with  a small  magnifying  arrangement 

used  as  an  eye-piece,  P.  Immediately  behind 
the  analyser,  A,  is  the  disc,  K,  on  which  is  en- 
graved the  scales  of  the  instrument.  Follow- 
ing this  is  the  trough  with  hinged  lid,  in  which 
are  placed  the  tubes  containing  the  liquid  under 
examination. 


B 


Fig.  120. — Polarimeter 
Tube. 


870.  Polarimeter  Tubes. — ^These  are  now 
usually  made  of  glass  and  are  fitted  at  the 
ends  with  brass  caps.  Those  most  commonly 
used  are  exactly  20  centimetres  in  length  from 
end  to  end  inside  the  caps.  The  left-hand  illus- 
tration, Fig.  120,  represents  the  tube  with  the 
ends  screwed  on  ; the  other  shows  the  tube  in 
section.  Each  cap  contains  a glass  plate  which 
fits  accurately  to  the  end  of  the  tube  ; above 
the  glass  plate  is  a washer  of  leather  ; on  screw- 
ing on  the  cap  this  washer  exerts  an  equable 
pressure  on  the  glass  plate,  and  so  makes  a water- 
tight joint.  The  mistake  must  not  be  made  of 
placing  the  washer  inside  instead  of  outside  the 
glass  plate.  When  using  the  tube,  it  is  first 
cleaned,  then  dried,  or  rinsed  with  a few  drops 
of  the  liquid  under  examination  ; one  of  the 
caps  is  next  screwed  on.  The  tube  is  then 
filled  with  the  solution,  any  bubbles  are  allowed 
to  escape,  and  then  the  second  glass  plate  is 
slidden  over  the  end  and  screwed  tight  by 


ESTIMATION  OF  CARBOHYDRATES. 


809 


means  of]  the  cap.  If  properly  filled,  the  tube  should  contain  no  air, 
neitherjshould  it  leak.  If  there  should  be  any  tendency  to  leakage,  it  may 
be  prevented  by  very  slightly  greasing  the  ends  of  the  tube.  It  will  be  evident 
that  such  a tube  contains  a layer  of  the  liquid  exactly  20  centimetres  in  length. 

871.  Polarimeter  Tube,  with  Thermometer. — ^Fig.  121  shows  a polari- 
meter  tube  of  slightly  different  construction  : it  is  in  the  first  place  22 
instead  of  20  centimetres  long.  On  the  top  there  is  a tubulure,  by  which 
a thermometer  is  inserted  in  order  to  determine  the  temperature  of  tlie 
solution  at  the  time  the  estimation  is  made.  The  use  of  this  particular 
form  of  tube  will  be  described  hereafter. 


Fig.  121. — Polarimeter  Tube,  with  Thermometer. 


872.  Verification  of  Zero  of  Polarimeter. — ^The  first  operation  to  be 
performed  in  starting  work  with  a new  polarimeter  is  to  verify  the  zero  of 
the  graduated  scale  of  the  instrument.  The  commonest  and  most  generally 
useful  form  is  a scale  graduated  into  angular  degrees,  namely,  90°  to  the 
right  angle,  or  360°  to  the  whole  circle.  In  addition  to,  or  instead  of,  the 
angular  scale,  some  instruments  are  provided  with  a sugar  scale.  This 
latter  is  a scale  of  100  degrees,  so  arranged  that  when  a specified  quantity 
of  cane  sugar  is  taken,  the  number  of  degrees  indicated  by  the  polarimeter 
represents  the  percentage  of  pure  sugar  without  any  calculation.  For 
present  purposes,  the  angular  scale  only  need  be  considered.  On  the  dial 
of  the  instrument  being  described  there  is  engraved  a whole  circle  of  360° 
graduated  into  half -degrees,  the  zero  being  on  the  right-hand  side,  and  the 
degrees  reading  upward  and  to  the  left,  right  round  to  360.  There  are  two 
fixed  vernier  scales,  n,  n,  one  on  each  side  of  the  dial.  Two  magnifying 
glasses,  I,  I,  are  provided  in  order  to  read  the  scales.  By  means  of  the 
milled  head,  T,  the  dial  may  be  readily  rotated  in  either  direction,  together 
with  the  eye-piece  and  analysing  prism.  To  make  this  verification  of  the 
zero,  commence  by  placing  some  fused  sodium  chloride  in  the  platinum 
spoon  of  the  bunsen  lamp,  then  light  the  bunsen,  and  turn  the  spoon  into 
the  flame,  so  that  an  intense  yellow  light  is  produced.  Arrange  the  axis 
of  the  instrument  in  the  direction  of  the  flame,  so  that  on  looking  through 
the  eye-piece  a brilliant  yellow  field  is  seen.  Next  fill  one  of  the  20  centi- 


810 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

metre  tubes  with  distilled  water,  and  put  it  in  its  proper  position  in  the 
polarimeter.  Place  the  zero  of  the  vernier  in  coincidence  with  that  of 
the  scale,  and  look  carefully  through  the  instrument  in  order  to  see  whether 
both  halves  of  the  field  are  equally  illuminated.  Turn  the  milled  head,  T, 
very  slightly  in  either  direction  ; one  half  of  the  field  becomes  dark,  and 
the  other  lighter.  Now  focus  the  eye-piece,  T,  by  drawing  it  out  or  pushing 
it  in  until  the  vertical  line,  dividing  the  two  halves  of  the  field,  is  sharply 
defined.  Having  focussed  the  eye-piece,  turn  T back  again  until  the  two 
halves  of  the  field  are  equally  illuminated  : note  the  position  of  the  vernier 
and  see  whether  it  coincides  with  the  zero  of  the  scale.  (For  reading  the 
vernier  use  the  eye-piece,  I,  drawing  it  in  or  out  until  the  scale  is  sharply 
in  focus.)  Should  the  two  agree,  once  more  displace  T,  and  again  bring 
it  back  to  the  position  in  which  the  two  halves  of  the  field  are  equally  bright, 
and  read  the  vernier.  Observe  whether  the  two  readings  of  the  zero  are 
alike.  If  the  zero  of  the  instrument  is  found  correct,  well  and  good,  but 
if  not,  turn  T until  the  zero  of  the  vernier  is  exactly  over  that  of  the  scale  ; 
then  slacken  the  milled  heads  immediately  underneath  A,  and  screw  in  or 
out,  until  the  two  halves  of  the  field  are  of  the  same  depth  of  tint.  Make 
this  adjustment  most  carefully  ; when  once  made,  re-tighten  these  milled 
heads  until  the  tube  A is  securely  fixed  in  the  correct  position.  The  instru  ■ 
ment  will  then  be  permanently  in  adjustment. 

The  pointer,  A,  is  used  for  the  purpose  of  regulating  the  degree  of  sensi* 
tiveness  of  the  instrument.  The  nearer  the  pointer  is  to  zero  the  darker 
is  the  half-shadow  side  of  the  field  for  the  same  amount  of  angular  displace- 
ment of  the  zero  of  the  angular  scale,  and  therefore  the  more  sensitive 
is  the  reading.  With  absolutely  transparent  solutions,  h may  be  fixed  at 
zero,  but  with  solutions  that  are  not  quite  clear,  the  pointer  must  be  moved 
slightly  away  from  zero  so  that  sufficient  light  may  pass  through.  When  h 
is  moved,  the  zero  of  the  dial  plate  must  again  be  adjusted  by  means  of  the 
milled  heads  under  A.  Usually,  when  the  instrument  is  received  from  the 
makers,  h is  arranged  in  the  most  convenient  position  for  general  work,  and 
the  zero  of  the  instrument  adjusted  accordingly. 

873.  Method  of  Reading  with  Vernier. — ^To  those  not  accustomed  to  the 
use  of  the  vernier  for  the  purpose  of  accurately  reading  graduations  on 
instruments  of  exactitude,  a few  words  of  explanation  of  that  device  will 
be  acceptable.  The  vernier  is  a small  scale  which  slides  over  the  gradua- 
tions of  the  principal  scale  of  the  instrument.  On  the  vernier  a length,  equal 
to  29  of  the  half-degree  graduations  on  the  fixed  scale,  is  divided  into  30 
equal  parts.  As  a consequence,  each  division  on  the  vernier  is  exactly 
twenty-nine  thirtieths  of  each  on  the  fixed  scale.  Bearing  this  in  mind, 
let  us  see  how  the  vernier  is  used  in  actual  work.  Suppose  that  with  the 
polarimeter  a sugar  solution  is  placed  in  the  instrument,  and  the  analyser 
turned  until  the  two  halves  of  the  field  are  illuminated  equally.  It  now 
becomes  necessary  to  read  off  the  number  of  degrees  through  which  the 
analysing  prism  has  been  rotated.  On  looking  at  the  scale,  we  find  that 
the  zero  of  the  vernier  is  between,  say  94  and  94-5  degrees.  Look  along  the 
vernier  scale  in  the  direction  of  the  95  until  one  of  the  graduations  on  the 
vernier  exactly  coincides  with  one  on  the  fixed  scale.  If  this  graduation 
on  the  vernier  is  7 from  the  zero,  then  the  accurate  reading  of  the  polarimeter 
is  94® 7'  (94  degrees  7 minutes,  the  minute  being  of  a haK-degree,  as  there 
are  60  minutes  to  the  degree).  In  fact,  whatever  number  graduation  on  the 
vernier  coincides  with  one  on  the  other  scale,  the^  number  of  that  particular 
vernier  graduation  represents  the  fraction  of  a half-degree  in  minutes. 
This  will  be  seen  to  be  the  case  on  reflection.  A fuller  explanation  of  the 
vernier  may  be  found  in  GanoFs  or  other  work  on  “ Physics.'' 


ESTIMATION  OF  CARBOHYDRATES. 


811 


In  Fig.  119,  the  vernier  scale  is  shown  to  the  right  of  the  illustration. 
In  that  particular  instrument  the  main  scale  is  divided  into  quarter-degrees 
and  the  vernier  scale  into  25  parts.  Each  graduation  on  the  vernier  scale  is 
therefore  equal  to  one  twenty-fifth  of  a quarter-degree,  or  0-01°. 


874.  Polarimetric  Estimation  of  Cane  Sugar. — ^As  a matter  of  practice 
the  student  will  do  well  to  make  some  polarimetric  estimations  on  pure  cane 
sugar.  For  this  purpose  powder  finely  some  clean  cofiee  sugar  crystals, 
and  dry  for  a short  time  at  100°  C.  Make  up  respectively  10  and  20  per 
cent,  solutions  in  distilled  water,  100  c.c.  of  each.  Fill  a tw^o -decimetre 
tube  with  the  10  per  cent,  solution,  which  must  be  perfectly  clear  and 
transparent.  Prepare  the  polarimeter  for  working  and  introduce  the  tube. 
By  means  of  the  milled  head,  rotate  the  analyser  to  the  right  until  the  point 
is  attained  at  which  the  change  from  illumination  of  the  one  side  of  the 
field  to  that  of  the  other  occurs  with  great  sharpness.  Turn  the  milled 
head  very  slowly,  and  observe  carefully  the  exact  point  at  which  equal 
illumination  is  reached.  Read  off  the  number  of  degrees  by  means  of  the 
vernier  on  the  right-hand  side  of  the  instrument  ; then  shift  the  analyser, 
once  more  bring  it  back  to  the  neutral  point,  and  again  read.  The  two 
readings  should  agree  to  within  2 minutes  (2').  If  the  sugar  be  absolutely 
pure,  and  the  operation  performed  correctly,  the  reading  should  be  precisely 
13°  18'.  This  signifies  that  the  sample  under  examination  contains  exactly 
100  per  cent,  of  pure  cane  sugar.  Similarly,  if  the  polarimeter  stood  at 
12°47',  we  should  state  that  the  sample  contained  less  than  100  per  cent,  of 


pure  sugar. 

As  angular  measurements  are  now  frequently  expressed  in  decimals  of 
a degree  instead  of  in  minutes,  the  following  table  for  the  conversion  of  one 
into  the  other  may  be  of  service  *. — 


Minutes  — 

decimals. 

Minutes  = 

decimals. 

Minutes  = 

decimals. 

1 

0-016 

11 

0-183 

21 

0-350 

2 

0-033 

12  . . 

0-200 

22  . . 

0-366 

3 . . 

0-050 

13 

0-216 

23  . . 

0-383 

4 

0-066 

14 

0-233 

24  . . 

0-400 

5 

0-083 

15 

0-250 

25  . . 

0-416 

6 

0-100 

16 

0-266 

26  . . 

0-433 

7 

0-116 

17  . . 

0-283 

27  . . 

0-450 

8 

0-133 

18 

0-300 

28  . . 

0-466 

9 

0-150 

19  . . 

0-316 

29 

0-483 

10  . . 

0-166 

20  . . 

0-333 

30  . . 

0-500 

The  figures  13°18'  and  12°47'  become  13-30°  and  12-783°  respectively. 
The  percentage  of  pure  sugar  in  the  second  case  can  readily  be  obtained  by 
calculation  : — 


12-783  X 100 
^13-30  ' 


= 96-1  per  cent. 


With  the  20  per  cent,  solution  the  reading  is  practically  double  (subject 
to  the  fact  that  there  is  a very  slight  diminution  of  specific  rotatory 
power  with  increase  of  concentration  of  cane  sugar).  If  the  sugar  be  pure 
the  reading  is  26°36'  or  26-6°,  or  with  the  same  degree  of  impurity  as  before 
supposed,  12°47'  becomes  25°34'  or  25-566°. 


874.  Polarimetric  Behaviour  of  Inverted  Cane  Sugar. — ^It  has  been 
already  stated  that  the  operation  of  treating  cane  sugar  with  an  acid,  and 
so  causing  it  to  precipitate  cuprous  oxide  from  Fehling’s  solution,  is  termed 
“ inverting  ’’  the  sample.  The  reason  is,  that  a solution  of  sugar  thus 
treated  rotates  the  plane  of  polarisation  to  the  left  instead  of  to  the  right. 
Take  a flask  having  two  marks  on  the  neck,  one  at  50  and  the  other  at  55 


812 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


C.C.,  fill  up  to  the  50  c.c.  mark  with  the  sugar  solution,  and  then  add  5 c.c. 
of  pure  fuming  hydrochloric  acid.  Next  heat  the  flask  in  a water  bath 
until  its  contents  have  acquired  a temperature  of  68°  C.  ; this  operation 
should  be  so  arranged  as  to  occupy  about  10  minutes.  Cool  the  flask  by 
immersion  in  cold  water.  Fill  the  22  centimetre  tube  with  this  solution, 
insert  the  thermometer,  note  the  temperature  and  read  the  amount  of 
rotation,  which  will  be  left-handed,  with  the  polarimeter ; that  is  to  say, 
the  dial  must  be  turned  toward  the  left  instead  of  the  right  in  order  to  reach 
the  critical  point  of  equal  illumination.  That  having  been  done,  the  reading 
must  be  taken  : in  the  instrument  described,  the  point  on  the  left  hand  of 
the  dial,  corresponding  to  zero,  is  180  degrees,  and  the  reckoning  is  usually 
taken  from  that  point.  Working  with  the  10  per  cent,  sugar  solution, 
and  assuming  its  purity,  and  that  the  thermometer  registers  15°  C.  as  the 
temperature  of  the  solution,  then  the  scale  of  the  polarimeter  read  on  the 
left-hand  vernier  stands  at  175°28'.  As  180  corresponds  to  zero,  this 
amounts  to  a minus  reading  of  4°32'. 

180°  - 175°28'  = 4°32'  = 4-533°. 

In  order  to  distinguish  them  as  left-handed  readings,  the  minus  sign 
is  placed  before  the  reading  thus,  — 4°32'  or  — 4-533°.  The  reason  for 
having  a tube  22  centimetres  in  length  will  be  evident  ; the  addition  of 
5 c.c.  of  acid  to  50  c.c.  of  sugar  solution  will  have  diluted  the  solution  to  } ^ 
of  its  former  volume.  When  the  reading  is  taken  in  a 22  centimetre  tube, 
that  also  is  of  the  length  of  the  20  centimetre  tube,  consequently  a depth 
of  liquid  equal  to  20  centimetres  of  the  sugar  solution  before  inversion  is 
looked  through.  Working  in  this  manner,  no  calculation  is  necessary  for 
the  dilution  resulting  from  the  addition  of  the  acid.  Careful  observation 
has  shown  that  a solution  of  cane  sugar  which  before  inversion  had  a right- 
handed  specific  rotatory  power  of  + 66-5°,  gives  after  that  operation  a 
rotation  of  22-7°  to  the  left,  provided  the  temperature  of  the  inverted  solu- 
tion is  15°  C.  Calculated  in  terms  of  specific  rotatory  power,  the  plane  of 
polarisation  is  therefore,  by  the  operation  of  inversion,  rotated  through 
89-2°.  As  has  been  stated,  inversion  produces  from  the  one  molecule  of 
cane  sugar  two  molecules  of  glucose,  one  each  of  dextro-glucose  and  Isevo- 
glucose.  This  latter  body  has  a diminished  rotatory  power  at  high  tem- 
peratures, and  hence  it  becomes  necessary  to  read  the  temperature  at  which 
the  observation  is  made.  At  a temperature  of  0°  C.  the  range  of  inversion 
is  94-1°,  and  diminishes  approximately  by  one  angular  degree  for  every 
three  degrees  rise  in  temperature,  or  0-33  of  an  angular  degree  for  each 
degree  rise  in  temperature.  This  rate  of  diminution  gives  89-2°  for  the 
temperature  of  15°  C.  If  possible  the  readings  of  the  inverted  sugar  solu- 
tion should  be  taken  at  15°  C.,  or  failing  that,  at  as  nearly  as  possible  that 
temperature.  The  correction  per  degree  amounts  to  approximately  gyo 
= 0-0037  of  the  total  range  of  inversion.  Thus  if  the  reading  be  taken  at 
18°  C.,  the  angular  range  will  require  to  be  increased  by  ^fo  of  its  total 
cjuantity. 

A convenient  way  of  expressing  rotatory  power  is  in  that  of  “ Rotatory 
power  per  gram  in  100  c.c.,  the  observations  being  made  in  a 2 decimetre 
tube.''  The  figures  thus  obtained  are  one-fiftieth  of  the  specific  rotatory 
power,  and  are  as  follows  •. — 

Rotatory  Power  per  Gram. 


Cane  Sugar 

1-33° 

Maltose 

2-77° 

Glucose,  Dextrose 

1-05° 

Fructose,  Lsevulose  . . 

— 1*96°  at  15°  C. 

Invert  Sugar  . . 

-045°  at  15°  C. 

Change  due  to  Inversion  of  Cane  Sugar  . . 

1-78°  at  15°  C. 

Dextrin 

4-01° 

ESTIMATION  OE  CARBOHYDRATES. 


813 


Thus  in  the  10  per  cent,  pure  sugar  solution,  the  reading  of  13-3°,  on 
being  divided  by  1-33  gives  10,  showing  that  there  are  present  10  grams  of 
sugar  in  the  100  c.c.  Similarly  the  amount  of  change  as  observed  is 

13-3  + 4-533  - 17-833. 

On  dividing  this  by  1-78,  the  result  is  again  10,  confirming  the  previous 
determination  of  there  being  10  grams  of  sugar  present  in  the  100  c.c.  In 
event  of  the  sugar  containing  10  percent,  of  moisture,  the  right  hand  reading 
would  only  amount  to  11-97°  or  of  13-3°  ; similarly,  the  reading  after 
inversion  and  calculation  to  15°  C.  would  amount  to  — 4-08°.  The  amount 
of  change  would  then  be  11-97  + 4-08  = 16-05.  On  dividing  this  as  before 
by  1-78,  the  result  is  again  9,  confirming  the  determination  by  direct  reading 
on  the  unaltered  sugar.  If,  on  the  other  hand,  some  substance,  as  glucose, 
were  present  which  is  not  capable  of  inversion  by  the  method  adopted,  then 
the  left-hand  reading  would  be  less  than  the  theoretical  amount  for  cane 
sugar.  Thus  the  polarimeter  affords  not  only  a means  of  observing 
the  percentage  of  sugar  present  in  a sample,  but  also  gives  valuable  indications 
as  to  the  nature  of  the  impurity. 

In  making  polarimetric  estimations  of  cane  or  other  sugar  or  saccharine 
body,  20  grams  may  be  taken  and  made  up  to  100  c.c.  In  the  case  of  cane 
sugar,  the  polarimeter  readings  may  be  divided  by  the  following  factors 
~ = 0-266  for  direct  reading,  and  = 0-356  for  amount  of  change 
due  to  inversion.  The  result  is  the  percentage  of  sugar  direct. 

875.  Polarimetric  Determination  of  Dextrin  and  Maltose. — ^Attention 
must  next  be  directed  to  the  method  of  using  the  polarimeter  for  estimating 
the  amount  of  dextrin  in  a liquid  containing  both  dextrin  and  maltose. 
Should  the  liquid  contain  any  coagulable  proteins,  they  should  first  be 
removed  by  heating  a known  weight  of  the  liquid  for  a few  minutes  in  the 
hot-water  bath,  making  up  the  lost  weight  with  distilled  water,  and  then 
filtering.  It  may  happen  that  the  liquid  is  not  sufficiently  clear  to  be 
transparent  in  a layer  of  so  much  as  20  centimetres  ; it  may  then  be  clarified 
by  treatment  with  animal  charcoal  in  the  following  manner  : — Add  to 
the  solution,  in  a flask,  about  one-fifth  of  its  volume  of  powdered,  recently 
ignited,  pure  animal  charcoal.^  Shake  up  vigorously  for  a few  minutes, 
and  pass  through  a dry  filter.  Return  the  filtrate  to  the  paper  until  it 
comes  through  perfectly  clear.  It  is  usualty  preferable,  however,  instead 
of  treating  with  charcoal,  to  dilute  the  liquid  with  water,  as  charcoal  appar- 
ently exercises  an  absorbent  effect  on  some  of  the  carbohydrates.  Subject 
to  this  reservation,  for  the  polarimetric  reading,  as  concentrated  a solu- 
tion as  possible  should  be  taken,  and  the  observation  made  in  the  20  centi- 
metre tube.  After  reading  with  the  polarimeter,  dilute  down  to  the  right 
strength,  and  estimate  maltose  by  Fehling’s  solution. 

Knowing  the  quantity  of  maltose  present,  in  order  to  calculate  the  pro- 
portion of  the  polarimetric  effect  due  to  dextrin,  the  amount  of  rotation 
due  to  maltose  must  be  calculated.  On  multiplying  the  number  of  grams 
of  maltose  in  100  c.c.  of  the  solution  by  2-78,  the  result  is  the  angular  rota- 
tion due  to  the  maltose.  Subtract  this  number  from  the  observed  angular 
rotation,  and  the  remainder  is  the  angular  rotation  due  to  dextrin.  This 
angular  rotation,  on  being  divided  by  4-01,  gives  the  grams  of  dextrin  in 
100  c.c.  of  the  liquid.  From  these  data  the  percentage  of  dextrin  and 
maltose  in  the  original  substance  may  be  calculated. 

As  an  illustration  of  the  polarimetric  estimation  of  dextrin,  the  following 

^ To  prepare  this,  take  1 lb.  of  pulverised  animal  charcoal  (bone  charcoal)  and  boil 
with  2 quarts  of  commercial  hydrochloric  acid  diluted  with  1 gallon  of  water.  Filter 
through  calico,  and  wash  with  water  till  free  from  acid,  dry  and  ignite  to  redness  in  a 
closed  crucible.  Store  in  a well-stoppered  bottle. 


814 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


example  of  the  analysis  of  a sample  of  wheat  germ  is  given.  A 10 
per  cent,  solution  of  the  substance  was  made  with  cold  water,  filtered,  shaken 
up  with  animal  charcoal,  and  again  filtered  until  clear.  The  clear  solution 
was  weighed  in  a beaker,  raised  to  100°  C.  in  the  water  bath,  made  up  to 
original  weight,  and  filtered  from  the  coagulated  albumin.  The  reading 
with  the  polarimeter  was  2-00°  to  the  right.  A maltose  estimation  was 
made  with  20  c.c.  of  the  solution  to  25  c.c.  Fehling’s  solution,  and  50  c.c.  of 
water.  The  resulting  precipitate  was  in  this  instance  converted  by  ignition 
into  cupric  oxide  (CuO)  and  weighed  as  such,  then — 

Wt.  of  CuO,  0-1515  X 0-7257  = 0-1099  gram  of  maltose  in  20  c.c.  of 
10  per  cent,  solution. 

0-1099  X 5 = 0-5495  gram  of  maltose  in  100  c.c. 

0-5495  X 10  = 5-495  per  cent,  of  maltose  in  the  substance. 

Then,  0-5495  x 2-78  = 1-52  = angular  rotation  due  to  maltose. 

Total  angular  rotation,  2 — 1-52  = 0-48  = angular  rotation  due  to 
dextrin. 

^ ^ j = 0-12  gram  of  dextrin  in  100  c.c. 

0-12  X 10  = 1-20  per  cent,  of  dextrin  in  the  substance. 

876.  Estimation  of  Starch. — ^This  estimation  may  be  roughly  made  by 
retaining  for  examination  the  whole  of  the  washings  from  the  gluten  test 
for  wheat  or  flour.  For  this  purpose  wash  the  dough  in  small  quantities 
of  water  at  a time  until  the  water  remains  clear,  the  washings  being  poured 
into  a large  beaker.  Stir  the  starch  and  water  thoroughly  together,  and 
then  strain  through  a piece  of  fine  silk  into  a second  clean  beaker,  in  order 
to  recover  any  fragments  of  gluten  that  may  possibly  have  been  in  the  first 
instance  forced  through  the  silk.  Having  washed  the  whole  of  the  starch 
through  the  silk,  stand  the  beaker  aside,  in  order  to  allow  the  starch  to 
subside.  Counterpoise  a pair  of  filters  and  arrange  them  in  funnels  one 
under  the  other,  so  that  the  lower  receives  the  filtrate  of  the  upper.  Remove 
the  lower  funnel  and  pour  the  supernatant  liquid  from  the  starch  on  to  the 
upper  filter  ; as  soon  as  the  filtrate  runs  clear,  replace  the  second  funnel 
and  continue  the  filtration,  finally  rinsing  the  whole  of  the  starch  on  to  the 
filter  ; wash  with  distilled  water  and  dry,  first  for  a few  hours  at  40°  C., 
and  afterwards  in  the  hot-water  oven.  The  reason  for  first  drying  at  a low 
temperature  is  to  prevent  the  gelatinisation  of  the  starch  ; this  preliminary 
drying  may  generally  be  done  on  the  top  of  the  hot- water  oven.  The 
counterpoise  filter  may,  of  course,  be  dried  direct  in  the  oven,  and  at  the 
end  weighed  against  the  starch  and  filter.  The  process  of  drying  is  much 
accelerated  by  giving  the  starch  a final  washing  with  95  per  cent,  alcohol 
so  as  to  remove  the  water.  This  treatment  gives  the  weight  of  starch  cells 
of  the  wheat  or  flour.  These,  it  must  be  remembered,  contain  a certain 
quantity  of  starch  cellulose. 

877.  Estimation  of  Soluble  Starch  by  Conversion  into  Dextrin  and 
Maltose. — -For  more  refined  estimations  the  method  of  first  converting  the 
starch  into  dextrin  and  maltose,  and  then  determining  those  bodies,  is 
preferable.  O’Sullivan  gives,  in  the  Journal  of  the  Chemical  Society  for 
tlie  year  1884,  a description  in  detail  of  his  method  of  making  such  esti- 
mations. The  method  is  based  on  first  removing  dextrin,  maltose,  and 
other  soluble  bodies  from  the  substance  by  the  use  of  water  and  other 
solvents,  tlien  converting  the  starch  into  dextrin  and  maltose  by  the  action 
tliereon  of  malt  diastase,  and  then  estimating  the  dextrin  and  maltose  by 
Fehling’s  solution  and  the  polarimeter.  The  following  special  reagents  are 
necessary  : — 

878.  Alcohol. — This  reagent  is  required  absolutely  free  from  water 


ESTIMATION  OF  CARBOHYDRATES. 


815 


and  also  mixed  with  water  in  different  proportions.  “ Absolute  ’’  or  water- 
free  alcohol  may  either  be  purchased  or  prepared  in  tlie  following  manner  : 

■ — Take  two  quarts  of  the  best  methylated  spirits,  add  thereto  about  half 
its  weight  of  recently  and  thoroughly  burnt  quicklime,  shake  up  vigorously 
two  or  three  times  a day  for  3 or  4 days.  The  quicklime  will  de- 
hydrate the  acohol,  by  combining  with  the  water  present,  to  form  slaked 
lime  (calcium  hydroxide).  The  alcohol  must  next  be  separated  from  the 
lime  by  distillation.  For  this  purpose  arrange  a glass  flask  in  a large  sauce- 
pan to  be  used  as  a water  bath.  Fit  a cork  with  leading  tube  to  the 
neck  of  the  flask,  and  connect  this  up  to  a condensing  worm,  provided  with 
a copious  supply  of  water.  Be  sure  that  all  joints  are  perfectly  air  tight. 
Fill  the  water  bath  with  water,  and  make  arrangements  for  securing  the 
flask,  so  that,  as  it  becomes  lighter  by  the  evaporation  of  the  spirit,  it  shall 
not  capsize.  Pour  off  the  clear  alcohol  from  the  lime  into  the  flask.  Intro- 
duce a few  small  sharp-pointed  steel  tacks  : these  will  cause  the  liquid 
to  boil  without  bumping.  Then  connect  up  the  whole  of  the  apparatus, 
and  raise  the  bath  to  the  boiling  point  by  means  of  a bunsen.  Collect  the 
distilled  spirit  in  a dry  stoppered  bottle.  It  must  be  remembered  that 
alcohol  is  highly  inflammable,  and  therefore  every  care  must  be  taken  to 
prevent  an  accident  through  fire.  The  lime  used  for  the  desiccation 
of  the  alcohol  will  still  contain  a considerable  quantity  of  spirit  ; this  may 
in  great  part  be  recovered  by  pouring  the  whole  on  to  stout  calico  and  squeez- 
ing as  much  as  possible  of  the  spirit  out. 

Dry  potassium  carbonate  is  perhaps  frequently  a more  convenient 
agent  for  desiccating  alcohol.  The  carbonate  absorbs  the  water,  and  forms 
a heavy  solution  on  which  the  alcohol  floats.  When  distilling,  both  solu- 
tions may  be  poured  into  the  still  together,  and  distillation  in  a water  bath 
•continued  as  long  as  anything  comes  over.  The  residual  solution  of  potas- 
sium carbonate  may  then  be  evaporated  to  dryness  in  an  ordinary  iron 
saucepan,  and  used  again  for  the  same  purpose. 

Absolute  alcohol  has  a specific  gravity  of  0-7937  at  15°  C.  The  per- 
centage of  water  is  usually  obtained  by  observing  the  specific  gravity 
by  means  of  a hydrometer.  This  is  a glass  instrument  consisting  of  a 
weighted  bulb  and  stem  carrying  a scale  ; the  hydrometer,  on  being  placed 
in  a liquid,  floats  higher  or  lower  according  to  its  density.  The  specific 
gravity  of  water  is  often  reckoned,  for  convenience,  at  1000  ; absolute 
.alcohol  is  then  said  to  have  a density  of  793-7.  A hydrometer  should  be 
procured  from  the  instrument  makers  marked  in  single  degrees  from  750 
to  1000. 

Cool  down  some  of  the  distilled  alcohol  to  15°  C.,  and  pour  out  into  a 
hydrometer  jar.  (This  is  a tall  glass  vessel  in  which  the  instrument  can 
just  float.)  Introduce  the  hydrometer,  and  observe  the  density  of  the 
liquid  ; should  this  be  from  795  to  800,  the  alcohol  may  be  considered  for 
practical  purposes  absolute.  Mixtures  of  alcohol  and  water  of  the  following 
•densities  are  also  required  : — 820,  830,  860,  880,  and  900  degrees.  These 
may  be  prepared  by  adding  water  to  methylated  spirit. 

Methylated  spirit  has  itself  a density  of  about  820,  and,  when  re- 
distilled, may  be  used  when  that  strength  is  directed.  The  strength  of 
.solutions  of  other  degrees  of  specific  gravity  is  given  below. 


Specific 

Gravity 
at  15-5°  C. 

1-0000 

Absolute 

Alcohol 
by  volume,  % 

0-00 

Specific 

Gravity, 
at  15-5°  C. 

0-8599 

Absolute 
Alcohol, 
by  volume, 

81-44 

0-9499 

41-37 

0-8299 

91-20 

0^9198 

57-06 

0-8209 

93-77 

0-8999 

65-85 

0-7999 

98-82 

■0-8799 

73-97 

0-7938 

100-00 

816 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


In  order  to  obtain  diluted  spirits  of  the  other  gravities  required,  water 
may  be  added  in  the  requisite  proportion  to  methylated  spirit.  As  alcohol 
and  water,  on  being  mixed,  contract  in  volume  [i.e.,  50  c.c.  of  alcohol  and 
50  c.c.  of  water  produce  less  than  100  c.c.  of  the  mixture),  the  amount  of 
water  to  be  added  to  the  methylated  spirit  to  produce  each  degree  of  dilu- 
tion cannot  be  calculated  with  absolute  exactness,  but  still  sufficiently  near 
for  present  purposes.  Knowing  that  alcohol  of  sp.  gr.  of  820  contains 
93-77  of  alcohol  and  6-23  of  water,  the  quantity  necessary  to  be  added  is 
determined  by  the  following  formula  : — 

A = percentage  of  absolute  alcohol  in  stronger  spirit. 
a = ,,  ,,  ,,  ,,  weaker  ,, 

W = water  ,,  stronger  ,, 

w = ,,  ,,  ,,  weaker  ,, 

Q z=  quantity  of  water  to  be  ^dded  to  100  c.c.  of  the  lower 
sp.  gr.  spirit  to  produce  the  higher  sp.  gr.  spirit. 

Then  Q = ^ ^ _ W 

a 

From  this  formula  it  is  found  that  to  100  c.c.  of  820  spirit  the  following 
approximate  quantities  of  water  must  be  added  to  produce  the  spirits  of 
correspondingly  higher  gravities  : — sp.  gr.  830,  3 c.c.  ; 870,  21  c.c.  ; 900, 
43  c.c. 

879.  Diastase. — Take  2 or  3 kilograms  (5  or  6 lbs.)  of  finely  ground  pale 
barley  malt,  add  sufficient  water  to  completely  saturate  it,  and  when 
saturated  to  slightly  cover  it.  Allow  this  mixture  to  stand  for  3 or  4 
hours,  and  then  squeeze  as  much  as  possible  of  the  solution  out  by  means 
of  a filter  press.  Should  the  liquid  not  be  bright,  it  must  be  filtered.  To 
the  clear  bright  solution,  add  alcohol  of  sp.  gr.  830  as  long  as  it  forms  a 
precipitate,  and  until  the  liquid  becomes  opalescent  or  milky.  Wash  this 
precipitate  with  alcohol  of  sp.  gr.  860-880,  and  finally  with  absolute  alcohol. 
Press  the  precipitate  between  folds  of  cloth,  in  order  to  dry  it  as  much  as. 
possible.  Then  place  the  precipitate  in  a dish,  and  keep  under  the  exhausted 
receiver  of  an  air-pump,  together  with  a vessel  containing  concentrated 
sulphuric  acid,  until  the  weight  becomes  constant.  The  kind  of  air-pump 
known  as  a mercury  sprengel  pump  is  best  fitted  for  this  purpose.  Prepared 
and  dried  in  this  manner,  diastase  is  a white,  easily  soluble  powder,  retaining 
its  activity  for  a considerable  time.  Store  the  substance  in  a dry  stoppered 
bottle,  and  keep  in  a cool  and  dry  place. 

880.  Method  of  Performing  Analysis. — ^The  analytic  operation  is  per- 
formed in  the  following  manner  : — Weigh  out  accurately  5 grams  of  the 
finely  ground  meal  or  flour  ; introduce  this  quantity  into  a wide-necked 
flask,  with  a capacity  of  100  to  120  c.c.  (a  4 ounce  conical  flask  wdll  be 
found  most  convenient).  Add  sufficient  alcohol  of  sp.  gr.  820  to  just  saturate 
the  flour,  and  then  20  to  25  c.c.  of  ether.  Cork  the  flask,  and  set  aside 
for  a few  hours,  shaking  up  occasionally.  Decant  the  clear  ethereal  solution 
through  a filter,  wash  the  residue  three  or  four  times  with  fresh  quantities 
of  ether,  pouring  the  washings  each  time  on  the  filter.  To  the  residue  add 
80  to  90  c.c.  of  alcohol  of  sp.  gr.  of  900  ; re-cork  the  flask,  and  maintain  the 
mixture  at  a temperature  of  35°  to  38°  C.  for  a few  hours,  shaking  occasion- 
ally. When  the  alcohol  solution  has  become  clear,  decant  it  through  the 
filter  used  for  filtering  the  ether  solution,  and  wash  the  residue  a few  times 
with  alcohol  of  the  strength  and  temperature  directed  above.  Wash  the 
residue  in  the  flask,  and  any  that  may  be  on  the  filter,  into  a beaker  capable 
of  holding  500  c.c.,  and  nearly  fill  the  beaker  with  water.  In  about  24 
hours  the  supernatant  liquid  becomes  clear,  when  gradually  decant 


ESTIMATION  OE  CARBOHYDRATES. 


817 


through  a filter.  Wash  the  residue  repeatedly  with  water  at  35°  to  38°  C., 
and  then  transfer  to  100  c.c.  beaker.  Take  the  filter  from  the  funnel,  open 
out  the  paper  on  a glass  plate,  and  remove  every  particle  by  means  of  a 
camel-hair  brush  cut  short,  and  a fine-spouted  wash-bottle.  Having  thus 
transferred  the  whole  of  the  residue,  the  beaker  should  not  contain  more 
than  40  to  45  c.c.  of  liquid.  Boil  for  a few  minutes  in  the  water  bath,  care 
being  taken  to  stir  well  in  order  to  prevent  “ balling,"’  or  unequal  gelatinisa- 
tion  of  the  starch.  After  this,  cool  down  the  beaker  still  in  the  bath  to  62° 
to  63°  C.,  and  add  0*025  to  0*035  gram  of  diastase  dissolved  in  a few  c.c.  of 
water.  In  a few  minutes  the  whole  of  the  starch  is  dissolved,  and  a trace 
of  the  liquid  gives  no  discolouration  with  iodine.  Continue  the  digestion 
for  about  an  hour,  then  raise  the  bath  to  the  boiling  point,  and  boil  for  8 
or  10  minutes.  Pour  the  contents  on  to  a filter,  and  receive  the  filtrate  into 
a 100  c.c.  measuring  flask  ; carefully  wash  the  residue  with  small  quantities 
at  a time  of  boiling  water.  Cool  the  flask  to  15*5°  C.,  and  make  up  its  con- 
tents to  100  c.c.  with  distilled  water.  Should  the  washings  and  solution 
exceed  100  c.c.,  they  must  be  evaporated  down  to  that  amount. 

Take  a polarimetric  reading  of  this  solution  in  the  20  centimetre  tube. 
Five  c.c.  of  the  solution  is  a convenient  quantity  to  take  for  the  estimation 
of  maltose.  This  is  rather  a small  quantity  to  measure  accurately  ; it  may, 
if  wished,  be  weighed  instead,  or  25  c.c.  may  be  taken  and  diluted  down  to 
100  c.c.  with  water  ; 20  c.c.  of  the  diluted  solution  may  then  be  taken  and 
added  to  25  c.c.  of  Eehling’s  solution  and  50  c.c.  of  water.  Proceed  as  before 
described  with  the  estimations,  and  calculate  the  quantity  of  maltose  from 
the  weight  of  precipitated  CU2O.  Calculate  the  relative  percentages  of 
dextrin  and  maltose  in  the  usual  manner.  Starch  produces  its  own  weight 
of  dextrin  and  fff  = 1*0546  its  weight  of  maltose.  To  obtain  the  weight 
of  starch  from  the  dextrin  and  maltose  it  produces,  the  weight  of  the  dextrin 
must  be  added  to  that  of  the  maltose  divided  by  1*0526,  or  multiplied  by 
0*95.  These  calculations  will  be  rendered  clear  by  the  study  of  the  following 
example  taken  from  O’Sullivan’s  paper. 

In  the  analysis  of  a sample  of  white  wheat,  4*94  grams  were  taken. 
The  100  c.c.  solution  had  an  optical  activity  equivalent  to  8*52°  for  Sd, 
and  contained  2*195  grams  of  maltose. 

2*196  X 2*78  = 6*10°,  angular  rotation  due  to  maltose.  8*52°  — 6*10°  = 
2*42°,  angular  rotation  due  to  dextrin.  _ ().0Q5  gram  of  dextrin 

in  100  c.c. 

Maltose,  2*196  ==  starch,  2*196  X 0*95  = 2*086 

Dextrin,  0*605  = starch,  0*605 


Total  starch  = 2*691 

^ = 54*47  per  cent,  of  starch  present.  ^ 

4*94 

A duplicate  analysis  on  6*009  grams  differed  only  by  0*03  per  cent. 

In  the  absence  of  diastase,  starch  may  usually  be  determined  with 
sufficient  accuracy  for  technical  purposes  in  the  following  manner  : — 
Remove  by  washing  or  otherwise  all  other  carbohydrates,  and  gelatinise 
the  starch  by  heating  with  water.  From  a known  weight  of  the  same 
variety  of  starch  prepare  a solution  of  approximately  the  same  strength. 
Put  50c. c.  of  each  in  a separate  flask,  and  add 50 c.c.  of  10  per  cent,  sulphuric 
acid.  Cork  the  two  flasks,  and  stand  in  a hot-water  bath  until  a drop  on 
being  taken  out  gives  no  reaction  with  iodine  solution.  Then  neutralise 
by  adding  solid  caustic  potash  in  small  fragments,  until  the  solution  gives 
A faintly  alkaline  reaction  to  litmus  paper  ; and  precipitate  from  10  to  25 
c.c.  of  the  solution,  according  to  strength,  with  Fehling’s  solution.  Knowing 

3 G 


818 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


by  the  test  with  pure  starch  what  weight  of  CuaO  it  precipitates  under 
these  conditions,  the  quantity  of  starch  in  the  substance  being  tested  can 
be  readily  calculated. 


881.  Estimation  of  Dextrin  and  Soluble  Starch. — It  occasionally  becomes^ 
necessary  to  estimate  dextrin  in  the  presence  of  soluble  starch,  as,  for  in- 
stance, in  bread  soluble  extracts.  The  following  method  may  then  be 
adopted  ; — Take  20  c.c.  of  the  soluble  extract  and  add  to  250  c.c.  of  redis- 
tilled spirits  ; if  the  precipitate  is  very  little,  take  double  the  quantities 
filter  and  proceed  with  the  estimation  precisely  as  previously  directed  for 
dextrin.  Control  the  results  by  determining  proteins  in  the  dried  and 
weighed  precipitate — the  residue  is  a mixture  of  dextrin  and  starch. 

Proceed  to  estimate  the  starch  in  the  following  manner  : — Prepare  first 
of  all  the  following  reagents  — 

0-5  per  cent,  solution  of  wheat  starch. 

5 per  cent,  solution  of  sulphuric  acid. 

Solution  of  iodine  in  potassium  iodide  of  sherry  tint. 


Take  two  graduated  Nessler  glasses,  and  add  to  each  OT  c.c.  each  of 
iodine  solution  and  sulphuric  acid  ; make  up  to  50  c.c.  with  distilled  water. 
To  one  add  0-5  c.c.  of  starch  solution  and  stir  ; to  the  other  add  the  diluted 
soluble  extract  from  a burette  until  there  is  the  same  depth  of  blue  tint  in 
each.  The  solution  to  be  tested  is  conveniently  of  approximately  the  same 
strength  as  the  standard  starch  solution.  If  this  first  test  shows  it  to  be  too 
concentrated,  dilute,  and  repeat  the  estimation.  Having  read  off  the  solu- 
tion necessary  to  match  the  0*5  c.c.  of  standard  starch,  add  another  0-5  c.c. 
to  the  standard  in  the  Nessler  glass,  and  again  run  in  the  extract  solution 
until  the  colours  are  of  equal  depth  of  tint.  Take  the  reading,  and  add 
another  0-5  c.c.,  and  repeat  the  titration.  In  this  way  three  separate  read- 
ings are  obtained,  which  should  closely  agree.  The  following  are  results, 
obtained  in  an  actual  analysis  : — 


standard  Starch  Solution. 

0*5  c.c. 

1-0  „ 

1-5  „ 

3*0  „ 


Diluted  Bread  Extract. 

0*30  c.c. 
0-55  „ 
0-85  „ 
1*50  „ 


The  whole  of  these  come  very  closely  together,  and  it  was  assumed  that 
1-5  c.c.  of  the  bread  extract  contained  as  much  starch  as  3-0  c.c.  of  the 
standard  starch  solution. 

To  ensure  success  with  this  method  of  starch  estimation  the  solutions 
must  be  dilute,  and  there  should  be  no  other  colour-producing  body  than 
starch  present.  The  iodine  must  not  be  in  large  excess,  but  must  give  a pure 
blue  colour  with  starch  : too  much  produces  a dirty  greenish  blue.  But 
the  iodine  must  be  in  excess  of  the  starch  present.  To  ascertain  this  by 
trial,  after  a titration,  add  a few  drops  more  starch  and  the  colour  should 
darken.  Both  tests  must  be  made  up  with  precisely  the  same  quantity  of 
each  reagent. 

Having  determined  the  starch  in  this  manner,  deduct  the  amount  from 
the  total  of  starch  and  dextrin  precipitated  by  alcohol  ; the  difference  is 
dextrin. 


882.  Estimation  of  Cellulose. — ^The  student  already  knows  that  cellu- 
lose has  the  same  chemical  composition  as  starch,  but  that  it  differs  from  that 
body  in  being  insoluble  in  boiling  water.  The  cellulose  or  woody  fibre  of 
grain  has  been  estimated  at  about  10  per  cent,  of  the  whole  : but  of  this 
much  is  soluble  in  the  digestive  secretions  of  animals,  particularly  those 
which  ruminate,  therefore  an  estimation  of  cellulose  simply  is  not  the  one 


ESTIMATION  OF  CARBOHYDRATES. 


819 


most  valuable  to  tlie  cliemist  whose  investigation  is  made  for  the  purpose 
of  determining  the  food  value  of  a substance.  What  for  this  purpose  should 
be  ascertained  is  that  percentage  of  the  grain  or  flour  which  is  ejected  from 
the  alimentary  canal  in  an  unaltered  condition.  A process  is  therefore 
selected  whicli  is  somewliat  similar  to  the  digestive  action  which  proceeds 
in  the  stomach,  this  action  being  imitated  by  alternate  treatment  with 
dilute  acid  and  alkali. 

883.  Special  Reagents  Necessary. — ^The  first  of  these  is  a 5 per  cent,  solu- 
tion of  sulphuric  acid.  In  a small  beaker  weigh  out  100  grams  of  the  con- 
centrated acid,  and  make  up  to  2 litres.  In  the  next  place  prepare  a 12 
per  cent,  solution  of  caustic  potash  by  weighing  out  240  grams  of  the  pure 
dry  sticks,  dissolving,  and  making  up  to  2 litres  Avith  water.  It  is  im- 
portant that  20  c.c.  of  the  acid  solution  should  be  approximately  neutralised 
by  10  c.c.  of  the  alkali. 

884.  Mode  of  Analysis. — -Take  5 grams  of  the  meal  or  flour,  and  mix 
them  thoroughly  with  150  c.c.  of  water  in  a beaker.  Stand  this  in  a hot- 
water  bath,  and  raise  to  a boiling  heat  in  order  to  effect  the  gelatinisation  of 
the  starch  ; stir  frequently  with  a glass  rod  ; add  50  c.c.  of  a 5 per  cent, 
solution  of  sulphuric  acid,  and  continue  the  boiling  for  an  hour,  stirring 
occasionally,  and  maintaining  the  volume  at  200  c.c.  by  adding  from  time 
to  time  a little  water.  (The  proper  volume  should  be  indicated  by  a mark 
made  with  the  diamond  on  the  outside  of  the  beaker.)  The  acid  Avill  by 
this  time  have  converted  the  starch  into  sugar.  To  this  solution  next  add 
50  c.c.  of  the  solution  of  caustic  potash  ; this  quantity  will  neutralise  the 
free  acid,  forming  potassium  sulphate,  and  will  leave  an  excess  of  alkali  in 
the  solution  approximately  equivalent  to  the  amount  of  acid  first  used. 
Again  boil  in  hot -water  bath  for  an  hour,  adding  water  to  supply  that  lost 
by  evaporation,  and  occasionally  stirring.  At  the  end  of  this  time,  dilute 
with  cold  water,  stir,  and  allow  the  residue  to  subside.  Wash  by  decanta- 
tion, using  large  quantities  of  tap  water  (provided  it  is  absolutely  free 
from  sediment),  pouring  as  little  as  possible  of  the  residue  on  to  the  paper. 
Stout,  well-made  quantitative  Alters  of  about  8 or  10  inches  diameter 
should  be  employed.  Next  transfer  the  residue  to  the  filter,  and  wash  once 
with  dilute  hydrochloric  acid,  in  order  to  dissolve  any  calcium  carbonate 
that  may  be  precipitated  from  ordinary  AA^ater  by  the  potash.  Then  AA'ash 
AAuth  distilled  AA^ater  till  free  from  acid,  and  alloA\^  the  Alter  to  drain.  While 
still  AA^et,  remove  the  filter  paper  from  the  funnel,  carefully  spread  it  out  flat 
on  a sheet  of  glass,  and  AAuth  a AA'ash  bottle  and  short  camel-hair  brush, 
transfer  the  Avhole  of  the  residue  to  a counterpoised  glass  dish  ; dry  in  the 
hot-AA'ater  oven  and  Aveigh.  The  dry  residue  multiplied  by  20  gives  the 
percentage  of  indigestible  fibre  in  the  sample. 

885.  Glycerin  Method  of  Cellulose  Estimation. — ^A  method  of  estimating 
crude  fibre  has  been  devised  by  Honig,  based  on  the  fact  that  protein  and 
starch  become  soluble  in  AA'ater  after  heating  AA'ith  glycerin  to  210°  C.,  at 
AA'hich  temperature  cellulose  is  not  attacked.  The  folloAA'ing  is  a modifica- 
tion of  this  method,  proposed  by  Gabiel,  in  order  to  provide  for  the  solu- 
tion of  certain  substances,  both  nitrogenous  and  non-nitrogenous,  other 
than  cellulose  which  are  unattacked  by  glycerin  alone  : — A solution  of 
caustic  alkali  in  glycerin  is  prepared  by  dissolving  33  grams  of  caustic  potash 
in  glycerin,  and  making  up  to  1 litre.  For  making  the  analysis,  2 grams  of 
the  substance  are  heated  in  a 250  c.c.  flask  on  a piece  of  AA'ire  gauze  over  a naked 
flame,  AAuth  60  c.c.  of  the  potash-glycerin.  At  about  130°  C.  a vigorous 
reaction  occurs,  and  care  must  be  taken  that  none  of  the  solution  is  lost  by 
foaming.  At  a temperature  of  160°  C.  the  reaction  is  for  the  most  part 


820 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


finished,  after  which  the  temperature  is  raised  to  180°  C.  The  mixture  is 
then  poured  into  200  c.c.  of  boiling  water,  weU  stirred,  allowed  to  settle,  and 
the  supernatant  liquid  removed  by  upward  filtration  through  a funnel  having 
a piece  of  linen  tied  over  the  end.  (The  material  known  as  swansdown 
answers  well  for  such  filters.)  The  residue  is  again  boiled  with  200  c.c.  of 
water,  allowed  to  settle  and  filtered,  and  a third  time  with  the  same 
quantity  of  water  to  which  5 c.c.  of  25  per  cent,  hydrochloric  acid  have  been 
added.  The  residual  fibre  is  washed  with  alcohol  and  ether  and  dried. 
The  extremely  small  quantity  of  nitrogenous  substances  left  in  the  crude 
fibre  appears  to  be  in  most  cases  negligible. 

The  centrifugal  separator  has  been  called  into  requisition  for  fibre  esti- 
mations. This  machine  consists  of  a wheel  making  some  3000  or  4000 
revolutions  per  minute,  on  the  circumference  of  which  vessels  are  attached  ; 
the  centrifugal  action  acts  like  gravitation,  only  with  far  more  intensity  in 
separating  bodies  whose  specific  gravity  is  different.  The  quantity  of 
material  taken  for  analysis  is  1 gram  ; in  event  of  this  containing  any  con- 
siderable quantity  of  fat,  it  is  first  shaken  up  with  20  c.c.  of  ether  in  a proper 
tube,  and  subsequently  rotated  in  the  machine.  The  supernatant  ether  is 
poured  off,  and  the  substance  subjected  twice  more  to  the  same  operation 
with  ether,  being  each  time  shaken  up,  and  then  treated  in  the  centrifugal. 
The  ether  is  driven  off  the  residue  by  heating  in  the  water  bath,  30  c.c.  of 
hot  water  added,  and  the  heating  continued  for  about  10  minutes,  the 
contents  of  the  tube  being  stirred  with  a glass  rod  flattened  at  the  end. 
Next,  10  c.c.  of  5 per  cent,  (by  volume)  sulphuric  acid  are  added,  and  the 
heating  and  stirring  continued  for  another  30  minutes.  The  tube  is  now 
rotated  in  the  separator,  at  a speed  of  at  least  2000  revolutions  per  minute, 
for  about  3 or  4 minutes.  Most  of  the  insoluble  matter  is  separated  in  a com- 
pact form  on  the  bottom  of  the  tube  ; the  turbid  liquid  is  poured  off  on  to  a 
weighed  or  counterpoised  filter  sufficiently  large  to  hold  the  contents  of 
the  tube.  The  tube  is  then  refilled  with  40  c.c.  of  hot  water,  stirred  re- 
peatedly during  a period  of  from  10  to  15  minutes,  the  tube  being  meanwhile 
suspended  in  the  water  bath.  The  tube  is  again  rotated,  the  clear  liquid 
poured  off  on  the  filter,  and  the  washing  repeated  in  the  same  way.  The 
residue  is  next  treated  with  30  c.c.  of  hot  water,  and  10  c.c.  of  a 5 per  cent, 
solution  of  caustic  potash,  heated  in  the  water  bath,  and  stirred  repeatedly 
during  30  minutes.  The  tube  is  placed  in  the  separator,  and  the  residue 
washed  in  the  same  way  as  after  the  acid  treatment.  The  fibre  is  next 
thrown  on  to  the  filter,  washed  in  succession  with  alcohol  and  ether,  and 
dried  and  weighed  in  the  usual  manner. 

Analysis  of  Bodies  containing  Carbohydrates. 

886.  Malt. — ^It  is  comparatively  rarely  that  for  bakers’  purposes  an 
analysis  or  assay  of  malt  is  required.  The  principal  point  is  the  character 
and  amount  of  extract  it  affords  on  being  mashed  ; to  this  reference  has 
already  been  made  in  Chapter  XII.,  paragraph  398.  A miniature  mash  of 
the  same  proportions  may  be  made  in  the  following  manner  : — Finely 
grind  tlie  sample  of  malt,  mix  thoroughly,  and  weigh  out  158  grams  ; mix 
with  about  900  c.c.  of  warm  water,  and  place  in  a water  bath  maintained 
at  a temperature  of  60°  C.  Let  it  remain  until  a drop  taken  out  after 
stirring  gives  no  starch  or  amylodextrin  reaction  with  iodine.  Then  raise 
to  the  boiling  point,  cool,  and  transfer  the  whole  to  a litre  flask  ; make  up 
to  tlie  mark  with  distilled  water  ; pour  out  into  a larger  flask  or  beaker, 
and  add  another  50  c.c.  of  water.  Thoroughly  mix,  allow  to  settle,  and  take 
the  density  of  the  supernatant  liquid,  at  a temperature  of  15-5°  C.,  by  means 
of  the  hydrometer.  The  quantities  taken  are  equivalent  to  40  gallons  of 
wort  from  63  lbs.  of  malt  : the  extra  50  c.c.  are  allowed  in  order  to  provide 


ESTIMATION  OF  CARBOHYDRATES. 


821 


for  the  average  amount  of  “ grains  ” resulting  from  this  quantity  of  malt. 
There  are  thus  1000  c.c.  of  wort  from  158  grams  of  malt.  The  percentage 
of  solid  extract  yielded  by  the  malt  is  readily  calculated.  Thus,  supposing 
in  a test  the  hydrometer  density  is  1035,  then  : — 


(1035  - 1000)  X 10 
3-85 


= 90-9  grams  of  solid  extract  in  1000  c.c.  of  wort. 


As  158  : 100  : : 90-9  = 57-53  per  cent,  of  solid  extract. 

The  whole  of  the  constants  in  the  above  may  be  reduced  to  one  single 
factor,  1-644,  and  we  then  have 


(1035  — 1000)  X 1-644  = 57-54  per  cent,  of  solid  extract. 

For  a detailed  description  of  the  method  for  an  exhaustive  assay  of 
malt,  the  reader  is  referred  to  Moritz  and  Morris'  Science  of  Brewing, 
pages  452  et  seq. 


887.  Malt  Extracts. — 'The  following  determinations  should  be  made  in 
analysing  extracts  of  malt  and  similar  preparations  : — Reducing  sugars, 
cane  sugar,  dextrin,  proteins,  water,  phosphoric  acid  (P2O5),  other  mineral 
matter,  specific  rotatory  power,  and  diastatic , capacity  by  Lintner,  or  other 
methods  hereinafter  described.  A 10  per  cent,  solution  of  the  substance 
should  first  be  prepared,  which,  either  with  or  without  dilution,  may  be 
employed  for  the  following  estimations. 

Reducing  Sugars. — Take  2 c.c.  of  10  per  cent,  solution,  and  precipitate 
as  usual  with  Fehling’s  solution  (30  c.c.). 

Cane  Sugar. — This  is  conveniently  determined  by  O'Sullivan's  method. 
Take  20  c.c.  of  10  per  cent,  solution,  make  up  to  100  c.c.,  raise  to  55°  C., 
and  add  0-2  grams  of  solid  brewers'  yeast  (prepared  by  drying  the  liquid 
yeast  on  a towel),  or  compressed  distillers'  yeast  free  from  starch,  digest 
in  a constant  temperature  water  bath  at  55°  C.  for  4 hours,  make  up 
loss  by  evaporation  (or  conduct  the  operation  in  a tightly  corked  flask), 
filter,  and  determine  reducing  sugars  in  10  c.c.  by  Fehling's  solution.  The 
difference  in  weight  of  CU2O  obtained  in  this  and  the  preceding  determina- 
tion is  CU2O  reduced  by  the  glucose  from  cane  sugar,  and  is  readily  calcu- 
lated into  the  percentage  of  that  body. 

Dextrin. — Take  20  c.c.  of  5 per  cent,  solution,  add  to  250  c.c.  of  spirit, 
and  proceed  as  described  under  Estimation  of  Dextrin,  paragraph  866. 
Should  the  amount  of  precipitate  be  very  small,  recommence  the  estimation, 
using  the  10  per  cent,  solution.  Determine  proteins  by  KjeldahTs  process 
in  the  dried  and  weighed  precipitate  ; deduct  from  the  weight  of  precipitate, 
and  calculate  as  dextrin. 

Proteins. — Determine  direct  by  Kjeldahl's  process  on  1-0  gram  of  the 
extract. 

Water. — Take  5 grams  of  extract,  dry  till  weight  is  constant  in  a plati- 
num basin  ; about  36  hours  are  necessary  at  100°  C.  When  speed  is 
an  object,  either  a smaller  quantity  (1-0  gram)  may  be  used,  or  an  oven  at 
110°  C.  employed.  Or  preferably  a vacuum  drying  oven  may  be  used,  in 
which  case  the  drying  may  be  conducted  at  a temperature  below  100°  C. 

Ash. — Ignite  the  dried  residue  from  5-0  grams  (residuum  from  water 
estimation)  until  a white  ash  is  obtained.  Note,  the  extract  sometimes 
swells  up  enormously  as  it  carbonises  ; in  such  cases  allow  to  cool,  and 
break  down  the  carbonaceous  mass  so  that  it  lies  easily  in  the  dish.  (This 
should  be  done  on  a sheet  of  glazed  paper.) 

Phosphoric  Acid. — Dissolve  the  ash  in  dilute  nitric  acid  (1  to  3),  and 
proceed  with  estimation  by  molybdate  and  “ magnesia  mixture  " (see 
paragraph  820).  The  ash,  less  phosphoric  acid,  gives  “other  mineral 
matter." 


822 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Specific  Rotatory  Power. — Make  up  a 20  per  cent,  solution  of  the  extract, 
and  take  a polarimetric  reading  precisely  as  described  in  paragraph  875  on 
Polarimetric  Determination  of  Dextrin  and  Maltose.  Calculate  out  the 
specific  rotatory  power  both  on  the  whole  and  the  dried  extract  : or,  if 
preferred,  the  rotatory  power  per  gram  of  either  whole  or  dried  extract  may 
be  calculated.  For  the  whole  extract,  with  a 20  per  cent,  solution,  this 
is  the  total  angular  rotation.  Supposing  in  the  case  of  an  extract  the 
total  solid  matter  to  be  80  per  cent.,  and  the  observed  rotation  32-4°,  then 
32-4 

= 1-62°  rotatory  power  per  gram  of  whole  extract  ; 

^ and  ^ ^ = 2-02°  rotatory  power  per  gram  of  dried  extract. 

■'  80 

The  specific  rotatory  power  may  be  obtained  by  multiplying  by  50  in 
each  case. 

Calculation  of  Results — The  reducing  sugar  of  pure  malt  extracts,  ob- 
tained by  concentrating  the  wort  produced  by  total  conversion  of  the  whole 
malt,  consists  principally  of  maltose  On  calculating  it  as  such,  and  adding 
together  the  results  of  the  whole  of  the  determinations  given,  there  is  usually 
an  excess  of  about  5,  or  more,  per  cent,  over  100  : this  is  due  to  some  of  the 
reducing  sugar  being  glucose  instead  of  maltose.  On  the  other  hand,  cold 
water  extracts  of  malt  contain  only  the  pre-existent  sugars  of  malt,  con- 
siderable proportions  of  which  are  glucose  : these,  if  worked  out  as 
maltose,  give  far  too  high  a result,  while  if  calculated  as  glucose,  the  result 
is  too  low.  Again  the  explanation  is  that  in  addition  to  glucoses  there 
is  maltose  also  present.  It  is  frequently  convenient  to  be  able  to  esti- 
mate approximately  the  relative  proportions  of  glucoses  and  maltose,  and 
this  may  be  done  in  the  manner  to  be  now  described.  It  should  first, 
however,  be  mentioned  that  doubtless  malt  extracts  contain  certain  sub- 
stances which  escape  determination  in  all  the  estimations  previously  given  ; 
but  these  cannot  in  any  case  represent  a large  percentage  of  the  whole,  and 
for  present  purposes  may  be  neglected,  the  reservation  being  made  that  a 
small  part  of  the  percentage  returned  as  sugar  may  consist  of  indeterminate 
bodies.  Assuming  that  100,  less  the  cane  sugar,  dextrin,  proteins,  water, 
and  ash,  consists  of  reducing  sugars,  then  we  have 

Total  reducing  sugar  by  difference  in  100  grams  extract  = S. 

Weight  of  cuprous  oxide  precipitated  by  100  grams  extract  = W. 

,,  maltose  in  100  grams  = m. 

„ glucose  „ =g. 

,,  cuprous  oxide  precipitated  by  I gram  of  maltose  = 1-238 

grams. 

,,  cuprous  oxide  precipitated  by  I gram  of  glucose  = 1-983 

grams. 

Then,  m + ^ = S : (Equation  No.  I.) 
and  1-238  m + 1-983  g —W . (Equation  No.  2.) 

From  these  the  values  of  m and  g may  be  determined  thus  : — 

Multiplying  equation  No.  I by  1-983,  and  subtracting  No.  2 from  the 
product,  we  get 

1-983  m + 1-983  g = 1-983  S 
less  1-238  m + 1-983  = W 

0-745  m — 1-983  S — W 

. 1-983  S-W 

“ = 0^4^ 

In  the  same  way  ~ - 

0-745 

or  more  simply,  g = ^ — m. 


ESTIMATION  OF  CARBOHYDRATES.  823 

The  following  figures  were  obtained  in  the  analysis  of  a sample  of  malt 
extract  : — 

S = 60-5.  W 80. 

(1-983  X 60*5)  - 80 

S — m = g,  therefore  60-5  — 53-65  = 6-85. 

The  percentages  of  maltose  and  glucose  are  therefore  respectively  53-65 
and  6-85. 

In  pure  malt  extracts  obtained  by  concentration  of  the  wort  of  the 
entire  malt,  so  mashed  as  to  ensure  the  hydrolysis  of  the  whole  of  the  starch, 
the  percentage  of  glucose  should  not  exceed  from  y to  ^ that  of  maltose. 
W ith  highly  diastatic  extracts  containing  also  a high  percentage  of  proteins, 
the  proportion  of  glucose  is  as  a rule  considerably  greater.  On  comparing 
the  results  thus  obtained  with  the  specific  rotatory  power  of  the  sample, 
it  will  be  found  that  the  glucose  is  almost  entirely  of  the  dextrose  or  right- 
handed  variety. 

The  other  calculations  require  no  detailed  explanation. 

888.  Diastatic  Capacity  on  Lintner’s  Scale. — ^For  brewing  purposes 
diastatic  capacity  is  now  almost  invariably  determined  by  Lintner’s  method, 
and  the  result  expressed  on  Lintner’s  standard,  or  in  “ degrees  Lintner.” 
That  standard  is  : — “ The  diastatic  capacity  of  a malt  is  to  be  regarded  as 
100,  when  0-1  c.c.  of  a 5 per  cent,  solution  reduces  5 c.c.  of  Eehling’s  solu- 
tion.” 

For  the  determination,  “ soluble  starch  ” and  standard  Fehling’s  solu- 
tion are  required.  The  soluble  starch  must  be  prepared  according  to  the 
method  described  in  Chapter  VI.,  page  81.  The  digestion  with  acid  must 
be  allowed  to  proceed  fully  as  long  as  directed,  as,  unless  the  starch  is  ren- 
dered thoroughly  soluble,  it  naturally  gives  apparently  low  diastatic  results. 
It  is  well  during  its  preparation  to  test  a small  portion  at  the  end  of  7 
days  by  thoroughly  washing,  and  then  dissolving  in  boiling  water  : the  solu- 
tion must  be  absolutely  clear  and  limpid.  When  about  to  make  an  estima- 
tion, take  2-2  grams  of  the  soluble  starch  and  dissolve  in  hot  water,  cool,  and 
make  up  to  110  c.c.  If  testing  a malt  or  flour,  take  25  grams  (of  course, 
finely  ground)  and  digest  with  500  c.c.  at  ordinary  temperatures  for  5 
hours.  Filter  until  perfectly  bright.  Arrange  ten  test  tubes  in  a stand,  and 
add  to  each  10  c.c.  of  the  soluble  starch  solution.  Then  to  the  first,  add  0-1 
c.c.  of  the  malt  or  flour  filtrate,  to  the  second  0-2  c.c.,  and  so  on  until  the  last 
receives  1-0  c.c.  Shake  them  thoroughly,  and  allow  the  whole  to  stand  for 
1 hour  in  a water  bath  maintained  at  the  constant  temperature  of  70°  F. 
During  this  time  the  diastase  wiU  have  converted  more  or  less  starch,  accord- 
ing to  its  strength.  Next  add  5 c.c.  of  Fehling’s  solution  to  each  of  the 
tubes,  shake  up,  and  place  the  whole  series  in  boiling  water  for  10  minutes. 
Allow  the  precipitate  to  subside,  and  note  the  condition  of  the  tubes  ; in 
some  the  blue  colour  will  probably  have  entirely  disappeared,  showing 
them  to  be  over  reduced,  while  others  will  still  be  more  or  less  blue.  Select 
the  two  tubes  lying  together  in  which  one  is  slightly  over  and  the  other 
slightly  under  reduced.  The  number  of  c.c.  required  to  give  exact  reduc- 
tion will  lie  between  these,  and  should  be  judged  according  to  which  it 
appears  the  nearest.  Thus,  suppose  as  nearly  as  possible  it  is  exactly  mid- 
way between  Nos.  5 and  6 , then  the  quantity  of  malt  solution  may  be  taken 
as  0-55  ; while  if  No.  5 is  full  yellow,  while  No.  6 is  only  very  faintly  blue, 
then  one  would  give  the  quantity  as  0-58  or  0-59,  according  to  how  near  in 
one’s  judgment  it  appeared  to  be  to  the  0-6.  With  a little  practice  .one  soon 
gets  able  to  judge  very  closely  this  second  decimal.  If  the  result  of  a test 


824 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


gives  0-5  c.c.  as  the  quantity  of  malt  solution  required,  then  the  sample  is 
evidently  only  one -fifth  of  the  standard  strength  of  100,  or 

^ ~ Lintner  as  diastatic  capacity. 

But  there  is  a certain  amount  of  reducing  sugar  extracted  from  malt 
by  cold  water,  and  this  also  helps  to  reduce  the  Fehhng’s  solution.  The 
amount  of  this  is  determined  in  the  following  manner  : — Take  5 c.c.  of  Feh- 
ling’s  solution,  10  c.c.  of  starch  solution,  and  10  c.c.  of  water,  and  raise  to 
the  boiling  point  in  a small  flask.  To  this  add  the  malt  solution  from  a 
burette  until  the  Fehling  is  exactly  reduced  ; then  determine  the  apparent 
diastatic  capacity  of  this  solution.  Supposing  that  7 c.c.  have  been  run  in 
in  order  to  reduce  the  Fehling,  then 

0 1 X 100  _ correction  for  reducing  sugars  extracted  from  the  malt. 


For  malts  the  correction  1-4  may  usually  be  taken  as  a constant,  and 
the  above  results  become 

20  - 1-4  = 16-8°  Lintner. 

Working  with  malt  extracts,  the  value  of  the  correction  becomes  much 
higher,  and  must  be  determined  for  each  individual  sample  analysed,  and 
preferably  before  the  diastase  estimation.  Take  a 5 per  cent,  solution  of 
the  extract,  boil,  make  up  to  original  volume,  filter,  and  titrate  on  Fehhng 
and  starch  as  above  described.  In  an  actual  analysis  1-25  c.c.  of  the  5 per 
cent,  solution  were  required  ; the  correction  therefore  becomes 


0*1  X 100 
1-25 


= 8*0°  correction  for  reducing  sugars  present. 


From  this  it  will  be  seen  that  the  tenth  tube  in  the  diastase  determination 
is  nearly  reduced  by  the  sugars  present  alone.  The  diastase  estimation 
should  now  be  made  : this  in  the  sample  in  question  amounted  to  0-73  c.c.  ; 
then 

^ ^0^3^^^  ~ 13-7°  apparent  diastatic  capacity. 

13*7  — 8-0  = 5-7°  Lintner,  real  diastatic  capacity. 


In  malt  extracts  and  other  diastatic  preparations  the  diastatic  capacity 
varies  very  widely,  and  either  none  or  all  of  the  series  may  be  completely 
reduced.  In  the  former  case  the  diastatic  capacity  must  be  less  than  10 
minus  the  correction.  Make  another  diastase  estimation  with  a 25  per 
cent,  solution  of  the  extract,  and  multiply  the  correction  by  5 ; the  solution 
being  of  5 times  strength,  the  net  figure  thus  obtained  for  real  diastatic 
capacity  must  be  divided  by  5 in  order  to  give  degrees  Lintner.  Should 
there  be  no  reduction  in  any  of  the  tubes,  the  diastatic  capacity  must  be 
less  than  2 minus  the  correction,  which  practically  amounts  to  its  total 
absence. 

On  the  other  hand,  the  whole  of  the  series  may  be  reduced,  showing  that 
the  diastatic  capacity  is  more  than  100  minus  the  correction.  In  this  case 
make  up  a 0-625  per  cent,  solution,  and  use  it  for  a diastase  estimation  ; 
multiply  the  result  by  8,  and  take  the  correction  as  | that  with  the  5 per 
cent,  solution.  The  following  is  the  result  of  an  estimation  on  a diastase 
preparation  made  by  the  authors  ; — 

Correction  for  reducing  sugars  on  5 per  cent,  solution  = 8-2°. 

All  tubes  were  reduced. 

With  0*625  per  cent,  solution,  reduction  effected  by  0*42  c.c. 

^ = 190*5°  apparent  diastatic  capacity. 


ESTIMATION  OE  CARBOHYDRATES. 


825 


190-5  — = 189-48°  Lintner,  real  diastatic  capacity. 

The  three  diastase  tests  made  in  this  manner  give  a total  range  of  from 
2°  to  800°  Lintner,  and  with  each  test  overlapping  the  other. 

In  comparing  extracts  for  bread-making  purposes,  it  is  sometimes 
advisable  to  also  test  on  starch  paste  ; in  that  case  proceed  exactly  as 
with  soluble  starch,  except  that  ordinary  starch  is  substituted  and  carefully 
gelatinised  without  ‘‘  balling.” 

889.  Diastase  Tests  on  Flours. — ^These  may  be  made  by  taking  a given 
quantity  of  the  extract,  mixing  with  flour  and  water,  and  digesting  for  a 
given  time  at  some  fixed  temperature.  The  amount  of  matter  dissolved 
and  maltose  produced  may  then  be  determined  by  direct  estimations.  Full 
particulars  of  such  determinations  are  given  in  paragraph  890. 

Baking  tests  afford  the  most  valuable  means  of  testing  diastatic  value 
of  extracts  for  bakers.  These  tests  should  be  made  as  directed  in  Chapter 
XXVI.,  paragraph  810,  with  the  extract  added  to  the  water.  It  is  well  to 
take  the  uniform  quantity  of  the  extract  equivalent  to  1 lb.  to  the  sack,  2 
grams  = 20  c.c.  of  a 10  per  cent,  solution  (the  quantity  of  water  used  for 
dough-making  must,  of  course,  be  diminished  by  the  20  c.c.  taken  with  the 
extract).  Prepare  100  c.c.  of  the  10  per-cent,  solution,  place  half  of  it  in  a 
flask,  weigh,  boil  for  5 minutes,  and  make  up  to  the  original  weight  with 
water,  and  call  this  No.  2.  Prepare  duplicate  loaves,  using  the  No.  1 or 
unheated  extract  solution  in  the  first,  and  No.  2 or  boiled  solution  in  the 
second.  Make  up  also  a plain  loaf.  No.  3,  with  the  same  flour  ; compare 
carefully  the  character  of  the  three  for  volume,  colour,  pile,  moistness, 
flavour,  and  any  other  points  of  interest  to  the  baker.  No.  2 will  have  had 
its  diastase  killed,  and  will  contain  only  such  maltose  and  other  bodies  as 
are  contained  in  the  extract  ; No.  1 will  contain  in  addition  all  such  sub- 
stances as  have  been  produced  by  the  diastatic  action  of  the  extract  itself. 

If  wished,  determinations  may  be  made  of  soluble  extract  and  maltose 
in  each  of  the  loaves.  The  results  may  then  be  returned  as  shown  in  blank 
below  : — 

Soluble  Extract.  Maltose. 

Normal  Quantities  in  Plain  Bread,  deter- 
mined in  No.  3 . . . . 

Quantities  added  in  Extract,  being 

difference  between  Nos.  2 and  3 . . ......  

Quantities  produced  by  Diastatic  Action, 

being  difference  between  Nos.  1 and  2 

Total  . . . . 


In  this  way  any  extract  can  at  once  be  valued  both  for  added  and  pro- 
duced maltose  and  other  substances. 

890.  Experimental  Comparison  of  Diastase  Determinations. — ^In  order 
to  institute  a comparison  between  results  obtained  by  Lintner’s  method 
and  the  amount  of  change  produced  both  in  flour  digestion  and  ordinary 
baking,  the  following  experiments  were  made  : — 

Lintner’ s Determinations. — First,  four  extracts  were  selected,  one  of 
which  (No.  I.)  had,  according  to  Lintner,  a low  diastatic  value  ; another 
(No.  II.)  was  remarkably  high  ; while  the  third  gave  practically  no  read- 
ing on  Lintner ’s  scale.  The  fourth  was  another  sample  from  the  same 
source  as  No.  I.,  but  from  a more  active  malt,  and  manufactured  at  a lower 
temperature.  The  results  are  in  each  case  tabulated. 


826 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No.  I.  Extract,  Diastatic  Capacity  ..  1-2°  Lintner. 

No.  II.  „ „ . . 354° 

No.  III.  „ „ . . 0-8° 

No.  IV.  ,,  ,,  not  accurately  determined,  but 

slightly  higher  than  No.  I. 

Another  sample  of  No.  II.,  same  type,  gave  320°  Lintner  on  being  tested. 
Duplicates  of  Nos.  I.  and  III.  were  in  absolute  agreement  with  those  quoted. 

Flour  Digestion  Tests. — A 0-5  per  cent,  solution  was  prepared  of  each 
extract  ; a half  of  this  was  raised  to  the  point  of  actual  ebullition,  cooled, 
and  loss  of  weight  made  up  with  distilled  water.  The  first  part  is  called 
“ Active  Extract,’’  and  the  second  “ Killed  Extract.”  Of  each,  100  c.c. 
( = 0*5  gram  extract)  was  taken,  added  to  25  grams  of  flour  in  a corked 
flask,  shaken  vigorously,  and  all  digested  together  for  4 hours  in  a water 
bath  at  140-150°  F.  A blank  experiment  was  also  made  with  100  c.c. 
water  and  25  grams  of  flour  only.  The  contents  of  the  flasks  were  filtered, 
and  “ soluble  extract  ” and  maltose  determined  in  the  clear  filtrate.  The 
following  are  the  results,  expressed  in  percentages  of  the  flour  used. 


Soluble  Extract  and  Maltose. 


• 

Percentage  of  Extract, 
less  Total  Solids  in  Malt 

Percentage  of 
Soluble  Extract 
on  Flour  used. 

Percentage  of 

Extract  and  Percentage 

No.  of  Extract. 

Extract,  less  Total 
Solids  in  Malt 

of  Extract  with  Plain 
Flour  and  Water  = 

Extract =1-6 

l-6+24-4=26-0,  being 
Extract  due  to  Diastatic 

Action. 

I.  Active 

26-28 

24-68 

0-28 

I.  Killed 

24-60 

23-00 

Minus  quantity. 

II.  Active 

48-04 

46-44 

22-04 

II.  Killed 

37-32 

35-72 

11-32 

III.  Active 

31-52 

29-92 

5-52 

I III.  Killed 

27-08 

25-48 

1-08 

IV  Active 

34-52 

32-92 

8-52 

IV.  Killed 

28-76 

27-16 

2-76 

V.  Flour  and  Water  only 

24-40 

— 

— 

Percentage  of  Maltose 

Percentage  of 
Maltose. 

Percentage  of 
Maltose,  less  that 
in  added  Malt 
Extract,  say  1-2. 

less  that  in  Malt  Ex- 
tract and  that  resulting 
from  Flour  only  = 
l-2-l-8-88=10-08,  being 
Maltose  due  to  Diastatic 

Action. 

I.  x^ctive 

23-75 

22-55 

12-47 

I.  Killed 

14-54 

13-34 

3-26 

II.  Active 

36-83 

35-63 

25-55 

1 II.  Killed 

25-52 

24-32 

14-24 

III.  iVctive 

19-06 

17-86 

7-78 

III.  Killed 

14-86 

13-66 

3-58 

IV.  xWtive 

22-61 

21-41 

11-33 

IV.  Killed 

17-12 

15-92 

5-84 

V.  Flour  and  Water  only 

i 

8-88 

8-88 

Baking  Tests. — Baking  tests  were  then  made  with  the  first  three  extracts, 
the  method  being  that  described  in  the  preceding  paragraph,  except  that 
tlie  “ killed  ” solutions  were  sim]fly  raised  to  actual  ebullition,  without  con- 
tinuing the  boiling  for  the  5 minutes  as  there  directed.  The  quantity  of 


ESTIMATION  OF  CARBOHYDRATES. 


827 


■extract  in  each  case  was  equivalent  to  1 lb.  to  the  sack  of  flour.  The  follow- 
ing are  the  results  of  various  determinations  made  on  the  baked  loaves  : — 

Analyses  of  Baked  Loaves. 


No.  of  Extract. 

Water. 

Soluble 

Extract. 

Maltose. 

Dextrin. 

I.  Active.  . 

43-81 

6-12 

5-41 

3-25 

I.  Killed 

42-24 

5-62 

3-31 

2-75 

II.  Active.  . 

41-71 

9-22 

6-22 

4-90 

II.  Killed 

42-90 

5-90 

3-64 

2-90 

III.  Active.  . 

42-21 

5-04 

4-70 

2-45 

III.  Killed 

42-74 

4-94 

3-79 

2-45 

V.  Plain  Loaf 

42-25 

4-74 

3-15 

2-40 

From  these  data  the  amount  of  each  constituent  may  be  calculated  into 
quantity  present  in  plam  loaf,  that  added  in  “ killed  ” extract,  and  that 
produced  by  diastatic  action.  When  thus  treated  the  results  assume  the 
following  form  : — 


Source  of  Each  Constituent  in  Baked  Loaves. 


Constituent  and  No.  of  Extract. 

Normal 

Plain 

Bread. 

Quantity 
due  to 
“ Killed” 
Extract. 

Quantity 
due  to 
Diastatic 
Action. 

Total 

Quantity. 

1 

1 

4-74 

0-88 

0-50 

6-12 

Soluble  Extract  \ 

II 

4-74 

1-16 

3-32 

9-22 

1 

. Ill 

4-74 

0-20 

0-10 

5-04 

I 

r I 

3-15 

0-16 

2-10 

5-41 

Maltose  . . . 

II 

3-15 

0-49 

2-58 

6-22 

1 

Im 

3-15 

0-64 

0-91 

4-70 

1 

ri 

2-40 

0-35 

0-50 

3-25 

Dextrin . . . 

II 

2-40 

0-50 

2-00 

4-90 

1 

Ill 

2-40 

0-05 

0-00 

2-45 

Reviewing  these  results,  the  following  is  noticed  in  the  flour  digestions  : — 
No.  I.  extract,  both  active  and  killed,  gave  abnormally  low  soluble  extracts, 
while  No.  I.  active  yielded  an  exceptionally  high  maltose  result.  There 
were  no  duplicates  made  of  these,  but  the  results  of  determinations  in  the 
baked  loaves  are  in  absolute  agreement  with  them  ; thus,  in  the  digested  flour 
the  maltose  is  0-90  of  the  total  soluble  extract,  while  the  maltose  in  the 
bread  is  0-88  of  the  soluble  extract  obtained.  In  each  case  except  No.  I. 
the  killed  extract  still  exhibited  considerable  amylolytic  activity. 

Turning  to  the  bread  results,  the  water  was  determined  as  a check 
on  the  constitution  of  the  loaves,  and  not  as  a measure  of  the  yielding  power 
of  the  flour.  There  is  in  the  case  of  each  constituent  a greater  quantity 
present  in  “ killed  extract  treated  loaves  than  in  that  which  was  perfectly 
plain,  a quantity  partly,  but  not  entirely,  due  to  the  actual  matter  intro- 
duced by  the  extract  itself  (a  lb.  of  extract  per  sack  equals  approximately 
0-25  per  cent,  on  the  baked  bread).  This  shows  that  malt  extracts  contain 
a hydrolysing  constituent,  the  activity  of  which  is  not  destroyed  by  momen- 
tary boiling.  In  each  case,  and  with  each  constituent  estimated,  except 
dextrin  in  No,  III.,  there  is  an  increase  due  to  amylolytic  action.  In  No.  II., 


828 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


which  gave  by  far  the  highest  result  on  Lintner’s  scale,  there  is  also  the 
highest  amount  of  change  in  the  baked  loaf,  but  in  nothing  like  the  same 
proportion.  The  dextrins  are  obtained  by  precipitation  with  alcohol, 
but  are  not  corrected  for  proteins.  The  reducing  sugars  are  throughout 
reckoned  as  maltose  : but  the  sum  of  the  maltose  and  uncorrected  dextrin 
is  uniformly  in  excess  of  the  total  soluble  extract.  No  specific  researches 
have  been  made,  but  the  probable  cause  is  that  some  of  the  sugar  is  "glucose. 

891.  Adulterations  of  Malt  Extract.— Malt  extract  may  be  adulterated 
either  with  molasses  (treacle)  or  glucose  syrups.  The  former  of  these  may 
be  detected  by  the  large  increase  in  the  quantity  of  cane  sugar  present, 
as  molasses  contains  from  35  to  48  per  cent,  of  sucrose.  It  also  usually  con- 
tains considerable  amounts  of  glucose.  The  so-called  sirupy  “ glucoses 
contain,  when  conversion  has  been  arrested  at  the  minimum  point,  large 
quantities  of  dextrin  and  maltose,  and  therefore  in  that  particular  closely 
resemble  malt  extracts.  Commercial  “ glucose  ’’  is,  however,  practically 
devoid  of  protein  constituents,  and  in  this  way  is  detected  when  used  as  an 
adulterant  of  malt  extract.  A polar imetric  reading  affords  a valuable 
indication  as  to  the  purity  of  malt  extracts.  The  following  table  gives  the 
result  of  a number  of  such  readings  calculated  to  angular  rotation  per  gram 
of  undried  substance  in  100  c.c.,  the  observations  being  made  in  a 2 deci- 
metre tube. 


POLAKIMETRIC  ESTIMATIONS  ON  MaLT  EXTRACT,  ETC. 


No. 

1.  Malt  Extract  of  known  purity,  tested  March,  1893 

2.  Same  make  of  Extract,  sample  taken  April,  1893 

3.  Sample  of  suspected  Malt  Extract,  very  light  in  colour 

4.  Second  sample  of  suspected  Malt  Extract 

5.  Lyle’s  Golden  Syrup,  obtained  personally  by  author  . 

6.  No.  1 Syrup,  lightest  colour 

7.  No.  2 ,,  intermediate 

8.  No.  3 ,,  darkest 

9.  “ Glucose  ” Syrup  (White  Confectioners’ 

10.  Mixture  made  personally  by  authors — 

No.  1,  7*07  grams 


) From  same 
1 manufacturers 


No.  6,  4*79 


1^' 


11. 


Calculated  Rotatory  Power  from  quantities  taken 
Mixture  made  personally  by  authors — • 

No.  1,  7*07  grams  ) 

No.  9,  6-26  „ I 

Calculated  Rotatory  Power  from  quantities  taken 


Rotatory  Power 
per  Gram. 

. 1-59° 

. 1-52° 

1-99° 
1-79° 

0- 52° 

1- 05° 
0-81° 
0*52° 

2- 30° 


1-33° 

1-33° 

1-85° 

1-89° 


Both  the  suspected  samples  had  abnormally  high  rotatory  powers,  and 
were  probably  adulterated  with  ‘‘  glucose  ” syrup ; they  agree  approxi- 
mately with  No.  11.  For  comparison  with  the  rotatory  powers  of  the  pure 
substances  refer  to  paragraph  874. 


892.  Baking  Powders,  Analysis  of. — ^Crampton,  in  a U.S.  Department 
of  Agriculture  Bulletin,  gives  a detailed  method  of  analysis  of  these,  of 
wliich  the  following  is  a modification.  In  examining  Baking  Powders, 
a qualitative  analysis  serves  to  recognise  whether  the  acid  constituent  is 
tartaric,  phosphoric,  or  sulphuric  acid,  or  a mixture  of  two  or  more  of  these. 
Tlie  alkalinity  of  the  aqueous  solution  should  be  tested  as  a guide  to  the 
amount  of  excess  of  carbonate  employed.  The  following  are  among  some 
of  the  more  important  estimations  which  should  be  made  : — 

(1)  Carbon  Dioxide. — This  is  the  measure  of  the  essential  strength  of 


ESTIMATION  OE  CARBOHYDRATES. 


829 


the  powder,  as  its  value  depends  on  the  quantity  of  this  gas  liberated  by 
the  powder  when  used.  Usually  the  total  and  available  carbon  dioxide  are 
both  measured,  as,  through  deficiency  in  acid  ingredients,  the  whole  of  the 
carbonates  are  not  always  decomposed  when  the  powder  is  employed  for 
baking  purposes.  The  total  carbon  dioxide  is  obtained  by  treatment  with 
excess  of  acid  ; the  available,  by  adding  water  and  heating  in  as  nea-rly  as 
possible  the  same  manner  as  in  actual  baking. 

Many  of  the  recognised  forms  of  apparatus  for  the  measurement  of 
carbon  dioxide  may  be  used  for  this  purpose.  Thus,  the  well-known 
Schroedter  may  be  employed,  in  Avhich  the  liberating  acid  and  drying  tubes, 
etc.,  are  all  self-contained  within  the  same  apparatus,  together  with  the 
powder,  which  is  weighed  before  and  after  the  acid  and  powder  act  on  each 
other.  The  loss  of  weight  is  the  measure  of  the  amount  of  carbon  dioxide 
evolved.  In  using  an  apparatus  of  this  form,  from  I to  2 grams  of  the 
l^owder  is  weighed  out  and  transferred  to  the  flask  of  the  Schroedter,  previ- 
ously charged  with  dilute  liberating  sulphuric  acid,  and  concentrated  acid 
for  drying  the  escaping  gas  ; weigh  the  whole  apparatus,  and  allow  the 
acid  to  enter  very  slowly.  Toward  the  close  of  the  reaction  heat  very  care- 
fully, and  add  the  acid  finally  to  powder  when  hot.  Care  must  be  taken 
that,  owing  to  the  gelatinisation  of  the  starch,  the  whole  mass  does  not  boil 
over,  and  thus  vitiate  the  determination.  Finally  draw  air  through  in  the 
usual  manner,  and  weigh  with  the  ordinary  precautions.  Water  must  not 
be  added  to  the  powder  before  the  reaction  is  started.  To  estimate  avail- 
able carbon  dioxide  proceed  in  the  same  manner,  except  that  distilled  water 
must  be  used  for  liberating  purposes,  instead  of  dilute  acid.  Add  the  water 
slowly,  and  at  the  close  bring  it  as  nearly  as  possible  to  the  boiling  point, 
and  maintain  it  at  that  temperature  for  15  minutes,  gently  agitating  the 
apparatus  occasionally. 

For  technical  purposes,  the  carbon  dioxide  can  be  estimated  with  suffi- 
cient 'accuracy  by  a modification  of  the  yeast  apparatus  described  on  page 
199,  the  gas  being  measured  volumetrically.  It  may  be  mentioned  that 
I gram  of  sodium  bicarbonate,  NaHCOs,  yields  on  treatment  with  excess'of 
acid  0-524  gram  of  carbon  dioxide,  being  267  cubic  centimetres  at  0°  C.,  or 
286  at  20°  C.  Further,  286  c.c.  = 17-4  cubic  inches. 

Take  a 6 ounce  flask  and  fit  it  with  a good  india-rubber  cork,  pass 
through  the  latter  a right-angled  delivery  tube,  and  also  a thistle  funnel, 
provided  with  bulb  of  about  50  c‘.c.  capacity,  and  a glass  stopcock.  Arrange 
the  flask  on  a piece  of  wire  gauze  on  the  retort  stand,  and  connect  it  up  by 
means  of  a short  length  of  india-rubber  tubing  to  the  end,  c,  of  the  T -piece. 
Fig.  21.  Stand  the  gas  collecting  jar,  /,  in  a deep  vessel  of  cold  solution  of 
calcium  chloride,  sp.  gr.  1-4,  preferably  using  for  this  purpose  a cylinder  of 
glass.  Weigh  out  25  grams  of  the  baking  powder  and  place  it  in  the  flask, 
connect  up  the  apparatus  and  exhaust  the  air  until  the  liquid  stands  at 
zero  in  the  glass  jar.  Fill  the  bulb  of  the  thistle  funnel  with  10  per  cent, 
sulphuric  acid,  turn  the  stopcock  very  gently,  so  as  to  allow  the  acid  to 
enter  drop  by  drop.  Great  care  must  be  exercised  in  opening  this  stop- 
cock, as  otherwise  the  column  of  water  in  the  gas  jar  will  draw  the  whole 
of  the  acid  out  of  the  funnel,  and  allow  the  apparatus  to  completely  fill  with 
air.  W hen  the  reaction  is  over,  gently  heat  the  flask  until  the  whole  of  the 
carbon  dioxide  is  set  free.  Allow’^  the  apparatus  to  cool,  and  read  off  the 
volume  of  carbon  dioxide  liberated.  Make  a deduction  for  the  volume  of 
acid  which  has  been  let  in  from  the  funnel  ; this  is  easily  done  by  measuring 
once  for  all  the  amount  it  delivers.  If  results  are  immediately  w'anted,  the 
apparatus  may  be  cooled  by  pouring  a little  w^ater  over  it.  To  determine 
available  carbon  dioxide  proceed  in  exactly  the  same  w'ay,  except  that  w^ater 
must  be  used  instead  of  acid  in  the  funnel,  and  gentle  boiling  should  be 


830 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


employed  at  the  termination  of  the  reaction  for  about  15  minutes. 
Precisely  the  same  remarks  apply  to  the  limits  of  accuracy  of  these  tests^ 
as  are  made  on  the  use  of  the  apparatus  for  yeast  testing  in  paragraphs^ 
364-5. 

(2)  Phosphoric  Acid. — Weigh  about  0-5  gram,  ignite  carefully,  treat 
with  nitric  acid,  dilute  and  filter.  Precipitate  with  ammonium  molyb- 
date, digest,  filter,  and  wash  with  dilute  nitric  acid  or  ammonium  nitrate 
solution.  Dissolve  the  precipitate  in  ammonia,  precipitate  with  magnesia 
mixture,  filter,  wash  with  dilute  ammonia,  ignite,  and  weigh. 

(3)  Tartaric  Acid. — Weigh  out  5 grams  of  the  powder,  transfer  to  a 500 
c.c.  flask,  and  add  100  c.c.  of  water  and  15  c.c.  strong  hydrochloric  acid. 
When  all  action  has  ceased,  makeup  with  water  to  500  c.c.,  and  allow  starch 
to  subside.  Filter  and  take  50  c.c.  of  filtrate  and  add  thereto  10  c.c. 
of  solution  of  potassium  carbonate,  containing  300  grams  K2CO3  per  litre  ; 
boil  for  half  an  hour  and  filter  into  a porcelain  dish,  concentrate  filtrate  and 
washings  down  to  10  c.c.,  add  gradually  and  with  constant  stirring  4 c.c. 
glacial  acetic  acid,  and  then  100  c.c.  of  95  per  cent,  alcohol,  stirring  the  liquid 
until  the  precipitate  floating  in  it  assumes  a crystalhne  appearance.  After 
standing  some  hours,  filter  and  wash  with  alcohol  until  entirely  free  from 
acetic  acid.  Transfer  filter  and  precipitate  to  a beaker,  add  water  and  boil. 
Titrate  the  resulting  solution  with  decinormal  soda  and  phenolphthalein  — 
1 c.c.  of  alkali  corresponds  to  0-0188  grams  of  potassium  bitartrate  (cream 
of  tartar),  or  0-0150  grams  of  tartaric  acid. 

(4)  Sulphuric  Acid. — This  may  be  estimated  without  previous  ignition 
of  the  powder.  Weigh  out  0-5  gram  and  digest  in  a beaker  with  strong 
hydrochloric  acid  until  the  whole  of  the  powder  including  the  starch  is- 
dissolved  ; then  dilute  with  water,  raise  to  near  boiling,  and  add  barium 
chloride  in  slight  excess,  allow  to  stand  12  hours,  filter  and  weigh. 

(5)  Alumina. — This  body  being  the  base  of  the  alums,  its  determination 
should  be  made  in  all  cases  where  sulphuric  acid  is  found  to  be  present. 
In  the  absence  of  phosphoric  acid,  from  0-5  gram  to  1 -0  gram  may  be  ignited, 
extracted  with  acid,  evaporated  to  complete  dryness  to  separate  silica, 
treated  with  strong  hydrochloric  acid,  diluted  with  water,  and  alumina 
precipitated  with  ammonia,  washed,  dried,  ignited,  and  weighed.  In  the 
presence  of  both  phosphoric  acid  and  alum,  the  following  method  may  be 
adopted  : — Weigh  out  5 grams  of  the  powder  in  a platinum  dish,  heat 
until  thoroughly  carbonised,  digest  with  strong  nitric  acid,  dilute,  and  filter 
into  a 500  c.c.  flask.  Wash  the  residue  slightly,  transfer  the  filter  and  all 
back  into  the  platinum  dish,  dry,  burn  to  white  ash,  add  mixed  potassium 
and  sodium  carbonates,  and  fuse.  Take  up  with  nitric  acid,  evaporate 
to  complete  dryness,  again  take  up  with  nitric  acid,  dilute,  and  filter 
into  the  500  c.c.  flask.  The  flask  will  now  contain  both  series  of  fil- 
trates ; make  up  to  the  mark  with  water.  Take  100  c.c.  and  precipitate 
with  ammonium  molybdate  and  nitric  acid,  digest  and  filter.  In  filtrate, 
determine  alumina  by  precipitation  with  ammonia,  and  estimate  phosphoric 
acid  in  the  precipitate  in  the  usual  manner. 

(6)  Starch. — This  may  be  determined  by  treatment  with  dilute  acid 
so  as  to  effect  conversion  into  glucose,  and  then  estimating  by  Fehling’s 
solution.  A rough  determination  may  be  made  by  adding  water  to  the 
powder,  and  after  cessation  of  the  reaction  washing  several  times  on  a filter, 
first  witli dilute  hydrocldoric  acid  (5  per  cent.)  and  then  with  water.  The 
residue  is  transferred  to  a platinum  dish,  evaporated  to  complete  dryness  at 
100°  C.  and  weighed,  subsequently  to  which  the  ash  is  determined  and  sub- 
tracted from  the  weight  at  100°  C. — the  remainder  is  taken  as  starch. 

Other  determinations  may  be  made,  but  the  above  are  the  most 
important. . 


CHAPTER  XXX. 


BREAD  ANALYSIS. 

893.  Principles  of  Bread  Analysis. — ^Having  described  the  methods  to  bo 
employed  for  the  determination  of  the  various  constituents  of  wheat  and 
flour,  a short  description  must  now  be  given  of  bread  analysis. 

Many  of  the  properties  by  which  good  bread  is  distinguished  from  bad 
scarcely  come  within  the  range  of  purely  chemical  analysis.  Among  these 
are  the  colour,  texture,  “ piling,’"  odour  and  flavour  of  the  crumb,  and  the 
colour  and  thickness  of  the  crust.  In  the  kind  of  bread  known  technically 
as  ‘‘  crumby  ” bread,  the  colour  and  texture  of  the  joint  between  two  loavef^ 
is  to  be  observed.  The  analyst,  in  reporting  on  bread,  should  examine 
the  loaf  so  far  as  the  above  characteristics  are  concerned,  and  include  his 
opinion  on  the  same  in  his  report.  In  judging  each,  he  may  adopt  the  plan 
of  employing  a series  of  numbers,  say  1 to  10,  and  using  the  lowest  number 
for  the  worst  possible  grade,  and  the  highest  for  the  very  best.  Or  he  may 
use  instead  the  terms  V.  B.,  very  bad  ; B,  bad  ; I,  indifferent  ; M,  moderate  ; 
G,  good  ; V.  G.,  very  good ; E,  excellent.  In  either  case  the  same  term 
must,  so  far  as  is  possible,  be  applied  to  the  same  grade  of  quality,  whether 
of  texture,  colour,  or  other  characteristic. 

894.  Colour. — 'The  baker’s  use  of  this  term  involves  a contradiction  ; 
it  is  the  custom  of  the  trade  to  speak  of  a loaf  as  “ having  no  colour  ” when 
a dark  brown,  while  in  the  purest  white  loaf  the  colour  is  said  to  be  “ high.” 
This  is,  of  course,  exactly  opposite  to  the  correct  use  of  these  terms,  for  white 
is  strictly  no  colour,  while  a yellow  or  brown  body  is  strongly  coloured. 
It  would  be  a better  plan  if  the  respective  terms  were  “ lightly  coloured  ” 
and  “ strongly  or  deeply  coloured.”  Judging  colour  by  itself  alone,  the 
loaf  should  be  a very  light  yellow  or  creamy  tint,  approaching  almost  to 
whiteness.  This  colour  is  selected  because  the  authors  are  of  opinion  that, 
judging  bread  by  the  eye  alone,  the  slightest  yellow  hue  is  more  agreeable 
than  an  absolute  snowy  whiteness.  The  latter,  perhaps  from  its  frequent 
association  with  absence  of  flavour,  is  unpleasant. 

It  must  be  remembered  that  colour,  etc.,  are  matters  of  individual  taste 
and  opinion,  and  therefore  that  each  individual  has  his  own  standard  of 
comparison.  In  forming  a judgment  one  naturally  most  appreciates  that 
in  accordance  with  one’s  own  standard  ; it  does  not  necessarily  folloAv  that 
such  judgment  shall  absolute^  agree  with  that  of  another  person.  It  is  a 
well-lmown  fact  that  in  different  localities  the  standard  of  taste  in  these 
matters  varies. 

For  actual  measurement  of  bread  colour,  the  method  of  testing  with 
the  tintometer  should  be  employed  ; or  baked  loaves  may  be  compared 
against  those  similarly  prepared  from  standard  samples  of  flour. 

895.  Texture. — ^The  texture  of  a loaf  is  best  observed  by  cutting  it  in 
two  with  a very  sharp  knife.  There  should  be  an  absence  of  large  cavities, 
and  also  of  dry  lumps  of  flour.  The  honeycombed  structure  of  the  bread 
should  be  as  even  as  possible.  The  bread  should  not  break  away  easily  in 
crumbs,  but  should  be  somewhat  firm.  On  being  gently  pressed  with  the  fin- 
ger the  bread  should  be  elastic,  and  should  spring  back  without  showing  a 
mark  on  the  pressure  being  removed. 

831 


832 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


896.  Proof. — ^Like  many  other  trade  terms,  this  is  used  in  a somewhat 
different  sense  in  different  localities.  It  usually  has  reference  to  the  degree 
of  rise  in  volume  a loaf  undergoes  before  being  put  in  the  oven.  In  this 
sense,  by  a well-proved  loaf  is  understood  one  that  has  risen  well,  both  in 
the  dough  stage  and  after  being  placed  in  the  oven.  It  almost  goes  without 
saying  that  in  judging  the  quality  of  a loaf  the  baker  likes  it  to  be  as  large  as 
possible.  Such  an  opinion  is  a sound  one  where  size  of  the  loaf  is  combined 
with  evenness  of  texture,  and  is  not  the  result  of  the  presence  of  large  cavities 
in  the  bread.  The  opposite  of  a well-proved  loaf  is  a heavy  one  ; hence  this 
matter  of  the  proof  of  a loaf  is  of  importance.  The  loaf  which  in  this  particu- 
lar looks  the  best  is  that  which  is  most  digestible  and  wholesome. 

There  is  another  sense  in  which  the  term  “ proof  ” is  applied  : thus, 
two  loaves  may  have  risen  equally  well,  and  yet  the  one  be  regarded  as  being 
better  proved  than  is  the  other.  The  well-proved  loaf  is,  under  these  cir- 
cumstances, viewed  as  that  in  which  fermentation  has  proceeded  until  the 
flavour  of  the  bread  (the  bouquet,  if  the  term  may  be  borrowed)  has  de- 
veloped to  the  greatest  perfection.  The  well-proved  loaf  will  be  sweet 
and  nutty  in  flavour,  and  have  all  the  characteristics  of  being  thoroughly 
cooked  ; the  badly-proved  loaf  will  be  lacking  in  flavour,  and  have  what 
for  want  of  a better  expression,  may  be  called  a “ raw  ’’  taste.  Undoubtedly, 
this  use  of  the  term  “ proving  ’’  refers  to  a difference  which  does  exist  in 
the  two  loaves,  a difference  which  in  all  probability  is  due  to  the  more  or 
less  perfect  proteolytic  action  of  the  yeast  on  the  proteins  during  fermenta- 
tion. The  term  proof  is  therefore  used  in  two  different  senses,  one  as  a 
measure  of  the  volume  of  the  loaf,  the  other  as  an  indication  of  the  extent 
to  which  the  changes  accompanying  fermentation  have  proceeded. 

897.  Pile. — ^This  is  essentially  a term  referring  to  the  texture  of  the 
crumb  of  bread,  and  is  doubtless  derived  from  the  use  of  the  word  “ pile 
as  indicating  the  texture  of  the  surface  of  velvet.  In  a letter,  of  which  the 
following  is  the  substance,  Mr.  W.  A.  Thoms  explained  to  one  of  the  authors 
the  exact  sense  in  which  the  term  is  used  in  Scotland  : — “ By  a well-piled 
loaf  we  do  not  understand  a loaf  well  risen.  Pile  is  the  gloss  of  the  outside 
skin,  or  crumb  of  close-packed  bread,  and  the  more  unbroken  the  skin,  the 
more  silky  in  feel  and  glossy  in  sheen,  the  higher  we  rank  the  pile.  Un- 
doubtedly a well-piled  loaf  must  also  be  a well-risen  loaf.  They  have  that 
in  common,  but  a well-risen  loaf  may  be  ragged,  broken-skinned  and  dark, 
without  being  over  proved  ; such  a loaf  we  call  coarse,  and  say  it  has  a bad 
or  no  pile.  Proof,  in  dough  or  baked  bread,  refers  to  volume  or  size.  These 
qualities , proof  and  pile,  are  due  to  the  same  factor,  carbon  dioxide,  acting 
on  and  distending  the  gluten,  and  it  is  the  condition  of  the  gluten  at  the 
time  in  the  oven,  when  the  dough  is  passing  into  bread,  that  determines  the 
pile.  The  condition,  good  or  bad,  of  the  gluten  in  this  transition  state  may 
be  due  to  the  condition  of  the  flour,  the  proportion  of  gluten  it  contains,  or 
to  the  action  of  the  yeast  and  its  bye-products  on  the  gluten  during  the 
entire  fermentation.  Unhealthy  yeast  will  produce  an  abnormal  propor- 
tion of  acids,  and  acids  render  gluten  first  friable  and  then  soluble.  At  the 
friable  stage,  bread  may  be  high,  badly  shaped,  dark  and  ragged,  but  defi- 
cient in  pile.’' 

898.  Odour. — ^This  is  best  judged  by  pulling  a loaf  open  and  burying 
the  nose  deep  in  the  cleft.  The  bread  should  have  a nutty,  sweet  smell  ; 
this  denotes  the  highest  degree  of  excellence  so  far  as  this  quality  is  con- 
cerned. There  may  be  an  absence  of  smell,  or  what  is  perhaps  most  forcibly 
described  as  a mawkish  arid  damp  odour  ; these  belong  to  the  indifferent 
stage.  The  bread  may  smell  sour,  in  which  case  an  unfavourable  opinion 
is  naturally  formed.  Beyond  these  are  the  smells,  approaching  to  stenches, 
arising  from  butyric,  ropy,  and  even  putrid  fermentation. 


BREAD  ANALYSIS. 


833 


899.  Flavour. — ^This  of  course  is  one  of  the  most  crucial  tests  of  which 
bread  can  be  put.  It  is  probably  the  only  one  adopted  by  the  vast  majority 
of  the  bread-eating  public.  Fortunately,  the  judgment  based  on  flavour 
is  almost  invariably  a sound  one  ; a bread  which  pleases  the  palate  is  usually 
one  that  is  wholesome.  Having  made  this  statement,  it  may  be  well  also 
to  indicate  one  direction  in  which  the  palate  test  is  untrustworthy  ; many 
people  are  extremely  fond  of  hot  rolls  for  breakfast.  These  luxuries  are 
not,  however,  to  be  indulged  in  by  every  one,  for  hot  bread  is  not  easily 
digestible.  The  reason  is  a simple  one  ; the  soft  nature  of  bread,  while  still 
warm,  causes  it  to  be  formed  into  balls  in  the  mouth,  wLich  are  swallowed 
without  the  due  admixture  with  saliva. 

When  tasting  bread,  nothing  having  a strong  flavour  should  have  been 
eaten  for  some  little  time  previously  ; a small  piece  of  the  bread  should 
be  put  in  the  mouth,  masticated,  and  allowed  to  remain  there  a short  time 
before  being  swallowed.  The  flavour  should  be  sweet,  and  of  course  there 
must  be  an  absence  of  sourness  or  any  marked  objectionable  taste.  The 
physical  behaviour  of  the  bread  in  the  mouth  is  also  of  importance.  The 
bread  should  not  clog  or  assume  a doughy  consistency  in  the  mouth  ; neither, 
on  the  other  hand,  must  it  be  dry  or  chippy.  In  addition  to  tasting  the 
dry  bread,  a slice  spread  with  butter  may  be  eaten.  It  need  not  be  said 
that  in  this  test  the  butter  must  be  unexceptionable. 

900.  Colour  and  Thickness  of  the  Crust. — The  crust  should  be  of  a rich 
brownish  yellow  tint  ; neither  too  light  on  the  one  hand,  nor  too  dark  on 
the  other.  So  far  as  is  consistent  with  adequate  baking,  the  crust  should 
be  as  thin  as  possible. 

The  act  of  baking  changes  the  character  of  several  of  the  constituents 
of  the  flour.  Thus,  the  albumin  is  coagulated,  and  thereby  rendered  in- 
soluble. The  starch  is  partly,  at  least,  rendered  soluble  by  the  gelatinisa- 
tion  consequent  on  heating.  The  fatty  matters  of  the  flour  are  unchanged  ; 
at  times,  however,  bread  is  found  to  contain  fat  over  and  above  that  nor- 
mally present  in  flour.  In  fancy  bread,  butter  or  milk  is  sometimes  used 
in  the  dough  ; small  quantities  of  lard  are  also  employed  by  some  bakers  in 
order  to  give  a special  silkiness  to  the  fracture  where  tw^o  loaves  of  crumby 
bread  are  separated  from  each  other.  The  ash  is  not  materially  affected 
in  quantity,  except  in  so  far  as  it  is  increased  by  the  addition  of  salt.  The 
w'ater  varies  considerably.  Subjoined  are  the  results  of  some  analyses  col- 
lected by  Konig  and  quoted  by  Blyth.  A number  of  others  by  the  authors 
are  given  in  various  parts  of  this  work  : — 


1 Mini- 

mum. 

Maxi- 

mum. 

Mean  for 
Fine 
Bread. 

j Mean  for 
Coarse 
Bread. 

Water 

26-39 

47-90 

38-51 

41-02 

Nitrogenous  Substances  . . 

4-81 

1 8-69 

6-82 

6-23 

Fat 

0-10 

1-00 

0-77 

0-22 

Sugar  . . _ 

0.82 

4-47 

2.37 

2-13 

Carbohydrates  (Starch,  etc.) 

38-93 

62-98 

49-97 

48-69 

Woody  Fibre 

0-33 

0-90 

0-38 

0-62 

Ash 

0-84 

1-40 

1-18 

1-09 

901.  Quantity  of  Water  in  Bread. — ^The  question  may  fairly  be  asked — 
On  what  principle  is  a decision  to  be  made  as  to  whether  a bread  contains 
too  much  water  ? In  reply,  the  loaf  having  become  cool,  say  2 hours 
after  being  removed  from  the  oven,  should  on  being  cut  feel  just  pleasantly 

3 H 


834 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


moist,  not  dry  and  chippy,  nor  on  the  other  hand  in  the  slightest  degree 
sticky  or  clammy.  A second  loaf,  on  being  examined  in  the  same  way  when 
2 days  old,  should  answer  to  tlie  same  tests,  and  should  not  show  the 
shghtest  signs  of  sourness  or  mustiness.  Some  loaves  of  bread  containing 
even  40  per  cent,  of  water  would  very  well  pass  this  examination  ; while 
others  which  might  contain  much  less  water  would  nevertheless  be  damp 
and  sodden,  rapidly  turning  mouldy  or  sour.  Notwithstanding  that  the 
latter  contained  absolutely  the  less  water,  they  would  still  be  condemned 
as  containing  more  than  they  ought  ; while  the  former  would  be  returned 
as  coming  within  the  limit.  The  quantity  of  water  permissible  in  a bread 
must  depend  on  the  nature  of  the  flour  used  ; the  offence  is  not  in  using 
sufficient  water  to  a strong  flour,  but  in  adding  more  to  a weak  flour  than  it 
can  properly  take. 

Another  question  arises — Would  it  not  be  well  for  the  public  to  insist 
on  being  supplied  with  bread  made  from  such  flours  as  normally  require; 
for  their  conversion  into  bread,  a low  proportion  of  water  ? Again,  in 
reply,  the  strongest  flours — that  is,  those  which  naturally  absorb  the  most 
water — are  made  from  the  most  nutritious,  soundest,  best  matured,  and 
highest  class  wheats  ; so  that  the  baker  who  uses  a flour  with  high  water- 
absorbing capacity,  uses  also  a high  priced  flour. 

902.  Standard  for  Moisture. — ^By  legal  enactment  the  quantity  of  mois- 
ture present  in  bread  of  standard  quality  may  not  exceed  31  per  cent,  in 
the  district  of  Columbia,  U.S.A.  (Foods  and  their  Adulteration,  Wiley.) 

As  against  this,  Wiley  regards  35  per  cent,  of  moisture  as  being  the 
average  quantity  in  typical  American  high-grade  bread  (see  paragraph  623). 

As  an  example  of  excessive  water,  Cameron  states  that  bread  supplied 
in  August,  1896,  to  the  troops  at  Clonmel,  county  of  Tipperary,  Ireland, 
contained  per  100  parts  ; — 

Water  . . . . . . . . . . . . ..  58-28 

Organic  Matter  . . . . . . . . . . ..  40-57 

Ash 1-15 


100-00 

(Analyst,  1896,  p.  255). 

903.  Analytic  Estimations. — ^In  an  ordinary  analysis  of  bread,  where  the 
object  is  not  to  test  for  audulteration,  the  estimations  given  below  may  be 
made.  A thin  slice  should  be  cut  from  the  middle  of  the  loaf,  the  crust  cut 
off,  and  then  the  interior  portion  crumbled  between  the  fingers  ; the  crumbs 
must  be  thoroughly  mixed,  and  at  once  placed  in  a bottle. 

Moisture,  Ash,  and  Phosphoric  Acid. — Determine  as  directed  in  para- 
graph 887  on  Malt  Extracts. 

Proteins. — Determine  by  Kjeldahrs  method  on  1 gram  of  the  bread. 

Acidity. — Take  10  grams  of  the  bread,  grind  up  in  a mortar  with  a 
small  quantity  of  water,  transfer  to  a flask,  and  make  up  to  100  c.c.  Allow 
to  stand  for  an  hour  in  a boiling-water  bath,  cool,  and  titrate  with  A/IO 
soda,  using  phenolphthalein  as  an  indicator.  The  acidity  may  be  calculated 
as  lactic  acid. 

Fat. — Direct  extraction  of  bread  with  ether  or  light  petroleum  spirit, 
however  long  continued,  gives  too  low  results,  owing  to  the  fat  being  enclosed 
by  the  starch  and  dextrin.  The  results  are  lower  than  those  obtained  from 
the  flour  from  Avhich  the  bread  was  made.  The  following  method,  slightly 
modified  from  that  suggested  by  Weibull,  gives  trustworthy  results,  but  it  is 
necessary  to  work  exactly  as  follows  : — 4 grams  of  new  or  3 grams  of  stale 
bread  or  dried  bread  solids  are  put  into  a 70  c.c.  beaker,  and  covered  with 
15  c.c.  of  water,  after  which  is  added  10  drops  of  dilute  sulphuric  acid  (25 
per  cent.).  The  beaker  is  then  placed  in  an  ordinary  saucepan  containing 


BREAD  ANALYSIS. 


835 


a little  water,  the  lid  put  on,  and  the  contents  boiled  gently  for  at  least  45 
minutes,  or  till  the  solution  gives  no  starch  reaction  with  iodine.  While  still 
warm,  the  contents  are  carefully  neutralised  with  slight  excess  of  powdered 
marble  or  pure  precipitated  calcium  carbonate.  The  mixture  is  then  heated 
over  a water  bath,  or  by  standing  on  the  top  of  the  hot-water  oven,  until  con- 
centrated to  about  10  C.C.,  when  it  is  spread  on  a strip  of  stout  blotting-paper 
(such  as  is  used  in  Adam’s  milk  process,  being  22  inches  long  by  2J  inches 
wide),  and  any  liquid  remaining  in  the  beaker  is  removed  by  means  of  a 
piece  of  cotton-wool,  which  is  then  put  on  to  the  filter  paper.  The  latter 
resting  on  iron  gauze,  is  first  dried  for  10  minutes  at  100°  C.  The  paper  is 
now  rolled  into  the  usual  shape,  and  then  dried  for  3-4  hours  at  100-103°. 
After  this  it  is  placed  in  a Soxhlett’s  apparatus,  and  extracted  for  about  60 
times  with  ether  or  light  petroleum  spirit,  the  extraction  occupying  in  all 
about  5 hours.  The  ether  solution  is  then  evaporated,  and  dried  in  a 
Aveighed  dish  in  the  usual  manner. 

The  following  analytic  results  show  very  clearly  the  relation  between  the 
fat  as  determined  by  direct  extraction,  that  by  W iebull’s  method,  and  the  fat 
contained  in  the  meal  or  flour  ; — 

I.  Analysis  of  fancy  loaf  containing  lard,  the  fat  being  determined  by 
direct  extraction. 

II.  Analysis  of  same,  by  one  of  the  authors,  the  fat  being  determined 
by  the  method  above  described. 

III.  Analysis  of  same  by  another  analyst,  fat  determined  by  similar 
method. 

IV.  Analysis  of  plain  bread,  made  and  analysed  by  one  of  the  authors. 

V.  Analysis  of  fancy  loaf  containing  according  to  the  recipe  J lb.  of 
lard,  made  and  analysed  by  one  of  the  authors. 

VI.  Analysis  of  “ all  new  milk  ” bread,  made  and  analysed  by  one  of 
the  authors. 

In  the  first  table  all  the  percentages  of  the  various  constitutents  are 
calculated  for  purposes  of  comparison  to  the  same  proportion  of  water  as 
was  originally  found  in  No.  I.  analysis. 

In  the  second  table  is  shown  the  percentage  composition  of  the  bread  in 
the  dry  state. 


Table  I. 


Constituents. 

i 

II. 

III. 

IV. 

V. 

VI. 

Water 

40-49 

40-49 

40-49 

1 

40-49 

40-49 

40-49 

Proteins  (Albuminoids),  Gluten,  etc.  . . 

7-55 

7-32 

— 

7-43 

7-55 

8-74 

Fat  . . 

0-96 

1-85 

1-81 

0-95 

2-16 

1-84 

Starch,  etc. 

38-97 

— 

— 

— 

. — 

— ■ 

1 Soluble  INIatter,  principally  Carbo- 

1 hydrates 

10-30 

12-16 

12-19 

6-31 

15-18 

8-16 

1 Mineral  Matter  . . 

1-73 

— 

1-87 

Ml 

1-37 

1-28 

j Table  II. 

1 

I. 

II. 

III. 

IV. 

AU. 

! 

Proteins  (Albuminoids),  Gluten,  etc.  . . 

12-68 

12-31 

12-49 

12-70 

14-70 

' Fat 

1-60 

3-12 

3-05 

1-60 

3-63 

3-10 

! Soluble  Matters,  principally  Carbo- 

hydrates 

17-30 

20-44 

20-50 

10-62 

25-52 

13-72 

1 Mineral  Matter  . . 

2-90 

— 

3-15 

1-88 

2-32 

2-16 

836 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  mixed  meal  used  in  Nos.  IV.,  V.  and  VI.  contained  1-47  per  cent,  of 
fat,  equal  to  1-69  per  cent,  in  the  meal  in  the  dry  state.  Ordinary  white 
bread  contains  on  an  average  in  the  dried  solids  ; — Fat,  0-7  to  1*14  per  cent.  ; 
soluble  matter,  5*0  to  8*0  per  cent.  ; ash  or  mineral  matter,  about  1-5  per 
cent.,  of  which  about  I-O  per  cent,  is  common  salt.  In  the  recipe  for  the 
fancy  loaf,  the  addition  of  the  J lb.  of  lard,  if  the  same  is  perfectly  pure, 
raises  the  calculated  percentage  of  fat  on  the  dried  bread  solids  by  the 
amount  of  2-07  per  cent,  which  agrees  almost  exactly  with  the  results  of 
analysis.  These  figures  do  not  confirm  the  view  sometimes  expressed,  that 
a part  of  the  fat  of  flour  is  in  bread-making  volatilised  in  the  oven. 

Soluble  Extract. — Take  25  grams  of  the  bread  and  240  c.c.  of  water,  rub 
down  with  a little  of  the  water  into  a perfectly  uniform  paste  in  a mortar. 
Transfer  to  a flask,  add  the  remainder  of  the  water  and  1 c.c.  of  chloroform. 
Or,  as  an  alternative  method,  the  bread  may  be  moistened  with  a little  of 
the  water  and  then  rubbed  through  a fine  sieve.  The  small  thimble-shaped 
strainers,  sold  for  attaching  to  the  spout  of  a tea-pot  in  order  to  strain  the 
tea,  answer  well  for  this  purpose.  The  strainer  is  then  washed  with  some 
more  of  the  water  and  the  whole  transferred  to  a flask.  Shake  vigorously 
at  intervals  during  12  hours,  or  allow  to  stand  overnight.  At  the  end 
of  the  time  shake  again,  and  allow  to  stand  for  half  an  hour  for  the  solids  to 
settle.  Filter  the  supernatant  liquid  until  perfectly  bright,  and  evaporate 
25  c.c.  to  dryness  for  soluble  extract.  Bread  contains  on  the  average  about 
40  per  cent,  of  water,  and  therefore  there  are  10  c.c.  in  25  grams  ; this  quan- 
tity, together  with  the  240  c.c.  added,  make  250  c.c.  The  water  extract 
may  therefore  be  viewed  as  a 10  per  cent,  solution  of  soluble  matters.  There 
is  probably  no  generally  applicable  method  which  extracts  the  whole  of  the 
soluble  matter  of  the  bread,  as  a portion  is  almost  certain  to  remain  behind. 
If,  on  the  other  hand,  the  bread  be  subjected  to  prolonged  boiling,  some  of 
the  constituents  which  were  not  originally  soluble  are  thereby  dissolved. 

It  is  not  recommended  to  evaporate  the  bread  to  dryness,  and  make 
the  determinations  of  soluble  matters  in  the  powdered  dry  residue,  as  this 
does  not  at  all  readily  yield  up  its  soluble  matter  to  water. 

Maltose. — Usually  10  c.c.  of  the  soluble  extract  solution  may  be  taken 
and  precipitated  with  Fehling’s  solution  in  the  usual  manner.  Should  the 
amount  of  precipitate  be  very  small,  another  10  c.c.  should  be  at  once  added. 

Soluble  Starch  and  Dextrin. — These  may  be  determined  as  described  in 
paragraph  881,  Chapter  XXIX. 

Soluble  Proteins. — Take  25  c.c.  of  the  soluble  extract  solution,  evaporate 
to  dryness  in  a flask,  and  determine  organic  nitrogen  by  Kjeldahl’s  process. 
The  difference  between  total  and  soluble  proteins  may  be  returned  as  in- 
soluble proteins. 

Starch. — This  is  usually  taken  as  difference,  after  making  all  other  deter- 
minations ; but  it  may  also  be  determined  direct  by  either  of  the  various 
processes  given  in  Chapter  XXIX.  for  estimation  of  starch.  From  the 
total  starch,  that  estimated  in  soluble  extract  solution  as  soluble  starch 
must  be  deducted. 

Cellulose. — This  may  be  determined  by  the  method  described  in  para- 
graph 882. 

Digestibility . — The  comparative  digestibility  of  bread  may  be  estimated 
by  the  method  described  in  Chapter  XVIII.,  paragraph  603.  Modifications 
may  be  made  in  the  strength  of  the  digestive  agents,  and  the  temperatures 
employed.  A useful  alternative  method  consists  in  first  digesting  for  3 
hours  with  the  acid  solution  of  pepsin,  and  then  adding  twice  as  much  normal 
sodium  carbonate  solution  as  necessary  to  neutralise  the  acid  present.  A 
similar  quantity  of  pancreatin  is  then  added  and  the  digestion  continued  for 
another  3 hours. 


CHAPTER  XXXI. 


ADULTERATIONS  AND  ADDITIONS. 

904.  Standard  Works  on  the  Subject. — ^In  giving  directions  for  both 
flour  and  bread  analysis,  the  authors  have  hitherto  confined  themselves  to 
such  modes  of  testing  as  enable  one  to  determine  the  quality  and  charac- 
ter of  each,  apart  from  any  considerations  as  to  the  presence  or  absence 
of  any  foreign  bodies.  The  present  chapter  contains  an  outline  of  the 
processes  employed  in  the  analysis  of  flour,  bread,  and  certain  other  sub- 
stances, for  the  purpose  of  detecting  adulteration.  This  branch  of  chem- 
istry applied  to  the  arts  of  milling  and  baking  has  received  considerable 
attention,  and  several  standard  works  of  reference  have  been  vTitten  on 
the  subject  ; among  these  may  be  mentioned  those  of  Allen  and  Blyth, 
both  of  which  represent  the  most  recent  and  authoritative  opinions  of 
chemists  on  the  problem.  For  several  of  the  tests  to  be  hereafter  described 
the  authors  are  indebted  to  these  works,  to  which  the  student  is  referred  for 
further  and  more  detailed  information. 

905.  Information  derived  from  Normal  Analysis. — Some  of  the  tests 
aheady  mentioned  in  the  description  of  the  normal  analysis  of  flour  and 
bread  serve  also  as  indications  as  to  whether  a sample  is  adulterated.  Thus 
the  moisture,  if  unduly  high,  points  to  the  fact  that  at  some  stage  of  manu- 
facture, water  has  been  added  to  the  wheat,  stock,  or  flour  ; water  added 
for  other  purposes  than  normal  conditioning  or  improvement  of  the  grain 
nr  stock  must  be  regarded  as  objectionable. 

The  percentage  of  ash  in  the  flour  affords  some  guide  as  to  whether  the 
sample  has  been  treated  with  mineral  substances.  A flour  ash,  when  pro- 
perly burned,  should  amount  to  less  than  1 per  cent.  ; greater  quantities 
than  this  are  probably  due  to  mineral  adulteration.  Reference  has  already 
been  made  to  certain  considerations  arising  out  of  the  presence  of  undue 
ash  for  the  colour  of  the  flour.  See  paragraph  815. 

906.  Impurities  and  Adulterants  of  Flour. — ^The  following  are  some  of 
the  foreign  substances  that  are  at  times  found  in  the  ground  form  in 
flour  ; seeds  of  other  plants,  as  corn-cockle  and  darnel  ; blighted  and 
ergotised  grains — these  are  to  be  viewed  rather  as  impurities  than  adul- 
terants, the  latter  term  being  confined  to  those  bodies  wilfully  added  for 
purposes  of  fraud.  Among  these  latter  are  rye,  rice-meal,  maize  flour, 
potato  starch,  meal  from  leguminous  plants,  as  peas  and  beans,  and  alum 
and  other  mineral  bodies.  The  question  of  the  addition  of  mineral  sub- 
stances as  “improvers  ” has  been  already  discussed  in  Chapter  XX. 

The  tests  for  many  of  these  substances  are  in  part  microscopical  ; the 
chapters  containing  directions  for  practical  microscopic  work  provide 
information  and  data  as  to  the  making  of  such  tests.  The  following  are 
the  principal  chemical  tests  for  the  bodies  above  mentioned  : — 

907.  Darnel. — ^Treat  a little  of  the  flour  with  alcohol  (rectified  spirits 
of  wine,  not  methylated  spirits),  digest  at  30°  C.  for  an  hour,  shaking  occa- 
sionally. Filter  and  examine  the  filtrate.  This  should  be  clear  and  colour- 
less, or  at  most  should  be  only  of  a light  yellow  colour.  In  the  event  of  the 

837 


838 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


flour  containing  darnel,  the  alcoholic  extract  is  of  a greenish  hue,  and  has 
an  acrid  and  nauseous  taste. 

Treatment  with  alcohol  and  a small  quantity  of  acid  is  a useful  test 
for  other  adulterants.  Extract  the  flour  with  70  per  cent,  alcohol  [i.e., 
a mixture  of  alcohol  and  water,  containing  alcohol  equivalent  to  70  per 
cent,  of  absolute  spirit),  to  which  5 per  cent,  of  hydrochloric  acid  has  been 
added.  Pure  wheat  or  rye  flour  yields  a colourless  extract  ; barley  or  oats 
gives  a full  yellow  tint  ; pea-flour,  orange-yellow,  mildewed  wheat,  purple- 
red,  and  ergotised  wheat,  a blood-red  colouration. 

908.  Ergot  and  Mould. — ^To  test  flour  for  ergot,  exhaust  20  grams  with 
concentrated  alcohol  in  a fat  extraction  apparatus  ; notice  the  colour, 
which  in  the  presence  of  ergot  is  more  or  less  red.  Mix  this  solution  with 
twice  its  volume  of  water,  and  shake  up  separate  portions  of  this  mixture 
with  ether,  amyl-alcohol,  benzol,  and  chloroform.  Ergot  imparts  a red 
colour  to  the  whole  of  these  solvents. 

Vogel  recommends  the  flour  should  be  stained  with  aniline  violet,  and 
then  examined  under  the  microscope  ; should  any  of  the  starch  granules 
have  been  attacked  by  ergot  or  other  fungoid  growths,  they  acquire  an 
intense  violet  tint  ; while  if  they  are  perfectly  sound,  they  remain  compara- 
tively colourless. 

Ergotised  flours  evolve  the  peculiar  flsh-like  odour  of  trimethylamine 
when  heated  with  a solution  of  potash  : the  same  smell  is,  however,  evolved 
by  flour  otherwise  damaged.  The  test  is  of  service  in  distinguishing  between 
sound  and  unsound  flours. 

The  use  of  mouldy  wheat  for  the  manufacture  of  flour  can  be  detected 
by  placing  the  sample  in  a tightly  stoppered  bottle,  damping  it  and  placing 
it  in  a bath  heated  to  about  30°  C.  Any  mouldy  taint  can  readily  be  observed 
after  thus  standing  for  2 or  3 hours. 

909.  Rice  in  Flour,  Gastine. — Gastine  recommends  for  the  detection  of 
rice  in  wheaten  flour  its  treatment  with  a colour  stain.  A trace  of  the  flour 
is  treated  with  a solution  of  0-05  gram  of  aniline  blue  in  100  c.c.  of  33  per 
cent,  alcohol.  The  flour  is  then  dried  at  about  30°  C.,  and  Anally  by  heating 
for  a few  minutes  at  110-130°  C.  The  preparation,  is  then  mounted  in 
cedar-wood  oil  and  examined  under  the  microscope.  Treated  in  this  man- 
ner the  wheat  starch  granules  are  almost  invisible  and  very  rarely  do  they 
even  exhibit  a visible  hilum.  On  the  contrary  the  hilums  of  the  minute 
rice  starch  granules  show  up  very  distinctly,  and  usually  in  regular  clusters, 
since  each  fragment  of  rice  is  generally  built  up  of  a number  of  starch  gran- 
ules. When  wheat  granules  are  cracked,  the  Assures  show  very  distinctly 
as  a result  of  the  infiltration  of  nitrogenous  matter,  which  readily  takes  the 
stain.  Granules  of  maize  and  buckwheat  starches  behave  like  rice.  {Comptes 
rend.,  1906,  142,  1207). 

910.  Maize  Meal  in  Wheaten  Flour,  Kraemer. — ^Kraemer  states  that 
flours  containing  corn-meal  give  off  an  odour  of  roasting  corn  when  heated 
in  glycerin  to  boiling  for  a few  minutes.  {Jour.  Amer.  Chem.  Soc.,  1899,  662.) 

911.  Maize  Starch  in  Wheaten  Flour,  Baumann. — ^For  the  detection  of 
maize  starch  (corn  flour)  in  wheaten  flour,  Baumann  recommends  the  follow- 
ing test  : — About  OT  gram  of  the  flour  under  examination  is  mixed  with 
10  c.c.  of  a 1-8  per  cent,  solution  of  potash,  and  the  test  tube  shaken  at 
intervals  during  2 minutes.  Four  or  five  drops  of  25  per  cent,  diluted  hydro- 
chloric  acid  are  then  added  and  the  tube  again  shaken.  The  liquid  must 
still  be  slightly  alkaline  in  order  to  prevent  the  precipitation  of  the  dissolved 
proteins.  A drop  is  taken  out  and  examined  under  the  microscope,  when 
the  wheat-starch  granules  will  be  found  to  be  completely  ruptured  while 


ADULTERATIONS  AND  ADDITIONS. 


839 


tliose  of  maize  are  unaltered.  As  little  as  from  1 to  2 per  cent,  of  maize 
can  thus  be  detected.  The  test  may  be  employed  quantitatively  by  taking 
mixtures  containing  known  quantities  of  maize  starch,  treating  them  in  the 
same  way  as  the  sample  under  examination,  and  deciding  which  matches 
it  when  drops  of  similar  size  are  microscopically  examined.  The  same 
method  is  applicable  to  the  detection  of  maize  in  rye  flour.  [Zeits.  /.  Unter- 
such.  Nahr.-u  Genussmittel,  1899,  2 [1]  27.) 

912.  Maize  in  Wheaten  Flour,  Embrey.— Embrey  has  not  found  the 
foregomg  process  to  give  satisfactory  results  in  his  hands,  and  has  therefore 
devised  and  recommends  the  following  modification  : — Mixtures  of  pure 
wheat  and  maize  flours  are  prepared  containing  respectively  10,  15,  20,  25 
and  30  per  cent,  of  the  maize.  Weighed  quantities  (0-2  gram)  of  each  of 
these,  and  of  the  sample  under  examination,  are  placed  in  test  tubes  (15 
c.m.  X 2 c.m.)  which  are  fitted  with  paraffined  corks.  To  each  is  added 
a quantity  of  20  c.c.  of  potassium  hydroxide  solution  (18  grams  per  litre), 
and  the  tubes  shaken  uniformly  for  3 minutes.  Twelve  drops  of  diluted  hydro- 
chloric acid  (HCl  of  specific  gravity  1T6,  50  c.c.  ; water,  100  c.c.)  are  next 
introduced  and  the  tubes  shaken,  and  then  whirled  in  a centrifugal  machine 
at  600  revolutions  per  minute.  One  c.c.  of  the  clear  liquid  is  transferred 
to  a Nessler  tube  and  diluted  to  50  c.c.,  after  which  1 c.c.  of  an  iodine  solu- 
tion (I,  0-25  gram  ; KI,  1 gram  ; water  to  250  c.c.)  is  added.  The  tint 
obtained  compared  with  those  of  the  standard  tubes  gives  the  proportion 
of  maize  within  about  5 per  cent.  For  a more  exact  determination,  10  c.c. 
of  the  clear  liquid  from  each  tube  are  boiled  for  2 hours  with  1 c.c.  of 
dilute  sulphuric  acid  (1  : 7),  then  neutralised,  diluted  to  50  c.c.  and  run  from 
a burette  into  a boiling  mixture  of  Gerrard's  solution,  10  c.c.,  and  Fehling's 
solution,  2 C.C.,  until  the  colour  is  discharged.  The  percentage  of  maize  is 
obtained  from  the  standard  tube  of  which  the  same  amount  is  required  to 
discharge  the  colour. 

Gerrard’s  Solution  is  prepared  by  diluting  10  c.c.  of  freshly  prepared 
Fehling’s  solution  with  40  c.c.  of  water,  and  adding  a solution  (about  5 per 
cent.)  of  potassium  cyanide  from  a burette,  until  the  blue  colour  is  only  just 
perceptible.  During  the  addition  of  the  cyanide,  the  diluted  Eehling’s 
solution  is  kept  boiling  and  constantly  stirred  in  a porcelain  dish.  {Analyst, 
1900,  25,  315.) 

This  process  is  really  an  estimation  of  the  soluble  starch  resulting  the 
rupture  of  the  granules  of  wheaten  starch  by  the  action  of  potassium  hydroxide 
solution.  In  the  first  method  it  is  directly  estimated  as  starch  by  a colori- 
metric process  with  iodine  ; and  in  the  second  by  conversion  into  glucose 
and  then  volume trically  by  a modification  of  Eehling’s  solution.  An  objec- 
tion to  the  method  is  that  variations  in  the  proportion  of  wheaten  starch 
in  a flour  may  be  due  to  causes  other  than  the  presence  of  maize.  Thus  a 
very  weak  flour  may  contain  more  starch  than  a very  strong  one,  and  if  the 
former  be  also  exceptionally  dry  and  the  other  comparatively  moist  the 
difference  is  still  further  enhanced.  Also,  if  even  as  much  as  30  per  cent,  of 
maize  flour  is  contained  in  the  flour  the  actual  reduction  in  wheat  starch  is 
only  approximately  from  about  70  to  50  per  cent.  On  the  other  hand 
the  amount  of  maize  flour  will  have  been  increased  from  zero  to  30  per  cent.  ; 
obviously,  therefore,  a direct  estimation  of  the  maize  starch  is  preferable 
if  practicable.  As  a modification  of  Embrey's  method  it  is  suggested  that 
the  solution  of  clear  starch  should  be  decanted  off,  the  insoluble  residue 
thoroughly  shaken  up  with  water,  and  again  whirled  in  the  centrifugal 
machine,  so  as  to  free  it  as  far  as  possible  from  soluble  starch.  The  residual 
maize  starch  may  then  be  dissolved  by  heating  with  water,  and  estimated 
either  colorimetrically  with  iodine,  or  by  conversion  into  glucose  and  esti- 


840 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


mation  by  Fehling’s  solution.  The  most  important  point  here  is  whether 
or  not  the  sediment  is  practically  free  from  soluble  wheaten  starch. 

In  the  discussion  on  the  above  paper,  Bevan  mentioned  with  approval 
a qualitative  method  devised  by  W ilson,  and  consisting  of  mixing  the  flour 
with  clove  oil,  and  examining  with  a J or  |^-inch  objective,  when  the  hilum 
of  maize  appears  as  a black  dot  or  star,  while  wheaten  and  other  starches  are 
practically  invisible. 

913.  Starch  in  Yeast. — ^Bruylants  and  Druyts  recommend  the  following 
method  of  estimating  flour  or  starch  in  yeast  : From  50  to  100  grams  of 
the  yeast  are  to  be  taken  according  to  the  suspected  quantity  of  starch,  and 
mixed  thoroughly  with  a dilute  solution  of  iodine  in  potassium  iodide. 
The  mixture  is,  if  necessary,  passed  through  a fine  sieve  in  order  to  remove 
any  large  sized  fragments  of  impurity.  It  is  then  allowed  to  settle,  when  the 
starch  falls  first,  until  the  starch  is  covered  by  a thin  layer  of  yeast.  The 
yeasty  liquid  is  poured  away  and  this  washing  by  decantation  continued 
until  only  starch  remains.  A little  fresh  iodine  must  be  added  from  time 
to  time.  The  sediment  is  dissolved  and  converted  into  glucose  by  heating 
with  dilute  (2  per  cent,  hydrochloric  acid),  and  then  estimated  in  the  usual 
manner.  In  tests  made  on  yeasts  containing  known  quantities  of  starch, 
ranging  from  3 to  15  per  cent.,  the  amounts  recovered  by  the  method  ranged 
between  96-7  per  cent,  and  100*8  per  cent,  of  the  added  starch.  [Bull.  Assoc. 
Beige  des  China.,  13  [1]  20.) 

Instead  of  dissolving  the  starch  obtained  by  this  process  in  hydrochloric 
acid,  it  may  be  estimated  direct  by  first  washing  with  strong  alcohol  and 
then  evaporating  and  drying  in  a tared  dish.  Comparative  experiments 
should  be  made  on  yeasts  to  which  known  quantities  of  starch  have  been 
added. 

914.  Aniline  Blue  in  Flour,  Violette. — ^Violette  states  that  blue  colouring 

matter  is  sometimes  employed  in  order  to  counteract  the  yellow  tinge  of 
flour.  In  order  to  detect  such  addition  a sheet  of  white  filter  paper  is 
floated  on  the  surface  of  water,  and  a little  of  the  suspected  flour  sprinkled 
thereon.  In  the  presence  of  aniline  colours,  dark  specks  soon  appear  on 
the  paper,  which  grow  in  size  and  form  blue  spots.  [Bull.  Soc.  China.,  1896, 
15,  456).  . 

915.  Mineral  Adulterants  and  Additions. — ^The  presence  or  absence  of 
most  foreign  mineral  matters  will  have  been  indicated  by  the  percentage  of 
ash  yielded.  Alum  is,  however,  added  to  flour  in  quantities  too  small  to 
be  thus  detected.  One  of  the  most  ready  means  of  separating  mineral 
substances  from  flour  is  by  means  of  what  is  termed  the 

916.  Chloroform  Test. — ^This  test  depends  on  the  fact  that  chloroform 
has  a density  higher  than  that  of  the  normal  constituents  of  flour,  but  lower 
than  that  of  minerals  generally  ; consequently,  on  agitating  a mixture  of 
flour  and  chloroform,  and  then  allowing  it  to  rest,  the  flour  rises  to  the 
surface,  and  any  mineral  adulterants  sink  to  the  bottom.  On  the  small  scale, 
for  the  purpose  of  a qualitative  test,  a large  dry  test-tube  may  be  about 
one-third  filled  with  the  flour,  then  chloroform  added  to  within  one  inch 
from  the  top.  The  tube  must  then  be  corked  and  violently  shaken,  after 
which  it  must  be  allowed  to  rest  for  some  hours  ; the  mineral  matter  will 
then  be  found  to  have  sunk  to  the  bottom.  For  quantitative  purposes  a 
glass  “ separator  is  requisite.  This  is  a cylindrical  vessel  some  2 inches 
in  diameter,  8 or  10  inches  in  length,  stoppered  at  the  top,  and  furnished 
with  a stopcock  at  the  bottom.  Introduce  in  this  vessel  100  grams  of  the 
flour  and  about  250  c.c.  of  methylated  chloroform  ; treat  as  directed  for 
the  smaller  quantity.  When  the  separation  is  effected,  open  the  stopcock 
and  allow  any  sediment,  with  as  little  as  possible  of  the  liquid,  to  run  through. 


ADULTERATIONS  AND  ADDITIONS. 


841 


Treat  this  again  with  a little  more  chloroform  in  a smaller  separator,  and 
once  more  drain  the  sediment  off  through  the  stop-cock  into  a watchglass, 
•or  small  evaporating  basin.  Allow  the  chloroform  to  evaporate  ; treat  the 
dry  residue  with  a small  quantity  of  water,  and  filter.  Any  plaster  of  Paris 
■calcium  phosphate,  or  other  insoluble  mineral  matter  will  remain  on  the 
filter,  and  may  be  ignited  and  weighed.  Evaporate  the  solution  to  dry- 
ness, and  examine  the  residue  carefully  with  a low  power  under  the 
microscope  for  any  crystals  of  alum. 

In  making  this  test,  flours,  which  are  absolutely  free  from  any  added 
mineral  matter,  occasionally  give  a slight  sediment.  This  was  formerly 
ascribed  to  the  presence  of  detritus  from  the  millstones  ; but  this  can 
scarcely  be  an  adequate  explanation,  as  the  authors  have  obtained  such 
sediment  from  pure  roller-milled  flours. 

917.  Special  Test  for  Alum. — The  most  convenient  test  for  alum  in 
flour  consists  in  adding  thereto  an  alkaline  solution  of  logwood.  Take  5 
grams  of  recently  cut  logwood  chips  and  digest  them  in  a closed  bottle  with 
100  c.c.  of  methylated  spirit.  Also  make  a saturated  solution  of  ammonium 
carbonate.  Mix  10  grams  of  the  flour  with  10  c.c.  of  water,  then  add  1 c.c. 
of  the  tincture  of  logwood  and  1 c.c.  of  the  ammonium  carbonate  solution, 
and  thoroughly  mix  the  whole.  With  pure  flour  the  resultant  mixture  is 
of  a slight  pinkish  tint.  Alum  changes  the  colour  to  lavender  or  full  blue. 
The  blue  colour  should  remain  on  the  sample  being  heated  in  the  hot-water 
oven  for  an  hour  or  two. 

918.  Mineral  Matters  in  Solution. — Certain  mineral  matters  are  at  times 
added  to  flour  in  the  state  of  solution,  the  solution  being  sprayed  into  the 
flour  or  added  to  a portion  of  the  stock  which  is  then  dried,  ground,  and  mixed 
in  with  the  flour.  If  this  operation  is  performed  with  sufficient  care  no 
particles  of  the  flour  are  sufficiently  weighted  by  the  adherent  mineral 
matter  to  sink  in  chloroform,  and  so  the  appHcation  of  that  test  fails  to 
reveal  the  presence  of  such  added  mineral  matter.  Very  frequently,  how- 
ever, some  portion  of  the  flour  has  absorbed  sufficient  of  the  mineral  addition 
to  sink  in  chloroform.  If  so,  this  portion  should  be  thus  separated  and  the 
ash  in  the  two  portions  determined.  Any  difference  detected  is  an  indica- 
tion of  the  addition  of  some  foreign  mineral.  The  nature  of  the  substance 
added  may  be  ascertained  by  further  analysis  of  the  ash. 

In  cases  where  it  is  desired  to  test  particularly  for  sprayed  additions  of 
mineral  salts,  it  is  well  to  compare  the  total  ash  of  the  flour  with  that  of  a 
sample  of  known  purity  of  the  same  colour  and  grade,  bearing  in  mind 
Snyder’s  conclusions  on  the  relation  between  ash  and  grade  of  flour  already 
given  (paragraph  815).  In  this  connection  it  must  be  borne  in  mind  that 
a bleached  flour  will  contain  less  ash  than  a corresponding  unbleached  flour. 
In  the  next  place  apply  the  chloroform  test  as  described.  Should  this  fail, 
add  to  the  chloroform  and  flour  in  the  separator,  absolute  alcohol  in  small 
quantities  at  a time,  and  shake  and  allow  to  settle  between  each  addition. 
As  the  mixed  liquid  approaches  in  density  to  that  of  flour,  a point  is  reached 
at  which  any  mineral-w'eighted  particles  of  flour  may  sink  and  the  purer 
portion  float  on  the  top.  In  this  case  separate  the  two  and  determine  the 
ash  in  each  separately.  If  deemed  necessary,  make  analyses  of  each  portion 
of  ash.  Should  the  whole  of  the  flour  have  absorbed  the  mineral  addition 
with  absolute  uniformity,  a separation  cannot  of  course  be  effected  by  this 
method.  But  in  all  such  methods  of  introducing  foreign  mineral  matters, 
some  portion  of  the  flour  is  almost  certain  to  have  absorbed  more  mineral 
matter  than  others.  If  the  addition  is  exceedingly  small,  this  mode  of  separa- 
tion is  not  likely  to  be  effective,  and  recourse  must  be  had  to  a more  or  less 
complete  analysis  of  the  whole  ash.  The  finding  of  any  substance  in  a 


842 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


quantity  beyond  the  extreme  amount  that  may  occur  as  a natural  consti- 
tuent of  flour  is  evidence  of  its  presence  as  an  added  body.  In  the  event 
of  the  addition  of  mineral  substances  to  a flour  which  is  naturally  deflcient 
in  those  substances,  and  in  such  quantity  as  not  to  exceed  the  normal 
amount  which  may  be  present,  then  even  a complete  analysis  of  the  ash 
may  fail  to  reveal  the  fact  of  mineral  bodies  having  been  added.  More 
usually,  however,  any  such  additions  will  not  have  the  same  proportionate 
composition  as  normal  flour  ash,  and  in  this  way  their  presence  will  be 
indicated. 

919.  Alum  in  Bread. — -Bread  is  tested  for  alum  by  first  taking  5 c.c.  of 
the  tincture  of  logwood,  5 c.c.  of  the  ammonium  carbonate  solution,  and 
diluting  them  down  to  100  c.c.  This  mixture  must  at  once  be  poured  over 
about  10  grams  of  the  crumbled  bread  in  an  evaporating  basin.  It  is  allowed 
to  stand  for  5 minutes,  and  then  the  superfluous  liquid  drained  off.  Slightly 
wash  the  bread  and  dry  in  the  hot-water  oven.  Alum  gives  the  bread 
treated  in  this  manner  a lavender  or  dark  blue  colour,  which  is  intensified 
on  drying.  Pure  bread  first  assumes  a light  red  tint,  which  fades  into  a 
buff  or  light  brown.  After  some  practice  this  test  gives  satisfactory  results, 
and  is  so  sensitive  that  as  little  as  7 grains  of  alum  to  the  4 lb.  loaf 
have  been  detected.  The  depth  of  colour  affords  a means  of  roughly  esti- 
mating the  quantity  of  alum  present.  It  is  essential  that  the  tincture  of 
logwood  be  freshly  prepared,  and  that  the  test  be  made  immediately  after 
mixing  the  tincture  of  logwood  and  ammonium  carbonate  solution. 

920.  Young  on  Longwood  Test  for  Alum. — ^In  1886  Young  pointed  out 
(The  Analyst)  that  under  certain  circumstances  bread  which  is  absolutely 
free  from  alum  gives  the  characteristic  reaction  wuth  logw^ood.  On  investi- 
gation it  was  found  that  the  flour  used  gave  no  indication  by  logwood,  but 
that  the  bread  gave  a very  distinct  colouration.  The  sample  was  heavy  and 
sour — subsequent  experiments  showed  that  the  colouration  was  directly 
due  to  the  acidity.  On  taking  pure  breads,  which  were  absolutely  negative 
to  the  logwood  test,  and  moistening  with  dilute  acetic  acid  (1  to  250  of 
water),  and  letting  stand  for  one  hour,  all  gave  a most  intense  blue  colour 
with  logAVOod.  So  also  did  pure  flour  similarly  treated.  Young  considers 
this  effect  to  be  due  to  phosphate  of  alumina  (a  body  normally  produced 
from  the  mineral  constituents  of  flour),  being  slightly  soluble  in  dilute 
acetic  acid,  and  quotes  experiments  in  proof  of  this  solubility.  He  further 
found  that  such  phosphate  of  alumina  exists  in  a state  of  combination  with 
the  gluten,  and,  as  a result  of  careful  washing,  was  able  to  procure  starch,. 
Avhich,  after  treatment  wdth  acetic  acid  and  subsequent  application  of  the 
logwood  test,  gave  no  colouration. 

In  a quantitative  experiment  some  best  quality  Hungarian  flour  was 
taken,  yielding  0-7  per  cent,  of  ash  and  8 per  cent,  of  dry  gluten  The 
gluten  was  washed  out  in  a muslin  bag  and  dried,  20  grams  Avere  taken, 
finely  poAA'dered,  and  treated  AAoth  250  c.c.  of  50  per  cent,  acetic  acid,  and 
heated  in  the  Avater  bath  for  28  hours.  The  gluten  had  then  dissolved, 
leaving  a sediment,  from  AAPich  the  clear  liquid  AA^as  poured,  and  the  residue 
again  tAAUce  treated  in  the  same  manner  AAuth  the  diluted  acetic  acid.  The 
three  lots  of  acid  extract  AA'ere  evaporated  to  dryness,  and  the  residue  burned 
to  a perfect  ash — this  Avas  treated  in  dilute  hydrochloric  acid,  and  the  insolu- 
ble residue  fused  AA'itli  alkaline  carbonates,  dissolved  in  dilute  hydrochloric 
acid,  filtered,  and  filtrate  added  to  acid  solution  of  ash.  This  Avas  again 
evaporated  to  dryness,  redissolved  in  small  quantity  of  hydrochloric  acid, 
filtered,  filtrate  boiled,  and  cautiously  added  to  25  c.c.  of  saturated  solution 
of  pure  sodium  hydroxide,  also  boiling,  and  kept  boiling  for  a feAV  minutes. 
The  precipitate  AA'as  dissolved  AA'ith  hydrochloric  acid,  and  precipitated  Avitli 
saturated  solution  of  sodium  phosphate  and  slight  excess  of  ammonia. 


ADULTERATIONS  AND  ADDITIONS. 


843 


After  10  minutes’  boiling,  the  precipitate  of  aluminium  phosphate  was 
collected,  filtered,  and  weighed.  The  20  grams  of  gluten  yielded  0-0185 
gram  of  aluminium  phosphate,  equal  to  0-01875  from  250  grams  of  fiour, 
or  0-0075  per  cent.  Alumina  was  thus  shown  to  be  a natural  constituent 
of  flour,  and  associated  with  the  gluten.  The  alumina  thus  normally  present 
justifies  a deduction  being  made  of  from  7 to  8 grains  of  alum  per  4 lb.  loaf 
from  the  amount  corresponding  to  total  alumina  by  analysis. 

For  further  experiments  by  Young  on  the  solubility  of  aluminium  phos- 
phate in  acetic  acid,  the  reader  is  referred  to  The  Analyst  for  April,  1890. 
He  there  shows  that  the  presence  of  ammonium  acetate,  and  also  that  of 
ammonium  chloride,  prevent  the  complete  precipitation  of  aluminium  phos- 
phate in  the  presence  of  acetic  acid. 


921.  Calcium  Sulphate  in  Bread. — -Calcium  sulphate  is  occasionally 
found  as  an  added  substance  in  bread.  The  addition  is  probably  due  to 
the  aeration  of  the  bread  by  a phosphatic  baking  powder,  in  which  the  acid 
phosphate  contains  calcium  sulphate  as  a natural  impurity.  As  only  traces 
of  sulphates  exist  ready  formed  in  the  cereals,  they  may  be  detected  by  an 
examination  of  the  unignited  bread.  The  best  plan  is  to  soak  12-20  grams 
of  the  bread  for  some  days  in  1200  c.c.  of  cold  distilled  water  until  mould 
forms  on  the  surface  of  the  liquid.  The  solution  is  then  strained  through 
muslin  and  the  filtrate  treated  with  20  c.c.  of  phenol  distilled  over  a small 
quantity  of  lime.  The  whole  is  then  raised  to  the  boiling  point  and  filtered 
through  paper  ; 1000  c.c.  of  the  filtrate  are  slightly  acidulated  with  hydro- 
chloric acid  and  precipitated  in  the  cold  by  barium  chloride.  Every  237 
parts  of  barium  sulphate  represent  136  parts  of  calcium  sulphate.  {^Allen's 
Commercial  Organic  Analysis,  vol.  1.,  p.  460.) 


922.  Mineral  Oil  for  Parting  Loaves. — ^In  the  case  of  close-packed  bread 
it  is  the  custom  to  smear  the  contiguous  surfaces  of  loaves  with  melted  lard 
or  oil  for  the  purpose  of  preventing  their  sticking  together.  For  this  pur- 
pose a petroleum  residue  is  employed  (1896)  in  Germany,  known  as  Brotel. 
Illness  has  been  traced  to  this  practice  in  Hamburg,  the  residue  remaining 
in  the  loaf  and  causing  digestive  disturbances.  {Jour.  8oc.Chem.lnd.,  368, 
1896.) 


923.  Colouring  Matter  in  Cakes. — ^In  order  to  determine  whether  cakes 
and  other  confectionery  have  been  coloured  with  yolk  of  egg,  or  with  other 
colouring  matters,  Spaeth  recommends  that  the  fat  be  extracted  and  ex- 
amined. The  following  are  the  characteristics  of  egg -yolk  fat  and  wheat 
meal  fat  respectively  : — 


Sp.  g.  at  100°  C.  (water  at  15°=1*00) 
Melting  point  of  fatty  acids 
Saponification  number  . . 

Iodine  value 

,,  ,,  of  fatty  acids 

Reichert-Meissl  value  . . 

Refractive  index  at  25°  C. 

,,  ,,  on  Zeiss  refractometer  scale 


Egg  Fat.  Wheat  Fat. 

0- 881  0-9068 

36°  34° 

184-43  166-5 

68-48  101-5 

72-6  — 

0-66  2-8 

1- 4713  1-4851 

68-5  9-20 


When  the  iodine  value  exceeds  98,  and  the  phosphoric  acid  (P2O5)  in 
the  fat  is  below  0-005  per  cent.,  there  cannot  be  more  than  traces  of  egg -yolk. 
{Analyst,  233,  1896.) 

In  this  proposed  method,  no  cognisance  is  taken  of  the  fact  that  cakes 
and  similar  articles  have  large  quantities  of  butter  and  other  fats  added  to 
them,  the  constants  of  which  may  vary  widely  from  those  of  either  egg-yolk 
or  wheat  fats. 


CHAPTER  XXXII. 

ROUTINE  MILL  TESTS. 


924.  Practical  Adaptation  of  Flour  Tests  to  Mill  Routine.— The  fore- 
going chapters  have  contained  descriptions  of  the  modes  of  making  various 
flour  tests  and  the  conclusions  to  be  drawn  therefrom.  There  now  remains 
for  discussion  the  problem  of  their  adaptation  to  commercial  milling  routine. 
This  may  be  done  in  two  ways,  either  by  the  employment  of  a chemist  at 
the  mill,  or  by  sending  samples  by  arrangement  to  a chemist  who  under- 
takes work  of  this  class.  In  either  case  some  special  training  is  requisite. 
A professional  knowledge  of  the  science  of  chemistry  and  the  principles  of 
analysis  is  of  course  essential  ; but  in  addition  to  these  a chemist  who  under- 
takes the  work  of  commercial  flour  analysis  should  be  familiar  with  the 
general  properties  of  wheats  and  of  flour.  He  should  also  have  had  suffi- 
cient experience  of  the  physical  methods  of  testing  employed  by  both  miller 
and  baker,  and  of  the  carrying  out  of  baking  tests  under  conditions  of  scien- 
tific accuracy.  In  cases  where  it  is  decided  to  carry  on  such  work  at  the 
mill,  a laboratory  must  be  provided  ; of  this  some  description  has  been 
already  given  in  Chapter  XXV.  on  Analytic  Apparatus. 

925.  Dispatch  of  Samples  and  Results. — ^If  the  alternative  is  adopted 
of  entrusting  these  duties  to  an  outside  chemist,  then  arrangements  must 
be  made  for  the  collection  of  the  necessary  samples  and  their  dispatch.  It 
should  be  made  the  special  business  of  some  responsible  person  to  take  the 
samples  at  some  specified  time.  This  person  must  be  familiar  with  the 
process  of  sampling,  and  must  take  care  that  the  samples  are  properly 
representative  of  the  bulk.  The  quantities  must  depend  on  the  nature  of 
the  tests  to  be  made.  Among  some  of  the  most  frequent  of  such  tests  are 
those  of  moisture.  For  each  of  these  an  ounce  of  the  material  is  sufficient. 
Having  regard  to  the  ease  with  which  wheat  products  either  absorb  or  lose 
moisture,  the  samples  for  this  purpose  must  at  once  be  packed  in  air- 
tight receptacles.  Probably  the  most  convenient  form  is  a glass  tube  of 
the  requisite  size,  fitted  with  an  india-rubber  cork.  Special  wooden  blocks 
are  made  for  holding  these  for  postal  purposes  ; any  desired  number  can 
then  be  packed  in  the  one  block  and  dispatched  by  post.  For  an  ordinary 
analysis,  an  8 oz.  sample  is  a suitable  quantity,  and  a convenient  pack- 
age consists  of  a small  bag  made  of  fine  close-textured  canvas  or  similar 
material.  This  in  turn  should  be  enclosed  in  a tin  canister  with  tightly 
fitting  lid.  Wooden  boxes  should  be  provided  to  hold  a certain  number  of 
these  canisters,  for  dispatch  to  the  chemist’s  laboratory.  The  locks  of 
tliese  boxes  should  be  provided  with  two  keys  to  be  held  respectively  by  the 
forwarder  and  recipient.  A systematic  course  of  labelling  must  be  adopted. 
Tlie  labels  should  be  affixed  to  the  bags  or  glass  tubes,  and  not  to  the  covers 
of  canisters  or  the  corks  of  tubes.  The  reason  is  that  the  identifying  label 
must  not  be  capable  of  detachment  from  the  sample  by  the  act  of  opening  the  package. 
Further,  the  label  should  bear  the  name  and  address  of  the  sender.  A 
])roper  dispatch  book  must  be  kept  in  which  descriptions  of  samples,  identify- 
ing marks  or  numbers,  and  dates  of  dispatch  are  entered.  For  baking  tests, 


ROUTINE  MILL  TESTS. 


845. 


! a larger  sample  must  be  sent,  and  for  this  2 lbs.  is  a very  convenient  quan- 
Ij  tity.  Larger  bags  of  the  same  kind  of  material  as  before  are  on  the  whole 
Ij  most  suitable.  It  is  not  absolutely  necessary  that  they  be  enclosed  in  tin 
; canisters,  but  they  should  also  be  packed  in  wooden  boxes.  The  sample 
sent  for  baking  will  also  serve  for  the  other  analytical  texts,  except  that  for 
moisture.  The  small  samples  for  this  purpose  should  always  be  packed 
in  the  air-tight  tubes  ; and  the  larger  carrying  boxes  may  be  easily  fitted 
; with  a small  division  to  hold  the  tubes.  The  packed  sample  cases  should 
so  far  as  possible  be  regularly  forwarded  by  a certain  mail  or  train.  There 
are  very  few  districts  in  which  samples  cannot  be  dispatched  in  the  evening 
i so  as  to  be  in  the  hands  of  the  chemist  early  the  next  morning.  He  will  of 
course  be  perfectly  familiar  with  the  routine  of  treatment  on  their  reception,, 
the  only  suggestion  to  be  made  being  that  such  results  as  are  wanted  most 
quickly  should  be  arranged  for  first.  For  example,  moistures  are  fre- 
quently required  with  the  utmost  expedition,  and  the  determinations  should 
therefore  be  started  immediately. 

In  returning  results,  they  may  frequently  require  to  be  sent  by  tele- 
graph ; in  that  case  a code  should  be  arranged  by  which  the  data  could  be 
sent  cheaply  and  with  the  least  possible  risk  of  mistake.  A certain  number 
of  figures  can  always  be  sent  as  a word  ; but  figures  are  prone  to  mistakes 
in  transmission,  and  above  all  such  mistakes  are  not  evident  on  the  face  of 
them.  Code  words  are  not  so  liable  to  the  same  errors,  and  should  there- 
fore be  used  in  preference.  As  an  example,  the  following  is  a convenient  and 
simple  code  for  the  transmission  of  moisture  results. 


9*0  Aback 

10*0  Babel 

11*0  Cabin 

12*0  Lark 

9*1  Abbey 

lO-l  Bank 

IM  Cask 

12-1  Late 

9*2  Accent 

10*2  Beach 

11*2  Chart 

12*2  Lean 

9*3  Adder 

10*3  Beef 

11*3  Civil 

12-3  Lell 

9*4  Affix 

104  Bird 

114  Clamp 

124  Lip 

9*5  Agate 

10*5  Blank 

11-5  Clock 

12*5  Li  van 

9*6  Aisle 

10*6  Blow 

11*6  Code 

12*6  Lock 

9*7  Alarm 

10*7  Boast 

11*7  Court 

12-7  Lose 

9*8  Ambit 

10*8  Box 

11-8  Crest 

12-8  Lrag 

9*9  Anchor 

10*9  Buoy 

11*9  Cube 

12*9  Luel 

13*0  Ear 

14*0  Fault 

15-0  Gas 

16-0  Hack 

I3-I  Ebb 

14*1  Fear 

15*1  Gear 

16*1  Hair 

13*2  Echo 

14-2  Feud 

15-2  Gem 

16-2  Head 

13*3  Eddy 

14*3  Field 

15-3  Gill 

16-3  Help 

134  Eel 

144  Fight 

154  Give 

164  Hide 

13*5  Effect 

14*5  Flock 

15*5  Gland 

16-5  Hint 

13-6  Egg 

14*6  Foam 

15-6  Good 

16-6  Hoax 

13*7  Ember 

14-7  Fowl 

15*7  Gout 

16-7  Hole 

13*8  End 

14*8  Freak 

15*8  Grain 

16*8  Hulk 

13*9  Equip 

14*9  Fury 

15*9  Gust 

16-9  Hurt 

All  telegraphic  results  must  be  confirmed  by  post, 
to  be  in  the  hands  of  the  miller  at  a regular  time. 

and  dispatched  so  as 

926.  Standard  Quality. — ^It  must  be  borne  in  mind  that  high  quality  is 
not  a fixed  and  invariable  standard,  but  depends  largely  on  what  are  local 
requirements.  This  question  most  generally  arises  when  systematic  tests 
are  for  the  first  time  introduced,  and  requires  its  proper  answer  in  each 
individual  mill  before  such  tests  can  yield  results  of  much  value.  That 
which  is  the  best  flour  in  the  one  district  is  not  the  best  in  another,  and 
therefore  the  chemist  first  requires  to  know  the  exact  kind  of  flour  the  miller 


846 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


M'ishes  to  make.  The  miller  can  usually  lay  his  hands  on  one  particular 
parcel,  which  has  the  approval  of  his  most  skilful  and  critical  customers, 
which  he  would  like  always  to  supply,  and  which  he  would  be  content  to 
take  as  a standard.  If  he  can  also  obtain  certain  samples  which  more  or 
less  fall  short  of  this  standard,  and  with  clearly  marked  defects,  they  will 
also  be  of  service.  The  chemist  should  be  supplied  with  these  samples, 
and  his  first  object  should  be  to  find  out  where  the  faulty  examples  differ 
from  the  standard  one.  No  precise  directions  can  be  given  for  doing  this, 
since  it  is  here  that  the  skill  and  judgment  of  the  expert  are  brought  to  bear 
on  the  problems  of  each  particular  flour.  Care  should  be  exercised  in 
discriminating  between  differences  which  are  accidental  and  those  which 
are  fundamental.  From  these  data  the  requirements  in  the  standard  flour 
for  each  particular  mill  are  formulated,  and  the  effect  of  any  departures 
from  the  standard  of  quality  are  duly  noted.  This  is  a judgment  which 
cannot  be  formed  immediately  ; the  first  opinion  must  only  be  looked 
on  as  provisional,  and  must  be  confirmed  or  otherwise  by  subsequent  tests. 
Still  it  is  remarkable  how  soon,  as  a result  of  regular  testing,  the  chemist 
forms  an  opinion  on  the  quality  of  the  flour  and  recognises  any  deviation. 
These  opinions  are  usually  confirmed  by  subsequent  baking  tests. 

927.  Uniformity  in  Quality. — ^Having  formulated  standards  for  each 
miller’s  requirements,  the  next  object  is  to  see  that  flours  of  these  qualities 
are  being  uniformly  produced.  For  this  purpose  flours  are  regularly  tested. 
The  first  and  simplest  object  of  such  tests  is  to  serve  as  a control  on  the 
working  of  the  mill,  and  to  secure  the  most  help  from  such  tests  the  miller 
(Le.,  the  working  miller)  should  work  in  unison  with  the  chemist.  So  far 
from  being  antagonistic,  their  real  duties  are  complementary,  and  any  real 
improvement  is  largely  dependent  on  their  mutual  co-operation.  The 
miller  will  take  samples  from  those  parts  of  the  mill  which  will  afford  the 
most  information,  and  the  chemist  will  duly  test  same.  In  particular  if 
suspicion  attaches  to  the  work  of  any  particular  machine  or  part  of  the  mill, 
samples  of  the  products  of  this  section  will  receive  special  attention.  In 
this  way  tests  are  made,  and  the  results  carefully  recorded.  In  cases  where 
any  marked  departure  from  the  usual  standard  occurs,  attention  should 
be  drawn  to  it,  and  the  flour  watched  in  its  future  stages  so  as  to  note  whether 
it  has  been  found  in  any  way  unsatisfactory  in  actual  use. 

928.  Actual  Routine  Tests  Employed. — ^Of  set  purpose  the  selection  of 
these  is  left  to  the  judgment  of  the  individual  chemist.  In  previous  pages  the 
nature  and  objects  of  the  most  important  tests  have  been  described  in  detail. 
The  following  are  among  those  which  will  probably  be  regularly  employed. 

Moisture. — This  test  has  a very  important  bearing  on  the  whole  question 
of  the  conditioning  of  wheat.  Samples  may  be  tested  of  the  whole  wheat 
unmoistened  and  after  the  moisture  has  been  added  by  any  means.  The 
comparison  of  these  shows  how  much  water  has  actually  been  added.  Then 
tests  may  be  made  on  the  whole  wheat,  the  flour,  and  the  bran.  These 
will  show  how  far  and  to  what  extent  the  moisture  has  penetrated.  Lack 
of  penetration  may  be  due  to  a particularly  hard  bran,  or  it  may  be  the 
result  of  conditioning  not  having  been  carried  out  sufficiently  long  before 
grinding.  Where  any  system  of  improving  treatment  is  carried  out  as  a 
part  of  the  conditioning  process,  or  by  the  spraying  of  either  stock  or  flour, 
the  moisture  tests  serve  the  secondary  purpose  of  determining  the  quantities 
of  the  improving  agents  which  have  actually  been  added.  Moisture  tests, 
intelligently  applied,  have  therefore  most  important  uses  in  the  mill. 

Ash. — As  a control  on  the  degree  of  length  of  patent,  regular  ash  deter-  . 
minations  are  exceedingly  valuable  when  properly  made. 

Protein  Estimations. — The  details  of  them  have  been  given  most  fully. 


ROUTINE  MILL  TESTS. 


847 


Tlie  selection  must  depend  on  individual  judgment.  Total  proteins,  gluten, 

' and  alcohol-soluble  proteins  will  probably  be  included  in  most  schemes  of 
i protein  determmations. 

Water -Absorption. — Viscometer  tests  not  only  measure  an  important 
property  of  flours,  but  also  one  which  serves  as  a most  important  check  on 
uniformity  of  production. 

Colour. — In  every  well  conducted  mill,  the  colour  of  flour  is  always  being 
carefully  watched.  This  is  especially  necessary  where  any  bleaching  process 
is  being  employed. 

929.  Replacement  Tests. — Tests  for  uniformity  are  not  confined  to  being 
a check  on  the  satisfactory  working  of  the  mill,  but  they  have  a further 
most  important  bearing  on  the  difficult  question  of  replacing  in  a mixture 
one  wheat  by  another.  Some  useful  general  information  on  this  point  is 
given  on  page  282,  but  that  scarcely  more  than  touches  the  fringe  of  the 
problem.  To  start  with,  the  same  kind  of  wheat  varies  with  its  age,  and 
as  the  crop  from  a fresh  harvest  arrives  it  must  be  carefully  tested  before  it 
can  be  regarded  as  the  equivalent  of  that  of  the  preceding  year.  When  a 
miller  is  grinding  a mixture  of  several  varieties  of  wheat,  and  one  of  these 
runs  out,  it  is  imperative  that  any  proposed  substitute  shall  not  seriously  alter 
the  character  of  the  flour  produced.  In  making  the  change  he  is  limited  by 
the  facts  that  the  average  price  of  the  wheat  composing  his  mixture  must 
not  exceed  a certain  amount,  and  that  the  various  grades  of  flour  he  manu- 
factures must  all  maintain  their  specific  qualities  ; and  so  far  as  possible 
must  be  produced  in  their  usual  proportions. 

In  making  any  tests  on  the  whole  wheats,  they  may  be  reduced  to  fine 
meal,  and  the  results  of  gluten  or  other  determinations  calculated  out  on  the 
assumption  of  a 70  per  cent,  yield  of  straight-run  flour.  Evidently  this 
can  be  nothing  more  than  an  assumption,  because  the  flour  yield  of  wheats 
varies  within  wide  limits. 

Again,  for  reasons  on  which  the  previous  subject  matter  will  have  thrown 
some  light,  the  mixmg  of  various  wheats  does  not  always  produce  the 
expected  results.  A mixture  of  strong  and  weak  wheats  having  a known 
percentage  of  gluten,  for  example,  sometimes  yields  a loaf  which  is  quite 
appreciably  better  or  worse  than  was  expected,  and  there  is  always  some 
anxiety  as  to  the  result  of  a new  blend  until  test  bakings  have  been  made 
on  the  resultant  flour. 

930.  Milling  Tests. — ^The  only  true  test  under  these  circumstances  is  the 
milling  test,  in  which  the  various  wheats  are  ground  separately  and  their 
resultant  flours  tested  chemically  and  by  baking.  They  should  then  be 
mixed  in  the  desired  proportions  and  again  tested  until  such  a blend 
is  obtained  as  satisfies  the  miller’s  desideratum — a maximum  of  quality  at  a 
minimum  of  cost.  With  very  small  milling  plants  it  is  the  custom  to  make 
a trial  by  putting  a few  sacks  of  a newly  arrived  wheat  through  the  entire 
mill.  But  while  this  is  a tedious  and  expensive  experiment  with  a small 
plant,  it  is  practically  an  impossibility  with  a large  one.  The  obvious 
alternative  is  to  lay  down  a small  milling  plant  for  experimental  purposes. 
This  must  not  be  too  large,  and  yet  must  be  large  enough  to  make  a fairly 
good  commercial  sample  of  flour. 

A very  convenient  plant  for  making  these  tests  has  recently  been  intro- 
duced, which  consists  of  a machine  that  in  a condensed  form  is  able  to  per- 
form all  the  operations  of  a gradual  reduction  roller  plant  built  in  one  frame, 
driven  by  one  main  belt  and  taking  up  a very  little  space.  This  machine  is 
illustrated  in  Fig.  122,  and  embodies  within  itself  two  pairs  of  “ Break  ” 
or  fluted  rollers,  a sieve  between  the  first  and  second  pair,  a centrifugal 
■dressing  machine  to  dress  the  flour  from  the  first  break  meal  and  another 


848 


THE  TECHNOLOGY  OF  BREAD-MAKING. 

to  deal  with  the  second  break  stock  and  tail  over  the  bran  to  the  sack.  There 
is  then  left  the  semolina  from  the  tails  of  the  first  centrifugal  and  the  bran 
middlings  from  the  “ Cut-off  ” of  the  second  break  centrifugal,  to  be  ground 
on  two  pairs  of  smooth  reduction  rollers  in  sequence,  each  of  which  is  suc- 
ceeded by  a flour  dressing  reel.  The  whole  process  is  entirely  automatic 
from  the  incoming  wheat  to  the  marketable  products  of  flour,  bran  and 
sharps. 


Fig.  122. — Midget  Testing  Mill. 


This  useful  little  appliance,  which  goes  by  the  name  of  the  “ Midget,’^ 
and  is  made  by  Messrs.  Alfred  R.  Tatter  sail  and  Co.,  75,  Mark  Lane,  London, 
E.C.,  lends  itself  admirably  to  the  testing  of  small  parcels  of  wheat,  as  its 
capacity  is  to  make  from  140  to  280  lbs.  of  finished  flour  per  hour.  By  its 
means  a grist  can  be  made  from  two  or  even  one  sack  of  wheat,  and  a very 
passable  yield  can  be  obtained.  While  the  results  got  on  this  machine 
may  not  be  identical  in  every  respect  with  those  got  on  the  larger  and  more 
elaborate  systems,  they  yield  trustworthy  comparative  results. 


Fig.  123. — Wheat  Cleaning  Machine, 


ROUTINE  MILL  TESTS. 


849 


A very  useful  adjunct  to  testing  mills  is  a cleaning  machine  made  by 
Messrs.  Howes  & Co.,  of  Mark  Lane,  and  shown  in  Fig.  123.  This  little 
machine  goes  in  very  small  compass,  and  has  a double  sieve  to  take  out  large 
and  small  impurities  by  a powerful  aspiration.  The  floor  space  it  occupies 
is  only  about  15  in.  x 40  in. 

Working  with  a plant  of  this  description,  any  wheat  may  be  taken 
weighed,  and  milled  either  with  or  without  conditioning.  Its  comparative 
behaviour  during  milling  can  be  observed,  and  the  total  yield  of  flour  deter- 
mined. Finally  the  quality  of  the  flour  can  be  tested  against,  and  com- 
pared with  that  of,  flour  milled  from  the  standard  mixture  on  the  same 
machine. 

931.  Replacement  Calculations. — ^In  making  wheat  replacements,  the 
following  is  a very  common  occurrence.  Given  a wheat  strong  in  one  con- 
stituent (C),  and  another  wheat  weak  in  the  same  constituent  (C),  it  is 
required  to  calculate  the  proportions  of  each  that  must  be  taken  to  give  a 
mixture  that  shall  have  a desired  intermediate  percentage  of  C.  Thus  as 
an  example,  a wheat  has  been  in  use  which  has  4 per  cent,  of  C.  The  only 
wheats  that  can  be  used  to  replace  it  are  a stronger  wheat  in  that  particular 
respect,  containing  5 per  cent,  of  C,  and  a weaker  one  containing  only 
2 per  cent,  of  C.  In  what  proportions  must  they  be  used  to  give  a mixture 
containing  4 per  cent,  of  C ? 

Stronger  wheat,  S,  contains  5 per  cent  of  C. 

Weaker  ,,  W ,,  2 „ „ C. 

Alixture,  M,  is  required  to  contain  4 per  cent,  of  C. 

First  calculate  the  quantity  of  each  that  will  contain  4 parts  of  C. 

As  5 (of  S)  is  to  4 : : 100  : 80 
As  2 (of  W)  : 4 : : 100  : 200 

Therefore,  80  parts  of  S will  contain  4 of  C. 

. 200  „ W „ „ 4 of  C. 

and  100  ,,  M must  ,,  4 of  C. 

Call  the  quantities  that  will  contain  the  amount  of  C in  M as  just  indi- 
cated, QS,  QW,  and  QM. 

Then  QS  (QW  — QM)  = amount  of  S to  be  taken. 

andQW(QM-QS)  = „ W „ 

Thus  QS  (QW-QM)  = 

80  (200  — 100)  = 8000  parts  of  S to  be  taken, 

and  QW  (QM-QS)  = 

200  (100  — 80)  = 4000  parts  of  W to  be  taken. 


Then  8000 

parts  of  S contain 

400  of  C. 

and  4000 

„ w „ 

80  of  C. 

12,000 

„ M 

4*^  of  C. 

and  100 

„ M 

4 of  C. 

Of  the  stronger  wheat,  therefore,  8 parts  must  be  taken,  and  of  the 
weaker,  4 parts  ; or  yet  more  simply  in  the  proportion  of  2 to  1 . 

The  following  is  a somewhat  more  difflcult  example  : — 

S contains  4-3  per  cent,  of  C. 

W „ 1-9  „ „ C. 

M to  contain  2-7  ,,  ,,  C. 

As  4-3  : 2-7  : : 100  : 62-8  = QS. 

„ 1-9  : 2-7  : : 100  : 142  1 = QW. 

Then  QS(QW-QM)  = 62-8(142-l-100)  = 2643-88  of  S. 

„ QW  (QM-QS)  = 142-1(100  -62-8)  = 5286-12  of  W. 


850 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


As  S contains  4-3  per  cent,  of  C,  2643-88  of  S contain  113-68  of  C. 

„ W „ 1-9  „ „ C,  5286-12  of  W „ 100-40  of  C. 

7930-00  of  M „ mT08  of  C. 

As  7930  : 100  : : 214-08  : 2-7  = desired  percentage  of  C. 

An  inspection  of  the  composition  of  the  mixture  shows  that  it  contains 
as  nearly  as  possible  1 part  of  the  stronger  wheat  to  2 parts  of  the  weaker 
one.  In  percentages,  the  result  works  out  thus  : — 

As  7930  : 100  : : 5286-12  : 66-66  per  cent,  of  W. 

100-66-66  =33-34  „ „ S. 

932.  Use  of  Improvers. — ^When  any  system  of  artificially  inproving 
flours  is  in  operation,  the  duty  of  checking  and  controlling  the  same  will 
naturally  fall  to  the  chemist  whether  working  in  or  out  of  the  mill.  In  the 
case  of  the  use  of  a bleaching  plant,  the  miller  Avill  exercise  his  own  judg- 
ment as  to  the  extent  of  the  bleach  he  requires.  The  chemist  should  com- 
pare the  reactions  of  the  bleached  with  the  unbleached  flour  and  see  that 
no  essential  of  the  flour  undergoes  any  material  alteration. 

In  event  of  the  employment  of  any  process  of  saline  or  other  treatment, 
whether  by  direct  addition,  spraying,  or  otherwise,  more  exacting  chemical 
duties  are  required.  The  proportions  of  saline  constituents,  sugars,  and 
amylolytic  and  proteolytic  enzymes  in  what  has  been  called  the  mill’s 
standard  flour  should  be  carefully  estimated.  It  should  also  be  ascertained 
whether  any  flours  which  are  below  standard  show  any  great  deviation  in 
any  of  the  foregoing  particulars.  Experiments  should  be  made  in  order  to 
determine  whether  the  addition  of  these  deficient  bodies  improves  the 
quality  of  the  flour,  and  if  so  to  what  extent  they  should  be  added.  The 
object  of  all  these  tests  is  to  formulate  some  definite  scheme  for  the  addition 
of  these  agents  to  the  flour  of  each  individual  mill.  Some  such  data  having 
been  acquired,  the  experimental  flours  of  new  wheats  should  be  tested  vdth 
and  without  the  improving  addition,  and  the  system  of  adding  or  not  adding 
any  improver  carried  out  on  a scientific  basis.  It  must  be  borne  in  mind 
that  the  object  of  all  these  additions  is  simply  to  remedy  the  natural  defi- 
ciencies of  some  wheats  and  thus  place  them  on  the  level  normally  attained 
by  other  wheats  without  any  addition  whatever.  Important  responsi- 
bilities are  thus  cast  on  the  chemist,  as  non-addition  is  in  some  cases  as- 
necessary  as  addition  is  important  in  others. 

933.  Baking  Tests. — Not  only  the  control  of  the  testing  mill,  but  also 
that  of  the  mill’s  baking  tests  will  probably  be  within  the  functions  of  the 
chemist.  It  will  be  more  especially  his  duty  to  see  that  conditions  of 
exactitude,  both  as  to  quantities  and  modes  of  working,  are  secured.  He 
A\'ill  also  see  that  the  baking  methods  used  represent  as  nearly  as  possible 
those  under  which  the  flour  is  baked  commercially,  and  will  inspect  the  baked 
loaves  and  keep  a record  of  their  properties.  Under  certain  circumstances 
it  may  be  necessary  for  him  to  make  a more  or  less  complete  analysis  of  the 
l)aked  bread. 

934.  Summary  of  Chemical  Functions  in  Mill. — ^The  preceding  para- 
graphs contain  an  outline  of  suggestions  as  to  the  adaptation  and  organisa- 
tion of  chemical  functions  to  milling  routine.  They  apply  equally  to  the 
performance  of  such  work  in  the  mill  or  in  the  laboratory  of  some  outside 
specialist.  The  suggestions  have  not  been  made  too  definite,  because  after 
all  each  particular  mill’s  set  of  problems  must  be  worked  out  by  the  chemist 
to  whom  they  are  entrusted.  As  to  the  utility  of  such  tests,  it  must  be  re- 
membered tliat  the  chemical  aspect  of  Avheat  quality  may  now  be  regarded 
as  fairly  settled  on  a scientific  basis,  and  questions  involving  chemical  investi- 


EOUTINE  MILL  TESTS.  851 

gation  must  continually  arise  in  practical  milling  if  the  best  results  are  to  be 
obtained  with  the  greatest  commercial  success. 

There  is  a certain  amount  of  healthy  rivalry  between  what  may  for 
convenience  be  called  “ chemical  ” and  baking  tests  on  flour.  Each  has 
its  own  merits,  but  a frequent  criticism  is  that  “ baking  is  after  all  the  final 
test  of  flour.”  To  this  no  open-minded  chemist  will  demur,  but  he  will  like- 
wise know  that  his  own  work  also  throws  most  important  light  and  guidance 
on  milling.  And  this  light  and  guidance  are  usually  of  a kind  which  baldng 
tests  are  absolutely  unable  to  furnish.  It  is  frequently  astonishing  to  note 
how  in  regular  routine  testing  of  flours  the  chemist  on  observing  some  depar- 
ture from  the  normal  is  able  to  predicate  successfully  an  alteration  in  the 
quality  of  the  flour.  And  the  importance  of  the  knowledge  thus  fur- 
nished lies  in  the  fact  that  it  is  not  merely  the  observation  of  a result,  but 
is  based  on  the  discovery  of  the  cause. 

As  to  the  value  of  chemical  work  as  applied  to  milling,  the  following 
testimony  from  the  Ogilvie  Flour  Mills  Co.,  Ltd.,  who  were  among  the 
pioneers  in  this  direction,  cannot  fail  to  be  of  interest  : — 

“ I would  say  that  in  the  operation  of  mills  of  large  capacity  such  as 
we  control,  our  experience  has  been  that  laboratory  work  is  one  of  the 
absolute  essentials  to  successful  and  economical  operation,  and  an 
actual  necessity  for  the  maintenance  of  a uniform  product  of  high 
quality.  We  certainly  would  not  for  one  moment  think  of  dispensing 
with  this  feature  of  our  business.”  [Personal  Communication,  April, 
1908.) 

One  last  suggestion  may  be  respectfully  made  to  those  who  may  decide 
to  enlist  chemical  assistance  in  their  milling  operations,  and  that  is  to  have 
patience  and  not  expect  too  much  at  the  commencement.  The  first  task 
of  any  chemist  will  be  to  thoroughly  familiarise  himself  with  all  the  pro- 
perties of  the  particular  mill’s  flour,  formulate  standards  on  the  lines  indi- 
cated, accumulate  data,  and  generally  study  the  whole  chemical  aspect  of 
the  problem  before  him  before  he  makes  or  suggests  any  radical  alterations. 
This  takes  time,  but  the  work  having  once  been  done,  his  recommendations 
have  the  merit  of  being  not  simply  speculative,  but  based  on  a reasonable 
degree  of  certainty. 

Further,  the  introduction  of  the  new  wheel  in  the  machinery  is  not  keenly 
welcomed  by  those  already  responsible  for  its  general  running.  In  certain 
cases  the  present  mill  foremen,  testing  bakers  and  others  have  keenly 
resented  what  they  regard  as  the  intrusion  of  the  chemist.  It  is  to  be 
feared  that  under  such  circumstances,  even  if  no  active  steps  are  taken  to 
nullify  the  recommendations  of  the  chemist,  no  great  amount  of  assistance 
is  rendered  in  the  direction  of  carrying  them  into  effect.  Much  will  here 
depend  on  the  tact  of  the  chemist  himself,  and  he  can  do  much  by  taking 
the  stand  that  his  functions  are  not  to  replace  or  displace  those  who  occupied 
the  responsible  positions  before  him,  but  rather  to  co-operate  with  and 
assist  them.  It  is  a truism  to  say  that  the  miller  can  make  a good  sack  of 
flour,  whereas  the  chemist  qua  chemist  cannot  ; but  if  the  miller  and  the 
chemist,  by  working  heartily  in  unison,  can  make  a better  and  cheaper 
sack  of  flour  than  can  the  former  alone,  then  the  milling  chemist  has  justi- 
fied his  existence.  This  phase  of  antagonism  and  suspicion  has  to  be  lived 
down,  and  the  chemist  requires  at  this  stage  all  the  moral  support  that  can 
be  afforded  him  by  his  employer. 


CHAPTER  XXXIII. 


CONFECTIONERS’  RAW  MATERIALS. 

935.  Flour  Confectionery. — ^Under  the  general  term  confectionery  are 
included  articles  of  such  a widely  diversified  nature,  that  some  sub-division 
is  necessary.  It  is  a convenient  classification  to  include  in  one  group  those 
goods  of  which  the  cake  may  be  taken  as  a type,  and  into  which  flour  enters 
as  an  essential  constituent,  and  call  them  flour  confections.  The  second 
group  may  then  include  those  goods  of  which  sugar  is  the  basis,  and  which 
may  be  viewed  as  sugar  confections.  The  present  work  attempts  to  deal 
principally  with  the  raw  materials  of  the  first  or  flour  group.  Incidentally, 
some  explanation  will  be  afforded  of  the  chemical  changes  underlying  certain 
confectionery  manufacturing  processes. 

A good  deal  of  the  matter  of  this  chapter  formed  the  subject  of  a course 
of  Cantor  Lectures  delivered  by  one  of  the  authors  before  the  Society  of 
Arts.  The  authors’  thanks  and  acknowiedgments  are  due  to  the  Society 
for  placing  at  their  disposal  the  report  of  the  lectures,  which  appeared  in  its 
Journal. 

936.  Flour. — ^The  composition  and  properties  of  flour  have  already 
been  dealt  w ith  so  exhaustively,  that  but  little  further  reference  is  necessary 
at  this  stage.  In  bread- making,  the  baker  will  naturally  prefer  a flour 
with  a high  absorbing  power,  since  all  else  being  equal,  the  cost  of  making 
dough  Avith  a larger  percentage  of  w^ater  is  obviously  less.  But  with  the  con- 
fectioner, the  moistening  ingredients  are  in  most  cases  more  expensive  than 
his  flour,  and  consequently  it  is  to  his  interest  to  use  a flour  which  shall 
obtain  its  desired  degree  of  moistness  wdth  the  minimum  of  these  more 
expensive  materials.  Further,  the  w'eaker  and  softer  flours  lend  them- 
selves more  readily  to  the  manipulation  and  working  necessary,  than  do 
those  of  stronger  nature.  It  should  also  be  noted  that  in  bread-making,  the 
flour  during  the  operation  of  fermentation  undergoes  considerable  softening, 
wiiile  no  similar  changes  occur  in  the  manufacture  of  confectionery.  For 
these  various  reasons,  therefore,  the  confectioner  usually  selects  a weak  and 
somewhat  soft  flour  containing  much  starch  and  comparatively  little  gluten, 
Avhicli  latter  should  be  of  a soft,  ductile,  and  silky  character.  For  the  sake 
of  the  colour  of  the  cakes  or  other  manufactured  goods,  a flour  of  a wFite 
or  delicate  creamy  tint  is  preferred.  xAmong  flours  used  by  the  confec- 
tioner, and  answ^ering  more  or  less  to  this  description,  are  finest  flours  from 
Englisli  wheats,  Hungarian  flours,  and  those  from  the  softer  wFite  wheats  of 
North  America. 

Moistening  Ingredients. 

937.  Milk. — ^As  a cake  moistening  ingredient,  milk  holds  a very  prom- 
inent place,  and  requires  a somewhat  extended  reference.  There  is  prob- 
ably no  substance  of  which  so  many  analyses  have  been  made,  as  milk, 
and  consequently,  its  composition  and  variations  of  composition,  are  well 
known.  Milk  is  used  by  the  confectioner  in  at  least  three  distinct  forms — 
new  milk,  skim  or  separated  milk,  and  sour  separated  milk.  This  latter  is 

852 


CONFECTIONERS’  RAW  MATERIALS. 


853 


at  times  supplied  mixed  with  butter-milk,  and  has  special  uses,  to  which 
reference  wull  again  be  made.  The  following  table,  based  on  the  authority 
of  Vieth  and  Richmond,  gives  the  average  composition  of  pure  new  milk  : — 


Fat  . . 

Proteins 

Sugar 

Ash  . . 

. . 3 6 

. . 4-5 

..  0-7 

4 0 

Total  Non-fatty  Solids  . . 

— 

8-8 

Water 

87*2 

100  0 

By  the  removal  of  fat  the  percentage  of  other  solid  bodies  in  milk  is 


slightly  increased,  and  separated  milk  has  about  the  following  average 

composition  ; — 

Fats  . . 

..  0-3 

Proteins 

. . 3-7 

Sugar 

46 

Ash 

..  0-7 

Total  Non-fatty  Solids 

. . 90 

Water 

. . 90-7 

100  0 


The  fat  of  milk,  like  that  of  other  fats,  confers  richness  on  cakes,  and 
will  be  dealt  with  in  detail  subsequently.  The  sugar  present  in  milk  is  a 
special  variety,  to  which  has  been  given  the  name  of  lactose.  Lactose,  or 
sugar  of  milk,  is  represented  by  the  formula,  C12H22O11,  and  has  therefore 
the  same  composition  as  cane  sugar  and  maltose.  It  is  not,  however,  iden- 
tical with  either  of  these  bodies.  Lactose  differs  from  cane  sugar  in  that 
it  is  far  less  sweet,  and  hence  is  not  such  a powerful  flavouring  agent  as 
sugar  of  the  latter  description.  The  remaining  constituent  of  milk  of  im- 
portance to  the  confectioner  is  the  protein  matter.  This  last  has,  like  the 
white  of  egg,  no  very  pronounced  taste,  but  yet  its  presence  confers  on  milk 
a fulness  and  roundness  of  flavour  (if  phraseology  may  be  borrowed  from 
other  tasters’  vocabularies)  which  a simple  solution  of  lactose  in  water 
would  not  possess.  In  the  baked  goods,  the  protein  of  milk  produces  a 
moistness  and  mellowness  of  character,  which  decidedly  differs  from  that 
caused  by  water  only.  Summing  up,  new  milk  gives  richness  through  its 
fat,  sweetness  through  its  sugar,  and  what  for  lack  of  a better  term,  may 
be  called  “mellowness  ” through  its  proteins.  Separated  milk  is  practically 
new  milk  less  its  fat. 

938.  Milk  Standards. — ^The  composition  of  mflk  has  been  indicated  in 
the  analyses  already  quoted,  but  these  figures  are  not  by  any  means  the 
lowest  obtainable  from  undoubtedly  pure  samples  of  milk.  For  purposes 
of  the  Food  and  Drugs  Adulteration  Acts,  the  limits  have  been  adopted  of 
3 per  cent,  of  fat,  and  8*5  per  cent,  of  non-fatty  solids.  But  for  confec- 
tioners’ purposes,  a direct  estimate  of  value  is  of  more  importance  than 
knowing  whether  or  not  a particular  sample  of  milk  passes  the  limits  of  the 
pubhc  analyst.  Thus  milks  containing  respectively  3 and  4 per  cent,  of  fat, 
would,  so  far  as  the  fat  is  concerned,  be  passed  as  free  from  adulteration  ; 
but  evidently  the  former  sample  has  only  three-fourths  the  fat  value  of 
the  latter.  For  some  years  this  subject  of  the  valuation  of  milks  has  en- 


854  THE  TECHNOLOGY  OF  BREAD-MAKING. 


gaged  the  attention  of  one  of  the  authors,  who  suggests,  and  has  for  some 
considerable  time  employed  a standard  of  valuation  worked  out  on  the 
following  lines  : — From  an  examination  of  a large  number  of  commercial 
milks  an  average  conventional  standard  of  quality  was  first  determined, 
the  aim  being  not  to  go  so  low  as  the  Government  limit  for  adulteration, 
but  to  take  figures  which  a buyer  might  reasonably  demand  to  be  reached 
in  milks  supplied  to  him.  These  were  ultimately  taken  as  being  for 


New  Milk. 

Separated  Milk. 

Total  Solids. . 

. . 12-5 

9-3 

Fat  . . 

3*5 

0-3 

Non -fatty  Solids  . . 

. . 90 

9 O’ 

The  figure,  9-0,  is  in  reality  somewhat  too  high  for  the  non-fatty  solids 
of  an  average  new  milk,  but  in  order  to  make  the  comparison  between  new 
and  separated  milk  as  simple  as  possible,  the  same  figure  has  been  adopted 
for  each.  The  difference  between  9-0  and  the  more  correct  figure,  8-8, 
does  not  practically  affect  the  valuations. 

At  the  time  when  these  figures  were  adopted,  the  approximate  whole- 
sale prices  of  milk  were,  new,  \0d.  per  gallon  ; separated,  2\d.  per  gallon. 
New  milk  differs  essentially  from  separated  in  that  it  contains  an  excess  of 
3-2  per  cent,  of  fat.  According  to  the  wholesale  prices  this  excess  of  fat 
lias  a market  value  of  7-5c?.,  and  in  the  same  proportion  3-5  per  cent,  of  fat  is 
worth  ^-'2d.  From  this  the  value  of  conventional  standard  samples  can  be 
expressed  in  terms  of  their  constituents  ; — 

New  Milk.  Separated  Milk. 

Fat  3-5  = S’2d.  ..  0-3  = 0-7t^. 

Non-fats  ..  ..  ..  9-0  = l-8c?.  ..  9-0  = l-8c?. 


per  gallon  . . . . 10 -Ot/.  2-5d. 

Obviously  other  prices  can  be  assigned  to  new  and  separated  milks 
and  the  values  of  the  constituents  similarly  calculated. 

If  the  value  of  standard  new  milk  be  called  100,  then  the  value  of  any 
other  sample  can  from  the  analysis  be  expressed  in  terms  of  percentages 
of  the  standard  from  the  following  Table  : — 


Valuation  of  Milks. 


Fat  in  Terms  of  Standard, 


Fat 

Percentage  of 

f Fat 

Percentage  of 

Fat 

Percentage  of 

per  cent. 

Standard. 

per  cent. 

Standard. 

per  cent. 

Standard. 

0-1 

— 

2-34 

1*7 

— 

39*83 

3*3 

zi: 

77*32 

0-2 

— 

4-69 

1*8 

42*17 

3*4 

79*66 

0-3 

— 

7-03 

1*9 

44*52 

3*5 

— 

82*00 

04 

— 

9-37 

2*0 

46*86 

3*6 

— 

84*34 

0-5 

— 

11*71 

2*1 

49*20 

3*7 

— 

86*68 

0*6 

r= 

14*06 

2*2 

= 

51*55 

3*8 

89*02 

0-7 

16*40 

2*3 

53*89 

3*9 

— 

91*36 

0-8 

18*74 

2*4 

56*23 

4*0 

= 

93*70 

0-9 

=r 

21*09 

2*5 

58*57 

4*1 

nr 

96*04 

1-0 

= 

23*43 

2*6 

60*92 

4*2 

— 

98*38 

M 

25*77 

2*7 

63*26 

4*3 

=Z 

100*72 

1-2 

— 

28*12 

2*8 

65*62 

4*4 

— 

103*06 

1-3 

— 

30*46 

2*9 

67*95 

4*5 

nr 

105*40 

14 

— 

32*80 

3*0 

70*29 

4*6 

nr 

107*74 

1-5 

.35*14 

3*1 

72*63 

4*7 

nr 

110*08 

1-6 

37*49 

3*2 

= 

74*98 

4*8 

nr 

112*42 

CONFECTIONERS’  RAW  MATERIALS.  855 


Non-Fatty  Solids  in  : 

Terms  of 

Standard. 

Non-Fatty 

Percentage 

X'on-Fatty 

Percentage 

Non-Fatty 

Percentage 

Solids 

of 

Solids 

of 

Solids 

of 

per  cent. 

Standard. 

per  cent. 

Standard. 

per  cent. 

Standard . 

4-8 

9-6 

64 

= 

12-8 

8-0 

=z: 

16-0 

4-9 

= 

9-8 

6-5 

z= 

13-0 

84 

= 

16-2 

5-0 

— 

10-0 

6-6 

= 

13-2 

8-2 

164 

5-1 

= 

10-2 

6-7 

134 

8*3 

16-6 

5-2 

104 

6-8 

nr 

13-6 

84 

= 

16*8 

5-3 

10-6 

6-9 

= 

13-8 

8-5 

z=; 

17-0 

54 

ZIZ 

10-8 

7-0 

=: 

14-0 

8-6 

z= 

17-2 

5-5 

= 

11-0 

7*1 

=z 

14*2 

8*7 

1= 

174 

5-6 

11-2 

7-2 

— 

144 

8-8 

= 

17-6 

5-7 

114 

7-3 

14-6 

8*9 

z= 

17-8 

5-8 

11-6 

74 

:z= 

14-8 

9-0 

18-0 

5-9 

11-8 

7*5 

:= 

15-0 

94 

— 

18-2 

6-0 

=z 

12-0 

7*6 

z= 

15-2 

9*2 

=Z 

184 

6-1 

12-2 

7*7 

= 

154 

9-3 

— 

18-6 

6-2 

= 

124 

7-8 

= 

15-6 

94 

=Z 

18-8 

6-3 

= 

12*6 

7-9 

15-8 

9-5 

19-0 

In  the  Table  on  page  856  are  given  the  results  of  analysis  of  some 
typical  examples  of  milk,  their  values  in  terms  of  standard  and  per  gallon, 
assuming  standard  milk  to  be  worth  lOt?.  per  gallon. 

Attention  is  drawn  to  the  fact  that  milk  No.  7,  although  of  highest 
value  in  terms  of  standard,  shows,  nevertheless,  evidence  of  having  been 
watered,  and  would  probably  be  made  the  subject  of  a prosecution  if  analysed 
for  the  purposes  of  the  Foods  and  Drugs  Acts.  The  public  analyst  is  con- 
cerned simply  with  adulteration,  while  the  commercial  user  is  more  vitally 
interested  in  the  Cjuestion  of  actual  value. 

A gallon  of  milk  weighs  approximately  about  10-3  lbs.  or  10  lbs.  5 ozs.^ 
and  if  this  be  bought  at  10c?.,  the  purchaser  gets,  if  the  milk  is  of  standard 
value,  0-36  lbs.  = 5-76  ozs.  of  butter  fat,  for  which  he  pays  8 -26?.,  or  at 
the  rate  of  2'2-ld.  per  lb.  ; and  0-93  lbs.  = 14-88  ozs.  of  mixed  protein^ 
milk-sugar,  and  ash  ; for  which  he  pays  l-8(i.,  or  at  the  rate  of  l-9c?.  per  lb. 

A gallon  of  separated  milk  of  standard  value  weighs  about  10-5  lbs.  or 
10  lbs.  8 ozs.,  and  if  this  be  bought  at  2Jc?.,  the  purchaser  gets  0-03  lbs.  = 
0-48  ozs.  of  butter  fat  and  0-945  lbs.  = 15-1  ozs.  of  mixed  protein,  milk- 
sugar,  and  ash,  making  0-975  lbs.  of  total  solids,  which  he  buys  at  the  rate 
of  2’56d.  per  lb. 

Taking  butter,  containing  87  per  cent,  of  butter  fat,  at  Is.  per  lb.,  then — 

One  gallon  of  separated  milk,  costing  . . . . 2^d. 

And  0’33  lbs.  of  butter,  costing  . . . . . . 4Jc?. 


Together  costing  . . . . . . . . 7c?. 

will  yield  the  equivalent  in  quantity  of  the  total  non-fatty  solids,  and  butter- 
fat  of  one  gallon  of  new  milk  costing  10c?. 

939.  Condensed  Milk. — Condensed  milks  of  the  unsweetened  variety 
are  at  times  employed  instead  of  new^  or  separated  milks.  In  ascertaining 
the  value  of  these,  it  is  well  to  dilute  them  to  three  times  their  original 
volume.  Then  such  a milk  as  No.  9 is,  as  nearly  as  possible,  of  the  same 
degree  of  coifcentration  as  standard  milk.  One  gallon  of  such  milk,  in  the 
concentrated  form,  is  worth,  as  against  standard  milk, 

9-8  X 3 = 28 •4(?.  per  gallon. 


856 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


No. 

Description  of  Milk.  i 

Com- 

position. 

Value 
in  terms 
of 

Stand- 

ard. 

Value 

per 

Gallon. 

1 

Milk  with  26  per  cent,  of  added  water 

( Fat  . . . . 

( Solids  not  fat  ’ 

3-2 

()-6 

74-98 

13-20 

9-8 

88-18 

8-8d. 

2 

Milk  deprived  of  40  per  cent,  of  its  cream 

(Fat  . . . . 

1 Solids  not  fat 

1-8 

91 

42-17 

18-20 

1 

10-9 

60-37 

6-Od. 

3 

Old  Somerset  House  limit,  below  which  I Fat  . . . . 

2-5 

58-57 

milks  were  considered  adulterated 

1 Solids  not  fat 

8-5 

17-00 

11-0 

75-57 

7-5d. 

4 

Present  Government  limit 

(Fat  . . . . i 

1 Solids  not  fat 

3-0 
8-5  1 

1 

70-29 

17-00 

11-5 

87-29 

8-7d. 

5 

Author’s  conventional  standard 

f Fat  . . . . 

] Solids  not  fat 

3-5 

9-0 

82-00 

18-00 

12-5 

100-00 

10 -Od. 

6 

Average  composition  of  pm’e  new  milk 

( Fat  . . 

( Solids  not  fat 

I 4-0 
‘ 8-8 

1 93-70 
17-60 

12-8 

111-30 

1 11-ld. 

7 

Very  rich  milk  slightly  watered 

(Fat  . . 

( Solids  not  fat 

4-3 
^ 8-1 

100-72 

16-20 

12-4 

1116-92 

11 -7d. 

8 

High  quahty  sample  of  skimmed  milk 

( Fat  . . 
t Solids  not  fat 

' 0-4 

1 9-1 

9-37 
j 18-20 

9-5 

27-57 

2-7  ad. 

9 

Unsweetened  condensed  milk  diluted  to  ( Fat  . . 

3-5 

82-00 

three  times  its  volume 

. ] Solids  not  fat 

! 8-2 

! 16-40 

11-7 

I 

j 98-40 

9-8d. 

10 

Unsweetened  condensed  milk  diluted  to 

( Fat  . . 

; 2-0 

1 46-86 

three  times  its  volume 

, t Solids  not  fat 

8-6 

i 17-20 

10-6 

i 64-06 

6-4d. 

No.  10  has  been  deprived,  before  condensing,  of  nearly  half  its  fat,  and  con- 
sequently is  only  worth 

6-4  X 3 = 19-0(^.  per  gallon. 

Such  condensed  milks  may  not  only  be  diluted  and  used  as  moistening 
agents,  but  also  at  times  are  employed  in  their  concentrated  state,  as  a 
more  or  less  complete  substitute  for  butter.  These  condensed  milks  have, 
or  should  have,  an  approximate  density  of  IT,  and  therefore  a gallon  of 
No.  9 will  weigh  about  11  lbs.,  and  is  worth,  on  the  milk  standard,  or 

2-58(1.  per  lb.  A gallon  of  the  milk  will  contain,  roughly,  2-70  lbs.  of  non- 
fatty solids,  and  1T5  lbs.  of  butter  fat.  . This  is  the  equivalent  in  quantity 


CONFECTIONERS’  RAW  MATERIALS. 


857 


•of  2-85  gallons  of  separated  milk,  at  a cost  of  7Td.,  and  1-32  lbs.  of  butter 
which  at  Is.  per  lb.  costs  15-8(i.,  or  a total  of  22-9d.  Unless,  therefore, 
such  full  value  milk  as  No.  9 is  bought  at  2-OSd.  per  lb.,  its  proteins,  milk- 
sugar  and  fat,  can  be  more  cheaply  supplied  from  separated  milk  and  butter. 

940.  Milk  Powders. — ^By  modern  processes,  milk  is  now  reduced  to  the 
condition  of  a dry  powder,  and  is  an  article  of  sale  containing  only  a very 
• small  percentage  of  moisture.  Full  cream,  half  cream,  and  separated  milk 
powders  are  now  on  the  market.  In  the  absence  of  moisture,  these  bodies 
-have  the  following  approximate  composition  : — 

Composition  of  Milk  Powders. 


Constituents. 

Full-cream. 

Half-cream. 

Separated. 

Fat 

31  *2 

17-2 

3-2  1 

Proteins 

28-1 

34-0 

.39-8 

Sugar  . . 

35-2 

42-3 

49-5 

Ash 

5-5 

6-5 

7-5 

100-0 

! 100-0 

i 

100-0 

Weight  of  water  required  to  convert 

1 lb.  of  each  into  liquid  of  the  same 

strength  as  milk  . . 

7-8  lbs. 

9-3  lbs. 

10-7  lbs. 

One  pound  of  the  full-cream  powder  is  equivalent  in  butter  value  to 
about  5|  ozs.  of  butter  ; in  addition  to  which  it  contains  proteins  and 
sugar  in  approximately  the  same  quantities.  On  mixing  the  powders 
with  warm  water  in  the  proportions  given  above,  a fluid  corresponding  to 
the  original  milk  is  produced. 

941. — ^Eggs. — ^Next  to  milk,  eggs  are  one  of  the  most  important  moisten- 
ing agents  to  the  confectioner.  The  raw  white  of  egg  is  a viscous  glairy 
liquid,  the  yolk  being  somewhat  more  fluid  in  character.  In  composition, 
the  white  of  egg  consists  of  protein  matter  dissolved  in  water,  while  the 
yolk  contains  in  addition  to  protein,  fat  and  colouring  matter.  The  follow- 
ing table  gives  respectively  the  results  of  analysis  of  the  white,  yolk,  and 
whole  interior  of  the  egg  : — 


Constituents. 

White. 

Yolk. 

White  and  Yolk 
together. 

Water 

85-7 

50-9 

73-7 

Protein  . . 

12-6 

16-2 

14-8 

Fat 

0-25 

31-75 

10-5 

Ash  

0-59 

1-09 

1-0 

The  white  of  egg  may  be  viewed  as  a solution  of  one  part  of  albumin  in 
seven  parts  of  water,  while  in  the  whole  egg  about  two -fifths  of  the  solids 
consist  of  fat,  and  three-fifths  of  protein  matter.  The  water  of  the  whole 
egg  amounts  roughly  to  three-quarters  of  its  weight.  Or  putting  it  another 
way,  1 lb.  of  whole  eggs  contains  about  4 ozs.  of  solids,  and  I lb.  of  white  of 
egg  just  half  that  quantity  or  2 ozs.  When  either  of  these  are  used  in  making 


858 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


a dough  with  flour,  the  w ater  part  of  the  egg  does  the  moistening,  and  acts 
in  the  same  w ay  on  the  constituents  of  flour  as  w'ater  alone  w'ould  do.  The 
wiiite,  if  used  alone,  is  so  nearly  tasteless  that  it  cannot  be  said  to  confer  any 
very  decided  flavour  ; but,  as  w^as  remarked  with  regard  to  the  protein  matter 
of  milk,  it  imparts  the  property  described  as  that  of  niello wmess  to  goods 
in  whose  manufacture  it  is  used.  The  yolk,  on  the  other  hand,  is  very 
marked  in  flavour,  and  just  as  eggs  themselves  are  in  consequence  most 
pleasant  eating,  so  cakes  have  a remarkable  richness  of  flavour  caused  by 
the  yolks  of  eggs  used  in  their  manufacture. 

The  yellow  of  the  yolk  confers  its  distinctive  colour  on  the  cakes  and 
other  goods  in  which  it  is  employed  ; as  a consequence  the  full  yellow 
of  a cake  has  become  associated  with  the  idea  of  its  richness.  With 
cakes  made  at  very  low'  prices,  the  use  of  eggs  in  full  proportion  becomes  an 
economic  impossibility,  and  therefore,  in  the  cheaper  cakes,  an  effort  is 
made  to  please  the  eye  by  adding  artificial  colouring  matter.  The  nature 
and  composition  of  the  substances  used  for  this  purpose  are  described  in  a 
subsequent  paragraph. 

942.  Dried  Egg  Whites. — ^For  certain  purposes,  in  place  of  the  wLite  of 
eggs,  the  confectioner  has  offered  to  him  such  w'hites  as  desiccated  albumin. 
This  preparation  should  consist  of  the  pure  fresh  wLite  of  egg  evaporated 
dow'n  to  dryness  at  a temperature  w'ell  below'  that  of  the  coagulation  or 
setting  of  albumin.  Such  dried  albumin  should  soften  on  tlie  addition  of 
W'ater  and  form  a solution  possessing  the  same  properties  as  fresh  w'hite  of 
egg.  The  solution  should  be  free  from  any  unpleasant  taste  or  odour  of 
decomposition.  As  w'hite  of  egg  contains  one-eighth  its  w'eight  of  pure 
albumin,  it  follow'S  that  dried  egg-albumin  should,  everything  else  being 
equal,  be  worth  w'eight  for  w'eight  eight  times  as  much  as  fresh  w'hite  of  egg. 
In  other  words,  pure  egg-albumin  at  anything  below  eight  times  the  cost 
of  white  of  egg  is  economically  to  be  preferred  to  such  fresh  w'hites.  The 
objections  to  such  commercial  albumin  are  first,  that  it  may  be  partly  coagu- 
lated, and  second,  that  it  may  be  unpleasant  in  odour  or  taste  either  as  the 
result  of  preparation  from  unsound  eggs,  or  incipient  putrefaction  during 
its  manufacture.  Among  adulterants,  to  which  dried  egg-w'hites  are  subject, 
are  dextrin,  sugar,  and  gelatin.  Serum-  or  blood-albumin,  is  less  expensive 
than  egg-albumin,  and  so  may  possibly  be  substituted  for  it  w'ithout  declara- 
tion to  the  purchaser. 

The  table  on  the  follow'ing  page  gives  the  results  of  analysis  of  a number 
of  samples  of  dried  egg-whites,  together  w'ith  that  of  fresh  w'hite  of  egg 
taken  for  comparison.  A 5 per  cent,  solution  of  the  pow'dered  albumin  in 
cold  w ater  was  prepared  and  filtered  through  paper.  The  total  solid  matter, 
and  nitrogen  by  Kjeldahl’s  method,  w'ere  determined  on  the  filtrate. 
Another  portion  of  the  filtrate  w'as  acidulated  with  acetic  acid,  and  boiled 
so  as  to  coagulate  the  albumin,  which  was  in  turn  filtered  off.  The  re^ 
sidual  soluble  matter  and  nitrogen  w'ere  then  determined  in  the  second 
filtrate.  In  each  case  the  nitrogen  multiplied  by  the  factor  6-25  gave  a 
([uantity  which  did  not  amount  to  as  much  as  the  total  matter  present.  The 
difference  is  therefore  returned  as  non-nitrogenous  matter. 

The  samples  1 , 2,  and  3 w'ere  specimens  of  commercial  dried  egg-whites  : 
<i  W'as  the  w4iite  of  fresh  egg,  and  a a the  results  of  the  same  analysis  calculated 
to  what  they  would  have  been  on  the  same  w'hite  dried  to  a w-ater-content  of 
15  per  cent.,  without  other  change. 

Tlie  fresh  w'hite  of  egg  was  diluted  to  about  the  same  degree  of  concen- 
tration as  the  5 per  cent,  solution  before  analysis.  While  the  fresh  egg-white 
W'as  perfectly  soluble,  the  dried  albumins  contained  insoluble  matter  vary- 
ing from  5-70  to  10-72  per  cent.  This  is  probably  albumin  which  had  been 


CONFECTIONERS’  RAW  MATERIALS. 


859 


Constituents.  ' 

1 

1.  1 

1 

2. 

3. 

1 

a d. 

Water. . 

1 

18-10 

15-08 

15-08 

87-55 

15-00 

Insoluble  Matter 

5-70 

6-52 

10-72 

0-00 

0-00 

Coagulable  True  Albumin  . . . . j 

52-86 

52-27 

52-26 

8-92 

61-90 

Associated  Non-nitrogenous  Matter 
Non-coagulated  Nitrogenous  Matter, 

4-54 

4-53 

2-54 

0-56 

3-93 

as  Proteins 

Non-coagulated  Non-nitrogenous 

7-74 

8-15 

7-62 

1-15 

7-98 

Matter 

11-06 

13-45 

11-78 

1-62 

11-22 

coagulated  in  drying,  as  the  total  nitrogenous  matter  is  quite  up  to  the 
normal  amount.  The  insoluble  matter  and  coagulated  albumin  together 
agree  very  fairly  v ith  the  coagulated  albumin  of  a a.  The  protein  matter, 
which  remains  uncoagulated  under  the  conditions  of  the  experiment  is 
practically  the  same  in  all  samples.  The  non-coagulated  non-nitrogenous 
matter  in  the  egg-white  is  more  than  is  usually  given,  and  cannot  be  ac- 
counted for  b}"  assuming  the  factor  used  for  proteins  to  be  too  low.  It  will 
be  seen  that  the  amount  is  practically  the  same  in  all  the  samples.  Adultera- 
tion with  sugar  or  dextrin  would  materially  increase  this  figure,  while  the 
addition  of  gelatin  would  augment  the  non-coagulated  nitrogenous  matter. 
The  whole  of  these  three  samples  may  be  regarded  as  genuine,  but  in  the 
act  of  drying  varying  amounts  of  proteins  have  been  rendered  insoluble. 

943.  Moistening  Effect  of  Fat. — Before  altogether  passing  from  moisten- 
ing action,  mention  may  be  made  of  the  moistening  effect  of  melted  fat,  as 
butter  or  lard.  Such  moistening  is  quite  different  in  character  from  that 
of  substances  whose  essential  moistening  constituent  is  water.  The  latter 
all  affect  the  gluten  of  flour,  and  produce  a dough  such  as  is  used  in  making 
bread  ; the  former  makes  a moist  mass,  devoid  altogether  of  any  tenacity, 
but,  instead  of  that,  distinctly  “ short.”  As  an  example  of  the  use  of 
butter  fat  as  a moistening  agent  Scotch  shortbread  may  be  mentioned. 

944.  Glycerin. — ^In  another  sense  of  the  word  “ moistening,”  glycerin 
must  be  referred  to  as  one  of  the  confectioners’  moistening  agents.  Glycerin 
is  well  Imown  as  a colourless,  odourless,  and  viscous  liquid,  of  a very  sweet 
taste.  Its  chemical  composition  and  properties  are  described  in  paragraph 
104.  If  exposed  to  the  air,  glycerin  increases  in  volume  through  absorption 
of  moisture.  When  used  in  small  quantities  in  cakes,  the  result  is  that 
drying  is  much  retarded,  and  the  cake  remains  moist  and  fresh  for  a consider- 
able time  longer  than  would  otherwise  be  the  case.  As  glycerin  is  without 
injurious  effect  on  the  human  economy,  its  use  in  this  direction  may  be 
regarded  as  perfectly  harmless. 

Aerating  Ingredients. 

945.  Aerating  Agents. — A number  of  these  bodies,  such  as  bicarbonate 
of  soda,  cream  of  tartar,  tartaric  acid,  and  similar  substances  have  already 
been  fully  described  in  Chapter  XVIII.,  paragraph  601. 

946.  Aerating  Action  of  Eggs. — It  is  well  known  that,  under  certain 
circumstances,  eggs  are  valuable  lightening  agents,  yet  they  do  not  give 
off  any  gas  whatever  within  the  range  of  temperature  employed  by  the  con- 
fectioner, neither  do  they  cause  evolution  of  gas  from  any  other  ingredients 
he  is  in  the  habit  of  using.  In  these  particulars  they  differ  markedly  from 
tlxe  aerating  agents  before  referred  to,  and  their  action  must  consequently 


860 


THE  TECHNOLOGY  OE  BREAD-MAKING. 

be  looked  for  in  some  other  direction.  First  of  all,  eggs,  and  especially 
their  whites,  have  a peculiar  glairy  consistency.  In  virtue  of  this,  if  eggs 
be  present  in  a mixture,  any  air  incorporated  with  it  prior  to  baking  is 
retained  much  more  tenaciously.  Consequently,  when  the  goods  are  placed 
in  the  oven,  such  air  expanding  with  increase  of  temperature,  increases 
the  volume  of  the  articles  by  its  more  perfect  retention,  as  a result  of  the 
peculiar  viscous  and  binding  nature  of  the  egg-albumin.  Another  valuable 
property  of  eggs,  so  far  as  this  effect  is  concerned,  is  that  of  setting  or  coagu- 
lation. Just  as  in  being  boiled,  the  egg  matters  become  solid  during  the 
act  of  baking  : as  the  temperature  of  coagulation  is  reached  they  begin  to 
set,  and  so  fix  the  dough,  so  to  speak,  in  its  expanded  state.  The  lightening 
function  of  eggs  is  therefore  summed  up  in  the  statement  that  they  do  not  of 
themselves  evolve  or  cause  the  evolution  of  gas,  but  assist  in  its  retention 
when  developed  by  the  expansion  of  air,  or  obtained  from  any  other  gaseous 
source. 


Enriching  Ingredients. 

947.  Fats. — ^The  next  step  to  be  considered  is  that  of  enriching  a cake, 
an  operation  which  is  performed  by  the  addition  and  incorporation  of  fat. 
Scotch  shortbread  dough  is  an  instance  of  dough  made  with  fat  as  a moisten- 
ing agent.  The  dough  itself  is  short  and  non-coherent,  while  the  baked 
shortbread  is  extremely  rich  in  flavour  and  character.  As  fats  fulfil  so 
important  a function,  it  becomes  necessary  to  inquire  into  the  properties 
of  the  bodies  embraced  under  this  general  heading  of  fat.  Reference  has 
already  been  made  in  Chapter  V.  to  the  composition  and  some  of  the  pro- 
perties of  fats,  but  at  this  stage  a somewhat  more  extended  description  is 
advisable. 

Under  this  name  are  included  a number  of  substances,  both  of  animal 
and  vegetable  origin.  The  fats  have  various  melting  temperatures  and, 
speaking  broadly,  those  which  are  solid  at  the  ordinary  temperature,  are 
called  “ fats,”  while  those  which  under  this  condition  are  liquid  receive  the 
name  of  “ oils.”  Pure  fats  and  oils  are  usually  either  colourless  or  of  a 
faint  yellow  tinge,  while  some  of  vegetable  origin  possess  a green  tint,  de- 
rived from  green  vegetable  colouring  matter.  Many  fats  and  oils  possess  a 
distinct  smell  and  taste,  agreeable  or  otherwise,  and  indicative  of  their 
origin  ; such  characters  appertain,  however,  to  minute  traces  of  associated 
impurities,  rather  than  to  the  pure  fat  and  oil  itself.  Consequently,  the 
act  of  refining  and  purifying  oils  generally  tends  to  deprive  them  of  special 
flavour,  leaving  behind  a bland  and  almost  tasteless  body.  All  ordinary 
fats  and  oils  possess  the  property  of  “ greasiness  ” ; if  dropped  in  the  liquid 
state  on  paper  or  cloth,  they  produce  a grease  spot,  and  give  that  well-known 
“ slipperiness  ” so  characteristic  of  a greased  surface. 

Oils  and  fats  are  practically  insoluble  in  water,  somewhat  soluble  in 
absolute  alcohol,  or  even  strong  spirit,  especially  when  hot.  Ether,  chloro- 
form, light  petroleum  or  petroleum  spirit,  and  other  somewhat  analogous 
substances  dissolve  them  readily  ; so  also  the  various  oils  and  fats  are 
readily  soluble  in  each  other,  and  consequently  may  easily  be  mixed  in 
all  proportions.  Viewed  themselves  as  solvents,  they  have  practically  no 
action  on  most  of  the  substances  employed  by  the  confectioner.  Thus 
tlie  constituents  of  flour  are  not  dissolved  by  oil,  and  this  is  the  reason  of 
tlie  particular  “ shortness  ” of  flour  mixtures,  such  as  shortbread  dough, 
into  w'hich  any  fat  has  largely  entered.  Oil  dissolves  some  colouring  matter, 
and  also  flavourings,  so  that  these  amalgamate  somewhat  readily  with  the 
fatty  part  of  various  mixtures. 

Fat  and  oils,  if  preserved  from  the  atmosphere,  remain  unchanged  for  a 
considerable  time,  but  on  exposure  are  hable  to  acquire  the  property  of 


CONFECTIONERS’  RAW  MATERIALS. 


861 


rancidity.  This  is  much  hastened  by  the  presence  of  impurities  resulting 
from  imperfect  separation  from  the  animal  or  vegetable  source  of  origin. 
Natural  fats  may  be  viewed  as  compounds  of  the  higher  fatty  acids  with 
glycerin,  or  some  closely  allied  body.  Among  the  fatty  acids  most  fre- 
quently occurring  are  those  of  the  stearic  series,  represented  by  the  general 
formula  HC„H2„.i02,  and  the  oleic  series  represented  by  HC,iH2„.302. 
This  mutton  fat  is  largely  composed  of  stearate  of  glycerin,  which  body 
may  be  artificially  produced  by  heating  together  glycerin  and  stearic  acid 
thus, 

3HC18H35O2  + ChHslHOja  = C3H5(Ci8H3502)3  + 3H2O. 

Stearic  Acid.  Glycerin.  Glycerin  Stearate.  Water. 

This  body,  glycerin  stearate,  is  conveniently  called  “ stearin.” 

Olive  and  lard  oils  consist  largely  on  the  other  hand  of  glycerin  oleate  : 
the  formula  of  oleic  acid  is  HC13H33O2,  and  the  oleate  is  consequently 
€3115(018113302)3.  This  body  has  received  the  name  of  ‘‘olein.” 

Stearin  is  a somewhat  hard  solid,  while  olein  is  liquid  at  ordinary 
temperatures  ; as  may  be  surmised,  therefore,  stearin  and  allied  bodies  are 
more  largely  found  in  fats,  while  oils  consist  principally  of  olein  and  its 
congeners. 

948.  Melting  and  Solidifying  Points. — ^The  temperatures  at  which  these 
changes  occur  are  of  considerable  importance  in  the  selection  of  fats  for 
different  purposes  ; a fat  when  once  melted  remains  liquid  at  a considerably 
lower  temperature  than  that  required  for  the  act  of  fusion.  Thus  mutton 
fat  melts  at  a temperature  ranging  between  46-5  and  47-4°  C.  ; but  when 
once  melted  only  re-solidifies  at  a temperature  of  from  32  to  36°  0.  In 
the  table  following  later,  the  temperatures  of  solidification  are  given.  At 
temperatures  varying  from  250°  C.  (482°  E.)  To  300°  C.  (572°  F.),  fats  are 
decomposed,  yielding  various  products  of  a disagreeable  odour. 

949.  Specific  Gravity  of  Fats. — ^These  bodies  are  all  of  them  lighter  than 
water,  the  specific  gravity  varying  between  875  and  970,  water  being  taken 
at  1000.  The  specific  gravity  is  a valuable  means  of  identifying  and  distin- 
guishing fats,  and  consequently  has  been  determined  with  considerable  care. 
As  the  oils  are  liquid  at  ordinary  temperature,  and  the  fats  solid,  it  is  prefer- 
able to  select  some  temperature  at  which  all  are  in  the  liquid  state.  That 
found  most  generally  convenient  is  the  temperature  caused  by  immersion 
in  boiling  water,  and  this  in  practice  registers  at  99°  C.  The  figures  given 
in  the  subsequent  table  have  been  taken  at  this  temperature  ; they  are 
somewhat  abnormal,  as  they  give  the  specific  gravity  of  the  fats  at  99°  C. 
compared  with  water  at  15-5  C. 

950.  Chemical  Constants  of  Fats. — ^There  are  various  data  used  by  the 
chemist  in  recognising  different  fats,  and  detecting  adulterations.  Among 
these  are  the  following  : — 

951.  Iodine  Value. — ^This  term  is  applied  to  a most  important  deter- 
mination now  made  on  fats  as  the  result  of  investigations  by  Hubl.  If 
any  fat  or  oil  be  dissolved  in  chloroform,  and  then  an  excess  of  a solution 
of  iodine  and  mercury  chloride  in  alcohol  added,  absorption  of  the  iodine 
by  the  fatty  matter  proceeds.  Losing  proper  precautions,  the  amount  of 
iodine  so  absorbed  is  capable  of  very  exact  measurements,  and  the  figure 
thus  obtained  is  that  quoted  as  the  “ iodine  value.”  Thus,  if  the  iodine 
value  of  a fat  is  given  as  50,  this  means  that  under  the  standard  conditions 
of  what  is  known  as  Hubl’s  test,  100  parts  of  that  fat  absorb  50  parts  of 
iodine.  The  iodine  value  not  only  throws  light  on  the  probable  nature  of 
an  oil  or  fat,  but  also,  in  many  instances,  affords  valuable  indications  of  the 


862 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


I^urity  and  quality  of  the  fat  in  question.  Speaking  generally,  the  more 
oily  a fat,  the  higher  is  its  iodine  value. 

952.  Reichert-Meissl  Value. — ’Fats  have  already  been  referred  to  as 
compounds  of  fatty  acids.  Of  this  group  of  bodies  some  are  readily  volatile 
at  the  temperature  of  boiling  water,  while  others  are  non-volatile  under  the 
same  conditions.  Butter  fat  is  distinguished  from  almost  all  other  fats  by 
containing  a high  proportion  of  such  volatile  acids.  The  exact  determina- 
tion of  the  volatile  acids  in  a fat,  is  a work  of  tediousness  and  some  difficulty. 
But  under  standard  conditions,  a fairly  constant  fraction  of  such  volatile 
acids  can  be  obtained  and  determined,  and  this  constitutes  a test  of  con- 
siderable importance.  A weighed  quantity,  5 grams  of  the  fat,  is  made 
into  a soap,  by  treatment  with  excess  of  potash  ; on  adding  excess  of  sul- 
phuric acid,  this  soap  is  decomposed,  and  the  whole  of  the  fatty  acid  liber- 
ated. The  solution  is  altogether  diluted  with  water  to  140  cubic  centimetres, 
and  then  distilled  until  110  cubic  centimetres  of  the  distilled  liquid  have 
been  collected.  The  acidity  of  this  filtered  distillate  is  then  determined  by 
the  use  of  phenolphthalein  and  decinormal  potash  solution.  Such  acidity  is 
termed  the  Reichert-Meissl  value.  Thus,  if  5 grams  of  butter  fat  gave 
a distillate,  which  took  30  cubic  centimetres  of  decinormal  potash  to 
render  it  neutral,  then  the  Reichert-Meissl  value  of  such  fat  would  be  said 
to  be  30.  This  figure  is  evidently  the  measure  of  the  quantity  of  vola- 
tile acid  which  distils  over  under  certain  standard  conditions. 

953.  Butyro-Refractometer  Value. — ^Like  other  transparent  substances, 
melted  fats  have  a refractive  action  on  a ray  of  light  passing  obliquely 
through  a layer  of  them.  The  amount  of  such  refraction  is  fairly  constant 
for  some  fats,  but  varies  however  with  the  temperature.  The  instrument 
known  as  Zeiss’  butyro-refractometer  is  one  for  rapidly  measuring  the 
amount  of  such  refraction.  On  looking  through  the  optical  portion  of  such 
an  instrument,  the  point  of  refraction  is  shown  by  means  of  a scale,  and 
can  be  read  off  at  once  into  degrees,  which,  for  example,  may  be  called 
47°.  The  instrument  is  also  provided  with  a thermometer,  graduating  into 
arbitrary  degrees,  and  this  is  also  read  at  the  same  time  as  the  point  of  re- 
fraction of  the  fat.  Suppose  that  this  figure  is  also  47°  ; then  in  the  case 
of  a butter  for  which  this  determination  is  principally  used,  the  difference 
between  the  two  is  0°,  and  such  butter  fat  is  at  the  bottom  limit  of  an 
arbitrary  scale  of  purity.  If  the  reading  on  the  butter  fat  is  lower  than 
that  of  the  thermometer,  then  the  butter  so  far  as  this  test  goes  is  passed 
as  pure  : if  higher,  then  the  butter  is  suspicious,  and  requires  to  be  further 
and  more  systematically  tested.  The  following  figures  were  obtained 
during  actual  examination  of  various  butters  : — 

Butter  reading  . . . . 46*4  44*0  50-0  52*5 

Thermometer  reading  . . 47*0  45*9  47*1  47*1 


-0*6  -1-9  +2-9  +54 


Of  these  tests,  the  two  former  were  pure  butters,  the  third  was  a mar- 
garine, and  the  fourth  a beef-fat  preparation.  By  means  of  the  arbitrarily 
marked  thermometer,  the  disturbing  influence  of  temperature  is  eliminatecl, 
as  minus  results  indicate  purity  of  butter  fat,  and  plus  results  impurity. 
Otlierwise  it  becomes  necessary  to  give  both  the  butter  readings  and  the 
temperature  of  the  fat  when  it  was  taken,  after  which  such  readings  must  be 
c-alculated  and  corrected  to  a given  temperature.  Thus  at  25°  C.  genuine 
butters  have  a range  of  from  49-5  to  54-0°,  and  margarines  of  from  58*6  to 
664°. 


COXFECTIOXERS’  RAW  MATERIALS, 


8(33 


864 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


954.  Tabular  Description  of  Oils  and  Fats. — ^In  the  table  on  the  preceding 
page  particulars  are  given  of  the  various  fats  and  oils  either  directly  used 
by  the  confectioner  or  indirectly  as  component  parts  of  various  butter  sub- 
stitutes or  other  confectioners’  fats.  For  these  data  and  their  arrangement 
the  authors  are  indebted  to  Allen’s  Commercial  Organic  Analysis ^ and 
Lewkowitsch’s  Analysis  of  Oils  and  Fats. 

955.  Butter. — 'There  can  be  little  doubt  that  where  prime  cost  is  no 
object,  butter  is  by  far  the  best  and  most  pleasant  fat  to  be  used  for  the 
great  majority,  if  not  all,  of  confectioners’  purposes.  Substitutes  for  butter 
will  succeed  or  fail  according  to  the  degree  in  which  they  reproduce  and 
possess  the  characteristics  of  good  butter.  Butter  is  therefore  first  de- 
scribed, and  other  substances  which  follow  are  naturally  compared  with 
and  tested  against  butter  as  a standard. 

Butter  may  be  defined  as  the  substance  produced  by  churning  the  cream 
derived  from  milk.  During  this  process  the  fat  globules  coalesce,  and  after 
washing  and  other  treatment,  result  in  the  production  of  butter. 

The  British  sources  of  butter  supply  include  Ireland,  France,  Denmark, 
Siberia,  Canada,  Australia,  and  New  Zealand.  The  last  of  these  devotee 
very  special  care  to  its  export  trade.  All  butter  for  export  purposes  is 
graded  by  the  State,  which  in  the  first  place  classifies  and  keeps  a register 
of  all  dairies.  The  Government  provides  cold  storage  rooms  at  specified 
ports,  in  which  the  latter  is  deposited  while  awaiting  shipment.  The  graders, 
who  are  as  a rule  picked  dairy  factory  managers,  examine  each  parcel,  and 
give  points  on  the  following  scale,  for  creamery  butter  : — 

Points. 

Flavour  . . . . . . . . . . . . . . 50 

Body,  moisture,  texture  . . . . . . . . . . 25 

Colour  . . . . . . . . . . . . . . . . 10 

Salting  . . . . . . . . . . . . . . 10 

Finish  . . . . . . . . . . . . . . . . 5 

100 

Butter  is  placed  in  the  first  grade,  which  secures  88  points  and  over ; 
in  the  second  grade,  under  88  points,  and  over  80  points  ; and  in  the  third 
grade,  with  80  points  and  under.  Of  creamery  butters  examined  and  graded 
in  1899-1900,  the  following  results  were  obtained  : — 

First  grade  . . . . . . . . . . 92*63  per  cent. 

Second  grade  . . . . . . . . . . 7*10  ,, 

Third  grade  . . . . . . . . . . 0*27  ,, 

Another  part  of  the  duties  of  the  port  graders  is  to  inspect  the  cold  stor- 
age accommodation  of  ships,  and  in  this  way  to  do  all  they  can  to  see  that 
such  produce  has  a good  send-off  from  colonial  shores.  Its  well-being  in 
this  country  is  attended  to  by  the  Produce  Commissioner,  who  sees  that  all 
is  well  on  arrival  here,  notes  critically  any  defects,  and  reports  them  to 
New  Zealand  for  remedying  in  the  future.  It  has  been  thought  well  to 
thus  explain  in  detail  the  organised  precautions  taken  to  ensure  for  this 
country  a supply  of  the  finest  possible  colonial  butter. 

956.  Composition  of  Butter. — -However  well  and  carefully  made,  butter 
contains  a good  deal  else  than  pure  fat  ; among  such  other  matters  being 
water,  proteins,  and  milk-sugar — usually  classed  together  in  analysis  as 
curd,  traces  of  natural  mineral  matter,  and  more  or  less  added  salt.  For 
confectioners’  purposes  the  water  is  useless.  The  presence  of  large  quan- 
tities of  curd  in  butters  is  general  evidence  of  inefficient  manufacture,  and 
excess  of  protein  matters  by  their  rapid  alteration  confers  an  unpleasant 


! 

i 

I CONFECTIONERS’  RAW  MATERIALS.  865 

cheesy  taste.  Salt  is  added  as  a preservative,  and  also  as  a flavouring 
agent  ; but  as  such  is  of  no  service  to  the  confectioner,  who,  as  a matter  of 
fact,  when  using  a salt  butter,  will  usually  wash  the  salt  out  as  completely  as 
possible  as  a preliminary  to  its  employment.  The  user  is  thus  reduced  to 
the  fat,  and  practically  that  is  the  substance  in  butter  of  value  : everything 
else  being  equal,  the  greater  the  proportion  of  fat  the  more  valuable  is  the 
butter. 

A reference  to  the  table  already  given  will  show  that  butter  differs 
from  every  other  fat  quoted  in  the  very  high  Reichert -Meissl  value  it  pos- 
sesses. As  already  explained,  this  flgure  is  an  indication  of  the  amount  of 
volatile  fatty  acids  present.  These  substances  give  butter  those  character- 
istic properties  not  exhibited  by  any  other  fat.  Therefore,  the  determina- 
tion of  Reichert-Meissl  value  is,  in  the  case  of  butters,  a most  important 
estima'tion.  In  the  table  on  page  866  are  given  the  results  of  analyses  of 
various  typical  butters  which,  except  when  otherwise  stated,  have  been 
made  by  the  authors. 

Samples  Nos.  6 to  12  are  fair  average  samples,  and  not  in  any  way  picked 
or  choicest  butters  of  their  kinds.  Looking  at  the  whole  series,  the  New 
Zealand  butters  are  characterised  by  containing  the  lowest  percentage  of 
water,  and  highest  of  butter  fat.  The  Canadians  and  Australians  also  are 
very  low  in  water,  while  next  follow  the  Siberian  samples.  The  Irish  butters 
are  marked  by  a large  percentage,  both  of  water  and  salt. 

The  Reichert-Meissl  value  of  the  butters  varies  from  about  26  to  over 
31  ; the  whole  of  these  figures  being  within  the  recognised  limits  of  purity. 
But  evidently  a butter  with  a value  of  31  must  be  richer  in  volatile  acids 
than  is  one  with  26,  and  will  be  found,  if  the  term  may  be  coined,  to  be  the 
more  “ buttery  ” butter  of  the  two.  In  confectioners’  valuation  of  butters, 
a high  Beichert-Meissl  value  is  of  importance  since  the  fullness  of  butter  fla- 
vour indicated  will  enable  such  a butter  to  be  mixed  with  a considerable 
proportion  of  a neutral  character  fat,  such  as  lard,  and  yet  be  as  “ buttery  ” 
in  character  as  another  butter  containing  normally  a low  proportion  of 
volatile  fatty  acids. 

957.  Butter  Standards. — One  of  the  data  given,  it  will  be  noticed,  is  the 
value  in  percentage  of  “ Standard.”  Taking  these  butters  right  through, 
it  was  found  that  many  samples  contained  87  per  cent.,  or  over,  of  butter 
fat.  This  figure  87  was  accordingly  taken  as  a standard  for  butter.  In  the 
following  table  is  given,  in  column  two,  the  value,  in  terms  of  the  standard. 


Valuation  of  Butters. 


Per- 
centage of 

Fat. 

70  .. 

Value  in 
Terms  of 
Standard. 

804 

Quantity  contain- 
ing same  weight 
of  Fat  as  100  lbs. 
of  Standard. 

124-3 

71  .. 

81-6 

122-5 

72  . . 

82-7 

120-8 

73  . . 

83-9 

119-1 

74  . . 

85-0 

117-5 

75  .. 

86-2 

. . 116-0 

76  . . 

87-3 

114-4 

77  .. 

88-5 

112-9 

78  . . 

89-6 

111-5 

79  . . 

90-8 

110-1 

80  . . 

91*9 

108-7 

81 

934 

107-4 

82  . . 

94-2 

. . 106-0 

Per- 
centage of 

Fat. 

83 

Value  in 
Terms  of 
Standard. 

95-4 

Quantity  contain- 
ing same  weight 
of  Fat  as  100  lbs. 
of  Standard. 

104-8 

84 

96-5 

103-5 

85  . . 

97-7 

102-3 

86  . . 

98-8 

101-1 

87  . . 

100-0 

. . 100-0 

88  . . 

101-1 

98-8 

89 

102-3 

97-7 

90  . . 

103-4 

96-6 

91  .. 

104-6 

95-6 

92  . . 

105-7 

94-5 

93  . . 

106-8 

93-5 

94  . . 

108-0 

92-5 

95  .. 

109-2 

91-5 

3 K 


866 


THE  TECHNOLOGY  OF  BREAD-MAKING. 
Analysis  of  Samples  of  Butter  and  Margarine. 

No.  Mark  or  Description. 

1.  English,  analysis  by  Richmond. 

2.  German,  salt  ,,  ,, 

3.  Danish,  salt  ,,  „ 

4.  Swedish,  salt  ,,  ,, 

5.  Australian,  salt  ,,  ,, 

6.  Danish. 

7.  Normandy,  fresh. 

8.  Normandy,  salt. 

9.  Canadian  (I.). 

10.  Canadian  (II.). 

11.  Australian. 

12.  New  Zealand. 

13.  Irish,  lowest  in  water  of  nine  samples. 

14.  Irish,  average  of  nine  samples. 

15.  Irish,  highest  in  water  of  nine  samples. 

16.  Siberian,  lowest  in  water  of  ten  samples. 

17.  Siberian,  average  of  ten  samples. 

18.  Siberian,  highest  in  water  of  ten  samples. 

19.  New  season  New  Zealand,  lowest  in  water  of  nine  samples. 

20.  New  season  New  Zealand,  average  of  nine  samples. 

21.  New  season  New  Zealand,  highest  in  water  of  nine  samples, 

22.  Margarine,  with  admixture  of  butter. 

23.  Margarine  (II.)  ,,  ,, 

24.  Margarine  (HI.),  without  butter. 

Composition  of  Butter  and  Margarine. 


|x„. 

Water. 

Salt. 

Curd 

(chiefly 

Casein). 

Fat. 

Total. 

Value  in  | 
percentage  of 
“ standard.” 

Reichert- 

Meissl 

Value. 

Butyro- 

refractometer 

Value. 

1 - 

11-6 

1-0 

0-6 

86-8  ' 

100-0 

89-6 

_ 

i 2 1 

12-3 

1-3  1 

1-2 

85-2 

100-0 

97-9 

— 

— 

13-4 

1-9 

1-3 

83-4 

100-0 

95-8 



— 

' ^ ; 

13-8 

2-0 

; 1-3 

82-9  1 

100-0 

95-3 

— I 

— 

5 ! 

12-7 

1-6 

1 

84-5 

100-0 

97-0 

— 

— 

6 1 

12-4 

1-4 

! 0-6 

85-6 

1 100-0 

1 98-3 

32-3 

- 1-9 

7 : 

12-4 

0-0 

1-7 

85-9 

; 100-0 

1 98-7 

31-1 

- 1-2 

10-6 

1-4 

0-8 

j 87-2 

100-0 

100-2 

31-1 

-1-0 

9 

9-7 

1-5 

1 0-6 

88-2 

100-0 

101-3 

28-6 

- 0-05 

10 

8-2 

1-7 

0-3 

89-8 

100-0 

103-3 

! 28-9 

+ M 

11 

i 11-8 

3-4 

1 0-4 

84-4 

100-0 

97-0 

1 31-0 

- 1-2 

12 

i 91 

2-8 

! 0-5 

87-6 

100-0 

100-6 

1 29-8 

1 -0-2 

! 13 

! 14-5 

4-6 

1 0-9 

80-0 

100-0 

91-9 

30-8 

i — 

14 

i 16-7 

6-2 

M 

76-0 

100-0 

87-3 

31-1 

— 

15 

* 19-8 

71 

1-0 

721 

100-0 

82-8 

31-6 

— 

16 

; 9-4 

; 1-0 

0-8 

88-8 

100-0 

102-0 

j 27-1 

— 

; 17 

' 10-3 

1 1-4 

M 

87-2 

100-0 

100-2 

26-7 

-0-5 

, 18 

i 11-3 

i 1-2 

1-2 

86-3 

100-0 

99-1 

1 26-9 

— 

i 10 

1 7-2 

! 1-2 

0-4 

91-2 

100-0 

104-8 

1 31-9 

-0-2 

: 20 

7-6 

i 1-2 

0-4 

90-8 

100-0 

104-3 

i — 

1 — 

1 *21 

1 8-1 

0-9 

1 0-3 

90-7 

100-0 

104-1 

1 30-4 

+ 0-9 

22 

13-2 

' 1-7 

! 3 0 

! 82-1 

100-0 

1 94-3 

1 5-7 

i +2-9 

23 

i 7-7 

. 1-7 

0-7 

89-9 

, 100-0 

103-1 

1 4-0 

1 

! 24 

1 

i G-7 

i 2-3 

0-2 

! 90-8 

1 100-0 

1 

104-2 

0-8 

+ 5-4 

of  butters  containing  various  percentages  of  fat.  Also  it  is  shown  in  column 
three  how  many  pounds  of  the  butter  are  required  to  yield  the  same  amount 
of  fat,  as  do  100  pounds  of  the  standard  butter. 


CONFECTIONERS’  RAW  MATERIALS. 


867 


Thus  supposing  that  a butter  has  only  72  per  cent,  of  fat,  then  everything 
else  being  equal,  it  is  only  worth  82-7  per  cent,  of  butter  of  standard  com- 
position. Further,  in  use  120-8  lbs.  of  that  butter  are  required  to  go  so 
far  in  fat  as  do  100  lbs.  of  the  standard.  Taking  on  the  other  hand  a butter 
Avith  92  per  cent,  of  fat,  such  butter  is  worth  105-7  per  cent,  of  standard, 
and  in  use  94-5  lbs.  only  are  required  to  go  so  far  as  100  lbs.  of  the  standard. 

958.  Weak  and  Strong  Butters. — In  working  butters,  there  is  one  point 
which  may  always  be  noted.  Some  butters  are  defined  as  weak,  while  others 
are  strong  and  waxy.  The  former,  on  warming,  readily  become  oily,  while 
the  latter  remain  tough  and  wiry.  If  paste  be  made  from  the  former,  the 
paste  does  not  rise  well,  while  the  melted  fat  drains  readily  from  the  hot 
goods.  The  tougher  butters  make  lighter  paste,  and  are  more  fully  retained 
by  the  articles  when  baking. 

Prior  to  use  in  confectionery,  butter  is  usually  “ creamed  : ” in  this 
operation  the  butter  is  beaten  until  of  the  consistency  of  cream.  The  opera- 
tion is  hastened  by  slightly  warming,  although  except  in  very  cold  weather 
such  is  not  absolutely  necessary.  This  act  of  creaming  consists  of  breaking 
down  the  butter  into  an  emulsion  in  which  both  the  fat  and  the  water  exist 
in  minute  globules. 

959.  Rancidity. — ^A  word  may  here  be  said  as  to  rancidity  in  butters ; 
and  on  this  point  some  interesting  data  are  given  by  Lewkowitsch,  of  which 
the  following  is  a summary.  When  kept  under  unfavourable  conditions, 
butter  acquires  a strong  acrid  is  unpleasant  flavour,  to  which  the  name 
of  rancidity  is  given.  At  the  same  time,  some  decomposition  of  the  fat  goes 
on,  and  part  of  the  fatty  acids  is  liberated  in  the  free  state.  This  alone 
does  not,  however,  produce  rancidity,  since  the  addition  of  free  fatty  acid 
to  an  oil  does  not  impart  a rancid  character,  although  it  gives  the  oil  a sharp 
taste.  It  has  been  surmised  that  bacteria  are  responsible  for  the  production 
of  rancidity,  but  this  has  been  disproved.  Neither  is  the  presence  of  mois- 
ture necessary,  since  dried  fats  are  more  liable  to  this  change  than  those 
containing  a certain  amount  of  moisture.  Rancidity  must  therefore  be 
considered  due  to  direct  oxidation  by  the  oxygen  of  the  air,  this  action 
being  intensified  by  exposure  to  light.  Both  oxygen  and  light  must  act 
simultaneously,  in  order  to  produce  rancidity,  either  of  these  agents  alone 
being  unable  to  cause  any  alteration  in  that  respect.  Solid  fats,  especially 
those  of  animal  origin,  are  less  liable  to  turn  rancid  than  liquid  fats.  With 
an  indication  of  the  causes  of  rancidity,  the  means  of  prevention  will  suggest 
themselves  to  the  user  of  fats. 

960.  Beef  Fat. — ^This  is  sometimes  found  in  the  well  known  form  of 
dripping,  but  does  not  by  itself  reach  the  confectioner  in  any  great  quantity. 
When  the  very  fatty  portions  of  the  carcase  are  heated,  the  fat  melts,  and 
separates  from  the  containing  tissues,  and  in  this  way  a pure  beef  fat  may 
be  obtained.  Like  many  other  animal  fats — that  of  beef  is  a mixture  of 
a harder  and  a softer  portion.  If  the  fat  be  gently  heated,  the  softer  part 
becomes  liquid,  while  the  harder  part  still  retains  its  solidity.  The  fat  in 
this  condition  may  be  enclosed  in  canvas  bags,  and  subjected  to  pressure  : 
the  more  liquid  portion  passes  through  and  constitutes  a body  known  in 
commerce  as  “ oleo,”  while  the  harder  part  remains  behind,  and  commer- 
cially is  termed  “beef  stearin.” 

961.  Hog  Lard. — ^Lard  is  obtained  from  the  fat  of  the  pig  in  much  the 
same  way  as  beef  fat  from  that  of  the  ox.  Lard  is  a white  fat  of  somewhat 
pleasant  taste  and  a soft  consistency.  Like  beef  fat,  it  may  be  separated 
by  warmth  and  pressure  into  lard  stearin  and  lard  oil.  The  fat  of  some 


868 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


portions  of  the  pig  is  much  harder  than  the  others,  consequently,  some  of 
the  fat  of  the  abdomen,  if  melted  down  separately,  gives  a much  harder  lard 
than  do  other  parts,  or  than  would  be  yielded  by  the  fat  of  the  whole  animal. 
The  harder  lards  are  found  to  contain  a larger  proportion  of  stearin  than 
do  those  of  softer  nature.  In  summer  and  very  hot  weather  there  is  con- 
siderable difficulty  in  cooking  with  the  softer  lards,  which  become  almost 
liquid.  In  order  to  get  over  this,  such  lards  may  be  fortified  by  the  addition 
of  stearin  of  either  lard  or  beef  fat.  Given  a soft  whole  hog  lard,  there 
can  be  little  doubt  that  its  cooking  properties  are  improved  by  the  addition 
of  stearin,  while  certainly  the  wholesomeness  is  in  no  way  deteriorated. 
The  only  point  is,  that  a purchaser  who  gives  the  price  for  the  more  expensive 
lard,  derived  from  the  harder  parts  of  the  pig,  has  a right  to  expect  to 
obtain  the  same,  and  not  a soft  whole  lard,  hardened  by  some  foreign  fat. 
Lards  are,  at  the  present  time,  almost  pure  fats  ; they  melt  into  a liquid, 
which  is  either  perfectly  clear,  or  only  slightly  turbid  through  the  presence  of 
a scarcely  weighable  quantity  of  unseparated  tissue.  The  chemist,  in  analys- 
ing lard,  directs  his  attention  principally  to  the  detection  of  foreign  fats  or 
oils.  In  doing  this,  the  iodine  value  is  of  much  assistance  to  him  ; the  harder 
fats,  as  beef  stearin,  having  a lower  value  than  lard,  while  most  oils  have 
a much  higher  value.  The  difficulty  here  is  that  a mixture  of  beef  stearin 
and  oil  may  be  so  arranged  as  to  have  the  same  iodine  value  as  pure  lard. 
The  microscope  is  called  into  requisition  in  order  to  detect  the  addition  of 
stearin,  since  in  samples  of  lard  dissolved  in  ether,  and  then  allowed  to 
recrystallise  out,  the  crystals  from  beef  stearin  differ  in  appearance  from 
those  of  lard  in  a state  of  purity.  These  crystals  are  not  only  microscopically 
examined,  but  also  separated  and  weighed.  Unfortunately,  these  tests 
at  times  fail  to  distinguish  between  added  stearin  and  natural  lards  in  them- 
selves containing  stearin  in  excessive  quantities.  Under  such  circumstances 
the  decision  as  to  the  presence  or  not  of  an  adulterant  becomes  a difficult  one. 

962.  Vegetable  Fats  and  Oils. — ^These  have  been  already  indicated, 
though  very  briefly,  in  the  table  given  at  an  earlier  stage  of  this  chapter. 
But  few  of  these  are  used  alone,  the  most  frequent  employment  of  the  oils 
being  in  conjunction  with  various  animal  fats.  Among  the  solid  vegetable 
fats  are  cacao-butter,  which  is  the  natural  fat  of  cocoa  or  chocolate. 

The  so-called  cocoa-nut  oil  is,  in  reality,  not  a liquid,  but  a solid,  and 
is  characterised  by  possessing  a somewhat  low  melting-point,  and  yet  being 
a rather  hard  fat.  In  its  natural  state  this  fat  is  said  to  readily  become  rancid  : 
the  thoroughly  purifled  forms  are  certainly  free  from  this  very  serious  defect. 
In  preparing  these  from  the  crude  cocoa-nut  fat,  the  fat  is  melted  in  a vacuum, 
and  then  a current  of  low  pressure  steam  forced  through.  This  latter  carries 
off  volatile  substances  of  objectionable  or  pronounced  odour  or  flavour,  and 
leaves  behind  a pure  and  comparatively  neutral  fat.  Like  the  lards,  these 
preparations  are  pure  fats,  and  contain  no  foreign  matter.  They  are  distin- 
guished from  other  fats,  both  vegetable  and  animal  (except  butter),  by  pos- 
sessing a rather  high  Reichert-Meissl  value. 

963.  Margarine. — ^In  1870,  the  French  chemist,  Mege-Mouries,  first 
described  a method  of  making  artificial  butter  on  the  large  scale.  Since 
then  his  methods. have  been  considerably  developed,  and  a large  industry 
has  grown  up  in  what  were  formerly  termed  artificial  butters,  butterine, 
oleo- margarine,  and  now  by  legal  enactment,  “ margarine.”  The  basis  of 
the  modern  methods  of  preparing  this  article  consists  in  first  rendering  fat 
of  the  ox  ; this,  after  melting,  is  drawn  off  from  solid  impurities,  and  allowed 
to  cool  very  slowly.  During  this  process  the  more  solid  portion  of  the  fat 
crystallises  out  as  stearin,  and  is  removed  by  filtration  under  pressure 
The  liquid  portion  solidifies  into  a granular  solid  of  a slightly  yellow  colour* 


CONFECTIONERS’  RAW  MATERIALS. 


869 


to  which  the  name  of  “ oleo  ” is  given.  Lard  is  also  prepared  in  some- 
what the  same  way,  and  to  this  the  name  of  “ neutral,”  or  neutral  lard,  is 
applied.  These  two  substances  constitute  the  basis  of  margarine.  The  oleo 
being  the  harder  fat  of  the  two,  is  taken  in  larger  quantity  for  margarine 
exposed  to  a warmer  climate.  The  mixed  oleo  and  neutral  are  next  agitated 
with  milk  or  cream,  or  possibly  butter  added,  and  thus  the  necessary  flavour 
introduced.  During  the  same  operation,  an  amount  of  butter  colour  is 
incorporated,  sufficient  to  produce  a tint  resembling  that  of  butter  itself. 
Different  manufacturers  use,  in  addition  to  these  ingredients,  various  vege- 
table oils,  in  order  to  soften  the  products,  and  thus  render  them  more  adopted 
to  general  purposes.  Arachis,  cotton-seed,  sesame  and  other  oils  are  thus 
employed.  When  properly  made,  there  can  be  no  doubt  as  to  the  whole- 
sonieness  and  nutritive  value  of  these  artificial  butters.  The  conditions  of 
manufacture  are  usually  hygienic,  the  materials  being  obtained  in  a fresh  state 
and  sterilised  before  use.  The  composition  of  margarine  is  shown  in  the 
last  three  analyses  quoted  in  the  table  of  butters  before  given.  The  fat 
value  is  generally  high,  while  a clear  line. of  distinction  between  these  sub- 
stances and  butter  is  afforded  by  the  low  Reichert-Meissl  and  high  butyro- 
refractometer  values.  The  former,  in  the  case  of  No.  24,  falls  below  I -0,  while 
in  the  admixtures  of  margarine  and  butter  the  figures  of  4-0  and  5-7  respec- 
tively were  obtained.  At  one  time  mixtures  were  offered  to  confectioners 
stated  to  contain  anything  up  to  40  per  cent,  of  butter  ; now,  by  law,  the 
proportion  of  butter  permitted  to  be  added  to  margarine  is  restricted  to 
10  per  cent. 

964.  Other  Compound  Fats. — Compound  lards  are  yet  another  form  of 
mixed  fats  ; these  are  sold  both  under  that  name  and  also  at  times  as  pure 
lards.  Their  basis  is  usually  beef  stearin,  or  whole  beef  fat,  mixed  with 
vegetable  oil,  generally  cotton-seed  oil.  With  these  more  or  less  lard  may 
also  be  incorporated.  As  lard  is  generally  checked  by  its  iodine  value, 
these  mixtures,  if  intended  as  fraudulent  lard  substitutes,  require  to  be  made 
so  that  their  iodine  value  is  the  same  as  pure  lard. 

One  of  the  most  interesting  bodies  of  this  type  is  a fat  put  on  the  market 
under  the  name  of  Veltex,  of  which  the  authors  have  had  special  oppor- 
tunities of  investigation.  No  claims  are  made  for  this  substance  that  it  is 
a substitute  for  animal  fats  ; but  on  the  contrary  it  stands  as  a competitor 
and  enters  the  field  as  a specially  prepared  fat  of  vegetable  origin.  The 
basis  of  this  fat  is  highly  refined  cotton-seed  oil,  which  is  grown,  manu- 
factured and  refined  in  the  southern  states  of  North  America,  from  which 
district  the  highest  grade  of  oil  is  obtained.  The  refining  process  is  that 
known  from  the  name  of  the  inventor  as  the  “Wesson”  process,  by 
which  probably  a purer  and  more  neutral  oil  is  produced  than  in  any  other 
manner.  There  are  several  grades  of  Wesson  oil,  the  highest  of  which 
alone  is  employed  in  Veltex  manufacture.  In  passing,  mention  may  be 
made  of  their  brand  of  “stearin-less  oil.”  Most  vegetable  oils  in  their 
natural  state  become  turbid  on  standing  in  the  cold,  as  a result  of  a deposit 
of  stearin,  but  with  the  stearin-less  oil,  immersion  in  melting  ice  for  5 hours 
still  leaves  the  oil  perfectly  clear.  Beyond  the  Wesson  oil,  the  chief 
constituent  of  Veltex  is  refined  beef  stearin,  which  is  used  in  order  to  give 
the  requisite  buttery  consistency  to  the  product. 

This  fat  is  manufactured  in  Liverpool  in  a modern  and  perfectly 
equipped  factory,  established  there  in  1910.  It  is  a great  advantage  with 
fats  that  they  should  be  in  the  consumer’s  hands  with  the  least  possible 
delay  after  manufacture.  This  factory  is  fortunately  situated,  ‘and  its 
products  can  therefore  be  distributed  in  an  absolutely,  fresh  state  within  a 
very  few  hours  to  any  part  of  the  United  Kingdom. 


870 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


The  authors  have  had  an  opportunity  of  inspecting  the  process  of 
manufacture,  which  has  been  so  organised  as  to  involve  the  least  possible 
handling  at  the  producer’s  factory.  The  oil  arrives  in  casks,  the  contents 
of  which  are  discharged  into  convenient  reservoirs  and  then  pumped  to 
the  top  of  the  building.  Here  the  process  of  manufacture  begins.  The 
solid  constituents  are  first  melted,  the  greatest  care  being  taken  to  keep  the 
temperature  at  the  lowest  possible  point.  The  melted  ingredients  are  then 
added  together  in  the  requisite  proportions  in  a large  vessel  and  thoroughly 
mixed  by  the  injection  of  air.  The  liquid  fat  next  descends  to  the  cooling 
room,  where  it  is  rapidly  converted  into  the  solid  state  by  means  of  specially 
designed  machines.  On  leaving  these  the  fat  has  practically  set,  but  is 
still  sufficiently  ductile  to  permit  of  its  being  forced  through  pipes  to  the 
automatic  weighing  machine,  where  it  is  weighed  off  direct  into  barrels  or 
other  convenient  packages  for  dispatch  to  the  consumer. 

In  physical  character,  the  fat  as  thus  obtained  is  of  buttery  consistency, 
has  a fair  body,  and  a slightly  yellow  tint,  due  to  the  natural  colour  of 
the  oil  only.  Perhaps  the  distinguishing  feature  of  Veltex  is  its  neutral 
character,  and  freedom  from  any  very  pronounced  flavour.  The  taste  is 
but  slight,  and  is  very  pleasant.  The  following  are  the  iodine  values 
of  the  chief  ingredients,  and  the  finished  fat  : — - 


Wesson  Cotton-seed  Oil  . . . . 103-90  Iodine  value 

Stearin  . . . . . . . . . . 23-20  ,,  ,, 

Veltex  . . . . . . . . . . 91-73  ,,  ,, 

The  figures  obtained  on  analysis  were  : — 

Water 

0-00 

Ash  

0-00 

Eat 

..  100-00 

100-00 

It  is  therefore  a fat  which  is  all  fat. 

In  use  Veltex  may  be  employed  alone,  when  it  produces  cakes,  which 
work  well  during  the  process  of  manufacture,  are  of  rich  nature,  and  pleas- 
ant flavour.  Cakes  so  made  were  devoid  of  any  after-flavour,  such  as  low 
grades  of  fat  are  peculiarly  apt  to  produce.  One  special  precaution  is  neces- 
sary in  working  with  this  fat,  and  that  is  to  add  a minute  quantity  of  salt. 
This  substance  is  always  present  in  considerable  quantity  in  butters,  and 
so  as  a flavour  developing  agent  a small  quantity  of  salt  is  necessary. 

When  the  butter  character  is  wished,  this  fat  may  be  used  in  any  desired 
proportion  with  butter,  with  which  it  works  well.  To  the  confectioner 
it  is  of  importance  that  his  fat  behave  properly  during  the  somewhat  critical 
operation  of  cake-mixing.  This  particular  article  may  be  successfully  used 
in  cakes  made  either  by  what  is  known  as  the  sugar  batter  process,  or  the 
flour  batter  process. 

965.  Mineral  Fats.” — ^It  is  not  too  much  to  say  that  both  the  animal 
and  vegetable  kingdoms  have  been  thoroughly  exploited  in  order  to  find 
fats  for  the  confectioner.  One  may  go  a step  further,  and  say  that  the 
mineral  kingdom  has  also  been  laid  under  contribution.  There  is  a class  of 
bodies  known  as  paraffins,  the  higher  members  of  which  are,  when  pure, 
white,  solid,  tasteless  waxes.  Then  next,  another  substance  has  been  pre- 
pared, knowTL  sometimes  as  soft  paraffin,  and  also  as  vaseline.  This  latter, 
which  is  also  tasteless  and  odourless,  has  a soft  and  semi-buttery  consis- 
tency. Its  physical  nature  is  very  like  that  of  the  fats  generally,  but  it 
differs  in  that  it  is  unattacked,  even  by  strong  alkalies,  and  so  cannot  be 
converted  into  soap.  It  is  therefore  matter  for  little  surprise  that  vaseline, 
paraffin,  and  petroleum  products  generally,  are  entirely  unassimilable  by 


CONFECTIONERS’  RAW  MATERIALS. 


871 


the  human  digestive  system,  and  consequently  absolutely  devoid  of  nutri- 
tive value.  When  a person  buys  a cake,  these  mineral  bodies  are  certainly 
not  of  the  nature,  substance  and  quality  of  the  article  demanded  by  such 
purchaser.  While  as  food  these  substances  are  perfectly  valueless,  the 
authors  are  not  aware  of  their  possessing  any  positively  harmful  qualities. 
It  would  seem  probable  that,  according  to  the  extent  to  which  flour  and 
other  bodies  were  saturated  with  paraffin,  they  would  thus  be  protected 
from  digestive  action  within  the  alimentary  tract,  and  thus  they  would  be 
rendered  more  difficult  of  digestion  and  of  less  food  value. 

Sweetening  Ingredients. 

966.  Sugars. — ^The  principal  sweetening  agents  of  the  confectioner 
belong  to  a group  of  substances  knovTi  as  sugars,  of  which  bodies  an  extended 
description  has  already  been  given  in  Chapter  VI.  The  following  are  the 
most  important  of  the  various  substances,  containing  one  or  more  of  the 
sugars,  that  are  of  service  in  confectionery. 

967.  Honey. — Among  bodies  which  are  naturally  sweet,  perhaps  that 
best  knowm  is  honey.  Since  this  substance  is  collected  and  stored  by  bees, 
man,  in  even  a most  primitive  state,  was  familiar  with  honey,  and  valued  it 
because  of  its  sweetness.  It  would  seem  that  honey  was  once  the  staple 
sweetening  agent  of  many  peoples,  being  used  for  that  purpose  in  this  coun- 
try, and  also  as  a source  of  those  beverages  which  require  a sugar  as  their 
basis.  Although  collected  by  the  bee,  honey  is  naturally  a vegetable  pro- 
duct, and  is  obtained  from  flowers.  Honey  not  only  possesses  sweetness, 
but  also  distinct  and  various  flavours,  due  to  certain  odoriferous  and  flavour- 
ing matters  present  in  the  flowers  from  which  it  is  derived.  This  natural 
form  of  sugar  is  still  used  by  the  confectioner,  and  is  one  of  the  principal 
ingredients  in  the  sweet  basis  of  nougat. 

In  composition,  according  to  Allen,  honey  is  a concentrated  solution  of 
glucose  (dextrose)  and  fructose  (laevulose)  in  water.  At  times  there  is 
also  present  a small  quantity  of  sucrose.  In  addition,  honey  contains  small 
quantities  of  wax,  pollen,  mineral  matter,  and  traces  of  flavouring  and  bitter 
substances,  and  formic  acid.  The  following  are  the  results  of  analysis  of  a 
number  of  samples  of  honey  by  various  observers  : — 


Glucose  (Dextrose)  . . 

22-2  to 

44-7  per  cent. 

Fructose  (Laevulose) 

321  „ 

46-9  „ 

Total  Glucose  and  Fructose 

61-4  „ 

82-5 

Wax,  Pollen,  and  Insoluble  Matters . . 

trace  ,, 

21 

Ash 

0 02  „ 

0-49  „ 

Water  expelled  at  100°  C. 

12-4  „ 

24-9  „ 

Undetermined  Matters 

1-3  „ 

10-8  „ 

In  the  great  majority  of  samples,  the  total  glucose  and  fructose  range 
from  70  to  80  per  cent.,  the  water  from  17  to  20,  and  the  ash  from  OTO  to 
0-25  per  cent.  Among  adulterants  of  honey  are  found  glucose  syrup  (con- 
fectioner’s glucose),  cane  sugar,  invert  sugar,  and  molasses  (golden  syrup). 
Dextrin  is  not  found  in  genuine  honey. 

968.  Cane  Sugar,  Sucrose. — The  earlier  names  given  to  the  sugars  were 
derived  from  the  source  of  each  particular  sugar  ; but  it  is  now  well  known 
that  one  and  the  same  variety  of  sugar  may  be  obtained  from  a number  of 
substances.  When,  therefore,  a sugar  is  named  cane  sugar,  the  name  indicates 
not  necessarily  that  the  sugar  in  question  is  derived  from  the  sugar-cane, 
but  that  it  is  sugar  of  precisely  the  same  kind  as  that  originally  derived 
from  that  souree.  Cane  sugar  occurs  not  only  in  the  juice  of  the  sugar-cane, 
but  also  in  certain  roots,  especially  tliat  of  the  beet,  and  in  the  sap  of  some 


872 


THE  TECHNOLOGY  OE  BHEAD-MAKING. 


trees,  of  which  maple  sugar  is  a familiar  example.  Various  seeds,  such  as 
the  almond,  barley,  and  also  fruits  contain  cane  sugar.  The  process  of 
manufacture  consists  first  in  expressing  the  juice  whether  of  the  cane  or  the 
beet,  heating  to  boiling  point,  and  then  getting  rid  of  various  impurities  by 
the  addition  of  lime.  To  get  rid  of  the  colour,  the  solution  of  sugar  is  filtered 
through  animal  charcoal,  after  which  the  S3rrup  is  evaporated  in  steam-heated 
pans  and  finally  in  vacuo.  Crops  of  crystals  of  sugar  are  thus  obtained, 
leaving  behind  a residuum  of  syrup  known  as  molasses. 

The  types  of  sugar  used  by  the  confectioner,  such  as  sugar  crystals, 
castor  sugar,  and  pulverised  sugar,  are  almost  chemically  pure.  Moist 
sugar,  or  “pieces,”  contains  water  in  varying  quantities  up  to  about  8 per 
cent.  Various  commercial  sugars  have  the  following  percentage  com- 
position : — 


Composition  of  Various  Sugars. 


Constituents. 

Raw  Cane 
Sugar. 

Raw  Beet 
Sugar. 

Refined  Sugar, 
Cane  or  Beet. 

Sucrose 

87  to  99 

89  to  96 

9M  to  99-9 

Glucose  and  Fructose  . . 

2 „ 9 

trace  ,,  0*3 

none  ,,  trace 

Ash  

0-2  „ 2-3 

1-6  „ 2-6 

trace  ,,  0*15 

Water 

04  „ 6*8 

2-0  „ 4-3 

trace  ,,  0*25 

Organic  Matter  not  Sugar 

0-3  „ 9*7 

04  „ 4-0 

none 

So  long  as  sugars  are  imperfectly  refined,  and  not  absolutely  freed  from 
the  residual  S3n’up,  beet  sugar  is  inferior  in  quality  to  that  of  the  cane.  But 
by  modern  processes,  the  sugar  is  obtained  in  what  is  essentially  a chemically 
pure  state ; and  in  this  condition  sucrose,  whether  derived  from  the  cane  or 
the  beet,  is  identical  in  character,  and  samples  obtained  from  the  two  sources 
are  undistinguishable  from  each  other. 

Refined  sugars  are  now  almost  invariably  “ blued  ” in  order  to  correct 
any  slight  yellowish  tint.  Minute  traces  of  ultramarine,  or  other  blue,  are 
added  for  this  purpose.  Such  an  addition  is  usually  regarded  as  harmless. 

969.  Molasses,  Treacle,  or  Golden  Syrup. — ^The  residual  juice  of  the 
sugar-cane,  before  referred  to,  forms  when  concentrated  a pleasant  smelling 
and  tasting  syrup  ; therefore  the  molasses  from  cane  sugar  is  agreeable  to 
the  taste.  The  concentrated  beet  juice  contains,  however,  substances 
which  are  not  pleasant  in  odour  or  taste,  and  therefore  beet  sugar  molasses 


Composition  of  Golden  Syrup  and  Treacle. 


Constituents. 

Golden 

Syrup. 

Treacle. 

Golden 

Syrup. 

Treacle. 

Cane  Sugar.  . 

3440 

32-55 

39-6 

32-5 

Glucose  and  Fructose 

46-35 

42-85 

33-0 

37-2 

Water 

18-50 

15-20 

22-7 

234 

1 Mineral  Matter  . . . . . . \ 

0-75 

9-40 

/ 2-5 

3-5 

Other  Organic  Matter  . . . . j 

t 2-8 

3-5 

100-00 

100-00 

100-6 

100-1 

CONFECTIONERS’  RAW  MATERIALS. 


873 


is  not  acceptable  for  food  purposes.  On  the  preceding  page  are  given 
analyses  of  golden  syrup  and  treacle,  Nos.  1 and  2,  by  one  of  the  authors, 
and  3 and  4 by  Wallace. 

970.  Inversion  of  Cane  Sugar. — ^The  chemical  changes  involved  in  the 
inversion  of  cane  sugar  were  explained  in  Chapter  VIII.,  paragraph  276. 
As  there  stated,  they  result  in  the  formation  from  one  molecule  of  sucrose  of 
a molecule  each  of  glucose  (dextrose)  and  fructose  (Isevulose).  The  follow- 
ing deals  with  the  bearing  of  cane  sugar  inversion  on  certain  processes  of  the 
confectioner.  It  may  be  of  interest  to  mention  that  dextrose  is  found 
largely  in  the  juice  of  grapes.  When  dried  into  raisins,  these  on  becoming  old 
develop  gritty  masses  in  their  interior.  These  little  lumps  are  aggregates 
of  small  crystals  of  dextrose,  which  at  times  is  called  grape  sugar.  The  Isevu- 
lose,  so-called  from  its  left-handed  rotation,  is  now  frequently  termed  fruc- 
tose or  fruit  sugar,  and  crystallises  only  with  great  difficulty  ; hence  its 
presence  acts  as  a preventative  of  crystallisation.  If  a saturated  cold  solu- 
tion of  cane  sugar  be  divided  into  two  equal  parts,  and  the  one  inverted  by 
treatment  with  hydrochloric  acid,  the  two  may  be  placed  away  together 
for  purposes  of  observation.  Even  though  the  unaltered  sucrose  have  water 
added  to  it  in  the  same  volume  as  hydrochloric  acid  was  added  to  the  other 
moiety,  yet  as  time  proceeds  the  cane  sugar  crystallises  rapidly.  In  such 
solutions  thus  made  and  set  aside  by  the  authors,  the  cane  sugar  had  at  the 
end  of  some  three  weeks  become  almost  solid,  while  not  a single  crystal 
had  developed  in  the  solution  of  invert  sugar.  Not  only  is  invert  sugar  itseK 
singularly  free  from  a tendency  to  crystallise,  but  its  presence  tends  also  to 
prevent  crystallisation  of  cane  sugar  present  in  the  same  solution.  Striking 
illustrations  of  this  occur  in  the  boiling  of  jams,  where  a solution  of  sugar 
is  heated  with  fruit  containing  organic  acids.  In  a sample  of  raspberry 
jam  made  in  the  authors’  laboratory  from  cane  sugar  and  fruit  only,  it  was 
found,  after  keeping,  that  some  50  per  cent,  of  the  sugar  had  undergone 
inversion.  As  already  mentioned,  cane  sugar,  on  heating,  is  changed  into 
an  amorphous  variety  ; and  hence  the  “ glassy  ” type  of  sugar  in  such 
sweets  as  barley  sugar.  Still  in  these  there  is  the  tendency  to  crystallise, 
and  such  sweets  would  become  opaque  on  being  kept.  To  prevent  this, 
acid  is  added  during  the  boiling,  and  by  the  inversion  of  part  at  least  of 
the  sugar  completely  prevents,  or  very  considerably  retards,  the  process  of 
crystallisation.  Whenever  sugar  is  inverted  by  acid  during  a process  of 
sugar  working,  or  invert  sugar  is  introduced  in  a mixture,  then  the  general 
effect  is  to  retard  or  prevent  crystallisation.  Although  invert  sugar  or 
glucose  is  thus  almost  continually  being  formed  from  many  sugar-working 
processes,  yet  it  is  rarely  if  ever  added  or  employed  as  a previously 
prepared  product  by  the  confectioner. 

971.  Comparative  Sweetness  of  Cane  and  Invert  Sugar. — ^When  unripe 
fruit  is  used  in  the  manufacture  of  pies  and  puddings,  they  are  too  sour  to 
eat  without  the  addition  of  sugar.  Sugar  may  be  added,  and  cooked  with 
the  fruit,  or  else  subsequently  at  the  moment  of  eating.  Various  opinions 
have  been  expressed  as  to  the  respective  advantages  of  these  two  methods. 
When  added  previous  to  cooking,  more  or  less  of  the  sugar  is  inverted  by 
the  acids  present,  and  the  degree  of  sweetening  action  of  the  added  sugar 
must  evidently  depend  on  the  comparative  sweetness  of  cane  sugar,  and 
the  invert  sugar  produced  therefrom.  In  order  to  throw  light  on  this  point, 
one  of  the  authors  made  an  experiment,  in  which  a solution  of  cane  sugar 
was  divided  into  two  equal  parts,  and  the  one  moiety  carefully  inverted 
and  neutralised,  after  which  both  were  made  up  to  the  same  volume.  On 
being  compared  for  taste  by  half-a-dozen  persons,  the  general  verdict  was 
that,  for  initial  taste,  the  cane  sugar  was,  if  anything,  the  sweeter.  On 
the  other  hand,  the  sweetness  of  the  invert  sugar  was  much  more  persistent 


874 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


and  lasting  on  the  palate.  Owing  to  this  latter  property,  the  invert  sugar 
was,  in  its  total  effect,  considered  the  sweeter  of  the  two.  In  the  next  place, 
an  attempt  was  made  to  decide  which  had  the  greater  ‘‘  covering  power  ” 
for  acids,  and  for  this  purpose  each  solution  was  acidulated  with  an  equal 
quantity  of  dilute  sulphuric  acid,  and  again  tasted.  The  acid  flavour  is 
very  rapid  in  its  effect  on  the  palate  ; and  consequently,  the  cane  sugar 
which  seemed  to  act  on  the  palate  with  almost  equal  speed,  mingled  its 
sweetness  with  the  taste  of  the  acid,  and  so  produced  a homogeneous  fla- 
vour. When  the  invert  sugar  was  tried,  the  first  sensation  was  one  of 
overwhelming  sourness,  followed  by  the  gradually  accumulating  sweetness 
of  the  slower  but  more  lasting  taste  of  sugar  after  inversion.  The  more  prefer- 
able method  of  sweetening  the  fruit  of  pies  and  puddings  would  therefore 
seem  to  be  that  of  adding  the  sugar  subsequent  to  the  cooking.  But  if  the 
full  advantage  of  the  Sugar  thus  added  is  to  be  derived,  the  sugar  should  be 
in  a finely  divided  state,  and  allowed  to  dissolve  in  the  juice  of  the  fruit 
before  being  eaten.  It  is  probable  that  the  apparently  greater  sweetness 
of  previously  added  sugar  may  be  due  to  its  having  been  thoroughly  dissolved, 
as  against  the  addition  of  large  crystals  of  sugar  after  cooking,  and  their 
deglutition  without  solution.  The  question  discussed  throws  an  interesting 
side-light  on  problems  of  flavour  generally.  Much  may  be  due  to  the  selec- 
tion of  flavours  which,  when  realised  by  the  palate  at  the  same  time,  shall 
conjointly  produce  a favourable  impression  ; or  if  appreciated  in  succession, 
shall  give  a sequence  of  effects  which  is  in  itself  pleasant.  That  the  distinc- 
tion is  a real  one,  is  evinced  by  the  frequent  discrimination  of  flavours  into 
“ taste  ” and  “ after-taste.” 

972.  Sugar  Boiling. — ^If  the  temperature  of  sugar  be  maintained  for 
some  time  just  a little  above  the  melting  point,  the  sugar  is  changed  without 
loss  of  weight  into  a mixture  of  dextrose,  and  a substance  called  laevulosan, 
thus  : — 

C12H22O11  = C6H12O6  CeHioOs. 

Sucrose.  Dextrose.  Laevulosan. 

Further  application  of  heat  causes  water  to  be  given  off,  with  the  pro- 
bable conversion  of  the  dextrose  into  glucosan,  thus  : — 

CeR,,Oe  = CeHioOs  + H2O. 

Dextrose.  Glucosan.  Water. 

At  a yet  higher  temperature  further  decomposition  ensues,  both  laevu- 
losan  and  glucosan  being  converted  into  caramelan,  C12H18O9,  thus  : — 

2C6H10O5  = C12H18O9  -|-  H2O. 

Glucosan  and  Caramelan.  Water. 

Lsevulosan 

Caramelan  w'hen  pure  is  colourless,  has  a slightly  bitter  taste,  and  is  highly 
deliquescent. 

Further  elevation  of  temperature  to  from  374°  F.  (190°  C.)  to  410°  F. 
(210°  C.)  results  in  the  formation  of  so-called  caramel,  which  is  a mixture 
of  dark-brown  bodies,  more  or  less  soluble  in  w^ater  and  alcohol. 

This  statement  of  the  chemical  changes  occurring  when  sugar  is  sub- 
jected to  the  action  of  heat  will  serve  as  a prelude  to  a description  of  what  is 
called  “ sugar  boiling  ” by  the  confectioner.  This  process  is  usually  con- 
ducted in  deep  round  copper  pans,  the  size  of  which  will  naturally  depend 
on  the  extent  of  the  contemplated  operations.  These  pans  may  be  heated 
either  by  gas  or  direct  fire  heat.  It  is  well  to  have  an  ample  margin  of 
sufficiency  of  heat,  since  rapid  heating  to  a given  point  will  produce  results 
which  differ  from  slowly  raising  the  temperature  to  the  same  degree.  The 
confectioner  places  in  his  pan  say  7 lbs.  of  white  cube  sugar  or  crystallised 
sugar,  and  one  quart  of  water.  This  is  set  on  the  fire  and  the  contents  raised 
to  the  boiling  point  : directly  this  occurs,  the  liquid  is  carefully  stirred 


COKFECTIONERS’  RAW  MATERIALS. 


875 


with  a spatula,  so  as  to  dissolve  any  lumps  of  sugar  which  may  happen  to 
remain.  At  this  stage  the  mixture  is  a solution  of  sugar  in  very  hot  water. 
On  continuing  the  boiling  a little  longer,  the  temperature  of  the  solution 
rises,  and  if  taken  by  a thermometer,  will  be  found  to  be  at  from  215  to 
220°  F.  Each  particular  stage  of  temperature  corresponds  to  a certain 
degree  of  sugar  boiling,  to  which  a technical  name  is  given.  Thus  at  the 
temperature  of  215  to  220°,  the  degree  of  smooth  is  reached.  The  workman 
identifies  these  degrees  by  physical  tests  which  he  applies  to  the  sugar 
Thus  he  dips  a clay  pipe  stem  into  the  liquid,  and  draws  it  between  the 
finger  and  thumb  ; at  the  smooth  degree  the  sugar  feels  oily,  and  hence  the 
name  of  the  degree.  Proceeding  still  further  with  the  heating,  a tempera- 
ture of  230  to  235°  is  reached,  and  now  the  sugar  is  at  the  thread  degree. 
During  this  time  water  has  been  driven  off  from  the  sugar,  and  now  on 
cooling,  the  solution  is  sufficiently  viscous  to  draw  into  threads,  if  a little  is 
pulled  out  between  the  finger  and  thumb.  With  further  heating,  a tempera- 
ture of  240  to  245°  is  reached,  and  the  sugar  is  in  the  Uow  or  feather  degree. 
At  this  stage  the  liquid  has  become  so  viscous  that  the  steam  generated  in 
boihng  blows  the  mass  into  huge  bubbles,  and  in  fact,  may  easily  boil  over 
the  pan.  If  a little  of  the  sugar  be  tossed  in  the  air,  it  will  exhibit  a fea- 
thered appearance.  At  250  to  255°,  we  reached  the  hall  or  pearl  degree,  and 
a little  of  the  sugar  taken  on  a pipe  stem  or  glass  rod  and  dipped  into  water 
acquires  a consistency  about  equal  to  that  of  putty.  We  now  proceed  to 
carry  our  heating  operation  a considerable  distance  further,  and  when  the 
thermometer  registers  from  310°  to  316°,  the  sugar  is  at  the  crack  degree. 
If  now  cooled  in  water,  the  sugar  rapidly  hardens  and  becomes  brittle.  Very 
little  further  heating  causes  an  incipient  caramelising,  and  the  confectioner’s 
caramel  degree  is  reached. 

During  these  stages  the  water  originally  added  is  being  driven  off  ; 
while  toward  the  last  the  sugar  is  undergoing  those  successive  steps  of  degra- 
dation towards  caramelan,  by  “ shedding  ” or  losing  molecule  after  mole- 
cule of  water.  It  will  be  noticed  that  throughout,  the  sugar  still  retains  the 
chemical  composition  of  a carbohydrate. 

973.  Cutting  the  Grain. — ^At  this  stage  an  explanation  must  be  given  of 
what  the  confectioner  terms  “ cutting  the  grain  ” of  sugar.  When  heated 
above  250°  E.  the  sugar  will,  if  allow'ed  to  cool,  crystallise  into  a hard  granular 
mass.  The  sugar,  in  fact,  re-solidifies  from  fusion  and  crystallises  in  so 
•doing.  To  “ cut  ” or  destroy  this  graining  tendency,  the  confectioner 
employs  some  acid  substance,  that  most  frequently  used  being  cream  of 
tartar,  wffiich  is  the  acid  tartrate  of  potash  (hydrogen  potassium  tartrate). 
Instead  of  this,  tartaric,  citric,  or  acetic  acids  may  be  employed.  The 
cutting  agent  may  be  added  to  the  sugar  when  first  mixed  with  w'ater,  and 
the  whole  heated  together.  Sugar  thus  treated,  instead  of  graining,  remains 
pliable  while  hot,  and  transparent  when  cold.  The  sugar  has  in  fact  lost 
its  crystalline  nature,  and  has  become  an  amorphous  or  vitreous  substance. 
From  w'hat  has  been  previously  explained,  it  will  at  once  be  seen  that  cutting 
the  grain  consists  of  inverting  more  or  less  of  the  sugar  by  means  of  an  acid 
body. 

974.  Fondant  Sugar. — ^This  preparation  is  used  both  in  flour  and  sugar 
confectionery.  Sugar,  w^ater,  and  cream  of  tartar  are  first  boiled  to  the 
feather  degree.  Then,  in  hand-w'orking,  the  syrup  is  stirred  until  it  becomes 
creamy  through  the  production  of  minute  crystals.  On  the  large  scale  the 
same  effect  is  obtained  by  pouring  the  requisitely  boiled  syrup  into  a vessel 
in  which,  during  cooling,  it  is  violently  agitated  by  paddles  or  stirrers  ; 
crystallisation  goes  on,  and  the  creamy  mass  of  fine  crystals,  suspended  in 
S3T?up,  pours  out  from  the  low  er  end  of  the  vessel.  The  crystalline  portion 


876 


THE  TECHNOLOGY  OE  BHEAH-MAKING. 


of  the  fondant  is  simply  unaltered  cane  sugar  crystals,  the  softer  and  non- 
erystalline  portion  consists  of  invert  sugar. 

975.  Starch-Sugar,  “ Glucose.” — -By  processes  already  explained 
(paragraph  632)  malt  is  converted  into  the  preparation  known  as  malt 
extract.  Starch  forms  a much  cheaper  source  of  malt  sugar  or  maltose, 
and  may  he  changed  into  a mixture  of  maltose  and  dextrin  by  the  action  of 
diastase,  or  more  conveniently  by  hydrolysis  of  dilute  acid.  But  while 
diastase  is  incapable  of  carrying  hydrolysis  further  than  maltose,  acids  pro- 
duce by  further  conversion  more  or  less  glucose.  Starch  sugar  finds  many 
uses,  and  consequently  its  production  is  an  important  branch  of  manufac- 
ture. Maize  starch  is  that  most  commonly  employed.  The  starch,  water, 
and  a small  quantity  of  sulphuric  acid,  are  heated  together  in  large  wooden 
vats  by  the  introduction  of  steam.  This  operation  is  continued  until  a 
small  portion  of  the  liquid  ceases  to  give  the  starch  reaction  with  iodine. 
Chalk  (calcium  carbonate)  is  next  added  in  slight  excess,  so  as  to  neutralise 
the  acid.  The  calcium  sulphate  is  allowed  to  settle,  and  the  upper  liquid 
decolourised  by  filtration  through  animal  charcoal,  and  concentrated  by 
evaporation  until  the  solution,  when  cold,  has  a specific  gravity  of  about 
1’3  to  1-4.  Starch  sugar  thus  obtained  is  a colourless,  odourless,  and  trans- 
parent syrup,  possessing  a pleasant,  sweet  taste. 

976.  Analysis  of  ‘‘  Glucose.” — ^The  following  are  analyses  of  malt 
extracts,  for  purposes  of  comparison,  and  commercial  starch  sugars  : — 


Analyses  of  Malt  Extract  and  ‘"Glucose.” 


Constituents. 

Malt 
Extract. 
No.  I. 

Malt 
Extract. 
No.  II. 

starch 
Sugar. 
No.  I. 

starch 
Sugar. 
No.  IIA. 

starch 
Sugar. 
No.  IIB. 

starch 

Sugar. 

No.  lie. 

Water 

22-23 

26-30 

18-24 

15-20 

15-20 

15-20 

Mineral  Matter 

MO 

1-60 

0-26 

0-18 

0-18 

0-18 

Proteins 

3-01 

5-40 

— • 

— • 

— ■ 

— • 

Dextrin 

12-90 

7-65 

16-00 

16-20 

16-20 

21-38 

Sucrose 

3-59 

4-07 

— • 

— • 

— • 

— • 

Maltose 

Dextrose  and  Lsevulose 

54-84 

47-01 

55-50 

59-00 

60-92 

48-98 

(Glucose)  . . 

2-33 

7-97 

10-00 

9-42 

7-50 

14-26 

1 

100-00 

100-00 

100-00 

100-00 

100-00 

100-00 

The  starch  sugar,  being  made  from  the  purified  starch  only,  contains 
none  of  the  ready-formed  sugars  of  the  grain,  nor  any  proteins,  such  as  are 
found  in  malt  extract.  The  mineral  matter  consists  of  a trace  of  calcium 
sulphate  held  in  solution  in  the  S3n’up.  The  essential  constituents  of  starch 
sugar  are  dextrin  and  maltose,  which  in  the  figures  given, in  the  first  analysis, 
together  form  about  87  per  cent,  of  the  total  solid  matters  present.  The 
remainder  is  composed  almost  entirely  of  dextrin.  Starch  sugar  has  a 
remarkably  high  right-handed  rotary  power  on  polarised  light,  the -figure 
for  the  first  sample  quoted  being  2*75°  per  gram  of  solids  in  100  cubic  centi- 
metres of  the  solution  when  measured  in  a two -decimetre  tube. 

It  will  be  seen,  therefore,  that  starch  sugar  has  about  double  the  right- 
handed  rotary  powder  of  cane  sugar,  w4iich  high  figure  absolutely  differen- 
tiates it  from  invert  sugar  or  glucose,  with  its  left-handed  rotary  power. 
In  the  analysis  quoted  the  high  rotary  power  indicates  that  the  proportion 
of  glucose  present  (if  any)  must  consist  practically  entirely  of  dextrose,  or 
tlie  right-handed  variety  of  glucose. 


CONFECTIONERS^  RAW  MATERIALS. 


877 


In  view  of  the  fact  that  the  composition  of  starch  sugar  as  stated  by  the 
authors  differs  materially  from  that  commonly  accepted,  the  following 
details  of  analysis  are  given,  being  those  of  sample  No.  II.  : — 

Density  of  20  per  cent,  solution  . . 

Rotar}^  power  of  20  per  cent,  solution  in  200  millimetre  tube 
Rotary  power  per  gram  of  solids  in  100  c.c.,  measured  in  200  m.m 
tube 

Specific  rotary  power  of  whole  substance.  . 

,,  ,,  ,,  organic  solids  of  substance 

Cupric  oxide  reducing  power  of  whole  substance  determined 
gravimetrically,  calculating  all  reducing  sugars  as  glucose,  (K) 

All  reducing  sugars  as  maltose 
Water — 

From  solution  density  . . . . . . . . . . 15*5 


1065-1 

47-216° 

2-78° 

118-04° 

139-0° 

Per  cent. 

44-62 

71-35 


14-9 


84- 5 

85- 1 


By  evaporaticn 

Mean 

Solids — 

From  solution  density  . 

By  evaporation  . . 

Mean 

Ash  by  ignition 

Organic  solids.  . . . . . . . . . . . 84-8  — 0-18 

Dextrin  by  direct  precipitation  with  alcohol,  10  c.c.  of  10  per 
cent,  solution,  added  to  250  c.c.  of  93  per  cent,  alcohol,  pre- 
cipitated, washed  and  weighed  ; quantity  per  cent. 

As  a check  on  the  dextrin  determination,  a control  experiment  was  made 
in  Avhich  0-2  gram  of  pure  dextrin  was  precipitated  in  the  same  manner. 


15-2 


84-8 

0-18 

84-62 


16-20 


There  was  recovered  as  precipitate 

,,  ,,  by  evaporation  of  filtrate 


Grams. 

0-1890 

0-0105 


0-1995 

In  making  the  determination  on  starch  sugar  the  correction  for  solu- 
bility was  added. 

In  column  No.  II a.  of  preceding  table,  the  maltose  and  dextrose  are 
calculated  from  the  opticity  thus  : — ■ 

Taking  the  20  per  cent,  solution,  it  contains,  in  grams,  per  100  c.c. 
Dextrin  . . . . . . . . . . . . . . 3-24 

Sugars  . . . . . . . . . . . . . . 13-72 


Organic  solids  . . . . . . . . . . . . 16-96 

The  rotation  due  to  dextrin  is 

3-24  X 3-86  = 12-506° 

The  rotation  due  to  sugars  is 

47-216  - 12-506  = 34-71°. 

If  all  the  sugar  present  consist  of  maltose,  then  opticity,  13-72  X 2-78  = 38-08° 
If  all  the  sugar  present  consist  of  dextrose,  then  opticity,  13-72  X 1-04  = 14-24° 
Difference  . . . . . . . . . . . . . . 23-84° 

The  observed  rotary  power,  34-71°,  lies  between  the  two,  and  therefore 
the  sugars  are  a mixture  of  maltose  and  dextrose,  from  which  the  respective 
percentages  are  calculated  as  follows  : — 


(34-71  - 14.24)  X 13-72 
23-84 


= 11-8  grams 


of  maltose,  per  100  c.c.  of  20  per  cent,  solution.  Then  13-7  — 11-8  = l-O 
of  dextrose. 


878  THE  TECHNOLOGY  OF  BREAD-MAKING. 


These  numbers  multiplied  by  5 give  the  percentages  quoted  in  the 
table— 

11*8  X 5 = 59-0  per  cent,  of  maltose. 

1*9  X 5 = 9-5  ,,  ,,  dextrose. 

In  column  No.  IIb.  of  the  table,  the  maltose  and  dextrose  are  calculated 
from  the  cupric  oxide  reducing  power. 

The  difference  between  the  percentage  of  organic  solids  and  precipitated 
dextrin  being  regarded  as  sugars  we  thus  have — 


84-62  — 16-20  = 68-42  per  cent. 

As  the  reducing  sugars  calculated  as  maltose  and  as  dextrose  amount 
to  71*35  and  44-62  per  cent,  respectively,  the  figure  68-42  lies  between  these, 
and  the  sugars  must  consist  of  a mixture  of  maltose  and  dextrose.  From 
these  figures  the  percentages  of  each  may  be  calculated — 

(68-42  - 44-62)  X 68-42 


71-35  - 44-62 


= 60-92  per  cent. 


of  maltose,  and  68-42  — 60-92  = 7-5  per  cent,  of  dextrose,  which  are  the 
figures  given  in  the  table. 

It  will  be  observed  that  the  percentages  of  maltose  and  dextrose,  calcu- 
lated from  opticity,  agree  substantially  with  those  calculated  from  cupric 
reducing  power. 

In  Alienas  Commercial  Organic  Analysis,  the  author  suggests  a method 
of  calculating  percentages  of  dextrin,  maltose,  and  dextrose  from  the  organic 
solids,  specific  rotary  power,  and  cupric  reducing  power.  In  column  No. 
He.,  the  composition  of  the  sample  is  calculated  from  this  formula  and  the 
data  already  given.  It  will  be  observed  that  the  dextrin  and  dextrose 
are  much  higher  than  when  the  dextrin  is  directly  determined  and  the  other 
constituents  calculated  from  either  the  opticity  or  cupric  reducing  power. 

From  particulars  before  given,  it  will  be  seen  that  determination  by 
precipitation  accounts  for  practically  the  whole  of  the  dextrin.  It  was 
thought  well,  however,  to  investigate  the  nature  of  this  precipitate  rather 
more  closely.  On  being  re-dissolved,  it  was  found  to  give  a considerable 
amount  of  precipitate  with  Fehling’s  solution.  A larger  quantity  was  there- 
fore prepared  in  the  following  manner.  From  50  to  60  grams  of  the  starch 
sugar  No.  II.  was  dissolved  in  about  100  c.c.  of  water,  and  added  to  about 
1250  c.c.  of  re-distilled  methylated  spirits  of  93  per  cent,  strength  by  the^ 
hydrometer.  The  dextrin  came  down  as  a flocculent  precipitate,  was 
thoroughly  shaken  up,  and  then  the  liquid  was  heated  to  boiling  point  and 
allowed  to  cool  slowly.  The  dextrin  then  adhered  to  the  walls  of  the  flask. 
The  spirit  was  poured  off,  the  dextrin  dissolved  in  about  100  c.c.  of  water, 
filtered  and  again  precipitated  by  exactly  similar  treatment  with  alcohol. 
The  operation  was  repeated  a third  time,  the  spirit  last  used  being  of  89 
per  cent,  hydrometer  strength.  On  dissolving  up  the  precipitated  dextrin, 
evaporating,  drying  and  weighing,  a quantity  of  about  8 grams  was  re- 
covered. A 10  per  cent,  solution  of  this  dextrin  had  a rotary  power  of 
18-15°  in  the  100  m.m.  tube,  equal  to  a specific  rotary  power  of  181-5°,  a 
figure  which  is  considerably  below  that  given  for  pure  dextrin. 

A gravimetric  determination  of  cupric  reducing  power  gave,  on  calculating 
Reducing  sugars,  as  glucose  (K)  . . . . . . 13-51 

or 

Reducing  sugars,  as  maltose  . . . . . . . . 23-84 

Assuming  the  precq^itated  “ dextrin  ” to  consist  of  dextrin  and  maltose, 
its  composition  is — 

Dextrin  . . . . . . . . . . . . . . 76-16 

Maltose  . . . . . . . . . . . . . . 23-84 


CONFECTIONERS^  RAW  MATERIALS.  879 


On  calculating  the  specific  rotary  power  from  the  composition  as  above, 


76-16  X 198 
100 

23-84’ X 139-2 
100 


150-79 

33-18 

183-97 


a figure  which  closely  agrees  with  the  observed  opticity.  It  would  appear, 
therefore,  that  dextrin  precipitated  in  this  manner  contains  nearly  a quarter 
of  its  weight  of  maltose.  It  is  scarcely  probable  that  any  notable  proportion 
of  free  maltose  could  thus  be  several  times  precipitated  with  dextrin.  As 
malto-dextrin  is  not  separable  into  maltose  and  dextrin  by  any  possible 
treatment  with  alcohol,  but  is  dissolved  and  precipitated  as  a homogeneous, 
substance,  the  obvious  deduction  is  that  starch  sugars  contain  malto-dextrin 
in  considerable  quantity.  As  the  molecular  weight  of  malto-dextrin, 

f C12H22O11 

i (C12H20O10)  25 

is  990  against  342  for  maltose,  then  23*84  per  cent,  of  maltose  is  equivalent 
to  69*01  per  cent,  of  malto-dextrin,  and  the  composition  of  the  precipitated 
matter  becomes 


Dextrin  . . . . . . . . . . . . . . 30-99 

Malto-dextrin  . . . . . . . . . . . . 69-01 


100-00 

Modifying  the  figures  given  in  column  No.  IIa.,  in  the  light  of  this  inves- 
tigation of  the  matter  precq^itated  by  alcohol,  the  following  is  the  approxi- 
mate composition  of  the  sample  of  starch-sugar  : — 

Water 

Mineral  Matter 
Dextrin 

Malto-dextrin  | 

Maltose 
Dextrose  . . 


That  is  to  say,  the  dextrin  being 

5-02  -f  7-32  = 12-34 

instead  of  16*20,  we  have  in  the  20  per  cent,  solution  2*47  grams  of  dextrin 
and  14*49  of  sugars,  making  16*96  grams  of  organic  solids  per  100  c.c.  instead 
of  13*72  grams  of  sugars  as  assumed  in  the  previous  calculation.  Then  if 

14*49  X 2*78  = 40*28°, 

the  observed  rotation  is  greater  than  that  required  for  the  whole  of  the  sugar 
being  maltose,  and  precludes  the  presence  of  any  dextrose.  The  total 
maltose,  3*86  -f  68*42  = 72*28,  in  the  modified  analysis,  agrees  closely  with 
the  figure  obtained  when  the  reducing  sugars  are  calculated  entirely  as 
maltose,  viz.,  71  *35  per  cent.  If  the  conclusion  based  on  the  analysis  of  this 
sample  be  correct,  the  substance  known  as  starch  sugar  may  be  viewed  as 
essentially  a mixture  of  dextrin,  malto-dextrin,  and  maltose. 

With  the  well-marked  composition  of  starch  sugar  it  is  to  be  regretted 
that  the  name  used  both  popularly  and  commercially  is  a misnomer.  Starch 
sugar  is  commonly  called  starch  “ glucose,”  whereas  evidently  a far  better 
name  is  either  starch  sugar  or,  if  preferred,  “ starch  maltose.” 

‘ ^ It  is  common  knowledge  that  some  time  ago  the  invert  sugar  produced 


15-20 

0-18 

5-02 

11-18 

68-42 

nfi 


100-00 


880 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


by  one  British  manufacturer  was  found  to  be  contaminated  with  arsenic.  As 
a result  an  active  search  for  that  poison  has  been  made  in  all  sorts  of  articles 
of  food,  and  among  these  starch  sugar,  because  of  its  unfortunate  popular 
name,  has  been  an  object  of  much  suspicion.  Many  samples  of  such  starch 
maltose  have  been  examined  by  the  authors  for  arsenic,  and  up  to  the  present 
they  have  not  found  one  containing  any  arsenic  contamination  ; neither,  so 
far  as  they  are  aware,  has  any  specimen  of  this  substance,  among  the  multi- 
tude which  have  been  submitted  to  analysis  by  public  analysis  and  others, 
received  condemnation.  It  is  no  more  than  justice  to  state  that  starch 
sugar  or  starch  maltose  is  made  from  pure  materials,  absolutely  harmless  in 
the  manner  in  which  they  are  employed,  and  that  the  manufacture  is 
conducted  under  perfectly  sanitary  conditions.  In  fact,  neither  on  scientific, 
nor  even  on  sentimental  grounds,  is  there  anything  any  more  objectionable 
in  the  manufacture  of  starch  maltose  than  there  is  in  that  of  cane  sugar. 

Of  the  constituents  of  starch  sugar  it  may  be  said  that  maltose,  although 
a crystalline  sugar,  crystallises  much  less  readily  than  does  cane  sugar. 
Dextrin,  or  as  it  is  sometimes  called,  British  gum,  is  a tasteless  gummy 
body,  which  does  not  crystallise  itself,  and  exercises  an  inhibitory  action 
on  the  crystallisation  of  other  sugars.  Its  use  is,  therefore,  as  a preventa- 
tive of  crystallisation  ; and  in  some  goods  starch  sugar  is  employed,  in 
order  to  prevent  cane  sugar  crystallising,  on  much  the  same  lines  as  a por- 
tion of  the  cane  sugar  is  inverted  by  the  addition  of  cream  of  tartar  or  other 
similar  acid  during  sugar  boiling.  In  addition  to  this,  dextrin  also  seems 
to  exercise  a specific  moisture-retaining  effect,  and  the  use  of  starch  sugar 
is  therefore  indicated  in  those  goods  which  are  desired  to  retain  a moist 
character. 


Flavouring  Ingredients. 

977.  Fruit. — Fruit  of  various  kinds  is  a most  important  flavouring  agent 
in  flour  confectionery.  Passing  mention  only  need  be  made  of  the  employ- 
ment of  fresh  fruits  in  season  ; thus,  gooseberries,  currants,  raspberries, 
cherries,  plums,  and  apples,  in  their  respective  turns,  are  used  in  the  manu- 
facture of  pies,  tarts,  and  puddings.  In  chemical  composition,  most  of  the 
fruits  consist  largely  of  water,  in  next  highest  proportion  containing  carbo- 
hydrates, and  lastly  small  quantities  of  other  bodies,  as  set  out  in  the  follow- 
ing table,  quoted  from  Hutchison’s  Food  and  Dietetics  : — 

Per  cent. 

85  to  90 
5-5  to  10-5 
2-5 
0-5 
0-5 
0-5 

The  carbohydrates  consist  mostly  of  sugar,  the  principal  one  being 
Isevulose,  or  fruit  sugar,  beside  Avhich,  there  are  varying  amounts  of  cane 
sugar  and  dextrose.  In  addition  to  sugar,  many  fruits  yield  gum-like 
bodies,  to  which,  as  a group,  the  name  of  “ pectin  ” has  been  given.  In 
unripe  fruits  there  is  present  an  insoluble  body  known  as  pectose,  which, 
by  the  action  of  a natural  ferment,  is  converted  into  pectin.  Pectin  exists 
ready  formed  in  ripe  fruits,  and  also  very  largely  in  Irish  moss.  Pectin  is 
soluble  in  water,  and  is  devoid  of  any  marked  flavour  and  odour.  Treatment 
with  a small  quantity  of  acid  causes  its  solution  to  gelatinise.  Like  most 
other  gelatinising  substances,  the  power  of  thus  setting  or  “ jellying  ” is 
seriously  diminished,  or  even  destroyed  by  long  continued  boiling  of  its  solu- 
tion. A solution  of  apple  juice,  on  being  concentrated,  exhibits  this  jelly- 


Carbohydrates 
Cellulose 
Protein 
Fat  . . 

Mineral  Matters 


CONFECTIONERS^  RAW  MATERIALS.  881 

like  consistency  in  a very  marked  form,  and  apple  jelly  may  be  regarded 
as  a pectin  jelly  sweetened  by  the  addition  of  cane  sugar. 

Fruits  contain  notable  quantities  of  various  organic  acids,  among  which 
are  tartaric,  citric,  and  malic  acids.  Cellulose  is  also  present  in  more  or  less 
amount.  In  the  act  of  ripening,  the  sugar  of  fruit  increases  in  quantity, 
while  the  free  acids  diminish  ; at  the  same  time,  the  cellulose  also  more  or 
less  disappears. 

The  characteristic  flavour  of  different  fruits  is  dependent  on  traces  of 
various  ethereal  and  allied  bodies.  Some  of  them  have  been  identified 
and  isolated,  but  many  are  present  in  such  small  quantities  as  to  render 
their  effectual  examination  impossible.  When  dealing  with  fruit  essences 
reference  will  be  made  to  some  of  these  bodies. 

978.  Dried  Fruits. — Certain  kinds  of  fruit  are  more  especially  used  in 
either  the  dried  or  otherwise  prepared  form.  Most  prominent  among  these  is 
the  ordinary  dried  currant  of  the  grocer  and  confectioner.  The  currant  is  not 
a fruit  of  the  same  type  as  our  fresh  currant  of  this  country,  but  is  a small 
stoneless  grape,  which  when  dried  in  the  sun  constitutes  the  currant  of  com- 
merce. The  smaller  raisin,  known  as  a sultana,  is  also  a dried  grape  of 
larger  size  than  the  currant.  Both  these  owe  their  sweetness  to  crystallis- 
able  grape  sugar  or  dextrose.  Cherries  are  also  prepared  for  somewhat 
similar  use,  by  being  stoned  and  then  soaked  in  a concentrated  solution  of 
cane  sugar.  The  following  is  the  result  of  analysis  of  a good  sample  of 
currants,  washed  and  dried,  and  sold  as  of  the  best  quality.  The  fruit  was 
carefully  hand-picked  so  as  to  ensure  the  absence  of  stones  or  grit  before 
analysis. 

Per  cent. 


Water  . . . . . . . . . . . . . . 23*24 

Carbohydrates,  principally  Sugars  . . . . . . 71*82 

Cellulose 1*19 

Proteins  . . . . . . . . . . . . . . 1*67 

Fat 0*10 

Mineral  Matters  . . . . . . . . . . . . 1*98 


100*00 


Energy  in  Calories  . . . . . . . . ..  302*24 

979.  Peel. — A portion  only  of  the  fruits  of  the  orange  and  lemon  type 
is  commonly  used  in  confectionery,  that  portion  being  the  peel.  The  peel 
of  the  orange,  lemon,  and  citron  are  preserved  by  treatment  with  sugar 
syrup,  then  drained,  and  cut  into  slices.  Peel  largely  owes  its  character- 
istic flavour  to  the  essential  oils  found  in  that  portion  of  the  fruit,  and  to 
which  reference  will  subsequently  be  made. 

980.  Preserved  Fruits. — One  obstacle  to  the  regular  use  of  fruit  by  the 
confectioner  is  that  fresh  fruit  is  in  season  for  only  a limited  time  of  the  year. 
To  get  over  this  difficulty,  recourse  is  had  to  various  methods  of  preserva- 
tion. The  simplest  in  principle  is  that  of  preserving  the  fruit  itself  without 
the  addition  of  any  other  body.  This  object  is  effected  by  filling  clean 
bottles  with  the  whole  fruit,  and  adding  water  to  the  neck.  The  bottles 
are  then  stood  in  tanks  containing  water  at  such  a height  as  to  submerge 
the  whole  of  the  bottle  except  the  neck.  The  water  is  slowly  heated  until 
the  boiling-point  is  reached.  The  bottles  are  then  securely  corked  and 
capsuled,  and  if  the  operation  be  successfully  performed,  the  contents  are 
preserved  indefinitely.  To  understand  the  principles  involved  in  the 
preservation  of  fruit,  it  must  be  remembered  that  putrefaction  and  de- 
composition are  due  to  the  action  of  certain  microscopic  living  organisms 

3 L 


882 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


present  on  the  surface  'of  the  fruit,  and  also  pervading  the  atmosphere.  If 
the  life  of  these  organisms  be  destroyed,  then  no  putrefactive  changes  can 
occur  in  the  fruit.  The  heat  of  boiling  water  is  in  this  case  found  to  be 
sufficient  for  the  purpose.  This  preservation,  without  sugar,  results  in 
maintaining  the  fruit  in  a condition  approximating  more  closely  to  that 
of  natural  fruit  than  when  foreign  preservative  agents  are  added. 

981.  Jam. — ^More  usually,  fruit  is  preserved  in  the  form  of  jam,  since  the 
cooking,  and  also  the  addition  of  sugar,  are,  for  many  purposes,  of  advan- 
tage rather  than  otherwise.  Jam  may  be  defined  as  a “ cooked  confection 
of  fruit  to  which  has  been  added  cane  sugar  or  other  wholesome  sweetening 
and  preservative  agent  or  agents.”  The  public  demand  that  jam  shall  be 
palatable  and  also  pleasing  to  the  eye  ; further,  that  it  shall  be  absolutely 
wholesome  in  character  and  contain  nothing  in  the  slightest  degree  dele- 
terious. If  it  fulfil  the  whole  of  these  conditions,  it  is  difficult  to  see  where 
the  interest  of  the  consumer  is  in  any  way  furthered  by  limiting  the  range 
of  constituents  of  jam  any  more  than  is  done  in  the  case  of  any  other  confec- 
tion. 

The  busy  time  of  the  jam-maker  is  in  the  fruit  season.  Fruit,  sugar, 
and  if  necessary  a little  water,  are  added  together  in  a steam- jacketed 
copper  pan  fitted  with  a mechanical  stirrer.  High  pressure  steam  is  ad- 
mitted to  the  jacket,  the  fruit  and  sugar  thus  boiled'being  continually  stirred 
the  whole  of  the  time.  The  boiling  having  proceeded  sufficiently  far,  the 
jam  is  poured  out  of  the  copper  into  a suitable  vessel,  and  then  conveyed 
away  to  the  filling-room,  where  it  is  placed  in  jars  or  other  convenient  recep- 
tacles. In  practice,  it  is  found  an  advantage  to  make  only  a portion  of  the 
fruit  into  jam  during  the  actual  fruit  season.  Large  quantities  of  fruit  are 
simply  converted  into  pulp  by  appropriate  pulping  machines,  then  boiled 
sufficiently  to  thoroughly  sterilise  and  thus  preserve  the  pulp.  Such  pulp 
is  stored  until  required,  when  it  is  transferred  to  the  boiling  coppers,  the 
requisite  quantities  of  sugar  added,  and  the  jam  boiled  and  prepared  in  the 
same  manner  as  with  fresh  fruit. 

The  chemistry  of  jam-boiling  follows  lines  already  indicated  in  other 
manufacturing  operations  which  have  been  described.  Various  kinds  of 
jam  must  differ  according  to  the  character  of  the  fruit,  the  differences  largely 
depending  on  the  degree  of  acidity  of  the  fruit  in  question.  During  the  act 
of  boiling,  such  acid  inverts  more  or  less  of  the  cane  sugar  added.  As  was 
fully  explained  during  the  treatment  of  sugar-boiling,  invert  sugar  exercises 
an  inhibitory  action  on  the  crystallisation  of  the  cane  sugar  also  present. 
Therefore,  the  inversion  of  cane  sugar  by  the  acid  of  the  fruit  prevents  sub- 
sequent crystallisation  of  the  jam.  The  less  acid  the  fruit  contains  the 
less  is  the  amount  of  such  inversion.  With  very  ripe  and  comparatively 
non-acid  fruits  the  requisite  amount  of  inversion  may  be  obtained  by  pro- 
longing the  boiling,  since  the  effect  of  a small  quantity  of  acid  acting  for  a 
longer  time  is  much  the  same  as  that  of  a large  quantity  for  a shorter  time. 
But  too  prolonged  boiling  introduces  another  difficulty — the  pectin  in  the 
jam,  like  other  analogous  substances,  has  its  setting  or  “ jellying  ” proper- 
ties diminished  or  destroyed  by  too  prolonged  boiling,  and  therefore  it  is  not 
always  feasible  or  advisable  to  push  inversion  by  a too  prolonged  boiling. 
In  the  case  of  sugar-boiling,  an  alternative  method  to  the  use  of  acid  for 
“ cutting  the  grain  ” was  described,  in  which  the  prevention  of  granulation 
was  due  to  the  addition  of  starch  sugar  (or  starch  maltose).  The  jam 
manufacturer  finds  the  same  agent  of  service  for  the  same  purpose,  and 
accordingly  with  some  kinds  of  fruit,  and  under  certain  conditions,  a portion 
of  the  sugar  used  consists  of  that  from  starch.  The  maltose  crystallises 
less  readily  than  does  cane  sugar,  and  in  this  way  lessens  the  tendency  to 


CONFECTIONERS^  RAW  MATERIALS. 


883 


crystallisation.  But  the  dextrin  also  present  in  starch  sugar  is  probably 
a yet  more  effective  preventative,  and  exercises  a very  powerful  retarding 
influence  on  the  crystallisation  of  the  jam.  In  those  kinds  of  jam  prepared 
from  acid  fruits,  no  addition  of  starch  sugar  is  necessary.  When  very  acid- 
free  fruits  are  employed,  the  addition  of  starch-sugar  is  an  advantage,  and 
in  no  way  lessens  the  palatability  or  wholesomeness  of  the  jam.  Recently 
some  preparations  of  marmalade  have  been  put  on  the  market,  in  which 
the  slices  of  fruit  float  in  a thick,  transparent,  sirupy  jelly.  These  forms 
appeal  very  strongly  to  the  eye  and  also  to  the  palate  ; in  their  manufacture 
starch  sugar  is  almost  a necessity. 

In  jam-making,  the  boiling  itself  is  a very  efficient  agent  of  preservation  ; 
but  the  sugar  also  acts  as  a preservative  agent,  since  although  dilute  sugar 
solutions  ferment  readily,  yet  sugar  in  this  concentrated  form  is  a powerful 
antiseptic  body. 

Among  things  to  be  condemned  without  reserve  in  the  manufacture  of 
jam  is  the  use  of  unsound  or  decomposed  fruit,  and  also  that  of  low  grade 
and  impure  sugars,  whether  of  the  sucrose  or  maltose  variety.  These  lower 
the  quality  of  the  jams,  and  render  them  decidedly  unwholesome.  Well- 
made  jam  does  not  require  the  addition  of  formalin,  salicylic  acid,  or  other 
similar  preservatives.  The  addition  of  artiflcial  colouring  matter  is  also 
unnecessary,  although  with  modern  harmless  colours,  no  actual  injury 
results  from  their  employment. 

Jam  for  confectioners’  purposes  requires  to  be  made  of  such  a consis- 
tency that  it  will  readily  stand  the  heat  of  cooking  in  tarts,  etc.,  without 
becoming  so  liquid  as  to  run  out.  This  point  is  a very  important  one,  and 
hence  specially  stiff  jams  are  manufactured  for  use  in  confectionery.  The 
purchaser  of  jam  is  warned  against  jams  containing  one  particular  adulter- 
ant, agar-agar,  or  Japanese  isinglass.  The  essential  constituent  of  this 
substance  is  gelose,  a compound  consisting  of  carbon  42-77,  hydrogen  5-77, 
and  oxygen  51-45  per  cent.  Gelose  has  remarkable  gelatinising  power,  and 
one  part  in  500  of  water  will  set  to  a jelly.  The  addition  of  this  substance 
to  jams  enables  them  to  carry  an  excessive  quantity  of  water  and  yet  to  be 
of  firm  consistency.  But  such  jams  become  exceedingly  fluid  on  the  appli- 
cation of  heat,  and  run  out  of  any  goods  in  which  they  are  used  in  the  act 
of  baking. 

982.  Nuts. — ^Nuts  are  characterised  by  the  high  proportion  of  oil  or  fat 
which  they  contain  ; this  amounts  to  from  50  to  60  per  cent,  of  the  whole 
nut,  the  remainder  consisting  of  protein,  carbohydrate  in  small  quantities, 
and  cellulose.  The  oil  of  nuts  is  likely  to  become  rancid  on  keeping  ; for 
this  reason  walnuts  and  other  nuts  are  liable  to  acquire  an  unpleasant  taste 
if  exposed  to  the  air.  Almonds  are  supplied  not  only  as  the  whole  kernel 
of  the  nut,  but  also  in  a ground  condition.  In  this  latter  form  there  is 
opportunity  of  considerable  sophistication.  Buyers  of  ground  almonds 
should  be  on  their  guard  against  removal  of  oil,  and  addition  of  starch, 
sugar,  or  other  foreign  matters.  The  cocoa-nut  is  also  largely  used  for 
confectioners’  purpose.  The  nut,  after  removal  from  the  shell,  has  the  outer 
skin  pared  off  ; the  flesh  of  the  nut  is  then  shredded  and  carefully  dried. 
Again  the  purchaser  should  satisfy  himself  that  no  oil  has  been  removed. 

983.  Essential  Oils. — In  the  case  of  a very  large  number  of  substances, 
their  special  and  peculiar  flavouring  qualities  are  due  to  the  presence  of 
small  quantities  of  substances  possessing  the  particular  taste  and  smell 
in  a marked  degree.  These  flavouring  matters  have,  in  many  cases,  been 
isolated  and  obtained  in  a state  of  purity.  In  a large  number  of  instances 
their  physical  properties  are  those  of  a volatile  oil  ; that  is  to  say,  they  are 
liquid,  more  or  less  oily  in  their  nature,  evolve  a distinct  and  often  powerful 


884 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


odour  at  ordinary  temperatures,  and  boil  or  distil  at  a much  lower  tempera- 
ture than  the  common  or  fixed  oils. 

984.  Oil  of  Peppermint. — ^This  substance  is  prepared  from  the  plant 
known  as  peppermint.  The  herb  is  cut  and  soaked  in  water  in  the  boiler  part 
of  the  well-known  still  ; heat  is  applied  and  as  the  water  boils,  its  steam  car- 
ries along  with  it  the  vapour  of  the  essential  oil  of  peppermint.  The  steam 
is  condensed,  and  the  resultant  water  is  found  to  be  charged  with  the  odour 
and  taste  of  peppermint  in  a much  more  concentrated  form  than  in  the  plant 
itself.  In  this  way  was  made  the  old-fashioned  housewife’s  “ peppermint 
water.”  But  with  this  operation  of  distillation  properly  conducted  on 
large  quantities  of  peppermint,  the  distilled  peppermint  water  is  found  to 
contain  an  oil  which  rises  to  the  surface,  and  may  then  be  separated.  On 
these  principles  are  prepared  commercial  oil  of  peppermint,  and  the  manu- 
facture of  this  oil  may  be  taken  as  a type  of  that  of  many  other  essential  oils. 

In  composition  this  oil  consists  largely  of  the  substance  termed  menthol, 
which  is  a crystallisable  solid,  melting  at  42°  C.,  and  an  alcohol  in  chemical 
composition.  This  body  in  its  free  state  is  a well-known  article,  and  is 
simply  obtained  by  freezing  the  oil,  when  menthol  separates  in  the  solid 
form,  and  is  purified  from  the  still  liquid  adherent  oil  by  pressure,  or  drying 
in  a centrifugal  machine.  This  de-mentholised  oil  is  either  sold  as  such, 
or  used  as  an  adulterant  of  the  oil  itself.  Another  form  of  adulteration  is 
the  addition  of  either  wood  turpentine  or  other  bodies  of  the  terpene  group. 

785.  Analysis  of  Essential  Oils. — Substances  commanding  such  a high 
price  as  essential  oils  offer  peculiar  and  special  temptations  to  the  adulterator, 
hence  their  composition  should  be  checked  by  analysis.  The  foUovnng  is 
an  outline  of  the  principles  involved  in  such  examination  : — 

I.  Essential  oils  have  a fairly  definite  specific  gravity  varying  for  the 
one  oil  with  well-defined  limits. 

II.  Many  oils  exercise  a rotary  power  on  polarised  light  ; consequently, 
like  the  sugars,  essential  oils  are  examined  by  the  polarimeter.  It  is  usual 
to  express  the  results  in  degrees  of  dextro-  or  laevo -rotation  when  measured 
in  a decimetre  tube. 

HI.  The  boiling  point  of  essential  oils  is  fairly  constant  for  the  same 
oil,  and  so  the  temperature  of  the  boiling  point  is  also  determined. 

rV.  The  oil  may  contain  some  special  compound  on  which  its  value 
largely  depends.  If  this  compound  can  be  readily  estimated  with  accuracy, 
such  determination  is  an  important  guide  in  the  commercial  valuation  and 
determination  of  purity  of  the  oil. 

Applying  these  principles  to  oil  of  peppermint,  the  following  are  the 
requirements  of  this  oil  : — 

I.  Specific  Gravity,  0-900  to  0-920  at  15-5°  C. 

II.  Optical  Rotation,  Lsevo -rotary,  — 20  to  —30°. 

III.  Boiling  Point.  The  oil  should  not  boil  below  200°  C.,  but  should 
distil  almost  completely  between  200°  and  215°  C. 

IV.  The  menthol  in  the  oil  may  be  determined  approximately  by  cooling 
the  oil  by  means  of  a freezing  mixture,  and  then  introducing  a small  crystal 
of  menthol.  If  the  oil  has  been  de-mentholised  it  remains  more  or  less 
liquid,  but  if  pure,  it  forms  a crystallised  mass  through  separation  of  solid 
menthol.  This  test  is  preferably  replaced  by  an  estimation  of  menthol  by 
purely  chemical  methods. 

986.  Essential  Oil  of  Lemon. — ’This  oil  is  of  vast  importance  to  the  con- 
fectioner, and  is  well  known  as  a light  yellow  liquid  of  extremely  fragrant 
odour.  Unlike  peppermint  oil,  that  of  lemon  is  not  usually  obtained  by  a 
process  of  distillation.  The  essential  oil  resides  in  small  cells  immediately 


CONFECTIONERS^  RAW  MATERIALS. 


885 


below  the  outer  surface  of  the  lemon,  and  these  are  burst  on  bending  the 
peel.  For  many  cookery  purposes,  the  flavouring  matter  is  obtained  by 
grating  off  the  outer  layer  of  the  skin,  which  grating  is  then  known  as  the 
“ zest  ” of  the  lemon.  The  process  of  manufacture  is  conducted  on  similar 
principles.  The  interior  of  the  lemon  is  first  removed,  leaving  its  rind  in 
two  cups ; these  are  turned  inside  out,  and  the  ejected  essence  viped  off 
the  originally  outer  surface  by  a sponge.  This  operation  is  continued  until 
the  sponge  is  saturated,  when  the  oil  is  squeezed  out  into  a vessel,  and  the 
collecting  operation  continued. 

In  composition,  oil  of  lemon  consists  principally  of  a terpene,  having 
an  analogous  composition  to  that  of  wood-turpentine,  and  to  which  the 
names  of  lemon-terpene  and  limonene  have  been  given.  This  body  differs 
from  turpentine  in  that  it  possesses  a higher  boiling  point  and  a higher  rotary 
power  than  the  latter.  As  a flavouring  agent  the  terpene  of  lemon  oil  is 
comparatively  of  little  value,  the  essential  flavouring  matter  being  an  alde- 
hyde, CioHieO,  known  generally  as  citral.  Oil  of  lemon  contains  citral 
in  quantities  varying  from  4 to  7 per  cent.  For  some  purposes  the  presence 
of  the  lemon  terpene  is  considered  an  objection,  and,  therefore,  there  are 
at  present  put  on  the  market  so-called  terpeneless  oils  of  lemon  in  which  all 
or  part  of  the  terpene  has  been  removed,  and  the  citral  with  other  flavour- 
ing ingredients  alone  remains.  Such  oils  are  prepared  by  a process  of  dis- 
tillation in  vacuo  ; the  terpenes,  having  a lower  boiling  point,  first  distil 
over  and  leave  behind  the  citral  residue. 

Like  the  other  oils,  there  are  certain  requirements  which  that  of  lemon 
are  expected  to  fulfil  ; of  these  the  following  is  a summary  : — 

I.  SpecifiG  Gravity.  0-857  to  0-860. 

II.  Optical  Rotation.  Not  below  -f  59°. 

III.  Boiling  Point.  Not  below  170°. 

IV.  On  being  subjected  to  fractional  distillation,  the  first  10  per  cent, 
distilled  over  will  exhibit  a less  optical  rotation  than  that  of  the  original 
oil,  but  such  difference  should  not  exceed  two  degrees.  This  last  limit  is 
that  laid  down  by  the  British  Pharmacopoeia,  but  the  amount  of  such  difler- 
ences  varies  considerably  in  different  years.  A fairer  figure  for  general  use 
is  3*0°,  and  this  is  the  limit  adopted  by  Parry.  Thus  recently  examined 
oil  of  undoubted  purity  gave  the  following  figures  : — 

Optical  rotation  for  whole  oil  . . . . . . -1-62-5° 

Optical  rotation  of  first  10  per  cent,  of  distillate  . . -f  57-4° 


Difference  . . . . . . . . . . 5-1° 

Oils  of  lemon  are  frequently  sold  with  the  results  of  a direct  estimation  of 
citral  given  ; but,  for  several  reasons,  this  is  no  very  true  guide  to  value. 
In  the  first  place,  the  results  obtained  by  the  rougher  methods  of  estimating 
citral  may  be  far  from  accurate,  and  an  investigation  of  the  methods  of 
sophistication  indicate  other  and  more  cogent  reasons  for  distrusting  citral 
estimations  as  an  indication  of  actual  value. 

987.  Adulteration  of  Oil  of  Lemon. — ^In  earlier  days,  the  principal  adul- 
terant of  oil  of  lemon  was  turpentine,  and  even  now  samples  are  at  times 
met  with  containing  some  40  or  50  per  cent,  of  this  body.  The  limitations 
previously  given  will  readily  serve  to  detect  adulteration  with  oil  of  turpen- 
tine, since  this  body  has  an  optical  rotation  of  from  — 40°  to  -f-  20°  accord- 
ing to  source,  and  a boiling  point  of  about  157°.  Any  large  admixture  of 
turpentine  will  lower  the  optical  rotation  of  oil  of  lemon,  but  this  can  be  to 
some  extent  masked  by  the  addition  of  cheap  oil  of  orange,  which  has  a rota- 
tion of  from  -f  92  to  98°.  By  boiling  and  fractionally  distilling,  the  presence 
of  turpentine  is  clearly  revealed.  First,  it  lowers  the  boiling  point  ; and, 


886 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


secondly,  the  first  fraction  of  distillate  will  have  a much  lower  optical  rota- 
tion, since  the  terpenes  of  either  oil  of  lemon  or  oil  of  orange  agree  very 
nearly  with  the  original  oils  in  rotary  power.  It  is  for  this  reason  that  the 
limit  of  3°  has  been  laid  down,  although,  as  first  stated,  this  is  not  suffi- 
ciently elastic  to  include  all  pure  oils.  But  when  a difference  of  as  much  as 
12  or  even  15  degrees  occurs,  as  was  the  case  in  some  samples  examined, 
which  had  been  recently  sold  by  well-known  firms,  then  evidently  the  buyer 
is  being  subjected  to  a fraud  of  a very  marked  kind.  But  the  use  of  oil  of 
turpentine  is  now  largely  superseded  by  adulteration  of  a much  more  in- 
sidious description.  In  the  manufacture  of  terpeneless  oil  of  lemon,  lemon 
terpenes  are  largely  produced  as  a waste  product.  As  such  terpenes  con- 
stitute some  93-95  per  cent,  of  pure  oil  of  lemon,  it  will  be  seen  that  their 
addition  cannot,  very  largely,  alter  the  chemical  constitution  of  the  oil, 
except  by  lessening  the  proportion  of  the  (approximately  5-6  per  cent, 
fraction  of)  citral  and  allied  constituents.  Neither  the  boiling  point  nor 
the  optical  rotation  of  the  oil  is  thus  affected  ; and  further,  the  first  10  per 
cent,  of  distillate  will  also  agree  with  the  standard  tests.  There  remains 
the  direct  estimation  of  citral,  but  unfortunately,  from  the  present  point  of 
view,  oil  of  lemon  is  not  the  only  source  of  citral.  Verbena,  or  as  sometimes 
called  “ lemon  plant,”  and  also  lemon  grass,  yield  oils  which  contain  about 
80  per  cent,  of  citral,  and  consequently  lemon  grass  oil  forms  a comparatively 
very  cheap  source  of  citral.  A mixture  of  say  94  parts  of  lemon  terpene  with 
6 of  lemon  grass  oil,  will  answer  not  only  to  the  B.P.  {British  Pharmacopoeia) 
limitations  before  quoted,  but  also  to  a direct  citral  estimation.  Therefore,  the 
simultaneous  addition  of  lemon  grass  oil  as  well  as  lemon  terpenes  to  oil  of 
lemon  evades  both  the  B.P.  tests,  and  also  a direct  citral  determination.  But 
although  such  a mixture  may  answer  to  the  tests  mentioned,  it  is  in  no  way 
a true  or  efficient  practical  substitute  for  pure  oil  of  lemon.  Oil  of  lemon 
contains  other  odoriferous  constituents  than  citral,  which  latter  are  not 
furnished  by  lemon  grass  oil  ; and  this  oil  contains  odorous  and  flavouring 
matters  which  are  foreign  to  oil  of  lemon.  The  presence  of  lemon  grass  oil 
is  revealed  by  the  odour  of  verbena  possessed  by  the  oil,  and  this  can  fairly 
readily  be  detected  by  the  expert.  A considerable  assistance  in  applying 
the  “ nose  test  ” to  lemon  oil  is  to  have  it  distilled  in  vacuo  to  10  per  cent, 
of  the  original  volume,  and  then  smell  the  concentrated  citral,  etc.,  residue 
either  in  its  normal  condition  or  after  dilution  vdth  pure  concentrated  alcohol. 
In  the  absence  of  the  terpenes  the  nose  can  often  better  judge  the  character, 
origin,  and  quality  of  the  essential  flavouring  bodies  present.  When  making 
an  analysis  of  oil  of  lemon  it  is  no  very  difficult  matter  for  the  chemist  to 
return  this  concentrated  residue  of  distillation  to  his  client,  and  allow  him 
to  exercise  his  own  judgment  on  its  odorous  qualities.  Nobody  can  feel 
more  strongly  than  chemists  the  urgent  necessity  for  buying  oil  of  lemon 
only  on  analysis  ; but  failing  this  very  obvious  precaution,  the  buyer  may 
generally  take  it  for  granted,  that  given  a range  of  oils  supplied  by  one  and 
tlie  same  dealer,  he  will  get  as  good  (if  not  the  best)  value  for  his  money  by 
selecting  oils  of  the  top  quality,  as  by  taking  those  of  lower  price.  If  he  has 
a preference  for  diluted  oils,  the  most  economic  method  of  gratifying  it  is 
by  buying  pure  oil,  and  lemon  terpene,  and  mixing  them  at  his  own  discretion. 

988.  Essential  Oil  of  Orange. — ^This  oil  like  that  of  lemon  is  prepared 
from  the  rind  of  the  fruit.  In  commerce  there  are  two  varieties,  the  oils  of 
sweet  and  bitter  orange.  Pure  orange  oil  has  a specific  gravity  of  0-848  to 
0-856.  The  optical  rotation  of  these  oils  is  very  high,  usually  falling  between 
-f  94°  and  + 98°.  The  oil  commences  to  boil  at  173°  to  174°.  As  with  the 
oil  of  lemon  adulteration  is  practised  by  the  addition  of  waste  terpenes  of 
oils  of  orange  and  lemon. 


CONFECTIONERS’  RAW  MATERIALS. 


887 


989.  Orange  Flower  Water. — ^An  odoriferous  and  flavouring  agent  is 
also  contained  in  the  flowers  of  the  orange,  and  is  extracted  by  adding  water 
to  the  petals  of  the  flower  and  then  distilling.  The  resultant  distillate  con- 
tains an  essential  oil  known  as  oil  of  neroli.  When  the  distillate  is  suffl- 
ciently  concentrated  this  oil  floats  on  the  surface  and  is  separated.  The 
watery  portion  owes  its  flavour  and  odour  to  the  fact  that  it  holds  a trace  of 
the  essential  oil  in  solution  and  is  termed  orange  flower  water. 

990.  Essential  Oil  of  Almonds. — •Almonds  not  only  contain  a true  and 
non-volatile  oil,  but  also  a substance  called  amygdalin,  which  by  taking 
up  water,  is  converted  into  dextrose,  essential  oil  of  almonds,  and  hydro- 
cyanic acid.  The  essential  oil  is  obtained  by  a process  of  distillation,  and 
is  then  freed  by  appropriate  processes  from  the  hydrocyanic  acid.  Such 
volatile  oil  of  almonds  is  essentially  benzaldehyde,  CyHeO,  and  has  a pungent 
characteristic  odour.  This  oil  is  employed  to  fortify  almond  confectionery, 
a less  proportion  of  almonds  being  used,  and  a larger  portion  of  sugar  or 
other  sweet  bodies  employed.  In  ground  almonds,  as  supplied  ready-made 
to  the  confectioner,  this  type  of  adulteration  should  be  carefully  watched 
for.  It  is  only  within  certain  limits  that  this  employment  of  essential 
oil  is  advisable,  since  its  too  generous  use  gives  a strong  over-powering 
flavour,  markedly  different  from  the  delicate  taste  of  the  almond  itself. 
Pure  natural  oil  of  almonds,  freed  from  hydrocyanic  (prussic)  acid,  is  worth 
from  255.  to  305.  per  lb.,  while  inferior  oils  and  fraudulent  and  poisonous 
substitutes  range  in  price  from  205.  to  as  low  as  M.  per  lb. 

Benzaldehyde  is  manufactured  on  the  large  scale,  and  is  found  on  the 
market  as  “ artificial  oil  of  almonds.”  This  substance  is  used  as  a cheap 
perfuming  agent,  but  its  odour  is  not  sufficiently  delicate  to  permit  of  its 
being  used  in  the  highest  class  of  perfumery,  to  Say  nothing  of  confectionery. 

Oil  of  Mirhane  is  sometimes  employed  as  an  adulterant  of  oil  of  almonds, 
and  chemically  consists  of  nitrobenzene,  C6H5NO2,  mixed  with  various 
impurities.  It  has  a coarse  almond-like  odour,  and  is  poisonous  when 
taken  internally.  Comparatively  recently  a fatal  case  of  poisoning  occurred 
through  oil  of  mirbane  being  mistaken  for  oil  of  almonds. 

991.  Standards  of  Purity  for  Essential  Oils.— The  authors  applied  to 
the  Confectioners’  Vegetable  Colours  and  Fruit  Essences  Company,  Ltd., 
Stratford,  London,  for  permission  to  insert  the  results  of  their  analyses  of 
pure  oils  sold  by  the  Company,  as  illustrations  of  the  conformity  of  such 
oils  with  the  standard  requirements  laid  down  by  various  authorities. 
Permission  having  been  granted,  they  append  the  results  ; — 


Essential  Oils,  Standaeds  of  Pueity. 


standard  Requirements. 

Oil  of  Peppermint. 
Specific  gravity,  0*900  to  0*920 
Optical  rotation,  — 20°  to  — 30°  . . 

Boiling  point,  not  below  200°  C.  ; should 
distil  almost  completely  between  200° 
and  215°  C. 


Results  obtained  on 
Pure  Commercial  Oils. 


0*909 

-24*65° 

About  I per  cent,  distilled 
off  at  200°  C.,  distilled 
almost  completely  be- 
tween 200°  and  215°  ; dis- 
tillation practically  com- 
plete at  216°  C. 


Essential  Oil  of  Lemon. 

Specific  gravity,  0*857  to  0*862  . . . . 0*857 

Optical  Rotation,  -f  59°  to  -f  64°  . . + 60*75° 


888 


THE  TECHNOLOGY  OF  BREAD-MAKING. 


Boiling  point,  170°  to  172°  C.  . . . . 170*5°  C. 

On  distilling,  first  10  per  cent,  of  distillate  10  per  cent.  fraction, 
should  have  a rotary  power  within  3°  of  + 58-50°.  Difference, 

that  of  the  original  oil.  2-25°. 


Essential  Oil  of  Orange. 


Specific  gravity,  0-848  to  0-856 
Optical  rotation,  -f  94°  to  + 98°  . . 

Boiling  point,  173°  to  174°  C. 

On  distilling,  first  10  per  cent,  of  distillate 
should  have  a rotary  power  within  5°, 
above  or  below,  that  of  original  oil. 


0-848. 

+ 96-666° 

173° 

10  per  cent,  fraction, 
-f  94-583°.  Difference, 
2-083°. 


Essential  Oil  of  Almonds. 

Specific  gravity,  1-045  to  1-055  . . . . 1-048 

Optical  rotation,  inactive  . . . . . . 0-0° 


Oil  of  Caraway. 
Specific  gravity,  0-910  to  0-920 
Optical  rotation,  -f  70°  to  -j-  85°  . . 

On  fractional  distillation,  not  more  than 
25  per  cent,  should  distil  below  185°  C.,  and 
40  to  50  per  cent,  between  220°  and  230°  C. 


0-915 
+ 75-05° 

Below  185°  C.,  16-4  per 
cent.  Between  220  and 
230°  C.,  47-4  per  cent. 


992.  Other  Essential  Oils. — 'These  must  be  passed  over  with  but  the 
slightest  reference.  The  various  spices,  allspice  or  pimento,  cinnamon, 
cloves,  etc.,  all  yield  essential  oils,  and  these  are  in  many  ways  of  use  to  the 
confectioner.  Among  the  spice  oils  the  most  important  are  that  of  allspice 
or  pimento,  and  oil  of  cloves.  These  are  somewhat  similar  in  character, 
and  both  contain  a phenol  known  as  eugenol.  In  oil  of  cloves  the  eugenol 
amounts  to  as  much  as  from  85  to  90  per  cent.  The  oil  should  have  a specific 
gravity  of  1-048  to  1-065,  and  a slight  left-handed  optical  rotation, 
never  more  than  — 1-5°  and  usually  under  — 1-0°.  In  pimento  oil  the 
specific  gravity  should  not  fall  below  1-040,  and  the  optical  rotation  is 
usually  about  — 2°,  and  should  never  exceed  — 4°. 

These  oils  already  dealt  with  may  be  taken  as  types,  and  for  particu- 
lars of  others,  systematic  treatises,  such  as  Parry’s  Essential  Oils,  must  be 
consulted. 


993.  Essences. — 'There  is  a more  or  less  subtle  distinction  between 
essential  oils  and  essences.  Thus,  essence  of  lemon  is  not  necessarily  the 
same  as  essential  oil  of  lemon.  Many  essences  are  solutions  of  essential 
oils  and  other  flavouring  ingredients  in  alcohol.  An  illustration  of  these 
is  offered  by  the  well-known  essence  of  mixed  spice  of  the  confectioner,  and 
used  largely  in  the  manufacture  of  “ Hot-cross  Bun.”  The  real  flavouring 
matter  of  such  essence  is  [a  mixture  of  essential  oils  of  different  kinds  of 
spice  ; but  many  samples  also  contain  alcohol  in  large  quantities  running 
up  in  some  cases  to  as  much  as  80  per  cent,  (and  in  extreme  instances  90 
per  cent.)  of  the  total  essence.  Samples  such  as  these  are  now,  however, 
of  great  rarity.  With  the  increased  duty  on  spirits,  the  oils  themselves 
are  frequently  but  little  dearer  than  the  alcohol.  Such  essences  now  fre- 
quently consist  of  a mixture  of  the  essential  oils  with  lemon  or  orange  ter- 
penes.  As  diluting  agents  these  bodies  are  quite  as  suitable  as  alcohol. 

Essential  oils  and  essences  require  constant  supervision,  and  all  users 
of  any  but  the  very  smallest  quantities,  will  find  their  frequent  analysis  to 
amply  repay  them. 

994.  Fruit  Essences. — ^The  composition  of  fruits  has  been  already  dis- 


CONFECTIONERS^  RAW  MATERIALS. 


889 


cussed,  but  as  their  flavouring  matters  are  prepared  in  a more  or  less 
concentrated  form,  they  require  some  attention  under  this  section  of  our 
subject.  There  is  a small  class  of  fruits  of  which  the  flavouring  matter 
has  been  identified  as  largely  composed  of  one  or  more  definite  chemica,! 
compounds.  Thus  as  already  explained,  the  essential  oil  of  bitter  almond 
consists  of,  and  is  identical  with,  benzaldehyde.  The  following  are  other 
instances  of  chemical  compounds  which  are  the  source  of  the  flavour  of 
fruits  : — 

Fruit.  Flavouring  Compounds. 

Jargonelle  Pear  . . . . . . Amyl  acetate. 

Quince  . . . . . . . . Ethyl  pelargonate. 

Pine-apple  . . . . . . . . Ethyl  butyrate. 

By  this  is  meant,  not  merely  for  example,  that  the  flavour  of  the  jargon- 
elle pear  is  simulated  by  acetate  of  amyl,  but  that  that  substance  is  the 
actual  flavouring  body  of  the  pear  itself.  For  these  and  possibly  one  or  two 
other  bodies,  the  essential  flavouring  ingredients  are  thus  obtained  in  a pure 
form  from  outside  sources  ; and  what  is  sold  as  essence  of  jargonelle  pear  is 
largely,  if  not  entirely,  amyl  acetate  in  a more  or  less  concentrated  condition. 

Another  group  of  essences  consists  of  those  of  an  artificial  nature,  built 
up  from  a number  of  essential  oils  and  other  flavouring  ingredients,  accord- 
ing to  each  particular  manufacturer’s  recipe.  Some  of  these  are  pleasant  in 
flavour,  and  others  the  reverse  ; but  whether  pleasant  or  unpleasant,  most 
of  them  bear  but  a very  distant  resemblance  to  the  fruit  they  are  supposed 
to  imitate. 

Manufacturing  chemists  have  devoted  considerable  attention  to  the 
problem  of  conserving  the  natural  essences  of  fruits  in  a concentrated  and 
permanent  form,  and  these  efforts  have  met  with  considerable  success.  It 
would  be  impossible  to  attempt  here  any  description  of  the  manufacturing 
processes  ; but  it  may  be  said  that  the  raw  material  is  fresh  ripe  fruit.  If 
one  takes  the  most  luscious  fruit  imaginable,  its  water,  cellulose,  proteins, 
fat,  and  mineral  matter  do  not  materially,  if  at  all,  contribute  to  the  flavour. 
The  pectin-like  bodies  are  also  flavourless,  while  the  sugars,  although  sweet, 
are  not  distinctively  flavouring.  As  these  constitute  the  main  proportions 
of  the  fruit,  it  is  evident  that  a considerable  concentration  of  the  flavouring 
portion  is  conceivable,  and,  as  a matter  of  fact,  the  solid  portion  of  the  fruit 
can  be  removed  as  an  almost  tasteless  mass.  It  remains  to  drive  off  as 
much  of  the  water  as  practicable,  so  as  to  obtain  a strong  solution  of  those 
constituents  to  which  belong  the  characteristic  taste.  This  being  done,  the 
fluid  is  sterilised  so  as  to  preserve  it  from  decomposition,  and,  as  a result, 
there  is  the  purely  natural  essences  of  the  fruits. 

995.  Vanilla  and  Vanillin. — ^Turning  to  yet  another  distinctly  different 
type  of  flavouring  matters,  there  may  be  taken  as  an  example  the  well- 
knovTi  vanilla  flavour.  This  flavour  is  familiar  as  a result  of  its  presence 
in  chocolate,  ices,  and  other  confections.  The  actual  source  is  the  pod  or 
fruit  of  the  vanilla  plant.  Close  inspection  of  these  pods  shows  them  to  be 
covered  with  a white  efflorescence  ; this  consists  of  the  essential  principle  of 
vanilla,  which  has  exuded  and  crystallised.  To  this  body  the  name  of 
vanillin  has  been  given.  Vanillin  constitutes  about  2 per  cent,  of  the  pod, 
and  like  many  other  flavouring  and  odoriferous  substances  is  an  aldehyde  in 
composition.  To  obtain  the  flavour  of  vanilla  in  the  most  thorough  and 
efficient  manner  there  is  probably  no  simpler  method  than  to  powder  the 
pods  themselves  with  sugar  as  a diluent,  say  I part  of  vanilla  to  9 parts  of 
sugar.  The  objection  to  this  is  that  in  light-coloured  cakes  and  ices  the 
appearance  of  what  look  not  unlike  particles  of  snuff  scattered  throughout 
the  substance  is  unsightly.  To  obviate  this,  a tincture  or  essence  of  vanilla 


890 


THE  TECHNOLOGY  OP  BREAD-MAKING. 


may  be  prepared  by  macerating  the  vanilla  in  alcohol  and  filtering  off  from' 
the  insoluble  matter.  The  solution  thus  obtained  yields  all  the  flavouring 
bodies  of  the  pods  without  the  presence  of  the  objectionable  solid  portion. 

996.  Synthetic  Vanillin. — ^Vanillin  is  one  of  those  substances  which 
has  been  artificially  prepared,  the  process  usually  adopted  being  that  of 
subjecting  eugenol,  the  essential  constituent  of  oil  of  cloves,  to  a process  of 
oxidation.  When  thus  prepared  and  thoroughly  purified,  vanillin  consists 
of  a white  crystalline  matter  of  an  intense  vanilla  odour.  It  is  important 
that  the  vanillin  should  be  thoroughly  freed  from  the  oil  of  cloves  from 
which  manufactured,  or  else  the  substance  is  liable  to  have  itself  a distinct 
odour  and  taste  of  cloves.  When  first  put  on  the  market  vanillin  com- 
manded a very  high  price,  and  in  1876  was  quoted  at  £160  per  lb.,  while  in 
1898  the  price  had  fallen  to  £2  125.  for  the  same  weight.  Vanillin  is  liable 
to  adulteration  with  various  harmless  but  valueless  substances,  the  pre- 
sence or  absence  of  which  can  be  determined  by  analysis.  The  manufacturers 
point  out  that  a mixture  of  2J  per  cent,  of  vanillin  in  sugar  is  equivalent 
in  strength  to  the  vanilla  pod  itself.  As  the  equivalent  of  the  confectioner’s 
“ vanilla  sugar,”  they  recommend  that  2J  per  cent,  vanillin  sugar  should 
be  taken  in  the  same  quantity  as  would  be  taken  of  actual  vanilla.  Vanillin 
forms  a very  useful  substitute  for  vanilla,  and  from  its  greater  cheapness  i» 
somewhat  extensively  used.  It  is  doubtful,  however,  whether  for  the 
most  delicate  flavouring  purposes  it  can  be  considered  a complete  sub- 
stitute for  true  vanilla.  While  undoubtedly  vanillin  is  the  chief  and 
predominant  flavouring  ingredient  of  vanilla,  yet  it  is  probable  that  there 
are  traces  of  other  flavouring  matters  present,  and  the  flavour  of  the  pod 
is  therefore  that  of  vanillin,  plus  such  additional  flavours  as  are  given  by 
these  other  bodies,  which  are  absent  in  artificial  or  synthetic  vanillin. 

Reverting  a moment  to  the  essence  of  vanilla,  while  the  best  is  prepared 
from  fresh  pods,  inferior  qualities  consist  of  tinctures  made  from  the  almost 
exhausted  residue,  which  are  subsequently  fortified  by  the  addition  of 
artificial  vanillin. 

997.  Confectioners’  Perfumes. — ^Not  only  are  flavouring  matters  em- 
ployed by  the  confectioner,  but  he  also  finds  a use  for  bodies  which  are 
ordinarily  regarded  as  scents  or  perfumes  only.  Among  these  the  otto  of 
roses,  and  musk,  find  a place  in  the  store  rooms  of  the  larger  manufacturing 
confectioners.  They,  like  the  essences,  are  bodies  whose  chemistry  pos- 
sesses an  intense  interest,  but  in  common  with  many  other  topics  must 
perforce  be  excluded  from  the  present  review  of  confectioners’  materials. 

998.  Colouring  Matters. — ^The  confectioner  uses  colouring  matters  for 
two  distinct  purposes.  The  one  is  to  give  a richer  colour  to  confections 
which  are  comparatively  colourless  : the  second  is  the  use  of  colour  for 
purely  decorative  purposes. 

999.  Egg  Colours. — Cakes  which  are  made  with  few  or  no  eggs  lack  the 
rich  yellow  tint  produced  by  eggs  unsparingly  used.  To  compensate  for 
this,  artificial  egg  colouring  matter  is  frequently  employed.  For  this  pur- 
pose vegetable  yellows  may  be  employed  ; and  in  fact,  in  the  west  of  Eng- 
land the  saffron  bun  is  a well-known  and  popular  institution.  Not  only 
is  saffron  here  used  as  a colouring  matter,  but  also  as  a flavouring  agent,  for 
such  saffron  buns  have  a distinct  taste  of  their  own,  which  is  entirely  lost 
if  the  saffron  be  omitted.  Other  vegetable  colours  are  also  used  ; but  the 
greater  number  of  egg  yellows  and  egg  colourings  offered  to  the  confectioner 
])elong  to  the  group  known  popularly  as  aniline  colours.  Some  time  ago 
the  authors  examined  a large  number  of  so-called  egg-yellow  colourings, 


CONFECTIONERS^  RAW  MATERIALS. 


891 


including  practically  every  make  of  importance  on  the  market  ; and  among 
other  things  investigated  then’  tinctorial  power  weight  for  weight,  and  price 
for  price.  In  tinctorial  power,  as  against  unit  weight,  the  most  intense 
colour  was  about  180  times  as  strong  as  the  weakest.  In  the  matter  of  cost 
for  the  same  amount  of  colour,  some  samples  were  just  30  times  as  expensive 
as  others.  On  being  tested  for  arsenic,  the  great  majority  of  these  colours 
were  absolutely  pure  ; some  one  or  two,  however,  gave  a sufficient  arsenic 
reaction  to  make  their  use  inadvisable.  When  it  is  remembered  that  these 
colours  are  offered  at  prices  of  from  I5.  to  IO5.  Qd.  per  lb.,  it  will  be  seen  that 
accurate  scientific  valuation  becomes  a matter  of  importance. 

1000.  Decorative  Colours. — ^The  most  familiar  example  of  the  use  of 
colours  for  decorative  purposes  is  that  of  the  tinted  sugars  employed  for 
covering  the  tops  of  birthday  and  similar  cakes.  The  colours  used  are 
soluble  and  are  blended  with  the  mixture  of  sugar  and  white  of  eggs  while 
in  the  pasty  state.  Such  colours  should  not  be  altered  by  traces  of  acid, 
since  acetic  acid  in  small  quantity  is  generally  used  in  making  up  icing 
sugar.  Preferably,  they  should  also  be  unaffected  by  weak  alkalies  as 
sodium  carbonate.  The  principles  which  underlie  the  blending  of  colours 
for  artistic  effect  lies  outside  the  scope  of  the  present  work. 

1001.  Harmless  and  Injurious  Colours. — Certain  colouring  matters  are 
generally  recognised  as  harmless,  while  others  must  be  regarded  as  doubtful, 
and  some  as  decidedly  injurious. 

Harmless  Colours. — Among  the  first  or  harmless  group  are,  with  some  few 
exceptions,  all  organic  colours  obtained  from  the  vegetable  and  animal  king- 
doms. To  these  are  usually  added  the  various  aniline  colours  so  long  as 
they  are  pure  and  contain  no  arsenic.  The  examples  most  frequently  found 
among  confectioners’  colours  are  : — 

Red. — Cochineal,  carmine,  the  juice  of  beet  and  red  berries. 

Yellow. — Saffron,  safflower,  turmeric,  marigold. 

Blue. — Indigo,  litmus,  saffron  blue. 

Green. — Spinach  juice. 

Brown,  various  shades  of. — Caramel  (burnt  sugar). 

Also  various  aniline  colours. 

Doubtful  and  Injurious  Colours. — A few  of  these,  such  as  picric  acid  and 
gamboge,  are  of  organic  derivation.  They  are  mostly,  however,  of  mineral 
origin,  and  may  contain  mercury,  lead,  copper,  arsenic,  chromium,  and  zinc. 
The  follo-sving  are  specific  examples  : — 

Yellows. — Barium  chromate,  and  compounds  of  lead,  arsenic,  and  anti- 
mony. 

Greens. — Compounds  of  arsenic,  and  copper. 

Blue. — Prussian  blue. 

1002.  Legal  Enactments  as  to  Colours. — In  various  countries  laws 
have  been  passed  defining  exactly  such  colours  as  may  and  may  not  be  used. 
Thus  as  early  as  February,  1891,  the  Official  Municipal  Bulletin  of  the  city 
of  Paris  contained  the  following  regulations  : — 

Paris  Ordinance,  1890. — “ Ordinance  concerning  the  colouration  of 
alimentary  Substances. 

Article  1. — The  employment  of  the  colours  herein  after  designated  is 
forbidden  for  the  colouration  of  all  substances  entering  into  articles  of  food. 

Mineral  Colours. 

Composed  of  copper. — Blue  dust  (cendres  bleues),  mountain  blue. 

Composed  of  lead. — Massicot,  minium  or  red  lead,  litharge.  Carbonate 


892 


THE  TECHNOLOGY  OE  BREAD-MAKING. 


of  lead  (white  lead) . Oxychloride  of  lead  (Cashel’s  yellow,  Turner’s  yellow, 
Paris  yellow).  Antimoniate  of  lead  (Naples  yellow).  Sulphate  of  lead. 
Chromates  of  lead  (chrome  yellow,  Cologne  yellow). 

Chromate  of  barium. — Ultramarine  yellow. 

Composed  of  arsenic. — Arsenite  of  copper,  Scheele’s  green,  Schweinfurt 
green. 

Sulphide  of  mercury. — Vermilion. 

Oeganic  Colours. 

Gamboge. — Aconit  Napel. 

Colouring  matters  derived  from  coal-tar,  such  as  fuchsine,  Lyons  blue, 
methylene  blue  ; phthaleins  and  their  derivations  ; eosin,  erythrosin. 

Colouring  matters  containing  among  their  constituents  nitrous  gases, 
such  as  naphthol  yellow,  Victoria  yellow. 

Colouring  matters  prepared  by  the  aid  of  diazo  compounds,  such  as 
tropeolins,  xylidin  reds. 

Article  2. — It  is  permitted  to  use  for  the  colouration  of  sweets  and  other 
food  substances  the  following  coal-tar  colours,  because  of  their  restricted 
employment,  and  the  very  small  quantity  of  the  colouring  substances  which 
these  products  contain: — 

Red  colours: 

Eosin. 

Erythrosin  (methyl  and  ethyl  derivations  of  eosin). 

Bengal  red,  ploxine  (iodine  and  bromine  derivations  of  fluorescin) . 

Bordeaux  reds,  ponceau. 

Acid  fuchsin  (without  arsenic  and  prepared  by  Coupier’s  process). 

Yellow  colours: 

Acid  yellow,  etc. 

Blue  Colours: 

Lyons  blue,  light  blue,  Coupier’s  blue  (derived  from  triphenyl  rosaniline 
or  from  diphenylamine. 

Green  Colours: 

Mixtures  of  the  above  blues  and  yellows. 

Malachite  green. 

Violet  Colour : 

Paris  violet  or  methylaniline  violet.” 

American  Regulations,  1907. — Food  Inspection  Decision  76  of  the  United 
States  Department  of  Agriculture  makes  the  following  regulations  for  the 
employment  of  colouring  matters  in  articles  of  food  : — 

“ The  use  in  food  for  any  purpose  of  any  mineral  dye  or  any  coal-tar  dye, 
except  those  coal-tar  dyes  hereinafter  listed,  wiU  be  grounds  for  prosecu- 
tion. Pending  further  investigations  now  under  way  and  the  announce- 
ment thereof,  the  coal-tar  dyes  hereinafter  named,  made  specifically  for  use 
in  foods,  and  which  bear  a guarantee  from  the  manufacturer  that  they  are 
free  from  subsidiary  products  and  represent  the  actual  substance  the  name 
of  which  they  bear,  may  be  used  in  foods.  In  every  case  a certificate  that 
the  dye  in  question  has  been  tested  by  competent  experts  and  found  to  be 
free  from  harmful  constituents  must  be  filed  with  the  Secretary  of  Agriculture 
and  approved  by  him. 

The  following  coal-tar  dyes  which  may  be  used  in  this  manner  are  given 
numbers,  the  numbers  preceding  the  names  referring  to  the  number  of 
the  dye  in  question  as  listed  in  A.  G.  Green’s  edition  of  the  ScJiultz- 
Julius  Systematic  Survey  of  the  Organic  Colouring  Matters,  published  in 
1904. 


CONFECTIONERS^  RAW  MATERIALS. 


893 


The  list  is  as  follows  : — 

Red  shades  : 

107.  Amaranth. 

56.  Ponceau  3 R. 

517.  Erythrosin. 

Orange  shade  : 

85.  Orange  I. 

Yellow  shade  : 

4.  Naphthol  yellow  S. 

Green  shade  : 

435.  Light  green  S.F.,  yellowish. 

Blue  shade  ; 

692.  Indigo  disulphoacid. 

Each  of  these  colours  shall  be  free  from  any  colouring  matter  other  than 
the  one  specified  and  shall  not  contain  any  contamination  due  to  imperfect 
or  incomplete  manufacture.” 


THE  END. 


INDEX 


PAGE 

A 

Abscissae 

708 

Absolute  temperature 

7 

— Weight  of  hydrogen  . 

15 

Absorption  of  heat  . 

10 

Acetic  acid  .... 

49 

— fermentation 

190 

Acetone 

51 

Achroo-dextrins 

. 84 

Acid,  Acetic  .... 

49 

— , Butyric  .... 

49 

— calcium  phosphate 

465.499 

— , Carbonic  .... 

33 

— , Formic 

. 48 

— , Hydrochloric 

30 

— , — , Use  of,  in  breadmaking 

. 470 

— , Hydrofluoric 

• 38 

— , Lactic 

50 

— , Margaric  .... 

49 

— , Nitric 

36 

— , Nitrous  .... 

36 

— , Oleic 

49 

• — , Palmitic  .... 

49 

— , Phosphoric  .... 

39 

- — , — , Determination  of 

• 759 

— potassium  phosphate 

. 466 

sulphate 

. 466 

— , Silicic 

• 38 

— , Stearic 

49 

■ — , Succinic  .... 

50 

— , Sulphuric  .... 

37 

— , — , Normal  .... 

. 771 

— , Sulphurous  .... 

37 

— , Tartaric  .... 

50.  464 

Acidimetry  and  alkalimetry  . 

• 770 

Acidity  of  bread 

. 774 

meals  or  flours . . 317, 

370, 772 

Acids,  bases,  and  salts 

16 

■ — , Basicity  of  . 

18 

— , Volatile,  Estimation  of, 

by 

Duclaux’s  method  . 

. 776 

— , Fatty  .... 

. 48 

— of  nitrogen  .... 

35 

— of  sour  bread,  Separation  and 

identification  of 

• 774 

— , Organic  .... 

. 48 

Adulterations  and  additions  . 

. 837 

Aerating  agents 

464,859 

Aeration  of  bread,  other  than 

by 

yeast  

• 463 

— process  .... 

. 47i«/ 

Age,  Effect  of,  on  flours  . 716, 

717,  798 

Albumins 

94 

—.Egg 

94.857 

— of  wheat  .... 

102 

Albuminates  .... 

94 

Albuminoids  .... 

PAGE 

91,  96,  98 

Albumoses 

95 

Alcohol,  Absolute 

45.814 

— of  various  strengths  . 

. 815 

— , Absolute,  Preparation  of  . 

. 814 

— , Detection  of  . . . 

45 

— , Ethyl 

44 

— in  bread.  Proof  of  presence  of  . 463 

— Engines 

. 614 

— , Methyl 

44 

Alcohols 

43 

• — , Propyl,  butyl,  and  amyl  . 

. 46 

Alcoholic  fermentation,  and  yeast  1 50 

, Substances  inimical  to  . 

. 166 

, — produced  by 

. 151 

, — susceptible  of  . 

. 150 

viewed  as  a chemical  change  1 50 

Aldehydes 

51 

Aldoses  

51 

Aleurometer  .... 

. 297 

Aleurone  cells  .... 

• 254 

— grains  

. 267 

Alkalies 

16 

Alkalimetry  .... 

. 770 

Alkaline  earths 

16 

Alkaloids 

54 

Allspice,  Essential  oil  of  . 

. 888 

Almond  right-angle  drive 

. 625 

Almonds,  Essential  oil  of 

. 887 

Alum,  copper  sulphate,  and  lime. 

Use  of 

459,  466 

Alum  baking  powders 

. 467 

— , Effect  of,  on  bread  . 

• 467 

— , Special  test  for  . 

841,  842 

American  flour-testing  methods  . 740 

— flours.  Tests  on  . 

735,738 

— high-grade  bread.  Composition 

of 

• 495 

— wheats.  Composition  of 

275,278 

Amides 

54 

— , Determination  of 

• 304 

Amines 

54 

Amino  acids  and  amides 

54 

Ammonia 

34 

Ammonias,  Compound  . 

54 

Ammonium  carbonate 

. 464 

— salts 

34 

Amyl  acetate  .... 

48,  889 

— alcohol 

. 46 

Amylans 

. 87 

Amylo-dextrin  . . . . 

. 87 

Amyl  01  ns 

. 87 

Amylolytic  and  proteolytic 

fer- 

ments  of  wheat.  Ford 

and 

Guthrie  . . . . 

. 324 

Amylopsin 

• 134 

Amyloplasts  . . . . 

267 

Analyser 

• 67 

INDEX.  S95 


PAGE 

PAGE 

Analyses  of  English  and  foreign 

Bakehouse,  Site  for  . 

. 581 

wheats  . . . . 

272,797 

— , Ventilation  of  . . . 

• 594 

Analysis  of  bread 

495.831 

— , Wholesale  bread  and  cake 

606,  608 

Analytic  apparatus  . 

680 

■ — , Working  requirements  of  . 

• 594 

- — balance  .... 

680 

Bakehouses,  Underground 

. 582 

, Adjustment  of 

683 

Baker  and  Hulton  on  strength  of 

— weights  .... 

683 

flour 

• 327 

Apostoloh  system  of  bread-making 

483 

toxins  in  flour 

. 225 

Apparatus,  Measuring 

687 

Baker  and  Hulton’s  researches 

225 

Appert’s  method  of  preservation 

Bakers’  home-made  yeast 

. 241 

from  putrefaction 

188 

Bakeries,  Large 

. 607 

Argon 

12 

Bakery  registers 

. 679 

Artificial  diastase  of  Reychler 

135 

Baking 

. 428 

— drying  of  wheats  and  flours 

362 

— , Effect  of,  on  bacterial  life  . 

. 449 

Ascospores 

176 

— , Time  necessary  for  . 

. 428 

Ash  of  flour,  Snyder  on  . 

758 

Baking  powders 

• 467 

— of  wheat  .... 

69 

, Analysis  of  . . . 

. 828 

wheats  and  flours.  Deter- 

— tests  . . . 292,379,733,850 

mination  of  . . . 

757 

, Alternative  scheme  of  . 

• 749 

Asparagine  .... 

55 

, American 

740.  745 

A spergillus  glaucus  . 

192 

, Authors’  method  of  makir 

Lg  • 745 

Atmosphere  .... 

33 

, M‘Dougall’s  . 

• 733 

Atomic  or  combining  weights . 

13 

, Richardson’s  . 

• 734 

■ , List  of  . 

1 1 

, Special  series  of  . 735,738,749 

— theory 

14 

Balance,  Analytical 

. 680 

Atomicity  or  quantivalence  . 

17 

Banana  flour.  Composition  of . 

. 271 

Atoms  and  molecules 

14 

Barley,  Composition  of  . 

270 

Attemperating  and  measuring  tank 

636 

— , Germination  of  . 

267 

Attenuation  of  worts 

247 

— meal,  Unsuitability  of,  for  bread- 

Auto-dividing,  proving, and  mould- 

making  .... 

• 472 

mg  plant  .... 

653 

Barm,  Compound 

. 252 

Automatic  bakery  . 

658,  676 

— , Malt  extract 

• 515 

— machine  bakeries 

606 

— , Parisian  .... 

250,  253 

— ovens 

672 

— , Virgin 

249,  252 

— prover 

653 

Barms,  Scotch  flour  . 

249,  251 

— temperature  regulator 

227 

— , , Meikle’s  formulae 

. 251 

Avogadro’s  law. 

15 

— , , Montgomerie’s  formulae  250 

— , , Thom’s  formulae 

. 249 

Base,  Definition  of  . 

16 

B 

Bashing  machine 

. 677 

Basicity  of  acids 

18 

Bacilli 

183 

Beard  of  wheat 

• 259 

Bacillus  subtilis .... 

183 

Bearing  supports 

621 

Bacteria 

182,  183 

Bearings 

. 620 

— , Diastatic  action  of 

185 

Beef  fat 

. 867 

■ — , Growth  forms  of . 

182 

Belt  fasteners  .... 

622 

Bacterial  and  putrefactive  fermen- 

Belting 

622 

tations  .... 

187 

Benzaldehyde  .... 

. 887 

— Fermentation,  Action  of  oxygen 

Bermaline  bread.  Analysis  of  . 

• 495 

on 

187 

Birmingham  methods  of  bread- 

Bacteriological  purity,  Compara- 

making  .... 

. 408 

tive,  of  flours  . 

549 

Biuret  reaction  of  proteins 

93 

Bacterium  lactis 

188 

Bleaching  of  flour 

• 375 

— ter  mo 

183 

■ — powder,  chloride  of  lime 

31 

Bakehouse  building,  Requirements 

Blending  and  sifting  plant,  General 

m 

585 

arrangement  of 

. 629 

— , Constancy  of  temperature  in 

595 

— of  flour 

473.629 

— design 

581, 

. 597 

— of  wheat  .... 

• 473 

— for  two  peel  ovens 

599 

Blood  or  serum  albumin  . 

94 

— machinery  .... 

612 

Bottcher’s  moist  chamber 

169 

, Fencing  of  . . . 

589 

Boyle’s  law  .... 

7- 

, when  it  pays  . 

606 

Brake  horse-power  . 

. 624 

— over  shop  .... 

602 

Bran 

258,  349 

- — , Requirements  for 

583 

— cellulose  .... 

261,  263 

, Compactness  of 

594 

— , Composition  of  . 

• 349 

— , Safety  from  fire  . 

588 

Bread  Acts  .... 

. 562 

— , Sanitation  of  . . . 

586 

, Historical  development  of 

• 574 

— , Single  drawplate  oven 

599 

, Intention  of  . 

• 576 

— , Single  peel  oven 

597 

— , Aerated  .... 

• 463 

896 


INDEX. 


PAGE 


PAGK. 


Bread,  Alcohol  in  ...  . 463 

— , Alum  in 842 

— , American,  Analysis  of  . -495 

— analysis  ....  831,834 

— and  cake  factory  . . . 606 

— , Assize  of  ...  . 562,  566 

— , Attractiveness  and  palatability 

of 551 

— - bill,  London  County  Council  . 579 

— , Calcium  sulphate  in  . . . 843 

• — , Chalk  disease  in  . . . .457 

— colour  ....  459,713,831 

— , Complementary  foods  to  . . 551 

- — •,  Composition  of  . . . . 496 

■ — Cooling  of 429 

— crumbliness  ....  458 

— crust,  Colour  of  ....  833 

— , Daren 486 

— , Dark  line  in  cottages.  . . 458 

— , Digestive  and  nutritive  proper- 
ties of,  Jago  . . . .531 

— , , Hopkins  . . 558 

— factory,  Modern  . . . 608 

— -,  Faults  in 457 

— , Flavour  of 833 

— , Gluten 472 

— , Holes  in 457 

— , Hovis 485 

— , “ Improved  standard  ” . . 560 

— improvers 509 

, Commercial  . . . .521 

, Restrictions  on  use  of  . 521,522 

— , Leavened 461 

— , Loss  of  weight  in  oven  . -579 

— , Malt  extract  . . . .487 

— , Mineral  oil  in  . . . . 843 

— , Musty  and  mouldy  . . .194 

— , Nutritive  value  of  . . .525 

— odour 832 

— , Palatability  of  . . . • 55i 

— , Pile  of 292,  832 

— , Price  of 562 

- — , Proof  of 832 

— , Protruding  crusts  of  . . . 458 

— , Quantity  of  water  in  . . . 833 

— , , Standard  for  . 834 

— , Red  spots  in  ...  193 

— , Relative  nutritive  values  of  dif 

ferent  varieties  of  . . . 525 

— , Ropiness  in  . . . .451 

— , Rye 472 

— Souring  of 433 

— , “ Standard  ” . . . *553 

— , Test  for  alum  in  ...  467 

— , Texture  of 831 

— , Turog 487 

— , Typical  American  high  grade  . 495 

— , Vienna 461 

— , Water  in 833 

— , Weighing  of  . . . .562 

— , What  constitutes  sale  by  weight  of  577 
— , Whole  meal  ....  470 

Bread-fruit  flour  . . . .271 

Bread-making  . . . 400,408,483 

— , American  methods  . . .415 

— , Apostoloff  system  of  . . .483 

— , Birmingham  practice  . . 408 

— , Brighton  practice  . . . 408 

— , Belfast  practice  . . . .414 


Bread-making,  Canadian  methods . 

415 

— , Cardiff  practice  . 

415 

— , Crewe  practice  . 

409' 

' — , Eastbourne  practice  . 

409 

— •,  Leeds  and  district  practice 

409 

— , London  practice . 

412 

— , Leicester  practice 

411 

— , Liverpool  practice 

411 

— , Manchester  practice  . 

413 

— , Macclesfield  practice  . 

412- 

— , Malvern  practice 

413 

— methods.  Present,  Callard  on 

406 

— , Modern  practice . 

407 

— , Nottingham  practice 

413 

— , Plymouth  practice 

414 

— , U.S.A.  practice  . 

415 

— , Objects  of  . 

401 

— , Special  methods  of 

461, 485. 

— , Scotch  practice  . 407,414,418,420 

i — , Use  of  alum  in  . 

459 

■ — -,  Various  stages  of 

402 

Breads,  Commercial  analysis  of 

495 

— , Relative  digestibility  of,  Brun- 

ton  and  Tunnicliffe  . 

528. 

1 Break  flours.  Composition  of  . 

348 

' Brewer’s  yeast  .... 

233 

Bromine,  iodine,  and  fluorine 

38 

Brown  and  Morris  on  molecular 

! weights  of  carbohydrates 

75 

Brown,  Heron,  and  Morris  on  starch 

conversion 

127 

Brown  on  influence  of  oxygen 

on 

fermentation 

162 

“ Brownian  ” movement 

183 

Buchner  on  influence  of  oxygen 

on 

1 yeast 

165 

Bunt  or  stinking  rust 

196 

Burette,  Water-absorption 

700 

; Burettes  and  floats  . 

687 

' Butter 

864 

t — , Composition  of  . 

864.  866 

— , Grading  of  . 

864 

— , Rancidity  of  . . . 

867 

— standards  . . . 

865 

1 Butter-making,  Selection  of  i 

[er- 

ments  for  .... 

189 

Butters,  Weak  and  strong 

867 

Butyl  alcohol  .... 

46 

Butyric  acid  .... 

49 

— fermentation 

190 

c 


Cakes,  Colouring  matter  in 

• 843 

Calcium  and  its  compounds 

• . 39 

— acid  phosphate  . 

• 46s 

Calculations  of  quantities 

20 

Calorie  .... 

526 

Calorimeter 

. 766 

Camera  lucida 

. 62 

Cane  and  invert  sugar,  Compara- 

tive  sweetness  of 

. • 873 

— sugar  .... 

85,871 

, Action  of  malt  extract  on]  ^ . 128; 

, Estimation  of 

801,  802,  811 

, Hydrolysis  of 

. 139,144 

, Inversion  of  . 

• 873 

Caramel  . . 

85,  874,891 

INDEX. 


897 


PAGE 


Carbohydrates  . 

74 

— , Classification  of  . 

74 

— , Constitution  of  . 

74 

— , Definition  of 

74 

— , Estimation  of 

800 

Carbon  .... 

31 

— , Compounds  of,  with  hydrogen . 

33 

— dioxide  .... 

32 

--monoxide 

32 

Carbonate  of  soda  . 

464 

Carbonates 

33 

Carbonic  acid  . 

33 

Catalysis  .... 

120 

Cellulose  .... 

76,  88,  294 

— , Composition  of  . 

77 

— , Estimation  of 

818 

— , Existence  of  in  wheat 

77 

— of  bran  .... 

261 

— of  endosperm 

263 

— of  wheat 

77 

Centinormal  solutions 

772 

Cerealin  or  aleurone 

267 

— — — cells 

256 

Cereals,  Composition  of  . 

270 

— , Diseases  of  . 

195 

Chaffing  machine 

678 

Chain  driving  . 

625 

Chains,  Annealing  of 

628 

Chemical  calculations 

18 

— combination  by  volume 

15 

weight . 

12 

— composition  of  flour  . 

• 311 

b344 

wheat  . 

270 

— equations 

13 

— functions  in  mill  . 

850 

— laboratory  . 

680 

Chemistry,  Definition  of 

10 

Chimneys  .... 

586 

Chloride  of  lime,  bleaching  powder 

31 

Chlorides  ..... 

30 

Chlorine  .... 

30 

Chloroform 

48 

— test  on  flour 

840 

Chlorophyll 

265 

Chloroplasts 

267 

Cilium  .... 

183 

Cinnamon,  Essential  oil  of 

888 

Cloves,  Essential  oil  of  . 

888 

Coagulated  proteins . 

95 

Code  for  telegrams  . 

845 

Coke  combustion.  Nature  of 

673 

Collagen  .... 

98 

Colloids  .... 

24 

Colour  investigations 

711 

— of  bread 

709 

— of  flour.  . . . 344,  375,709 

Colouring  matter  in  cakes 

843 

— matters 

890 

Colours,  Harmless  and  iniurious  . 

891 

— , Legal  enactments  as  to 

891 

Combination  ovens  . 

664 

Combining  or  atomic  weights 

13 

, List  of  . 

1 1 

— proportion  . 

13 

Combustion,  Heat  of 

. 525,766 

— of  coke,  Nature  of 

673 

Commercial  breads.  Analysis  of 

495 

— testing  and  chemical  analysis  of 

wheats  and  flours 

307 

PAGE 


" Comp.”  or  baker’s  ” patent  ” 

yeast 241 

Comparison  between  brewers’  and 

distiller’s  yeasts  . . . 216 

Composition  of  ash  of  wheat  . . bg 

— of  organic  bodies  ...  42 

— of  roller  milling  products  . . 345 

Compound  ammonias  . . . 54 

, Definition  of  . . . . 1 1 

— radicals 17 

Compounds  of  carbon  with  hydro- 
gen . . . . . . 33 

Compressed  yeasts,  Characteristics 

of 239 

, Manufacture  of  . . .235 

Conduction  of  heat  ....  8 

Confectioners’  aerating  ingredients 

464. 859 

— enriching  ingredients  . . 860 

— flavouring  ingredients  . . 88a 

— flour 852 

— moistening  ingredients  . . 852 

— raw  materials  . . . .852 

— sweetening  ingredients  . .871 

Conidia 192 

Constituents  of  wheat  ...  68 

Constitutional  formulae  . . . 13 

Construction  of  wheat  grain  . . 68 

Constructive  metabolism  of  plants  265 
Convection  of  heat  ....  8 

Cooling  of  bread  ....  429 

Co-ordinates 708 

Copper  sulphate,  Employment  of, 

in  bread -making  . . .459 

Cottage  loaves.  Dark  line  in  . . 458 

Court  of  reference  . . . 508,523 

Counterpoised  and  weighed  filters  763 

Coverplate  oven  ....  670 

Cream  of  tartar 464 

substitutes  . . . 466 

Crumbliness 458 

Crusts,  Protruding  . . . .458 

Crystalloids  and  colloids ...  24 

Cupric  oxide  reducing  power  . . 84 

Currants 881 

Cuticle  of  wheat  grain,  bran  . .258 

Cystine 92 

Cytase 122 


D 


Damping  wheats 

. 360 

Daren  bread  . . . , 

486,  495 

Darnel 

. . 837 

Dauglish’s  process  of  aerating  bread  47 1 

Decinormal  solutions 

. 772 

Derived  albumins 

94 

Designs,  Typical,  for  bakeries 

• 597 

Detection  of  alcohol . 

45 

Deutero-albumose  . 

95 

Dextrin  .... 

83,  90,  294 

— and  maltose,  Polarimetric  esti- 

mation of 813 

— and  sugar  of  wheat  . . .294 

— and  soluble  starch.  Estimation  of  8 1 8 

— , Chemical  character  of  . . 84 

— ■,  Estimation  of  . . . .805 

— , Hydrolysis  of  . . . .140 

3 M 


898 


INDEX. 


PAGE 

Dextrin,  Molecular  constitution  of  1 30 
Dextrose  or  dextro-glucose  . . 86 

Dialysis 24 

Diamalt 513 

Diastase 124 

— , Action  of,  on  starch  . . . 127 

— baking  tests 826 

— determinations.  Experimental 

comparison  of  . . , . 825 

— , Nature  of 126 

— of  raw  grain  . . . .134 

— , Preparation  of  . . . .816 

— test  on  flours  . . . .825 

— , Reychler’s  artificial  . . . 135 

— , Translocation  ....  266 

Diastatic  action  or  diastasis  . .126 

of  bacteria  . . . .185 

, Conditions  and  substances 

inimical  to.  . . . 133,144 

, Effect  of  heat  on  . . . 133 

, Effect  of  time  and  concen- 
tration on 133 

, Further  experiments  on  . 491 

— capacity.  Measurement  of  . 126 

Dictionary  of  wheat,  Voller  . .285 

Diffusion,  Gaseous  ....  22 

Digestibility 526 

— of  bread 525 

Disease  ferments  . . . .191 

Diseases  of  cereals  . . . .195 

Distillers’ yeast  . . . 172,235 

Dough  ....  306,339,403 

— dividers 646 

— mixing  and  kneading  machines  637 

. 645,646,652 

. 645 


— proving 

— trucks  . 

Doughing  and  baking,  Scotch  methods 


of 

— machinery  . 

Doughs,  Off-hand 
Drawplate  ovens 
Drives,  Belt 
■ — , Various 

Drying  wheats  and  flours 
Duclaux’s  method  of  estimating 
fatty  acids.  Description  of 

, Discussion  of 

Durum  wheat,  Norton 


414,  419 

637 
403 

662 
622 
625 
362 


776 

438 

280 


E 


Egg  albumin 94 

— colours 890 

— whites.  Dried  . . . .858 

Eggs 857 

— , Aerating  action  of  . . -859 

Electric  motors 618 

Element,  Definition  of  . . . 1 1 

Elements  and  compounds,  Descrip- 

^ tion  of 28 

— , List  of II 

Empirical  formula  ....  20 

Endocarp 258 

Endosperm  ....  258,  375 

— , Cellulose  of 263 

Engines,  Internal  combustion  . 613 


English  and  Scotch  wheats,  Analy- 
ses of 

PAGE 

273 

— weights  and  measures 

27 

Enzymes  and  diastatic  action 

120 

— or  soluble  ferments 

I2I 

— , Chemical  properties  of 

122 

— , Classification  of  . 

122 

— , Composition  of  . 

124 

— , List  of 

123 

— , Proteolytic  of  resting  and  \ 
minating  seeds  . 

ger- 

139 

Epicarp 

258 

Epidermis  of  wheat  grain 

258 

Episperm 

258 

Equations,  Chemical 

13 

Erdmann’s  float 

687 

Ergot 

196,  838 

Erythro-dextrins 

84 

Essences 

888 

— , Fruit 

888 

Essential  oil  of  allspice  . 

888 

almonds 

887 

cinnamon  . 

888 

cloves  .... 

888 

lemon 

884 

nerbli 

887 

■ orange 

886 

peppermint 

884 

Essential  oils  .... 

883,888 

, Analysis  of  . . . 

884 

— • — , Standards  of  purity  for 

887 

Esters  or  ethereal  salts  . 

48 

Ethane  

44 

Ethereal  salts  .... 

48 

Ether,  Light-bearing 

65 

Ethers 

47 

Ethyl 

42 

— alcohol  .... 

44 

• — butyrate  .... 

48 

Etiolin 

265 

Expansion  and  contraction  of  gases 

7 

— by  heat  .... 

7 

Explosion  motors  . . 613,614,615 

Extractive  matters  of  cereals 

88 

Eye-piece 

58 

— micrometer 

60 

F 


Factory  Acts 582 

— , Wholesale  bread  and  cake  . 608 

Fat,  Beef 867 

— , Determination  of  . . . 763 

— , Moistening  effect  of  . . . 859 

Fats 49. 860 

• — , Butyro-refractometer  value  of . 862 

— , Chemical  constants  of  . .861 

— , Compound 869 

— , Iodine  value  of  . . . .861 

— , Melting  and  solidifying  points  of  861 

— , Mineral 870 

— , Properties  of  ...  • 863 

— , Reichert-Meissl  value  of  . . 862 

— , Specific  gravity  of  . . .861 

— , Vegetable  . . . . . 868 

Fatty  acids,  or  acids  of  acetic  series  48 
— matters  of  wheat . ...  70 


INDEX. 


899 


Faults  in  bread . 

Fehling’s  solution 
Ferment  . 

— and  dough  . 

• — , Potato 

— , sponge,  and  dough 
Ferments  . 

Fermentation  . 

— , Acetic  . 

— , Action  of,  on  gluten 
— , Aerating  system . 

• — , Alcoholic  {see  also  under 
holic  fermentation) 

— , Butyric 
• — , Changes  in  flour,  resulting  from 
• — , Comparison  of  brewers’  and  dis- 
tillers’ yeast  .... 

■ — , Conditions  affecting  speed  of  . 
- — , Course  of 
- — , Definition  of 
— , Earlier  views  on 
— , Effect  of  addition  of  various 
substances  on  . 

— , salt  on 

— , temperature  on 

— , Experimental  basis  of.  Modern 
theory  of  . 

— , experiments.  Authors’ 

— , History  of  views  of  . 

- — , Influence  of  oxygen  on 
— , Liebig’s  view  of  . 

— , Lactic  .... 

— , Loss  during . 

— , Modern  theory  of 
• — of  dough,  Parenti 
• — of  filtered  flour  infusion 

— of  flour.  Effect  of  salt  on 
— , Origin  of  term  . 

— , Panary,  Review  of 
- — , Pasteur’s  view  of 


• 457 

. 800 

402,  422 
306,  403 
402 
404 
191 

145 

190 
205 
238 

alco- 
150, 180 
190 
475 

216 
429 

433 
148 

145 

21 1 
427 
214,  433 


332, 


of 


149 
332 

145 

162 

146 
188 

427 

. 149 

. 306 

207 
21 1 

• 145 

422,423 
146 
224 


PAGE 

Flasks,  Alkalinity  of  . . . 439 

— , Measuring 688 

— , Pasteur’s 167 

Flexible  moulder  . , . .651 

Float  for  burette  ....  687 

Flour  analyses.  Results  of  . 352,364 

— , Alum  in 841 

— , Aniline  blue  in  . 

— barm,  sponge  and  dough 

— barms,  Scotch 

• , Thoms’  formulae  . 

— bleaching 

, Action  at  law 

, Ageing  effect  of 

and  improving,  Hamill 

by  electricity  . 

by  nitrogen  peroxide 

, Chemistry  of,  Avery 

, Effects  of  . . 377,  381,  382 

, Estimation  of  nitrogen  per- 
oxide   

, Griess-Ilosvay  test 

, Hamill  on  ...  . 

, Injurious  effects  of,  Ladd  . 

, Local  Government  Board 

reports  on 500 

, Monier- Williams  on  . .500 

patents,  Alsop  . . . 377 

, Andrews  . . . .376 

, Snyder 387 

, Tests  for,  Alway  and  Gortner  385 

, , Shaw  ....  382 

, , Weil  . . . .393 

diazo  compounds  . 398 

,U.S.  Board  of  Food  decision  393 

, Wesener  and  Teller  . 384,  397 

— blending 473 

machinery  ....  629 

Carbon  dioxide  yield  of  . *325 

Changes  in,  resulting  from  fer- 
mentation   475 


840 
407 

249 
249 
375 
393 
381 
501 
377.  382- 

• 376 

• 384 


380 

385 

501 

383 


— , Putrefactive 

187 

— , Chloroform  test  on  . . . 

840 

— , Quick  versus  slow 

430 

— , Colour  of  . . 344,  375,  709,  71 1 

— , Spontaneous 

191 

— , Composition  of  . . . 331,345 

— , Substances  inimical  to 

166 

— , Darnel  in 

837 

— , Summary  of  course  of 

433 

— , Effect  of  age  on  . . 391,  716,  798 

— , Technical  researches  on 

198 

— , germ  on  ...  . 

369 

— , Theory  of  leaven 

462 

— , size  of  starch  grains  on. 

— , Toxic  effect  of  flour  on 

216,  225 

Armstrong 

321 

— , Varieties  of 

150 

— , starch  on,  Snyder 

305 

— , Vienna  system  . 

236 

— , sugar  on  . 

315 

• — , Viscous 

191 

— , Ergot  in 

838 

— , Zymase  theory  of 

148 

— for  confectioners 

852 

Fermentative  properties  of 

various 

— , Fourteen  years  old.  Tests  on  . 

798 

substances — 

— , General  relationship  between 

Albumin 

203 

various  properties  of 

369 

Filtered  flour  infusion  . 

207 

— hoisting 

627 

Flour  .... 

205 

• — improvers 

499 

Pepsin  .... 

203 

— improving,  Hamill 

501 

Potato  and  potato  infusion . 

21 1 

— , Impurities  and  adulterants  of  . 

837 

Separate  constituents  of 

flour 

205 

— , inferior.  Fermentation  of  . 

205 

Starch  .... 

21 1 

— , Maize  in 

838 

Sugar  .... 

203 

— , Mineral  adulterants  and  addi- 

Wort  .... 

204 

tions  to  ...  . 840, 841 

Yeast  mixture 

21 1 

— , Mould  in 

838 

Fibrin 

95 

— , Physical  properties  of 

291 

Filter  ash.  Weight  of 

762 

— , Preservation  of,  by  cold  . 

374 

Filters,  Counterpoised  and  weighed 

763 

— samples.  Changes  during  storage  of  7 1 6 

Flagellum  , , 

. 

. 

183 

— , Standards  of  quality  for  . 

845 

900 


INDEX. 


Flour,  Rice  in  . 

PAGE 

. . 838 

— , Self-raising  . 

. 470 

— sifting  machinery 

• 635 

— , Specific  heat  of  . 

5 

— , Spraying  treatment  of 

. 498 

— , Stability  of  . 

• 705 

— standards,  Jago  and 

Briant’s 

report  on  . 

• • 738 

— , Strength  of  . . . 291,311,327 

— , , Definition  of  . . . 291 

— , , Knowledge  in  1895  • *294 

— , , Present-day  conclusions . 331 

— , , Relation  to  gas-retaining 

power 336 

— Sugar  in  . . . 315.331,335 

— testing  689 

Methods,  Foreign  . 734,740,745 

schedule 744 

with  viscometer  . . .299 

— , Toxic  effect  of,  on  fermentation 


— , Uniformity  in  quality  of  . 

216,  223 
. 846 

— used  in  Scotland  . 

. 421 

— , Water- absorbing  power  of 

• 345 

Flours,  Acidity  of  . . . 

370. 772 

— , Analyses  of  ... 

• 555 

— , Artificial  drying  of 

. 362 

— , Baking  characteristics  of  . 

371,  372 

— collected  in  America  . 

• 735 

— , Composition  of  . 

343.  358 

— , Fatty  matters  of 

• 370 

— , old.  Analysis  of  . 

774,  798 

— produced  during  gradual  reduc- 

tion 

348, 358 

— , Seasonal  variations  in 

• 371 

— , “ Strengthening  ” 

• 374 

— , typical.  Characters  of 
“ Fluff,”  Composition  of. 

• 374 

• 350 

Fluorine 

• 38 

Fondant  sugar  .... 

. 875 

Food,  amount  required  . 

• 527 

Force 

2 

Foreign  wheats.  Composition  of 

. 276 

Formaldehyde,  formalin 

• 51 

Formic  acid  .... 

. 48 

Formula  from  percentage  composi- 

tion.  Calculation  of  . 

19 

Formulae 

.12,  13 

— , Constitutional  . 

13 

— , Empirical  .... 

20 

Fructose  or  laevulose 

86 

Fruit 

. 880 

” Fruit  ” 

. 422 

Fruits,  Dried  .... 

. 881 

— , Preserved  .... 

. 881 

Fungi 

174,  192 

Fusel,  or  Fousel,  oil 

47 

G 

Gas  engines  . . . 613,614,615 


, Directions  for  working  . . 615 

— producers 616 

— ovens 749 

Gases,  Expansion  and  contraction  of  7 
— , Relation  of  pressure  and  volume 

of 7 


Gaseous  diffusion 
— solution  .... 
Gear  wheel  drives 
Gearing  and  power  transmission 

Gelatin 

Gelatinisation  of  starch  . 

Gelose 

Germ,  Composition  of 
— , Effect  of,  on  flour 
— , Structure  of  . . . 

Germination  of  wheat  and  barley 
Glazing 


PAGE 

22 
22 
625 
619 
98 
80,  89 
883 
350 
369 
254,257 

267 
428 


Gliadin  97,103,  297,  300,  303,  306,308,309 
— and  glutenin  estimations,  Cham- 


302, 


berlain 

, Fleurent 

, Guess 

, Guthrie 

— determinations  . . 300, 

— , Estimation  of 

— , by  chalk 

— , — — 'by  starch 

— , on  flour 

— , on  wet  gluten 

, Solution  methods  of 

•,  Trituration  methods  of 

— , one  protein  only  . 

— , Polarimetric  estimation  of 

— ratio.  Relation  to  strength 

flour 

— , Solubility  of,  in  varying  strength 

spirit 

— , Variations  in  composition  of  . 
Globulins  . 

— of  wheat 
Globuloses . 

Glucose,  or  grape  sugar 
— , Analysis  of 


310 

304 

• 303 

• 300 
302,  307 

• 785 

• 787 

. 792 

. 786 

• 787 

• 790 

. 788 

• 308 
306,  309 
of 

340 


• 303 

. 308 

94,  96 

• 103 

• 95 

. 86 
. 876 

. 86,  876 

, Composition  of  876 
. 803,822,876 

• 55 
96,  97 

J05,  1 19,  296,  305,  343 
205 


— , Commercial. 

— , Confectioners’ 

— , Estimation  of 
Glutamine . 

Glutelins  . 

Gluten  . . __ 

— , Action  of  fernientation  on 

— bread  .... 

— cells  .... 

— , Composition  of,  Norton 
— , Conditions  affecting  quantity 

and  physical  character  of 

— determination 

, Arpin  .... 

, Value  of. 

— , Distribution  of,  in  wheat  . 

— , Effect  of  acids  and  salts  on  3 

— extraction  .... 

from  wheat-meal  . 

— , Fermentation  of 
— , Formation  of  . . . 

— , Mechanical  disintegration  of 
— , Relation  between,  and  proteins 
— , Solubility  of,  on  ionisation  hy- 
pothesis   

— testing 

, The  aleurometer  . ... 

— tests  on  commercial  flours 

on  special  flours  and 

wheats 

— , “ Tjue  


472 

254 

309 

341 

696 

305 

343 
370 
- 342 

697 

698 
205 

113 

338 

336 

319 

696 

297 

795 

796 

298 


INDEX. 


ij,' Gluten,  “True/ 

U 


PAGE 

Estimation  of  . 783 

— , Valuation  of  . . . .297 

Glutenin  ....  97,  108,  300 

— , Absorption  of  gliadin  by,  Mat- 

thewson 323 

Glycerin 47.859 

Glycoproteins  ....  96,  98 

Golden  syrup 872 

Gradual  reduction,  Flours  produced 


during 
Grain  life.  Physiology  of 
Gram  .... 


H 


348, 358 
265 
26 


Haematimeter  . 

• 63 

— , Intestinal 

138 

Haemoglobins  . 

96,  98 

Iodine 

38 

Half  sponge 

. 418 

— reaction  with  starch  . 

82 

Hander-up . 

• 653 

Iodoform  ...... 

48 

Handing-up 

• 652 

Ionisation  hypothesis  of  strength 

Hangers 

. 621 

of  flour 

319 

Hansen  on  analysis  of  yeasts  . 

. 176 

Isolation  of  yeast  and  other  organ- 

 yeast  culture  . 

. 168 

isms  

167 

Heat  .... 

2 

Isomerism 

51 

— , Absorption  of 

10 

— , Conduction  of 

8 

— , Convection  of 

8 

J 

— , Elements  of . 

2 

— , Expansion  by 

— measurements 
— , Mechanical  equivalent  of 

— of  combustion 
— , Quantity  of 
— , Radiation  of 
— , Solid  and  flash 
— , Sources  of  . 

— , Specific 
— , Transmission  of 
Hemi-peptones . 

Hetero-albumose 
Hexoses 
High  yeast . 

Higher  fatty  acids,  and  salts  of 
Hilum 
Histones  . 

Hoisting  of  flour 
Holes  in  bread  . 

Homologues,  Definition  of 
Honey 
Hordein 
Hot  water  oven 
Hovis  bread  and  meal 
Howard  flour-testing  system 
Humidity  of  air.  Effect  of,  on  flour 
Hydr-acids  .... 
Hydrazones  or  phenylhydrazones 
Hydrides  of  organic  radicals,  par 

affins  

Hydrochloric  acid  . 

, Use  of,  in  bread-making 

Hydrofluoric  acid 

Hydrogen 

— , Absolute  weight  of 

— peroxide  or  hydroxyl 
— , Sulphuretted 
Hydrolysis 


7 
2 

10 

525 

9 
9 

429 
6 
5 

8 
95 

95 
51.86 

170 

49 
79 

96 
627 
457 

50 
871 

97 

693 
485,495 

740 

695 

16 
55 


— , Details  of 


43 
30 
470 
38 
28 

15 
30 

37 
140,  144 


139,  143 


Hydrolytic  agents  . 
Hydroxides  or  hydrates 
Hyphae 


901 

PAGE 

120 

16 

192 


Iceland  spar 
Improvers,  Bread 
— , Control  of  . 

— , Wheat  and  flour . 

Improving  flour,  Hamill  . 

Indicators  .... 

Insoluble  proteins  of  wheat  108,  1 1 3,  296 
Internal  combustion  engines  . . 613 

Invert  sugar  . . . . 86, 8 1 1 

In  vertase 177 


. 66 

• 509 

• 850 

• 497 

501.  503 

770 


Jam  . 

Jockey  pulleys  . 


K 


Katabolism 

Kempter  kneading  machine  . 

Ketones 

Ketoses 

Kjeldahl’s  method  for  estimation  of 

proteins 

Kneading  machinery 
— machines  with  revolving  blades 
rotating  pans 


882 

624 


264 

642 

51 

52 

780 

637 

638 
640 


Laboratory 680 

Lactic  acid 50 

, Volatility  of  . . . . 438 

— ferments,  Hansen  on  isolation 

of 189 

— fermentation  . . . .188 

Lactose  or  milk  sugar  ...  86 

Laevulose  or  Isevo-glucose  . . 86 

Lard 867 

Leaven  . . . . .461 

— fermentation.  Theory  of  . . 462 

Leavened  bread  . . . .461 

Lecithin 549 

Lecithoproteins  ...  96, 98 

Legumin  ......  97 

Legumelin 96 

Lemon,  Essential  oil  of  . . .884 

— , Oil  of.  Adulteration  of  . .885 

Leucine 54 


902 


INDEX. 


Leucosin 96, 98 

Light,  Polarisation  of  . . . 65 

Lignose,  lignified  cellulose  . . 77 

Lime,  Use  of,  in  bread-making  . 459 

Lintner  on  measurement  of  diastatic 

capacity  . . . . 126,823 

Lintner’s  scale 823 

Liquids,  Solution  of  ...  23 

Litmus 770 

Litre 25 

Loaf,  Shape  of.  Wood  . . . 317 

London  methods  of  bread -making . 412 

Loss  during  fermentation  . . 427 

Low  grade  flours.  Working  with  . 459 

Lubricating  . . . 616, 620, 626 

Lucombe 627 


M 


Machine  bakery  , 

Machine-moulding,  Quality  of 

Machinery 

— , Maintenance  of  . 

Magnesia  mixture 
Magnification  in  diameters 
Maize,  Composition  of 
Malt,  Analysis  of  . . . 

— , Aqueous  extract  of  . 

— ■ bread,  Analysis  of  . . 

— Composition  of  . 

— •,  Mashing  of  . 

— , Mashing  of,  together  with 
malted  grain 

— , Saccharification  of,  during 
mashing 

— extract.  . . . 127,494,510 

Action  of,  on  bruised  starch  129 
, — cane  sugar  . .128 


un- 


612 

652 

597 

626 

759 

61 

270 

820 

127 

487 

140 

H4 

143 

142 


PAGE 

Maltose,  Reducing  power  of  . . 84 

Manchester  methods  of  bread- 
making   413 

Mannite  or  Mannitol  ...  47 

Manufacture  of  compressed  yeasts 

235,247 

starch 80 

Margaric  acid 49 

Margarine 866,  868 

Martin  on  wheat  proteins  . .100 

Mashing  malt  together  with  un- 
malted grain  . . . .14^ 

Matter i 

— , Indestructibility  of  . . . 1 1 

M’Dougall’s  report  on  wheats  . 275 

— baking  tests 733 

Measures  of  weight  and  volume  . 25 

— and  weights,  English  . . . 27 

Mechanical  equivalent  of  heat  . 10 

Metabolism  ....  264,  265 

Metalloids  or  non-metals  . . 12 

Metals 12,  39 

Metamerism 51 

Metaproteins 96 

Methyl 42 

— alcohol 44 

— orange  771 

Methylamine 51 

Methylated  spirits  of  wine  . . 46 

Metre 25 

Metric  system 25 

Micrococcus  prodigiosus  . . .192 

Micrometer 60 

Micromillimetre,  or  m.k.m.  . . 61 

Microscope,  Description  of  . . 57 

— , How  to  use  .....  59 

Microscopic  character  of  starches  . 79 

— counting 63 

— examination  of  starches  . . 88 


, , — flour 

519 

yeast . . . 1 8 1 , 

233,  248 

, — , — , — starch  paste  . 

. 

129 

— objects.  Measurement  of  . 

60 

, -,  — ungelatinised  starch 

128 

• — • sketching  and  tracing 

62,  248 

, Analyses  of  . 512,514,515,516 

Middlings  and  semolinas 

348, 352 

•,  barm  .... 

515 

Midget  testing  mill  . 

. 848 

breads  .... 

487 

Mildew  of  wheat 

. 195 

, Cold  water 

511 

Milk 

. 852 

, Commercial  manufacture. 

— , Condensed  .... 

. 855 

American  .... 

514 

— powders  .... 

. 857 

, , British . 

313 

— standards  .... 

. 853 

, Diastatic  action  of 

491 

— sugar 

86 

, Spent  .... 

511 

Milks,  Valuation  of  . 

• 854 

, Types  of  ... 

510 

Mill-gearing  .... 

. 589 

•,  Whole  .... 

511 

Milling  tests  .... 

. 847 

— • extracts.  Adulterations  of 

828 

Millon’s  reaction  of  proteins  . 

93 

— • — , Analysis  of  . . . 

821 

Mineral  constituents  of  wheat 

68,  73 

, Diastatic  capacity  of  . 

823 

— matters.  Determination  of 

. 757 

, Highly  diastatic  . 

494 

, Nutritive  value  of . 

• 546 

— , Yield  of  ...  . 

247  - 

Mirbane,  Oil  of  ... 

. 88/ 

Maltase  , . . . . 

138 

Mixing  and  kneading  machinery 

• 637 

Malting  system.  Ordinary 

235 

Mixture,  Definition  of 

. 1 1 

, Pneumatic 

236 

— , Notice  of  ...  . 

• 523 

Malto-dextrin  .... 

87,  140 

M.k.m 

61 

— , Hydrolysis  of  . . . 

131 

Modern  baking  machinery  and  ap- 

Maltose 

84,  90 

pliances  .... 

. 612 

— , Estimation  of,  by  Fehling’s 

Moisture  content  of  flour.  Effect 

solution  .... 

84,  804 

of  keeping  on  . 

731.  733 

— , Hydrolysis  of  . . . 

140 

— , Estimation  of  . . . 

691 

— Molecular  constitution  of  . 

130 

— , by  distillation  process 

• 69s 

— , Polarimetric  determination 

of. 

813 

— of  flour.  Effect  of  humidity  on  . 695 

INDEX.  903 


Moisture  of  wheat  . 

PAGE 

. 691 

— , Rapid  determination  of 
— telegraphic  code  . 

695 

845 

Molasses 

872 

Molecular  constitution  of  carbo- 
hydrates   

75 

starch,  dextrin,  and  mal- 
tose   

130 

Molecules 

14 

Molybdic  solution 

759 

Motive  power  in  bakeries 

612 

Motors,  Electric 

618 

— , Explosion  . . . 613,614, 

615 

Mould  in  flour  .... 

838 

Moulding  machines  . 

649 

Moulds 

182 

— and  fungoid  growths  . 

192 

Mucor  mucedo  .... 

192 

Musty  and  mouldy  bread 

194 

Mycelium 

174 

Mycoderma  aceti 

190 

— cerevisicB  .... 

174 

— vini  ..... 

174 

Myosin,  Vegetable  . 

99 

N 

Neroli,  Essential  oil  of 

887 

Nicol’s  prisms  .... 

66 

Nitrates  ..... 

37 

Nitric  acid 

36 

— oxide 

35 

Nitrobenzene  .... 

887 

Nitrogen 

33 

— •,  Oxides  and  acids  of  . 

35 

— peroxide  .... 

36 

— trioxide  .... 

36 

Nitrogenous  organic  compounds 

54 

Nitrous  acid  and  nitrites 

36 

Normal  sodium  hydroxide 

772 

carbonate 

770 

Normal  solutions 

770 

— sulphuric  acid 

771 

— temperature  and  pressure 

8 

Notice  of  mixture 

523 

N.  T.  P 

8 

Nucleoproteins 

96.  97 

Nutrition  and  food 

525 

Nutritive  ratio  .... 

527 

— value.  Mineral 

546 

— values  of  different  varieties 
bread  . . . 525,  528, 

of 

531 

.535 

, Experiments 

on  human  subjects  . 

537 

Nuts 

883 

O 


Oats,  Composition  of  . . . 270 

Objective 58 

Offals,  Composition  of  . . . 349 

Off-hand  doughs  ....  403 

Oilengines.  . . . 613,614,615 

— of  lemon 884 

mirbcine 887 

orange 886 


Oil  of  peppermint  . 

PAGE 

. 884 

wheat 

71 

Oils,  Essential  . 

883 

— , Vegetable  . 

868 

Old  flours.  Analysis  of 

774, 798 

Oleic  acid  .... 

49 

Oleo 

869 

Orange,  Essential  oil  of  . 

886 

— flower  water 

887 

Organic  acids  . 

48 

— chemistry.  Definition  of 

41 

— compounds  . 

41 

— • — , Classification  of 

42 

— • — , Composition  of 

42 

, Nitrogenous  . 

54 

— radicals 

42 

, Hydrides  of.  Paraffins 

43 

Organised  structures 

40 

Oryzenin  .... 

97 

Osazones  or  phenylosazones 

56 

Osborne  and  Voorhees  on 
proteins 

wheat 

100 

Osmose  and  dialysis 

24 

Oven  chimney  . 

586 

— firing  .... 

673 

— fittings  .... 

672 

— furnaces.  Arrangement  of 

— heating,  Perkins’  principle 

670 

659 

— , Hot-water  . 

69 

— light  .... 

672 

— • pyrometers  . 

3 

— types  .... 

662 

— , Vacuum 

693 

Ovens  .... 

596,  658 

— , Automatic  . 

672 

— , Combination 

664 

— , Coverplate  . 

670 

— , Drawplate  . 

662 

— , Electric 

659 

—,  Field  .... 

667 

— , Gas-fired  . 

661 

— , Hot  air  ... 

659 

—,  Hotel  .... 

668 

— , Internally  heated 

658 

— , Mechanically  heated  . 

659 

* — , Portable 

667 

— , — drawplate 

664 

— , Producer  gas  firing  . 

661 

— , Ship  .... 

668 

— , Split  drawplate  . 

664 

— , Steam-pipe  . 

659 

— , Vienna 

668 

Oxides  of  nitrogen  . 

35. 

, 380 

Oxygen  .... 

28 

Oxy-acids  .... 

16 

Ozone  .... 

28 

P 


Palmitic  acid 49 

Panary  fermentation,  or  panifica- 

tion.  Review  of  . . .422 

Papain 98 

Paraffins,  Hydrides  of  organic  radi- 
cals   43 

Parenchymatous  cellulose  . . 77 

Parisian  barm  . . . . .250 


904 


INDEX. 


PAGE 

Pasteur  on  effect  of  oxygen  on  yeast  1 6o 

Pasteur’s  flasks 167 

— fluid 203 

Patent  yeast 241 

Pectin 880 

Pediococcus  cerevisicB  . . . 191 

Peel 881 

Peel  ovens 665 

Pekar’s  colour  test  for  flour  . 379,  7 1 1 

Penicillium  glaucum  . . .192 

Pentosan 53 

Pentose 53 

Peppermint,  Essential  oil  of  . . 884 

Pepsin  and  trypsin  . . . .138 

Peptase 138 

Peptides 96 

Peptones 95.96,98 

Percentage  composition  from  for 

mula.  Calculation  of  . . 18 


795 

796 
96 
91 


PAGE 

Proteins,  Estimations  of,  in  com- 
mercial flours  .... 

— , , in  special  flours  and  wheats 

— , List  of 

— , Nomenclature  of  . . . 

— of  wheat  . . . 99,111,117 

, albumins  ....  102 

, Distribution  of 

, Earlier  researches  on 

— , globulin  .... 

, Osborne  and  Voorhees  on 

, soluble  in  water 

• , Summary 

— of  oat  kernel  .... 

— , Precipitation  of  . 

— , Reactions  of  . . .92, 

— , Salting  out  of  (precipitation)  93 


— , Separation  of 
— , Simple 


117 

99 

lOI 

100 

100 

1 16 

117 
93 

118 

. 97 


93.  97 


Perfumes,  Confectioners’ . 

. 890 

■ — , Soluble,  Estimation  of 

Peroxide  of  hydrogen 

30 

103,  1 18,  294,  785 

— of  nitrogen  .... 

35 

— , Solubility  of  . . . 

. 

92 

Phenolphthalein 

• 771 

— , Summary  of  properties 

and 

Phenylhydrazine 

• 55 

composition  of 

116 

Phenylhydrazone  or  hydrazones 

• 55 

— , True,  Estimation  of  . 

784 

Phenylosazones  or  osazones  . 

• 56 

— , Vegetable  .... 

95 

Phosphate  powders  . 

. 467 

Proteolytic  enzyme  of  seeds  . 

139 

Phosphates,  Manufacture  of  . 

. 499 

— enzymes.  Detection  of 

326 

— , Nutritive  value  of 

• 547 

— ferments  of  wheat.  Ford 

and 

Phosphoproteins 

96,  98 

Guthrie  .... 

324 

Phosphoric  acid 

• 39 

Proteoses  . . .94,  96,  98,  102, 

. 302 

, Determination  of  . 

. 759 

— of  wheat  .... 

102 

Phosphorus,  phosphoric  acid,  and 

Proto-albumose 

95 

phosphates 

39 

Protoplasm  .... 

264 

Physical  structure  of  wheat  grain  . 254 

Prover,  Automatic  . 

653 

Physiology  of  grain  life  . 

. 264 

— , Final 

658 

Pile  of  bread  .... 

292,  832 

Ptyalin  and  amylopsin  . 

134 

Pipettes  

. 688 

Pulleys 

621 

Plans,  Typical,  for  bakeries  . 

• 597 

— , Jockey  .... 

624 

Pneumatic  maltings . 

. 236 

Putrefaction  .... 

118 

Polarimeter,  The 

67,  807 

— , Conditions  inimical  to 

187 

Polarimetric  estimations  306,  309,  806 

— , Products  of  ... 

188 

Polarisation  of  light. 

. 65 

Putrefactive  fermentation 

187 

Polariser 

. 67 

, Action  of  oxygen  on 

187 

Polymerism 51 

Polypeptides 92 

Potato  ferment  . . . .422 

Potatoes,  Action  of,  on  fermentation  213 

Potash,  Determination  of  . . 762 

Potassium  and  its  compounds  . 40 

Power  transmission  . . . .619 

Precipitates,  Washing  and  ignition 

of 761 

Producer  gas  . . . 613,616,661 

Prolamins 96,  97 

Proof  spirit 45 

Propyl  alcohol 46 

Propylamine 51 

Protamines 96 


Proteans  . 

96,  98 

Protease,  Detection  of. 

in  flour  . 326 

Proteins  . 

91,107,300 

— , Amount  of  various,  contained  in 

wheat 

1 1 1 

— , Animal 

94 

— , Classification  of 

.94,96 

— , Composition  of  • . 

91 

— , Decomposition  of 

. 117 

— , Estimation  of 

. 780  1 

Pyrometers 


Quantities,  Calculation  of  . . 20 
Quantity  of  heat  ....  4 

Quanti valence  or  atomicity  . . 17 
Quarter  sponge  . . . -419 


Radiation  of  heat  ....  9 

Radicals,  Compound  . . . 17 

— , Organic 42 

Radium 12 

Raffinose 87 

Rancidity 867 

Raoult  on  molecular  weights  . , 75 

Raw  grain  diastases  . . .134 

Red  spots  in  bread  . . . .193 

Reducing  power  of  maltose  . . 84 

Registers  for  bakeries  . . . 679 


INDEX. 


905 


PAGE 


Remedies  for  sour  bread  . . .450 

Replacement  tests  ....  847 

Reychler’s  “ Artificial  ” diastase  . 135 

Rice,  Composition  of  . . . 270 

Richardson’s  baking  tests  . . 734 

Right-angle  drive  . . . .625 

Ring  lubrication  ....  620 

Ritthausen  on  wheat  proteins  . 99 

Rochelle  salt 50 

Roller  bearings  ....  620 


— milling  products,  Composition  of 

345.  346 

, Richardson’s  analyses  of 


Rope  driving 

351.  354 
. 625 

Ropes,  Wire  .... 

. 628 

Ropiness  in  beer  and  bread  . 

. 191 

bread,  Watkins 

• 451 

Rotary  mixers  .... 

• 637 

Rotatory  power.  Specific 

. 807 

Rousing,  Action  of,  on  yeast  . 

161 

Routine  mill  tests 

844.  846 

Rye  bread  .... 

. 472 

— , Composition  of  . 

270 

s 


Saccharification  . . . .120 

— of  malt  during  mashing  . .142 

Saccharomyces  cerevisics  . . .170 

, Life  history  of  . . .156 

, Classification  of  . . .170 

— ellipsoideus 174 

— minor 173 

— my  coderma  or  my  coderma  vini  . 1 74 

— pastorianus 174 

Sack  hoist 627 

Salt,  Definition  of  . . . . 16 

— , Common,  Action  of,  in  bread- 
making . . . . — . 400 

— , — , , on  fermentation  . 2 1 1 


— , Use  of 427 

Samples,  Collection  and  dispatch  of  844 
Sanitary  aspects  of  bakehouses  583,  586 

baking  machinery  . . 612 

Schizomycetes 182 

— , Spore  formation  of  . . . 185 

Scotch  flour  barms  ....  249 

— methods  of  bread -making  . 414,  418 

Section  cutting  and  mounting  . 257 

Self-raising  flour  ....  470 

Semolinas  and  middlings  . . 348 

Setters 656 

Setting  bread 662 

Shafting 619 

— , Power  absorbed  by  . . . 624 

Shaking  apparatus  ....  794 

Sharps,  Composition  of  . . . 349 

" Sheen  ” 714 

Sifting  machine  for  flour  . >635 

Silicic  acid 38 

Silicon,  silica,  and  the  silicates  . 38 

Simple  proteins  ....  96 

Smoke  nuisance  . . . .590 

Smut 195 

Soaps  and  Fats  ....  49 

Sodium  bicarbonate  . . . 464 


Sodium  chloride 

PAGE 

400 

— compounds  .... 

40 

Solid  and  flash  heats 

. 429 

Solids,  Solution  of  . 

23 

Soluble  ferments 

121 

— proteins  .... 

. 294 

of  wheat  .... 

100 

— extract  .... 

296,  768 

— starch 

81 

, Estimation  of 

. 818 

Solution 

22 

— , Gaseous  .... 

22 

— of  liquids  .... 

• 23 

— of  solids  .... 

23 

Sour  bread 

• 433 

, Briant’s  researches  on  . 

• 434 

, Researches  on 

• 437 

, Remedies  for  . 

• 450 

, Separation  and  identification 

of  acids  of  . . . . 438,  774 

, Summary  of  views  on  . . 449 

Souring  of  bread.  Ammonia  pro- 
duced during  ....  447 

, Effect  of  high  tempera- 
tures on 447 


Sourness,  Relation  of,  to  acidity  434,  447 


attenua- 


Soxhlett’s  extraction  apparatus 
Special  breads  and  bread-making 
processes  . 

Specific  heat 

— gravity  of  worts  and 

tion  . 

— rotatory  power  . 

Spirits  of  wine,  alcohol 

, Methylated 

Sponging  and  doughing 

by  machinery 

Sponge 

— and  dough  . 

, Management  of 

Sponge-making  machines 
Spontaneous  fermentation 

Sporangia 

Spores 

Spraying  treatment  of  wheaten 

stock  and  flour 
Stability  of  flour  tests 
“ Standard  ” bread  .... 

, Snyder  on  ...  . 

Starch 

— , Action  of  caustic  alkalies  and 
zinc  chloride  on 
— , Action  of  diastase  on 
— , Action  of  iodine  on 


763 

483 

5 


. 247 

. 807 

44 
. 46 

. 425 

. 637 

. 402 

404.  425 

. 426 

. 644 
. 191 

. 192 

. 185 


498 

705 

553 
561 
77.  294 


82 

127 

82 


— , Admixture  of,  with  yeast  . . 239 

— , bruised,  Action  of  malt  extract 

on 129 

— cellulose 77 

— , Estimation  of  . . . 814,816 

— , Fermentation  of  ...  206 

— , Gelatinisation  of  . . 80,  89 

— , — , Temperature  of  . . , 81 

— grains.  Effect  of  size  of,  on  flour, 

Armstrong 321 

— , Hydrolysis  of  . . . 139,143 

— in  yeast  ....  239,  840 

— , Molecular  constitution  of  . . 130 

— , Occurrence  of  . . . . 77 

— of  wheat  ....  77,  78,  79 


906 


INDEX. 


PAGE 

PAGE 

Starch  paste,  Action,  of  malt  extract 

Tcxalbumins  .... 

224 

on  . 

129 

Transmission  of  heat 

8 

— , Preparation  and  manufacture  of 

80 

Treacle  ..... 

872 

— , Properties  of,  in  solution 

82 

Trimethylamine 

SI 

— , Saccharification  of  . . . 

120 

True  gluten  .... 

296 

— , Solubility  of  ...  . 

80 

, Estimation  of 

783 

— , Soluble 

81 

— proteins.  Estimation  of 

784 

— , — , Estimation  of  . . . 

818 

Trypsin 

138 

— solution.  Properties  of 

82 

Tuberin 

97 

, Reactions  of  . . . 82, 89 

Turog  bread  .... 

487.  493 

— sugar,  glucose  .... 

876 

Tyrosine 

54 

— , ungelatinised.  Action  of  malt 

extract  on 

128 

Starches,  Microscopic  character  of 

1 1 

various 

77 

U 

— , — examination  of  . . 88.^21 

Steam  oven 

659 

Underground  bakehouses 

. 

582 

Stearic  acid 

49 

Unsound,  or  very  low  grade  flours. 

Storage  of  flour. 

629 

Working  with  . , 

459 

Strength  of  flour  . 29 1 , 294,  3 1 1 , 3 1 9 

Ustilago  segetum 

195 

yeast  

198 

“ Strengthening  ” flours 

374 

Striking  gear  ..... 

624 

V 

Substitution,  or  compound,  ammonias  54 

Succinic  acid 

50 

Vacuum  oven  .... 

693 

Sucrose,  cane  sugar  . . . 85, 871 

Vanilla  and  vanillin . 

889 

Sugar  and  dextrin  of  wheat  . 

294 

Vanillin,  Synthetic  . 

890 

— boiling 

874 

Veda  bread.  Analysis  of  . 

495 

— , cane,  inverted,  Polarimetric 

Vegetable  albumin  . 

96 

behaviour  of  ...  . 

811 

— myosin 

97.  99 

— , Cutting  the  grain  of  . 

875 

Veltex 

869 

— , Fondant 

875 

Vernier,  Description  of  . 

810 

— , Polarimetric  estimation  of 

811 

Vibrio  suhtilis  .... 

185 

Sugars 294,871 

Vienna  bread  .... 

461 

— , Commercial,  Composition  of  . 

872 

— ovens 

668 

— , Estimation  of,  by  Fehling's 

Viennara  kneading  machine  . 

641 

solution 

800 

Virgin,  barm  .... 

249 

— , — — , by  polarimeter 

811 

Viscometer  .... 

702 

Sulphates 

37 

— , Mode  of  testing  with  . 

703 

Sulphites  

37 

Viscometric  gluten  valuations 

298 

Sulphur 

37 

Viscous  fermentation 

191 

— dioxide 

37 

Vitellin 

94.  97 

Sulphuretted  hydrogen  . 

37 

“ Volatile,”  ammonium  carbonate 

464 

Sulphuric  acid  and  sulphates  . 

37 

Voller  on  wheats 

282 

Sulphurous  acid  and  sulphites 

37 

Voller’s  dictionary  of  wheat  . 

284 

Symbols  and  formulae 

12 

Volume,  Laws  of  chemical  com- 

Systeme-Schweitzer  of  bread-mak- 

bination by  . . . 

15 

ing  

483 

— , Measures  of  . 

25 

T 

Tailings,  Composition  of  . 

345.  351 

Tannin,  Effect  of,  on  bacteria 

. 190 

Tartar,  Cream  of  . . . 

. 464 

Tartaric  acid  .... 

50.  464 

Tartrate  powders 

. 467 

Telegraphic  codes 

. 845 

Temperature  .... 

. 2 

— , Absolute  zero  of 

7 

— , Automatic  regulator  . 

. 227 

— , Effect  of,  on  fermentation 

. 214 

Test  mills 

. 691 

Testing  with  viscometer  . 

702 

Thermometer  .... 

3 

Thermometric  scales 

3 

Tintometer  .... 

. 709 

Total  proteins.  Estimation  of 

. 780 

Tourmaline  .... 

66 

W 


Walsh  and  Waldo  on  effect  of  bak- 


ing  on  bacterial  life  . 

. 450 

Wash-bottle  .... 

. 761 

Water 

29,  400 

— bath 

227,  769 

— , Corrosive  action  of  . 

. 637 

— ■,  Estimation  of  . • • 

. 691 

— for  washing  wheat 

. 361 

— free  from  carbon  dioxide  . 

. 772 

— heating  . . 

. 675 

— in  furnace  ashpit 

. 674 

— Measuring  and  attemperating 

:or 

tempering  ...» 

. 636 

— of  wheat  .... 

297,  691 

— , Softening  of  . • • 

. 400 

— , Solvent  power  of 

29 

INDEX. 


907 


PAGE 

Water-absorbing  power  of  flour  345,  699 
, Effect  of  temperature 


on 706 

Water-absorption  burette  . . 700 

Watkins  on  ropy  bread  . • -452 
Weighed  filters  ....  763 

Weighing  of  bread  . . • 562, 648 

— , Operation  of  . . • .685 

Weight,  Measures  of  . . • 25 

Weights,  Analytic  . . • .683 

— and  measures,  English  . . 27 

Weyl  and  BischofE  on  wheat  pro- 
teins   99 

Wheat,  Agricultural  improvement 

of  . . . • • -497 

— ash.  Composition  of  . • 69,  270 

— blending  . . • • • 473 

— , Chemical  changes  during  ripening 

of 282,  290 

— , Chemical  composition  of  . . 207 

— , Cleaning  machine  for  testing  . 849 

— ’ Commercial  assay  of  . . .307 

— , Constituents  of  . . 68,73,270 

— , Damping  of . . . • • 360 

— , Distribution  of  gluten  in  . . 370 

— , Durum,  Norton  ....  280 

— , Fatty  matters  of  . • 70,  294 

— , Foreign  matters  in  . . . 690 

— , Germination  of  . . • • 267 

— grain.  Construction  of  . 68,  254 

, Crease  of  . . • .256 

, Functions  of  . . . 254,559 

— Grinding  of  samples  . . . 690 

— , Insoluble  proteins  of,  gluten 

105,  1 19,  296,  305,  343 
— , Microscopic  examination  of  . 258 
— , Mineral  constituents  of  . .68 

— mixtures,  Voller  . . . .282 

— oil,  de  Negri,  Frankforter,  and 

Harding 7 1 

— , Organic  constituents  of  . • 7^ 

— products.  Nutritive  ratio  of  . 527 

— , Protein  of,  soluble  in  dilute 

alcohol,  gliadin  . . • 310 

A— proteins.  Properties  of,  Cham- 
berlain   3^0 

— replacement  calculations  . . 849 

tests 847 

— • section  cutting  . . . .257 

— , Soluble  proteins  of  . • .295 

— testing 689 

— , — Commercial,  Snyder  . . 307 

— , Treatment  of,  by  moist  heat  . 497 

— , , by  water-soluble  phos- 
phates   497 

— washing,  Water  for  . . . 361 

— . Water-soluble  phosphates  of. 

Wood 323 

— , Weight  per  bushel  . . • 689 

— , — of  100  grains  . . • 689 

Wheaten  stock,  Spraying  treatment 

of 498 

Wheats,  American  . . • .728 

— , Analyses  of  . ...  272 

— and  flours,  Artificial  drying  of  . 362 

— , Artificial  drying  of  . . • 361 

— , Composition  of,  Fleurent  . . 280 

— , Damping  of  . . • • 369 

— , English  and  Scotch  . . . 273 


\ 


Wheats,  Foreign  . . . . 

— , McDougall’s  tests  on. 

— , Replacing  mixtures  of 
White  bread,  analysis  of  . 

Whole  meal  bread  .... 

— , Analysis  of  . • • 

Wild  yeasts 

Wire  ropes 

Wood  on  strength  of  flour 
Worts,  Preparation  of  . • • 

— , Specific  gravity  of,  and  attenua- 
tion   


PAGE 

276 

279 

282 

495 

470 

495 

179 

628 

311 

236 

247 


X 

Xanthoproteic  reaction  of  proteins  93 

Y 


Yeast  . . • • *150 

— , Admixture  of  starch  with  . . 239 

— an  article  of  food . . • • 241 

— and  other  organisms.  Isolation 

of 167 

— as  an  organism  . . • -153 

— , Ascospores  of  . . • 166,176 

— , Bakers'  home-made  . . .241 

— , Behaviour  of  free  oxygen  to  . 160 

— , Botanic  position  of  . . • i54 

— , Bottom-fermentation  species  . 179 

— , Brewers’ 233 

— brewing,  Suggestions  on  . • 246 

— , Budding  of 1 5 5 

— cells,  Nature  of  . . • *155 

— , Chemical  composition  of  . • 152 
— , — reactions  of  . . • *155 

— compressed,  Characteristics  of  239 
— , — , Manufacture  of  . . *235 

— counting ^3 

— , cultivated.  Varieties  of  . • I79 

— culture  and  isolation  . . .167 

— , Distillers’ ^72 

— , — , Manufacture  of  . . • 235 

— , Efiect  of  rousing  on  . . • 161 

— , Endogenous  division  of  . .166 

— growth,  Influence  of  tempera- 

ture on  . . • . . I 58 

— , High  . . *.*..•  • 

— ^ — and  low,  Convertibility  of  . 172 

’ , Distinctions  between  1 70 

— ’ Insufficiency  of  either  sugar  or 
nitrogenous  matter  only  for 
nutriment  of  . . • .160 

— , Isolation  of  . • • .167 

— , Keeping  properties  of  . 213,231^ 

— , Life  History  of  . • • .156 

— , Low  or  sedimentary  . . .170 

— , Mal-nutrition  of  . • .165 

— , Manufacture  of  . . • .233 

, bakers’  “ patent  ” or 

home-made  malt  and  hop  • 241 

— ^ brewers’  . . • • 233 

— ^ compressed  . • .235 

’ Scotch  flour  barm  . . 249 

’ Methods  of  isolation  of,  and 

other  organisms  . . .167 


908 


INDEX. 


PAGE 


Yeast,  Microscopic  study  of  1 8 1,  233,  248 
— , Mineral  matters  necessary  for 

growth  of 

— mixture  ....  203 

— , Multiplication  of,  by  endogenous 

division 

— , Nature  of  cells  of  . . . 

— , Necessity  of  saccharine  matter  for 
— , Nitrogenous  nutriment  of. 

“ Patent  ” 

— , Formula  for  .... 

— , Suggestions  on  . . . 

Purification  of  . . . 167,  189 

Sporular  reproduction  of  . .166 

Starch  in 840 

Strength  of ig8 

Substances  requisite  for  nutri- 
ment of  158 


160 

230 

166 

155 

158 

159 

241 

246 

246 


Yeast,  Technical  researches  on 
— testing  ..... 

Apparatus 

— , Top-fermentation  species  of 
— , variety  and  quantity  used 
Yeasts,  Classification  of  . 

— , Detection  of  wild 
— , Hansen  on  analysis  of 
Young  on  alum 


PAGE 

. 198 

198,  229 

199,  227 

. 180 

155.426 
. 170 

• 179 
. 176 

. 842 


z 

Zein 

Zero,  Absolute 
Zoogloea  . . . . 

Zymase  . . . . 

— theory  of  fermentation 


97 

7 

183 

139 

148 


L & A.  Harris,  Printers,  94,  Leadenliall  Str^,  E.C, 


